Yeast biomass is widely utilized in the food and beverage industries for its ability to enhance flavours, particularly umami—a savoury taste that is one of the five basic tastes in food. The use of yeast for flavour enhancement has gained popularity in both human and pet foods, especially as consumers are increasingly seeking natural flavourings that can replace synthetic additives. This technology not only deepens the taste profiles of food but also serves as a valuable nutritional supplement, contributing amino acids, vitamins, and minerals to the diet.
Yeast extract are concentrates of the soluble fraction of yeast and they are usually Saccharomyes cerevisiae.
In this post, we will explore how yeast biomass, is used to create and enhance umami flavour in human and pet food. We will examine the mechanisms behind umami flavour production, the processes involved in biomass extraction, and the specific uses of these yeast species.
What is Umami?
Umami, derived from the Japanese word meaning “pleasant savoury taste,” is often associated with the flavour of glutamate, inosinate, and guanylate—compounds naturally found in certain foods like meats, fish, seaweed, mushrooms, and fermented products. The umami taste is a result of the presence of free amino acids such as glutamic acid and nucleotides like inosine monophosphate (IMP) and guanosine monophosphate (GMP). These compounds stimulate specific taste receptors on the tongue, producing a savoury sensation.
Umami taste, the 5th taste as it is sometimes known as is one of the critical taste sensations we as humans and as pets too truly understand (Temussi, 2012). It is a sensation that enhances the overall sensory attributes of food and stimulates the human appetite (Gao et al., 2023).
So the word “umami” came from a Japanese word (うま味) which means a “pleasant savoury taste”, “mouthfulness” or “delicious”. Monosodium glutamate (MSG) which is a chemically synthesized compound, is the most prevalent and widely consumed umami substance.
Yeast biomass has become a significant source of umami flavour because of its high protein content, which includes amino acids such as glutamic acid, as well as other flavour-enhancing compounds produced during yeast metabolism. When yeast cells undergo autolysis (self-digestion), they release free amino acids, nucleotides, and peptides that contribute to the umami taste. This makes yeast biomass a natural and sustainable alternative to synthetic flavour enhancers like monosodium glutamate (MSG).
The perception of the umami taste and sensation is the result of an intricate interaction between specialised taste receptors dedicated to umami in the taste buds and with particular compounds (Zhang et al., 2019).
From the outset, umami is a flavour characteristic of foods which often complements the perception of saltiness and sweetness/sourness. A number of peptides are known to generate flavour including the monosodium glutamate. There are many others which serve as flavour transmitters in the brain.
When it comes to yeasts though which are a form of fungi we have a partner in the food industry which offers a great deal of potential and yet remains underused in a lot of respects. Yeasts and yeast extracts have long been used in food to generate a range of delicious flavours. Yeast extract (YE) itself creates sensations of a long-lasting taste impression, of thickness and complexity. This is usually characterised as kokumi which we discuss later on and a complementary sensation to umami. The kokumi-active peptides are glutathione and γ-glutamyl dipeptides and now leucyl peptides. (Liu et al., 2024).
Yeast Biomass in flavour enhancement
1. Saccharomyces cerevisiae (Baker’s and Brewer’s Yeast)
Saccharomyces cerevisiae is the most common yeast used for flavour enhancement in food products. During autolysis or controlled enzymatic hydrolysis, the cell walls of S. cerevisiae break down, releasing the internal contents, including amino acids, peptides, and nucleotides. These compounds contribute to the umami profile in various products. Yeast extracts derived from S. cerevisiae are often used in soups, sauces, snacks, and ready meals to impart savoury flavours.
In addition to enhancing taste, S. cerevisiae biomass is rich in B vitamins, making it an attractive ingredient for both human and pet nutrition. It is often included in pet food formulations not just for its flavour-enhancing properties but also for its nutritional value, contributing to the overall health and well-being of pets.
