Post mortem changes and spoilage in rock lobster muscle

Abstract

Summary Glycolysis in rock lobster comprising the oblique extensor, oblique flexor and enveloping muscles of Jasus novae‐hollandiae was studied under anaerobic conditions at 20°, 15° and 0°C. After bisecting the muscles along the mediosaggital plane one section was treated by dipping for 4 min in 3% sodium chloride solution containing 15 ppm oxytetracycline (treated). The other (untreated) was immersed in sodium chloride solution containing no antibiotic. In the treated muscles lactate production showed a linear relation to the fall in pH over a range of 7·2–6·0, a fall in one unit of pH corresponding to 118 μmol of lactate per g of tissue. In spite of a relatively high production of lactate the ultimate pH did not fall below 6·0 because of a high buffering capacity of the muscle. Breakdown of phosphoraginine and ATP and accumulation of lactate and inorganic phosphorus at 20° and 15°C followed patterns similar to those observed in mammalian and poultry muscle but at 0°C these processes were slowed down to a much greater extent. There was no accumulation of glucose 6‐phosphate. Concentrations of arginine rose as a result of phosphoarginine breakdown in both treated and untreated samples. However, in the untreated samples at 20° and 15°C, arginine concentrations started to fall 24 hr post mortem probably due to bacterial attack; the fall being more rapid at 20°C. When mounted in a specially designed rigorometer at 20° and 15°C the muscle strips started to shorten concurrently with only a slight drop in ATP concentrations. The extent of shortening did not exceed 10% of the original and in some cases the contraction was immediately followed by a slow lengthening. The findings of this study are discussed in relation to glycolysis and rigor mortis in mammalian and fish muscles.