Studies on Greening of Canned Shellfishes

Part VIII. On the effect of manufacturing condition and that of metals on the greening of Canned oysters

Abstract

The greening of oysters is frequently found in the sterilization process of canning. In the present paper, the effect of the manufacturing conditions, as sterilization temp, and time, pH value of juice, and the presece of metals, on the greening phenomenon were investigated. The greening degree was estimated by measuring the optical-density at 420 and 620mμ in hydrochloric acid-acetone extract, and taking the ratio of 660:420. Canned oysters turned green during sterilization at 90°C for 20min. or at 110°C for 10min. The manufacturing conditions, as sterilization temp. and time, as well as vacuum degree have no effect on the greening. While, in case of acidic juice, the oysters turned green; in case of alkaline one, they turned brown. The presence of metals, as magnesium, iron, zinc or copper has no effect on this reaction.