Problems Involved in the Quantitative Extraction of Glycogen and High-Energy Phosphorus Compounds in Frozen Cod Muscle

Abstract

Extraction of cod muscle with 0.3 N perchloric acid followed by digestion of the residue in potassium hydroxide yielded an average of 16% more total glycogen than did classical digestion with 30% KOH. However, the differences tended to be less at higher glycogen levels. It was suggested that glycogen may be partially degraded during digestion with KOH, although no glycogenosis occurred during contact with alkali prior to heating. The proportion of residual glycogen not extracted by acid varied from 23% in unfrozen muscle to about 40% in liquid nitrogen-frozen and in slowly frozen muscle.Significant degradation of glycogen and high energy phosphorus compounds in frozen prerigor cod muscle was avoided by weighing samples in insulated beakers chilled by liquid nitrogen to prevent warming or thawing, and by homogenizing immediately on addition of acid extractant. Extraction with acid enabled the simultaneous determination of glycogen and phosphorus compounds on the same sample. Special sampling procedures were employed to reduce the sampling error due to variation in glycogen distribution along the fillet.