General characteristics of the products of this group
The word "jelly" generally refers to food jelly obtained with the help of fruit and berry juice, pectin, gelatin and other gelatin formers.
In the confectionery industry of the USSR, “jelly” marmalade is called marmalade-type products, in which the jelly-like structure is due to the use of agar, pectin or agaroid. In these products imitation of taste, aroma and color of natural fruits and berries is achieved by adding acid, essential oils, essences, vanillin and dyes. There is also the possibility of creating taste and aroma, adding fruit and berry supplies or juices. Jelly marmalade on agar is transparent. When adding supplies or mashed potatoes, it loses its transparency.
Depending on the method of preparation, in particular on the method of molding, there are three main types of jelly marmalade mass production.
- Molded - in the form of products of various figured outlines, molded by casting into rigid forms.
- Three-layer - in the form of carved products of rectangular or diamond shape with two outer jelly layers and a middle layer of downed mass.
- Orange and lemon slices are in the form of semicircular slices of orange and lemon.
Depending on the kind of gelling agents used to distinguish tin marmalade agar and pectin agaroid.
Agar its chemical composition and physico-chemical properties
In the production of jelly marmalade, agar plays a special role. It is a vegetable glue, which is extracted from seaweed (a type of anfelcium, gelidium, etc.) growing near the coasts of the White Sea and the Pacific Ocean. The conditions of gelation of agar are somewhat different than those of pectin. Studies of the chemical composition of agar indicate that it, like pectin, is a highly polymeric compound like polysaccharides, which has a chain-like molecule. As a result of agar hydrolysis, up to 33% galactose is obtained by weight of the initial agar. This indicates the presence of the last galactan. Other reducing carbohydrate substances were found in the agar.
Agar contains 3 — 5% sulfur in the form of organically bound (not separated by dialysis) sulfuric acid. The latter is in the etheric bond with the carbohydrate complex of the agar molecule.
Like protopectin, agar contains calcium and magnesium. When they are removed, agaric acid is obtained.
These data led to the assumption that the native agar is the calcium-magnesium salt of the acidic sulfuric ester of the galactan polysaccharide - galactose - according to the following approximate scheme:
where R represents carbohydrate complex.
Based on the latest data, it can be assumed that the demineralized agar is a linear sulfur polysaccharide ester
Agar chain is composed of residues 9 d-galactose, linked glucoside bond (positions in 1 and 3, and has a terminal residue of l-galactose, which has six atoms esterified with sulfuric acid.
In some cases, acetyl groups were found in agar; at the same time, the majority of agar researchers found no methoxyl groups in its composition, which are so characteristic of pectin.
In addition to the most important components in the purified agar contains from up to 1 3% of nitrogenous substances.
Pure agar is almost insoluble in cold water (10 — 15 °), but it swells in it as a colloid of limited swelling. In hot water during boiling, the agar dissolves almost completely (it goes into solution to 99% agar, depending on the degree of its purity).
From aqueous solutions (sols) agar as pectin is precipitated with alcohol and electrolytes.
When cooling hot aqueous agar solution becomes jelly (gel).
The latter is obtained when the concentration of agar, starting with 0,2% by (gel weight. Aqueous solution containing 0,3 — 1% agar forms a solid gel with vitreous fracture.
The main provisions on the mechanism of gelation of pectin are applicable to agar. However, the gelation of agar unlike pectin does not require the presence of sugar and acid. The presence of sugar or other deactivating agent is not necessary also in the formation of gelatinous jelly. Attempts to explain this phenomenon are reduced to the fact that particles of agar or gelatin have a stronger ability to hydration (solvation) than particles of pectin. The amount of free water that is contained in the surrounding ash is not enough to fully hydrate the agar particles, so the value of sugar as a dehydrating agent in this case disappears.
When agar is heated under acidic conditions, its hydrolysis occurs, as a result of which it loses its gelatinous properties. Under neutral conditions, agar tolerates higher temperatures.
The degradation of the agar jelly-forming ability in an acidic medium develops intensely when heated, starting with the temperature 60 — 70 °. Agar is much less resistant against the action of acid than pectin. With respect to alkalis, agar, in contrast, is more resistant than pectin.
