Comparisons of aroma extracts of heat-treated cereals

Changes in phenolic profiles and antioxidant activities during the whole wheat bread-making process

Health benefits of whole wheat products are partially attributed to their unique phenolic profiles. This study investigated the effect of bread-making processes on the phenolic profiles and antioxidant activities of four different varieties of hard red winter wheat. The fermentation process generally increased soluble phenolic content, flavonoid content, antioxidant activities, and soluble ferulic acid of whole wheat products. The baking process increased the soluble phenolic content and antioxidant activities. Some phenolic acids were incorporated into Maillard reaction products during baking. For the insoluble fraction, fermentation and baking slightly increased phenolic content, flavonoid content, and antioxidant activities of certain wheat varieties. Ferulic acid and isomers of di-ferulic acid (DFA) were not significantly affected by the baking process. Overall, the bread-making process demonstrated positive effects on the potential health benefits of whole wheat products.

Role of the ribose-specific marker furfuryl-amine in the formation of aroma active 1-(furan-2-ylmethyl)-1H-pyrrole (or furfuryl-pyrrole) derivatives

Furfuryl-pyrroles possess a diverse range of organoleptic properties described as roasted, chocolaty, green, horseradish-like, and mushroom-like and are detected in various foods such as coffee, chocolate, popcorn, and roasted chicken. Although their origin in food was attributed to furfuryl-amine, the latter has not been detected so far in Maillard model systems or in foods. In this study, furfuryl-amine was shown to be formed specifically from ribose through nitrogen atom transfer from the α-amino group of any amino acid. Such a transfer can be achieved through decarboxylation of the Schiff base adduct and isomerization followed by hydrolysis. Through the use of (15)Nα-lysine it was revealed that only the (15)Nα nitrogen atom was incorporated into its structure, indicating a specific role for the carboxylate moiety in the mechanism of its formation. Furthermore, isotope labeling studies have indicated that furfuryl-pyrrole derivatives can be formed by the interaction of 2 mol of furfuryl-amine with 3-deoxyribosone followed by dehydration and cyclization to form 1-(furan-2-yl)-N-{[1-(furan-2-ylmethyl)-1H-pyrrol-2-yl]methylidene}methanamine. After hydrolysis, this intermediate can generate furfuryl-formyl-pyrrole, furfuryl-pyrrole carboxylic acid, and furfuryl-pyrrole. In this study, the furfuryl-amine derivatives were also detected in different coffee beans after pyrolysis and analysis by GC-MS. The potential of these compounds to form in aqueous model systems at a temperature of 120 °C was also demonstrated.

Analysis of volatile compounds and their contribution to flavor in cereals

Recent developments in methods for isolation and measurement of volatiles from cereals are reviewed. The main types of isolation methods, namely, direct extraction, distillation, and headspace, have recently been complemented by solid phase microextraction. Direct solvent extraction provides efficient recovery of compounds with a broad range of polarities and volatilities, whereas headspace techniques provide relatively clean extracts. Supercritical fluid and solid phase microextractions have not yet been fully evaluated for cereals. GC and GC/MS remain the dominant techniques for measurement of the extracted compounds, although new electronic noses show promise. Relating these results to human perception requires careful control to ensure valid comparisons and, in this respect, aroma extract dilution analysis is a useful procedure.

Comparison of volatile generation in serine/threonine/glutamine-ribose/glucose/fructose model systems

Thermal generation of volatiles in nine model reactions was studied and compared. Each of the model systems contained one amino acid and one monosaccharide. The amino acid was serine, threonine, or glutamine, and the monosaccharide was ribose, glucose, or fructose. More unsubstituted pyrazine was generated in serine-sugar systems than threonine-sugar systems. The formation of several furfuryl-substituted pyrazines and pyrroles was observed in some of the studied systems. Total pyrazines were generated more in glutamine-containing systems than in serine- and threonine-containing systems, and the reverse was true for generation of furfuryl-substituted compounds. Acetylpyrazine was generated in serine/threonine/glutamine-glucose and serine/glutamine-fructose systems.