Brief information about the preservation of fresh fruits and berries

Different ways of preserving fresh fruit

For the preparation of semi-finished fruit and berry puree in fruit ripening period last season was used directly in the fresh form, or they prepare them for future use by canning.

At the canning fruits aim is:

  1. slow enzymatic processes in living tissue of fruit, ie processes of post-harvest ripening, breathing..;
  2. exclude the possibility of the development of microorganisms present on the surface of fruit or made into fabric, or paralyze their livelihoods.

Currently used methods of preserving fruit are very diverse and their selection depends on the destination of canned fruit on the terms of their storage and further processing

You can specify the following principal methods for industrial canning fruits:

a) heat sterilization in hermetically sealed containers;

b) cold storage (psihroanabioz) and freezing (krioanabioz);

c) the chemical preservation (using various chemical agents or antibiotics);

g) drying the fruit (kseroanabioz);

d) cold preservation using ionizing radiation or ultrasound.

In the confectionery industry, the most prevalent chemical preservation of fresh fruit and berries, in particular, conservation of sulfurous acid. Confectionery Ukrainian enterprises use significant amounts sulfited fruits, especially apples, which are processed in the applesauce for cooking marmalade, marshmallow, fruit and berry candy shells and fillings.

Action sulphurous acid and its salts in fruits

The action of sulphurous acid on fresh fruits basically boils down to this.

In certain concentrations it inaktiviziruet oxidative enzymes of plant tissue and suppresses the last breath in this way contributing to an increase in "keeping quality" fruit. Concurrently S02 stabilized vitamin C fruits, inhibiting enzymes, ascorbic acid oxidation catalysts.

The sulphurous acid acts as a powerful antiseptic; it hinders the development of microbiological spoilage of fruits or suspend the already started process of such damage. Especially strongly it affects the mold microorganisms. concentration S02Necessary for the preservation of fruit ranges from up to 0,025 0,15%.

Processing of fruits and berries sulfurous acid prevents them from browning. Available data indicate that the sulfurous acid damage oksigeiazu fruit, but it does not affect the peroxidase and tannins. According to others S02 restores the hydrogen peroxide present in the fruit and contributes to their browning.

In response to the yellow and green pigments of fruits, sulfurous acid converts them into leuco that restore their color after removing S02.

Sulfurous acid is reacted with sugars of the fruit. Connecting with aldehydes and ketones, sulphurous acid forms oksisulfogruppu:14.1

Accordingly, the reaction with glucose is obtained glyukozosernistaya acid:14.4

Since fructose is obtained fruktozosernistaya acid:


In the sugar and sulfurous acid there is a state of unstable equilibrium14.2

Sugar-sulfur compounds are inactive in the sense of their preserving action, but they split easily when heated, especially in the presence of acids (and bases).

Among other organic matter, which is capable of reacting sulfurous acid, a number of authors called cellulose. It is possible that some other organic substances (tannin, protein), also linked sulfurous acid.

Remaining in the fruit in the form of the free sulphurous acid (as well as a significant portion of related sulfurous acid) is removed by heat. This is the basis desulfitatsiya, t. E. The liberation of sulfurous acid fruits at the end of the period of storage.

Changes in pectin substances under the influence of sulphurous acid and its effect on the enzymes pectin fruits (especially apples) were studied in detail in recent Samson [8]. It was found that the concentration of sulfurous acid, necessary for preserving apples (up to 0,1%) does not suspend the enzymatic digestion of pectin. During storage sulfited apples at the indicated concentrations S02 there is a gradual destruction of the pectins and the deterioration of the ability studneobrazuyuschey apples.

Cleavage of pectin in apples during storage sulfitirovainyh affects appearance in softening their texture is primarily the result of vital activity of pectolytic enzymes. To stop the action of enzymes that cause demethylation of pectin requires concentration not less than 0,2% S02And to inactivate polygalacturonase (an enzyme catalyzing the depolymerization of the pectin molecules) concentration needed 0,4% S02.

Since these concentrations greatly exceed the concentrations S02Commonly used for canning fruits, then sulfitation fresh fruits and berries should be recognized as an imperfect method of preparation of raw materials for the confectionery industry. More perfect in this sense is the method of processing fruit in the form of puree. However, due to the seasonal nature of fruit production and the availability of fresh fruits sulfitation method is widely used in the fruit processing industry, including the confectionery enterprises.

Technique sulfitation fruit

And depending on how the fruits sulfitation distinguish "dry" and "wet" sulfitation.

In the first case, whole or sliced ​​(halves, slices) fruits are treated with sulfur dioxide, obtained directly - by feeding sulfur on the air or from cylinders supplied with chemical plants with sulfur dioxide in purified and liquefied form. This is the so-called fumigation method.

In the second case, use an aqueous solution of sulfurous acid, which pour fresh fruits (wet sulfitation).

Sulfitation most fruits, especially apples, and can be performed the other way.

When harvesting apples for confectioneries often practiced their fumigation, which is a convenient means of preserving fruit aphids collected in the deep areas, i de often required urgent measures to save the fruit to lock them to the place of processing.

Technique for fumigation of fruit is as follows. Sorted fruits are placed in crates placed on tiers or stacks in a gas-tight room. The latter are arranged brazier with sulfur. Sera for this purpose should be used purified, free from arsenic and other contaminants. Sulphur dioxide produced in the combustion of sulfur in an enclosed space, diffuse through the skin into the fruit. accumulation S02 the fruit occurs at different rates depending on the species, variety and state of maturity of fruit, concentration S02 in ambient air, the latter temperature. Hard fruits of saturated gas is slower than the soft. As the temperature increases the diffusion of sulfur dioxide in fruits is increased accordingly. The rational sulfitatsionnyh chambers are arranged for sulfur burning furnace outriggers set by the camera is connected to its particular channel, or apply special artificial furnace injection of combustion air required for sulfur. From these furnaces sulfide gas is directed into the chamber.

