File Name: spoilage of milk and milk products by microbes .zip
- INTRODUCTORY DAIRY MICROBIOLOGY
- Microorganisms in milk: the 7 biggest threats to milk production
- Microbiological Spoilage of Dairy Products
As with all food products, health and safety are paramount. For reasons of safeguarding public health, the dairy industry treats milk with heat, destroying pathogenic bacteria, which can cause illness in humans. The process has its origins in the 19th century, when milk was a common transmitter of tuberculosis and typhus.
INTRODUCTORY DAIRY MICROBIOLOGY
The Milk Microbiology section contains information relating to microbial concerns in milk. A brief overview of dairy microbiology is presented below as an introduction this section.
The topics covered are:. Milk is virtually sterile when it is synthesized in a healthy cow's udder mammary gland. Cows, like humans, are natural reservoirs of bacteria. Many of these bacteria are not harmful to humans, but some may be harmful to humans even though the cows are not affected and appear healthy. Milk may become contaminated with bacteria during or after milking. The mammary glands of cows and humans can become inflamed due to a bacterial infection called mastitis.
During a mastitis infection, very high numbers of bacteria present can be in the udder and in the milk. Some disease causing organisms pathogens can be shed through cow feces and may contaminate the outside of the udder and teats, the farm environment bedding, for example and the milking equipment.
Although optimal growth conditions for bacteria are different for different organisms, milk contains important nutritional components for mammal growth, and, therefore, it is also an ideal medium for the growth of many different bacteria. Temperature plays an important role in bacterial growth.
The area of dairy microbiology is large and diverse. The bacteria present in dairy products may cause disease or spoilage. Some bacteria may be specifically added to milk for fermentation to produce products like yogurt and cheese. A detailed discussion of fermentation bacteria is outside the scope of this web site, although these organisms are discussed briefly in the section on yogurt production and cheese production.
This section of the web site is dedicated to the discussion of pathogens because of their importance in human health. Human illness from milkborne pathogens is usually associated with consumption of raw milk or products made from raw milk such as fresh cheeses. In the past 20 years, foodborne illnesses from dairy product consumption have been predominantly associated with Salmonella enterica , Listeria monocytogenes , Campylobacter jejuni , and Escherichia coli OH7.
These organisms have been isolated from bulk tank samples at rates ranging from 0. Because there is a risk of pathogen contamination in milk produced from healthy cows under sanitary milk conditions, pasteurization of milk prior to consumption will destroy pathogens and provide protection for illness associated with consumption of dangerous microbes.
Occasionally, human illness has been linked to pasteurized milk products but these cases usually have been a result of contamination of the product after pasteurization or improper pasteurization. Milk Microbiology The Milk Microbiology section contains information relating to microbial concerns in milk.
Microorganisms in milk: the 7 biggest threats to milk production
The wide array of available dairy foods challenges the microbiologist, engineer, and technologist to find the best ways to prevent the entry of microorganisms, destroy those that do get in along with their enzymes, and prevent the growth and activities of those that escape processing treatments. Troublesome spoilage microorganisms include aerobic psychrotrophic Gram-negative bacteria, yeasts, molds, heterofermentative lactobacilli, and spore-forming bacteria. Psychrotrophic bacteria can produce large amounts of extracellular hydrolytic enzymes, and the extent of recontamination of pasteurized fluid milk products with these bacteria is a major determinant of their shelf life. Fungal spoilage of dairy foods is manifested by the presence of a wide variety of metabolic by-products, causing off-odors and flavors, in addition to visible changes in color or texture. Skip to main content.
The field of this invention concerns the determination of food freshness, and, in particular, methods and devices for the detection of microbial spoilage in food products. The spoilage and souring of perishable foods with time is an on-going problem for the consumer and food product provider alike. Although some deterioration in freshness is due to oxidative processes, spoilage and souring is in large part due to the growth of microbes such as bacteria, yeasts, and fungi. To derive energy for their growth, these microbes break down food carbohydrates, proteins and fats. The breakdown process produces a variety of low molecular weight molecules such as carboxylic acids e.
The Milk Microbiology section contains information relating to microbial concerns in milk. A brief overview of dairy microbiology is presented below as an introduction this section. The topics covered are:. Milk is virtually sterile when it is synthesized in a healthy cow's udder mammary gland. Cows, like humans, are natural reservoirs of bacteria.
Spore-forming bacteria in raw milk are predominantly Bacillus spp. (such as B. cereus, B. licheniformis,. B. megaterium, and B. subtilis). Clostridium spp. are.
Microbiological Spoilage of Dairy Products
June 1 is World Milk Day: a good reason to take a closer look at this tasty drink, which is very nutritious, but also an ideal breeding ground for harmful microorganisms. In recent years, milk has been quite discredited: It has been said that milk makes people sick, fat and tired. Many people have reduced their milk consumption due to health or ethical reasons. Nevertheless, milk contains numerous valuable nutrients.
J Food Prot 1 October ; 81 10 : — Milk spoilage caused by psychrotrophic bacteria and their heat-stable enzymes is a serious challenge for the dairy industry. In many studies, spoilage has been explored based on the simplistic view of undesirable enzymes produced by planktonic cells.
Даже президент Соединенных Штатов не решался бросать вызов Фонтейну, что не раз позволял себе Стратмор. Для этого нужен был политический иммунитет - или, как в случае Стратмора, политическая индифферентность. Сьюзан поднялась на верхнюю ступеньку лестницы. Она не успела постучать, как заверещал электронный дверной замок. Дверь открылась, и коммандер помахал ей рукой. - Спасибо, что пришла, Сьюзан. Я тебе очень благодарен.
Пошел к черту. - У меня неотложное дело! - рявкнул Беккер. Он схватил парня за рукав.