Magnetic nanometer combined with microwave: Novel rapid thawing promotes phenolics release in frozen-storage lychee

Magnetic nanometer combined with microwave thawing (MN-MT) could become a novel solution to challenges uneven and overheating of microwave thawing (MT), while retaining high thawing efficiency, compared to conventional water immersion thawing (WT). In this study, MN-MT was applied to thaw fruit (lychee as an example) for the first time, and was evaluated by comparison with WT, MT and water immersion combined with microwave thawing (WI-MT). Results showed that MN-MT could significantly shorten the thawing time of frozen lychee by 80.67%, 25.86% and 18.83% compared to WT, MT and WI-MT, respectively. Compared to WT, MN-MT was the only thawing treatment which significantly enhanced the release of quercetin-3-O-rutinose-7-O-alpha-L- rhamnoside, according to HPLC-DAD. Meanwhile, thermal-sensitive procyanidin B2, phenylpropionic acid and protocatechuic acid were found to be protected from degradations only by MN-MT based on UPLC-ESI-QTOF-MS/MS results. In summary, MN-MT is a potential novel treatment for rapid thawing and quality mainte-nance of frozen fruits.

Automated summary

Magnetic nanometer combined with microwave thawing (MN-MT) can be a novel solution for uneven and overheating challenges in microwave thawing (MT), while maintaining high thawing efficiency compared to conventional water immersion thawing (WT). This study applied MN-MT to thaw lychee fruit for the first time and evaluated it compared to WT, MT, and water immersion combined with microwave thawing (WI-MT). The results showed that MN-MT significantly reduced the thawing time of frozen lychee by 80.67%, 25.86%, and 18.83% compared to WT, MT, and WI-MT, respectively. MN-MT also enhanced the release of quercetin-3-O-rutinose-7-O-alpha-L- rhamnoside and protected thermal-sensitive compounds from degradation.