Food Fermentation Lecture 5 PDF

Kingdom of Saudi Arabia ‫المملكة العربية السعودية‬ Ministry of Education ‫وزارة التعليم‬ Jazan University ‫جامعة جازان‬ Collage of Nursing and Health ‫كلية التمريض وال...

Kingdom of Saudi Arabia ‫المملكة العربية السعودية‬ Ministry of Education ‫وزارة التعليم‬ Jazan University ‫جامعة جازان‬ Collage of Nursing and Health ‫كلية التمريض والعلوم الصحية‬ Sciences ‫قسم التغذية االكلينيكية‬ Department of Clinical Nutrition Lecture 5 Food Fermentation  Objectives To know and understand: 1)What is the importance of fermentation process? 2)What is the fermentation? 3)What are the important microorganisms that used for food fermentation? 4)What are the beneficial effects of fermentation process? 5)How can food fermentors be improved? What is the importance of fermentation process? Throughout the centuries fermentation has been one of the most important methods for manufacturing many kinds of food (Table 1). It still remains one of the most important methods.  Today’s fermentation technology plays an important role in ensuring the food security of millions of people around the world. Relatively few people, are aware that many food products such as bread, vinegar, cheese and yogurt are prepared and/or preserved by fermentation processes.  Fermentation is also used to improve the health benefits of functional foods such as tempeh and miso. Functional foods are foods containing significant levels of active components that impart health benefits beyond our basic needs for sufficient calories, essential amino acids, vitamins and minerals. In order to use fermentation in food production you should be able to understand what is fermentation?  WHAT IS FERMENTATION? The chemical breakdown of a substance by bacteria, yeasts, or other microorganisms, typically involving effervescence and the giving off of heat. The fermentation (anaerobic respiration) is the result of growth of bacteria, yeasts, molds, or combinations of these. The changes that occur during fermentation are caused by the enzymes liberated by these microorganisms. What is the anaerobic respiration? Anaerobic respiration is a way for an organism to produce usable energy without the involvement of oxygen; it is a respiration without oxygen. The important microorganisms used for food fermentation? The predominant fermenting organisms used in food production are yeasts and the lactic acid bacteria. Both groups of organisms ferment the sugar in the starting substrate, to obtain energy by elimination the hydrogen accumulated in the oxidation of sugars.  The lactic acid bacteria are involved in the production of most of the fermented foods such as olives, pickles, yogurt, and cottage cheese. The fermentative yeasts produce ethyl alcohol and carbon dioxide from sugars.  There are also foods such as bread and vinegar which are produced using the fermentative activities of these organisms followed by the oxidative action of other bacteria. Diagram of respiration and fermentation ❑The former diagram showed that, ATP and pyruvic acid are formed during fermentation. ❑Yeast cells also have enzymes that transform pyruvic acid into ethanol. The conversion and formation of substances by enzymes of cells constitutes the action of fermentation (the original name for enzymes was in fact "ferments").  ATP (adenosine triphosphate) serves as the major energy "currency" in all living organisms. It is produced in aerobic respiration in the presence of O2, while produced in fermentation in the absence of O2. In lactic acid fermentation, there is a net production of 2ATP molecules per glucose molecule, and no atmospheric oxygen is used. ▪The formation of lactic acid by certain bacteria used in yogurt production. The equation for lactic acid production from glucose is: C6H12O6 (glucose) → 2 CH3CHOHCOOH (lactic acid) The production of lactic acid from lactose and water may be summarized as: C12H22O11 (lactose) + H2O (water) → 4 CH3CHOHCOOH (lactic acid) Milk lactose ----> glucose ----> pyruvic acid ----> lactic acid+ ATP (a sugar) Lactic acid fermentation is used to convert lactose into lactic acid in yogurt production. It also occurs in animal muscles when the tissue requires energy at a faster rate than oxygen can be supplied. Yogurt Production by lactic acid fermentation There are many ways to make yogurt, but the food itself is simply milk fermented by two species of lactic acid bacteria, Streptococcus thermophilus and Lactobacillus bulgaricus growing at about 45oC.  The Streptococcus produces so much acid that the pH drops to about 3. The Lactobacillus is responsible for much of the flavor and aroma of the yogurt. The entire process takes only a few hours.  Alcoholic fermentation A second metabolic pathway in the production of ATP molecules from glucose and is performed, for example, by the fermentative yeasts. The process begins with the breakdown of glucose into pyruvic acid and the production of ATP.  Then, the pyruvic acid molecule is further broken down with the production of ethanol and carbon dioxide. No atmospheric oxygen is required for this process. C6H12O6-------> 2CH3CH2OH + 2CO2 + energy glucose ethanol Yeast and certain bacteria perform ethanol fermentation. Ethanol fermentation has been used in the production of beer, wine, and bread.  