Food Hygiene Essentials

Pseudomonas bacteria are a genus of bacteria which exist widely in the environment. They are gram negative, rod shaped, non spore forming, motile, flagellated aerobes. Pseudomonas aeruginosea, probably the most well know of all pseudomonas strains, is an opportunistic pathogen that has the capability of adapting to many niches. It can infect animals and humans alike and can cross the species barrier and for this reason it is considered a potentially zoonotic pathogen. This type of bacteria is immune to many types of bacteria because it has within it’s cell wall a mechanism known as an efflux pump which pumps antibiotics back out of the cell before they have had time to take effect. It is the second most common bacterial contaminant in hospitals and it is known to be paticularly malicious in burn units where it prevents the regeneration of healthy tissue. Bacteria of the pseudomonas family are grown on blood agar which turns from a blood red color to a marine blue/green hue. It also gives off a quite pleasant slightly minty smell.

One form of Pseudomonas pathogen causes a highly contageous disease in horses which is also highly infectious to humans. The disease in horses is know as glanders because it affects the glands in and around the throat and jaws of the horse. This disease was common when colonial forces shipped large quantities of horses to places like Africa, the Middle East and the Far East. Now, this disease is more rarer. The scientific name of this pathogen is Pseudomonas Mallei and it is registered as one of the possible bacterial strains that could be used in bacterial warefare together with Clostridium Botolinum and Anthrax.

Other forms of Pseudonas bacteria are known to cause spoilage in food at low temperatures. These psicrophilic Pseudomonas strains include: P. fragi which causes spoilage of dairy products , P. taetrolens which causes mustiness in eggs and P. mudicolens, and P. lundensis, which causes spoilage of milk, cheese, meat, and fish.

The term spoilage is used in food hygiene for a condition by which the food takes on an unpleasant texture, color change smell taste. This does not mean that the food has necessarily become a serious health risk in the same way as if meat were infected with e.coli or salmonella, for instance, but at the same time it is definitely not advisable to eat spoiled food. It means that the food has been infected with bacteria which cause the physical nature of the food to change. For instance, meat may become slimy to the feel or the outer lawyer of certain foods may become pulpy, it may also smell slightly sour and change color. This happens to food which has been stored in refrigerated conditions for long periods of time in places which have not been properly cleaned with anti bacterial disinfectants. I often see this condition in places such as deli counters where meat is sliced in front of the customer.

However a little slime on meat, such as with cured pastrami in particular and with other types of processed meats is not always a sign of spoilage. It may well be due to a reaction between the protein of the meat, the curing chemicals and the air. Many manufacturers now use preservatives to prevent such spoilage. In addition, the reaction of the preservative with the air and other factors within the meat can cause the color of the product to change slightly as well. The color of the may become slightly irridescent or take on a greenish hue. If the meat smells even the slightest bit sour, feels or looks slimy or has a bad color refuse to accept it.

Spoiled food such as cured meats meat can cause stomach discomfort, diarrhea, vomiting or mild allergic symptoms in some people and may even become more serious in people whose immune system is compromised. Remember this central rule of food hygiene, “When in doubt throw it out”.

Fish products are particularly susceptible to spoilage and it can be very difficult to guess from a casual inspection if the deterioration of the fish is due to spoilage bacteria such as the psicrophilic pseudonmonas species stated above or if the cause is due to more dangerous, pathogenic forms of bacteria. If fish looks even slightly slimy, discolored or smells in the least sour don’t buy it or if it has turned bad in your fridge throw it out and clean you fridge thoroughly with disinfectant. (A tactic used by many fresh fish mungers to hide the tell tale smell of fish which has started to show signs of going off is to constantly pour sea water over it. Watch out for this trick. If you are not sure if you are smelling the actual fish or sea water, don’t buy the fish). Most importantly, keep all fish products in closed containers to avoid cross contamination with of by other food products in your fridge.

The same goes for eggs milk and cheese, if you distinguish any changes in color texture or smell, don’t take any risks, better to throw out and buy fresh. To lower the risk being sold spoiled or food which is about to spoil, buy only from supermarkets and stores which are very busy and have a high turnover of merchandise, particularly in the deli sections. Don’t be embarrassed to inspect what you buy, you are paying for fresh and healthy food and the decision to take what is on offer or not is entirely your own. The customer is always right. If you notice that the food you buy goes off quickly and you know that a). your fridge is clean and b). the temperature of the fridge is as it should be then take the food back to the store with your receipt and demand a refund or a fresh replacement. If the problem continues report your findings to your local authority for food hygiene.

In my last article on the subject of bacteria (shigella) I described some bacterial terminology in lay man’s terms to help you to understand the scientific terminology. Today I would like to touch a little upon the subject of how we categorize bacteria. There are many species of bacteria and the have evolved in many different ways. Each has found a niche in the evolutionary ladder and they have adapted themselves to be able to live in a vast variety of different conditions. What I want to do is to go through some of the different conditions in which bacteria live and by which bacteria are categorized.

