Keith H. Steinkraus

Classification of fermented foods: worldwide review of household fermentation techniques

Abstract Fermented foods are of great significance because they provide and preserve vast quantities of nutritious foods in a wide diversity of flavors, aromas and textures which enrich the human diet. Fermented foods have been with us since humans arrived on Earth. They will be with us far into the future as they are the source of alcoholic foods/beverages, vinegar, pickled vegetables, sausages, cheeses, yogurts, vegetable protein amino acid/peptide sauces and pastes with meat-like flavors, leavened and sour-dough breads. While the Western world can afford to enrich its foods with synthetic vitamins, the developing world must rely upon biological enrichment for its vitamins and essential amino acids. The affluent Western world cans and freezes much of its foods but the developing world must rely upon fermentation and dehydration to preserve its foods at costs within the budgets of the average consumer. All consumers today have a considerable portion of their nutritional needs met through fermented foods and beverages. This is likely to expand in the twenty-first century when world population reaches 8–12 billion.

Nutritional significance of fermented foods

Abstract Fermented foods are of great significance because they provide and preserve vast quantities of nutritious food in a wide diversity of flavours, aromas and textures which enrich the human diet. Fermented foods have been with us since humans arrived on earth. They will be with us far into the future as they are the source of alcoholic foods/beverages, vinegar, pickled vegetables, sausages, cheeses, yogurts, vegetable protein amino acid/peptide sauces and pastes with meat-like flavours, and leavened and sour-dough breads. While the Western world can afford to enrich its foods with synthetic vitamins, the developing world must rely upon biological enrichment for its vitamins and essential amino acids. The affluent Western world cans and freezes much of its food but the developing world must rely upon fermentation and dehydration to preserve and process its foods at costs within the budget of the average consumer. All consumers today have a considerable portion of their nutritional needs met through fermented foods and beverages. This is likely to expand in the 21st century when world population reaches 8–12 billion (10 9 ).

Lactic acid fermentation in the production of foods from vegetables, cereals and legumes

Lactic acid bacteria perform an essential role in the preservation and production of wholesome foods. Generally the lactic acid fermentations are low-cost and often little or no heat is required in their preparation. Thus, they are fuelefficient. Lactic acid fermented foods have an important role in feeding the worlds population on every continent today. As world population rises, lactic acid fermentation is expected to become even more important in preserving fresh vegetables, fruits, cereals and legumes for feeding humanity.

Bio-enrichment: production of vitamins in fermented foods

Less than a hundred years ago, vitamin deficiency diseases were common in the United States. Unfortunately hundreds of millions of people still suffer from a variety of vitamin-deficiency diseases in the developing world. Each year millions of children become permanently blind via xerophthalmia caused by a lack of vitamin A in the diet. Surrounded by quantities of green and leafy vegetables, no child should be lacking vitamin A and have to suffer life-time blindness. Lack of proper nutrition education is the problem.

Fermented foods, feeds and beverages

World population reached 5 billion people in 1986 and is expected to rise to 6 particularly severe in parts of Africa, particularly Ethiopia. Hunger and malnutrition accompany the poverty that is characteristic of the masses of the people in the developing world. Even in the United States, one of the most affluent countries, there has been a considerable increase in the number of homeless people including mothers and children living in the streets or in substandard housing. The indigenous fermented foods and beverages already consumed for centuries by hundreds of millions of the worlds masses can be used in many cases to improve and extend the worlds food and nutrition supply at a relatively low cost. Fermented foods, feeds and beverages are getting ever increasing attention particularly in the developing world and also in the developed world. This paper summarizes activities and advances related to fermented foods, feeds, and beverages over the past several years.

Factors Influencing the Fermentation of Honey in Mead Production

SUMMARYAttempts were made to produce a good-flavoured mead by more rapid fermentation than is usual. Several wine yeasts were tested, and additives of two types, I composed mainly of inorganic salts and citric acid, and II with a wide spectrum of vitamins and small amounts of organic and inorganic nitrogen compounds.Honeys varied in their fermentability, in general light honeys being more difficult to ferment than dark honeys. But addition of growth factors allowed all honeys tested to be fermented rapidly, yielding characteristic meads which had none of the unpleasant flavour associated with long (unaided) fermentation.A recommended procedure is described, which uses additives I + II and can give a dry or sweet mead (alcohol content 12% or 14–15%). Fermentation takes about 2 weeks without agitation. The production of mead champagne and mead sherry is also described.

