fermentation.pdf

1 2 3 However, scientists and policy makers have neglected this area, particularly traditional fermented products from developing countries. 4...have been prepared and consumed for thousands of years and are strongly...

1 2 3 However, scientists and policy makers have neglected this area, particularly traditional fermented products from developing countries. 4...have been prepared and consumed for thousands of years and are strongly linked to culture and tradition, especially in rural households and village communities. 5 There is reliable information that fermented drinks were being produced over 7,000 years ago in Babylon (now Iraq), 5,000 years ago in Egypt, 4,000 years ago in Mexico and 3,500 years ago in Sudan (Dirar, 1993), (Pedersen, 1979). 6... make a significant contribution to the diet of millions of individuals. 7 For instance... Over one billion litres are produced each year in Japan alone. 8 "Gundruk" which is a fermented and dried vegetable product is very important for ensuring food security for many Nepali communities especially in remote areas. It is served as a side dish with the main meal and is also used as an appetiser in the bland, starchy diet. The annual production of gundruk in Nepal is estimated at 2,000 tons. 9 10 There is tremendous scope and potential for the use of microorganisms towards meeting the growing world demand for food, through efficient utilisation of available natural food and feed stocks and the transformation of waste materials. 11 Description of terms used in food processing. 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Description of terms used in food processing. 28 Description of terms used in food processing. 29 Description of terms used in food processing. 30 Description of terms used in food processing. 31 Microorganisms contain certain enzymes, such as cellulases, which are incapable of being synthesised by humans. 32 Pulque (a fermented fruit sap) is felt to have medicinal properties in Mexico. 33 Lastly, Fermentation can improve the flavor and appearance of food. One important area is the creation of meat-like flavour. 34 Several more fermented fruit and vegetable products arise from lactic acid fermentation and are extremely important in meeting the nutritional requirements of a large proportion of the worlds population. 35 The most common groups of micro-organisms involved in food fermentations are: 36 Lactobacillus species which have the ability to produce lactic acid from carbohydrates. 37 Other important bacteria, especially in the fermentation of fruits and vegetables, are the acetic acid producing acetobacter species. 38 Yeasts play an important role in the food industry as they produce enzymes that favour desirable chemical reactions such as the leavening of bread and the production of alcohol and invert sugar. 39 Moulds are also important organisms in the food industry, both as spoilers and preservers of foods. Certain moulds produce undesirable toxins and contribute to the spoilage of foods. 40 41 It is essential with any fermentation to ensure that only the desired bacteria, yeasts or moulds start to multiply and grow on the substrate. 42 There are six major factors that influence the growth and activity of micro-organisms in foods. These are... 43 44 chromogenic – producing pigments 45 Most yeasts require an abundance of oxygen for growth, therefore by controlling the supply of oxygen. In addition to oxygen, they require a basic substrate such as sugar (40%). 46 Some yeasts can ferment sugars to alcohol and carbon dioxide in the absence of air but require oxygen for growth. They produce ethyl alcohol and carbon dioxide from simple sugars such as glucose and fructose. 47 Normal yeasts require a minimum water activity of 0.85. 48 Factors which are most important to control are: - Excessive clarification removes many of the natural yeasts and flora. 49 - Sugar can be added to fruit juices with a low sugar content, to increase the amount of fermentable substrate. 50 Other micro-organisms have the potential to influence wine production at all stages of the process. Fungicides are used in an attempt to control their growth, but these disturb the natural balance of flora, thus making it difficult to carry out a ‘natural’ fermentation. During storage, wines are prone to non-desirable microbial changes. 51 The major products of yeast fermentation are alcoholic drinks and bread. 52 Bacteria are "a large group of unicellular or multi-cellular organisms lacking chlorophyll, with a simple nucleus, multiplying rapidly by simple fission, some species developing a highly resistant resting (spore) phase; some species reproduce sexually, and some are motile. In shape they are spherical, rodlike, spiral, or filamentous. 53... which produce lactic acid as the major end product of the fermentation of carbohydrates. 54 Historically, bacteria from the genera... are the main species involved. 55 They are the most important bacteria responsible for the fermentation of : 56 The same reaction also occurs in wines, oxygen permitting, where the acetobacter can cause undesirable changes – the oxidation of alcohol to acetic acid. 57 58 59