Dehydrated Vegetables

Dehydrated Vegetables Detail Introduction

We are professional dehydrated vegetable suppliers to provide you with the following guidance on dehydrated vegetables.

1. What are dehydrated vegetables?

Dehydrated vegetables are a kind of dried vegetables made after artificial heating to remove most of the water in the vegetables, which can be recovered by submerging them in water before consumption and retaining the original color, flavor, and nutrients of fresh vegetables. Specifically, vegetable dehydration means that vegetables are dried after dehydration, which reduces the water content and increases the range of soluble substances in vegetables while essentially inhibiting the breeding of microorganisms and reducing the activity of enzymes, making it possible to extend the storage period at room temperature and meet the needs of the people for vegetables under unfavorable storage conditions.

The main features of dehydrated vegetables
Small size, lightweight, will recover when immersed in water, easy to transport and eat, and most importantly, retain the original nutritional value.

2、What are the vegetables suitable for dehydration?

Suitable vegetables for dehydration include wood ear, shiitake mushroom, pepper, yellow cauliflower, dried bamboo shoots, yucca slices, etc.

3、Basic principle of vegetable dehydration

The majority of vegetable products spoilage is the result of microbial multiplication. A large amount of water and nutrients in vegetables is the material basis for microbial reproduction, and microorganisms keep growing under suitable conditions, causing vegetable decay. In addition, the vigorous respiration of vegetables after harvesting will gradually consume the nutrients and eventually lose their edible value. The process of vegetable dehydration is the process of evaporation and drying of water in raw materials. Fresh vegetables contain a large amount of water, generally 75% to 95%. The water contained in the vegetables, according to its state of existence, is divided into combined water and free water, two categories, which is combined with the vegetable tissue starch and protoplasm and other substances mixed into colloidal water, free water is free to state exists in the vegetable tissue. Binding water is colloidal water with the role of swelling produced; only under high temperature drying conditions can it be discharged

4、How are the raw materials for dehydrated vegetables processed?

Raw materials before drying to remove diseases and insects, rotten, dried parts, and melons to seeds and flesh. Other types of vegetables can be rinsed clean with water to remove surface dirt and mud and keep products sanitary, improving the appearance and enhancing product quality. It can be manually cleaned or mechanical cleaning to ensure that the raw materials meet the requirements of dry processing. Then put in an excellent place to dry. It should not be exposed to the sun. Some vegetable raw materials, such as potatoes, garlic, carrots, etc., should be removed from the skin before drying to improve the quality of products and make the water easy to evaporate and promote drying. Peeling methods are manual peeling, mechanical peeling, thermal peeling, and chemical peeling. The chemical peeling method uses 1% to 2% sodium hydroxide at room temperature or boiling water treatment 5 ~ 10min can be. Modern dried vegetable processing of raw materials has been generally used to cut the processing of mechanized operation, or with a fixed knife by manual process, so that the raw materials cut consistent. The raw materials are cut into slices, strips, grains, shreds, etc., is to adapt to the edible requirements to facilitate the evaporation of water. In the cutting process, bell peppers, onions and garlic, and other vegetables containing colloidal mucus varieties should also be cleaned and bleached to remove most of the mucus to ensure the looseness of the product and prevent the color from deepening or discoloration, making the product more beautiful.

5、How is the color protection process for dehydrated vegetables carried out?

This process is crucial in vegetable drying, which directly affects the appearance quality of dried vegetable products and plays an essential role in maintaining the nutritional value of the products. Color protection includes controlling non-enzymatic browning and avoiding enzymatic browning and decolorization and coloring. Commonly used color protection methods mainly include hot bleaching, acid treatment, etc.

Hot bleaching, also known as hot blanching, pre-boiling, greening, etc., is a short heat treatment and rapid cooling process; it is the most commonly used method to control enzymatic browning. It is considered an essential process of vegetable drying processing. The key is the scalding and bleaching process to maintain a stable water temperature. Commonly used scalding and bleaching methods are boiling water blanching and steam hot blanching two kinds, the temperature is 95 ~ 100 ℃. To strengthen the effect of color protection, cooking water hot blanching can also add 0.1% to 0.3% sodium carbonate or sodium bicarbonate, 0.1% to 0.5% citric acid, 0.1% calcium chloride, or sodium chloride, and other food additives according to different vegetables. Hot blanching solution by adding 0.05% zinc chloride as a color guard to add sodium chloride or sodium bicarbonate alone is more conducive to the protection of chlorophyll.

