Nippon Eiyo Shokuryo Gakkaishi (J. Jpn. Soc. Nutr. Food Sci.) 36, 133-140 (1983) In a previous paper the authors reported that the discoloration by the reaction in boiled and dried Euphausia superba among autoxidized unsaturated fatty acid and volatile basic nitrogen (VBN) or non-volatile (Non-VBN) assumed to be influenced by the amounts of nitrogenous substance in VBN and Non-VBN fractions.
In this paper, the influence of pH, some inorganic ions such as Cu²⁺, Fe²⁺ and the water-soluble browning substance separated from boiled and dried E. superba on discoloration was investigated.
The following results were obtained.
(1) The browning intensities of hydrophilic Non-VBN (F-1), lipophilic Non-VBN (F-2), hydrophilic VBN (F-3) and ipophilic VBN (F-4) fractions were measured with E value at 430 nm. The results indicate that the effect of pH (among 5 to 9) on browning intensities was not observed in any fraction even after 120 hr incubation.
(2) The browning intensities of F-1 and F-2 fractions, peroxide value and thiobarbituric acid value increased by addition of 100 or 300 ppm Fe²⁺ and Cu²⁺. Fe²⁺ showed stronger effect than Cu²⁺.
(3) The browning substance which was analyzed by fluorescence intensity, ultraviolet and infrared spectrophotometry, was suggested to be quite similar to melanoidin.