LESSON 9 Flashcards
Biotechnology definition
An umbrella term that covers a broad spectrum of tools and techniques, ranging from fermentation (bread, wine, cheese) to plant and animal breeding, cell and tissue culture, antibiotic production and genetic engineering.
Fermented foods definition
The foods which have been produced with the aid of microorganisms
Principle of preservation by fermentation
Encouragement of growth and metabolism of alcohol and acid-producing microorganisms to suppress the growth and metabolic activities of proteolytic and lipolytic, spoilage-causing microorganisms. This condition forms the basis of microbial antagonism that is the principle of preservation of foods by microorganisms specifically cultured for the production of fermented foods. Microorganisms, when cultured in foods, produce a variety of end products including acids and alcohols which act as antimicrobial agents.
Benefits of Fermentation
Fermented foods in many cases can be more nutritious than the unfermented original materials, add variety to our food supply, which adds to our diet a group of nutritious products,
Factors Affecting Fermentation in Foods
Starter cultures, Formation of Metabolites ( e.g Acids, Alcohol), Temperature, Oxygen and Salt.
Starter cultures
Modern food fermentation (biotechnology) employs the use of microbial cultures specifically selected and maintained for desirable trait(s): e.g.acid production; alcohol production; production of flavour compounds; production of specific enzymes; rate of growth. In current food fermentation practices, the starter cultures are grown under specific conditions and the harvested cells are added in a specific proportion to the food to be fermented. Cultures may be grown within the food processing plant or may be purchased as frozen or dehydrated cultures.
Formation of Metabolites
Metabolites are products resulted from metabolism by the organism. In fermentation, the desired microorganisms or more specifically the starter culture is grown to produce the desired metabolites. These compounds vary depending on the type and condition of growth of the microorganisms. The most common metabolites are acids and alcohols.
Acids
Foods can be preserved by the addition of acids to lower the pH or by the encouragement of growth of acid-producing microorganisms used in food fermentations. Milk and meat are treated in such a manner that the lactic acid-producing bacteria, added as a starter culture, will grow rapidly and produce lactic acid in sufficient quantities to suppress growth and metabolism of spoilage and disease-causing microorganisms. Cheese, yogurt, and fermented sausages must be stored under refrigeration with or without vacuum packaging to delay growth of the acid-tolerant psychrotrophic yeasts and moulds.
Alcohol
Alcohol, like acid, in sufficient concentrations functions as a preservative. Alcohol in wines and beer is not of sufficient concentration to inhibit growth of ethanol-oxidizing bacteria. Wines and beer must be further processed by pasteurization or filtration through membranes with pore diameters smaller than the spoilage-causing microorganisms. Fortified wines with alcohol contents above 20% do not require further preservation treatments.
Oxygen
Oxygen may be desirable or undesirable in fermentation processes. Microorganisms used in fermentation processes have different oxygen requirements for growth and fermentation activity.
Rennet
The combination of acid and rennet causes the caseins to coagulate and form a gel very much like that found in a carton of yogurt. The commercial rennin preparation is known as “rennet”, which is obtained from the 4th stomach of the calf and contains rennin and other small amounts of other materials. Rennin (also called chymosin) is a pure enzyme.
CHEESE PRODUCTION 9.3
9.3
Chymosin
Microbially produced bovine chymosin is an approved food additive in Canada. Chymosin is the principle milk-clotting enzyme in bovine rennet extracts that have traditionally been used in cheese making.
Goals of genetically engineered starter culture research
Microbially produced bovine chymosin is an approved food additive in Canada. Chymosin is the principle milk-clotting enzyme in bovine rennet extracts that have traditionally been used in cheese making.
Preservation of food by biotechnology involves the use of…
.. live microorganisms to produce desirable changes in the food, including acids, alcohols and other (antimicrobial) substances that inhibit the growth of other microorganisms (microbial antagonism)
Food fermentation can be caused by …
.. bacteria, yeast, and mould
