Amino acids chocolate

Although flavor precursors in the unroasted cocoa bean have no significant chocolate flavor themselves, they react to form highly flavored compounds. These flavor precursors include various chemical compounds such as proteins, amino acids, reducing sugars, tannins, organic acids, and many unidentified compounds. 

The natural moisture of the cocoa bean combined with the heat of roasting cause many chemical reactions other than flavor changes. Some of these reactions remove unpleasant volatile acids and astringent compounds, partially break down sugars, modify tannins and other nonvolatile compounds with a reduction in bitterness, and convert proteins to amino acids that react with sugars to form flavor compounds, particularly pyrazines (4). To date, over 300 different compounds, many of them formed during roasting, have been identified in the chocolate flavor (5). 

Table 10. Amino Acid Content of Cocoa and Chocolate Products,. mg/g ...

MS milk chocolate = 20% whole milk sohds, 13% hquoi, 33% total fat. Total AA lecoveied = sum of individual amino acids (qv). 

Chocolate flavored syrup, theobromine and caffeine content, 6 367t Chocolate liquor, 6 355-358 amino acid content, 6 368t composition, 6 369t... 

The results of this survey of the aromas produced over time by heating glucose—amino acid mixtures at a series of temperatures in the range 100-220° proved of great interest. Many mixtures were heated in the "dry" statB for the first time. Some produced the expected result, for example, methionine and phenylalanine led to potato and to floral aromas, respectively. Others were unexpected, for example, the large number of amino acids that was capable of producing chocolate aroma under one or other set of conditions. 

Rohan had suggested that the operative reaction in the development of chocolate aroma might be a Strecker degradation of the amino acid fraction. Bailey et al. (8) demonstrated quantitatively that three aldehydes, which could be related to leucine, valine, and alanine, were prominent in the volatiles from a typical sample of roasted, ground cacao beans. 

One o-f the world s most popular -flavors, chocolate, is a product o-f both -fermentation and roasting. Early studies by Rohan (44-47) pointed out the importance o-f liberating the precusor materials (amino acid) so that roasting will generate chocolate aroma. 

Some 350 other volatiles have been identified in chocolate aroma, and about 10% are pyrazines (48— 51) and quinoxalines (52). During roasting 49% of the total free amino acids are lost with only 4% of the bound amino acid being lost (53). 

Destruction of Amino Acids and Peducing Sugars on Heating Chocolate Aroma Precursor Extract... 

Moisture content of the reaction mixture Influenced the degradation of amino acids. Rohan and Stewart (52) reported that chocolate precursor aroma extracts when heated in the dry state for one hour at 100°C., lost 30% of the amino acids by degradation. When very lightly moistened the amino acids degradation dropped to 9% under the same reaction conditions. 

Special flavor formation for crumb chocolate takes place in the plant shown schematically in Fig. 14.28, left. In this system, so-called Maillard reactions between amino acids and reducing sugars occur in 1 to 2 minutes at 130°C, producing the classic flavors usually found in Great Britain, Scandinavia, and Japan. The process requires a few percent of moisture, which is added separately and removed in the vacuum after the reaction. The ZSK process saves on expensive vacuum dryers requiring several hours residence time. 

Enzymatic Modification of Proteins for Food Use. Proteolytic enzymes are used extensively for modifying proteins in various ways in food products and for waste management (17, 27. These are used in baked and brewed products, cereals, cheese, chocolate/cocoa, egg and egg products, feeds, fish, legumes, meats, milk, protein hydrolysates and wines. But there are many other uses, and potential uses, of enzymes to modify protein. Whitaker (27, 28), and Whitaker and Puigserver (29) have described more than 100 enzymatic modifications of proteins in vivo, challenging scientists to look at the possibilities of modifying the amino acid side chains by proteolytic and other methods. 

Flavourings that are useful for aromatising bakery and chocolate food products can be made from sulphur-free amino acids by the reaction with cyclic ketones (Fig. 3.36) such as 4-hydroxy-2,5-dimethyl-3(2//)-furanone (26), maltol (63) or 2-hydroxy-3-methyl-2-cyclopenten-l-one (64, cyclotene) [109]. Amino acids of special interest are leucine, valine, proline and hydroxyproline. The reaction is carried out favourably in fat or propylene glycol. 

More specific flavors have been obtained by substituting specific amino acids and specific sugars. An example is the microwave reaction of Glucose, Phenylalanine and Leucine by Byrne and Buckholz to get a chocolate tasting flavor. 

Chocarom Pyrazine isomers were isolated from the skin and flesh of potato Solanum tuberosum L.) cultivars after baking 4). 3,5-Dimethyl-2-isobutylpyrazine [2,5-dimethyl-3-(2-methylpropyl)-pyrazine] was isolated by Oruna-Concha, Craig, Duckham and Ames from the following potato cultivars - Cara, Nadine, Flanna and Marfona. 3,6-Dimethyl-2-isobutyl-pyrazine [3,5-dimethyl-2-(2-methylpropyl)pyrazine], was found by the same team in Cara and Marfona potato cultivars. 2,5-Dimethyl-3-isobutylpyrazine was also detected by Welty, Marshall and Grun in chocolate ice cream prepared from cocoa flavor (5). Both pyrazines were also found as key odorant compounds in dark chocolate by Counet, Callemien, Ouwerx and Collin (6). The role of amino acids in alkyl-substituted pyrazines formation in model systems containing pyruvaldehyde was examined by Mea (7). 2,5-Dimethyl-3-isobutylpyrazine was formed in the model system with valine. Both isomers were prepared synthetically by Chen (S) by reacting acetol, isobutyraldehyde and ammonium acetate, with low yield of 22.3%. Subsequent proprietary work by the author has improved the yield to 65%. 

Nearly all foods are made up of a complex mixture of components, including carbohydrates, amino acids, and proteins. When these foods are heated, the Maillard reaction occurs resulting in the formation of a large variety of volatile flavor compounds (1-3). The Maillard reaction is responsible for both desirable and undesirable aromas in foods. The aroma of bread, chocolate, coffee, and meat are all examples of desirable aromas resulting from the Maillard reaction. The aromas of burned food, canned products, stale milk powder, cereal, and dehydrated potatoes are typical examples of the undesirable aspects of this reaction. 

Blood meal is a chocolate-coloured powder with a characteristic smell. It contains about 800 g/kg of protein, small amounts of ash and oil, and about 100 g/kg of water. It is important nutritionally only as a source of protein. Blood meal is one of the richest sources of lysine and a rich source of arginine, methionine, cystine and leucine, but it is deficient in isoleucine and contains less glycine than fish, meat, or meat and bone meals. Owing to the poor balance of amino acids, its biological value is low in addition, it has a low digestibility. It has the advantage, in certain situations, that its protein has a very low rumen degradability (about 0.20). 

The amount of flavonoids and flavanols in cocoa and chocolate might be highly variable and this variability is multifactorial. For example, plant s genetic predisposition dictates the biosynthesis of the primary (sugars, amino acids, etc.) and secondary metabolites (proanthocyanidins, saponins, alkaloids, etc.) while genetics can cause as much as a fourfold difference in flavan-3-ol content of fresh cocoa beans [22, 23]. Variability with respect to secondary metabolites exists between varieties (or cultivars) of the same species. However, various environmental factors determine the extent to which genetic potentialities are... 

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