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Pasteurizers
Pasteurizers: Machinery used in the process of heating liquids for the purpose of destroying bacteria, protozoa, molds and yeasts.
Unlike sterilisation, pasteurisation is not intended to kill all micro-organisms (pathogenic) in the food or liquid. Instead, pasteurisation aims to achieve a "logarithmic reduction" in the number of viable organisms, reducing their number so they are unlikely to cause disease (assuming the pasteurisation product is refrigated and consumed before its expiration date). Commercial-scale sterilization of food is not common because it adversly affects the tast and quality of the product.
Pasteurisation typically uses temperatures below boiling since at temperatures above the boiling point for milk, casein micelles will irreversibly aggreagate or "curdle". There are two main types of pasteurisation used today: -
- High Temperature/Short Time (HTST)
- Extended Shelf Life (ESL) treatment.
Ultra-high temperature (UHT or Ultra-heat treated) is also used for milk treatment. In the HTST process, milk is forced between metal plates or through pipes heated on the outside by hot water, and is heated to 71.7 degrees Celisus for 15.20 seconds. UHT processing holds the milk at a temperature of 138 degrees celisus for a fraction of a second.
ESL milk has a microbial filtration step and lower temperatures than HTST. Milk simply labeled "pasteursation" is used treated with the HTST method, whereas milk labiled "ultra-pasteurisation" or simply "UHT" has been treated with the UHT method.
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