Inactivated biomass from yeasts and fungi can be processed into a variety of different valuable products serving as ingredients for animal and human consumption. Due to their nucleic acid content and cell wall compounds which may cause undesirable effects, the main strategies entail cell lysis and extraction of the components, mainly proteins, and separation and concentration for the production of concentrates and isolates. These can be used directly (e.g., Beldem produces inactive yeast for use in animal feed) or processed in order to get extracts, autolysates, and protein hydrolysates of specific functional properties.
Use of yeast protein concentrates and isolates in food processing is recommended in many scientific papers due to their favorable nutritional properties. However, due to the relative high cost of protein isolate production the use of these formulations is limited to meat products, meat, and milk substitutes.
Yeast and fungi autolysates and hydrolysates are obtained by hydrolysis of the proteic fraction. These can be used as natural flavors under the definition of the FDA and Code of
Federal Regulations (21 CFR 101.22(3)) and to improve the physical properties (texture, emulsifying properties) and nutritional value of food products (Halasz and Lasztity 1991). Thus, yeast autolysates and hydrolysates are used as flavor enhancers in sausage, meat, and cheese manufacture (Halasz and Lasztity 1991). Examples of these applications are: the production of Aspergillus oryzae extracts by Diamond V, used as a livestock feed, the autolyzed yeast flavor ingredients, Provesta® flavors from torula yeast, and Ohly® yeast extracts manufactured by Burns Philp (http://www. bpfoods.com) for use in different food systems, sauces, soups, marinades, and many other food types. Lallemand Inc, Lesaffre group, and Beldem also produce a complete range of yeast extracts for animal feed and as flavor enhancers for application in animal and human nutrition. At this moment, the studies are mainly focused on new developments and more tailored protein formulations whose acceptance by the consumer will depend on their functional characteristics.
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