Effect of low-dose irradiation and refrigeration on the microflora, sensory characteristics and biogenic amines of Atlantic horse mackerel (trachurus trachurus)

Abstract

Fresh Atlantic horse mackerel (Trachurus trachurus) were gamma irradiated at 1 and 3 kGy, and stored in ice for 23 days. Quality changes during ice storage at 0±1 °C were followed by sensory analysis and the determination of total viable count, histamine, cadaverine, putrescine, tyramine, agmatine, spermidine, trimethylamine and volatile basic nitrogen contents. The control lot had a sensory shelf life of 8 days, whereas those of the irradiated lots were extended by 4 days. TVC’s and levels of amines increased in all lots with storage time, their contents being significantly reduced by irradiation, even when the lower level (1 kGy) was used. Histamine in the irradiated lots was undetectable when the fish was spoiled at the end of 23 days, whereas in the control lot, the concentration did not exceeded the maximum allowed in fresh fish (100 mg/kg). Presumptive identification of microorganisms gave a majority aerobic or facultative Gram-negative anaerobic rods being Gram-positive bacteria circa 10–18% in irradiated samples. Chemical indices were shown to be unsuitable for the determination of the quality changes in irradiated fish.