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Flavor Development during Cocoa Roasting
Published in Hii Ching Lik, Borém Flávio Meira, Drying and Roasting of Cocoa and Coffee, 2019
Another important route is the Strecker degradation, which leads either to volatile aldehyde, or to volatile pyrazines and other heterocyclic compounds. The Strecker degradation is one of the major pathways for pyrazine formation during the browning reaction. The pyrazine structure is dictated by the side groups on the dioxo compound. For example, the reaction between pyruvaldehyde and valine will produce 2-methyl-propanal and 2,5-dimethyl pyrazine, which have been described as having a nutty flavor. In cocoa, the pyrazines are abundantly available and can be used as tracers for the cocoa flavor (Bonvehí, 2005).
Development of flavor during drying and applications of edible mushrooms: A review
Published in Drying Technology, 2021
Lihui Zhang, Min Zhang, Arun S. Mujumdar
The characteristic carbonyl compounds α-aminoadipic and γ-glutamic semialdehydes produced by protein oxidation can react with free amino acids (FAA) to form Schiff base, which can produce Strecker aldehyde by Strecker degradation reaction, and then affect food flavor.[43] The mechanism of protein oxidation was similar to lipid oxidation, which was also caused by free radical chain reaction.[44] The carbonyl produced by protein oxidation was easy to form specific Strecker aldehydes. In the food processing, Strecker reaction also occurred to produce flavor components such as aldehyde and pyrazine.[45] High temperature during the drying process enhanced decomposition of protein into amino acids.[46] Carbonyl derivatives produced by amino acid side chain modification during protein oxidation will participate in Strecker degradation reaction, and then produce volatile flavor compounds (such as 3-methyl-n-butanol, 2-methyl-ethyl propionate, 2-methyl-ethyl butyrate, etc.).[47] Taking isoleucine as an example, under the oxidative stress of ROS free radical attack, isoleucine can generate amino free radical. There are two ways: one is that unpaired electrons are absorbed by metal ions to form amino ions, and then hydrated to form α-dicarbonyl compounds (AAS, GGS), and finally participate in Strecker degradation to form characteristic flavor compounds. Second, amino free radicals continue to react with other protein molecules to form protein free radicals, which are chain reactions of cyclic free radicals (as shown in Figure 4).[43] In the process of food drying, protein hydrolyzes formed a large number of FAA to form food flavor. High temperature in the drying process accelerated lipid oxidation, protein oxidation and hydrolysis without producing bad flavor.[6] This pathway primarily formed some sweetness, acidity and bitterness substances, which contributed to the flavor of food.[48] The benzaldehyde and phenylacetaldehyde were detected in the dried fillets due to the Strecker reaction during hot air and microwave drying.[49] And pyrazine in the dried carrots is a condensation of carbonyl compounds produced by the Strecker degradation.[50]