Changing the tanning and coloring materials
The unroasted and roasted cocoa beans contain tannins that inform them astringent and bitter IKUSI in the literature tannins often called tannin.
There are two groups of tannins:
a) hydrolyzable tannins - a compound whose molecules phenolic nuclei are joined by oxygen atoms in increasingly complex. These substances have the nature of esters are easily cleaved by refluxing with water or with dilute acid or by the action of enzymes on compounds with smaller molecules and iron oxide to give salt dark blue staining;
b) condensed tannins, phenolic molecules whose nuclei interconnected carbon bonds. These substances are not able to undergo hydrolytic degradation. When heated with dilute acids by enzymes first representatives of this group of tannins do not break down into simpler substances; with oxides of iron salts, tannin gives this group of dark-green color. Under the action of strong acids, they condense, forming a so-called flabafeny.
Energetic exposure to alkaline carbon skeleton of tannins can be destroyed.
Of the group of hydrolyzed tannins most studied tannins.
Research has shown that the structure of tannin structure close to the glucoside, made up of glucose and five tannic acid residues
[(HE)2 - С6Н2 - CO - O - C6Н2(HE)2 - CO]5С6Н7О6
Pure tannin is a colorless to light yellowing amorphous powder, easily soluble in water, lower alcohol, anhydrous, almost insoluble in ether. An aqueous solution of tannin has oilno astringent taste and colors litmus paper red. Tannin has regenerative properties in alkaline solutions it rapidly absorbs oxygen from the air, and its solutions are colored with a dark brown color.
The most studied member of the group of condensed tannins is catechin
Catechin by itself does not have a tanning agent, but catechin compound or its derivatives to larger molecules formed tannins. Warming aqueous catechin solution entails a shift in the last tannins. Very often, such a transition is observed under the influence of enzymes, acids or alkalis.
In the fresh unfermented cocoa beans contain L-epicatechin, which represents, apparently stereoisomer catechin. L-epicatechin crystallizes as well?
betsvetnyh thin shiny needles, sparingly soluble in cold, but easily soluble in hot water, readily soluble in alcohol and acetone and is very difficult - in ether. The melting point of its 229 ° C. Strong rotates to the left. During fermentation the catechins pass in tannins.
It is found that in non-fermented tea contains L-epicatechin condensing during fermentation in tannins.
Tannins in the oxidation go into the compound, painted in brown-reddish color and called flobafenami.
Flobafeny substances are insoluble in water but soluble in alcohol, alkali and sulfuric acid.
Coloring characteristic cocoa beans depends to a certain degree on the presence in them flobafenov.
Tests have shown that in the fresh cocoa beans nefermetirovanyh catechin content reaches up from the 0,6 1%. During the entire fermentation proceeds in catechin tannin, catechin in fermented beans are not
All studies lead to the conclusion that the tannin fermented cocoa beans consist mainly of catechins condensation products.
Regarding the amount contained in the cacao beans of tannins, it varies depending on varieties of beans.
According to various researchers, the content of tannins in cocoa beans core ranges from up to 3 6%.
When studying the chair changes in the content of water-soluble tannins in beans Akra during roasting using the permanganate method found that the content of water-soluble tannins in fermented peeled beans (on dry substance) before roasting equal 3,43%, after roasting - 2,43 %.
Simultaneous determination of water-soluble tannins contained in roasted beans, according to the standard method is that of beans, an aqueous tannin extract, which is then treated skin powder, causing tannin precipitate.
Certain content on this method of tanning agents in the beans after roasting was 2,33%.
According to BV Kafka content of water-soluble tannins in cocoa beans reaches 3,6% in terms of dry matter. The roasted beans of tannins content decreases.
Decreasing the amount of tannins in the process of roasting the beans is also confirmed by the VP Insurance.
