Admin
Blanching is a method of heat treatment of raw materials

Blanching of fruit and vegetable raw materials is called short-term heat treatment at a certain temperature in water, steam or in aqueous solutions of salts, sugar, organic acids, alkalis.

Blanching is a very important preliminary operation, on which product quality and production losses largely depend. Translated into Russian, blanching means bleaching (from the French word blanchir — to bleach). However, depending on the type of raw material, the manufacturing technology of certain canned food, blanching is used for different purposes with the achievement of various results, the main of which are: cessation of biochemical processes in the product, destruction of most of the microorganisms, change in volume and mass, increase in the permeability of cell protoplasm, change in consistency, removal of air, volatile substances, gelatinization of starch, preservation of the natural color of the product.

Enzyme activity can cause spoilage of the product and undesirable changes even in the absence of microorganisms. When heated, biochemical processes stop due to the destruction of the enzyme system of raw materials, the contamination is significantly reduced due to the partial destruction of microorganisms that are mainly on the surface of raw products, therefore, for many vegetables, blanching pursues the main goal - the destruction of the enzyme system, which is based on proteins. Warming up to 70-75 ° C is usually sufficient for this.

Enzyme inactivation has influence on product color... This is of particular importance for pome fruits, since the action of oxidative enzymes explains the darkening of the fruits during their cleaning and cutting. Therefore, in the production of compotes, fruit in syrup, preserves, jams and other types of canned food, it is recommended to blanch apples and pears.
Since the inactivation of enzymes proceeds better in an acidic environment, during blanching the water is acidified with citric or tartaric acid to a concentration of 0.1-0.2% to reduce the intensity of biochemical processes. Certain varieties of apples, especially highly acidic ones, are strongly boiled down due to the hydrolysis of protopectin when heated and converting it into soluble pectin. To partially prevent this, it is recommended to blanch the fruits in 35% sugar syrup at a temperature of 80-90 ° C for 4-5 minutes. The syrup remaining after blanching is used to pour the fruits placed in jars.

Blanching beets produced to soften fabric and preserve color. In this case, it is necessary to destroy the enzyme tyrosinase. When oxidized, the enzyme forms melanins, which cause darkening of the beets. Beets are blanched with steam in autoclaves or in continuous scalders for 15-20 minutes at a temperature of 120 ° C. In blanched beets, the skin is easily separated from the pulp. Blanching the beets before peeling and cutting allows you to maximize the preservation of coloring matter - anthocyanins, to obtain a smooth cut surface and uniform shapes of the cut pieces, since raw beets are very fragile.

During heat treatment, in some cases, a color change occurs. The reason may be either a change in pigments or the formation of new dyes. The color change is observed in vegetables that are green, white or red-violet in color.
Vegetables with yellow and orange coloration do not change color and are resistant to heat treatment.
When heated in green vegetables due to the interaction of chlorophyll with organic acids or acidic salts of these acids contained in the cell sap, pheophytin is formed - a new brown dye. The degree of green discoloration depends on the duration of the heat treatment and the concentration of organic acids in the product. The longer the heat treatment is carried out, the more pheophytin is formed and the more noticeable the browning of vegetables. Green vegetables retain their color better when blanching in hard water. The calcium and magnesium salts contained in it neutralize some of the organic acids and acidic salts of cell juice.

During blanching, certain types of raw materials are bleached due to leaching or destruction of dyes. Blanching of cauliflower inflorescences leads to their bleaching due to the destruction of the coloring substances that give the inflorescences a green or yellowish color.

To facilitate the removal of inedible parts - skins, seeds, seeds, etc., giving elasticity to the raw material, to facilitate subsequent operations and more dense packing of it in jars, certain types of raw materials are blanched to soften the fabric. The softening of raw materials occurs due to chemical and physicochemical transformations in tissues during blanching. This is mainly accomplished by hydrolysis of protopectin, which is converted into soluble pectin. The cells are separated from each other, the fruit tissue becomes loose and soft. Hydrolysis contributes to a jelly-like consistency.

