Question 10 / 2 pointsAn intrinsic factor of food that can determine whether spoilage occurs isQuestion options:A)the water content.B)the storage temperature.C)storage packaging.D)the degree of processing.E)the amount of preservatives added.
Food spoilage is an unpleasant appearance, smell, and bad taste of a food which not favorable for human consumption. Food spoilage is caused by different types of microorganism such as: Bacteria, fungus, yeasts etc. Show Food spoilage has been a continuing problem ever since humans first discovered they could produce more food than they could eat in a single meal. We all know of Marco Polo’s travels to China in the 13th century to obtain spices and explore new trade routes. What often is not mentioned is that the spices brought back from China were more than just a luxury; the spices were essential for improving the smell and taste of spoiled food. Refrigeration was virtually unknown, and canning was yet to be invented. Food Spoilage Comes from Several Microbial SourcesSpoiled foods usually have an unpleasant appearance, aroma, and taste. Sometimes, however, spoilage can be difficult to detect, such as when staphylococci deposit exotoxins in food or when few bacteria are present to cause a perceptible change. Contaminating microorganisms can be transmitted to foods in several ways. Airborne pathogens can fall onto fruits and vegetables and then penetrate the product through an abrasion of the skin or rind, whereas crops carry soilborne bacterial pathogens to the processing plant. Shellfish concentrate pathogens by straining contaminated water and catching the microbes in their filtering apparatus, and rodents and arthropods transport pathogens on their feet and Human handling of foods also provides a source for transmission. For example, bacterial pathogens from an animal’s intestines can be transmitted to and contaminate meat handled carelessly by a butcher. Several factors that can determine food spoilageBecause food is basically a culture medium for microorganisms, the chemical and physical properties in and surrounding the food have a significant impact on the type of microorganisms growing on or in the food. Several intrinsic and extrinsic factors determine whether foods are likely to spoil quickly or resist spoilage.Conditions naturally present in foods that influence microbial growth are called intrinsic factors. These include the following:
The food industry recognizes three groups of foods based on their intrinsic properties. Highly perishable foods are those that spoil rapidly. They include poultry, eggs, meats, most vegetables and fruits, and dairy products. Foods such as nutmeats, potatoes, and some apples are considered semiperishable, meaning they spoil less quickly. Nonperishable foods are often stored in the kitchen pantry. Included in this group are cereals, dried rice and beans, macaroni and pasta products, flour, and sugar. Extrinsic FactorsEnvironmental conditions surrounding the food (food storage and packaging) are extrinsic factors influencing microbial growth and food spoilage:
A good example for the relationship of intrinsic and extrinsic factors with microorganisms is dairy products such as milk. Milk is an extremely nutritious food for both humans and microbes. It is an aqueous solution (87% water) with a pH of about 7.0 and contains proteins, carbohydrates, and fats. About 2.5% is a protein, consisting of casein and lactalbumin. Carbohydrates make up about 5% of the milk. The major carbohydrate is lactose, sometimes referred to as milk sugar. The last major component of milk is butterfat, which comprising about 4% of the milk, is removed in the preparation of nonfat (skim) milk or low-fat milk. However, when bacteria contaminate milk, the cells secrete enzymes that digest fats into fatty acids. We say the milk becomes spoiled; it is rancid and unfit to drink. A common type of milk spoilage often takes place in the kitchen refrigerator or dairy case at the supermarket. Here, species of Lactobacillus, Streptococcus, or Paenibacillus (a spore-forming genus), which are ubiquitous in nature, are introduced during milking and processing. Not all these cells are killed by pasteurization, so the survivors can multiple slowly, fermenting the lactose into lactic and acetic acids. Enough acid can develop to change the structure of the protein and cause it to curdle (coagulate). Milk also can be contaminated by gram-negative rods, such as Escherichia coli and Enterobacter aerogenes. These bacterial species produce acid and gas from lactose. The acid curdles the protein, whereas the gas forces the coagulated casein (curds) apart, sometimes so violently that they explode out of the container. The result is called “stormy fermentation.” Clostridium species also cause this reaction. References and Sources
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