Processes proceeding during the storage

With the storage of food goods in their composition and the quality occur different changes, which can be slowed down, strongly braked, but cannot be completely avoided. Depending on the nature of these changes the processes, proceeding during the storage, can be subdivided into the physical, the chemical, the biochemical, the microbiological, and the biological.

Physical processes (moistening and drying) change state and properties of products, and they also influence the activity of other processes. To slow down these changes is possible by the method of observing of temperature conditions, relative humidity of air, and also by the correct selection of packing.

Chemical processes proceed in the foodstuffs without the participation of ferments (caramelization Sakharov, the rancidification of fats, chemical of canned foods). They slow down the rate of chemical processes by a decrease in storage temperature, by the application of packing, which insulates product from the action of light and atmospheric oxygen.

Biochemical processes are caused by the action of ferments, which are located in the products. Biochemical processes they are respiration, hydrolysis (autolysis), as a result of which occur the loss of dry matter, moistening and spontaneous heating-up (grain, vegetables), T. e. decreases the content Sakharov, acids, proteins, fats, vitamins and other, thus is reduced the food biological value of product. To slow down respiration is possible fall of temperature, humidity of air.

Microbiological processes are caused by the vital activity of the microorganisms, for which many foodstuffs serve grow prettier by nutrient medium. They include the fermentation, molding, rotting.

Fermentation - this is the decomposition of carbohydrates and some alcohols under the action of the ferments, isolated by microorganisms. During the storage of food goods the following forms of fermentation most frequently appear: alcohol, lactic acid, acetous, butyric-acid.

Molding occurs as a result development on the foodstuffs (fruits, vegetables, bread, meat, fish articles and i.t.) mold fungi. The development of moulds causes the appearance of unique moldy smell, attack on the surface of product and accumulation of toxins (poisonous substances).

Rotting - this is the decomposition of proteins under the action of the ferments, isolated by putrefactive microorganisms, with the formation of the substances, which possess unpleasant smell and poisonous. Are most frequently to rotting subjected the products, rich in the protein: meat, fish, and egg.

Biological processes - these are the processes, caused by the biological subjects (rodents and insect-pests), which bring the extensive damage to goods during the storage: they destroy and soil by their isolations; they are sources and carriers of microorganisms. Therefore during the storage of all food goods it is necessary to observe sanitary regime, to conduct the disinfection of warehouse accommodations.

Basic task during the storage of goods lies in the fact that not to allow or to break the undesirable processes, which lead to reduction in their quality or spoiling. Retarding or acceleration of different processes in the goods during the storage in many respects depends on temperature, humidity and air composition, ventilation and illumination of accommodation, commodity proximity, packing and piling of the goods and many other factors.

The temperature of air renders clout on the activity of ferments, chemical reaction rate, development of microorganisms and wreckers. Therefore the majority of food goods is stored at reduced temperatures, which disastrously act on many microorganisms, wreckers and reduce to the minimum the fermentative and chemical processes. For the products of prolonged storage the temperature must not exceed 10°C, while for those being perishable - to be not higher than 0°C.

The humidity of air during the storage of goods also has important significance. The higher the humidity of ambient air, the more the moisture absorbed by product, and vice versa. Therefore the humidity of air must be supported at this level so as to exclude both the moistening goods and drying. During the storage of goods with the high moisture content (fruits, vegetables, meat) should be supported the high relative humidity of air - 80-95%, and goods with the low humidity (sugar, flour, salt, starch, macaroni articles, croup and other) should be stored with the humidity of air 65-75%.

Air composition has an essential effect on the retention of product. Since many products come into contact with air, it is necessary to consider the influence on them of its separate component parts and, first of all, oxygen (is caused the oxidation of fats). Air must be clean, not have outside smells.

The ventilation of air is necessary for the removal of excess water vapors and gases, which are formed during the storage of products; it contributes to a decrease in the temperature of air in the accommodation. Ventilation is distinguished natural, forced and active.

Illumination (light) during the storage of the majority of products plays the negative role: it accelerates the processes of respiration, rancidification of fats and destruction of many vitamins; germination and the turning green of potatoes; change color, smell and taste of many foodstuffs, which therefore store predominantly in the darkened accommodations.

Commodity proximity during the storage of foodstuffs must exclude their mutual negative influence on each other. The strongly reeking products cannot be stored by the products, which easily receive smells. Is not allowed joint storage of dry products with the products, which contain more than 40% moisture, since the first will be moistened and grow mould, the second - excessively dry.

Packing protects goods from the external actions, the increased or reduced temperature; the humidity of air, from the light, outside smells, microorganisms Packing materials must be elastic, lungs, cheap, dry, no hygroscopic. Tara for the food goods it is characterized by the wide variety. It they classify according to different sign: according to the form of material (wooden, pasteboard, metallic, polymeric, textile, ceramic, glass, combined); on the resistibility to the mechanical actions (rigid and soft); on quantity of revolutions (single-cut and fast-rotating).

The order of piling and positioning the goods must be considered during the storage, since incorrect piling can lead to the deformation of articles, the caking and the balling of friable goods, the acquisition of the outside smells and other defects.

 

Losses of food goods

With the storage, the transportation and the realization appear the quantitative losses of goods, which are subdivided into those normalized and protocol led. To the normalized losses carry the natural loss of mass and the before realization withdrawals, which are formed with the preparation of goods for sale (cleaning of sausage, fish, of butter; the formation of crumb with sale refined sugar, confectionery articles and other). Here carry the losses, which are formed over the standards of the natural loss of goods in the food stores of self-service. Natural loss - this of the loss of the mass of goods, that appears for the natural reasons. Its basic reasons are shrinkage (scattering), leakage and other The size of the natural loss of products influence the physical chemistry properties of goods, periods and conditions for storage, the form of packing, climatic conditions and the seasons. For reduction in the losses it is necessary to exercise thorough control over the quality of the goods entering, to observe the proper regime of storage, to enlarge sale of the package goods.

The actual sizes of natural loss are determined after the removal of remainders (inventory). They compare the revealed deficiency in the goods with the affirmed standards of natural loss. To natural loss do not relate the withdrawals from the cleaning of the upper layer of butter; the withdrawals, which are formed with the preparation for sale of sausages (string, the ends of the shells), beaten of poultry (paper), and also of meat bloated and the fish goods, sold after working-out (the skin of hams, the bone), and other These losses are normalized separately. The losses of goods - scrap, battle, which arose as a result of a careless attitude, also do not relate to the natural they diminished and they are copied due to the guilty persons. The writing off of lack can be produced only after the inventory of goods. The order of the writing off of lack, embezzlements and losses from the spoiling of values is regulated by legislation and constitutive documents of enterprise.

 

Control questions

1. What they do understand under the term “storage”?

2. What processes do occur during the storage?

3. Call you the possible losses of goods.

4. Call you the forms of natural loss.

5. How and when is produced the writing off of natural loss?

 

Lecture 5