Food Spoilage Due to enzymes
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Lipases Rancidity Proteinases Casein Potential health risks Enzymatic Browning Arctic Apples Proteolytic enzymes Refrences
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Food Spoilage Due to enzymes
- 1. 1 Food Spoilage Due to enzymes Zohaib HUSSAIN sp13-bty-001 Presentation Number 1 COMSATS Institute of Information Technology Abbottabad
- 2. 2 What is microbial food spoilage? • Microbial food spoilage occurs as a consequence of either microbial growth in a food • Release of extracellular and intracellular enzymes in the food environment Signs of spoilage • In normal tissues, the rates of new cell growth and old cell death are kept in balance – Changes in color – Changes in odor – Changes in texture e.g slime formation – Accumulation of gas or foam – Accumulation of liquid
- 3. 3 Spoilage by microbial growth occurs much faster than spoilage by microbial extracellular or intracellular enzymes in the absence of viable microbial cells.
- 4. 4 Lipases Rancidity Proteinases Casein Potential health risks Enzymatic Browning Arctic Apples Proteolytic enzymes Refrences
- 5. 5 Lipases •Lipase activity shown by psychotrophs isolated from milk and milk products e.g Flavobacteria and Pseudomonas species •Microbial lipases are heat stable. •Lipase activity in milk leads to the release of medium and short-chain fatty acid from triglycerides. (Hydrolytic rancidity) •Hydrolysis of as little as 1-2 % triglycerides leading to rancid off flavor. •Milk naturally also contains high levels of indigenous lipase, •It is likely that indigenous as well as microbial lipases are important in development of lipolytic rancidity in milk.
- 6. • Milk is heated to destroy milk lipases but not the bacterial heat-stable lipases. • Assay methods depend on the release of free fatty acids due to hydrolysis of milk fat • ELISA is also used to measure lipases of Pseudomonas Spp. 6
- 7. Rancidity • Microbial rancidity refers to a process in which microorganisms, use their enzymes such as lipases to break down fat. • Rancidification or rancidity, causes a substance to become rancid, that is, having a rank, unpleasant smell or taste. • Consuming rancid food products is unlikely to cause immediate illness or harm, • Reduce the nutritional value of food, and some vitamins are highly sensitive to degradation. • Produce potentially toxic compounds associated with long- term harmful health effects concerning advanced aging, neurological disorders, heart disease, and cancer 7
- 8. Proteinases • The major cause of bitterness in milk and milk products is the formation of bitter peptides due to the action of proteinases. • Proteinase activity has been detected in Pseudomonas Serratia and Bacillus species. • Heat stability of proteinases from several bacterial species was investigated by Griffiths et al. (1981). • Strict quality control is therefore critical in UHT milk products to ensure that heat-stable proteinases do not cause bitter off flavors. • The most investigated source of bitter peptides is the casein. 8
- 9. • Even when present as low as 1ng/ml in raw milk can reduce the acceptance quality of milk during normal storage. • So it is very important to use a sensitive assay to predict the shelf life of dairy products. • Laboratory tests for these proteinases include: ELISA, Flurescamine assay 9
- 10. Casein • Casein phosphoproteins (αS1, αS2, β, κ). • These proteins are commonly found in mammalian milk making up 80% of the proteins in cow milk • Casein major component of cheese • Use as a food additive, to a binder for safety matches • As a food source • Casein supplies amino acids, carbohydrates • And the two inorganic elements calcium and phosphorus 10
- 11. Potential Health Risks • Populations with greater than 10% of the protein in their diet from casein • We were at risk of cancer due to casein acting as a cancer promoter. • A Casein allergy, when your body's immune system mistakenly thinks the protein is harmful and produces allergic (IgE) antibodies for protection. • The interaction triggers the release of body chemicals • Such as histamine that cause symptoms • Swelling of the lips, mouth, tongue, face, or throat • Skin reactions such as hives, a rash, or red, itchy skin sneezing, runny nose, itchy eyes, coughing,etc 11
- 12. The China Studyis a book written about a large-scale study done with the support of the Chinese government and provincial governments across China. America's best-selling books about nutrition.
- 13. Enzymatic Browning • Fruits and vegetables turning brown when damaged/cut is exposed to air (enzyme-involved oxidation) • Enzyme involved is polyphenol oxidase (PPO). • PPO converts polyphenol, which is naturally present in all kinds of fruits and vegetables, into a brown pigment called melanin. • PPO is naturally separated from polyphenol in the intact cells. • Damage or cut destroys cell structure and mix the PPO and polyphenol together. • PPO converts polyphenol into melanin pigment. Therefore brown surfaces are formed. 13
- 14. • Arctic Apples apples that contain a nonbrowning trait introduced through biotechnology. • They were developed through a process of genetic engineering and precision breeding by Okanagan Specialty Fruits • Specifically, gene silencing reduces the expression of polyphenol oxidase (PPO), thus preventing the fruit from browning. First of its type. 14
- 15. Proteolytic Enzymes • Proteolysis Cells contain proteolytic enzymes which hydrolyse proteins into amino acids, which is responsible for the ageing and spoilage of foods. • Suitable action of proteolytic enzymes on meat produces tendering effect, which improve meat quality. • However undesirable action of this enzyme causes spoilage of meat. 15
Editor's Notes
- Cancer arises from a loss of normal growth control. In normal tissues, the rates of new cell growth and old cell death are kept in balance. In cancer, this balance is disrupted. This disruption can result from uncontrolled cell growth or loss of a cell's ability to undergo "apoptosis." Apoptosis, or programmed cell death, is the mechanism by which old or damaged cells normally self-destruct.