Food Microbiology Lecture 15 PDF

▪ Rivka H. Borger, PA ▪ Touro College ▪ Microbiology ▪ Summer 2021 ▪ There are multiple uses of microbes in the natural world. The human and microbial life are very clearly intertwined. ▪ This gave rise to many practical applications and the field of biotechnology.  ▪...

▪ Rivka H. Borger, PA ▪ Touro College ▪ Microbiology ▪ Summer 2021 ▪ There are multiple uses of microbes in the natural world. The human and microbial life are very clearly intertwined. ▪ This gave rise to many practical applications and the field of biotechnology.  ▪ Microbes can be used for specific metabolic tasks to practically benefit humans. APPLIED ▪ One area of interest is called applied microbiology. MICROBIOLOGY ▪ This area takes advantage of the microbes living in natural habitats to treat wastewater and fix damaged environments. INDUSTRIAL MICROBIOLOGY ▪ Industrial microbiology – This area explores the use of microbes in making a wide variety of food, medical, manufacturing, and agricultural products. ▪ This is an artificial use of microbes, but applies the metabolic and adaptive principles of microorganisms. ▪ Most biotechnological systems involve the actions of bacteria, yeasts, and molds. ▪ They need to be able to synthesize a certain food, drug, organic acid, or vitamin. ▪ Many of the end products are obtained through fermentation.  ▪ Fermentation - this is a general term used to refer to the mass, controlled culture of microbes to produce the desired organic compounds. ▪ Fermentation also includes use of microbes in sewage control, metal mining, and FERMENTATION bioremediation. ▪ NOTE: Fermentation in biotechnology is not the same fermentation as metabolic fermentation, although some processes such as wine production will involve biochemical fermentation as well.  ▪ Management of Drinking Water ▪ Most drinking water comes from rivers and springs. It is used in its natural form MICROORGANISMS only in remote areas. In cities, the water needs to be treated. IN WATER ▪ Water supplies from deep wells which are relatively clean require less treatment than those from sources more contaminated.  1 2 3 4 5 6 7 8 9 10 1) Water is 2) Remove 3) 4) Causes 5) Calcium 6) pH 7) filter the 8)disinfect 9)potable 10)potable pumped large chemicals settling in and lowered to water with with water is water from lakes objects are added large tanks magnesium 7.8 by gravel, chlorine or pumped to delivered and rivers such as to which is adding sand, chloramine large to trees and aggregatio responsibl CO2 anthracite storage individual branches n of small e for water tanks households particles hardness are removed, allows the water to settle ▪ In many parts of the world, the same water which serves as a source of drinking water is also used to dump solid and liquid wastes. ▪ Sewage - the used wastewater draining out of homes and industries which contains a variety of chemicals, debris, and microorganisms. ▪ There is a danger of typhoid, cholera, and dysentery linked to the unsanitary mixing of household water and sewage. ▪ Currently, some sewage is treated to reduce its microbial load before it is released, but a lot is released untreated into the aquatic environment.  ▪ Sewage contains large amounts of solid MANAGEMENT OF wastes, organic matter, and toxic WASTEWATER AND chemicals. This poses a health hazard. SEWAGE ▪ To remove sewage and all health hazards properly, treatment requires 3 phases. ▪ 1) Primary stage – floating bulkier materials (paper, bottles) are skimmed off. Remaining particles settle. Sedimentation usually takes 2-10 hours and the mixture is rich in organic matter. ▪ 2) Secondary stage - biodegradation. Bioremediators such as bacteria, algae, TREATMENT protozoa aerobically decompose remaining wood, paper, fabric, and organic molecules PHASES inside a large digester tank. This forms sludge. ▪ 3) Tertiary stage - further filtering and chlorinating prior to discharge. The treated sewage is released. ▪ All human food comes from some other organism. ▪ Rarely is it obtained in a sterile state. ▪ Microbes and humans are in direct competition for nutrients in food; microbes have very fast growth rates, so they generally have the winning edge over us. ▪ Somewhere along the lines with procuring food, with processing or preparation, food gets contaminated with microbes. ▪ The final effects depend on the amount of microbes present and whether the food is cooked or preserved. Food is fermented through Food is chemically Food can be benefited by Microbes can serve as use of microbes changed through use of the addition of microbes to food microbes alter and improve flavor, taste, or texture DETRIMENTAL ▪ Food poisoning or food-borne illness EFFECTS OF ▪ Food spoilage – growth of microbes make food unfit for consumption, adds MICROBES IN undesirable flavors, appearance and smell