Food Contamination

Food Contamination
Because the same nutrients in foods are also the same nutrients microbes need for their growth, food spoilage is inevitable. However, most infectious agents do not multiply on foods, but use them as a vector to gain entrance to the human body.

Food Poisoning results from many sources. Some of them include the following: Bacillus cereus, Campylobacter jejuni, Clostridium perfringens, Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, Vibrio parahaemolyticus, and Yersinia enterocolitica. Infection from them usually causes the same basic symptoms of acute gastroenteritis, abdominal discomfort and pain, and diarrhea, but symptoms vary -- from mild gastric distress to death -- depending on the type of bacterial infection. Transmission is usually passed via the fecal/oral route with the ingestion of the pathogen on contaminated food.

Foodborne diseases affects roughly seventy-six million people each year in the US, which is more common and deadlier than bacterial meningitis, toxic shock syndrome, and the flesh-eating strep combined. Typical bacteria that cause most of the epidemics include Salmonella, Campylobacter, and Shigella. More recently, such mutant strains as Escherichia coli 0157:H7, Listeria monocytogenes, Cyclospora cayetanensis, and caliciviruses are becoming more commonplace.

Water contamination is usually because of the presence of three bacteria and are indicators of fecal contamination -- E. coli, Clostridium perfringens, and enterococci. In the case of water contamination by Klebsiella pneumoniae, it should not be assumed that the contamination came from a fecal source. The bacterium is also found in soil and runoff can contaminate water.

Meat held at room temperature often invites bacteria from the family Enterobacteriaceae. This also happens with strains of Staphylococci, micrococci, and aerobic Gram-positive spore-forming bacilli. Refrigeration suppresses these microbes, but can allow the growth of such other organisms as pseudomonas. Eating raw meats, fish, and milk is becoming more of a hazard and should be avoided. Suspect, too, are salads prepared in restaurants where meats and vegetables share a common surface during preparation.

Color can often indicate the type of microbe involved in the spoilage:

• Black spots on meat are the result of Cladosporium species.
• White spots are from Sporotrichum carnis.
• Yellow or green spots form as a result of the Penicillium species.
• A rainbow effect, often seen on bacon and fish, is caused by a spoilage bacteria known as Photobacteria that can break down ATP to produce visible light. After a couple of days, this bacterium can grow sufficiently to enable raw fish to glow in the dark!
  

Spoiled milk, as opposed to fermented products, is caused by such capsulated organisms as Lactococcus cremoris or Enterobacter aerogenes, leaving the milk to form unpleasant strands. Various strains of clostridium can also cause milk to spoil. Contaminated ice cream in Minnesota in 1994 caused an estimated quarter of a million people to become ill. Despite this, it took a full three months before the Salmonella-type bacterium was tracked down and appropriate action taken. This is not an inspiring record designed to instill confidence in the public health system. On the other hand, when a contaminant is suspected, much food is wasted in an effort to track down a few questionable samples.


Stores of rotten black potatoes that turn into an oozing mess are the result of an Erwinia contamination.


A liver fluke, Fasciola hepatica, can be contracted by humans, mainly from eating watercress harvested from beds where infected snails live.

Listeria monocytogenes is a Gram-positive bacillus capable of growing at temperatures of 0°C (32°F) and lower. It is relatively heat-resistant, having been isolated from pasteurized products. Another reason for it being an easy microbe to be passed on is its ability to remain on the hands for long periods of time -- at least eight hours -- and is not easily removed by conventional handwashing.

Foods associated with this microbe are soft cheeses, pates, and raw vegetable dishes. Pre-cut foods are most at risk for developing listeria contamination. Most people remain relatively unaffected, except for pregnant women and newborns, where often fatal cases of meningitis and/or septicemia develop.

Almost half of all food poisonings in Japan are caused by Vibrio parahaemolyticus, a marine bacterium found off the coast there, as well as in America and southwest England. Almost all food poisonings have been the result of undercooked fish. Such was the case in an air flight from Hong Kong to the UK, where lobster salad was served. Fortunately, the new crew, picked up in India enroute, did not eat any of the salad as all others aboard were ill by the time the flight ended. Obviously, the incubation period is relatively short -- the time it took to fly from Hong Kong to the UK.
Food Contamination

Quality Characteristics of Raw Milk

Quality Characteristics of Raw Milk
Good raw milk quality is the basis for the production of high quality dairy products. The raw milk quality is controlled by the following characteristics:

Level of nutrient and reagents

Chemical physical characteristics

Level of total plate count and composition of the flora, e.g. level of spore formers, coliform, psychotrophs and thermosresistant microorganisms in the total plate count as well as level of somatic cells (cell count)

Presence or absence of pathogenic organisms such as those that cause tuberculosis, brucellosis or mastitis

Presence or absence of disease such as pus particles or toxins

Presence or absence of deleterious substances such as inhibitors or other foreign substances

Taste and flavor

Cleanliness of milk

Quality Characteristics of Raw Milk

Aromatic profile

Aromatic profile
Much have been published on the history, nature and processing of herbs, species and other aromatic plant materials used as food flavorings but one subject which has received little attention is that their sensory characteristics.

What do they actually smell and taste like? What quantitative and qualitative contribution can one expect them to give to the total flavor complex of any product which they are used? How can one describe the observable differences in aroma and flavor? The absence of any really informative articles covering this important aspect of flavoring is not surprising when one realizes how extremely difficult it is to achieve meaningful descriptions or well known but purely sensory effects (for example flavor of banana).

Certain descriptive terms have become well established by use and understood by the majority of these like to be called upon to evaluate aromatic materials, generally, however, the mere reading of a descriptive profile gives little idea of the effect obtained. It is fair to say that no color-of flavor can yet be describe verbally in any language in such a way that the uninitiated layman immediately recognize and visualize the material and be able to identify it when presented with a sample.

Even the individual words used do not necessarily convey the correct impression. For instance, one may have a reasonably clear understanding of the word “aromatic” as something which has both a hedonic and nonhedonic connotations; i.e., it is both pleasing and sweet. In the other hand, the term “green’” which are also very frequently used in describing aromas and flavors, is far less precise, ranging from the effect one associates with freshly cut grass to that of damp leaves or even of freshly cut garden herbs; all of which are quite different.

This problem is accentuated when one has to translate terms into other languages. Frequently, a single world replacement is not understood may, in fact, give totally wrong impression. In most cases one has to carry out an evaluation at first hand in order to appreciate fully the differences in aromatic character or create a picture of the total profile.

Aromatic profile

What are allergens?

What are allergens?
Allergens are substances that cause the immune system to trigger and act against itself. Normally, this condition happens when foreign bodies such as bacteria enter the human body. However, innocent and harmless bodies (proteins) such as pollen, peanuts, milk, penicillin may not be recognized by the immune system and continue to function as a harmful foreign body. Yet, wasps and other insects produce allergens as a defense mechanism.

A food allergy is triggered when natural substance is mistaken for a hostile invader, causing immune systems to mobilize to repel the invader. F00d allergies are mediated by IgE antibodies to protein-a characteristic shared with other allergens such as those present in hay fever (an acute allergic nasal condition) an wasp-sting reactions. The severity of food allergy symptoms varies from life threatening reactions when exposed to food proteins that are allergens to which they are sensitized, to less severe reactions such as skin irritation and breathing difficulties. Since no cure is available for food allergies. Avoidance is the only preventive measure available to allergic consumers.
What are allergens?