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Mathematical modeling and effect of blanching pretreatment on the drying kinetics of Chinese yam (Dioscorea opposita)

Fang Sheng (Zhejiang Gongshang University, School of Food Science and Biotechnology Engineering, Hangzhou, China)
Wang Li-Ping (Zhejiang Gongshang University, School of Food Science and Biotechnology Engineering, Hangzhou, China)
Wu Ting (Zhejiang Gongshang University, School of Food Science and Biotechnology Engineering, Hangzhou, China)

The influences of blanching pretreatment on the drying kinetics of Chinese yam (Dioscorea opposita) slices were investigated. Drying experiments were carried out at 60, 70, 80 and 90°C. Six thin layer models were evaluated and the determination of coefficient (R2), chi-square (χ2), root means square error (RMSE) were used to analysis the model performance for both raw and blanched samples. The Wang and Singh model gave best results with R2 of 0.9987 and RMSE of 0.0136 for raw yam slices, and R2 of 0.9989 and RMSE of 0.0119 for blanched samples. The effective moisture diffusivity coefficient Deff varied in the range of 0.7295×10-9 to 2.4087×10-9m2 s-1 for raw slices, and 1.3748×10-9 to 3.8524×10-9m2 s-1 for the blanche dones. The activation energy of yam slices drying were 41.149 and 33.499 kJ mol-1 for raw and blanched yam slices, respectively. Results show that blanching pretreatment can reduce the total drying time and improve the effective moisture diffusivity compared with the raw samples.

Keywords: Chinese yam, hot air drying, kinetics, modeling, blanching