The ability of pectins to studneobrazovaniyu.

The ability of pectins to studneobrazovaniyu. Pectin jellies form different composition, differing from each other in physical and mechanical properties.
The most typical for the production of marmalade-Pastila products is the formation of jelly with acid and water in the presence of relatively large amounts of sugar (60-80% by weight of jelly). Preparation of gels of this type is the basis of the production of fruit marmalades, pastes, jams, chocolates.
Without dwelling on the question of the mechanism studneobrazovaniya pectin in a confectionery production (coverage of this issue will be given a special place in the future), it is necessary here to consider studneobrazuyuschie properties of pectins and the factors by which these properties are determined.
Ability to studneobrazovaniyu shown individually in various pectins, depending on their origin, and therefore they are unequal in value for confectionery manufacture.
It is known, for example, that the greatest value in its ability to represent studneobrazuyuschey apple pectin, citrus fruits (from orange and lemon peel), black currant, gooseberry, baskets of sunflowers and beets. With the proper conduct of technological processes of production of these pectins they give jellies, has the required strength and other valuable properties.
Less than full-fledged in this regard are pectins rowan, quince, apricot, peach, plum, cranberry. Pectin of fruits, giving jellies, have lower strength, not otvechabt confectionery production requirements. Even less valuable in terms of their ability to studneobrazovaniyu pectins are pears, cherries, summer fruit, vegetables and grapes.
Within the same species and variety of plant and fruit pectin ability to studneobrazovaniyu varies during plant development, fruit ripening, during storage and processing of the raw material.
The current state of knowledge does not allow even the possibility of reliably establish the causes that determine the natural ability to studneobrazovaniyu in pectins from different sources.
The quantitative content of pectin in fruits and plants studied varies widely from the 1,8 28% to the dry weight of the plant material.
The content of pectin in the feedstock does not allow him to judge the ability studneobrazuyuschey. This is due to the fact that the applicable methods of quantifying pectin (known calcium pektatny method, alcohol precipitation method, etc.) Are shown in the sum with its studneobrazuyuschimi factions and those factions who are deprived of this property.
At present, it is assumed that studneobrazuyuschie properties of pectin are predetermined mainly by the following factors:
1) chain length of the pectin molecule;
2) methoxylated galacturonic acid residues;
3) presence neuronidnyh components (organic and mineral).
There is evidence that the ability of the pectin to studneobrazovaniyu depends primarily on the size of its molecules. The latter are determined degree of polymerization of the main chain valences and are characterized by the value of the molecular weight of the pectin.
Besides the natural features of the pectin molecule its polymerization degree depends on the conditions of the plant and the nature of exposure to a production process.
In the course of natural decay of pectic substances in plants, the first stage of the hydrolysis of protopectin has a positive value from this point of view. In fruits, this stage coincides with the so-called technical maturity of them; it represents the phase of the state of pectic substances that is optimal for gelling. Further decomposition of pectic substances in natural conditions of fruit ripening on a tree or during ripening and overriding in maturation occurs splitting off of weakly related components of pectin (methoxyl groups and related substances, such as galactose, araban, etc.), and sometimes deeper hydrolytic processes.
When biochemical spoilage of fresh fruits (fermentation, putrefaction) by the enzymes of microorganisms occurs forced the collapse of the pectin molecule. Some enzymes cleave protopectin other ( "pektazy" or pectinesterase) produces demethylation of pectin, and others ( "pectinase" or polygalacturonase) cause its depolymerization, t. E. Pectin chain cleavage of the molecule, its break more or less short lengths.
Pectin have a sensitivity to thermal and chemical influences. Therefore depolymerization of the pectin molecules often occurs in processing of raw pectin. The more pectin is subjected to various treatments (heat, acids or bases), the greater the risk of depolymerization of pectin, which is a decrease of its molecular weight.