Acetic acid formation An additional pathway following alcoholic fermentation is the acetic acid formation. The bacterium Acetobacter can break down ethanol by oxidation to produce acetic acid and water. The production of acetic acid results in additional molecules of ATP.  Acetic acid gives the aroma and taste to vinegar. In the formation of vinegar, yeasts first ferment sweet apple cider to form ethanol. Then oxidative bacteria (Acetobacter) converts ethanol to acetic acid (vinegar). CH3CH2OH + O2 ----------> CH3COOH + H2O + energy Ethanol Acetic acid Starches and sugars from grains and fruit ferment into sour tasting vinegar and condiments. Examples include apple cider vinegar, wine vinegar, and kombucha.  Vinegar is an example of a foodstuff that employs both fermentation and oxidation by microorganisms. The fermentation of a substrate such as apple or grape for production of vinegar using the yeasts naturally present on the skin of this substrate can result in the production of about 12% ethanol. The subsequent oxidation step is carried out by the Acetobacter, which is present in nature wherever fermentative yeasts occur. What are the beneficial effects of fermentation process? The major aim for the fermentor microorganism is energy production for itself, but a number of other metabolic and bio-chemical changes take place that can improve the flavor, digestibility, shelf life, and nutritional profile of the food being occurred ❖Also fermentation process serves several functions, such as the providing of food substrates with proteins, essential amino acids, essential fatty acids, vitamins, carbohydrates and anti-oxidants.  1-Nutritional value of fermented foods ❑Traditional fermented protein-rich foods play an important role for improving the diets of people in tropical countries. For example, growth of the fungus Aspergillus niger for 24 to 30 hours on cassava flour with an initial content of 2% to 3% protein and 80% to 90% carbohydrate resulted in a product containing 18% to 20% protein and 30% to 35% carbohydrate. ❑The germination and fermentation of cereals make their iron content more available, the deficiency of which is responsible for the high risk of anemia in tropical countries. 2-Removal of anti-nutritional factors ❑Many fruits and vegetables contain naturally occurring toxins and anti- nutritional compounds. ❑These can be removed by the action of micro-organisms during fermentation. For example, the fermentation process that produces the Sudanese product Kawal, removes the toxins from the leaves of cassava, so fermentation is an important step in ensuring that cassava is safe to eat.  3- Digestibility Fermented foods are often more digestible than unfermented foods, this is because micro-organisms produce enzymes, such as cellulases and pectinases which are not formed in human body. Microbial cellulases breakdown cellulose into sugars which are then, be digested by humans. Also, Pectinases soften the texture of foods and liberates sugars for digestion. Example: Starchy porridges are commonly fed to weaning infants in developing countries. The small capacity of the infants stomach, means that it is impossible for the child to consume adequate energy from this porridge. Solution: By acidifying the porridge through lactic acid fermentation, starch is broken-down into glucose and dextrose, which reduce the viscosity of the porridge and increase its energy. Thus the child is more able to meet its energy requirements.  4-Medicinal benefits Fermentation is an important process for reducing the microbial contamination of foods. Studies have shown that children fed with fermented gruels had a 33% lower risk of diarrhea than those fed unfermented gruels, owing to the inhibition of pathogenic bacteria by lactic acid forming bacteria. There is a scientific basis to these benefit effect: 1.Lowering of the pH during fermentation, inhibits the growth of food poisoning bacteria and destroys certain pathogens. 2. Some lactic acid bacteria (e.g. Lactobacillus acidophilus) and moulds have been found to produce antibiotics and bacteriocins. 3.The beneficial health effects of lactic acid bacteria on the flora of intestine are well indicated. 4.Substances in fermented foods have been found to have a protective effect against the development of cancer.  Fermentation Facts: ❑Fermentation is an anaerobic process, meaning it does not require oxygen in order to occur. However, even when oxygen is abundant, yeast cells prefer fermentation to aerobic respiration, provided a sufficient supply of sugar is available. ❑Fermentation occurs in the digestive system of humans and other animals. ❑In a rare medical condition called gut fermentation syndrome or auto-brewery syndrome, fermentation in the human digestive tract leads to intoxication by ethanol production. ❑Fermentation occurs in human muscle cells. Muscles can expend ATP faster than oxygen can be supplied. In this situation, ATP is produced by glycolysis, which does not use oxygen  39 Thank You