Abstract:

The effects of different thawing methods, microwave, water bath, ultrasonic and natural thawing, on quality
characteristics of quick-frozen strawberries were investigated by measuring the required thawing time as well as physical
properties and nutritional quality of thawed strawberries. The results showed that the time necessary to thaw frozen
strawberries by different methods decreased in the following sequence: microwave, ultrasonic, water bath, and natural
thawing, with an extremely significant difference among these four methods. Microwave thawing was the best for maintaining
the color and harness of strawberries and minimizing the drip loss, and ultrasonic ranked second. Furthermore, microwave-thawed
samples exhibited a significantly higher total acid content and extremely significantly higher contents of reducing sugar and vitamin
C (VC) than those thawed by three other methods. Ultrasonic resulted in a higher content of anthocyanins in thawed strawberries
than other methods, suggesting that these compounds are destroyed to the least extent during the thawing process. Taken together
these results demonstrate that microwave is superior to the other thawing methods.

Key words: microwave thawing, water bath thawing, ultrasonic thawing, air thawing, quick-frozen strawberry fruits, quality characteristics