VA Reutov VP Strakhov and identified changes in the content of tannins in cocoa beans during roasting, using a standard method and obtained the following results (Table 7).
|Category beans Accra||The degree of fermentation||A method of processing||Moisture content in%||The fat content in%||Tannin content on a dry substance and a skim%|
To compare data of other authors with the above data, we recalculated the above table tannin content in the dry (non-fat) raw material and roasted kernels of cocoa beans and get the following values for the content of water-soluble tannins:
Accra, Accra 1 II Accra, Accra III IV Accra V
Raw beans. ... 3,08 3,84 3,93 3,91 3,99
Roasted beans 2,27 2,43 3,33 3,68 3,73
The content of water-soluble tannins in poorly fermented beans is higher than in well-fermented.
These different researchers data are in good agreement and suggest that the number of raw beans soluble tannins contained in the nucleus varies from 3 to 4%, in terms of dry matter and decreases under the influence of roasting up to 2-3% - Obviously, high temperature roasting contributes to oxidation processes, whereby a portion of water-soluble tannins becomes insoluble oxidized form.
Carried out by us in the department in 1957-1958 years. Research by roasting cocoa beans at different modes and methods have shown that the amount of tannins decreases to 1 -2,5%.
With regard to the above noted changes in the cocoa bean during roasting color transition due in part tannins flobafeny dark colored, it should be noted here that the color of the beans flobafeny affect not only, but also the cocoa beans contained in dyes.
Established that cocoa beans colorant refers to a group of anthocyanins, dyes, very widespread in the plant kingdom, particularly in fruits and flowers.
Anthocyanins are glycosides. When heated with acid (or by the enzymes) are cleaved pas sugar and a colorant, referred to as anthocyanins.
The isolated way or another potassium salt by treatment cyanine can translate in hydrochloric acid cyanine chloride which, as established by tests, has the formula:
С27Н31О16SI BM *2О.
This compound is a glucoside, which is cleaved by the action of acids on glucose and cyanidin:
С27Н31О16CL + H2A = C15H11O6CL + 2С6Н12О6.
Chloride Water Chloride Glucose
Cyanidin structurally resembles catechin. Indeed, optically inactive epicatechin was obtained from cyanidin chloride reduction with hydrogen in the presence of platinum.
This proves the close connection of catechins and formed one of tannins to anthocyanins.
It was found that fresh, unfermented and poorly fermented beans (Accra, Bahia, St. Tome) contains a coloring substance having the characteristic properties antotsiaiinov. This colorant has a purple beans it is highly soluble in alcohol, poorly in water and insoluble in ether, chloroform and benzene, and has a bitter and astringent taste. In neutral solution pigment has a magenta color; acid red dye in it, and the alkali - blue
Anthocyanins contained in the beans by fermentation, possibly under the influence of fruit pulp contained in the organic acids or enzymes to pass cyanidin, which in turn may pass through a condensing catechol tannins.
Thus, during roasting cocoa beans occur discoloration due to oxidation, not only tanning agents, but also due to changes in the composition of the beans contained in the coloring matter
In recent years, studies of tanning and coloring substances cocoa beans were used chromatography methods, which allowed more fully study the composition and the number of them.
A study of tannins chromatographic method in cocoa beans Amelonado established the presence of the four catechins (catechin, epicatechin, and gallokatehmn zpigallokatehin) and three leykotsianidov.
In another study, the same author has allocated chromatography of cocoa beans two major anthocyanin. One of them is a salt of cyanide pentose-glycoside, while others simply glycoside.
Acid hydrolysis them showed that both the anthocyanin derived from tsianizina.
Method chromatography revealed that as a result of changes in polyphenols during the fermentation and after drying West American varieties Amelonado cocoa beans derived anthocyanins and catechins leykoantotsianiny. After drying of fermented cocoa beans and leykoantotsianiny catechins found. Depending on the conditions and duration fermetatsii amount of phenols varies widely, ranging from up to 4 45% for anthocyanins from the 17 77% up to and catechins from the 19 87% up to leykoantotsianinov.
In addition to the changes discussed components of cocoa beans during roasting, note also the other: the transition of some of the starch contained in the beans from the insoluble to the soluble form and move a certain amount of cocoa butter from the kernel and the shell. At high temperatures, the amount of fat frying, passing the sheath reaches 1,4%. Finally, one of the most important changes in the beans during roasting, the development of the characteristic flavor.