Substances that help to enhance shelf life.
Under food preservation understand measures against the development of harmful microorganisms in the product, the formation of toxins, prevent growth of molds, the emergence of unpleasant taste and odor. There are physical, biological, and chemical preservation.
The most known physical methods that prevent the growth of microbes: sterilization and pasteurization (heat treatment), cooling and freezing (cold treatment), drying (removal of water) and treatment with ionizing radiation. Biological canning assumes the effect on the food product of harmless to human health cultures of microorganisms in order to prevent the development of pathogenic or other undesirable microflora. Protective crops are currently used mainly in dairy products and sauerkraut. The chemical methods of conservation are the addition of certain substances that inhibit the development of microorganisms. Such substances are called preservatives. In practice, for a long time, various canning methods have been successfully combined. For example, the addition of sorbic acid to the oil cream is supplemented by storing the cake in the refrigerator.
Preservatives can not compensate for the poor quality of raw materials and a violation of the Occupational Health Regulations. If the product is heavily contaminated with bacterial or began to deteriorate, preservatives are already useless.
Preservatives can be conditionally divided into preservatives proper, and substances possessing a preservative effect (besides other useful properties). The action of the first is directed directly at the cells of microorganisms (slowing down of enzymatic processes, protein synthesis, destruction of cell membranes, etc.), the latter adversely affect microbes, mainly due to lower pH of the medium, water activity or oxygen concentration. Accordingly, each preservative exhibits antimicrobial activity only against a portion of the causative agents of food spoilage. In other words, each preservative has its own spectrum of action.
The use of substances having a preservative effect, - sugar, carbon dioxide, ethyl alcohol - has long been well known. They are usually used in an amount of several percent or ten percent, often achieving a certain flavor of the food, and the preservative effect of treating as a side.
Substances conventionally referred to proper preservatives - sorbic, benzoic, acid, and their salts - are used in much smaller amounts (less 0,5%) and virtually no influence on the organoleptic characteristics of the confectionery product.
Sulphurous acid, its salts and sulfur dioxide has long been widely used for the preservation of fruit and semi-finished syrup subjected to industrial processing (for processing are removed by heating or vakuumirova- tion). Action sulfurous acid mainly bacteriostatic. In addition, it has antioxidant properties and retards enzymatic reactions and enzymatic browning.
The use of preservatives can be effective only if they are evenly distributed in a confectionery product, which is most easily achieved by dissolving the additive. Since salts are more soluble in water (Table 8), they are recommended for use in preserving products with a high water content. Food emulsions with a high fat content (for example, confectionery creams) are also recommended to be preserved with salts or a mixture of acid and salt, since the water phase is much more susceptible to microbiological damage than fat. The aqueous phase of a real confectionery product almost always contains sugar or other flavoring. The solubility of the preservatives varies. In Table. 9 shows the change in the solubility of sorbic acid and potassium sorbate, depending on the additions of sugar, alcohol and citric acid .
8 Table. The solubility in water of some preservatives
9 Table. The solubility of sorbic acid and potassium sorbate in various aqueous solutions
Acid preservatives are used typically in powder form, and salts thereof - in the form of aqueous solutions.
Storing foods in protective atmosphere (inert) gas instead of air prevents them from rancidity, enzymatic browning and microbial spoilage.
The technology of storage of food in a gas-tight packaging of inert gases in the atmosphere instead of air called "controlled atmosphere packaging with» (Modified-Atmosphere Packing - MAP). As the shielding gas carbon dioxide is used most often (E290), nitrogen (E941) and mixtures thereof with oxygen. Limiting oxygen access to the food product does not allow oxidation reactions go to develop and aerobic microorganisms.
Antioxidants (antioxidants) protects fats and fat-containing products from rancidity, protect fruits, vegetables and derived products from darkening.
Antioxidants can not compensate for the poor quality of raw materials, gross violation of the rules of industrial hygiene and technological modes. If the concentration of peroxide or free acids in the product is higher than the norm, and even more so if the smell has changed, taste or color of the product, the antioxidants are already useless.
Food products in the preparation, processing and storage are oxidized by atmospheric oxygen. In doing so they accumulate toxic substances reduced their biological value and organoleptic properties deteriorate. The tendency to oxidation of food decreases the shelf life of them.
The primary products of the oxidation of fats are peroxides, which are then converted into secondary products - aldehydes, ketones, acids. The content of primary oxidation products express the peroxide value (IF), which is determined iodometrically (GOST R 51487-99) and is measured in millimoles of oxygen in the 1 kg of product. The indicators of the content of secondary oxidation products can serve as the acid number and carbonyl.
