Use of Yeast Biomass in Food Production

Anna Halasz, Radomir Lasztity

• Editore: CRC Press
• Anno: 2017
• ISBN:
  9781351405911
• Edizione: 1
• Argomento: Tecnologia e ingegneria
• Categoria: Scienze dell'alimentazione

Yeast biomass is an excellent source of proteins, nucleic acids, and vitamins. It has been produced and consumed in baked goods and other foods for thousands of years and offers significant advantages when compared to other potential new microbial protein sources. Use of Yeast Biomass in Food Production provides up-to-date information regarding the chemical composition and biochemistry of yeasts, discusses the biotechnological basis of yeast production and possibilities for influencing yeast biomass composition using new techniques in molecular biology. The book examines techniques for producing yeast protein concentrates (and isolates) while still retaining their functional properties and nutritive values, as well as the various uses for these materials and their derivatives in different branches of the food industry. Finally, the book explores possibilities for the production and industrial use of other yeast components, such as nucleic acids, nucleotides, cell wall polysaccharides, autolysates, and extracts. Food microbiologists and technologists, as well as biotechnologists, will discover that this book is an invaluable reference resource.

PART I

1
Introdution

In writing about the potential use of yeast biomass in food production we are thinking about yeasts first as a protein source. The proteins have long been recognized as both quantitatively important and nutritionally vital components of foods. In the last decades substantial interest has been shown in their contribution to food attributes such as texture and behavior in processing and use and thus, ultimately to food acceptability. Keeping in mind the facts mentioned above, it is quite understandable that few subjects in the field of food science and technology have attracted as much active interest in recent years as proteins.

Since the beginning of agricultural production in prehistoric time, the cereals (wheat, rice, corn, rye, barley, sorghum, millet, etc.) were the main agricultural products in most parts of the world playing an important role in the nutrition generally and also in the protein supply. Although amino acid composition of the cereal proteins and the role of essential amino acids were not known, the mixed diet containing different proteins was characteristic of the greatest part of the population allowing a compensation of the effects of the unsatisfactory content of some essential amino acids in cereal proteins. Later, the steady growth of population and the limited increase of agricultural production (especially animal husbandry) changed this situation. In many countries the mixed protein diet changed to a diet based on the overwhelming consumption of cereals resp. cereal products representing 50 to 90% of the total energy and protein supply. The low content of cereal proteins in some essential amino acids combined in many cases with shortage of food leads to a protein resp.essential amino acid deficiency in a lot of countries belonging to the group of developing countries.

As it is known, the major function of proteins is to provide the body with an adequate intake and balance of essential amino acids and nitrogen for the synthesis of other (nonessential) amino acids. The essential amino acids are used for the maintenance of the body, tissue protein synthesis in adults and for net protein gain during growth and development. The daily protein requirements for adult men and women, for infants aged 0 to 6 months and children aged 10 to 12 years are indicated in Table 1. The values included in Table 1 are recommended by the Food and Agriculture Organization (FAO) and World Health Organization (WHO) as “safe protein intakes” for healthy people.¹ Adults require less protein per kilogram than children, since protein turnover decreases with age and growth stops.

Protein (resp. essential amino acid) requirements are influenced by caloric intake. The total amount of energy supplied by a range of foods in the diet, however, determines not only the quantity of the protein in the diet but also its effective utilization.

If the caloric intake is insufficient, a part of the dietary protein is used for the energy production. Results of studies of both children and adults indicate clearly that protein metabolism is very sensitive to energy intake. So it is understandable that various interactions among dietary protein, total energy intake and the proportion of energy derived from non-protein energy sources such as carbohydrate and fats, have important implications for the quantitative estimation of human protein and amino acid requirements.

The recommended quantity of proteins for adults is somewhat controversial. In the framework of studies in developing countries, some adults have been found to remain in nitrogen equilibrium when given a rice protein intake as low as 0.44 g/day/kg.² This may be possible because of metabolic adaptation to habitually low protein intakes. Nevertheless, many countries recommend protein intakes higher than those advocated by FAO/WHO. These recommendations are usually 1 g/kg/day and are based on observations that young men fed amounts of egg protein, just sufficient to maintain nitrogen equilibrium, over extended periods of time undergo some biochemical abnormalities. The value finally agreed upon is of great importance since it will influence the level of concern directed to the “protein gap” of developing countries, the planning goals for national food supplies, the dietary standards for assistance programs, the information contained in nutrition education programs, how data from food consumption surveys are interpreted, the requirements for nutrition labeling and so on.³

Table 1 Human Requirements for Essential Amino Acids and Provisional Amino Acid Patterns for Ideal Proteins

Amino acid	Infant requirement (0—6 months; mg/day per kg)	Child requirement (10—12 years; mg/day per kg)	Adult requirement (mg/day per kg)	Provisional ideal pattern (adult; mg/g protein)
Histidine	28	0	0	0
Isoleucine	70	30	10	18
Leucine	161	45	14	25
Lysine	103	60	12	22
Methionine (+ cysteine)^a	58	27	13	24
Phenylalanine (+ tyrosine)^b	125	27	14	25
Threonine	87	35	7	13
Tryptophan	17	4	3.5	6.5
Valine	93	33	10	18
Total essential amino acids	742	261	83.5	151.5
Total protein requirement (egg or milk proteins)	2000	800	550 570:man 520:woman

^a Cysteine may supply up to one third the need for total sulfur amino acids.

^b Tyrosine may supply up to one third the need for total aromatic amino acids.

From FAO/WHO Energy and Protein Requirements, Report of a joint FAO/WHO ad hoc Expert Committee, World Flealth Organization Techn. Rep. Ser.

To meet the protein requirements of humans not only the quantity of proteins is important, but also the essential amino acid content. The nutritive value of protein (protein quality) depends on the kinds a...