PRESERVATION - PRESERVATION We have just seen that a large...

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PRESERVATION We have just seen that a large number of organisms have the potential to grow in our food and cause us to become ill. A far greater number cause no harm but do affect the quality of the food to the point that it will not be consumed. There are also biological and chemical processes occurring in food that can affect its quality and acceptability. The goal of preservation is to make food safe and to make it last as long as possible with as high a quality as possible. Blanching A mild heat treatment, generally applied to fruits and vegetables to inactivate enzymes that might decrease product quality. May also destroy some microorganisms and thus lead to increased product shelf life. Primary objective is enzyme inactivation. Blanching is usually done to improve product quality and not for safety reasons. It is often accomplished by heating at boiling for a few minutes to inactivate enzymes that could degrade color, flavor or other quality attributes. Pasteurization A comparatively mild process with two main objectives: Designed to destroy all pathogenic microorganisms that might grow in a specific product. Extension of shelf life by decreasing number of spoilage organisms present. Product is not sterile and will be subject to spoilage. Pasteurization is usually accomplished by heating. It is designed to kill all disease causing organisms that could grow in the food product under conditions of storage that will be employed. Milk is pasteurized to prevent tuberculosis. The process would also kill any staph, salmonella or any other pathogen that happened to contaminate the milk. The process is not designed to kill the spores of clostridia. You don’t have to worry about botulism from warm milk because the organisms can not grow in the presence of air. If the milk were stored in a can it would need a different process. Pasteurized products still contain living bacteria that will eventually cause spoilage. If you leave milk in the refrigerator long enough you will get a chunky product that will not taste very good. The bacteria that survived
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pasteurization and that could grow in the cold caused spoilage. While it would not taste good the product would be safe because of the pasteurization. Example: Milk can be pasteurized by heating at 161F for 15 seconds or 145F for 30 minutes. Process designed to eliminate Q fever organisms that are slightly more heat resistant than tuberculosis organism. Apple juice maybe pasteurized to kill yeast so fermentation won’t occur as well as pathogens that may be present. Process may be accomplished by a special form of filtration without heating. Even the mild heating of pasteurization can cause changes in flavor. For clear liquids (i.e. beer, apple juice) it is possible to use special filters to remove the bacteria and not affect flavor. This would be called cold pasteurization and is used for products like draft beer in bottles Sterilization Refers to the complete destruction of all microorganisms. Often requires at least 121 °C (205°F) for 15 minutes to destroy all spores.
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PRESERVATION - PRESERVATION We have just seen that a large...

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