Includes readily available mono- and disaccharides like glucose and maltose, as well as more complex oligosaccharides, which are available to fewer types of microorganisms. Vegetables are a good substrate for yeasts, molds or bacteria. Because bacteria grow more rapidly, they usually out-compete fungi for readily available substrates in vegetables. As a result, bacteria are of greater consequence in the spoilage of vegetables with intrinsic properties that support bacterial growth favorable pH, Eh. Microflora of vegetables is primarily composed of:.
Staphylococci are usually unable to proliferate but cross-contamination can introduce them into other foods where growth conditions are more favorable. Soft rot.
One of the most common types of bacterial spoilage. Softening can also be caused by endogenous enzymes.
Some bacteria are capable of forming highly resistant and endurable structures called spores. These help to either:. Categories : Food safety Food preservation Food waste. In food preparation at home, foodborne microorganisms can be introduced from the unwashed hands of people who are infected by bacteria and viruses, and who cook and serve the food to family members. Imprint CRC Press. Such a change can be detected with the senses of smell, taste, touch, or vision.
FlavrSavr story:. Calgene made antisense RNA to tomato pg, constructs soften slower and so can be harvested after they are ripe better flavor. First commercially avail. Handout - Table 8. Mold spoilage. In vegetables where bacterial growth is not favored e.
Most molds must invade plant tissue through a surface wound such as a bruise or crack. Spores are frequently deposited at these sites by insects like Drosophila melanogaster , the common fruit fly. Other molds like Botrytis cinerea , which causes grey mole rot on a variety of vegetables, are able to penetrate fruit or vegetable skin on their own.
The microflora of vegetables will reflect:. Soil-borne MO such as clostridia are common on raw vegetables, and some species, like C. Sources of Contamination. Surface contamination — Soil, water, air, human pathogens from manure night soil. Harvesting - hand picking vs. Geotrichium candidum — mold on harvestors. Packaging: containers reused-sanitized.
Processing plant. Markets — handling, cross-contamination. Average composition. Handout - Fig. Like vegetables, fruits are nutrient rich substrates but the pH of fruits does not favor bacterial growth. As a result, yeasts and molds are more important than bacteria in the spoilage of fruits.
Several genera of yeasts can be found on fruit. Because these organisms grow faster than molds, yeast often initiate fruit spoilage. Specific Spoilage Organisms:.
single cause of food spoilage is invasion by microorganisms such as moulds, yeast and Key words: Food spoilage, Enzymes, Bacterial contamination, Food . Food Spoilage Microorganisms. A volume in Woodhead Publishing Series in Food Science, Technology and Nutrition. Book • Edited by: Clive de W.
Blue rot — Penicillium, fruits. Downy mildews — Phytophora , large masses of mycellium grapes. Black rot — Aspergillus, onions. Sour rot — Geotrichum candidum. Other Foods. Dairy Products - Milk is a very rich medium. Raw milk flora may include:.
All MO found on the cow hide which incl. Psychrotropic pseudomonads are common in bulk stored raw milk. Pasteurization kills most G - incl. Pasteurized fluid milk — spoiled by a variety of bacteria, yeasts and molds. In the past, milk was usually soured by LAB such as enterococci, lactococci, or lactobacilli, which dropped the pH to 4. Today, milk is more frequently spoiled by aerobic sporeformers such as Bacillus , whose proteolytic enzymes cause curdling.
Molds may grow on the surface of spoiled milk, but the product is usually discarded before this occurs. Table Butter ; high lipid content and low a w make it more susceptible to surface mold growth than to bacterial spoilage. Rancidity due to butterfat lypolysis caused by P. Cottage cheese can be spoiled by yeasts, molds and bacteria. G - aerobic rod bound in soil, water, and intestinal tract of vertebrates. Penicillum, Mucor and other fungi also grow well on cottage cheese and impart stale or yeasty flavors. Ripened Cheeses — 1 low a w , 2 low pH and 3 high salt inhibit most spoilage microorganisms except surface mold growth.
Spores of C. Swiss with intrinsic properties that are less inhibitory e. Defects Table Eggs have several intrinsic parameters which help to protect the nutrient-rich yolk from microbial attack. Freshly laid eggs are generally sterile, but soon become contaminated with numerous genera of bacteria.
Eventually, these MO will penetrate the eggshell and spoilage will occur. We should remember that spoilage is not necessarily a bad thing. It shows us that a food has not been made or kept in the best conditions, alerting us to the possible presence of pathogenic microbes. Also decomposition returns the chemicals in food back to the environment, to be used again in the life cycles of Earth. There are three main types of microbes that cause spoilage:. Kaysner, C.
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