Use of the single cell gel electrophoresis assay (Comet assay) as a technique for monitoring low-temperature treated and irradiated muscle tissues

The influence of refrigeration, freezing, repetitive freezing-thawing, and irradiation on meat quality were evaluated by detecting DNA damage to beef muscle tissues using the single cell gel electrophoresis assay (Comet assay ). Comet tail lengths indicating DNA damage levels increased with refrigera tion time up to 10 days. In the case of frozen storage, the damage was incr eased only for the first 15 days of storage, but after that, decreased slig htly and the tail lengths at 15 days were similar to those of 35 days refri gerated storage. Tail lengths resulting from repetitive freezing-thawing we re increased after two cycles of treatment and three cycles produced longer tails than those that had been refrigerated for 10 days or kept in frozen storage for 60 days. Irradiation from 1 to 10 kGy caused the most serious D NA damage among the treatments compared in this study. The two kinds of mus cle tissue were similar in the pattern of results obtained from the Comet a ssay. The mean tail length of the comets reflected approximately the increa sing patterns of DNA damage, but the differences of values between the exte nts of treatment were somewhat insignificant and anomalous. Therefore, we u sed the concept of relative damage index (RDI) calculated from per cent cel ls data for each tail length range and representing a state of DNA damage. Significantly different values in RDI's made it possible to discriminate sa mples according to the treatment levels within each treatment.