High-pressure/temperature treatment effect on the characteristics of octopus ( Octopus vulgaris ) arm muscle

Abstract

Octopus muscle was pressurized at 200, 300 and 400 MPa for 15 min at 7 °C and 40 °C; treatments at 400 MPa continuously for 15 min and in three 5 min pulses at 7 °C and 40 °C were also carried out. Total viable counts of Enterobacteriaceae, Staphylococcus aureus and lactic bacteria, shear strength and autolytic activities were studied. High-pressure treatments reduced colony-forming units (cfu) for all groups tested, especially when applied in pulses at 40 °C, and caused a change of the predominant flora. Autolytic activity clearly decreased when pressure was over 200 MPa. When muscle is pressurized, shear strength increases although it is higher at lower pressures (200 MPa) than at higher pressure (400 MPa). When pressure was applied, morphological and ultrastructural changes were observed, mainly in the variation of fibrillar compacting, destruction of the sarcomere pattern, ultrastructural alteration of the myofibrils and gradual disappearance of the cell nucleus. The connective tissue was virtually unaffected by pressure despite the temperature applied.