CN107494721B - A device and method for improving the uniformity of almond radio frequency sterilization - Google Patents

Abstract

The invention discloses a device and method for improving the uniformity of almond radio frequency sterilization, comprising a first layer of almond container, a second layer of almond container, a third layer of almond container, a fourth layer of almond container, and a fifth layer of almond container. It includes the following steps: sequentially place 5 layers of container positions; heat almond hot air for 3 minutes with assisted radio frequency heating; place 5 layers of containers in reverse order; heat almond hot air with assisted radio frequency for 3 min; stop radio frequency heating of almonds, keep warm with hot air at 72°C for 15 minutes; stop hot air heat preservation, and quickly cool down to room temperature. Adopting the present invention avoids the situation that the almonds at the corners of the containers are damaged due to excessive heating, and the almonds are heated more evenly during the radio frequency treatment.

Description

A device and method for improving the uniformity of almond radio frequency sterilization

technical field

The invention relates to the technical field of radio frequency sterilization of fruit seeds, in particular to a device and method for improving the uniformity of radio frequency sterilization of almonds.

Background technique

According to the United Nations Food and Agriculture Organization's statistical database (FAOSTAT), the output of almonds in six countries including the United States, Spain, Australia, Italy, Turkey and China ranks among the top in the world. Studies have shown that almonds contain high levels of unsaturated fatty acids such as linoleic acid and linolenic acid and vitamin E, and have high nutritional and medical values. Therefore, almonds are widely accepted and loved by consumers. At present, California, USA is the world’s largest supplier of almonds. During the harvesting of almonds, there are problems such as vibrating mature almonds from the trees, drying the almonds on the ground naturally, or transporting the dried almonds from the ground to trucks. Due to the contact between the almonds and the soil on the ground, irrigation water, and sprayed pesticides, the almonds are polluted by pathogenic microorganisms. At the same time, during the processing of almonds, such as peeling, shelling, packaging, transportation, sales and storage, etc., the pathogenic bacteria carried by almonds will survive for a long time. When the pathogenic bacteria are under suitable temperature and humidity conditions, they may multiply rapidly, posing potential hazards to the health of eaters. In addition, almonds infected with strong pathogenic bacteria such as Salmonella and Escherichia coli, even if the amount of contamination is small, will cause food safety problems after human consumption. Therefore, the contamination of pathogenic microorganisms in almonds has become a new food safety problem. At home and abroad, radio frequency sterilization technology is used to preserve and sterilize fruit seeds. Radio frequency heating can penetrate into the interior of the material, causing the oscillation and migration of charged particles inside the material, and converting electromagnetic energy into heat energy. Because radio frequency heating overcomes the limitation of traditional heat treatment, it can heat the inside and outside of almond at the same time to achieve the overall heating effect. Therefore, radio frequency heating technology has been used as a new heat treatment method for insecticide and sterilization because of its unique advantages such as strong penetrating power and fast heating speed. However, there is a problem of uneven heating at different positions during the radio frequency heating process. In the process of radio frequency treatment of almonds, due to the edge effect produced by radio frequency heating, the temperature at the edge of the almond container is the first to rise, causing the temperature of the almonds at the edge to be much higher than the temperature of the almonds at other places. Although the use of radio frequency heating technology will eventually kill harmful fungi such as Salmonella in almonds, the almonds at the edge have seriously damaged their nutritional value due to excessive heating. In view of this, it is an urgent problem to be solved by professionals in the industry to invent a device and method that can improve the heating uniformity of almond wood during radio frequency treatment.

Contents of the invention

The object of the present invention is to provide a device and method for improving the uniformity of almond radio frequency sterilization in view of the deficiencies in the prior art, so as to solve the existing problem of uneven heating of almonds in the radio frequency sterilization process.

The above object is achieved by the following technical solutions: a device for improving the uniformity of almond radio frequency sterilization of the present invention consists of five parts: a first layer of almond container, a second layer of almond container, a third layer of almond container, a fourth layer of almond container, and a fifth layer of almond container. Among them, the following steps are included:

Place 5 layers of containers in sequence: Weigh almonds of the same quality and put them into containers on each layer, place the first layer of almond container, the second layer of almond container, the third layer of almond container, the fourth layer of almond container, and the fifth layer of almond container vertically from top to bottom in the order of 1, 2, 3, 4, 5, and the container material is polypropylene or polyethylene.

