Evaluation and Optimization of Steam and Lye Peeling Processes of Sweet Potato (Ipomea batatas) using Response Surface Methodology (RSM)

Sweet potato of uniform sizes and shape were subjected to steam peeling (temperature 80-100 degrees C and peeling time 5-15 min) and lye peeling (sodium hydroxide concentration 8-12%, temperature 80-100 degrees C and peeling time 3-5 min). Response surface methodology was used to analyze and optimize the process parameters in each case. For steam peeling, the peel loss and unpeeled surface area were 6.85 and 28.16%, respectively, while optimum peeling conditions where temperature and peeling time of 100 degrees C and 5 min, respectively, for minimum peel loss and unpeeled surface area. For lye peeling, however, the peel loss and unpeeled surface area were 13.19 and 13.35%, respectively, and optimum peeling conditions were lye concentration, temperature and peeling time of 8.89%, 100 degrees C and 4.75 min, respectively, for minimum peel loss and unpeeled surface area. The models developed in each case (R-squared of 0.9225 and 0.8428; 0.5929 and 0.8346) were adequate in producing responses as a function of the independent variables. From the optimized values and results obtained, lye peeling was more suitable for sweet potato.