The demand for processed foods has gone up manifold with consumption and lifestyle changes. Accordingly there have been changes in the way foods are processed and food regulations ensure that there is continuous improvement in processing methods. The tremendous advancement in processing technology ensures that there is minimum damage to the nutrients, tastes and texture of processed foods. Variations in heating and optimized temperatures are used in commercially processed food so they remain sterile and have a stable shelf life.
Thermal processing is considered as one of the most important processes for controlling foodborne pathogens in ready-to-eat (RTE) meat and poultry products as it can reduce pathogens to acceptable limits. Historically thermal processing has proved to be effective and so is used most extensively to produce safe food. If the targeted microorganisms are reduced during heating to a level of zero then the processed foods are safe for consumption till the duration of shelf life.
However, thermal processing of foods requires a complete understanding of the method of processing. There has to be the complete knowledge about how much heat a product requires and the effect of the heat on the microorganism that is targeted. The degree to which the thermal process needs to be applied is dependent on
- the physical properties of the food product
- thermo-physical properties, shape and size of the container holding the product
- the type of resistance the microorganisms in the food are likely to be shown
- the pH, water activity (aw) and salt content of the food
If there are changes in the properties of food like salt, water activity and the pH then the ability of the microorganisms to survive the thermal process is likely so all parameters have to be calculated for each product and ingredient used separately.
There are hundreds of ready to eat (RTE) products like meats, poultry, ham, lunchmeats and hotdogs etc. All these foods are thermally processed by using various methods, schedule of heat treatment and equipment. Since all the hundreds of products have different compositions and use different ingredients, the response of the thermal process on the rate at which the pathogen will be destroyed is likely to be different and also the effect on the product itself.
After the detailed study of various microorganisms, the conclusion is that there are organisms like the Clostridium botulinum bacteria that are difficult to kill and this could lead to food poisoning. The spores of the bacteria are difficult to kill as they are heat resistant. It is important to destroy them as they are also the most dangerous of all microorganisms as they can produce deadly poison. So the study of the kind of heat treatment required depends on the effect that it will have on the spores of Clostridium botulinum.
Another deciding factor is the pH level. A pH of 4.6 is acceptable for low acid foods as the point below which the bacteria will not grow or produce toxins. The amount of salt has to be factored in too as people prefer low sodium foods but food might require a higher content for preservation. Other heat resistant spores that can cause spoilage are Clostridium thermosaccolyaticum, Bacillus stearothermophilus, and Bacillus thermoacidurans if the processed foods in the cans are not stored in the right temperatures.
Food Safety Act, Rules & Regulations have defined the guidelines for Thermally Processed Foods.