Acta Alimentaria, Vol. 38 (Suppl.), pp. 71–85 (2009) DOI: 10.1556/AAlim.38.Suppl.5 0139-3006/$ 20.00  2009 Akadémiai Kiadó, Budapest BIOCHEMICAL PRINCIPLES OF THE USE OF YEAST BIOMASS AND LAB STARTER CULTURES IN FOOD PRODUCTION A. HALÁSZ* and ZS.ZALÁN Unit of Biology, Department of Food Safety, Central Food Research Institute, H-1022 Budapest, Herman O. út 15. Hungary 1. Yeast biomass During the last 40 years considerable interest has been shown in the production of food proteins by microorganisms: bacteria, yeast, fungi and algae. Microorganisms are technologically attractive mainly because they offer the promise of increased food productions without reliance on traditional agricultural methods. Important features of the production of these unconventional proteins (single cell proteins or SCP) are that they are produced under controlled factory conditions, which require very limited space, they are not dependent upon atmospheric conditions and they spare marine fauna and other natural sources. The microorganisms involved continuously propagate in large fermentation vessels and will grow on many different substrates, among others on by- products of the food industry. Among the other potential sources of SCP for human nutrition yeast protein seems to be the most suitable. In human experiments CALLOWEY (1976) showed that diets containing yeast as the only protein source resulted in a slightly higher level of faecal nitrogen than the control diet of casein, but the difference was not statistically significant. About 8–9 g yeast nitrogen was adequate to maintain the balance in healthy male subjects. Among the advantages to use yeast (yeast protein) the long tradition of yeast production has to be mentioned and commercially well developed, economically applicable technologies are available. In many cases (e.g. breweries) large volume of * To whom correspondence should be addressed. Phone: +36 1 355 8244/614; fax: +36 1 225 3342; e-mail: a.halasz@cfri.hu