Simplification work with fumigation is achieved by using portable sulfitatsionnyh cameras instead of stationary. They are a canvas cloth impregnated with a gas-tight structure. These bunting closed stacks crates of apples (et al. Fruit), subject to fumigation. After fumigation the cloth is removed and used for the treatment of the next batch of fruit.

Some companies use a method of fumigation gas bottled fruit, is poured into the capacious underground reservoirs. Recent serve as chambers for fumigation and as repositories for the same fruit in fumigated condition.

Method wet sulfitation used advantageously in respect with delicate fruit pulp. These are mainly stone fruit (plums, apricots, dogwood) and summer berries: strawberries, raspberries. Significant quantities of apples as they prepare in this way. The latter consists in the fact that fresh fruits prepared in the appropriate manner (sorting, washing, cleaning from pedicels, branches, etc.) are placed in barrels up to 150 kg and filled with aqueous sulfuric acid solution. The amount of this solution was taken in such a way that the concentration of sulfur dioxide is from 0,1 0,15% up to the weight of the fruit and to shut fruit preservative solution completely.

An aqueous solution with a concentration of up to 4 6% S02 It can be obtained in finished form from chemical plants. Due to the fact that the transport of the weak solution is unprofitable, it is prepared for the most part in place. To prepare the working solution is saturated with cold water S02 from cylinders containing liquid 100% 502, to obtain the desired concentration. Saturation is conducted in the cold gradually as possible without gas losses. If you wish to obtain a working solution faster way B02 poured the liquid from the bottle into the water with the help of a special device-sulfitometra enabling to measure liquid S02 in precise volumetric amounts. Recent translated by the specific gravity of the liquid B02 on the weight of (specific gravity of the liquid S02 равен 1,38 20 при °).

Apples, apricots and peaches, they prepare by this method in the form of halves or slices. Apricots and peaches sulfitated with seeds and seedless.

Qualitative requirements sulfited fruits, content standards S02 sulfited for different types of fruits and berries, the weight ratio between fruit and solution regulated by GOST 3661-47 - 3671-47 sulfited on fruit and berries.

According to the statutes existing in Ukraine for sulfitation fruit and berry fruit and semi-finished products it is allowed to use, in addition to sulfurous acid, sulfite and sodium bisulfite (Na2SO3NaNSO3) And calcium sulfite Ca (HSO3)2 provided the perfect purity of these chemicals. These salts must be taken to sulfitation fruit or of fruit semi-finished products in such a way that the total amount S02 and the amount of bound sulfurous acid in the product does not exceed the standards prescribed for a visit.

In practice, some foreign countries for sulfitation of fruit preparations used drugs potassium or sodium metabisulfite (K2S2O5 and Na2S2O5), Which are commercially available in solid crystalline form. Their use should be carried out on the basis of the precise stoichiometric calculation in compliance with the conditions specified above for bisulfites. The downside is that their use is complicated by the necessity of the simultaneous addition of hydrochloric acid for the isolation of these S02 in free form.

Transportation and storage of fruits sulfited

When fumigation of apples (and other hard fruits) in the last boxes are often used as containers for storage and transportation of fumigated fruit. The major drawback in this case is the presence of leaks, which are associated with volatilization S02 and the loss of the product from flowing out of juice, released as a result of caking softened fruit. In view of the need to avoid a bookmark in crates fumigated fruit for long term storage and transportation. For this purpose, they should zatarivatsya hermetically sealed with the barrel.

The fruit, canned solution S02, Lay usually in barrels with capacity up to 200 l} where they can be transported and stored for a long time. To eliminate waste from flowing through the slits 802 solution from cells and wicking extractives fruit wood barrel coated inside with a thin layer of paraffin, or a special protective varnish.

If the confectionary factories processing sulphated fruits are located in the areas of the last billets, the stock can be stored in stationary tanks made of wood, iron, concrete and other material, equipped with hermetically sealed lids, hatches, etc. On the inner surface of such storage facilities be applied to the corresponding acid resistant coating of special smolok, ebonite, bakelite et al. pumping fruit with the solution feed them into production carried out by means of pumps or corrosion yn x mechanical devices.

Other methods of preserving fresh fruit and berries, used in the confectionery industry, it should be noted mainly way to harvesting watermelon and melon peel by salting. Cork gourds are used as raw materials for the production of candied fruits. For this purpose, special varieties of watermelon rind and melon purified from the outer peel, freed from the pulp and cut into slices. Crust placed in the barrel and this is filled with brine and concentration in such an amount that the content of NaCl in the crust was about 10-12%.

Some fruits and berries (strawberries, cherries, plums) they prepare by pouring fresh fruit alcohol. In this way, use the procurement of fruit for the upper grades of sweets.

The formulation adopted at the Moscow confectionery "Udarnitsa" factory for semi-finished products of this type, is composed as follows: 55 parts by weight of berries, 25 parts by weight of alcohol and 20 70% by weight of solution of sugar syrup. The introduction of sugar orphan provided to mitigate the taste of the semi-finished product.

Freezing fresh fruits also ensures the safety of their quality in terms of confectionery production requirements. However, this road way to the mass procurement and unsuitable for plants, since it is connected with the obligatory condition for the rapid defrosting of fruits and immediate processing after their receipt from the refrigerator.

Methods of preserving fresh fruit with ionizing radiation has not yet received the mass distribution.

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