2. Saccharomyces pastorianus and Saccharomyces bayanus
These yeast species are primarily associated with beer brewing, where they are used in the fermentation of lagers and ciders. However, their biomass, once harvested from the brewing process, can also be utilized as a flavour enhancer in food production. Like S. cerevisiae, these yeasts can be autolyzed or hydrolyzed to release glutamates and nucleotides, enhancing umami flavour in foods.
The waste biomass from brewing processes is often dried and processed into yeast extracts, which are used as flavour enhancers in human and pet foods. This not only provides a sustainable use for brewing byproducts but also creates a natural source of umami compounds that can be incorporated into a variety of food products.
3. Candida utilis (Torula Yeast)
Candida utilis (Cyberlindnera jadinii) is a widely used species in the production of simple animal feed, single-cell protein as well as yeast extracts, especially in the food and pet food industry. It is known for its high protein content and ability to produce significant amounts of glutamic acid during fermentation, making it a valuable source of umami flavour.
Yeast extracts from C. utilis are often used in processed foods, such as snacks, meat products, and soups, to provide a savoury taste. This yeast is also used in vegetarian and vegan products to mimic the umami flavour traditionally associated with meat. In the pet food industry, C. utilis biomass is used to enhance the flavour of kibble and wet food products, making them more palatable to animals.
4. Candida milleri
Candida milleri is commonly used in the production of sourdough bread, where it interacts with lactic acid bacteria to create the unique flavour and texture of sourdough. While its primary use is in baking, the biomass of C. milleri can also be harvested and used as a flavour enhancer. When autolyzed, this yeast releases glutamates and other flavour compounds that contribute to umami taste in food.
Although C. milleri is not as widely used as other yeasts for flavour enhancement, it holds potential in niche applications, especially in the production of artisanal foods where a complex umami profile is desired.
5. Kluyveromyces lactis
Kluyveromyces lactis is a lactose-fermenting yeast commonly used in the dairy industry, particularly in the production of cheese and fermented milk products. Its biomass is rich in amino acids and peptides that contribute to umami flavour, especially in dairy-based products. K. lactis can be autolyzed to produce yeast extracts that enhance the savoury taste of cheese, sauces, and other dairy foods.
In pet food, K. lactis biomass can be used as a flavour enhancer, particularly in products that aim to replicate the taste of dairy. Its ability to contribute to umami flavour makes it a valuable ingredient in both human and animal nutrition.
6. Pichia pastoris
Pichia pastoris is a methylotrophic yeast widely used in biotechnology for the production of recombinant proteins. However, its biomass can also be used in the food industry as a source of umami flavour. Like other yeasts, P. pastoris can be autolyzed to release amino acids and nucleotides that enhance the savoury taste of food products.
P. pastoris is not as commonly used for flavour enhancement as S. cerevisiae or C. utilis, but it holds potential in specialized applications, particularly in the production of high-protein foods where a strong umami flavour is desired.
7. Brettanomyces spp.
Brettanomyces yeasts are primarily associated with the fermentation of specialty beers and wines, where they contribute to the development of complex flavours, including earthy, smoky, and fruity notes. While these yeasts are often considered spoilage organisms in the context of beer and wine production, their biomass can be used in food products to create unique flavour profiles.
The use of Brettanomyces biomass in flavour enhancement is less common than other yeast species, but it offers potential for creating complex umami flavours in gourmet food products. In the pet food industry, Brettanomyces biomass could be explored as a novel flavouring agent, especially in premium products that aim to differentiate themselves through unique taste profiles.
Yeast Extracts
The yeast extracts are usually available as concentrates from the soluble fraction of yeast following fermentation. The most likely sources are yeasts from brewing including other materials. They are also invariably described as brewers spent grain (BSG).
- Autolyzed Yeast: Yeast biomass can undergo autolysis (self-digestion) where the yeast cells break down their own cell walls, releasing intracellular contents like amino acids, peptides, and nucleotides. The result is a concentrated yeast extract that intensifies umami flavours.
- Hydrolyzed Yeast: Another method involves hydrolyzing yeast proteins using enzymes and acids, further enhancing the release of flavour compounds. This produces a potent umami-rich extract that is used as a flavour enhancer.