Hot air assisted radio frequency heating of almonds for 3 minutes: Before starting the radio frequency treatment of almonds, turn on the hot air fan. After preheating for 1 hour, put the 5-layer container on the lower plate of the radio frequency equipment, turn on the radio frequency equipment, and use hot air assisted radio frequency heating to sterilize the almonds. The processing time of this process is about 3 minutes.

Place the 5-layer containers in reverse order: turn off the radio frequency equipment, and re-arrange the order of the 5-layer containers on the lower plate of the radio frequency equipment. Place the first layer of almond wood containers, the second layer of almond wood containers, the third layer of almond wood containers, the fourth layer of almond wood containers, and the fifth layer of almond wood containers vertically from top to bottom in the order of 5, 4, 3, 2, and 1.

Hot air assisted radio frequency heating of almonds for 3 minutes: Turn on the radio frequency equipment and continue to heat the almonds in the 5-layer container with hot air assisted radio frequency heating. The radio frequency treatment time for almonds in this process is also 3 minutes.

Stop the radio frequency heating of the almond and keep it warm with hot air at 72°C for 15 minutes: After the hot air assisted radio frequency heating of the almond in the 5-layer container reaches 6 minutes, turn off the radio frequency equipment, stop the radio frequency treatment of the almond, and only use the hot air at 72°C to continue to keep the almond warm for 15 minutes.

Stop the hot air heat preservation and quickly cool down to room temperature: quickly cool the almond wood after heat preservation treatment to room temperature.

Preferably, the capacity of the single-layer container is 30.0 long x 22.0 wide x 2.0 high cm³.

Preferably, the weight of the almond wood in each layer of the container is 0.3Kg, and the moisture content is 10.0%.

Preferably, the frequency of the radio frequency device is 27.12MHz, and the power is 6KW.

Preferably, the hot air blower will be turned on before the almond radio frequency treatment, and the temperature of the hot air blower is set to 72 degrees.

Preferably, the distance between the radio frequency plates is 12cm in the radio frequency sterilization method for the 5-layer almond wood container.

Preferably, the auxiliary temperature of the hot air is 72°C.

Preferably, the almond is cooled to room temperature by means of forced rapid cooling by a fan, and the wind speed is about 3.5m/s.

The remarkable advantage of the present invention is that it proposes to change the almond radio frequency sterilization of the whole layer container into the almond radio frequency sterilization of the 5-layer container, by changing the position arrangement sequence of the 5-layer container during the radio frequency heating process of the almond, and keeping it in hot air at 72°C for 15 minutes, thereby improving the heating uniformity of the almond. This method is not only simple and easy to operate, but also prolongs the storage time of the obtained almonds. More importantly, it avoids the damage of the nutritional value of the almonds at the corners of the container due to overheating, and has good practical performance and promotion prospects.

Description of drawings

Fig. 1 is a flow chart of steps of the present invention.

Fig. 2 is a structural schematic diagram of a 5-layer almond wood container device.

Fig. 3 is a structural schematic diagram of a traditional whole-layer almond wood container device.

FIG. 4 is a schematic structural diagram of a radio frequency device.

Detailed ways

The patent will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Fig. 2, a kind of device and method for improving the uniformity of almond radio frequency sterilization of the present invention are made up of the first layer of almond container 1, the second layer of almond container 2, the third layer of almond container 3, the fourth layer of almond container 4, and the fifth layer of almond container 5.

Specific working process: refer to Figure 1 and Figure 4;

Step S10: Arranging 5 layers of containers in sequence. First, the almond with a water content of 10% and a total weight of 1.5Kg is divided into 5 parts on average, and each part of 0.3Kg is put into a container on each layer. The capacity of each layer of container is 30.0 long x 22.0 wide x 2.0 high cm³. , 5. The sequence is placed vertically from top to bottom, and the material of the container is polypropylene or polyethylene.

