Use of: a soy protein extenders b mechanically deboned meat MDM. Vacuum packaged meats. Impermeable films used:. CO 2 levels are higher. Eh lower. In general, vacuum packaged meats are considered very safe foods and free from most pathogenic species of bacteria. Spoilage in vacuum packaged meats is manifest by:. Greening caused by microbial production H 2 O 2 or H 2 S. H 2 O 2 production in meat has been associated with several types of lactic acid. Handout - Meat Pigments. The oxidant H 2 O 2 reacts with nitrosohemochrome cured meat color cmpd to form a green porphyrin compound.
H 2 S greening occurs in fresh meats that have been vacuum packaged and stored between o C. H 2 S reacts with myoglobin to form sulphmyoglobin in meats with a pH above 6.
H 2 S is produced by:. Shewanella putrefaciens and Pseudomonas spp. Some lactobacilli when O 2 - impermeable films are used. Off odors which result from:. The type of spoilage bacteria that will dominate is influenced by several factors that include:. Is the meat product raw or cooked? Raw products have a pH of about 5. Lactobacillus, Carnobacterium, and Leuconostoc. Nitrite concentration in meat. High nitrite conc. Processed meats hot dogs, sausage and luncheon meats.
These products are composed of a variety of blended ingredients, any of which can contribute microorganisms to the food. Yeasts and bacteria are the most common causes of spoilage, which is usually manifest in 3 ways :. Slimy spoilage. Like other meat products, this occurs on the surface and is caused by the buildup of cells of yeasts, lactobacilli, enterococci or Brochothrix thermosphacta.
Washing the slime off with hot water can restore the product quality. Sour spoilage. Results from growth of lactic acid bacteria which originate from contaminated ingredients like milk solids under the casing. These organisms ferment lactose and other CHOs in the product and produce organic acids.
Taste is adversely affected but the product is not harmful if eaten. Greening due to H 2 O 2 or H 2 S production. Because greening indicates more extensive product breakdown, I would not recommend eating green wieners. Reasons Cured meats bacon, hams are resistant to spoilage:. Smoking or brining of hams. The high fat content thus low a w of bacon. Instead, spoilage of these products is often caused by molds from several genera including Aspergillus, Fusarium, Mucor, Penicillium, Rhizopus and Botrytis.
When poultry is in the advanced stages of spoilage, the skin will often fluoresce under UV because so many fluorescent pseudomonads are present. Off odors generally appear before sliminess develops. The same bacteria can produce visceral taint, a condition manifest by off odors in the abdominal cavity or poultry.
Point to remember :. During the initial stages of spoilage, the skin supports bacterial growth better than does the tissue which remains essentially free of bacteria for some time. Thus, the skin can sometimes be removed to salvage the food. Fish have high nitrogen content but no carbohydrate. The microbial quality of fish and especially shellfish is heavily influenced by the quality of the water from which they were harvested.
U nsanitized processing steps are principal culprits in fish products with high microbial loads. In general, frozen fish products have lower counts than fresh products. Bacteria on fresh fish are concentrated on the outer slime, gills and intestine. Spoilage of salt- and freshwater fish occurs in similar ways; the most susceptible part of the fish to spoilage is the gill region , and the best way to detect spoilage in fresh fish is to sniff this area for off odors produced by Pseudomonas and Acinetobacter-Moraxella bacteria.
Meat and poultry carcasses can be contaminated during slaughter by contact with small amounts of intestinal contents. Animal hides are an important source of contamination of the general environment, the hands of meat worker s, and skinned meat carcasses. Hides are a primary source of E. Hides become contaminated either because the outside of the hide is dirty, or because once removed from the animal, the inside of the hide is a good breeding place for microorganisms. Animal feeds are a source of microorganisms, especially Salmonella , which can contaminate poultry and other farm animals.
The organisms in dry animal feed spread throughout the local environment and may get on to animal hides, hair and feathers, as well as on people who handle the feeds. The term food handler can be applied to anyone who touches or handles food, and this includes people who process, transport, prepare, cook and serve food. The microorganisms transmitted to foods by food handlers may come from the hides of animals, soil, water, dust, gastrointestinal tracts and other environmental sources.
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. Food utensils are cutting boards, knives, spoons, bowls and other equipment used in food preparation, which may become contaminated during food processing and preparation. For example, in families where there is no access to running water, the food utensils may not be properly cleaned, stored and handled, and may become a major route of food contamination.
Cross-contamination of food is the transfer of harmful microorganisms between food items and food contact surfaces. Prepared food, utensils and surfaces may become contaminated by raw food products and microorganisms.
These can be transferred from one food to another by using the same knife, cutting board or other utensil without washing it between uses. A food that is fully cooked can become re-contaminated if it touches raw foods or contaminated surfaces or utensils that contain pathogens. For example, you should never:. An unsafe temperature for food storage is a major factor in food contamination. Many microorganisms need to multiply to a very large number before enough are present in food to cause disease in someone who eats it.
