Preparation and characterization of white shrimp hydrolysate–xylooligosaccharide Maillard products and their in vivo promotive effects of zinc absorption in mice

The Maillard reaction products, as a kind of glycosylation-based reaction, possess the metal-chelating ability. In this study, the white shrimp hydrolysate (WH) and xylooligosaccharides (XOS) were used to prepare the Maillard reaction product-zinc complex (WH-XOS-MR-Zn) with zinc ions. The Maillard reaction conditions, such as pH level, temperature, reaction time, and the ratio of XOS to WH, were selected by testing the products' zinc-chelating capacity, while the optimized conditions (zinc-chelating capacity = 64.8%, pH = 7, 110 °C, 180 min, XOS : WH = 2) were finally determined. The interactions between WH-XOS-MR and zinc were confirmed and characterized by various kinds of techniques and triggered new peaks of fluorescent signals. The addition of zinc in WH-XOS-MR induced the proportion changes of secondary structures, including the decrease of β-sheets (8.16%) and the increase of β-turns (5.9%) and random coils (2.23%). The addition of zinc changed the morphological surface appearance of WH-XOS-MR and the crystal signal was completely covered in the WH-XOS-MR-Zn complex involved in the chelation with carbonyl and amino groups. The high-dose and medium-dose of the WH-XOS-MR-Zn complex showed higher promotive effects on zinc absorption (11.89 and 11.05 umol L^-1, respectively) and medium-dose recovered values of AKP (liver and serum: 7.15 and 12.53 U mL^-1), SOD (liver, kidney and serum: 59.84, 7.86 and 13.61 U mL^-1) and GSH-Px (203.22 U per mgprot), damage to testicular tissues, damage to the intact neuron cells in the hippocampus region (CA1: 54 to 61, CA3: 67 to 136, DG: 219-353), and intestinal inflammation compared with the zinc-deficient mice. These findings showed therapeutic benefits of Maillard products on intestinal health and cellular structures.