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Method for shortening processing time of microwave freezing drying of fruit or vegetable powder by utilizing dielectric core

A microwave freezing and core technology, applied in applications, food preservation, food preparation, etc., can solve the problems of reduced ability to absorb microwave energy, low dielectric coefficient, product overheating, etc., to achieve less residual microorganisms, high cost performance, and increased yield Effect

Inactive Publication Date: 2006-11-29
JIANGNAN UNIV
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  • Summary
  • Abstract
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  • Application Information

AI Technical Summary

Problems solved by technology

[0004] However, there are two major problems when simple microwave freeze-drying is used for the dehydration of high-moisture food raw materials: 1) After a large amount of water in the material is frozen, the water molecules are greatly constrained, so its dielectric coefficient is very low in the microwave field, such as at 2450MHz In the microwave field, its dielectric coefficient drops from 78.2 of water to 3.2 of ice (Tang, 2005), resulting in a rapid decline in its ability to absorb microwave energy. Therefore, pure microwave freeze-drying is currently limited to the dehydration of low-moisture food materials; 2) Due to the huge difference in the dielectric coefficient of ice and water, the microwave energy that is applicable to the frozen state of the material water becomes the sublimation interface of the material and thaws into water, which in turn becomes the heat source for overheating and coking of the product

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0014] Embodiment 1: Microwave vacuum freeze-drying strawberry powder production with dielectric core

[0015] Fresh strawberries (moisture content of 95% on a wet basis) are firstly selected, cleaned, destemmed, beaten, and treated with pectinase for 3 hours, added with high fructose syrup at an amount of 5g / kg, and concentrated in a vacuum until the moisture content of a wet basis is 50% %, implanted nano-titanium oxide ceramics with a dielectric coefficient of 80-100, cylinders with a size of 30×Φ20-30×Φ50mm, and placed symmetrically at intervals of 100mm-300mm; after freezing for 15 minutes at -36°C Carry out microwave vacuum freeze-drying (pressure 80Pa, microwave power 1600W within 0-2h, microwave power 800W within 2-3h, cold trap temperature -50°C), dehydrate to wet basis moisture content 6%, pulverize, pass through 80 mesh sieve, get Strawberry powder, packed and stored away from light. Drying took 3 hours.

Embodiment 1

[0016] Comparative Example 1, the production of microwave vacuum freeze-dried strawberry powder without a dielectric core: first, through selection, cleaning, destemming, beating, adding pectinase enzymolysis treatment for 3 hours, vacuum concentration to a moisture content of 50% on a wet basis, and Microwave vacuum freeze-drying (pressure 80Pa, microwave power 1600W within 0-4h, microwave power 800W within 4-8h, cold trap temperature -50°C) after freezing at -36°C for 15min, and dehydration to moisture content of 6 %, crushed, passed through an 80-mesh sieve to obtain strawberry powder, packaged, and stored away from light. Drying took 8 hours.

Embodiment 2

[0017] Embodiment 2: Microwave vacuum freezing white mushroom powder production with dielectric core

[0018] Fresh white mushrooms (moisture content on a wet basis: 92%) are first selected, cleaned, cut into pieces, blanched (100°C, 5 minutes), then cooled, added with an appropriate amount of water for beating, and refined table salt is added in an amount of 1.0g / kg. Concentrate in vacuum until the moisture content of the wet base is 50%, implant nano-titanium oxide ceramics with a dielectric coefficient of 80-100, and place them in a cylinder with a size of 30×Φ20-30×Φ50mm, with an interval of 100mm-300mm, symmetrically placed; at -40 After freezing for 10 minutes at ℃, carry out microwave freeze-drying (pressure 100Pa, 0~3h microwave power 1600W, 3~6h microwave power 800W, cold trap temperature -50℃), dehydrate to wet basis moisture content 8%, crushed over 80 Mesh sieve to get white mushroom powder, then pack and store. Drying took 6 hours.

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Abstract

A dielectric core method for shortening the time taken by microwave freeze-drying of fruit-vegetable powder includes such steps as choosing raw materials, conventional pre-treating, slicing, beating, adding the high-dielectric-constant titanium oxide ceramic nano-particles, amino acid and sugar or salt to form dielectric cores, quick freezing, microwave vacuum freeze-drying, and pulverizing. It features less loss of nutrients.

Description

technical field [0001] The invention discloses a method for shortening the microwave freeze-drying time of fruit and vegetable powder by adopting a dielectric inner core, which belongs to the technical field of fruit and vegetable food processing, relates to energy-saving processing of high-quality dehydrated fruits and vegetables, and is mainly used for energy-saving production of high-quality dehydrated fruits and vegetables. Background technique [0002] Vacuum freeze-drying (lyophilization for short) has become the most popular dehydration method for preserving heat-sensitive active substances in food and biological products due to the low temperature and the basically anaerobic condition of the whole process (Xu, Min and Mujumdar, 2004). However, due to the low electric heat transfer efficiency of ordinary freeze-drying, it often takes a long time to dehydrate food with high moisture content, so its operating cost is high (Zhang Min et al., 2001); in addition, various ha...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): A23L1/212A23L3/44A23L3/36A23L19/00
Inventor 张慜段续范柳萍
Owner JIANGNAN UNIV
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