However, if bacteria can have warm, moist conditions and an ample supply of nutrients, one bacterium can reproduce by dividing on average every half an hour and can produce 17 million bacteria in 12 hours! So, if you leave lightly contaminated food out overnight, it will be highly contaminated and infectious by the next day. Poor personal hygiene of food handlers is another major factor in food contamination.
The most important contaminants of food are the microorganisms excreted with faeces from the intestinal tract of humans. These pathogens are transferred to the food from faecal matter present on the hands.
We have already mentioned failure to wash hands after visiting a toilet as a source of food contamination. Can you suggest other times when food handlers should wash their hands? Hands should be washed before starting work on preparing food, and after touching any food, surface or equipment that may be contaminated e.
Bad personal habits like scratching your hair and nose with your fingers also contributes to food contamination. Sneezing and coughing spreads contaminants and microorganisms through the air and onto uncovered food, and onto surfaces and hands that can transfer the infectious agents into food.
Foods can be damaged and also contaminated by pests. Many stored grains are lost through the damage done by pests, including termites mist , beetles, locusts, cockroaches , flies and rodents such as rats and mice. Pests can damage and co ntaminate foods in various ways, such as boring into and feeding on the insides of grains, or tunnelling into stems and roots of food plants.
For example, weevils cause large losses of stored grains, especially in warm and humid conditions such as in lowland areas of Ethiopia. Pests also dama ge the protective skin of foods allowing microorganisms to get inside the food and causing it to rot more quickly. Pests can pollute food with their excreta, and with bodies and body fragments when they die. They also transfer microorganisms on to food while walking on it Figure 8. Flies and cockroaches readily move between wastes and foods, transporting microorganisms with them as they go.
You now know that food can be contaminated from sources in the natural environment, people, food preparation surfaces and utensils, raw and uncooked food, animals, pests, and waste material. To prevent contamination, food production and preparation operations need to be carefully controlled. Attention also needs to be given to possible chemical contamination of food.
Food can be contaminated through the misuse or mistaken handling of chemicals, including pesticides, bleach and other cleaning materials. All chemicals detergent, disinfectant, sanitiser used in the food preparation area should be removed before food preparation begins, to prevent any chemical contamination of the food.
Physical contaminants include stones, pieces of glass, and metal. Physical contamination can occur at any stage of the food chain: for example, stones, bones, twigs, pieces of shell or foreign objects can enter food during handling and preparation. These materials should be removed, if possible, for example by sieving or picking out the items with clean fingers. Food spoilage is the process of change in the physical and chemical properties of the food so that it becomes unfit for consumption.
Food spoilage is any undesirable change in food. Most natural foods have a limited life: for example, fish, meat, milk and bread are perishable foods, which means they have a short storage life and they easily spoil. Other foods also decompose eventually, even though they keep for a considerably longer time.
The main cause of food spoilage is invasion by microorganisms such as fungi and bacteria. Microbial spoilage is caused by microorganisms like fungi moulds, yeasts and bacteria. They spoil food by growing in it and producing substances that change the colour, texture and odour of the food. Eventually the food will be unfit for human consumption. When food is covered with a furry growth and becomes soft and smells bad, the spoilage is caused by the growth of moulds and yeasts look back at Figure 8.
Microbial spoilage by moulds and yeasts includes souring of milk, growth of mould on bread and rotting of fruit and vegetables. These organisms are rarely harmful to humans, but bacterial contamination is often more dangerous because the food does not always look bad, even if it is severely infected. When microorganisms get access to food, they utilise the nutrients found in it and their numbers rapidly increase.
Food spoilage directly affects the colour, taste, odour and consistency or texture of food, and it may become dangerous to eat. The presence of a bad odour or smell coming from food is an indication that it may be unsafe. But remember that not all unsafe food smells bad. Food contamination is when food is contaminated with microorganisms or substances and eating it could result in foodborne disease.
Food spoilage is any undesired change in the natural colour, taste or texture of food items that makes it unfit for consumption because it has lost its quality and nutritional value. The term contact spoilage is used when microbial spoilage is the result of direct contact or touching between the food and any contaminated or unclean surface such as shelves, food preparation boards or unwashed hands. It also includes food-to-food contact, for example between cooked meat and raw meat or between rotting fruit and sound fruit.
Physical spoilage is due to physical damage to food during harvesting, processing or distribution. The damage increases the chance of chemical or microbial spoilage and contamination because the protective outer layer of the food is bruised or broken and microorganisms can enter the foodstuff more easily.
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Enzymes, substances naturally present in food, are responsible for the ripening process in fruits and vegetables. Enzymes are responsible for texture, color and flavor changes. For example, as a banana turns from green to yellow to brown, not only does the color change, but there is also a change in the fruit'ss texture.
Unblanched, frozen corn-on-the-cob may taste like the cob over time. This is the result of enzyme action.
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