Monitoring of Functional Components (Nattokinase, Vitamin K 2 -MK7, and Poly-γ-Glutamic Acid) in Commercial Natto Products Distributed in Korea

This study integrated newly measured nattokinase (NK) and vitamin K 2 -MK7 data with previously reported poly-γ-glutamic acid (γ-PGA) data in the same 19 commercial natto products distributed in Korea.It compared these three functional components according to the storage conditions, raw bean type, and bean origin.The NK activity was measured using a fibrin-degradation assay according to the JHNFA standard method, while γ-PGA and vitamin K 2 -MK7 were determined by alum-ethanol precipitation followed by UHPLC amino acid analysis and by lipase hydrolysis followed by hexane extraction and UHPLC, respectively.The mean contents of the 19 products were NK 60.89± 11.38 FU/g (39.82-79.51),vitamin K 2 -MK7 502.25±182.89μg/100 g (238.64-824.35),and γ-PGA 732.69±176.17mg/100 g (431.26-1,108.27),with substantial product-to-product variation.Yellow soybean products (n=13) contained 24.0% higher γ-PGA than blackbean products (n=6), a statistically significant difference (P=0.034).Domestic-bean products (n=14) contained 33.5% lower vitamin K 2 -MK7 than imported-bean products (n=5) (P=0.008).No significant differences were observed in the remaining comparisons, including γ-PGA according to the storage conditions (P=0.063) and vitamin K 2 -MK7 according to the bean type (P=0.062), and no significant correlations were found among the three components.No single product ranked highest in all three.These between-group differences should be interpreted as descriptive observations within a limited sample set rather than as effects of the individual variables because manufacturer, starter strain, and process conditions varied simultaneously among the products.This is the first exploratory report to integrate NK, vitamin K 2 -MK7, and γ-PGA data in the same commercial natto sample set.