Effects of Hot Air and Freeze Drying on the Quality of Five Fresh Sweet Corns Kernels

Objective: To investigate the effects of hot air drying (HAD) and vacuum freeze drying (VFD) on the quality of fresh sweet corn, in order to provide reference for the appreciation and utilization of fresh sweet corn after harvest. Methods: The effects of HAD and VFD on water content, soluble protein, hardness, frangibility, color difference, rehydration ratio and microstructure of five fresh sweet corn varieties (Jingheitian, Baimeiren, Jinyin208, Meiguo No.1 and Hesu No.1) were studied. Results: The moisture content of VFD sweet corn dry product was lower than HAD sample, which was easy to preserve; the soluble protein was higher than HAD sample, the loss of nutrients was less; the hardness was lower than HAD, the taste was better, the frangibility was lower than HAD, the tissue was soft, the taste was delicate; the color was better than HAD sample, the visual effect was better; the rehydration was much better than HAD sample, the dry product had stronger water absorption; scanning under the electron microscope, the cross-section of VFD sweet corn dry products was a porous honeycomb network structure with uniform distribution of micropores. The cross-section structure of HAD sample was closely stacked and the cell wall collapses seriously. The hardness, brittleness and color difference of VFD dried sweet corn were close to that of fresh sweet corn, and there were more internal voids and better quality. Conclusion: Different varieties of fresh sweet corn were different after eating VFD. The order of sweet corn varieties suitable for VFD was Jingheitian, Hesu No.1, Baimeiren, Meiguo No.1 and Jinyin 208. In general, Jingheitian and Hesu No. 1 were more suitable for VFD, while Meiguo No. 1 and Jinyin 208 were more suitable for HAD.