Effect of liquid nitrogen spray quick-freezing technology on the quality of bamboo shoots, Dendrocalamus brandisii from Yunnan Province, China

Abstract

This study explored the effects of liquid nitrogen spray quick-freezing (LNF) on the quality of fresh bamboo shoots. The results showed that the low temperature damaged bamboo shoots and caused a loss of nutrients after freezing. Notably, liquid nitrogen spray quick-freezing technology significantly improved the freezing efficiency and quality of the sample compared with the refrigerator freezing at −20 °C. The bamboo shoots that underwent LNF at −80 °C (LNF-80 °C) suggested the best results, with a 92.73% reduction in passing the zone of maximum ice crystal formation time, 60.23% reduction in thawing loss, 79.32% increase in hardness and 33.61% decrease in peroxidase activity compared that of refrigerator freezing at −20 °C. On the nutrients, the total amino acid content in the LNF-80 °C bamboo shoots (133.31 mg/100 g) increased by 25.50% compared with that in bamboo shoots that were slowly frozen (835.24 mg/100 g). Furthermore, the LNF-80 °C group samples had the most uniform water distribution, and the microstructure of this sample was the least damaged by ice crystals. These results show that LNF technology has great potential to improve the quality of frozen fruits and vegetables.