Study on quick freezing blueberries on LN2-spraying fluidized freezer

Liquid nitrogen (LN2) fluidized bed for freezing was used to process blueberries by setting different freezing temperatures, wind velocities, and bed-layer heights. The experimental procedure was comprised of regular and mixed experimental designs. The blueberries were tested under six quality indicators, including vitamin C, anthocyanins, water loss rate, soluble solid-type material, rate of DPPH (2, 2-diphenyl-1-picrylhydrazyl) free radical scavenging, and reducing power, through different experimental conditions. Multiple linear regression analysis indicated that the suitable process conditions were-40℃ freezing temperature, 4.5m/s fan speed, and3.6cm bed height, for quick-freezing blueberries using a liquid nitrogen-type fluidized bed. Based on the regression equation of dimensionality reduction, the influence of the fluidization process parameters on the six indexes of blueberry was analyzed. This study might serve as a theoretical basis for further optimization of the fluidized bed quick-freezing process of blueberries.