18-Fermentation and its uses.pptx practical

food microbiology practical

1. Fermentation and its Uses Dr. Muneeb Khan Assistant Professor Riphah College of Rehabilitation and Allied Health Sciences Riphah International University, Lahore

2. Fermentation Anaerobic or partially anaerobic oxidation of carbohydrates Enzymes produced by microorganisms breakdown carbohydrates or carbohydrate-like materials into substances that are less subject to undesirable microbial activity than the original material

3. Fermented Foods Important part of the diet all over the world Presently fermentation industries (e.g. baking, brewing, wine making, vinegar manufacture) which employ pure cultures grew out of the home-scale traditional fermentation processes that relied primarily on the activities of mixed micro flora Modern fermentation plants still utilize mixed or conjoint microbial culture to produce fermented foods (e.g. yoghurt, cheese, sauerkraut, pickles)

4. Fermented Foods More than 3500 fermented foods consumed in the world Numerous beverages are produced by fermentation e.g. alcoholic (beer, wine, brandy, whisky, vodka, sake, and palm wine) and non-alcoholic beverages (tea, coffee, and cocoa) Cereals are fermented to produce leavened bread, pancakes, muffins, etc Legumes are fermented in Far East for the production of tempeh, soy sauce, miso, oncom Among dairy products cheese and yoghurt are popular Sausages and salami are produced from meat Fish is fermented in North Africa, Middle East, Europe and South East Asia

5. Objectives of Fermentation Prolong the keeping quality of the food raw materials especially in areas where other methods of preservation are technically and economically difficult to implement To enhance the flavor of some foods To Improves the physical characteristics To produce new products having longer shelf life

6. Types of Fermentation Alcoholic Fermentation Acetic Fermentation Lactic Fermentation

7. Alcoholic Fermentation Applied in the production of leavened bread and alcoholic beverages Sugars are converted into ethyl alcohol and carbon dioxide Yeast C 6 H 12 O 6 = = = = = > 2C 2 H 5 OH + 2CO 2 Most commonly species of the genus Saccharomyces such as S. cerevisiae and S. carlsbergenis are employed C 2 H 5 OH and to some extent CO 2 act as natural preservative agents in such fermented foods

8. Alcoholic Beverages B E E R is produced from barley Barley is allowed to germinate under controlled conditions to produce malt that contains active enzymes from the germination process. These help in the breakdown of starch

9. Brewing Process

10. 1. Malting: Here the conversion from carbohydrates to dextrin and maltose takes place. The grain used as the raw material is usually barley. Barley as a cereal can be preserved for a long time after harvesting and it is the malted barley that gives Beer its characteristic color and taste. 2. Milling: The malt is then mixed with water to complete the conversion of starches in the grain to sugar. After that the grain is milled to create the proper consistency to the malt. 3. Mashing: This process converts the starches released during the malting stage, into sugars that can be fermented.

11. 4. Lautering : The liquid containing the sugar extracted during mashing is now separated from the grains. It is then generally termed as wort . 5. Boiling and Hopping: Boiling the wort , ensures its sterility, and thus prevents a lot of infections. Hops are added during this stage of boiling.As I mentioned in my earlier post, hops are used to add flavor and aroma to balance the sweetness of the malt.

12. Alcoholic Beverages Wort is allowed to ferment in special vessels with the aid of selected strains of brewery yeasts ( S. cerevisiae & S. carlsbergenis ) Fermented wort is filtered to remove yeast cells and other coarse particles. Then it is allowed to mature in storage vessels Filled in bottles and pasteurized. Final product contains between 3-5% ethyl alcohol

13. Alcoholic Beverages W I N E S may be manufactured from any sugary raw material Fruits are commonly used for the purpose Wines produced from grapes are regarded as the real wines, while those made from other fruits are simply referred to as fruit wines Selected grapes or fruits of proper maturity are crushed and treated with sulphur dioxide or sulphite or pasteurized to reduce the microbial contaminations Then inoculated with a suitable yeast starter and allowed to ferment After a short fermentation, the wine is drawn off, placed in storage tanks for further fermentation, racked, stored for ageing, clarified and packed

14. Alcoholic Beverages C H A M P A G N E is manufactured from specially selected white tale wines produced from grapes Involves a secondary fermentation that yields more ethyl alcohol, carbon dioxide and flavour in the product

