Influence of nitrate, ascorbic acid, and nitrate reductase microorganisms onN‐nitrosamine formation during Korean‐style soysauce fermentation

Abstract

Traditional Korean soysauce samples were collected from households in Chinju, Gyeongnam, Korea and analysed for volatile N-nitrosamines. Five of 24 samples contained NDMA (range = 1.6-10.4 micrograms/l) which was the only volatile N-nitroso compound found. Soysauce made from well water contained NDMA more often (4 of 6 samples) than soysauce made from tap water (1 of 18). This suggests that the water source is a determinate in the NDMA content of soysauce, probably due to a higher nitrate content of well water. The source of salt used did not clearly influence NDMA content. Soysauce was prepared in the laboratory using traditional methods but with 0 to 400 mg/l nitrate and in some cases made 6.5 to 65 mM in ascorbic acid and fermented for 120 days. The NDMA content of the samples was positively correlated with increasing nitrate concentration. Nitrate at 400 mg/l resulted in an NDMA content of 203 micrograms/l. Ascorbic acid substantially inhibited NDMA formation. All samples contained large numbers of nitrate reductase-containing organisms (greater than 1 x 10(7) CFU/ml).

Risk assessment of N‐nitrosamines in food

“…The presence of N‐ NAs (mainly NDMA) in soy sauce has been reported by various authors (Song and Hu, 1988 ; Park et al, 2015 ). Kim et al ( 1985 ) and Sung et al ( 1991 ) attributed levels of NDMA of ≤ 261.34 μg/kg in these products to tap water used during production and probably containing high nitrate levels. To date, this seems to be the main cause of N‐ NA residues in soy sauce.…”