Chemical interactions and protein conformations changes during the formation of silver carp surimi gel were studied by textural analysis, chemical methods, laser Raman spectroscopy, and circular dichrosim. The optimum setting time at 40 • C was 60 min. During surimi gel formation, ionic bonds and hydrogen bonds decreased significantly (P ≤ 0.05), while hydrophobic interactions, disulfide bonds, and non-disulfide covalent bonds increased significantly (P ≤ 0.05). Hydrophobic interactions, disulfide bonds, and non-disulfide covalent bonds were the main chemical interactions maintaining the stable structure of surimi gel. Secondary structural analysis of surimi protein showed that 94.11% α-helix existed in native myosin and it partly changed into β-turn and random coil during heating. Myosin gel was made up of 33.70% α-helix, 12.40% β-turn and 53.90% random coil. These three kinds of secondary structures were the main protein conformations in surimi gel.

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Gelatin extracted from the body wall of the sea cucumber (Stichopus japonicus) was hydrolyzed with flavourzyme. Low-molecular-weight gelatin hydrolysate (LMW-GH) of 700−1700 Da was produced using an ultrafiltration membrane bioreactor system. Chemiluminescence analysis revealed that LMW-GH scavenges high free radicals in a concentration-dependent manner; IC 50 value for superoxide and hydroxyl radicals was 442 and 285 μg mL -1 , respectively. LMW-GH exhibited excellent inhibitory characteristics against melanin synthesis and tyrosinase activity in B16 cells. Furthermore, LMW-GH notably increased intracellular glutathione (GSH), which in turn suppressed melanogenesis. LMW-GH performs antioxidation activity, holding the potential of being used as a valuable ingredient in function foods, cosmetics and pharmaceuticals or nutriceuticals.

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Proanthocyanidins with different polymerisation degrees were extracted from Chinese quince fruits by subcritical ethanol/water into four fractions (F1-F4), which were then analysed using UPLC-MS/MS, GPC and thiolysis combined with RP-HPLC MS and MALDI-TOF MS (matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry). The inhibitory effects of these proanthocyanidins on the formation of heterocyclic aromatic amines (HCAs), such as norharman, harman and PhIP, in chemical model systems were determined. The results reflected that the mean degree of polymerisation (DP) of proanthocyanidins in fractions F1, F2, F3 and F4 were 8.0, 12.7, 27.5 and 64.9, respectively. All four fractions prominently and dose-dependently reduced the formation of HCAs at concentrations of 0.5, 1 and 2 mg mL −1 in chemical models. F1, the fraction richest in oligomers, had the most effective inhibition of harman, norharman and PhIP, with the levels reduced by 65.71%, 37.15% and 72.99%, respectively, when used at a concentration of 2 mg mL −1 . The mean DP of proanthocyanidins showed negative correlation with the inhibition of HCA formation (R 2 = −0.697 for norharman, −0.799 for PhIP and −0.758 for harman). These findings suggest that proanthocyanidins from Chinese quince fruit have the potential to be used as additives to reduce the levels of heterocyclic amines in foods.

BACKGROUND: In recent years, cold-pressed oils have become more and more popular with consumers. However, their oxidative stability is low. Improving the oxidative stability of cold-pressed oils will increase their shelf life. Maillard reaction products (MRPs) have been shown to promote the oxidative stability of lipids. In this study, products from the Maillard reaction of reducing sugars and sesame enzymatically hydrolyzed protein (SEHP) were added to cold-pressed sesame oils to improve their oxidative stability. RESULTS: Three types of MRPs from reducing sugars (xylose, fructose, and glucose) and SEHP were prepared. Xylose-SEHPMRPs prepared under optimum conditions had the highest antioxidant activities among the three. The optimum conditions for xylose-SEHP were as follows: reaction temperature, 130 ∘ C; reaction time, 180 min; pH, 6.5; and sugar/protein ratio, 10:1. The addition of xylose-SEHP MRPs at a level of 20 g kg −1 could significantly improve the oxidative stability of cold-pressed sesame oil. Besides, the addition of MRPs reduced the loss of tocopherol. The interaction of MRPs with endogenous antioxidants in the sesame oil (sesamol and tocopherol) was proved by comparison with lard. There was a synergistic increase in antioxidant activity for the combination of MRPs and sesamol and the combination of MRPs and tocopherol. CONCLUSIONS: The results provide evidence that adding certain MRPs can improve the oxidative stability of cold-pressed sesame oil. mediate and final products of the Maillard reaction. The MRPs were diluted appropriately in order to obtain absorbance values of less than 1.5. J Sci Food Agric 2020; 100: 1524-1531

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