Step S20: heat the almond wood with hot air for 3 minutes assisted by radio frequency. Turn on the hot air fan, set the temperature of the hot air fan to 72 degrees, and preheat for 1 hour. Then, put the 5-layer container on the lower plate of the radio frequency equipment, and start the radio frequency equipment to perform radio frequency hot air treatment on the almond. The frequency band of the radio frequency equipment is 27.12MHz, the distance between the radio frequency plates is 12cm, and the auxiliary hot air is 72°C. The radio frequency treatment time for the almond in this process is about 3 minutes.

Step S30: Arrange the positions of the 5-layer containers in reverse order. Then turn off the radio frequency equipment, and on the lower plate of the radio frequency, rearrange the order of the 5 layers of containers, and place the first layer of almond wood container 1, the second layer of almond wood container 2, the third layer of almond wood container 3, the fourth layer of almond wood container 4, and the fifth layer of almond wood container 5 vertically from top to bottom according to the order of 5, 4, 3, 2, and 1.

Step S40: heat the almond wood with hot air for 3 minutes with the aid of radio frequency. Turn on the radio frequency equipment and continue to heat the almond in the 5-layer container with hot air assisted radio frequency. The radio frequency treatment time for the almond in this process is about 3 minutes, and the temperature of the almond after treatment reaches 72 ℃.

Step S50: stop the radio frequency heating of the almond, and keep it warm with hot air at 72°C for 15 minutes. After the radio frequency heating time of the almond wood in the 5-layer container reaches 6 minutes, turn off the radio frequency equipment, stop the radio frequency treatment of the almond wood, and only keep the hot air at 72°C to continue the heat preservation of the almond wood for 15 minutes.

Step S60: stop the hot air heat preservation, and quickly cool down to room temperature. Finally, heat the almonds in the 5-layer container with hot air, then take them out and use a fan to quickly cool them down to room temperature, where the wind speed is about 3.5m/s.

The invention provides a group of control experiments to verify the effect of the method of the invention on improving the heating uniformity of the almond. The verification method refers to the heating uniformity index, which is the ratio of the standard deviation of the sample temperature to the average sample temperature rise within the processing time, that is, the smaller the heating uniformity index, the better the uniformity of the heating effect.

Control Experiment 1: Determination of Heating Uniformity Index

Experimental group 1.1: Determination of the uniformity index of radio frequency sterilization of almond wood in a 5-layer container

Select almonds with uniform maturity, put 0.3Kg almonds with a water content of 10% into one layer of containers, put 5 layers of containers (1.5Kg in total), and put the 5 layers of containers on the lower plate of the radio frequency equipment. Then, the heating uniformity index was compared under five different sterilization conditions: scheme 1, the almond wood of the 5-layer container was only heated by radio frequency; scheme 2, the almond wood of the 5-layer container was heated by hot air assisted radio frequency; scheme 3, the almond wood of the 5-layer container was heated by hot air assisted by radio frequency, and the single layer 4 and 5 were moved to the top of 1 during the radio frequency heating process; Change the sequence to 5, 4, 3, 2, 1; plan 5, heat 5 layers of almond wood with hot air-assisted radio frequency heating, and change the placement sequence of 1, 2, 3, 4, 5 to 5, 4, 3, 2, 1 during the radio frequency heating process, and heat it with 72°C hot air for 15 minutes.

Control group 1.2: Determination of the uniformity index of radio frequency sterilization and heating of the whole layer of container almond

Referring to Figure 3, select almonds with uniform maturity, put 1.5kg of almonds with a moisture content of 10% into a full-layer container with a capacity of 30.0 length × 22.0 width × 10 height cm³, and put the entire layer container on the lower plate of the radio frequency equipment. Then, the heating uniformity index was compared under 5 different sterilization conditions: scheme 1, 1.5kg almond wood in the whole container was heated by radio frequency only; scheme 2, 1.5kg almond wood in the whole container was heated with hot air assisted radio frequency; scheme 3, 1.5kg almond wood in the whole container was heated with hot air assisted radio frequency and stirred once; kg almonds were heated with hot air-assisted radio frequency, and stirred twice and kept at 72°C for 15 minutes with hot air.

