Petfood Palatability: Why Replacing Meat Is More Than Replacing Protein

The Friday Conversation · No. 3

Meat Is More Than Protein

Perhaps meat was never just an ingredient. It is a biological language that every alternative protein must eventually learn to speak.

Dr. rer. nat. habil. Dr. Seronei Chelulei Cheison

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Stand near a barbecue with your eyes closed and you can name what is cooking. Chicken smells like chicken. Lamb smells like lamb. Salmon announces itself across a garden, and beef is unmistakable long before it reaches the plate. Nobody finds this remarkable, because everybody can do it. It is one of those competences so ordinary that we never stop to ask how it works.

So ask it. Why does lamb smell like lamb and not like beef?

The comfortable answer is that they are different animals, which is true and explains nothing. Here is the answer that should unsettle anyone whose job is to rebuild meat from something that was never an animal at all: the difference you are smelling is almost entirely not in the protein. Strip a piece of chicken and a piece of beef down to their lean muscle, cook them bare, and they converge. The heat of cooking on lean tissue produces a meaty aroma that is remarkably species-neutral, the generic smell of cooked flesh, and a blindfolded taster would struggle to tell them apart. What makes chicken smell like chicken lives somewhere else.

It lives in the fat. And not the fat you can see and trim, but the fat woven invisibly into the cell membranes: the phospholipids. Remove the phospholipids from beef and its flavour changes markedly; leave the visible marbling and remove nothing else, and far less is lost. The species signature is a membrane phenomenon. The identity of meat resides less in its muscle proteins than in the chemistry of the lipids surrounding them. Lamb carries its identity in branched-chain fatty acids that beef does not use for flavour at all. Pork can carry a note that is, quite literally, a steroid dissolved in fat: boar taint, the reason most male pigs are castrated, is androstenone lodged in the adipose tissue. Chicken loses its chicken-ness the moment you wash the polar compounds out of its adipose tissue. And none of it speaks until fire arrives: raw meat is weakly flavoured, faintly metallic, faintly of blood, a reservoir of precursors waiting for heat to convert them. A substantial proportion of a cooked meat's characteristic aroma arises from lipid oxidation products and their interactions during heating, rather than from the muscle proteins themselves.

The lean is nearly the same across species. The signature was always in the fat.

I open here, at the grill, for the fastest way into the thing this whole conversation turns on. In the second of these Friday conversations I wrote about a single molecule, the one a cat reads off a fresh wound before it has taken a bite. That was the smell of the kill. This is the smell of the fire. Meat speaks in more than one aroma, one from the wound and one from the flame, and in both of them the protein is silent. Which raises the question the alternative-protein transition has mostly declined to ask out loud: if the thing that makes meat taste of anything at all was never the protein, what exactly are we matching when we match the protein?

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WHAT WE HAVE REPLACED, AND WHAT WE HAVE NOT

Let me grant the strong version first. It is true, and the argument does not work without it.

What the alternative-protein industry has largely succeeded in replacing is nutrition. We now know how to formulate diets that deliver complete amino acid profiles, adequate digestibility and, with appropriate supplementation, the vitamins and micronutrients an obligate carnivore requires. That is no small achievement. It represents decades of careful nutritional science, and I have spent enough of my own life on protein hydrolysis to refuse to wave it away. The lysine in a pea is the same lysine as the lysine in a muscle; it is a small, defined molecule and it does not carry a passport. On the nutrient certificate, the substitution is honest and complete.

What remains much less certain is everything beyond nutrition.

We are making progress in reproducing the broad savoury character of meat through hydrolysed proteins, fermentation products, yeast extracts and carefully designed flavour systems. Yet recreating the aroma of meat is not the same as recreating the identity of meat. A cooked chicken, a grilled lamb chop and a roasted beef steak all announce themselves long before they are tasted, each carrying a distinctive chemical signature that evolution has written into their lipids and that cooking merely reveals. We understand fragments of that language. We are still far from speaking it fluently.

A legume may provide the vocabulary of nutrition. Meat provides the grammar of recognition.

Harder still is the question of species recognition. We know remarkably little about how a cat weighs one prey species against another, or how many cues must be present, and in what combination, before the brain concludes simply: this is food. In the last of these conversations we met one such cue, a blood-borne signal shared across the whole predatory lineage. But that signal says kill, not chicken. The cues that carry species identity, and the number of them a diet must satisfy, remain largely unmapped. The science is moving. The map is still mostly blank.

Beyond recognition lies an even larger uncertainty. A bowl is emptied not because a formulation is nutritionally complete, but because an animal chooses to return to it, day after day. That decision emerges from a conversation between aroma, taste, texture and the physiological consequences of eating. Preference is learned, reinforced, and sometimes abandoned. We understand parts of that process. We do not yet understand the whole.

Seen in this light, the challenge facing alternative proteins is changing. It is no longer simply to replace the nutrients found in meat. Increasingly, it is to reproduce the biological functions that meat performs. Nutrition may be the first milestone. It is unlikely to be the last. The future belongs not to formulations that merely analyse like meat, but to those that are recognised, accepted and remembered as food by the animal standing at the bowl.

And to see how far that reaches, you have to stop treating meat as a thing with a fixed composition, and start watching what it does when it is left alone.

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Movement I

MEAT THAT WRITES ITSELF

Here is the fact that ought to change how a formulator looks at a data sheet, and almost never does. A cut of meat is not finished when the animal dies. It is barely begun.

In the hours and days after death, the tissue sets about digesting itself. No one adds an enzyme; the enzymes were always there, folded away inside the living cell, kept apart from the structures they would otherwise destroy. Death removes the partition. As the muscle runs out of oxygen and turns acidic, drifting down toward a pH near 5.5, the little membrane-bound compartments called lysosomes, the cell's own recycling bins, begin to break open. Out spill the cathepsins, enzymes that are most active in exactly the acid conditions that dying muscle creates. A second family, the calpains, goes to work on the structural proteins and loosens the meat toward tenderness. The cathepsins and the peptidases that follow them do something subtler and, for our purposes, more important: they carve the long proteins into short peptides, and the short peptides into free amino acids.

This is where much of meat's flavour is actually made. Aging is not storage. It is a slow, self-directed hydrolysis, the tissue quietly cleaving its own proteins into the small, taste-active fragments a carnivore is tuned to. Amino acids that are barely present in fresh muscle, tyrosine, phenylalanine, threonine, tryptophan, rise into detectability as the enzymes run. Some of them read as sweet, some as bitter, and the acidic and sulphur-bearing ones, glutamate and aspartate, cysteine and methionine, carry the deep savour we call umami. The meat that a cat would choose is, in a real sense, meat that has been cooking itself without heat.

Aging is not storage. It is the meat quietly cleaving its own proteins into the language of savour.

Now set that beside a specification. When we match the amino acid profile of muscle, we are matching a photograph of a moving thing. The certificate records what the tissue contained at the instant it was sampled, as though composition were the point. But the carnivore did not evolve to eat a composition. It evolved to eat a process, a tissue whose free amino acids and peptides and nucleotides are still being generated on their own clock, arriving in a sequence and a proportion that the animal's chemistry learned to read across millions of years of eating exactly this.

A legume hands you a number, fixed and honest, printed on a page. Muscle hands you an engine that is still running. You can match the number precisely and never build the engine, because the engine was never in the protein content. It was in the enzymes that came free with the animal, the ones that keep working after the animal is gone.

A legume gives you a number on a certificate. Muscle gives you an engine that is still running.

And the engine does not stop at flavour. The same self-digestion that fills fresh meat with savour keeps going, and where it goes next is the second half of this story, because the clock that ripens meat is the same clock that will eventually spoil it. Before we follow it there, though, we should look at what the animal is reading while the meat is still at its best, the signal that sits at the very peak of freshness and begins, quietly, to fade from the first hour onward.

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Movement II

THE CLOCK THE TONGUE CAN READ

There is a second clock running alongside the first, and where the enzymes of self-digestion were slow, this one is fast and almost violent in its opening moments. It concerns the nucleotides, and it is the taste-side companion to the smell-side signal I wrote about last time.

At the instant of death, the muscle is still charged with adenosine triphosphate, ATP, the molecule that powered it in life. With the animal gone and the oxygen with it, that ATP begins to fall apart along a fixed staircase: to ADP, to AMP, and then, within the first day or two, to a compound called inosine monophosphate, IMP. And IMP is not a waste product. It is one of the most powerful savoury molecules in all of food, the nucleotide that carries umami, the very compound the tongue of an obligate carnivore is built to detect. In the first hours after death the meat is quietly filling with the taste of savour. This is the peak. This is freshness at its most delicious, and it is why a signal on the taste side and a signal on the smell side both point, in a fresh kill, to the same conclusion.

But the staircase does not stop at IMP. It keeps descending, only more slowly, because the enzyme that breaks IMP down is the rate-limiting step, and so IMP lingers at its peak for a while, a plateau of deliciousness, before it gives way. When it gives way it becomes inosine, and then hypoxanthine, and hypoxanthine is bitter. The savour fades and a faint bitterness rises in its place. Long before any bacterium has done its work, long before the meat has begun to rot in any sense a nose would recognise, the taste has already started to tell the animal that the best moment has passed.

IMP is the taste of freshness at its peak. Hypoxanthine is the taste of that peak already passing.

This is the taste-side clock, and the tools of fish science measure it directly. The freshness of fish is graded by a number, the K-value, that is simply the ratio of the spent compounds, inosine and hypoxanthine, to the whole family of ATP breakdown products. A low K-value is a fresh fish; a high one is a fish whose clock has run down. A carnivore does not carry a laboratory, but it carries the same reading in its mouth. The E2D of the last conversation was freshness announced at the very first instant, ab initio, off the wound. The nucleotide clock is freshness measured across the hours that follow, the savour rising to a peak and then, molecule by molecule, beginning to leave. Between them, smell and taste, the animal has a remarkably precise clock on how long ago something died.

And this is where one ingredient proves the entire argument of this essay, more plainly than any reasoning could.

Consider liver. Ask anyone who has fed cats and dogs which single ingredient they find hardest to resist, and liver will be near the top of every list. Cats can be so taken with it that they will overeat it against their own interest. On a protein specification, liver is unremarkable, roughly comparable to muscle, sometimes lower. If protein were the thing an animal was chasing, liver would be ordinary. It is not ordinary. It is close to irresistible, and the reason is precisely the vocabulary this essay has been assembling.

Liver is not muscle at rest. It is the body's most metabolically active organ, a chemical factory that never idles in life, and it is therefore dense in exactly the compounds a carnivore is tuned to read: nucleotides in abundance, free amino acids and short peptides, the blood that carries the heme and its metallic note, and the fat that carries so much else. Everything the tongue and nose of a carnivore evolved to prize is concentrated in that one organ, not because it holds more protein, but because organ function itself, the ceaseless traffic of a living liver, leaves its signature in the tissue. The palatability of liver is metabolism made edible.

Liver is not more protein than muscle. It is more of everything the protein was never carrying.

There is a quiet lesson folded inside this for anyone tempted to think the answer is simply to add the missing molecules back. Some of what makes the organ precious does not survive the factory. The heat of processing degrades the very taurine and the B vitamins that made the raw organ so complete for a cat, which is why they must be added back as supplements at all. We are already, without quite admitting it, conceding the point: the raw tissue delivered something that our processing removes and then reconstructs in part. Nutrition we can rebuild. Whether we have rebuilt the whole of what the animal was reading is a different and far less settled question.

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Movement III

WORDS ONLY FIRE CAN SAY

Everything so far has been about what the raw tissue already holds, or makes for itself: the fat woven into the membranes, the peptides carved out by the cell's own enzymes, the nucleotides rising and falling on their clock. But a large part of meat's language does not exist in the raw material at all. It has to be written, and the pen is heat.

Return to the barbecue we started at. The raw chop on the counter is faint, a little metallic, faintly of blood, and almost nothing like the thing that will fill the garden twenty minutes later. What happens in between is chemistry of real complexity, and it has a name. When the amino acids and the reducing sugars in the meat are brought together at temperature, they enter the Maillard reaction, a cascade of hundreds of steps that generates hundreds of new molecules that were simply not present before. Alongside it runs Strecker degradation, breaking amino acids into their own aromatic fragments, and alongside that the breakdown of the lipids, throwing off volatile pieces of the fat. These are not small effects. The characteristic flavour of cooked meat is very largely a creation of these thermal reactions. The roast, the sear, the brown crust: this is a vocabulary spoken only by fire, and the raw tissue is merely the reservoir of words waiting to be said.

Here, at last, is a part of the language where the alternative-protein project is on strong ground, and I want to say so plainly. The Maillard reaction does not, in principle, care where its amino acids and sugars came from. Give it the free amino acids of a fermented biomass and the reducing sugars of a plant, hold them at the right temperature, and it will brown and roast and generate savour on a meat-free substrate as readily as on a muscle. Much of the industry's real success in savoury flavour lives exactly here, in the deliberate use of thermal reactions and the hydrolysates that feed them. If any part of meat's language can be spoken fluently by a plant or a ferment, it is this one.

The Maillard reaction does not ask where its ingredients were born. This is the part of the language a plant can learn to speak.

But notice the boundary, because it is precise, and it takes us straight back to the grill. The Maillard reaction supplies the meaty. It does not, by itself, supply the chicken, or the lamb, or the beef. The generic roasted savour is shared; the species identity rides on the lipid substrate underneath it, on those branched-chain fatty acids and species-specific phospholipids that the heat is acting upon. Cook two different meats and the Maillard chemistry is broadly the same in both; what differs is the fat it has to work with, and the fat is where the animal's name is written. So heat can give a fungal kibble the word for cooked. Whether it can give it the word for a particular prey is a harder question, and it returns us, every time, to the fat.

