Hundreds of years ago it was known that if food was not stored accurately the food would go off which therefore could lead to illness. Thus they acquired the ability to preserve food in such ways as salting, drying and freezing to suspend it from deteriorating through the action of bacteria, yeast’s and moulds. Food hygiene is practices in the handling of food that help to make it safe to eat in order to avoid food poisoning which is most caused by pathogenic bacteria such as staphylococcus aureus and bacillus cereus.
This essay is going to highlight how the effective use of temperature control can be utilised to ensure the integrity of food stuffs and restrict the growth of food born pathogens thus extending the shelf life of food, by doing this temperature control would be explored, why it is used, how it can insure the integrity of food and restrict food born pathogens. Pathogens are microorganisms that cause disease; they are single celled animals capable of independent movement.
They feed by engulfing tiny food particles and reproduce by binary fission, an example of a food born pathogen would be Listeriosis, it is found in foods such as milk, vegetables, cheese meat and seafood. It can be prevented by pasteurising milk and cooking foods properly. Temperature control is a method used for the restriction of microorganisms, within this method there are many different stands ranging from heating to freezing.
Caterers have found temperature control to be favourable method for restricting the growth of bacteria because it has been said that any method of preservation involving heat in order to demolish microorganisms can be assumed the majority of enzymes would be destroyed. Meats, fish and vegetables were all once living, because meats and fish are killed before they are eaten or distributed they become inclined to deteriate and spoil by microorganisms such as saprophytic. As with humans food has danger zones, and within these zones pathogens grow rapidly and are accompanied with the formation of toxins.
The food danger zone is between the temperatures of 10oC to 60oC. When foods reach these temperatures caterers insure food is moved promptly to prevent food born illnesses. Between 71oC and 100oC cooking temperatures destroys most bacteria. At other temperatures pathogens are still able to survive. Given that temperature is one factor affecting the growth spurt of pathogens they should be moved out of the danger zones quickly, caterers used temperature probes to monitor temperature of foods.
In commercial places law states that hot food must be 64oC or hotter and cold food 0oC or cooler. If hot food were stored any lower it would support the growth of pathogens, which would be a risk to health. However limited times inside the danger zone is legally recognised because of transportation. Caterers insure the integrity of foods by using temperature control methods such as freezing, blanching and refrigeration. Freezing causes very few changes in the quality of food assuming its carried out correctly.
Science has found that when foods are frozen slowly large ice crystals are formed these are unfavourable as they fracture the cell structures of foods such as meat, this therefore results in a poor texture of the food and too much dripping when thawing consequently freezing should be carried out at a fast rate. Freezing is used on almost all foods meats, fish and vegetables, it has no effect on the majority of meats, little effect of vegetables however it changes fruit which when defrosted becomes supple.
Caterers use freezing to insure the integrity of food because it makes little changes to the nutritional value, tastes or textures of the foods, because freezing changes fruit caterers often use the method of refrigeration in order to keep the physical structure of foods. Refrigeration has minimal effects on the nutritional value of food, its texture or taste making it a very popular method of temperature control to insure the integrity of food.
Blanching foods before freezing destroys microorganisms on the surface of vegetables, however over blanching foods makes them loose their flavours, colours and nutrients whilst under blanching stimulates enzymes and is worse than doing nothing at all therefore they must be kept at the right temperature. Unlike the other methods pasteurisation cannot help but change the integrity of foods for example with milk there are many different types ranging from full fat to Soya, the heating process takes out many of the creaminess from milks such as skimmed.
Caterers attempt to prevent microbial growth in two ways by either increasing or decreasing the temperature. There are two types of low temperature methods these are chilling and refrigeration; this is where foods are placed at temperatures above 0oC because the growth of most species of microorganisms are retarded and some may even be killed however the majority are still able to grow however as stated before they grow slowly. The second method of low temperature is deep-freezing the foods are frozen if they food is required to be kept long it is suggested that it should be stored -18oC or below.