Table 1 Determination of heating uniformity index of almond wood in five-layer container by radio frequency sterilization

Table 2 Determination of the uniformity index of the radio frequency sterilization heating of the whole container almond

As can be seen from the results of the comparative experiments in Table 1 and Table 2: a device and method for improving the uniformity of radio frequency sterilization of almonds according to the present invention, when using 5 layers of containers to carry out radio frequency sterilization treatment of almonds compared with that of whole layer containers to carry out radio frequency sterilization treatment of almonds, the heating uniformity index of the upper, middle and bottom layers of almonds under the 5 kinds of sterilization treatment conditions will be significantly reduced. Moreover, it can be seen from the experimental data under 5 kinds of sterilization conditions in the experimental group 1.1 that the heating uniformity index of almond is significantly lower than that of the other 4 schemes by adopting scheme 5, which shows that the device and method for improving the uniformity of almond radio frequency sterilization of the present invention are the best for improving the heating uniformity of almond.

Compared with the prior art, the present invention has substantive features and significant progress as follows:

The present invention changes the almond radio frequency sterilization of the whole container into the almond radio frequency sterilization of the 5-layer container, which improves the heating uniformity of the almond in the radio frequency sterilization process, thereby avoiding the damage of the nutritional value of the almond at the corner of the container due to excessive heating. This method is simple and convenient, and has good practical performance and popularization prospect.

Claims (1)

1. A method for improving the uniformity of almond radio frequency sterilization, characterized in that: the almond container is made up of the first layer of almond container 1, the second layer of almond container 2, the third layer of almond container 3, the fourth layer of almond container 4, and the 5th layer of almond container 5, wherein it comprises the following steps: Place 5 layers of containers in sequence: weigh almonds of the same quality and put them into containers on each layer, place the first layer of almond container, the second layer of almond container, the third layer of almond container, the fourth layer of almond container, and the fifth layer of almond container vertically from top to bottom in the order of 1, 2, 3, 4, 5, and the container material is polypropylene or polyethylene; Heat the almond with hot air assisted radio frequency for 3 minutes: turn on the hot air blower, and after preheating for 1 hour, put the 5-layer container on the lower plate of the radio frequency equipment, and use the hot air assisted radio frequency heating to sterilize the almond. The processing time of this process is 3 minutes; Place the 5-layer containers in reverse order: turn off the radio frequency equipment, and re-arrange the order of the 5-layer containers on the lower plate of the radio frequency equipment, and place the first layer of almond wood containers, the second layer of almond wood containers, the third layer of almond wood containers, the fourth layer of almond wood containers, and the fifth layer of almond wood containers vertically from top to bottom in the order of 5, 4, 3, 2, and 1; Hot air assisted radio frequency heating of almond for 3 minutes: Turn on the radio frequency equipment and continue to heat the almond hot air assisted radio frequency heating of the 5-layer container. The radio frequency treatment time for almond in this process is also 3 minutes; Stop the radio frequency heating of the almond, and keep it warm with hot air at 72°C for 15 minutes: After the hot air assisted radio frequency heating time of the almond in the 5-layer container reaches 6 minutes, turn off the radio frequency equipment, stop the radio frequency treatment of the almond, and only use the hot air at 72°C to continue to keep the almond warm for 15 minutes; Stop the hot air insulation and quickly cool to room temperature: quickly cool the almond wood after the heat preservation treatment to room temperature; The capacity of the single-layer container is 30.0 long x 22.0 wide x 2.0 high cm³; The weight of the almond wood in each layer of containers is 0.3Kg, the total weight is 1.5Kg, and the moisture content is 10.0%; The frequency of the radio frequency equipment is 27.12MHz, and the power is 6kW; Before starting the almond radio frequency treatment, the hot air blower should be turned on, and the temperature of the hot air blower should be set to 72°C; The radio frequency hot air pole plate spacing is 12cm in the radio frequency sterilization method carried out to 5 layers of almond wood containers; The hot air auxiliary temperature is 72°C; Described almond is cooled to room temperature and adopts the mode of forced rapid cooling of fan, and wind speed is 3.5m/s.