Seawater bittern (
nigari) is a concentrated solution remaining after the crystallization process of salt that has been used as a coagulant for
tofu. Recently, various
nigari products are distributed in the East Asia. To clarify the properties of
nigari products, major mineral composition of six
nigari products was determined. Then, effects of the
nigari on the browning and antioxidant activity during the glucose/lysine Maillard reaction were investigated. Though the predominant cation was Mg
2+, the content was varied by each product (0.88–6.49 mol/L). The other major ion contents were also varied. Each 0.5 mol/L of
d-glucose and
l-lysine were incubated with the
nigari (5–50 % (
v/
v)) or
nigari-related salts (1 or 2 mol/L). The browning (OD at 465 nm) and antioxidant activity (1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging capacity and ferrous-reducing power) were increased remarkably by the
nigari containing high Mg
2+ content. The browning tended to be high with sulfates (Na
2SO
4, (NH
4)
2SO
4). On the other hand, high content of MgCl
2 decreased slightly the browning and antioxidant activity. These results suggest that the reaction and antioxidant activities were affected not only by salinity and cations but also by anions and other elements in the
nigari.
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