Impact of thawing methods on physico‐chemical properties and microstructural characteristics of concentrated milk

Abstract

This study investigated the effects of different thawing methods on the physico-chemical properties and microstructural characteristics of pasteurized milk and concentrated milk. Four thawing methods including air thawing, flowing water thawing, microwave thawing, and ultrasonic thawing (UT) were individually used. The results showed that particle size and fat globules size of milk increased after thawing, but UT could improve these conditions. For the pasteurized milk, thawing process caused ethanol stability and heat stability degradation. Thawing decreased thermal stability of concentrated milk; however, no change was observed in ethanol stability. Secondary structures of proteins in both samples were also destroyed after thawing. The thawing method did not change pH values, but it would cause a small change in titratable acidity. Overall, the UT could maintain physico-chemical properties of pasteurized milk and concentrated milk better compared with other thawing treatments. Practical applications Thawing is an essential step before processing or eating frozen food and can greatly affect the final quality of the frozen food. To our knowledge, no previous study has optimized the method of thawing milk and compared the effects of different thawing methods on milk. So, it is important to study the effect of the different thawing method on the quality of concentrated milk. Ultrasonic thawing can increase the physico-chemical properties of milk.