Influence of freezing rate variation on the microstructure and physicochemical properties of food emulsions

The freezing rate used in industrial applications may vary for a number of reasons, such as changes in food mass, food composition, and freezing equipment operation. In this study, we evaluated the influence of freezing rates on the microstructure, stability and physicochemical properties of model emulsion-based sauces. Slow freezing (−0.015 °C/min) resulted in a larger mean particle size than fast freezing (−0.11 °C/min), which was attributed to increased fat droplet flocculation and coalescence. The influence of various additives (salt, sugar, gums) on the properties of the sauces was also investigated. The addition of 200 mmol/L NaCl promoted droplet flocculation and phase separation whereas 150 mmol/L sucrose inhibited droplet flocculation and phase separation, and inhibited ice crystal growth. The addition of 0.2% xanthan gum promoted flocculation, but inhibited phase separation and ice crystal growth. Our results are interpreted in terms of the influence of the additives on the phase behavior of water, and the colloidal interactions between the fat droplets. This study provides valuable information about the major factors, i.e., salt and sugar, and influence on the stability of emulsion-based products to freeze-thaw abuses, which has important implications for the development of high quality frozen meals.