There is a second, quieter point in this for the formulator, and it connects the two halves of the essay. Some of the most meaty of all the thermal compounds are built, in part, from the very nucleotides we were just discussing. The IMP that carries umami on the tongue is also a precursor that heat can convert into some of the most potent roasted, meaty aromas known. The freshness clock and the fire are not separate systems. The molecule that signals a fresh kill to the taste is the same molecule that, under heat, helps write the smell of the roast. Meat's vocabulary is not a list of independent words. It is a web, in which the same molecule can mean one thing to the raw tongue and another thing entirely once the fire has spoken it.

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Movement IV

CONTROLLED SPOILAGE

Follow the clock past its best moment and it does not simply stop. The same self-digestion that filled the fresh meat with savour keeps running, and now a second cast of characters arrives: the bacteria. What they do next is, on the surface, the story of rot. Read more closely, it is one of the most interesting things in this whole essay, for it is also the story of some of the most prized foods we make.

When microbes settle into meat, they set about the free amino acids that self-digestion so helpfully produced, and they strip the acid group from them. This is decarboxylation, and its products are the biogenic amines, each one traceable to the amino acid it came from: histidine becomes histamine, tyrosine becomes tyramine, lysine becomes cadaverine, ornithine becomes putrescine. The names alone tell you which way this is heading. Cadaverine and putrescine are the smell of decay, and their rise is a reliable index that decomposition has begun.

But the story is not as simple as good versus spoiled, and this is the part worth slowing down for. Some of these amines are genuinely aversive, even dangerous: histamine at high levels is the cause of scombroid poisoning, and tyramine and phenylethylamine can push blood pressure and trigger headaches. Some are close to neutral, present at low levels in perfectly healthy tissue as part of the ordinary chemistry of living cells. And some, in the right food at the right concentration, are not spoilage at all. They are flavour. The depth of an aged cheese, the tang of a fermented sausage, the savour of a fish sauce that has stood for a year: these are, in significant part, the taste of the very same amines, produced by the very same decarboxylation, that in another vessel we would have called rot.

Aged cheese and rotting fish share a chemistry. The only difference is who was invited.

Here is the thing that ought to stop a formulator in their tracks. The enzymes that carry out this decarboxylation are found in the microbes of spoilage and in the microbes of fermentation alike. The reaction is the same. The products are the same family. What separates the cheese from the rot is not the chemistry but the control: which organisms were present, at what temperature, for how long, under what salt and what acid. Choose the culture and hold the conditions, and you get the sausage. Let the wild flora arrive on their own terms, and you get the bin.

Fermentation, in other words, is spoilage you chose the microbes for. Rot is spoilage that chose its own.

Fermentation is spoilage you chose the microbes for. Rot is spoilage that chose its own.

I set this at the end of the essay, and not as a flourish, because of where the alternative-protein industry actually stands. A great deal of the most serious work in the field is fermentation: mycoprotein grown in tanks, precision-fermented ingredients, biomass raised by cultures under tight control. The industry is already, and expertly, working the far end of the very freshness gradient this essay has walked. It has spent its skill on the controlled end, on safety and consistency and the avoidance of the aversive amines, which is exactly right and not to be second-guessed.

The question I want to leave in the room is subtler than safety. Meat is not palatable because it sits at one fixed point on this gradient. It is palatable because a carnivore evolved to read the whole of it: the fresh-kill signal at the top, the umami of the peak, the first bitter hint of the turn, and yes, in aged and cured and fermented forms, some of the controlled notes of the descent. If we are learning to build proteins by fermentation, we are already speaking the last dialect on the gradient. The unanswered question is whether we are shaping it only away from what is dangerous, or also toward what an animal would recognise as the deep, aged, savoury language it has always known food to speak.

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THE WHOLE ENSEMBLE

Stand back now from the gradient we have walked, and look at the whole of it at once.

At the top is the fresh kill, and the blood-borne molecule a predator reads off the wound in the first instant. Then the savour rising as the nucleotides climb to their peak, the umami of a thing at its freshest. Then the first faint bitterness as that peak begins to pass, the taste telling the animal the clock has started. Beneath all of it, from the very beginning, the fat and its phospholipids, carrying the name of the species in molecules no scale will weigh. Through the middle, the meat quietly digesting itself, cathepsins carving savour out of structure. And at the far end, the controlled descent, the aged and fermented notes that are spoilage tamed and made delicious. This is not a list of ingredients. It is an ensemble, and every part of it is playing at once.

That is the word I have been circling for three of these conversations. Meat is not a substance. It is an ensemble, a whole orchestra of signals sounding together, and a carnivore did not evolve to eat any one of them. It evolved to hear the chord.

And an ensemble is more than the sum of its players. This is the part the specification can never hold, because it is not written in any one component but in the way they sound together: the proportion, the timing, the interference of one note against another. You could fill every chair on the stand, source each molecule on the list and set it in its place, and still not have meat, because meat was never the collection of its parts. It was their playing together. The chord is not the notes.

And this is the thing I most want to leave with anyone rebuilding meat from something that was never an animal. When we replace meat, we do not replace the orchestra. We replace some of the players. We are very good now at the nutrition, which is the section that keeps the animal alive; we are increasingly good at the roasted, Maillard savour, which any substrate can be taught to sound. But the fat that carries the species, the nucleotide clock, the self-made peptides, the deep controlled notes of the aged descent, many of these chairs are still empty, or filled by a player reading from a different score.

Here is the question that keeps me up, and that I do not think the industry has yet asked itself squarely. An incomplete orchestra is not simply a quieter orchestra. Leave out the strings and you do not get the same symphony played softly; you get a different piece, and sometimes a discordant one. The parts that are present, sounding without the parts that are absent, can be worse than silence, because the animal is not comparing our formulation to nothing. It is comparing it to a chord it has known for forty million years. A bowl that delivers perfect nutrition and half the ensemble may not read to a cat as incomplete meat. It may read as something that is trying to be prey and failing, which is a harder thing to forgive than a food that never pretended at all.

I do not say this to discourage the project. I say it because the project is worth doing well, and doing it well means being honest about what is actually on the stand. Nutrition was never going to be the whole score. It was the first section to learn its part. The work now is the rest of the ensemble: to find which of the empty chairs matter most to the animal, and in what combination, and whether the players we do have are sounding in tune with one another or merely sounding.

Perhaps meat was never just an ingredient. It was an orchestra, and the animal at the bowl has been listening to the whole of it all along. The question for the next diet is not whether it can analyse like meat. It is whether, when the animal leans in to listen, the chord rings true.

