Ohmic Heating Assisted Lye Peeling of Pears

Currently, high concentrations (15% to 18%) of lye (sodium hydroxide) are used in peeling pears, constituting a wastewater handling and disposal problem for fruit processors. In this study, the effect of ohmic heating on lye peeling of pears was investigated. Pears were peeled using 0.5%, 1%, 2%, and 3% NaOH under different electric field strengths at two run times and their peeled yields were compared to that obtained at 2% and 18% NaOH with conventional heating. Results revealed that ohmic heating results in greater than 95% peeled yields and the best peel quality at much lower concentrations of lye (2% NaOH at 532 V/m and 3% NaOH at 426 and 479 V/m) than those obtained under conventional heating conditions. Treatment times of 30 and 60 s showed no significant differences. Within the studied range, the effects of increasing field strength yielded no significant additional benefits. These results confirm that the concentration of lye can be significantly lowered in the presence of ohmic heating to achieve high peeled yields and quality.

Our work shows that lye concentrations can be greatly reduced while peeling pears, resulting in significant savings in use of caustic chemicals, reduced costs for effluent treatment and waste disposal.