15. Bread Manufacture In the manufacture of pan bread and similar products, essential ingredients (wheat flour, yeast, water and salt) are mixed together and made into dough of desired quality by stretching, folding and cutting Allowed to ferment: yeast utilizes sugars and produces carbon dioxide and minor amount of ethyl alcohol Carbon dioxide is trapped in the gluten framework of the dough to give an increased volume Fermentation process in bread manufacturing is not aimed at increasing the shelf life, but to impart certain textural characteristics to the product such as increased volume and open crumb

16. Acetic Fermentation Acetic acid bacteria (species of the genera Acetobacter and Acetomonas ) are capable of oxidizing ethyl alcohol into acetic acid and water Acetic acid bacteria C 2 H 5 OH = = = = = = = = > CH 3 COOH + H 2 O Acetic acid is the main component of vinegar, which has been used for centuries as medicine, flavoring agent and preservative for products like tomato ketchup, mayonnaise and salad dressings Many pickles are also partially preserved by using vinegar

17. Vinegar Production Vinegar is a product of two-stage fermentation. In the first stage, yeast converts sugars into ethanol anaerobically. In the second ethanol is oxidized to acetic acid aerobically by bacteria of genera Acetobacter and Gluconobacter . There are two methods of vinegar fermentation. Orleans Method Generator Method

18. Vinegar Production Product of acetic acid fermentation In commercial production suitable cheep raw material such as grapes, apples, malt, sugar of molasses is fermented by yeast to produce ethyl alcohol Yeast fermented substrate is allowed to undergo acetous fermentation by the slow or quick process Improved Slow Process is Orleans Process in which fermented liquid is filled in special barrels Inoculated with fresh vinegar. After about three months at 21-29°C, about 1/3 is withdrawn and fresh quantity of the fermented liquid added Freshly acetified vinegar is stored and aged for about 6 months to improve its flavour and other characteristics. Every month about 1/3 rd to 1/4 th of the finished vinegar is withdrawn and the cycle is repeated

19. Vinegar Production Quick or Generator Process consists of an upright cylinder of varying dimensions Equipped with a spreader device to distribute alcoholic solution, a large main section filled with maize cobs, purified coke of charcoal to provide surface to the acetic acid bacteria and a lower section with air holes Fermented liquid is sprinkled from the top and air is pumped from the bottom Acetic acid bacteria present on the corncobs etc., convert ethyl alcohol into acetic acid. When the conversion is completed, the vinegar is drawn, aged, clarified and filled into bottles

20. Lactic Fermentation Most widely used biological preservation technique . The Lactic acid bacterial act on glucose and convert it into lactic acid and water. Lactic acid bacteria C 6 H 12 O 6 = = = = = = = = > CH 3 CHCOOH + H 2 O Great importance in the dairy industry, meat industry, and fruits and vegetable industry.

21. Dairy Industry Species of genera Streptococcus, Lactobacillus and others are most often used to convert the milk sugars to lactic acid. Production of yoghurt, standardized and pasteurized milk is inoculated with a culture containing Streptococcus thermophilus and Lactobacillus bulgaricus. Lactic acid produced coagulate the milk proteins. Coagulated milk may be consumed as such (yoghurt) or further processed to produce cheese.

22. Meat Industry Production of numerous meat products (sausages) is directed towards obtaining a low pH (4.0-5.5) and the production of unique flavour characteristics of the product Strains of Leuconostoc , Lactobacillus and Pediococcus are employed for this purpose

23. Fruits & Vegetables Industry Most important use of lactic fermentation in the food industry worldwide is in the fermentation of fruit and vegetable materials to produce pickles or other products Fermentation is carried out by species of Lactobacillus, Leuconostoc , Pediococcus and other suitable lactic acid bacteria Activities of other microorganisms in these products in prohibited by the addition of common salt (2.5% or higher)

24. Changes in Foods as a Result of Fermentation During controlled fermentation the growth and activities of microorganisms resulting from the existence of a favorable environment lead to the breakdown of complex components of food molecules into simpler ones Substances get metabolized into end products and are released in the environment Three major components in foods that are metabolized are Carbohydrates, Proteins and Fats

25. Changes in Foods as a Result of Fermentation When carbohydrates or carbohydrate-like compounds are attacked by microorganisms, end products such as alcohols, organic acids, aldehydes and ketones are released in the environment Human body can utilize some of them as immediate source of energy Breakdown of proteinaceous material is referred to as Proteolysis Lipolysis is the term that describes the breakdown of fatty materials Proteolysis and Lipolysis reactions usually produce off-odors in the product depending upon the degree of changes