CN1868321A - Method for shortening processing time of microwave freezing drying of fruit or vegetable powder by utilizing dielectric core - Google Patents

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

A kind of employing band dielectric core shortens the microwave freezing drying of fruit or vegetable powder time method

Technical field

A kind of employing band dielectric core shortens the microwave freezing drying of fruit or vegetable powder time method, belongs to the fruit-vegetable food processing technique field, relates to the energy-conservation processing of high-quality dehydrated fruits and vegetables, is mainly used in the energy-conservation production of high-quality dehydrated fruits and vegetables.

Background technology

Owing to adopt the basic oxygen free condition of low temperature and whole process, vacuum freeze drying (abbreviation freeze-drying) has become preserves the most popular dewatering type (Xu, Min andMujumdar, 2004) of temperature-sensitive active material in food and the biological products.But because the fax thermal efficiency of common freeze-drying is lower, the high-moisture percentage food-dewatering often needs long time, so the high (Zhang of its operating cost Min etc., 2001); In addition, various harmful microorganisms (bacterium, gemma, mould, worm's ovum, pathogenic bacteria etc.) are when adhering to freeze-drying prods, its survival rate very high (Liu Zhisheng, Lee repair canal, 1998).Easily remaining having become of the sky high cost of product and microorganism influences the further fast-developing maximum restraining factors of this frozen dried food industry, accelerates efficient, the safe freeze drying process of research and development and become common recognition in the industry.According to external (Arsem and Ma, 1990), fruits and vegetables freeze-drying dewatering time is if can shorten half, and then energy consumption and production cost all can reduce more than 1/3.Therefore improving its freeze-drying dewatering efficiency also is the focus that this field is studied in the world.

In order to improve freeze-drying speed and control harmful microorganism, in freeze-drying process, adopt microwave to substitute the traditional electrical heating, formed auxiliary freeze-drying (abbreviation microwave freeze-dry) technology of microwave, more existing research report (Copson and Decareau, 1957 both at home and abroad; Ben Souda, Akyel and Bilfen, 1989; Wangand Shi, 1998; 1999).Microwave freeze-dry not only can improve dewatering speed but also can suppress harmful microorganism to a certain extent, thereby has remarkable superiority.

But simple microwave freeze-dry has two hang-ups when being used for the dehydration of high moisture content raw-food material: 1) because after the material large quantity of moisture freezes, hydrone is subjected to very big constraint, therefore its dielectric coefficient is very low in microwave field, drop to 3.2 (Tang of ice from 78.2 of water as its dielectric coefficient in the 2450MHz microwave field, 2005), cause its also very fast decline of ability that absorbs microwave energy, therefore simple microwave freeze-dry only is confined to the dehydration of low moisture raw-food material at present; 2) because there are greatest differences in the ice and the dielectric coefficient of water, often the microwave energy that is suitable in the material moisture frozen state becomes the material interface that distils and separates and be frozen into water, and then becomes that product is overheated, the thermal source of coking.Therefore studying various lots of high-moisture raw-food material is keeping the rapid microwave freeze drying process under the stay in grade condition significant.

Summary of the invention

The object of the present invention is to provide a kind of employing band dielectric core to shorten the microwave freezing drying of fruit or vegetable powder time method, when carrying out microwave freeze-dry at the fruits and vegetables of high-moisture percentage, ice absorbs the low characteristics of microwave ability, the high dielectric core of artificial adding forms internal heat resource, thereby cut down the consumption of energy significantly and the production cycle, reduce the dehydration processing cost with this.

Technical solution: because after the material large quantity of moisture freezes, hydrone is subjected to very big constraint, so its dielectric coefficient is very low in microwave field, cause its also very fast decline of ability that absorbs microwave energy, therefore simple microwave freeze-dry only is confined to the dehydration of low moisture raw-food material at present.For the fruit-vegetable food of high-moisture percentage,, can add other polar molecule and obtain inner additional heating source for improving its microwave freeze-dry dewatering speed.This key problem in technology is to treat how freeze-dried material adopts preliminary treatment to form dielectric core, optimizes band dielectric core microwave freeze-drying technology.

Main process for fruit and vegetable materials is chosen, conventional preliminary treatment (clean, peeling (nuclear, the base of a fruit), section (fourth, grain), blanching etc.), making beating, enzymolysis, dielectric core formation processing, quick-frozen, microwave vacuum freeze drying, pulverize fruits and vegetables powder, packing and storage.

