The researchers studied how the oil in red carp fish changes when frozen for up to 9 months at -18°C. They found that the fatty acids in the fish oil, like linoleic acid and EPA, are good for health. However, during frozen storage, the oil quality decreased. The levels of free fatty acids and peroxide increased, while the ratio of healthy fatty acids to saturated fats decreased. This means that for the best quality, red carp fish should be stored for less than 3 months at -18°C.