Effects of different freezing methods on the quality and microstructure of lotus (Nelumbo nucifera) root

Abstract

The effects of three freezing methods, air blast freezing (ABF), immersion freezing (IF) and ultrasound-assisted immersion freezing (UIF), on quality and microstructure of lotus roots were investigated. The parameters used to evaluate the freezing methods effect were the freezing time, color, firmness, drip loss, vitamin C and microstructure of the final frozen products. The results showed that the UIF products had several advantages in terms of the freezing time, color, firmness and drip loss over ABF and IF. No significant difference (p > 0.05) of vitamin C content was observed between the ABF and IF products, while significant difference (p < 0.05) of vitamin C was observed between UIF and ABF/IF products. ABF caused the largest destruction to the tissue, while the microstructure of the UIF products was the best preserved. It is concluded that UIF processing was a better freezing method for lotus root with improved quality and less damaged microstructure than the two other methods.