Dr. rer. nat. habil. Dr. Seronei Chelulei Cheison
Langwedel, Niedersachsen

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Sources drawn on for this essay

1. Mottram, D.S. (1998). Flavour formation in meat and meat products: a review. Food Chemistry 62(4): 415–424. doi:10.1016/S0308-8146(98)00076-4
2. Mottram, D.S. & Edwards, R.A. (1983). The role of triglycerides and phospholipids in the aroma of cooked beef. Journal of the Science of Food and Agriculture 34(5): 517–522.
3. Toldrá, F. & Flores, M. (1998). The role of muscle proteases and lipases in flavor development during the processing of dry-cured ham. Critical Reviews in Food Science and Nutrition 38(4): 331–352. doi:10.1080/10408699891274237
4. Howgate, P. (2006). A review of the kinetics of degradation of inosine monophosphate in some species of fish during chilled storage. International Journal of Food Science & Technology 41(4): 341–353. The freshness K-value derives from Saito, T., Arai, K. & Matsuyoshi, M. (1959), Bulletin of the Japanese Society of Scientific Fisheries 24: 749–750.
5. McGrane, S.J., Gibbs, M., Hernangomez de Alvaro, C., Dunlop, N., Winnig, M., Klebansky, B. & Waller, D. (2023). Umami taste perception and preferences of the domestic cat (Felis catus), an obligate carnivore. Chemical Senses 48: bjad026. doi:10.1093/chemse/bjad026
6. Gassenmeier, K. & Schieberle, P. (1994). Formation of the intense flavour compound trans-4,5-epoxy-(E)-2-decenal in thermally treated fats. Journal of the American Oil Chemists’ Society 71(12): 1315–1319. doi:10.1007/BF02541347
7. Watson, P.E., Thomas, D.G., Bermingham, E.N., et al. (2023). Drivers of palatability for cats and dogs: what it means for pet food development. Animals 13(7): 1134. doi:10.3390/ani13071134
8. Prester, L. and the Frontiers review of biogenic amines in seafood (2012), Frontiers in Microbiology 3: 188, doi:10.3389/fmicb.2012.00188; on fermentation as controlled decarboxylation, see the review of biogenic amines in fermented foods (2024), Heliyon, doi:10.1016/j.heliyon.2024.e25553.

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Dr. rer. nat. habil. Dr. Seronei Chelulei Cheison is the founder and Chief Executive Officer of Sinonin Biotech GmbH, a biotechnology company focused on alternative protein and palatability enhancer innovation and application for petfood formulations. He formerly led alternative protein and palatant development projects at the Mars Petcare Global Innovation Centre in Verden, and spent close to two decades in academic research on enzymatic protein hydrolysis, holding a doctorate from Jiangnan University and a habilitation from the Technical University of Munich.

Sinonin Biotech GmbH is a partner in two consortia funded under the Circular Bio-based Europe Joint Undertaking: ZEST, on fungal fermentation of agricultural residues, and PROSCALE, on scalable microbial protein ingredients, which runs from September 2026 to August 2030.

Co-funded by the European Union under Grant Agreement No. 101157382 (ZEST) and Grant Agreement No. 101288362 (PROSCALE). Views and opinions expressed are however those of the author only and do not necessarily reflect those of the European Union or CBE JU. Neither the European Union nor the CBE JU can be held responsible for them.

Petfood Palatability and the Fresh-Kill Signal Cats Read as Prey

The Friday Conversation · No. 2

The Biological Signal

Why the cat at the bowl is not smelling meat. It is smelling a fresh kill, and the single molecule that tells it so is one the flavour industry has spent twenty-five years trying to bottle.

Dr. rer. nat. habil. Dr. Seronei Chelulei Cheison

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Cut a finger and bring it to your nose, and you will recognise at once a smell you have never been taught: sharp, metallic, faintly like wet iron. You did not learn it. It arrived with you. And it has a name, a single molecule, one of some thirty that gas chromatography can pull out of a drop of blood, and the only one your nose truly needs.

For a human being that smell is a curiosity, occasionally an alarm. For an obligate carnivore it is not a smell at all. It is an instruction.

For decades the petfood industry has spoken of “meat flavour” as though a cat crossed the kitchen because it enjoyed the taste of meat, the way a person enjoys the taste of beef. That is a comfortable anthropomorphism and it is not what evolution built. The cat is not a small person with fur. It is a predator whose sensory apparatus was shaped by a single recurring problem, asked over millions of years and millions of kills: is this prey fresh enough to be worth eating?

That question is answered long before anything reaches the tongue. It is answered in the air.

I raise this now, and not as a curiosity, because the category is in the middle of the largest reformulation in its history. The industry is moving (under pressure from cost, from carbon, from supply, and from a genuine shift in what owners will buy) away from meat and toward alternative proteins: fungal biomass, single-cell protein, insect meal, and at the furthest edge, plant-based and outright vegan diets for animals that evolution designed around a carcass. I am not here to tell that movement it is wrong. Much of it is right, and some of it is overdue. I am here to name, precisely and early, the thing standing between it and the bowl.

Because the transition will not be decided by whether these proteins can nourish a cat. It will be decided by whether the cat recognises them as prey.

A word on how I mean to do it. In the first of these Friday conversations I set five questions on the table and closed none of them. This one moves differently (a single question, followed as far down as I can take it), but the discipline is the same. I do not intend to answer this one either. I intend to show you how deep it goes, name the people who could answer it, and leave it, on purpose, where a conversation can still reach it.

The cat is not a small person with fur. It is a predator asking one question: is this fresh enough to be worth eating?

The nose that threw things away

An omnivore’s senses are a compromise. They must find ripe fruit and reject unripe, detect sweetness and starch, weigh a hundred plant and animal foods against one another. The cat abandoned all of that. Somewhere on the way to obligate carnivory it lost the working sweet-taste receptor entirely: the gene is a pseudogene, a broken cassette, and it is why a cat is indifferent to sugar in a way no dog ever is. What the lineage saved on sugar it spent on meat. The equipment that survived is equipment for one job: to find, assess and commit to prey.

So when we sit down to reformulate that prey (to replace the animal tissue in the bowl with mycoprotein, with fermented biomass, with a protein a European hectare threw away), we are not merely swapping a nutrient. We are addressing a sensory system that was built, at the cost of everything it discarded, to detect the one thing we have taken out.

The molecule

When blood meets air, the fats within it begin to oxidise almost immediately. Lipid peroxidation is not exotic chemistry; it is the same family of reactions that turns fat rancid, running here in seconds rather than months. Among its products is an oxygenated aldehyde with an unwieldy name, trans-4,5-epoxy-(E)-2-decenal, mercifully shortened by the people who study it to E2D.

E2D is the character-impact compound of blood. Of the roughly thirty volatiles a machine finds in a blood sample, this is the one a trained human nose picks out as the metallic, blood-like note, a fact established not by the instrument, which nearly missed it, but by human panellists smelling the gas chromatograph’s output one peak at a time. It is extraordinarily potent. Human detection thresholds sit in the parts-per-trillion range; the mouse, for its own reasons, is more sensitive still.

And here is the detail that ought to reorganise how we think about the whole category: no open wound, no E2D. The molecule is not a property of meat. It is an event, with a clock. It appears when tissue is broken and blood meets oxygen (at the moment of the kill), and it is gone again as the chemistry moves on. It does not signal meat. It signals a fresh kill. What comes later, as flesh actually decays, is a wholly different and largely repellent set of volatiles. E2D is the top of the freshness curve, not the bottom of the rotten one.