In the process of oxidation of the first of these two indicators is changing the drive.
The acid number is determined alkalimetrically (GOST 5476-80, GOST R 50457-92) and is measured in mg of KOH per g of product 1. For butter indicator of oxidative damage is considered to be the acidity of its fat phase, which is determined by titration with a solution of NaOH (GOST 3624-92) and is expressed in degrees Kettstofera . oxidative damage indicators are normalized SanPin .
Oxidation occurs in the presence of oxygen, including the oxygen in the air, it contribute to the elevated temperature and the presence of variable valence metal ions. Therefore, to prevent oxidative deterioration is necessary to exclude the impact of these factors on the product. For the binding of metal ions of variable valence use complexing Teli: EDTA, citrate, etc. But for vysokozhirnyh confectionery products, such as butter cookies, significantly slow down the oxidation is only possible with the help of antioxidants...
Known natural antioxidants are vitamins: ascorbic acid (E300, vitamin C), found in many plants, and mixtures of tocopherols (E306, vitamin E), which are rich in some vegetable oils. Despite the high antioxidant activity, natural extracts of these substances are much more often used as vitamins. Antioxidants are the same substances and their derivatives obtained synthetically: ascorbic acid is obtained from glucose, sodium ascorbate (E301), ascorbate of potassium (E302), ascorbyl palmitate (EUSSH) and ascorbyl stearate (E304p) from ascorbic acid. Moreover, ascorbic acid derivatives partially retain C-vitamin activity, a-, y-, 5-tocopherols (E307-EXUMMX) are also synthesized, but they are completely identical to the corresponding natural compounds and also have E-vitamin activity. From natural sources - Siberian larch wood - an antioxidant dihydroquercetin, possessing P-vitamin activity, is obtained. Recently, rosemary and sage essential oils have been successfully used as antioxidants.
Most common among the artificial food antioxidants received phenol derivatives: butyl (hydr) hydroxyanisole (BHA, E320), butyl (hydr) ksitoluol o- (BHT "Ionol" E321) and isoascorbic (erythorbic) acid (E315) and Izoaskorbat (erythorbate) sodium (E316) tretbutilgidrohinon (E319) and esters of gallic acid (gallates) (E310-E313). These compounds are not found in nature. Vitaminized side they have no action, but significant advantage is their high stability and, consequently, a significant increase in the shelf life of food products.
Antioxidants slow down the oxidation process by interacting with oxygen in the air (not allowing it to react with the product), interrupting the oxidation reaction (deactivating the active radicals) or destroying the peroxides that have already formed. At the same time, antioxidants are used up. One would expect that any increase in the content of the antioxidant leads to an increase in the product protection time, but this is not the case. In practice, for most antioxidants, there is a limiting concentration above which the shelf life of the product no longer increases. As a rule, it is 0,02%.
There is no universal antioxidant. The effectiveness of the antioxidant depends on the properties of a particular confection and the most antioxidants (Table. 10).
Table 10. The relative safety of the terms of fat, depending on the type of antioxidant
The use of individual antioxidants can not completely protect foods from oxidative damage. Therefore, it is more expedient to use multiple antioxidants simultaneously. This phenomenon manifests itself synergies. Synergy is in the mutual strengthening of the antioxidant capacity of the mixing of several (usually two) antioxidants.
Antioxidant effects can also be achieved by using antioxidants or their mixtures in combination with substances that either do not themselves have an antioxidant effect or are weak antioxidants. Such substances (they are called synergists) include some polybasic organic hydroxy acids (citric, tartaric), a number of amino acids, polyphosphates, EDTA and other compounds. Acids are hydrogen donors necessary for the regeneration of antioxidants, and the action of complexing agents is based on the binding (transfer into an inactive form) of metal ions catalyzing oxidation. In the latter case, it is difficult to draw a clear line between antioxidants and synergists.
The synergistic mixture can be prepared directly in the food industry. In this case, however, it is difficult to achieve the optimum technological and economic point of view the composition of the mixture. Therefore, at present in the world of food producers prefer to use ready-made mixtures obtained in an industrial environment. For ease of use, and to extend the shelf life of their own, they are issued in the form of solutions in vegetable oils or media, such as flour.
The process of oxidation is a self-accelerating. Therefore, the sooner an antioxidant added to the product, the greater effect can be expected from him. Conversely, if the oxidation rate has reached its threshold value, to add an antioxidant useless.