Effect of physicochemical properties on freezing suitability of Lotus (Nelumbo nucifera) root

• Near infrared spectroscopy was efficient to reduce the time and cost of detecting process.
• Six principal physicochemical properties of lotus root were obtained.
• Higher starch content of lotus root was more suitable for freezing processing.
• Quality improvement of ultrasound-assisted immersion frozen lotus root with high content starch was achieved.

The initial physicochemical properties of different lotus roots were studied with the aim to evaluate their influence on freezing suitability. Six physicochemical properties indicators (starch content, whiteness index, maximum diameter, protein amount, titratable acidity and vitamin C) of lotus root were determined by principal component analysis. It was observed from the experimental results that the initial physicochemical properties of lotus root can directly affect the freezing suitability in terms of initial freezing temperature, transition phase time, total freezing time, relative firmness and drip loss. Correlation analysis suggested that relative firmness increases in proportion to starch content, and initial freezing temperature and drip loss are inversely proportional to the starch content. Compared to immersion freezing, power ultrasound can significantly improve the freezing rate and relative firmness but decrease drip loss. These results suggested that high quality frozen lotus root can be achieved via appropriately selecting high starch content lotus root and using ultrasound-assisted immersion freezing.