It does not signal meat. It signals a fresh kill, and it is gone again before the meat has time to rot.

What the animals actually did

Between 2014 and 2017 a group of Scandinavian researchers did the experiment that turns this from chemistry into biology. They took pure E2D (no blood, just the single synthesised molecule) and painted it onto wooden logs, and gave it to captive predators. Siberian tigers, Asian and African wild dogs, South American bush dogs, later a pack of wolves. The animals sniffed, licked, bit, pawed and dragged the logs exactly as they did for a fresh kill. One molecule reproduced the response of the whole complex mixture. Present the same compound to a mouse and it does the opposite: avoidance, vigilance, retreat. The identical cue, read as dinner by the predator and as danger by the prey, across species that last shared an ancestor a very long time ago. The word the field uses is conserved, and it is the right one.

Now the honest edge of this, which the essay will not step around, because stepping around it is precisely the habit I am arguing against.

The tiger is a felid. The domestic cat is a felid. The lineage, the diet, the obligate carnivory are shared. It is a reasonable and probably correct inference that Felis catus reads E2D as the tiger does. But inference is not evidence, and I want to be exact about what I am and am not claiming. To the best of my search, no publicly published study has put a domestic cat in front of purified E2D, measured its investigation and its intake, and reported the number. I make the distinction on purpose. The great palatability houses run trials they never publish, and it is entirely possible the experiment has already been done behind a confidentiality wall and quietly priced into a product. What I can say is that it is not in the public record, not in the behavioural journals, which stopped at tigers, wolves and wild dogs; and not, I checked, in the flavour patents that first put a commercial value on this molecule, which rest their entire case on human tasters smelling the compound in water. The most commercially consequential species in the palatability business is absent from the one experiment that would matter most to it, at least anywhere the rest of us are allowed to read.

I would be glad to be shown the study I could not find. And if it truly is not there (if the number does not exist, or exists only where none of us can see it), then that absence is not a footnote. It is the conversation.

The most commercially consequential species in the whole business is missing from the one experiment that would matter most to it.

A word to the dog

Before anyone assumes this is a cat’s story alone: it is not. The clearest behavioural evidence for E2D comes from the dog family. The wolf, the domestic dog’s own ancestor, worked the scented logs as avidly as the tiger did, and three wild-dog species did the same.

E2D is not a feline signal. It is a carnivore signal, and the dog reads it plainly.

What differs is not whether the dog detects the kill, but how much rides on the detection. The dog is the better nose of the two, with more than twice the cat’s olfactory neurons, and it is an omnivore with the full five-taste palate, sweet included, and a working flexibility the cat traded away. It reaches acceptance by many roads. The cat reaches it by few: no sweet receptor, fewer taste buds, a narrower diet, a deeper neophobia. So the same molecule that is one appetite cue among several for the dog is, for the cat, closer to the whole case. I have told this through the cat not because the dog is unmoved, but because the cat is where a single wrong note is likeliest to end in a turned back and an untouched bowl. Solve the cat, the finickier customer, and you have cracked the hardest bowl in the business.

Why this is not another palatant story

The systems that carry the category today are genuinely good, and I will not pretend otherwise. Animal digests, hydrolysed proteins, the browning chemistry of cooking, these reproduce, with real skill, much of the flavour a cooked and digested meat delivers. They are the reason a modern coated kibble works at all, and I spent years of my own working life inside that toolkit. Nothing here displaces them.

But E2D is a different kind of message, and the difference is the point. A digest imitates cooked meat: the kitchen, the retort, the long warm chemistry of a meal. E2D imitates fresh prey: the wound, the moment, the kill. These are not two intensities of the same signal. They are two different sentences spoken to two different parts of the animal’s evolutionary memory: one about food that has been cooked, one about food fresh from the kill.

There is a practical consequence that formulators will recognise immediately. E2D is volatile and reactive; it would no more survive the heat of an extrusion barrel than a fragrance would survive a hot iron. You do not scent a shirt and then press it; you press it first and lay the scent on after. A signal like this could not be built into the dough. It would have to be delivered afterward (through the fat coat, the liquid palatant, the topcoat applied once the kibble had cooled), so that its message waited in the headspace the instant the bag was opened and the bowl was filled. Its job would not be nutrition. Its job would be the first sentence the animal reads before it has taken a step.

And is it? Is E2D, or some designed cousin of it, already sitting in a product on a shelf, doing exactly this? I do not know, and I will not pretend to. That is the honest edge of an outsider’s knowledge, and it is precisely the sort of thing I would rather ask in the open than guess at in private. If it is already there, then someone has been speaking the cat’s oldest language for years without saying so. If it is not, then the most potent word in that language is going spare.

The industry knew, and the regulator hesitated

None of this escaped the people whose business is flavour. More than two decades ago the flavour and fragrance house Givaudan patented the isomers of epoxydecenal specifically for their potency, in United States patents resting on the observation that the molecule’s handedness matters, that one optical form of the same compound carries more sensory punch than its mirror image. Even chirality, the difference between a left hand and a right, turns out to be something biology is reading. That is the level of detail the category has been prepared to pursue.

And yet the same molecule sits under a regulatory shadow. In the European Union, the flavouring 4,5-epoxydec-2-enal was assessed by EFSA and could not be cleared: it tested positive for genotoxicity in an in-vitro micronucleus assay, a result the follow-up in-vivo work confirmed in the liver, and the panel concluded it could not be evaluated as safe under the standard procedure. In 2017 it was removed from the EU list of permitted flavourings. That verdict was reached for human food, and petfood is a different regime with different exposures and different rules; one does not automatically carry to the other. But it is a caution written in ink, not pencil, and any honest account of E2D has to carry it too.

It is worth being exact about the two numbers involved, because they sit strikingly far apart. The signal a predator reads operates at the edge of physics: a cat's fresh-kill cue is a matter of parts per trillion, picograms of the molecule in the air above the wound. The genotoxic flag, by contrast, was raised by feeding rats near-maximum-tolerated doses, in the region of three hundred milligrams per kilogram straight into the stomach, enough to leave necrosis in the liver. Between the concentration that carries the message and the concentration that does the damage lies a gap of many orders of magnitude, and the same chemical reactivity that lights up a genotoxicity assay in a dish is precisely what makes E2D a fleeting top-note in the world rather than a compound that lingers or accumulates. None of which clears it; the flag is real and I will not explain it away. But it does sharpen the question. The hazard was shown in a rodent liver, for a human additive, at a dose no palatant use would approach, in a species that is not the one eating the bowl.

Which leaves the honest account not with a verdict but with a gap in the evidence, and it is worth naming plainly. Is there a single published study of what E2D does in a cat, at the vanishing concentrations a cat would actually meet, rather than in a rat gavaged to its limit? If there is, I have not found it. And if there is not, then we are weighing a signal biology has used for millions of years against a hazard measured in the wrong species, by the wrong route, at ten orders of magnitude the wrong dose, and calling the balance settled. Is it?

