Freezing rate and frozen storage effects on the ultrastructure of samples of pork

Cryo-scanning electron microscopy was used to study the ultrastructure of small samples (approximately 6 g) of pork. Combinations of six freezing rates, two storage times and three thawing rates were used. Cavities created after sublimation of the ice crystals were quantitatively analysed using an image analysis software package. The cross-sectional areas of cavities of meat samples in the frozen state were approximately ten times the areas of the cavities of the fresh and thawed samples. The large cavities in the frozen state grossly distorted the muscle cell structures. Upon thawing, the meat structure had almost completely recovered. No significant freezing rate effects were observed, however, trends were evident. Significant storage time effects were observed. In the frozen state, at the 90th percentile level, the hole area fraction was greater in stored samples for intermediate cavity areas. In thawed samples, hole area fractions of stored samples were greater than in samples without storage.