The first three categories I am going to describe relate to different temperature conditions in which bacteria can be found and by which they are categorized for having this quality.

Psicrophilic. Psicro in Greek means low. Psicrophilic bacteria are ones which prefer to function at low temperatures. Normally speaking, low temperatures means below 5 degrees Celsius. The advantage that these bacteria have by utilizing cold conditions is that there are very few other bacteria that can compete with them at this temperature. From a food hygiene perspective these are the bacteria which cause refrigerator spoilage. If you have ever notices a slightly slimy surface to food that is kept at low temperatures this sliminess can be caused by psicrophilic bacteria. Normally these are not considered to be pathogenic bacteria but if you are particularly sensitive eating food that has been affected by psychrophylic bacteria can cause mild to medium stomach upset.

Mesophilic. Mesophilic bacteria are once which prefer to perform their metabolic functions at a moderate temperature range. This means that this category of bacteria is active between temperatures of 10 degrees Celsius to 40 degrees Celsius. many processes in the food industry, particularly the cheese industry, and most fermentation processes occur within this temperature range. This is also the temperature at which the vast majority of pathogenic bacteria function and therefore this presents the need for close control of bacteria action within the cheese and fermentation industries. Mistakes in this area would definitely cost lives. It is also the temperature at which most bacteria attack our bodies.

Thermophilic. Thermophilic bacteria are bacteria which have developed the ability to operate their metabolic functions at high temperatures. Bacteria of this classification can survives in temperatures in excess of 100 degrees Celsius. Some bacteria of this classification are used in the food industry and some are found in nature. In processes of controlled rotting the development of thermophilic bacteria is undesirable because they will break the materials down too much. This can be caused in the manufacture of compost by giving too much food. By giving too much food the temperature rises, the desirable bacteria are killed as well as the worms and the thermophilic bacteria turn the entire compost heap into useless mush.

The next three categories that I would like to discuss refers to the chemical environment in which bacteria live with respect to levels of acidity. Bacteria have developed the ability to survive in a wide range of acidic or non acidic conditions. Many such bacteria by acting in different acidic or non acidic climates become desirable from an industrial point of view. Many industrial processes rely upon bacterial activity for the production of the end product. This is true of the food and non food industries. However, some conditions become the target zone of pathogenic bacteria.

Basophilic. Bacteria which thrive in a basophilic climate are bacteria which prefer to live in a base of alkali environment. The level of which depends upon the specific species of bacteria. Some pathogenic bacteria become pathogenically active in alkali environments particularly bacteria which break down the proteins in meat and fish. They have developed this ability because ammonia is produced in decomposing flesh which is an alkali. In saying that many industrial processes are dependant upon basophilic bacteria.

Normophilic. Normophilic bacteria are ones which perform their metabolic functions at a neutral PH level or there about. Bacteria wich are active within this climate include many types of pathogens. You may remember that we have already talked about the fact that most pathogenic bacteria cannot remain active when acidity levels are raised and PH is lowered. We can therefore state that a great many pathogens function in mesophilic, normophilic conditions. If you think about it this is logical because the acidic conditions within a body are more of less neutral. The bacteria have become suited to the environment in which they are designed to exist.

Acidophile. Bacteria which have developed to survive within an acidophile environment are ones which perform their metabolic function in a strong acid environment. Again, bacteria such as these have evolved in nature to continue the degradation of matter when conditions become too acidic for normophilc bacteria. This category of bacteria is also used extensively throughout industry for a great many purposes. Not many bacteria within this group are pathogens.

The third category of bacteria about which I would like to discuss with you refers to how the bacteria relates to the use of oxygen. by this I mean can the bacteria survive with or without the presence of oxygen. Most pathogenic bacteria exist in an anaerobic environment or can change from an aerobic environment to an anaerobic one depending on the environment in which it is trapped.

Obligate aerobic. An obligate aerobic bacteria is one which must have the presence of free oxygen around it. Many industrial processes rely upon bacteria of this category.

Obligate anaerobic. Obligate anaerobic bacteria are bacteria which for the most part cannot tolerate an oxygen rich environment and perform all their metabolic functions through fermentation. Some bacteria from this category are pathogens.

Facultative anaerobic bacteria are ones which can switch from an oxygen rich environment to an environment devoid of oxygen and back again as the need arises. Many pathogenic bacteria belong to this category. By belonging to this niche facultative anaerobic bacteria have ensured the ability to survive even when conditions change.

Now that you have this information look up different bacterial species on the Internet and see if you can distinguish pathogenic bacteria in several of the different categories stated here.