These studies and practical experience show that all the impacts that cause depolymerization of the pectin molecules inevitably entail deterioration of its ability studneobrazuyuschey.
Take that of the components of pectin complex studneobrazuyuschey ability to have pectin fraction having a molecular weight of not less than 10 000. The remaining fractions are not involved in pectin studneobrazovanii they are bulking agents.
Degree of polymerisation hydrophilic properties are defined and colloidal compounds, their water binding capacity. These properties of pectin are important in the production of marmalade-Pastila products as protect them from drying out or from getting wet.
Recently, considerable evidence has accumulated showing that the demethylation of pectin, which is not accompanied by depolymerization of its molecules does not lead to loss of its properties studneobrazuyuschih. On the other hand there is often depolymerization of pectin to its demethylation, t. E. The splitting of the pectin chain to metokoilirovannye remains of polygalacturonic acid.
It was also found that pectins retain their ability studneobrazuyuschuyu often with decreasing content SNzO to 5% and below. The resulting acid with pectin exhibit its ability to studneobrazovaniyu in somewhat different forms than the pectin, rich methoxy.
In general, research data recently led to a new interpretation of the role SNzO. The latter consists in that the pectin content in SNzO predetermines studneobrazovaniya conditions only: the amount of sugar acid required for the formation of jelly, and speed studneobrazovaniya process.
On the basis of the established production technology nizkometilirovannyh pectins. A distinctive feature studneobrazovaniya nizkometilirovannyh pectins is that they form jellies with small amounts of sugar (about 35% sugar jelly by weight), unlike conventional vysokometilirovannogo pectin, which is capable of only jellies sugar concentration not lower 65%.
Additionally, pectins containing not more SNzO 7,5%, have the ability to form strong jellies with ions of polyvalent metals.
Nizkometilirovannye pectins obtained by the enzymatic, acid or alkali hydrolysis of pectin materials. The conditions of preparation of these gels with calcium salts, sugar and acid. Recently added only for the taste.
The most stable calcium pectin jellies obtained from acids containing metiloefirnyh between groups before 3,5 6,0%.
The role of calcium or other metal ions in the formation of these gels is pectic acid molecules that are linked together by metal ions via free carboxyl groups. Therefore, this type of pectin gels called "ionnosvyazannymi" gels because communication Studneva grid made therefrom by polyvalent metal ions (in this case -Sa ++) replacing hydrogens carboxyl groups.
In conventional sugar-pectin jellies acid (sugar with 65%) this connection is via the free COOH group, which are connected with each other to form hydrogen bonds. Therefore, these jellies are referred to as "hydrogen-bonded" gels.
There pectin jellies intermediate type, which contain sugar and calcium. In practice received very widespread in recent years, such jellies with 35% of sugar and an appropriate amount of calcium (called "nizkosaharnye" jellies).
These provisions form the basis of modern ideas about the role of metiloefirnyh groups and their practical value in the process studneobrazovaniya pectin.
As for other components neuronidnyh pectin (arabinose, galactose), they do not play any significant role in studneobrazovanii pectin. Low in their content
native pectin or artificial reduction of their maintenance by cleaning pectin preparations leads to a corresponding increase in the number of galacturonic pectin substances and to enhance its ability studneobrazuyuschey. Therefore, the percentage of galacturonic acid in the pectin (number uronidnoy part) is also indicator of its ability to studneobrazuyuschuyu.
From all that has been said above, it follows that the decisive importance for the pelleting ability of pectin has the processes of its natural hydrolysis in the plant, its extraction from plant raw materials and subsequent processing in production. In view of this, it is necessary to avoid as far as possible all those factors that cause the depolymerization of the pectin molecule. In particular, care should be taken to prevent overripe fruit before collection and post-harvest period. It is necessary to protect the fruit and berry raw materials from spoilage in storage, from prolonged heating (during cooking and drying) and from the strong impact of chemical agents (acids, etc.) in the processing processes.

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