Sous-Vide Nonenzymatic Browning of Glucosamine at Different Temperatures

The effects of reaction parameters on the non-enzymatic browning reaction between l-ascorbic acid and glycine

The non-enzymatic browning (NEB) reaction between l-ascorbic acid (ASA) and glycine (Gly), including the effects of temperature (110–150 °C), time (10–150 min) and pH (4.5, 6.8, 8.0 and 9.5) on the formation of un-colored intermediate products (UIPs), browning products (BPs) and volatile products (VPs), were investigated. The results showed that pH had a remarkable effect on the reaction. The characteristics of zero-order kinetics for the formation of UIPs and BPs were discussed, and the corresponding activation energy (E a ) was also calculated. When the pH was 4.5, the E a for the formation of UIPs was approximate 53.76 kJ/mol and less than that at other pH values; while the E a for BPs formation was approximate 94.06 kJ/mol and much higher than that at other pH values. The results suggested that an acidic environment facilitated the generation of UIPs, but did not remarkably promote the formation of BPs. The possible reaction pathway between ASA and Gly was proposed according to the experimental results.

Efficient conversion of chitin-derived carbon sources into microbial lipid by the oleaginous yeast Cutaneotrichosporon oleaginosum

Chitin represents the second most abundant biomass after lignocelluloses in the biosphere. It can be depolymerized into either N-acetylglucosamine (GlcNAc) or glucosamine (GlcN) and acetate by different degradation strategies. However, these chitin-derived carbon sources have been scarcely compared for lipid production. Here, GlcNAc was found superior to GlcN or acetate for lipid accumulation by Cutaneotrichosporon oleaginosum. The lipid accumulation potential of these carbon sources was calculated based on a small scale metabolic model of C. oleaginosum. Co-fermentation of GlcN and acetate under phosphate limitation rendered improved lipid production. GlcN and acetate were assimilated simultaneously. The highest lipid titer and yield of 10.1 g/L and 0.25 g/g, respectively, was reached when GlcNAc was used under phosphate limitation. The fatty acids composition of the lipid samples showed similarities to vegetable oils, demonstrating the suitability in biodiesel industry. This study provides profitable guidance for the design of chitin-to-lipids routes.

The effect of glucosamine and glucosamine caramel on quality and consumer acceptability of regular and reduced salt breakfast sausages

Given the more recent interest in its flavour enhancing potential, the effects of the addition of glucosamine or glucosamine caramel on both technological and consumer acceptability of regular and reduced salt breakfast sausages were studied. A 2 × 3 complete factorial design was used with salt level (regular salt, RS (1.1%) and low salt, LS (0.825%)) and formulation treatment (control, GlcN - glucosamine (1%), CAR - glucosamine caramel (1% GlcN equivalent)) as main effects. Raw or cooked sausages were analyzed for CIE L*, a* and b*, physical and textural properties and consumer acceptance. Different salt levels did not affect the pH of meat batter, while the reduced salt treatment resulted in higher cook loss. On the contrary, addition of GlcN and CAR reduced the pH of sausage with no effect on cook loss. Neither salt levels nor treatment formulation affected the textural attributes of sausages. The inclusion of CAR significantly reduced L* value and increased redness (a*) and yellowness (b*) of cooked sausages. Salt reduction resulted in decreased a* and b* values in raw batter; the effect which disappeared in cooked sausages. Glucosamine caramel increased the overall and flavour acceptability score of low salt breakfast sausages. The present study showed that glucosamine caramel could potentially improve the flavour of low salt breakfast sausage with limited effect on textural attributes.

The effect of amino acids on non-enzymatic browning of glucosamine: Generation of butterscotch aromatic and bioactive health compounds without detectable levels of neo-formed alkylimidazoles

A mixture of glucosamine (GlcN, 15% w/v) and different amino acids in 1:1 M ratio was incubated at 70 °C for 12 h. The resulting GlcN-amino acid caramels were analysed for α-dicarbonyl compounds, polyhydroxyalkyl pyrazines, heterocyclic compound and alkylimidazoles. All the analyses were performed by using HPLC-MS/MS followed by pooling the variables with principal component analysis (PCA). GlcN-Gly caramels generated the greatest amount of butterscotch aromatic compound diacetyl and polyhydroxyalkyl pyrazines (fructosazine and deoxyfructosazine). The potentially toxic heterocyclic compound, 5-hydroxymethylfurfural (HMF) was generated in greater amounts with the GlcN-Arg caramels. However, the toxic alkylimidazoles (4-MEI and THI) were not present in any of the GlcN-amino acid caramels. The results suggest that caramel with butterscotch aroma and bioactivity can be produced with GlcN-amino acid at 70 °C. The PCA performed discriminated the majority of the GlcN-amino acid combinations; GlcN-Gly and GlcN-Ser were best discriminated.