Quasi-static mechanical properties of tomato peels produced from catalytic infrared and lye peeling

Abstract

This study investigated the quasi-static mechanical properties of tomato peels of three cultivars - Hz 5608, Seminis DRI 319 and Seminis HP 849. The peels were produced from infrared (IR) heating with three targeted tomato surface temperatures of 109, 112 and 115 °C at two loading rates which reflected the different heating rates. Peels from conventional lye peeling method using a solution of 10% NaOH at 95 °C were used for comparison. Fresh tomato peels were used as control. A texture analyzer was used to determine the tensile strength to failure, puncture resistance strength, and adhesive strength of peels. It was found that mechanical strengths of tomato peels obtained from both IR and lye peeling processes were significantly (α = 0.05) lower than those of the control. However, the mechanical strengths of tomato peels under IR treatment at the temperatures of 109 and 112 °C were significantly (α = 0.05) higher than those of the peels obtained from lye treatment. The mechanical strength of the peels produced from IR treatment at 115 °C was similar to those produced from lye treatment. The reductions in tensile, puncture and adhesive strengths of peels were up to 88, 87.3 and 74.3%, respectively, for IR heated tomatoes, whereas these were 95.1, 99.3 and 91.3%, respectively, for lye treated tomatoes compared to control. The peels obtained from IR peeling had more integrity than those obtained from lye peeling. Increasing the loading rates of tomatoes during IR heating corresponding to lowered heating rate significantly (α = 0.05) decreased the mechanical strengths of peels due to increased residence time for reaching the targeted temperatures. Tomato cultivars had a significant (α = 0.05) effect on the adhesive strength of peel but not on tensile and puncture resilience strengths. These results provide important information about the changes of mechanical properties of tomato peel under different processes.