Yeast has been part of our diet and used for its nutritional attributes for centuries and it is more and more recognised for its natural benefits and image. Some people take inactive yeast on a daily basis, one tablespoon mixed with salads, soups, pasta, juice, etc.
Because of its naturally rich B vitamins content, notably riboflavin, folic acid, and niacin, it is often recommended to stimulate appetite and milk production during lactation. It is also used by athletes and the elderly that need to supplement their nutrient intake to increase their energy level.
The precise nutritional content of yeast products can vary with manufacturer and fermentation substrates, but in general they can contribute significant amounts of nutrients, including high quality proteins, fibres and highly bioavailable B vitamins and minerals.
Its pleasant nutty-cheesy flavour and rich nutritional content explains why it is frequently used to in vegetarian food products, for direct consumption and for the formulation of dietary supplements. Protein-rich extracts obtained from yeast are more and more utilised to enhance flavours and lower sodium content of food preparations.
Nutrients To Look For In Yeast
Yeast contains significant amounts of proteins which comprise all of the essential amino acids, including a significant amount of leucine, a branched-chain amino acid. They have a relatively good digestibility level (83 percent in vitro), which explains their protein digestibility-corrected amino acid score of 86 percent. These key characteristics are essential to stimulate muscle protein synthesis.
Nutritional yeast made from primary yeast (Baker’s yeast) contains significant amount of beta-glucans. Compared to spent yeast obtained from alcohol fermentation (Brewer’s yeast), primary yeast strain of Saccharomyces cerevisiae has a higher beta-glucan-to-alpha-mannan ratio and is therefore a better source of beta-glucans.
The yeast beta-glucans located in the cell wall, are branch-on-branch polysaccharide molecules containing linear (1,3)-beta-glucosyl chains that are joined through (1,6)-linkages. This structure provides yeast with several properties useful for food and dietary supplement applications.
Yeast beta-glucans can also play a role in human health by helping strengthening the immune system. They have the ability to trigger the non-specific-innate immune response, including phagocytosis and production of pro-inflammatory factors. This mechanism can lead to the elimination of infectious agents.
Nutritional yeast is naturally rich in B-complex vitamins (pantothenic acid, thiamin, folate) and in minerals (zinc and potassium). However yeast can also be produced with the objective of converting and/or enhancing these natural endogenous micronutrients.
Depending on process and fermentation media formulations, nutritional yeast products will have different nutritional profiles—some contain only naturally-occurring micronutrients (thiamin, riboflavin, pantothenic acid, folate, zinc), whereas others are fortified in order to further increase their concentration in B vitamins and in minerals of interest to attain more measurable levels.
In any case, the gentle processing conditions aim at preserving the yeast’s natural beneficial nutrients and ensure the yeasts’ dosage of essential micronutrients, so nutritional yeast can contribute significant amounts of bioavailable micronutrients essential for optimal nutrition.
Compared to pure forms of minerals and B vitamins, those found in yeast have been shown to be absorbed more slowly in animals and man and more bioavailable. With its naturally rich and bioavailable mineral and B-vitamin content organic nutritional yeast is a perfect ingredient for the manufacturing of vegetarian and vegan food products.
Yeast Savoury Properties
Apart from these nutritional attributes, inactive yeast has the ability to elongate taste sensation and to smooth off top notes in seasonings. It is commonly used to improve flavour in processed cheese and meat analogues. Yeast can also be used for the production of yeast extract. This naturally protein-rich and flavourful water-soluble yeast extract is loaded with L-glutamic acid and nucleotides, flavour-enhancing compounds which provides an umami (savoury) and kokumi (heartiness) tastes to food.
Glutamic acid is a natural compound found in many fermented or aged foods, including soy sauce, fermented bean paste, and cheese, and is also a component of hydrolysed protein such as yeast extract. Glutamic acid stimulates specific receptors located in taste buds which induce the taste known as umami, one of the five basic tastes also referred to as 'savoury' or 'meaty'.
The 5’-nucleotides (5’-inosine monophosphate and guanosine monophosphate) found in yeast and yeast extract are other important flavour compounds. They enhance and impart umami flavour sensations in order to bring out taste and round off sharp notes. These 5’-nucleotides also have a synergistic effect with certain amino acids such as glutamic acid (flavour enhancer) and aspartic acid and phenylalanine (starter material for peptide sweetener).
According to a study by Baryłko-Pikielna and Kostyra in 2007, the contribution of glutamic acid, 5’-inosine monophosphate and 5’-guanosine monophosphate to food palatability-enhancement can vary. In chicken broth and vegetable soup, glutamic acid plays the leading role. In mushroom, red beets and asparagus soups, the contribution of 5’-inosine monophosphate and 5’-guanosine monophosphate is more considerable.
It is generally recognised that the umami substances are effective flavour enhancers in savoury foods, such as meat, fish, seafood, vegetable foods and mixed products of above raw materials—but they remain ineffective in sweet, fruity or bland foods.
The unique taste properties of yeast extract makes it especially useful for savoury flavour enhancement in a great variety of applications from soups, sauces, snacks and seasonings to vegetarian food and also meat products. Yeast extracts that vary in taste profiles can also be used to help reduce sodium content of cheese and dairy, meat, poultry, sauces and dips, vegetable and snack preparations.
Yeast is considered an agricultural product in the organic regulation in the EU since 31 December 2013 and thus, has to be taken into account in organic recipes. Whether used in soups, sauces, vegetarian foods, meat products or for seasoning, organic yeast and yeast extract products can therefore help improve food texture and bring out the savoury flavours of these organic certified foods.