Studies of various varieties of potatoes, white cabbage and some root crops have shown that the duration of their blanching depends not only on the content of protopectin in vegetables and root crops, but also on the content of substances that promote its breakdown. These substances mainly include organic acids. The more of these acids contained in the raw material, the less time it takes to blanch the raw material. A similar effect of fabric softening is achieved if the fabric is heated to 80-85 ° C for at least 3-4 minutes. This is due to the fact that when heated to such a temperature, protoplasmic proteins coagulate, the cytoplasmic membrane is damaged, the osmotic pressure, which determines the hardness of the fetus, decreases and the fetus softens.

During heat treatment, the volume and mass of raw materials are reduced to one degree or another. During the heat treatment of meat and meat products, irreversible dehydration of proteins occurs with the release of previously bound moisture into the environment together with extractives, minerals, vitamins, etc. dissolved in it.

Unlike products of animal origin, a decrease in the mass of vegetables occurs not due to the release of moisture by denatured proteins together with soluble substances, but mainly due to the loss of soluble substances as a result of their diffusion, removal of air contained in the intercellular spaces of tissues of plant materials.
So, when blanching cucumbers there is a rapid removal of air from the intercellular space, the tissue becomes denser, its elasticity increases. When canned, these cucumbers have a crispy texture. Reducing the volume of the cucumbers helps to keep the product tighter in the jars.

Removing air during blanching helps preserve vitamins. In addition, the air contained in the intercellular spaces of the plant tissue, getting into the finished product, as well as acting on the raw materials at intermediate stages, causes a deterioration in the quality of the product, promotes corrosion of metal containers, and causes an increase in the partial pressure in cans during sterilization.

For a certain assortment of canned food, in order to abnormally fill the container, to ensure the required consistency of the product and the normalized ratio between the constituent components of canned food, the correct conduct of the sterilization process requires an increase in the volume of the product, which is achieved by blanching. This is mainly canned food with the use of food beans and peas, rice, pearl barley, soybeans, pasta and others. In this case, during blanching due to the absorption of water by starch, the volume and weight of the product increase by 2-2.5 times. In each case, the percentage of swelling is stipulated by the technological instructions.

Blanching achieves the removal of volatile or readily disintegrating substances that give products an unpleasant odor and form, when combined with metal cans or lids, sulphurous salts of tin and iron, which cause browning of the product, as well as the removal of substances that give some types of raw materials an unpleasant bitter taste. For example, to remove bitterness from eggplant they are blanched in boiling water or 1.5-2% NaOH solution, and to improve the taste and remove unstable sulfur compounds white and red cabbage blanch in boiling water for 1-2 minutes, separate inflorescences cauliflower- 2-3 minutes.
Asparagus blanch in mesh baskets in a boiling 2% sodium chloride solution for 1-3 minutes to leach glucosides, which give the product a bitter taste, and to straighten curved shoots.

As a result of blanching, the permeability of the cell walls of fruits and vegetables increases, which makes it easier to soak the fruits. sugar syrup (when cooking jam, jam, when making compotes), extraction of juices. Sometimes for this purpose plums, apples are blanched in sugar syrup, respectively, with a concentration of 25 and 35%. To increase the juice yield, plums, raspberries, black currants, lingonberries, gooseberries are blanched in water or steam at a raw material temperature not exceeding 85 ° C. Blanching water is used to blanch multiple batches. In this case, part of the extractive substances of the raw material goes into solution. The concentration of extractives gradually increases and reaches their concentration in the raw material. Such a solution is added to the juice squeezed from the fruit, which significantly increases the juice yield, but somewhat worsens its quality. It is more rational to blanch the fruit with steam in a ribbon scalder, and heat the berries in a double boiler with continuous stirring.

Fruits and vegetables are most often blanched whole. The duration and temperature of blanching depend on the type, variety, degree of maturity, quality of raw materials, and its further use. Blanching is usually done very quickly so that the product retains the flavor, color and aroma of the raw materials.

When carrying out this process, it must be remembered that an under-blanched product can cause bombing, and an over-blanched product can cause boiling of canned food during sterilization.

To avoid overcooking, the product is immediately cooled with water after blanching.

All recipes

© Mcooker: best recipes.

map of site

We advise you to read:

Selection and operation of bread makers