Applied chemical ecology

Here is where the questions get harder, and I would rather leave them open than pretend I have closed them.

Modern palatant development, at its sharpest, is no longer flavour creation in the culinary sense, the art of making something taste nice. It looks more like applied chemical ecology: the deliberate use of signals evolution spent millions of years teaching an animal to obey. And if that is what the discipline has quietly become, then is the whole alternative-protein transition asking the wrong question of itself? We keep asking whether a fermented biomass can nourish a cat. Should we not be asking, first and far more urgently, whether it can convince one?

We keep asking whether a fermented biomass can nourish a cat. We should be asking whether it can convince it to eat.

Because a diet the animal refuses has an efficacy of zero, and the refusal is decided in the headspace above the bowl, in the first second, before a single requirement on the label has been tested.

Which brings the sharpest question to the table, the one that decides whether the vegan bowl is a biological dead end or merely an unsolved problem. Is the signal the cat is chasing an irreducible property of meat, something that exists only as long as the muscle does? Or is it a molecule, a single defined compound that forms wherever the right fats oxidise, and that a chemist could, in principle, build from feedstocks that never saw an animal? The science leans hard toward the second answer; the whole reason a company could patent E2D’s isomers is that it is a thing you can make. But if that is right, then where does it leave the argument the industry keeps having? Can the kill be written by a factory rather than a carcass? Can the instruction the cat obeys be sprayed onto a fungal kibble that a tiger’s ancestors would not recognise as food, and would the cat obey it anyway?

And there is a further turn to this that is worth holding onto, because it changes what the molecule is for. It would be easy to treat E2D as a beautiful but unreachable thing, a signal to admire and not use, especially with a regulator’s flag against the isolated compound. That would be the wrong lesson. E2D is not only the smell of a raw wound; it is also generated in situ, by heat, from polyunsaturated fatty acid precursors through ordinary oxidation chemistry. The fresh kill writes this word in seconds; heat can write it again from the fats. Which means the question was never “where do we buy the molecule,” but “what chemistry, and which precursors, let a food generate it for itself.” That is a thread for the conversations still to come, on how these signals form, from which precursors and on what timetable, and on the fats themselves, the most underrated players at the bowl.

I do not think those are rhetorical questions. I think they are unanswered, and I think the answers are worth more than another percentage point of protein.

And here is the one I most want to put to the people reading this, because I cannot answer it alone. We have been assuming the difficulty with insect and plant and fermented proteins is that they lack the signal, that there is no E2D in a mealworm, no fresh-kill note in a fungal biomass. But I do not actually know that, and neither, as far as I can find, does the public literature. Insects are lipid-rich and oxidise readily; the raw chemistry that makes E2D is present in them, even if the blood-metallic note has never been reported and their loudest volatiles point the nose somewhere else entirely, toward fish, earth and cheese. So the real question is open, and it is yours as much as mine. Is the signal simply absent from these materials? Or is there a different signal, one native to insects or microbes or plants, that a carnivore could be taught to read as readily as it reads the kill, that we have simply not gone looking for? If you know of such a molecule, or if you know that E2D is in fact hiding in one of these ingredients, I would genuinely like to be told.

Because strip the argument to its frame and this is what we have done. Evolution taught the cat to smell a fresh kill. We have answered by offering it a cooked meal, nutritionally balanced to the last milligram, and set it before an animal that has never cooked, never stored, never in its evolutionary life encountered food that was prepared rather than caught. We solved the gut and may have forgotten the nose. Have we built the perfect dinner and failed to announce it as dinner at all?

So let me put the essay’s own question back on its feet. Is the compound the point, or is the principle? If what an obligate carnivore reads can be decoded, defined and reproduced, then what exactly is standing between the plant-based movement, the alternative-protein developers and the palatant houses and the bowl they all want the animal to empty? Is it really whether the diet is complete, or whether it is credible to a nose calibrated by evolution to detect a fresh kill?

We have spent a generation asking whether these new proteins can nourish a cat.

The cat has been asking a different question the whole time. It has been asking whether something has just died. Can we learn to answer yes, and mean it, without a single animal having to?

Somebody should put a domestic cat in front of the molecule and publish what the bowl says. Until someone does, we are inferring the most important customer in the category from the behaviour of a tiger, and preparing to build the future of the bowl on that inference. Is that good enough?

I am asking.

And while we wait for the answer, here is the shape I think the question is taking.

We have spent twenty years learning how to make proteins without animals.

Perhaps we will spend the next twenty learning how to make them read, to the animal, like one.

Because the future does not belong to alternative proteins or to inclusive diets, as if the two were rivals. It belongs to an inclusive diet built around alternative proteins, and made credible to the creature that has to eat it. E2D is only one word in that language, and perhaps not even the word we will end up using. The point was never the molecule. The point is that the signal can be learned, and that the learning has an examiner.

And the bowl will answer before the laboratory does.

Dr. rer. nat. habil. Dr. Seronei Chelulei Cheison
Langwedel, Niedersachsen

The thread this essay opens, how these signals form, from which precursors and on what timetable, is taken up in the third Friday Conversation: Meat Is More Than Protein.

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Sources drawn on for this essay

Nilsson, S., Sjöberg, J., Amundin, M., Hartmann, C., Buettner, A. & Laska, M. (2014). Behavioral responses to mammalian blood odor and a blood odor component in four species of large carnivores. PLOS ONE 9(11): e112694. doi:10.1371/journal.pone.0112694

Arshamian, A., Laska, M., Gordon, A.R., et al. (2017). A mammalian blood odor component serves as an approach–avoidance cue across phylum border, from flies to humans. Scientific Reports 7: 13635. doi:10.1038/s41598-017-13361-9

Buettner, A. & Schieberle, P. (2001). Aroma properties of a homologous series of 2,3-epoxyalkanals and trans-4,5-epoxyalk-2-enals. Journal of Agricultural and Food Chemistry 49(8): 3881–3884. Establishes trans-4,5-epoxy-(E)-2-decenal as the metallic, blood-like character-impact odorant. doi:10.1021/jf0104329

Pettersson, H., Amundin, M. & Laska, M. (2018). Attractant or repellent? Behavioral responses to mammalian blood odor and to a blood odor component in a mesopredator, the meerkat. Frontiers in Behavioral Neuroscience 12: 152. doi:10.3389/fnbeh.2018.00152

Li, X., Li, W., Wang, H., et al. (2005). Pseudogenization of a sweet-receptor gene accounts for cats’ indifference toward sugar. PLOS Genetics 1(1): e3. doi:10.1371/journal.pgen.0010003

Givaudan SA (inventors A. Daniher, S. Furrer, A. Goeke), US Patent 6,335,047 and continuation-in-part US Patent 6,451,366 (both granted 2002), Epoxydecenal isomers: isomeric forms of epoxydecenal with enhanced flavour potency, the enriched (−) optical isomer carrying greater sensory potency than its mirror image.