The main nutritional components are partly hydrolysed protein containing 35 to 40% free amino acids along with B vitamins and a few trace minerals and elements especially rare metals.
Spent brewers yeast will contribute proteins, B group vitamins, excluding B12, β-D-glucan, minerals including cobalt, and organic acids (Puligundla et al., 2020).
An interesting development is the growth of postbiotics such as Propionibacterium freudreichii which have improved the nutritional quality of spent brewer’s yeast. This type of fermentation contributes SCFAs (short-chain fatty acids and vitamin B12. The hindrance to further growth was the presence of polyphenols. .
One of the most intriguing products in our food range are fermented dry sausages. There are many different yeast species to be found on a fermented dry sausage including:-
- Debaryomyces,
- Candida,
- Trichosporon,
- Pichia,
- Rhodotorula,
- Yarrowia,
- Cryptococcus
All of these yeasts contribute some form of umami flavour.
The umami peptides from yeast are small types. They are also associated with particular amino acids and 5′-nucleotides.
Yeast extract peptides have been produced by heat treatment (Alim et al., 2019). These peptides produce beef-like aromas which are generated by Maillard reactions when reacted with other compounds. The YE peptides were reacted with various substrates such as xylose, thiamine, cysteine and xylose which created a range of volatile aromas
The peptides were separated using UF/GPC/RP-HPLC and then identified using LC-ESI-Q-TOF MS/MS and E-tongue. Heating had a significant impact on the taste profile of the yeast extracts.
Gao et al., (2024) has identified umami peptides from Saccharomyces cerevisiae using UHPLC-MS/MS and de novo sequencing. In this study, Asp 110, Thr 112, Arg 114, Arg 240, Lys 342, and Glu 264 were the key sites in ligand-receptor recognition. Hydrogen and ionic bonds were the main characteristic interactions between the umami peptides and the well-recognized receptor T1R1/T1R3.
Various umami peptides have been screened and identified. They have a mechanism of action on specific receptors T1R1/T1R3. Five peptides of interest are:-
AGVEDVY, LFEQHPEYRK, AFDVQ, GPTVEEVD, and NVVAGSDLR
Umami peptides bind to these receptors via H-bonds. Such peptides enhance the effects of 0.35% monosodium glutamate. Molecular docking studies show that peptide residues His, Arg, Tyr, Asp, Gln, Thr, Ser, and Glu primarily bound to His71, Ser107/109/148, Asp147/218, and Arg277 of T1R1 and Ser104/146, His145, Asp216, Tyr218, and Ala302 of T1R3 through hydrogen bonds.
Kokumi
Liu et al., (2014) identified 10 kokumi peptides in YE. We mentioned earlier that the best known kokumi peptides were glutathione and γ-glutamyl dipeptides. They identified five leucyl dipeptides which also had similar kokumi activity. The yeast extracts they analysed contained γ-Glu-Cys-Gly, γ-Glu-Leu, γ-Glu-Val, γ-Glu-Tyr, Leu-Lys, Leu-Gln, Leu-Ala, Leu-Glu, Leu-Thr and Ala-Leu. This study looked at kokumi taste with these peptides in a bland chicken broth.
The latter, Ala-Leu had the highest threshold concentration of 1.5 mmol/L in the chicken broth whilst Leu-Glu was the lowest was 0.3 mmol/L. They then conducted dose-response sensory tests using these peptides to find that they had a bitter taste. These leucyl dipeptides imparted a particular sensation below their bitter taste threshold. When they exceeded their threshold concentration, the kokumi sensation began to decline significantly.
Genetic Engineering
What has been described as a beef meaty peptide was produced by gene engineering in the yeast Pichia pastoris. This was an octapeptide Lys-Gly-Asp-Glu-Glu-Ser-Leu-Ala that was isolated from beef then digested by papain.
