The effects of immersion freezing (IF) followed by microwave thawing on the quality of frozen litchis
were investigated after frozen storage for various time periods and compared with traditional air-blast
freezing (AF). The freezing rate of IF samples was 10 times higher than that of AF samples. The
average size of ice crystals in IF and AF samples was determined as: AF > 200
m
m > IF. Consequently,
there was good integrity of the fruit microstructure, hardly any drip loss and high retention (80%) of
texture, quality and nutrient content in IF samples. Moreover, the IF samples retained their red color,
with texture and taste that were difficult to distinguish from fresh litchis after being thawed and placed
at room temperature for 3 h. In contrast, the AF litchis showed significant degradation in their quality,
including loss of firmness, 4% drip loss and rapid browning. Compared with the AF method, the IF
technology improved the quality of frozen litchis overall and greatly extended their shelf-life to at least 6
months. Therefore, IF should be considered as a promising novel technology for long-term storage of
litchis.