Influence of Free Amino Acids, Oligopeptides, and Polypeptides on the Formation of Pyrazines in Maillard Model Systems

Abstract

Pyrazines are specific Maillard reaction compounds known to contribute to the unique aroma of many products. Most studies concerning the generation of pyrazines in the Maillard reaction have focused on amino acids, while little information is available on the impact of peptides and proteins. The present study investigated the generation of pyrazines in model systems containing whey protein, hydrolyzed whey protein, amino acids, and glucose. The impact of thermal conditions, ratio of reagents, and water activity (a(w)) on pyrazine formation was measured by headspace solid-phase microextraction with gas chromatography/mass spectrometry (HS-SPME-GC/MS. The presence of oligopeptides from hydrolyzed whey protein contributed significantly to an increased amount of pyrazines, while in contrast free amino acids generated during protein hydrolysis contributed to a lesser extent. The generation of pyrazines was enhanced at low a(w) (0.33) and high temperatures (>120 °C). This study showed that the role of peptides in the generation of pyrazines in Maillard reaction systems has been dramatically underestimated.

Partial purification and characterisation of the peptide precursors of the cocoa-specific aroma components

“…As shown by Maillard model systems, unsubstituted pyrazine was predominant in the case of free amino acids, whereas the amounts of generated alkylpyrazines were higher in the presence of peptides (Van Lancker et al, 2011). Obviously, the role of peptides in the formation of alkylpyrazines (and other flavour components) in Maillard reaction systems has been dramatically underestimated as recently reported (Scallone et al, 2015).…”

“…Alkylpyrazines are not unique for roasted cocoa beans, but are widespread in the volatile fractions of roasted foods. They are generated by Maillard reactions of both free amino acids and peptides with glucose (Scallone, Cucu, De Kimpe, & De Meulenaer, 2015;Van Lancker, Adams, & De Kimpe, 2011, 2012. Older studies on the formation of pyrazines in the Maillard reaction have largely focused on free amino acids.…”

“…The characteristic cocoa and chocolate aroma notes are generated during the roasting process by Maillard or nonenzymatic browning reactions, which involve the reactions of free amino groups of amino acids and/or peptides with reducing sugars (Afoakwa et al, 2008;Amrani-Hemaimi et al, 1995;Granvogel, Bugan, & Schieberle, 2006;Heinzler & Eichner, 1991;Scallone et al, 2015;Schnermann & Schieberle, 1997;Van Lancker, Adams, & De Kimpe, 2010;Van Lancker et al, 2011, 2012. Roasting of both the mixture and the individual aroma-related peptides identified in this communication in the presence of glucose and fructose with and without addition of free amino acids and subsequent comparative GC-mass spectrometry of the generated volatile products should enable the unequivocal identification of those compounds which really contribute to the specific cocoa and chocolate aroma.…”

Discovery of Amadori‐Type Conjugates in a Peptide Maillard Reaction and Their Corresponding Influence on the Formation of Pyrazines

“…Many researchers have found pyrazines to be more important than free amino acids in the peptide reaction system (Scalone, Cucu, De Kimpe, & De Meulenaer, ; Totlani & Peterson, ). Notably, van Lancker () reported that the production of 2,5(6)‐dimethylpyrazine and trimethylpyrazine was low in the case of Pro, Val, or Leu at the N‐terminus of X‐Lys dipeptides, whereas it was very high for Gly, Ala, or Ser.…”

“…In current studies, pyrazines, especially 2,5(6)‐dimethylpyrazine and trimethylpyrazine, constitute the most important volatile products identified in the peptide Maillard reaction system (Lu, Hao, Payne, & Ho, ; Zhang, Dorjpalam, & Ho, ). Scalone () found that the oligopeptides from hydrolyzed whey protein contributed more to pyrazine generation than free amino acids. The mechanism of pyrazine formation is widely known to occur through the condensation of α‐aminoketones formed from the interaction of α‐dicarbonyls and amines through Strecker degradation.…”