Fermentation
Fermented foods regularly contribute flavour compounds especially savoury flavours. Their major contribution has been to complement dishes by enhancing other foods (Caplice & Fitzgerald, 1999).
The US Food and Drug Administration has certified Saccharomyces cerevisiae, Kluyveromyces marxianus, and Candida utilis (Cylindnera sp.) for human consumption-generally recognized as safe (GRAS). The most commonly studied yeasts are Saccharomyces cerevisiae and Saccharomyces uvarum, which are mainly used in the brewing industry, and are also used in bread and pastry making or in the pharmaceutical industry.
Generally, YEs are obtained by autolysis of yeast cells, heat and mechanical disruption and hydrolysis assisted by exogenous enzymes, proteins, peptides, amino acids and nucleotides. The peptide which are released from the cell contents are collected then processed by spray drying, and the taste characteristics determined by the production of above active substance released from the enzymatic hydrolysis process (Tomé, 2021). Compared with monosodium glutamate (MSG), YEs have an excellent umami taste with a lower intake (Tomé, 2021).
Protein is a major component of yeast biomass, accounting for 35%–60% of yeast dry weight (Bratosin, Darjan, & Vodnar, 2021).
Source of Umami Compounds
- Glutamates and Nucleotides: Yeast cells naturally contain high levels of glutamic acid, a key amino acid responsible for the umami taste, similar to monosodium glutamate (MSG). The levels of free and total glutamate, (as glutamic acid) are between 5 and 10 %. Additionally, yeast cells are rich in nucleotides like inosinate and guanylate, which synergize with glutamates to boost the umami perception. Together, these compounds create a rich, savoury flavour that enhances the taste of food. The 5′-nucleotides which are breakdown products of nucleic acid have their own impact in flavour terms.
Production Processes for Yeast Biomass
The production of yeast biomass for use in food and flavour enhancement typically involves the fermentation of yeast cultures on suitable substrates, such as molasses, sugars, or other carbohydrates. The brewing process and bioethanol process are the two main sources of dried yeasts for further processing. A significant amount of yeast is used in its entire form as a source of single-cell protein as well as providing many other components for the food and biotechnology industry.
After fermentation, the yeast cells are harvested, often through centrifugation, and then processed through autolysis, enzymatic hydrolysis, or thermal treatments to break down the cell walls and release the internal components, including proteins, amino acids, and nucleotides.
Autolysis and mechanical disruption are common methods but largely poorly understood and uncontrolled. Enzymic hydrolysis is slowly gaining credence as the method of choice because it is more gentle.
Pretreatments are also being explored because they may generate peptide hydrolysates of different and better quality depending on the specification. An ultrasonic pretreatment was employed on Candida utilis prior to enzymatic hydrolysis using a double enzyme system (Wang et al., 2022). Based on experimental design, enzyme ratio, temperature, and pH were the most significant factors affecting the polypeptide yield and degree of hydrolysis. The optimal yield of polypeptides and degree of hydrolysis was achieved with a ratio of enzyme of alkaline protease to trypsin of 1:1.85 at a temperature of 51C and pH 10 which is very alkaline. Yields of polypeptide and degree of hydrolysis were 53% and 48% respectively. Ultrafiltration of the hydrolysate removed 57% of the polysaccharide yielding an amide rich polypeptide extract.
The resulting yeast extract can be dried into a powder or used in liquid form, depending on the application. In addition to being a rich source of umami flavour, yeast extracts are also valued for their ability to enhance the overall taste profile of foods, providing complexity and depth to flavours. This is especially important in the development of plant-based and meat-alternative products, where achieving a savoury, meaty taste without animal ingredients is a key challenge.
Applications in Human Food
In human food, yeast biomass is used extensively in processed foods, including soups, sauces, snacks, and ready meals, to provide a savoury and rich flavour. Yeast extracts are often included in plant-based products to enhance their umami profile and make them taste more like meat. Additionally, yeast biomass is used in the production of fermented foods, where it contributes to the development of complex flavours. The amount of yeast extract to be added rarely exceeds 5%w/w. On average a range of between 2 to 5% w/w is acceptable but with the skewness of the curve of taste preference towards the higher range. The level of glutamate needed for umami is always below 1% w/w which is actually below the amount required with pure MSG (Tome, 2021).