The ratio of agar to metal cations is different than that of pectin. Thus, for example, it has been established that alkali metal ions, and in particular the K + ion, increase the strength of agar jellies to a much greater degree than Ca 2 + ions. In general, in contrast to pectin, alkalinization increases the strength of agar jellies. This results from the fact that at neutralization of acidity of an agar its stability in the course of heating increases.
The gelatinous ability of agar as well as pectin depends on the degree of polymerization of its molecule. According to available data , the molecular weight of the soluble fraction of agar varies from 11 000 — 25 000.
The geostatus point of 1% agar jelly containing 60 — 70% sugar is close to 40 °. Thus, the jelly mass prepared from 1% agar will chill at a lower temperature than the corresponding pectin-sugar solutions. In this regard, the process of geathing (cages) of jelly marmalade (on agar) requires a longer time than the process of planting fruit and berry marmalade.
Agar enters the factories usually in the form of a thin film, bars or grains containing up to 18 — 20% (water. Of particular importance when using agar in the confectionery industry is its gelatinous ability and degree of purification, in particular, the absence of extraneous taste and smell.
Black Sea agar (agaroid) and its properties
Along with agar, another gel-forming agent is used in the confectionery industry. This product has physicochemical properties somewhat different from agar. In this regard, it is considered as an agar-like substance - an agaroid. In some respects, it approaches pectin.
The chemical composition and structure of the agaroid are still insufficiently studied. According to some data, the agaroid contains galactose, glucose and fructose, sulfur, Na, Ca, Mg, a small amount of acetyl groups.
Like agar, it is poorly soluble in cold water, soluble in hot water.
Aqueous solutions (sols) of the agaroid after cooling form gel (gels), starting with the concentration 0,8 — 1,0%.
Under the conditions of confectionery production, the ability to jelly agaroid in 3 — 3,5 is less than that of agar, and in 2 — 2,5 is less than that of pectin. To obtain agaroid-sugar-water jelly (with a concentration of sugar 70%), it is necessary to spend about 3% of air-dry agaroid to the weight of the finished gel.
The introduction of alkali metal ions has a positive effect on the jelly-forming ability of the agaroid. In this respect, it differs from pectin and approaches agar.
The agaroid is similar to pectin in high gelation temperature and agar in its increased sensitivity to acid. In an acidic environment at temperatures above 70 — 75 °, it undergoes rapid hydrolytic decomposition and loses its ability to gel formation. The destruction of the agaroid increases with increasing temperature and with increasing duration of its interaction with acid.
The melting point of water jelly (3% agaroid) lies within 60 — 65 °. The gel temperature of agaroid solutions with 70% sugar in the presence of acid is close to 70 °.
These properties of agaroid limit its use in the manufacture of confectionery products, where it takes some time to pour the jelly mass before it is gelled and where it is necessary to introduce the acid into the mass before forming the latter, i.e., until it becomes gemstone.
ECNII studies have shown that some protection against the acid cleavage of agaroid can be obtained by introducing alkaline or buffer salts. It was found that Na is very effective in this respect.2NR04.
Depending on the amount of salt injected, the pH of marmalade is shifted more or less to the alkaline side, i.e. alkalization of the latter. Therefore, the dosage of salt should not exceed 0,1% by weight of the marmalade mass; higher dosages of salt cause a sharp weakening of the organoleptically sensed acid in the taste of marmalade.
Aqueous solutions are highly viscous agaroid.
Hydrophilic properties, in particular, the ability to retain water, are less pronounced on an agaroid than on agar and pectin, as a result of which the jelly is less resistant to drying and sugaring than on agar and pectin jelly.
Recipe želejnogo jam
The recipe for different varieties of jelly marmalade is made up of the following approximate ratios of the main components (in% to the weight of finished products): 0,8 — 1 agar (or 1,0 — 1,5 pectin, 2,5 — 3 agaroid), 50 — 65 granulated sugar, 20XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX25 agaroid) acid (citric or tartaric) 1 —1,5.
Sugar, in addition to its flavoring value, plays here the role of a solid filler, which replaces water in jelly. Molasses in this case, as in fruit and berry marmalade, is used as a thickener and as a means of delaying the crystallization of sugar. The participation of molasses in the formulation of jelly marmalade from agar and agaroid is very important, since there are no other reducing sugars other than glucose and maltose molasses in the other components of its formulation. Acid in the marmalade from agar and agaroid plays the role of a flavoring agent.