Hot blanching time depends on the vegetables' type, shape, and size. To blunt the enzyme activity as a condition, as short as possible, time is generally 2 ~ 8min, to vegetable leaves become translucent or raw materials slightly soft as appropriate. Remove the raw materials immediately after hot scalding and cool them with cold water or cold air to prevent excessive hot scalding. If the hot scalding is not complete, enzymatic browning will occur, generally to the degree of peroxidase inactivation, to test whether the hot blanching is appropriate. The method is to cut the raw material after hot blanching and a few drops of 0.1% guaiacol or benzidine and 0.5% hydrogen peroxide on the cut surface, respectively. If it turns brown or blue, the hot scalding is not enough; if it does not change color, the enzyme has lost activity.

The acid treatment method uses citric acid, malic acid, phosphoric acid, and ascorbic acid for chemical color protection treatment because the hydrogen ions dissociated from the acid reduce the pH of the material and control the activity of polyphenol oxidase. Because the optimum pH of polyphenol oxidase is 6~7, the movement of polyphenol oxidase will be significantly reduced when the pH is <4, thus providing the effect of color protection. In addition, a solution consisting of 5.0% NaCl, 0.05% phosphoric acid, and 0.05% VC was used to treat tomatoes to achieve the desired color protection effect.

6、What is the drying method of dehydrated vegetables

There are mainly natural drying, hot air drying, and vacuum freeze-drying methods for vegetable drying.

Natural drying is the method of drying vegetables under natural conditions, using solar radiation energy, hot air, etc. Thus, it can be divided into two forms of sun-drying and shade-drying. Different vegetable varieties should set up a dehydration drying rack or sunbed; the drying rack should be built with the wind and easy to ventilate. Suitable for shade-drying sorts should choose a cool and ventilated site or make a shade shed. Grains, blocks, slices suitable for drying bed dehydration can build multi-layer sunbed. The strips are ideal for drying and hanging on the drying rack.

Natural dewatering is simple, easy to manage, and low cost. Natural dehydration mainly relies on external conditions such as temperature and humidity. The quality is not easy to control; when the temperature is high, some vegetables have not yet reached the dehydration requirements of local mold. Some vegetables in the high-temperature sunlight are easy to read ferment. Some vegetables lose color seriously, and it isn't easy to form good products. At present, most rural and mountainous areas are still commonly used natural drying methods to produce peppers, dried bamboo shoots, golden needles, shiitake mushrooms, mushrooms, fungus, etc...

Hot air drying usually uses a tunnel-type hot air drying machine for dewatering and drying. The spreading sieve lays the processed materials flat on a bamboo or stainless steel mesh sieve. The baking sieve is primarily rectangular. The available size is 1.0m×1.0m×0.5m, and the sieve hole is 6mm×6mm. Each baking sieve is 2~5kg, depending on different vegetable species. Loading will lay the material of the baking sieve loaded into the material baking frame. What can push the loaded baking car into the drying room along the ground track for dewatering and drying? Every specific time that is incremented from the import of the drying room one load baking car and unloaded from the export of 1 load baking car that has completed dewatering. So continuous dewatering operation, one drying room can generally accommodate 8~9 sets of laden drying carts. The drying room temperature is usually controlled at about 60℃, generally not more than 65℃, and can be completed in 6~8h. The temperature is too high due to sudden high temperature resulting in the rapid expansion of the juice in the material tissue, resulting in the loss of contents, crystallization, scorching, etc. Fruits and vegetables rich in sugar and volatile substances are also suitable for dehydration at lower temperatures.

Vacuum freeze-drying is the material of vegetables drained of water quickly and sharply frozen, and then put into the vacuum container with the help of a vacuum system to reduce the pressure inside the nest to below the three-phase point, and supply heat to the material by the heating system so that the material moisture gradually evaporates until dried to the endpoint of humidity. In vacuum freeze-dried, dehydrated vegetables, the key lies in the pre-freezing and sublimation procedures. The pre-freezing temperature is generally decided according to the eutectic point of the material; that is, the pre-freezing temperature should be 5~10℃ lower than the eutectic point temperature. The eutectic point temperature of vegetables is when the structural water in vegetables is frozen. Generally, after 2~3h or a longer time, it can reach the freezing temperature and then keep warm for 1~2h to make it freeze through. Sublimation drying is the longest stage of the whole vacuum freeze-drying process, this stage needs to heat the materials, and the heat required for different materials is different.