Dielectric core forms to be handled: to the pulpous state fruits and vegetables before the quick-frozen moulding, the implantation dielectric coefficient is 80～100 nanometer titanium oxide ceramic formation dielectric core, nanometer titanium oxide ceramic is of a size of the cylinder of 30 * Φ, 20～30 * Φ 50mm, spacing distance 100mm～300mm, and symmetry is put; And add amino acid, sugar or salt in the pulpous state fruits and vegetables before the pre-freeze moulding, and the formation dielectric coefficient is 10～80 dielectric core, and addition is 1～20g/kg, and dielectric constant adopts based on resonant cavity perturbation method to measure.

Quick-frozen: the pulpous state fruits and vegetables after dielectric core form to be handled are loaded on charging tray, carry out quick-frozen, quick freezing temperature-36～-40 ℃, time 10-15min.

The microwave vacuum freeze drying: pressure 40～80Pa, microwave power 800～1600W, drying time 3～7h.

Beneficial effect of the present invention: the present invention adopts the method for band dielectric core microwave vacuum freeze drying and dehydrating, reaches to produce suitable additional heating source, shorten the product dewatering time significantly.And the product residue microorganism is few, and doing back freeze-drying prods best in quality and common does not have difference substantially.Therefore, adopt the inventive method to help improving occupation rate of market guaranteeing significantly to reduce the dehydration processing cost under the product quality premise with high cost performance.

Compare shortcoming such as the present invention has avoided that the product shr is big, rehydration is poor, the easy brown stain of color and luster, nutritional labeling loss are big with the traditional heated air drying technology.

Compare with common conduction heating or common microwave vacuum freeze dry technology (not being with dielectric core), the present invention has overcome long, shortcomings such as heating is uneven, product partly melts, coking drying time, and product quality still keeps higher level.The final time that has shortened vacuum freeze drying greatly, shortened the production cycle, thereby overcome operation energy consumption cost height, long shortcoming of production cycle,, also reduced the equipment depreciation cost of producing indirectly because the output of (1 year) increases substantially in the unit interval.

The specific embodiment

Embodiment 1: the dry strawberry powder production of band dielectric core microwave vacuum freeze

Fresh strawberry (wet basis moisture content 95%) is at first through choosing, clean, go the base of a fruit, making beating, add pectinase enzymatic hydrolysis and handle 3h, add high fructose syrup, addition is 5g/kg, and vacuum is concentrated into wet basis moisture content 50%, the implantation dielectric coefficient is 80～100 nanometer titanium oxide ceramic, be of a size of the cylinder of 30 * Φ, 20～30 * Φ 50mm, spacing distance 100mm～300mm, symmetry is put; After freezing 15min ,-36 ℃ sharp freezing rooms carry out microwave vacuum freeze drying (pressure 80Pa, microwave power 800W in the microwave power 1600W in 0～2h, 2～3h, condenser temperature-50 ℃), dewater to wet basis moisture content 6%, pulverize, cross 80 mesh sieves, get strawberry powder, packing, lucifuge storage.Dry 3 hours consuming time.

Comparative examples 1 is not with the dry strawberry powder production of the microwave vacuum freeze of dielectric core: at first through choosing, clean, go the base of a fruit, making beating, add pectinase enzymatic hydrolysis and handle 3h, vacuum is concentrated into wet basis moisture content 50%, carries out microwave vacuum freeze drying (pressure 80Pa after-36 ℃ sharp freezing rooms freeze 15min, microwave power 800W in the microwave power 1600W in 0～4h, 4～8h, condenser temperature-50 ℃), dewater to wet basis moisture content 6%, pulverize, cross 80 mesh sieves, get strawberry powder, packing, the lucifuge storage.Dry 8 hours consuming time.

Embodiment 2: band dielectric core microwave vacuum freeze white mushroom powder is produced

Fresh white mushroom (wet basis moisture content 92%) at first through choosing, (100 ℃ of cleanings, stripping and slicing, blanching, 5 minutes), cooling then adds the suitable quantity of water making beating, adds table salt, addition is 1.0g/kg, vacuum is concentrated into wet basis moisture content 50%, and the implantation dielectric coefficient is 80～100 nanometer titanium oxide ceramic, is of a size of the cylinder of 30 * Φ, 20～30 * Φ 50mm, spacing distance 100mm～300mm, symmetry is put; After freezing 10min ,-40 ℃ sharp freezing rooms carry out microwave freeze-drying (pressure 100Pa, 0～3h microwave power 1600W, 3～6h microwave power 800W, condenser temperature-50 ℃), dewaters, pulverized 80 mesh sieves to wet basis moisture content 8%, get the white mushroom powder, then the packing storage.Dry 6 hours consuming time.

Comparative examples 2, be not with the production of dielectric core microwave vacuum freeze white mushroom powder: fresh white mushroom (wet basis moisture content 92%) at first through choosing, (100 ℃ of cleanings, stripping and slicing, blanching, 5 minutes), cooling then, add the suitable quantity of water making beating, be concentrated into wet basis moisture content 50%, after freezing 10min ,-40 ℃ sharp freezing rooms carry out microwave freeze-drying (pressure 100Pa, 0～5h microwave power 1600W, 5～11h microwave power 800W, condenser temperature-50 ℃), dewater to wet basis moisture content 8%, pulverized 80 mesh sieves, got the white mushroom powder, then the packing storage.Dry 11 hours consuming time.

Embodiment 3: band dielectric core microwave vacuum freeze seasoning wild cabbage powder is produced

Fresh wild cabbage (wet basis moisture content 88%) at first through choosing, (100 ℃ of cleanings, cutting, blanching, 3 minutes), cooling then adds the suitable quantity of water making beating, adds cysteine and table salt, addition is respectively 19g/kg and 1.0g/kg, be concentrated into wet basis moisture content 50%, the implantation dielectric coefficient is 80～100 nanometer titanium oxide ceramic, is of a size of the cylinder of 30 * Φ, 20～30 * Φ 50mm, spacing distance 100mm～300mm, symmetry is put; After freezing 13min ,-38 ℃ sharp freezing rooms carry out microwave freeze-drying (pressure 100Pa, 0～3h microwave power 1600W, 3～7h microwave power 800W, condenser temperature-50 ℃), dewaters, pulverized 80 mesh sieves to wet basis moisture content 8%, get the wild cabbage powder, then the packing storage.Dry 7 hours consuming time.

Comparative examples 3: be not with the production of dielectric core microwave vacuum freeze wild cabbage powder: fresh wild cabbage (wet basis moisture content 88%) at first through choosing, (100 ℃ of cleanings, cutting, blanching, 3 minutes), cooling then, add the suitable quantity of water making beating, be concentrated into wet basis moisture content 50%, after freezing 13min ,-38 ℃ sharp freezing rooms carry out microwave freeze-drying (pressure 100Pa, 0～5h microwave power 1600W, 5～10h microwave power 800W, condenser temperature-50 ℃), dewaters, pulverized 80 mesh sieves to wet basis moisture content 8%, get the wild cabbage powder, then the packing storage.Dry 10 hours consuming time.

Claims (1)

1. one kind is adopted the band dielectric core to improve the method for fruits and vegetables microwave freeze-drying speed, its main process is: fruit and vegetable materials is chosen, clean peeling stoning and/or go the conventional preliminary treatment of the base of a fruit, section, blanching, making beating, enzymolysis, dielectric core forms handles quick-frozen, microwave vacuum freeze drying, pulverize the fruits and vegetables powder, the packing and the storage; It is characterized in that:

Dielectric core forms to be handled: to the pulpous state fruits and vegetables before the quick-frozen moulding, the implantation dielectric coefficient is 80～100 nanometer titanium oxide ceramic formation dielectric core, nanometer titanium oxide ceramic is of a size of the cylinder of 30 * Φ, 20～30 * Φ 50mm, spacing distance 100mm～300mm, and symmetry is put; And add amino acid, sugar or salt in the pulpous state fruits and vegetables before the pre-freeze moulding, and forming dielectric coefficient is the dielectric core of 10-80, addition is 1～20g/kg;

Quick-frozen: the pulpous state fruits and vegetables after dielectric core form to be handled are loaded on charging tray, carry out quick-frozen, quick freezing temperature-36～-40 ℃, time 10～15min;

The microwave vacuum freeze drying: pressure 40～80Pa, microwave power 800～1600W, drying time 3～7h.