As with chilling the freezing process ‘has a killing effect’ some die but they are never eradicated, as spores are able to survive. By raising the temperature its possible to destroy the spores by putting foods at a high temperature or a longer, the destruction of microorganisms is called sterilisation. Caterers use low temperatures to preserve food based on research explaining that micro organisms can be slowed down above freezing and stopped at subfreezing because ‘metabolic reactions of microorganisms are enzyme catalysed and that the rate of enzyme catalysed reactions is dependant on temperature.
The temperature coefficient for most biological system is 1. 5 to 2. 5 so that for each 10oc rise in temperature within the suitable range, there is a twofold increase in the rate of reaction. ‘ In the eighteen hundreds Louis Pasteur developed a process of heating wine in order to destroy the microorganisms, which cause souring; the process Pasteur developed is still used by caterers today in order to kill unwanted microorganisms, its known as pasteurisation. Pasteurisation has the ability to kill the majority of all pathogens; by boiling food you can make the food sterile.
Pasteurisation has the ability to kill the majority of all pathogens; by boiling food you can make the food sterile however this often affects the taste and nutritional value. The heating from pasteurisation terminates pathogenic organisms. By using the correct temperature for foods you are stabilising the foods state of being and restricting growth of pathogens, with the example of ice cream when it is warmed it melts, this not only changes the physical structure but also provides a good temperature for the activity of microorganisms.
The texture of the ice cream also changes it becomes granular. Practical caterers use instruments such as probe thermometers to insure food is kept at the correct temperature. Freezing involves two methods to control the growth of microorganisms; low temperatures the rate of undesirable chemical changes is also reduced at low temperature reduce it. Secondly a lot of the water contained in food turns to ice when frozen therefore becomes unavailable to microorganisms. The aim of freezing is not to eliminate pathogens but to slow them down.
Freezing does not sterilise the foods just slows down the growth of micororganisms. Caterers may often blanch vegetables prior to freezing them because enzymes occur in foods that can spoil it as they can maintain a level of activity during the freezing process. Blanching is a mild heat treatment used to inactivate enzymes. As with freezing refrigeration slows down the microorganisms it does not destroy them. Another method of temperature control is heat sterilisation; this process involves using heat to destroy all microorganisms and their spores.
The amount of heat required for sterilisation depends on factors such as the PH of the food. Foods with high acidity only require a mild heat because very few bacteria can survive within those conditions, whereas low acidic foods such as meat and fish require severe heat treatment to ensure total obliteration of bacteria such as Clostridium botulinum. Food preservation has the ability to be either long term or shot term, both blanching food and cooking food is a short-term method because they prevent autolysis they also destroy some microorganisms.
Refrigeration can extend the shelf life of foods for a few days, however refrigeration is not the sole method used for preserving food with the example of milk it is accompanied with pasteurisation, milk is heated then refrigerated. Refrigeration is the most popular for of preservation used today, the idea is to slow down bacteria so food can last longer. Caterers have understood that by restricting the growth of food born pathogens and keeping the integrity of foods they would be able to extend the shelf life of food, this is mainly because there is very few things that could now destroy the food.
To go back to the question ‘how the effective use of temperature control can be utilised by practical caterers to insure the integrity of food stuffs and restrict the growth of food born pathogens thus extending the shelf life of foods’ all ideas put forward suggests that temperature control is a vital method in restricting the growth of pathogens however it does not seem that effective in insuring the integrity of foods, as noted before temperature is important from all stages from preparation to distribution, there are many foods which are subject to temperature control this is because without it the growth of pathogens are aided, it includes foods such as dairy products which are pasteurised, meats and fish which are subjected to heating, pasta and vegetables which are often blanched.
Temperature control is an important factor for the maintenance of bacteria in foods therefore it is essential that cold food is stored precisely then cooked at a temperature high enough to kill bacteria. It has been recommended that temperature probes you use in order to observe the temperature of the foods and where it’s being stored is calibrated frequently to ensure that it’s accurate.