Uptake of thiol anti-browning agents by cabbage on blanching and reactivity during dehydration

Inhibitory effect of thiol compounds on browning precursors and intermediates in sorbitol/glycine system

BACKGROUND

Sorbitol as a sweetener is often thought to be unable to participate in the Maillard reaction causing browning. However, browning of a system was found to be significant when sorbitol was mixed with glycine and heated. The thiol compounds glutathione and cysteine were added to the system, and the inhibition mechanism of the two on the browning of the system was studied by combining the changes of precursor substances, intermediate products and browning degree.

RESULTS

When the concentration of thiol compounds reached 25 mg mL-1, both could make the browning inhibition of the system more than 80%, and the accumulated glucose concentration was reduced to <35% of the control. The production of 3-deoxyglucosone, a precursor of melanoidin, was significantly reduced.

CONCLUSION

Glutathione and cysteine directly inhibited the production of substrates in the sorbitol/glycine system, reduced glucose accumulation through competitive consumption and captured highly active intermediates through sulfhydryl groups. This has implications for the browning control of food systems containing sugar alcohols. © 2024 Society of Chemical Industry.

Color and structural modifications of alkaline extracted sunflower protein concentrates and isolates using L-cysteine and glutathione

Alkaline sunflower protein extraction can be performed along with de-phenolization of sunflower seed proteins if greening is unwanted. This greening is promoted at alkaline pH when chlorogenic acid (CGA) oxidizes and reacts with amino acids such as lysine. Thiol-containing dough conditioners: L-cysteine hydrochloride and glutathione (GSH) were investigated as an alternative de-greening strategy to acidification and de-phenolization. Greening and browning inhibition of thiols (GSH and Cysteine) were modeled by a combination of additive and interaction effects of extraction pH (7.0 to 11.0) and thiol concentration (0.00 to 5.60 mM) randomly assigned by Response Surface Methodology (RSM). The powders with the highest greening were the controls (pH 8.9-9.3 and no added thiols) and powders at pH 10.41 with 0.82 mM thiols. From RSM, the maximum greening inhibition was achieved at pH 8.71 and 4.23 mM cysteine, and pH 8.51 and 3.78 mM GSH. However, cysteine caused more browning at alkaline pH than GSH. Furthermore, fluorescence spectroscopy showed that cysteine had a protective effect against alkaline unfolding, whereas GSH quenched fluorescence in a concentration-dependent manner. Overall, de-greening of alkaline extracted sunflower protein was achieved by adding cysteine or glutathione, but the thiols differed in their contribution to the browning and unfolding effect.