The Potential of Microbial Cells As Protein for Man

Mans basic foods consist of plant cells and their storage products (i.e., seeds, leaves, and roots), animal cells (meats), and animal products (milk and eggs). Historically, consumption of microbial cells per se by man has been largely limited to mushrooms and to certain forms of algae such as Spirulina and Scenedesmus in parts of Africa and Mexico. In recent years people in certain countries (e.g., Taiwan) have incorporated relatively small amounts of dried yeast cells and extracted algae cells into their diets. However, microbial cells grown en masse could be consumed in some form directly by man as a major protein source in the diet (see Waslien 1975 for detailed review). And they can be fed to animals, thus releasing for human consumption the cereal grains and legumes now fed to animals. As shown in Table 1, the crude protein content ranges from 8 to 64% for pure cultures of algae cells, 15-75% for yeasts, and 50-84% for bacteria. Chemical scores of the protein can be as high as 71 for Spirulina and Scenedesmus algae, 88 for brewers yeast, 93 for the food yeasts (Torulopsis utilis), and 71 for the bacterium Hydrogenomonas eutropha. The median chemical score for the protein ranges from 54 for bacteria to 61 for yeasts, compared with chemical scores of 100 for eggs and 94 for milk (Waslien 1975). As with soybean protein, methionine and cystine are the first limiting amino acids in microbial cells; thus, they too might serve as suitable protein sources for man.

Factors influencing permeability of the cell membrane of the osmotolerant yeast Saccharomyces rouxii grown in the presence and absence of 18% NaCl. I. Na+/K+-activated Mg2+-dependent ATPase

Abstract It was found that cells of Saccharomyces rouxii contain an ouabain-inhibited ATPase, assumed to be an Na+/K+-activated Mg2+-dependent ATPase, which could serve as a sodium pump protecting the cells in a high salt environment. Twenty-two cell homogenates or supernatants (centrifuged at 3000 × g) grown without added salt in the medium contained sufficient total ATPase activity to liberate (on average) 0.225 μM Pi min−1 mg−1 protein. The percentage of total ATPase inhibited by the addition of ouabain (1 × 10−4 M) varied from 7 to 100%. Cell homogenates or supernatants from cells grown in the presence of 18% NaCl in the media contained sufficient ATPase activity to liberate (on average) 0.114 μM Pi min−1 mg−1 protein, about 50% of the total ATPase activity found in the non-salt grown cells. The percentage of total ATPase activity inhibited by ouabain ranged from 16 to 100%. Although the non-salt-grown cells contained approximately double the total ATPase activity of the salt-grown cells. there was evidence that the percentage of total ATPase that is ouabain sensitive (Na+/K+-activated ATPase) is higher in the salt-grown cells. Also, cells of S. rouxii grown in media without added NaCl, recovered by centrifugation and transferred to media containing 18% NaCl for 16 h and again recovered by centrifugation, homogenized and centrifuged at 10 000 × g contained 61.2% ouabain-sensitive ATPase compared with 21.3% ouabain-sensitive ATPase in the cells before adaptation to the high salt environment.

Chemical Analysis of Honey Wines

SummaryEleven commercial honey wines and meads were analysed, with the following results: alcohol 12·2–20·8% vol/vol; pH 2·90–3·75 (very tart to mild acidity); total titratable acids (as tartaric) 0·220–0·708 g/100 ml; volatile acid (as acetic) 0·014–0·0779 g/100 ml, acetaldehyde 18·2–125·5 mg/litre, reducing sugars (as dextrose) 2·5–27·8%; most of the commercial meads were quite sweet.Ash content and percentage of certain cations in the ash were also determined; these results indicated the nature of the fermentation and the type of salts added during the process. Mead made by the Cornell University rapid-fermentation process was less sweet than most commercial wines, and free from any off-flavour.

Characterization of the semi-purified membrane bound ATPases of Zygosaccharomyces rouxii adapted to 18% NaCl

The yeast (Zygosaccharomyces rouxii) contains a plasma membrane ATPase which exhibits some properties similar to those of the Na+/K+-activated Mg2+-dependent ATPases hitherto reported as existing almost exclusively in animal systems. Cells of Z. rouxii grown under low salt conditions and adapted to media containing 18% NaCl have Mg2+-dependent ATPase activity which is optimum at PH 6.0 and is inhibited by ouabain (10−4 M) in the presence of NaCl and KCl, inhibited by sodium orthovanadate and virtually unaffected by oligomycin. When run through sodium dodecylsulfate (SDS) polyacrylamide gel electrophoresis (PAGE), the enzyme appears to contain a subunit ranging from 70000 to 100000 daltons. The mean specific activity (x) from the P6 semipurified membrane fraction of cells grown without added salt was 0.48 μM Pi·mg−1 protein·min− with a batch mean standard error of 0.12. The mean specific activity of similar fractions from 18% NaCl adapted cells was 0.78 μM Pi·mg−1 protein·min−1 with a batch mean standard error of 0.07. It was demonstrated that the enzyme had significant specificity for ATP and had significant dependence upon Mg2+. As much as 75.3% of enzyme activity was inhibited by sodium orthovanadate, a known inhibitor of plasma membrane ATPase. Oligomycin, an inhibitor of mitochondrial ATPase activity, inhibited a maximum of 10.3% of the activity suggesting some mitochondrial contamination. Ouabain (1.6×10−4 M) in the presence of NaCl and KCl (23 mM) showed a significant inhibition of the membrane ATPase activity in one half the cells adapted to 18% NaCl while producing apparent enhancement of ATPase activity in cells grown without salt. The ATPase activity of cells adapted to 18% NaCl was significantly higher than that of cells unexposed to high salt.