EFSA CEF Panel (2017). Scientific Opinion on Flavouring Group Evaluation 226, Revision 1 (FGE.226Rev1): genotoxicity data on 4,5-epoxydec-2(trans)-enal [FL-no. 16.071]. EFSA Journal 15(5): 4847. The substance raised a genotoxicity concern and could not be evaluated under the Procedure (and was subsequently removed from the EU flavourings list). doi:10.2903/j.efsa.2017.4847

Gassenmeier, K. & Schieberle, P. (1994). Formation of the intense flavour compound trans-4,5-epoxy-(E)-2-decenal in thermally treated fats. Journal of the American Oil Chemists’ Society 71(12): 1315–1319. Establishes that E2D forms on heating from the hydroperoxides of linoleic acid. doi:10.1007/BF02541347

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Dr. rer. nat. habil. Dr. Seronei Chelulei Cheison is the founder and Chief Executive Officer of Sinonin Biotech GmbH, a biotechnology company focused on alternative protein and palatability enhancer innovation and application for petfood formulations. He formerly led alternative protein and palatant development projects at the Mars Petcare Global Innovation Centre in Verden, and spent close to two decades in academic research on enzymatic protein hydrolysis, holding a doctorate from Jiangnan University and a habilitation from the Technical University of Munich.

Sinonin Biotech GmbH is a partner in two consortia funded under the Circular Bio-based Europe Joint Undertaking: ZEST, on fungal fermentation of agricultural residues, and PROSCALE, on scalable microbial protein ingredients, which runs from September 2026 to August 2030.

Co-funded by the European Union under Grant Agreement No. 101157382 (ZEST) and Grant Agreement No. 101288362 (PROSCALE). Views and opinions expressed are however those of the author only and do not necessarily reflect those of the European Union or CBE JU. Neither the European Union nor the CBE JU can be held responsible for them.

Petfood Palatability in the Age of Alternative Proteins

The Friday Conversation · No. 1

Palatability  ·  Alternative Proteins  ·  Petfood

Petfood Palatability in the Age of Alternative Proteins: The Conversation We Need to Have

Five questions about what animals actually recognise as food, and why we keep measuring the wrong thing.

By Dr. rer. nat. habil. Dr. Seronei Chelulei Cheison
Langwedel, Niedersachsen

The same diet, two species, one empty bowl

Somewhere tonight a cat will walk away from a bowl of food that is nutritionally faultless. Every amino acid balanced against a published requirement, every micronutrient supplemented, digestibility measured and documented, the whole formulation defensible to any regulator who cares to ask. And the animal will sniff it, decline it, and sit down beside it.

That refusal is the most important data point in our industry, and it is the one we have organised ourselves least well to understand.

The petfood industry is entering one of the most consequential periods of innovation in its history. Insect meals, microbial biomass, precision-fermented ingredients, cultivated meat and novel plant proteins are no longer confined to research laboratories or niche launches; they are steadily becoming part of mainstream product development, and the regulatory frameworks are beginning to move with them. The conversation has understandably centred on sustainability, nutritional adequacy, ingredient security and environmental impact. These are important discussions, and they will continue to shape the future of companion animal nutrition.

Yet they all rest upon a deceptively simple assumption.

That the pet willingly eats the food.

More importantly, that it continues to do so, day after day, bowl after bowl, long after the novelty has worn off.

Perhaps this is where our industry should pause.

For decades, palatability has been recognised as an essential component of product development, but seldom as its defining strategic challenge. It has often been viewed as the final optimisation step — something applied after the formulation has been completed and before feeding trials begin.

That perspective may no longer be sufficient.

As we progressively reformulate with lower-meat diets and alternative proteins, palatability is moving from the end of the development process to its very centre. It is becoming the bridge between scientific innovation and commercial success. In human food, the barrier to novel protein is persuasion; you can argue a person into a lentil. In petfood, the barrier is engineering. The animal will eat the bowl or it will walk away, and no marketing budget has ever changed its mind.

Owners buy the first bag. Pets decide the second.

I want to set out five conversations I believe we should be having. I have views on all of them, and I have deliberately not concluded any of them, because the people best placed to answer are scattered across formulators, ingredient developers, panel operators and researchers who rarely find themselves in the same room.

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Conversation One

Have we confused nutritional replacement with behavioural replacement?

The industry has made remarkable progress in demonstrating that many alternative proteins can contribute to nutritionally complete diets. Essential amino acids can be balanced. Micronutrients can be supplemented. Digestibility continues to improve. In many respects, the question of nutritional adequacy is becoming increasingly manageable.

But nutrition and feeding behaviour are not the same challenge.

Replacing the nutritional contribution of meat does not necessarily replace the biological signals that companion animals have evolved to associate with food.

For much of our industry's history, meat has quietly performed several functions simultaneously. It has provided protein, energy and micronutrients, but it has also supplied free amino acids, nucleotides, animal fats, Maillard reaction precursors, volatile sulphur compounds and a great many other molecules that together create a sensory experience. We have rarely needed to separate these functions, because meat conveniently delivered them together.

Alternative proteins force us to do exactly that.

Meat does five jobs at once. We never asked which one mattered.

And here I find myself genuinely uncertain. If meat performs five jobs at once, which of them is load-bearing? I am not aware of published work that takes it apart — that holds the amino acid profile constant while removing the nucleotide contribution, or the reverse, and reports what the animal does. Within ZEST, Sinonin Biotech leads the assessment of mycoprotein biochemical and techno-functional properties and the development and testing of petfood prototypes, which is precisely the territory in which this question becomes practical rather than academic. I would be glad to be pointed towards work that has already answered it.

Perhaps the more interesting question is no longer whether alternative proteins can replace meat nutritionally.

Perhaps it is whether they can replace what meat communicates biologically.

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Conversation Two

Is meat an ingredient, or a sensory language?

One of the unintended consequences of alternative proteins is that they oblige us to reconsider what meat actually contributes.

Perhaps meat is not simply an ingredient. Perhaps it is a remarkably efficient carrier of sensory information — free amino acids that shape taste perception; 5'-nucleotides generated by the post-mortem breakdown of muscle tissue and almost entirely absent from plant material; animal fats that yield characteristic aroma compounds under process heat; Maillard and Strecker products that depend on sulphur amino acids many plant proteins supply only sparingly; and, behind all of it, the post-ingestive reinforcement that quietly teaches an animal what to choose next week.

These are not merely chemical constituents. Together they form a biological language through which dogs and cats recognise food.

When we remove meat, we are not only changing the source of protein. We are changing that language.

We are not changing the protein. We are changing the language.

Equally, alternative ingredients arrive speaking their own. Plant proteins may contribute bitter peptides, green or grassy notes and anti-nutritional compounds. Insect-derived materials bring different textural and aromatic characteristics. Fermentation products introduce another profile again.

These are not flaws. They are simply a reminder that every ingredient communicates something, whether or not we designed it to.

The question is whether we understand those conversations well enough to conduct them deliberately.

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Conversation Three

Are we designing for one animal, or two?

We speak of petfood palatability as though it were a single discipline. It may be closer to two.

