Effects of relationships among freezing rate, ice crystal size and color on surface color of frozen salmon fillet

Relationships among freezing rate, ice crystal size, and color have been elucidated quantitatively to investigate the whitening effect on the surface of salmon fillet during freezing. Both surface color and ice crystal size, dependent on freezing rate, were measured at the surfaces of frozen gelatin as a model food and salmon fillet. As the ice crystal size on the surface layer of frozen product decreased, the surface showed lighter color with increase in values of L* and decrease in those of a* and b*. The fast freezing rate on the flesh surface markedly affected salmon color, indicating effective vertical depth within 0.3 mm at air velocity of 15.0 m/s with temperature of −35 °C. These methodologies based on quantitative demonstrations would provide adequate tools for the control of whitening effect by application of proposed relationships to industrial freezing equipment.