Effect of starch osmo-coating on carotenoids, colour and microstructure of dehydrated pumpkin slices.

Carotenoids in pumpkins are extremely unstable during industrial drying, to avoid the carotenoid degradation, starch omso-coating was subjected to the pretreatment process for dehydrated pumpkin slices. The results showed that starch omso-coating reduced the dehydration rate of pumpkin slices. When coated with corn starch, the retention rates of lutein, α-carotene and β-carotene in dehydrated pumpkin slices significantly increased by 11.3, 9.0 and 7.7%, respectively, and the provitamin A activity increased by 9.5%. 1% (w/v) modified corn omso-coating gave highest retention rate of total carotenoids (95.5%), while provitamin A activity reached 4148 µg RAE/100 g. In addition, the colour parameters △E and a* values reduced, but L*, b* and H values increased with coated samples. Pearson correlation analysis showed that lutein, α-carotene and β-carotene were significantly positive correlated with L*, and exhibited negative correlations with △E. The SEM indicated starch granules was attached to tissue gap and caused the film formation of oxygen barrier. It could be concluded that modified corn coating effectively improved the quality of final product.