Dogs, shaped by millennia of proximity to human settlements, display considerable dietary flexibility, and their food selection appears substantially odour-led. Cats remain obligate carnivores whose selection is more taste-dominant, whose format preferences are largely established around weaning, and whose sensory apparatus is tuned with unusual precision to animal-derived material.

One difference deserves to be stated plainly, because it is structural rather than a matter of degree. The gene encoding the sweet taste receptor subunit is non-functional in the cat.

Not diminished. Absent.

The cat's sweet receptor is not weak. It is absent.

Which means that a considerable portion of the toolkit available for managing bitterness in lower-meat canine diets is simply unavailable in the species that is also more bitter-sensitive, more texture-rigid and more neophobic than the dog.

I have a particular interest in this problem, having spent a large part of my research career on enzymatic protein hydrolysis and on the bitterness that hydrolysis generates. When you cleave a protein you expose hydrophobic residues, and hydrophobic peptides read bitter; I published on the simultaneous desalting and debittering of whey protein hydrolysates in 2007, and returned to the influence of environmental conditions and substrate pre-treatment on whey protein hydrolysis in a review with Ulrich Kulozik a decade later. The chemistry is not mysterious. What I am far less certain about is what the industry is actually doing with it now, in cats, at commercial inclusion levels, without recourse to sweetness.

I suspect practice here is well ahead of publication. If it is, I would rather hear it from the people doing the work than speculate about it from the outside.

There is a further observation that has been treated, I think, as a procurement inconvenience when it may be scientifically interesting. Trial data compiled by FEDIAF suggests that dogs may favour black soldier fly larvae meal while cats favour yellow mealworm — a plain divergence with no settled explanation. Lipid profile? Chitin fraction? Something in the volatile signature that one species reads as food and the other does not?

If we cannot explain why two domestic species rank the same two insects differently, it is worth asking how confidently we can predict acceptance of anything genuinely novel.

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Conversation Four

Are we designing formulations, or engineering preference?

Historically, palatability has been treated as a finishing operation. Formulate, extrude, dry, coat, validate. That workflow has served the industry exceptionally well.

But as meat inclusion declines, it may become increasingly difficult to separate formulation from palatability.

One observation illustrates this particularly well. In many dry petfoods, the overwhelming majority of the formulation passes through the extruder before a final coating stage delivers much of the product's sensory identity — and frequently those coatings still rely on animal-derived fats, digests or hydrolysates.

This is not a criticism. These ingredients remain highly effective, and their continued use is entirely rational.

It does, however, illustrate the nature of the transition we are undertaking. In a good many formulations we have replaced meat as a nutritional ingredient while continuing to depend upon it as a sensory technology.

We replaced meat as a nutrient. We kept it as a flavour.

It also explains something we say too rarely. The coating step is what makes dry formats forgiving; it separates the base matrix from the sensory signal and gives us a stage at which to correct course. Wet formats offer no such separation. They must be intrinsically palatable, first time, with nothing applied afterwards to rescue them.

Which raises an uncomfortable practical question. If lower-meat dry dog food is approaching a solved problem, what is the honest status of lower-meat wet cat food? Is anyone close? Or have we collectively, and rather quietly, deprioritised the hardest quadrant because the easier three pay sooner?

And behind that, a broader one. Are we replacing proteins, or are we beginning to redesign the mechanisms through which companion animals recognise food?

If it is the latter, palatability can no longer be regarded as something added at the end of development. It becomes a design discipline from the outset.

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Conversation Five

Are we measuring the right outcome?

The industry has long relied upon robust palatability methodologies, particularly paired preference testing, and these methods have served ingredient developers extremely well.

Yet the transition towards alternative proteins raises a question about what, exactly, we are measuring.

A two-bowl comparison is exceptionally sensitive to small formulation differences. That sensitivity derives from simultaneous presentation against a control — which is precisely what makes it invaluable during development, and precisely what makes it unlike any situation the animal will ever encounter at home.

Consider what that means for a genuinely novel diet. It is assessed on an unfamiliar aroma profile, at first exposure, in an animal whose neophobia is a feature of its biology rather than a defect in the product. Meanwhile the one mechanism that most favours reformulated diets, post-ingestive learning, requires repeated exposure to operate at all, and the design excludes it.

Commercial reality unfolds rather differently. Pets eat one food at home. Owners observe feeding behaviour across weeks and months. Confidence accumulates slowly. Repurchase follows repeated positive experience.

The trial rewards preference. The market rewards repurchase.

So let me ask the narrow version rather than the rhetorical one. Where is the ninety-day monadic comparison between an alternative-protein diet and its meat-based equivalent? I cannot find one published. If it exists, it deserves considerably more attention than it has received. If it does not, that absence tells us something about what we have chosen to measure, and what we have chosen not to look at.

Success depends less upon winning the first comparison than upon earning the next purchase.

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The Grand Finale

The bowl is the only honest judge

The conversation around alternative proteins is usually presented as an ingredient story. It is equally a sensory story.

The companies that succeed over the coming decade may not be those with access to the newest protein technologies; many of those will become broadly available across the industry. The greater advantage may lie in understanding feeding behaviour more deeply than competitors — in integrating sensory chemistry, behavioural biology, process engineering, flavour science and nutrition into what might reasonably be called palatability engineering.

The term matters less than the shift in thinking it represents.

The industry has learnt how to formulate with meat. Its next task is learning how to formulate without relying upon it, while preserving the sensory experience that keeps pets returning to the bowl and owners returning to the shelf. That cannot be solved by nutrition alone, nor by flavour chemistry alone, nor by processing alone.

I have left these five conversations open on purpose. I am more interested in what the people running the trials and formulating the diets know than in restating what I think I know. If you are working on any of them — the deconstruction question, the feline bitterness problem, or the longitudinal data — I would rather have your answer than repeat my own.

We have spent a decade asking whether these proteins can nourish a dog or a cat.

The animal has been answering a different question all along.

A diet the animal refuses has an efficacy of zero.

Dr. rer. nat. habil. Dr. Seronei Chelulei CheisonLangwedel, Niedersachsen

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Dr. rer. nat. habil. Dr. Seronei Chelulei Cheison is the founder and Chief Executive Officer of Sinonin Biotech GmbH, a biotechnology company focused on alternative protein and palatability enhancer innovation and application for petfood formulations. He formerly led alternative protein and palatant development projects at Mars Petcare, and spent close to two decades in academic research on enzymatic protein hydrolysis, holding a doctorate from Jiangnan University and a habilitation from the Technical University of Munich.

Sinonin Biotech GmbH is a partner in two consortia funded under the Circular Bio-based Europe Joint Undertaking: ZEST, on fungal fermentation of agricultural residues, and PROSCALE, on scalable microbial protein ingredients, which runs from September 2026 to August 2030.

Co-funded by the European Union under Grant Agreement No. 101157382 (ZEST) and Grant Agreement No. 101288362 (PROSCALE). Views and opinions expressed are however those of the author only and do not necessarily reflect those of the European Union or CBE JU. Neither the European Union nor the CBE JU can be held responsible for them.