Yeast extracts are also used in the production of flavour enhancers and seasoning blends, providing a natural alternative to synthetic additives like MSG. Because of their natural origin and clean-label appeal, yeast-based flavour enhancers are becoming increasingly popular among food manufacturers.
Some of these yeast extracts are heated too to produce meaty compounds (Zhang, 2018).
Examples of Yeast-Derived Umami Products
- Nutritional Yeast: This is a deactivated yeast often used as a topping or ingredient in vegan cuisine to add a cheesy, umami-rich flavour. It’s particularly popular in vegan cheese and savoury snacks.
- Marmite and Vegemite: These popular spreads are based on yeast extracts, specifically from the brewing industry, and are well-known for their strong umami flavour profiles.
Sensory Testing
The techniques of choice from an analytical perspective have been gas chromatography-olfactometry (GC/O) coupled with both sensory analysis and partial least squares regression (PLSR). The aroma of a yeast extract is not just about umami flavours contributed by various amino acids, it is also about various breakdown products from yeast cells.
Back in 2006, Mahadevan and Farmer reported on the compounds found in different YE pastes. They picked up on a variety of sulphurous compounds, pyrazines and other fat-soluble compounds which all contributed to meaty flavours. It was apparent throughout the development of yeast pastes that flavours varied from batch to batch and even from within a batch of yeast. These were dependent on the substrates, the processing conditions especially level of heating. The higher beefy, roasted and metallic notes comes from very low concentrations of aliphatic sulphur compounds as well as furanthiols (Methven, 2012).
Lin et al., (2014) extracted aroma-active compounds from pastes of yeast extract. They used dynamic headspace extraction or simultaneous distillation extraction. The detection system was gas chromatography–olfactrometry–mass spectrometry in conjunction with dynamic headspace dilution analysis or aroma extract dilution analysis. They identified a large range of compounds from aldehydes, ketones and alcohols, pyrazines and various sulphur compounds.
Wang et al., 2019 assessed four different yeast extracts with different sensory profiles. One had a sulphurous note, another had green and fatty notes whilst another was slightly floral and the last of the group fermented, with roasted and caramel notes. I that study they identified 37 specific aroma compounds. The main types were methional which is a typical potent sulphur note and 2,4-Di-tert-butylphenol. They also identified nonanal which has a slight cardboard note as well as off-flavours too. These include p-cresol and indole which are identified as yeast notes. Indole is breakdown product from amino-acids and some vitamins. A number of aldehydes and ketones have been isolated too.
Applications in Pet Food
In the pet food industry, yeast biomass is used to improve the palatability of kibble and wet food products. The savoury taste of umami is appealing to both cats and dogs, making yeast extracts a valuable ingredient in pet food formulations. In addition to enhancing flavour, yeast biomass provides nutritional benefits, such as B vitamins, amino acids, and minerals, which contribute to the overall health of pets.
Yeast-based flavour enhancers are particularly important in premium and specialty pet foods, where manufacturers seek to create highly palatable products without relying on artificial additives. Yeast extracts can also be used in grain-free and hypoallergenic pet foods, where they provide a natural and digestible source of flavour.
Yeast biomass plays a critical role in the enhancement of umami flavour in both human and pet foods. These yeasts contribute to the savoury, meaty taste associated with umami through the release of amino acids, peptides, and nucleotides during autolysis or hydrolysis.
In human food, yeast biomass is used in a wide range of products, from soups and sauces to plant-based meats, where it provides a natural source of flavour. In pet food, yeast extracts improve the palatability of kibble and wet foods, making them more appealing to animals while also offering nutritional benefits.
As consumer demand for natural and sustainable ingredients continues to grow, the use of yeast biomass for flavour enhancement is likely to expand, providing new opportunities for innovation in the food and pet food industries.
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