Non-enzymatic browning in glucosamine and glucosamine-peptides reaction systems as a source of antioxidant and flavouring compounds

Abstract: Non-enzymatic browning is a common and complex reaction that occurs in everyday cooking—indeed, it is a crucial step in food processing. A typical browning process includes both the Maillard reaction and caramelization, which normally occur only at extreme temperatures to produce both desired and distinctive flavours and an intense brown colour in foods. On one hand, advanced stage Maillard reaction compounds can be toxic, such as acrylamide and 5-hydroxymethylfurfural (5-HMF). And yet on the other hand, Maillard reaction compounds can possess bioactivities including taste enhancing, antioxidant and antimicrobial capacities; collectively these are known as Maillard reacted peptides (MRPs). This bizarre paradox among non-enzymatic browning reaction compounds has long deserved a more in depth investigation under controlled conditions. To achieve these positive bioactivities yet reduce the accumulation of the harmful compounds associated with the Maillard reaction, a research strategy was proposed to produce and understand MRPs at lower temperatures. However, information on the antioxidant and sensorial properties MRPs at moderate temperatures is scarce. Glucosamine (GlcN) is an amino sugar recently revealed to be capable of triggering a fast Maillard reaction with protein at 25˚C. Additionally, due to the presence of both a carbonyl and amino group within the same molecule, GlcN can form substantial dicarbonyls at 37˚C—the precursors to desirable flavours. The main objective of this thesis was to study taste enhancement and antioxidant activity of GlcN-peptides in GlcN model systems. A total of 3 studies were designed representing the main building blocks of this project. The first study focused on the potential of GlcN to modifying protein hydrolysates at 25 and 37˚C in a fish gelatin hydrolysates-GlcN model. Modification of the hydrolysates by GlcN was accomplished by two approaches: firstly, a Maillard-based glycation with GlcN, and secondly, an enzymatic glycosylation catalyzed by the transglutaminase (TGase), condensing the primary amine group of GlcN with the carboxamide group of a glutamine residue in a peptide. GlcN-induced modification was achieved at both 25 and 37˚C, and the antioxidant and antimicrobial activities were improved compared to native hydrolysates. The second study focused on the taste enhancing property of GlcN-modified hydrolysed meat proteins produced at 37 and 50˚C in the presence or absence of TGase. Samples were formulated into seasoning compositions and evaluated by untrained consumers. The meat protein hydrolysate was perceived as the saltiest (p