Optimization and Quality Comparison of Low Temperature Vacuum Fried Pueraria thomsonii Crisp Chips

To fully utilize the Pueraria thomsonii, low temperature vacuum frying technology was applied to prepare crisp chips from Pueraria thomsonii. On the basis of single factor tests, the optimal process was determined by orthogonal experimental design. The optimum conditions were listed as follows: Thickness of chips 2 mm, frying temperature 105 ℃, frying time 35 min, and blanching time 3 min. The crispness value and fat content of Pueraria thomsonii crisp chips under the optimum conditions was 989.35 g and 22.95%, respectively. In addition, the quality of Pueraria thomsonii crisp chips from different processes were compared. The Pueraria thomsonii crisp chips produced under the low temperature vacuum fried process and treated by bleaching and/or freezing showed lower fat content and higher crispness values. The crisp chips produced under the conventional frying process treated by bleaching and freezing technology presented the lowest water content (1.71%) and crispness value (597.54 g), but the fat content was as high as 62.24%. The fat content of Pueraria thomsonii crisp chips produced by conventional frying without bleaching pretreatment was significantly higher than that after low-temperature vacuum frying process (P<0.05), but there was no significant difference in crispness value (P>0.05). After frying, the main aroma substances of Pueraria thomsonii crisp chips were nitroxide, sulfide and organic sulfide. However, there were obvious differences in the aroma for the different frying process. After frying, the honeycomb structure on the chips disappeared. There were a few holes on the surface of Pueraria thomsonii crisp chips produced by low temperature vacuum frying process. However, there was gel layer on the Pueraria thomsonii crisp chips without freezing treatments.