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Canned Green Beans

Preservation Method and Goal

Initially, beans brought from the farm go through blanching process where they are exposed to high temperature to reduce spoilage-causing factors in foods, such as bacteria, spores, and microorganisms. After blanching, beans are then rapidly cooled to prevent heat resistant microorganisms that cannot multiply in cool temperature, such as thermophiles. Then, they are aseptically packaged, in pre-sterile containers and hermetically sealed. The lack of oxygen inside the packaging will ensure the elimination of aerobic bacteria and microorganisms. The package must be able to prevent the penetration of light and oxygen in addition to being able to withstand high temperatures and pressure during the next processing step, which is commercial sterilization.

The purpose of commercial sterilization process is to minimize populations of all spoilage and disease causing microorganisms and spores. Surviving individuals are not a concern as they will be inactive unless they receive a temperature shock. Because beans are low acid foods (pH > 4.6) in order to meet the margin of safety, a thermal process is applied during which the canned beans go into a retort machine which is sealed to create a vacuum and exposes the canned beans to high pressure steam (121o C), for 15 minutes. Although this process puts the beans in danger of losing nutrition value, and wilting, the canned beans, in their hermetically sealed state, are a shelf-stable food product with a shelf-life of up to 6 months to 2 years depending on the storage environment.