Mycoproteins, marketed in some foreign countries under the name Quorn, is essentially the mycelium of Fusarium graminerarum grown in continuous culture in a medium containing glucose, ammonium salts and a few growth factors. It is essential to reduce the level of RNA which is about 10% on mycelial dry weight to below the levels likely to lead to kidney- stone formation or gout. This can be achieved by mild heating prior to filtration which activates the RNAses and leads to RNA reduction. Such products contains 44% of protein and is high in 'fiber' contents.
Tempeh: This is fermented food of Indonesians. The most popular type is produced from soybeans and also called as tempeh kedle. Whole clean soybeans are soaked overnight in water to hydrate the beans. A bacterial fermentation occurs decreasing pH to 4.5-5.3. The beans are dehulled and the moist cotyledons cooked resulting pasteurization of the substrate. It destroys the trypsin inhibitor and lectins contained in the beans. After cooking, the beans are drained and spread on to bamboo trays for cooling.
The fermentation is carried out by mixed culture of molds, yeasts and bacteria but most important component appears to be Rhizopus oligosporus. After 48h incubation at 33-35Â°C, the mycelium develops, pH rises to around 7, fungal protease increase the free acid content of the product and lipases hydrolyse over to neutral fat present to free fatty acids. Fresh tempeh has a nutty odour and flavor which can be consumed after frying in oil. Except thiamine, other vitamins increase to varying degree during fermentations. Tempeh is the important source of B12 for people subsisting on a largely vegetarian diets.
Tempeh has been stopped from 1988 due to food poisoning by Pseudomonas growing in the product and elaborating the toxious acid production.
Soy sauce: This is a representative of product which have mold activity in two stage fermentation process.
Koji stage: The production of the soy sauce involved two stage fermentation process. The mould starter used is often called koji. In case aerobic conditions allow molds to grow on the substrate producing a range of hydrolytic enzymes. The soybeans are mixed with roasted wheat in equal proportions and inoculated with seed koji. i.e. a mixture of substrate and strains Aspergillus oryzae. The moulds are grown about 5 cm deep for 2-3 days at 25-35Â°C.
Moromi stage: Moromi stage is a mash process in which conditions are made so as not to allow moulds to grow. In soy sauce production this is obtained by mixing koji with an equal volume of brine to give a final salt concenteration of 17-20%. The yeasts and lactobacilli dominate the microflora produced by a number of flavoured compounds and convert half of the soluble sugars to lactic acid (2-3%) and ethanol (1%). The halophiles lactic acid bacterium Tetragenococcus halophilus and the yeasts Zygosaccharomyces rouxi and Torulophilus etc. have been identified as being important organisms. This stage lasts up to a year or more at the end of which the mash is filtered to remove the solid residues which may then be mixed with brine to undergo a second fermentation and produce a lower grade product. After pasteurization, filtration and maturation the product is bottled.
Miso: Molds are involved in the preparation of most of the oriental foods. Miso is prepared by the starter termed koji and chou molds serve the source of enzymes. In this case Aspergillus oryzae is used to ferment steamed polished rice in shallow trays at 35Â°C. The koji is mixed with a mash of crushed and steamed soybeans to which salt is added. The fermentation is now allowed for about 6-7 days at 28Â°C and 60 days at 35Â°C. Finally it is ground to form a paste which is used with other foods.
Natto: It is soybean made product. The soybeans are wrapped in rice straw and fermented for 1-2 days. The package becomes slimy on the outsides. The microbe involved Bacillus natto, grows in natto, release trypsin like enzymes responsible for ripening process.
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