Source of putrefactive non-volatile amines and volatile basic nitrogen detected in kusaya [dried fish] products

The Japanese product “Kusaya” is made from fishes (mackerel-scad, flying fish, etc.) through processes of fermentation and drying. A survey of volatile basic nitrogen (VBN) and non-volatile amines, putrescine (Put), cadaverine (Cad), histamine (Him), tyramine (Tym) and spermidine (Spd), was carried out on 29 Kusaya samples which consisted of 12 broiled, 15 seasoned and 2 other products. VBN in the broiled products ranged from 220 to 520mg%, and that in the seasoned products ranged from 77 to 510mg%. In the broiled products, Put and Spd were detected in 8 samples, but the amounts were low: from 1.0 to 2.3μg/g and from 1.1 to 7.7μg/g, respectively. In the seasoned products, five non-volatile amines were detected at higher levels and with a higher frequency than in the broiled products. The amounts of Put, Cad, Him, Tym and Spd were 1.0-110, 1.0-380, 10-530, 9.1-67 and 1.2-5.5μg/g, respectively. Changes in the amounts of the five amines and VBN during the manufacture of Kusaya and Kusaya products were examined. The results imply that: (1) in the broiled products, Put originated from soakage fluid at the fermentation stage, whereas Spd was derived directly from the raw fish; (2) most of the five amines in seasoned products originated from soy sauce used in the seasoning; (3) VBN in both products originated from the soakage fluid.