Quality improvements to mackerel (Scomber japonicus) muscle tissue frozen using a rapid freezer with the weak oscillating magnetic fields.

Although freezing is the most popular long-term food preservation method, the formation of ice crystals during the freezing process often degrades the quality of the product. Recently, several reports have argued that oscillating magnetic fields (OMFs) may affect ice crystallization. In this paper, we investigated the effects of OMFs on fresh mackerel using the Cell Alive System® (CAS®) developed as an additional OMF generator for a rapid freezer. Mackerel fillets were frozen with home freezing (HF), air blast freezing without (ABF) or with CAS (ABF-CAS) (ABI Co. Ltd., Chiba, Japan), and stored them for 2 weeks in the frozen storage between -30 °C and -35 °C. We analyzed the tissue damages of thawed samples histologically. The OMFs has been shown to significantly inhibit tissue damage in mackerel tissue after freezing and thawing (especially, thawing in ice water). And it seems that OMFs suppressed the ice hole counts (p < 0.05), the mean size (p = 0.061), and the increase of interstitial area% (p < 0.05) after freezing/thawing. We also found that it is necessary to avoid re-crystallization during thawing to maintain the quality of the frozen product. The use of OMFs with rapid thawing has the potential to improve cryopreservation in the food industry as well as in the bioscience industry.