Characteristics of divalent minerals extracted from liver of Japanese common squid Todarodes pacificus under various experimental conditions

Abstract

In relation to the problem of how to utilize the waste from squid processing, we determined the proximate and mineral compositions of liver of the Japanese common squid Todarodes pacificus, and characterized the behavior of divalent minerals, focusing in particular on cadmium removal. The squid liver contained fat (44.0 g/100 g dry matter), protein (13.5 g/100 g dry matter), and ash (2.11 g/100 g dry matter). It also contained the macrominerals sodium, potassium, magnesium, and calcium, as well as the trace minerals iron, zinc, cadmium, and copper. Low- and high-pH treatments (pH 2 and 12) removed the cadmium entirely, but the trace minerals zinc, iron, and copper, as well as soluble protein, which are all important for proper functioning of the human organism, were also removed in large quantities. High percentages of soluble minerals and soluble protein were found in the low molecular weight (MW < 10,000) fraction. The solubility of zinc and copper were strongly related to the solubility of cadmium, but there was no relationship between the solubilities of magnesium and cadmium. On the other hand, while treatment with either 0.9 % NaCl or 100 mM phosphate buffer (pH 7.4) also removed the cadmium completely, it left some useful compounds (trace minerals and soluble protein) in the solid part, so these treatments may represent appropriate methods for removing cadmium from squid processing waste.