Inhibitory activity of a Concanavalin-isolated fraction from a glucosamine-peptides reaction system against heat resistant E. coli

Alcalase-derived gelatin hydrolysates were glycated with glucosamine in the presence (+) or absence (−) of transglutaminase (TGase), and their antimicrobial activities toward Escherichia coli AW 1.7 were studied. Glycation treatments were subjected to concanavalin A affinity chromatography to selectively collect the glycopeptide-enriched fractions and the changes in antimicrobial activity were determined. The minimum inhibitory concentration of glycated hydrolysates decreased by 1.2 times compared to the native hydrolysate, with no differences between (+) or (−) TGase treatments. No difference was observed in the dicarbonyl compound concentration between the two glycation methods except that 3-deoxyglucosone was greater in the TGase-mediated reaction. Concanavalin A-retentate, but not the flow-through fractions, significantly improved the antimicrobial activity, however there was no difference between +TGase and −TGase glycated treatments. Purification of the retentate fraction from fluorescent compounds did not improve its antimicrobial activity

Iron (Fe²⁺)‑Catalyzed Glucosamine Browning at 50 °C: Identification and Quantification of Major Flavor Compounds for Antibacterial Activity

Glucosamine browning at 50 °C with (GlcN/Fe²⁺) or without iron (GlcN) was studied over time from 0 to 48 h. Generation of reactive oxygen species (ROS), H₂O₂, and ¹O₂, along with α-dicarbonyls, fructosazine, and deoxyfructosazine, was evaluated. Singlet oxygen generation increased over time and was greater in GlcN/Fe²⁺ caramel solution. The presence of iron significantly increased the concentration of α-dicarbonyls at an early incubation time (3 h). Fructosazine and deoxyfructosazine were the major degradation products at 48 h comprising together up to 37 and 49% in GlcN and GlcN/Fe²⁺, respectively. GlcN/Fe²⁺ (48 h) exhibited a MIC₅₀ against highly heat-resistant Escherichia coli AW 1.7 at pH 5, but not at pH 7. Despite several antimicrobial compounds being produced during browning, GlcN/Fe²⁺ created a synergistic environment for the fructosazine-organic acids to confer their antimicrobial activity. GlcN caramel solutions have the potential to serve as both flavoring compounds and antimicrobial agents in formulated food systems