JPS59166068A - Thermal sterilization with microwave radiation - Google Patents

Abstract

PURPOSE:To uniformize the temperature increase of a food and prevent the burst of a packaging film, by vacuum-packing a food consisting of a mixture of solid and liquid with a film transparent to microwave radiation, immersing the packed food in hot water, and irradiating with microwave radiation. CONSTITUTION:A food consisting of a mixture of solid and liquid, e.g. hamburger steak, meatball, etc. is vacuum-packed with a film transparent to microwave radiation (e.g. polyethylene film). The packed food is immersed in a hot water bath containing hot water maintained at 60-70 deg.C, and irradiated with microwave radiation from the outside of the bath for 3-10min to effect thermal sterilization of the food.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for heat sterilizing a solid-liquid mixed food that has been subjected to vacuum sterilization using microwaves. 1-Relates to a method of heat sterilization by irradiation with

Traditionally, solid-liquid mixed foods such as hamburgers and meatballs have been heat-killed using microwaves. L. Shun, it has been proposed to vacuum package each yuzu glass in film form.

However, according to this extreme sterilization method, bacteria adhere to the food during the vacuum packaging process after heat sterilization, reducing the sterilization effect by half. In addition, when vacuum-packaged solid-liquid mixed foods are heated and sterilized using microwaves, only the outer surface of the food is locally heated, and water vapor is generated in this heated area, which causes the packaging bag to burst and sterilize it. There was a problem that the effect was lost.

This invention was made in view of the above circumstances, and its purpose is to sterilize solid-liquid mixed foods such as hamburgers and meatballs by heating with microwaves while vacuum-packaging them in various plastic films. It is an object of the present invention to provide a heat sterilization method that can perform sterilization by heating and that does not cause the packaging bag to burst due to generation of water vapor or the like.

The above object of the present invention is achieved by heating and sterilizing a solid-liquid mixed food that has been immersed in hot water by irradiating it with microwaves.

The method of the present invention will be specifically explained below.

Foods that are heat sterilized by the method of the present invention are so-called solid-liquid mixed foods that are a combination of fixed substances such as fruit pulp and liquid juice, as typified by hamburgers, meatballs, and the like.

To heat and sterilize such foods according to the uninvented method, the foods are first vacuum packaged using various plastics, glass, or a combination of these materials that transmit microwaves.

In this way, the empty packaged solid-liquid mixed food is immersed in warm water at 60°C to 70°C. Soaking a solid-liquid mixed food in a 7-temperature bath within this temperature range is as follows:
This is to equalize the warm rise of the solid-liquid mixed food and to prevent evaporation of the liquid component and expansion of the film.

Also, heating water in the range of 68 to 70 degrees Celsius means that the temperature of the eyelids irradiated with microwaves is low, and one-liquid heated food is more likely to be heated due to microwaves than hot water with a higher temperature. (This is because solid-liquid mixed foods can be preferably heat sterilized.

The microwave used in the heat sterilization method of the present invention is a type of electromagnetic wave with a wavelength of 1 m to 1 cm (frequency 300 M
I (z ~ 30 GIIz) Refers to an extremely short 'LU wave that is completely invisible. In the microwave heating of the present invention, a microwave of 2450 MI (z) is specifically used among the above-mentioned microwaves.

Microwave heating using such a wavelength is a heating method in which the object to be heated itself becomes a heating element based on the principle of high-frequency dielectric heating. This microwave heating is good (as it is known,
Food that is heat sterilized becomes 87 (f-form), and the electric dipoles (molecules separated into positive and negative poles) that make up the substance of this food begin to vibrate violently using the frequency of the high-frequency electric field, and the molecules Friction occurs between them and they heat up, causing the temperature of the substance to rise.

The heat generation M absorbed by this object tL and converted into heat, p is the following formula % formula % In the formula, p is the power absorbed by the 5 electric body (w/md), f
is the circumferential mantissa (l-1z), E is the electric field strength (vA), and e
r is the relative permittivity 11L of the material, and tan δ is the dielectric loss angle of the material. Note that ξγtanθ is called a loss factor, and is a value specific to a material, and is a value that changes depending on temperature, other states of the material, and frequency.

The microwave irradiation time used in the heat sterilization of the present invention varies depending on the type, size, shape, etc. of the food to be heat sterilized, but is preferably 3 to 10 minutes.

According to the method of the present invention, the solid-liquid mixed food is completely packaged in a film and irradiated with the micro technique while immersed in hot water, so the temperature distribution of the liquid mixed food is uniform (therefore, the aF
When the food is heated to -, the moisture in the food turns into steam and the packaging film never ruptures.

Next, examples of the present invention will be shown.

A 110 g hamburger steak vacuum-packed with polystyrene film was used as a sample to be heat sterilized.

Autumn 293mm, ((t 191mm, 'M 82m
m, yongfl? <Pour 1400cc ft of water into a 4600cc polyethylene container and place it in a 7AL microwave oven (
The container was placed in a Toshiba ER-608F'S) and irradiated with microwaves to heat the water in the container to approximately 69°C.

Next, the sample was placed in hot water at about 69°C and then heated in the microwave for about 10 minutes, resulting in a temperature of 9.
At 0°C, the center of the sample reached 95°C. The sample was left in hot water for an additional 4 minutes at this temperature, but no expansion of the film in hot water was observed. Furthermore, even if a film-wrapped solid-liquid mixed food was quenched in cold water after heat sterilization using microwaves and the food was left at 8°C for 30 days, no change in flavor was observed, and the food was putrefied by bacteria. There was no.

Although the present invention has been described using a so-called batch method in which a solid-liquid mixed food is immersed in hot water using a household microwave oven and sterilized by heating with microwaves, the method of the present invention is not limited to this. Instead, for example, a solid-liquid mixed food placed on a belt conveyor in hot water must be conveyed through a long tunnel a゛! It can also be applied to a so-called continuous method of heat sterilization in a microwave heating device.

Claims (1)

[Claims] In a method of heating and sterilizing a solid-liquid mixed food using microwaves, the food is vacuum-packaged with a film that transmits microwaves, and then the food is immersed in a hot water tank, and the microwave is irradiated from outside of the hot water tank in this state. A heating sterilization method using microwaves, which is characterized by: