CN1294842C - Former hot blast and latter vacuum microwave combining drying process of producing crisp fruit and vegetable grains - Google Patents

Abstract

The invention discloses a method for preparing granulated fruit and vegetable brittle grains by combined drying with vacuum and microwave in the early stage of hot air and later stage, and belongs to the technical field of fruit and vegetable food processing. The main process of the present invention is: first take a certain amount of fruit and vegetable raw materials such as vegetables, fruits, beans, etc., after cleaning, arranging and dicing, blanching to kill enzymes (90-100° C.), draining after cooling with running water, and then draining them with or without After quick-freezing (-20～-30℃), frozen storage for later use (-15～-20℃), thawing, soaking and seasoning (about 1 hour), draining and hot air pre-dehydration (60～70℃, wind speed 1~3m/s) to obtain semi-finished products (moisture content 40~60%), and finally carry out vacuum microwave drying (-90~-96kPa, 2000~3500W) to obtain finished products (moisture content 2~5%). The present invention adopts a new process of firstly soaking and flavoring granular fruits and vegetables to balance the internal polar solutes, and then performing atmospheric pressure hot air drying and vacuum microwave subsequent joint drying. The nutritional components and color of the crispy fruit and vegetable products are well maintained, and the texture of the product is crisp and crisp. , and there is no problem of high oil content and greasy taste of fried food, and the production cost is far lower than that of vacuum freeze-dried products. It has the characteristics of short production cycle, low cost and good product quality.

Description

Method for preparing granular fruit and vegetable crisps by combined drying with vacuum microwave in the early stage of hot air and later stage

technical field

A method for producing granular fruit and vegetable crisps by soaking granular fruits and vegetables for seasoning to balance internal polar solutes, and then adopting the process of hot air drying in the early stage and vacuum microwave combined drying in the later stage, belonging to the technical field of fruit and vegetable food processing and related to the field of fruit and vegetable dehydration processing .

Background technique

Fruit and vegetable dehydration is an important part of the field of fruit and vegetable processing. The conventional dehydration of fruits and vegetables consumes a lot of heat energy, and there is a high temperature process, which causes a large loss of nutrients in fruits and vegetables. Therefore, high energy consumption and serious impact on product quality are the two most important problems in the dehydration process of fruits and vegetables.

Hot air drying is a traditional drying method, which is still widely used today. But there are obvious defects: the drying speed is fast in the early stage and slow in the later stage; high temperature; long heating time; large loss of nutrients; serious shrinkage; poor brittleness.

Vacuum freeze-drying is currently considered to be the best drying method to maintain the nutritional content and color of the product, but there are large one-time investment; large equipment footprint; large production energy consumption; long production cycle; Defects such as hidden dangers of microbial excess.

Although vacuum fried food has certain advantages in terms of cost, color, and nutrient preservation rate, there are (20-40)% of the oil that cannot be removed. Based on the scientific theory that "eating fried food is harmful to the body", vacuum Fried foods have not always been widely accepted.

Vacuum microwave drying is a new type of drying technology. It has the advantages of fast drying speed, less damage to food nutrients, basically maintaining the original color and flavor, and can produce an ideal puffing effect, making the product crispy and delicious. In recent years, there have been many researches on the application of vacuum microwave drying technology. The patent publication number CN1547951A adopts microwave drying fresh razor clam series food, and the patent publication number CN1530035A produces crispy red peppers with stuffing through microwave drying. color, aroma, taste and various nutrients, but because microwave equipment works under vacuum conditions, it belongs to a closed dry space with poor moisture removal capacity, and the moisture evaporated from the material cannot be discharged in time and re-condenses on the inner wall of the equipment And the surface of the material, the drying load is even greater, and it cannot meet the dehydration requirements of materials with high moisture content.

In order to solve the problem that the vacuum microwave drying equipment load is too large due to the high initial moisture content of the material, which is not conducive to popularization, Guixing (2000), Medeni Maskan (2001), Ana Andres (2004) combined microwave and hot air to dry American ginseng, kiwi fruit, and apples. The technology has been researched to better solve this problem. However, the above research is to integrate the hot air and microwave dryers on the same equipment, which is very difficult to use in actual production.

Xu Yanyang (2004) conducted a test of drying cabbage combined with hot air and vacuum microwave, successfully separated the hot air equipment and vacuum microwave equipment, achieved the purpose of greatly shortening the drying time and improving the drying quality of the product, but due to the cabbage ( Leafy vegetables) have more wrinkles after AD, and the distribution of polar solutes is uneven, resulting in uneven microwave absorption intensity at different parts of the material. Therefore, the material is prone to coking in the subsequent vacuum microwave drying, and the quality is difficult to control.

Contents of the invention

The purpose of the present invention is to provide a method for producing granular fruit and vegetable brittle grains by soaking granular fruits and vegetables for seasoning to balance the internal polar solutes, and then adopting the process of hot air drying in the early stage and vacuum microwave combined drying in the later stage, which involves dehydration processing of fruits and vegetables and can be used Used in the processing of various granular fruits and vegetables.

Technical solution: The main process of making fruit and vegetable crisps is: first take a certain amount of fruit and vegetable raw materials such as vegetables, fruits, beans, etc., and then wash, arrange and cut into cubes, blanch to kill enzymes (90-100°C), and cool with flowing water After draining, after quick freezing (-20～-30°C), frozen storage (-15～-20°C), and thawing process with or without quick freezing (-20～-30°C), soaking and seasoning (preparation of seasoning liquid according to taste, seasoning liquid: the quality of fruit and vegetable particles The ratio is 1:1, soaking time is about 1 hour) to balance the internal polar solutes of fruit and vegetable particles, and after draining, hot air pre-dehydration (60-70°C, wind speed 1-3m/s) to obtain semi-finished products (moisture content is 40-3m/s). 60%), and finally carry out vacuum microwave drying (-90～-96kPa, 2000～3500W) to obtain the finished product (moisture content is 2～5%).

The invention uses soaking and seasoning treatment to balance the polar solute inside the fruit and vegetable particles, so that all parts of the material absorb microwave energy in a balanced manner during the vacuum microwave drying process, and dry synchronously, which solves the problem that coking phenomenon is easily generated in the subsequent vacuum microwave drying.

In the present invention, the granular fruits and vegetables are dried with hot air in the convection oven in the early stage, and about 50% of the water in the fruits and vegetables is removed, which greatly reduces the drying load of the vacuum microwave dehydration equipment in the later stage, thereby further reducing the requirements for the moisture removal capacity of the production equipment. Reduce the cost of equipment introduction.

The present invention adopts the late-stage vacuum microwave drying technology to reduce the dehydration temperature, reduce the damage to the nutritional components of food, and maintain the original color and flavor. The unique mass transfer and heat transfer methods of vacuum microwave drying make granular fruits and vegetables produce more ideal The puffing effect makes up for the shrinkage caused by hot air drying in the early stage, so that the fruit and vegetable particles basically return to their original shape and are crispy and delicious, overcoming the problem of poor quality of conventional hot air drying products. Microwave has a bactericidal effect, which solves the problem of the hidden danger of microorganisms exceeding the standard.

Beneficial effects of the present invention: the materials targeted by the present invention are granular fruits and vegetables with a relatively small surface area, and the internal polar solutes are balanced by soaking the granular fruits and vegetables for seasoning, followed by hot air drying (60-70°C, wind speed 1-3m/s) Dehydration in the early stage, when the moisture content reaches 40-60%, transfer to vacuum microwave drying equipment for post-vacuum microwave dehydration (-90 ~ -96kPa, 2000 ~ 3500W), and the moisture content of the final product is 2 ~ 5%.

Compared with the background technology of poor quality of traditional hot air drying products, the present invention adopts the technology of vacuum microwave drying in the later stage, the high vacuum reduces the boiling point of water, the dehydration temperature decreases, the damage to food nutrients is less, and the original color and flavor are maintained; The unique mass transfer and heat transfer methods of microwave drying make granular fruits and vegetables produce an ideal puffing effect, make up for the shrinkage caused by hot air drying in the early stage, and make the fruit and vegetable particles basically restore their original shape and crispy and delicious; overcome the conventional hot air drying products. Large loss of nutrients, large shrinkage and deformation, hard crust on the surface and other quality deterioration phenomena.

Compared with the background technology of vacuum freeze-drying, the equipment used in the present invention has small footprint, low one-time investment, low energy consumption and other operating costs. hidden dangers.

Compared with the background technology of vacuum frying, the present invention does not have the disadvantage of high fat content.

Compared with the vacuum microwave dehydration background technology studied by the predecessors, the present invention uses granular fruits and vegetables as raw materials. Since the microwave contact surface of the granular fruits and vegetables is small, the difference in the distribution of polar solutes in each part is not large. The method of soaking and seasoning the fruits and vegetables makes the polar solutes in each part of the material more balanced, and solves the problem of easy coking in the subsequent vacuum microwave drying; , The method of removing about 50% of the water in fruits and vegetables greatly reduces the drying load of the vacuum microwave dehydration equipment in the later stage, thereby further reducing the requirements for the dehumidification capacity of the production equipment and reducing the cost of equipment introduction.

In a word, compared with the background technology, the present invention effectively reduces the investment cost, shortens the dehydration time, and improves the nutrition of the product by soaking the granular fruits and vegetables in seasoning to balance the internal polar solutes, hot air dehydration in the early stage, and vacuum microwave drying in the later stage. And the appearance quality increases the added value of the product. The product has a unique texture and flavor, which is a comprehensive effect that cannot be achieved by other drying methods, and has a significant application prospect.

Detailed ways

Embodiment 1: the production of edamame crisps

Fresh edamame clipping, selection, shelling, cleaning, blanching to kill enzymes (95°C, 2 minutes), cooling in running water, draining, quick freezing (-30°C quick-freezing tunnel, the central temperature is less than -18°C within 5 minutes), (-18～-20℃) Frozen storage, thawing, soaking seasoning (3% salt water, monosodium glutamate, aniseed, etc. according to taste, seasoning liquid: edamame mass ratio = 1:1, 1 hour), draining, hot air pre-dehydration (60-70°C, wind speed 1-3m/s) to a moisture content of about 45%, vacuum microwave drying (-90-96kPa, 2000-3500W) to a final moisture content of 2-5%, packaged and finished.

Embodiment 2: the production of crisp carrot White granulated sugar, seasoning liquid: carrot mass ratio = 1:1, 1 hour), drain, hot air pre-dehydration (60-70°C, wind speed 1-3m/s) to about 50% moisture content, vacuum microwave drying (- 90～-96kPa, 2000～3500W) to a final moisture content of 2～5%, packaged and finished.

Embodiment 3: the production of sweet corn crisp

Fresh sweet corn, threshing, selection, cleaning, blanching to kill enzymes (90°C, 1.5 minutes), cooling in running water, soaking and seasoning (1% salt, 2% white sugar, 5% maltodextrin, seasoning liquid: sweet corn kernels Mass ratio = 1:1, 1 hour), drain, hot air pre-dehydration (60~70℃, wind speed 1~3m/s) to about 50% moisture content, vacuum microwave drying (-90~-96kPa, 2000~3500W ) to a final moisture content of 2 to 5%, packaged and finished.

Claims (1)

1. A method for preparing granulated fruit and vegetable brittle grains by combined drying of hot air in the early stage and vacuum microwave in the later stage. The main process is: first take a certain amount of fruit and vegetable raw materials that can be diced and cleaned, diced, blanched to kill enzymes, and flow Drain after water cooling, after quick-freezing, frozen storage for later use and thawing with or without immersion and seasoning treatment, after draining, hot air drying, and finally vacuum microwave drying to obtain the finished product; it is characterized by soaking and seasoning granular fruits and vegetables Then adopt the process of hot air drying in the early stage and vacuum microwave combined drying in the later stage; Soaking and seasoning: the mass ratio of seasoning liquid: fruit and vegetable particles is 1:1, and the soaking time is 1 hour; Hot air drying in the early stage: the temperature of the hot air is 60-70°C, the wind speed is 1-3m/s, and the wet basis moisture at the conversion point of the fruit and vegetable drying method is 40-60%; Post-stage vacuum microwave drying: the vacuum degree is -90~-96kPa, the microwave power is 2000~3500W, and the moisture content of the final product is 2~5%.