Rapid freezing using atomized liquid nitrogen spray followed by frozen storage below glass transition temperature for Cordyceps sinensis preservation: Quality attributes and storage stability
You Tian, Dongmei Li, Wenhuang Luo, Zhiwei Zhu, Wenjia Li, Zhengming Qian, Guangrong Li, Da-Wen Sun
Fresh Cordyceps sinensis (CS) is rich in bioactive components but perishable with a short shelf-life and drying is the most common method for its preservation. For better retention of its quality and nutritional values, an innovative preservation technique using rapid freezing based on atomized liquid nitrogen (LN) spray followed by frozen storage below glass transition temperature (Tg) was developed in the current study. Atomized LN spray freezing of CS at −60 °C (LN-60), −80 °C (LN-80) and −100 °C (LN-100) was performed. Freezing rates and quality attributes of CS including electronic conductivity (EC), drip loss (DL), total sugar content (TSC), superoxide dismutase activity (ASOD), basic colour information (L*, a* and b* values) and total colour difference (ΔE) were investigated, and the stability of CS stored at −40 °C, which was below the Tg, for 16 weeks was evaluated. The Tg of CS was determined as −34.86 °C through differential scanning calorimeter (DSC) analysis. Multivariate data analyses including principal component analysis (PCA) and cluster analysis (CA) verified that LN-80 and LN-100 provided CS with better quality indicators, among which, ΔE, DL, and EC were the most predominant ones. The stability test suggested that LN-80 and LN-100 minimized the quality deterioration of CS during the frozen storage.
Rapid freezing, Quality preservation, Multivariate data analysis, Principal component analysis, Cluster analysis