and destroys food value FOOD  NEUTRAL Presence or EFFECTS OF growth of microbes that do MICROBES IN not cause disease or change the FOOD nature of the food ▪ Many culinary procedures will deliberately add microbes in order to prepare foods. ▪ Food fermentation - common substances such as beer, wine, bread, cheese, yogurt, pickles are the products of food fermentation. ▪ The microbes can occur naturally or they can be added. If added, they can be added as pure or mixed samples. Sometimes we use a starter culture - a sample of known bacteria or yeasts. ▪ Microorganisms accomplish 3 functions: ▪ Leavening the flour-based dough ▪ Imparting flavor and odor ▪ Conditioning the dough to make it workable ▪ Leavening - achieved through the release of gas to produce a porous and spongy product. ▪ Without leavening, bread dough remains flat, dense, and hard. ▪ The most common microbe and leavening agent present is a strain of baker's yeast Saccharomyces cerevisiae. Other gas-forming microbes such as Clostridium, heterofermentative lactic acid bacteria, and wild yeasts can be used depending on the bread desired. ▪ Yeast metabolism requires a source of fermentable sugar such as glucose or maltose. Since the yeast undergoes aerobic respiration in bread dough, the products of maltose fermentation are carbon dioxide and water instead of alcohol. ▪ Other contributions to bread texture come from kneading which bring air into the dough and from microbial enzymes which break down flour proteins (gluten) and give the dough some elasticity. ▪ Production of beer and other alcoholic beverages takes advantage of alcohol fermentation. ▪ By fermenting carbohydrates in fruits or grains anaerobically, ethyl alcohol will be produced. ▪ Malting - releasing amylases that convert starch to dextrins and maltose, and proteases that digest proteins ▪ Mash – mix of the malt grain and warm water ▪ Wort- clear fluid that comes off during the brewing ▪ Lagered – freshly fermented beer is held for several weeks to months in vats near 0 degrees celsius as a maturation period. ▪ Wine - any alcoholic beverage which comes from the fermentation of grape juice ▪ However, any fruit can be rendered into wine. ▪ The starting point is the preparation of must - the juice given off by crushed fruit which is used as a substrate for fermentation. ▪ Grape wines are usually white or red. ▪ Color comes from the skin of the grapes. ▪ White wine can come from white skinned grapes or red skinned grapes with the skin removed. ▪ Red wine comes from the red or purple skinned grapes. ▪ The major steps for preparing wine include: ▪ Must preparation ▪ Fermentation ▪ Pasteurization ▪ Storage ▪ Aging ▪ Milk is very nutritious. ▪ It starts its journey in the cow's udder which is sterile, but as it passes out, it is inoculated with MICROBES IN MILK the cow's microbiota. Other microbes can be introduced with the milking utensils. Milk can AND DAIRY be highly susceptible to microbial growth. PRODUCTS ▪ This is one reason why milk should undergo pasteurization. ▪ Large scale cheese production is usually controlled and uses only freeze-dried samples of pure cultures. ▪ These are first inoculated into a small quantity of pasteurized milk to form an active starter culture. The amplified starter culture is inoculated into a large vat of milk where curd development takes place. ▪ Rennin is usually added to increase the rate of curd formation. ▪ After its separation from whey, the curd will be rendered to produce one of several types of cheeses – soft, semisoft, hard. The amount of fat, acid, or salt content can be adjusted in order to vary the composition. ▪ Foodborne illnesses are often called food poisoning. Not all food poisoning though is caused by microbes or their products. ▪ Several illnesses are caused by poisonous plants and animal tissues or by ingesting food contaminated by pesticides or other poisonous substances.  ▪ Can be divided into 2 categories: ▪ Food intoxication - results from the ingestion of exotoxin secreted by bacterial cells growing in food. The absorbed toxin disrupts a particular target such as the intestine or the nervous system. FOOD POISONING ▪ Food infection - associated with ingestion of live intact microbial cells which target the intestine. Some cases target the surface of the intestine while others invate the intestine and other body structures. Most food infections cause abdominal distress and diarrhea. ▪ Mader, S. (2018). Human Biology (15th ed.). New York, NY: McGraw Hill. ▪ Talaro, K (2018) Foundations of Microbiology (10 ed.) New York NY: McGraw Hill ▪ Tortora, G. (2014) Principles of Anatomy &Physiology (14th ed.) Hoboken, NJ: John Wiley& Sons. ▪ Urry, L. (2017).Campbell Biology (11th ed.). New York, NY: Pearson Education. ▪ Vodopich, D. (2011). Biology Laboratory Manual (9th ed.) New York, NY: McGraw Hill.