Research And Development In Equipments And Packaging

6.1. High pressure equipment and the system

In order to meet the requirements for the food industry, a high pressure equipment used in ceramic industry (CIP) has been improved by incorporating additional sensors for pressure and temperature sensing, so as to attain fast pressurizing and depressurizing speeds, and to ensure the safety of the food products.

Test equipments for foods have been developed by several equipment industries and are on the market (5-7). A typical equipment has 500 ml capacity, is made of stainless steel and works at a maximum pressure of 700 MPa. It takes only 90 seconds to attain the maximum pressure. Temperature of the inside water, used as the pressure transducing medium, is regulated by an electric heater outside the pressure vessel. Thus, in this machine, the hydrostatic pressure is directly applied to foods placed in the pressure vessel with high speed under the regulated temperature without any harmful contaminants. A total of more than 100 food companies and government institutions in Japan are equipped with the high pressure test machines in recent years and are performing research and development of new food products based on the high pressure processing.

Industrial equipments for high pressure processing of foods are operational in several food industries: a batchwise system of 10 to 50 liter-capacity and a semi-continuous system of 1 - 4 ton/hour-treatment. The former is used for processing and sterilization of packed foods and the latter for the treatment of liquid foods (6-9). These machines are small as an industrial machine, but a pressure vessel of 50 liters is similar to a heating vessel of 200 liters in capacity. The cycle time for operating the pressure machine is short, generally being 15 min for food sterilization or food processing, while a large pan takes about 1 hour for heating and cooling in conventional processing.

An industrial system for the high pressure processing of foods is similar to the conventional heat processing: raw materials are pre-treated, filled in plastic bags, sealed in vacuum and pressurized. Final products are obtained after drying the bags. Liquid food may be placed directly in the pressure vessel in a semi-continuous way.

It should also be pointed out that the use of pressure processing saves energy and is more sanitary compared to the use of high temperature processing (5-10).

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