Effects of Liquid Nitrogen Freezing Temperature, Sample Volume and Depth on the Temperature Fluctuation, Microstructure, and Qualities of Large Yellow Croaker During Storage

Abstract

The microstructure and physicochemical properties of large yellow croaker (Larimichthys crocea) frozen by air freezing (AF, -20 °C) and liquid nitrogen spray freezing (LNSF, -20, -60, and -100 °C) during storage were evaluated. The effects of sample volume and depth on temperature fluctuations and the change in ice crystal size were explored. LNSF at -100 °C resulted in uniform ice crystals with a significantly lower cross-sectional area (186.95 μm2) compared to AF (7844.22 μm2), reducing thawing loss from 11.61% to 7.04%. Temperature fluctuation range and final cross-sectional area decreased from 0.944 to 0.645 °C, and 456.75 to 286.90 μm2, respectively, with increaseing depth from 2 to 20 mm. The significantly lowest thiobarbituric acid reactive substances (0.93 mg MDA/kg), total volatile basic nitrogen (16.68 mg/100g), and the highest α-helices content (29.44%) for samples frozen at -100 °C suggested that rapid freezing inhibited lipid oxidation and protein denaturation, and extended shelf life.

Keywords: Liquid nitrogen spray freezing, Large yellow croaker, Storage, Temperature fluctuation, Microstructure, Depth