Viscoelastic properties of tomato peels produced from catalytic infrared and lye peeling methods

Abstract

This study investigated the effect of infrared and lye peeling methods on viscoelastic properties of tomato peels of cultivars - Hz 5508, Seminis DRI 319, and Seminis HP 849 using a dynamic mechanical analyzer (DMA) under temperature ramp mode. Peels were produced from infrared (IR) peeling conducted at three tomato surface temperatures of 109, 112 and 115°C, and lye peeling conducted at 95°C using a 10% NaOH solution. Fresh tomato peels were used as a control. It was found that dynamic moduli of all the peel samples decreased initially and then increased with increase in temperature, displaying a parabolic curve. Storage moduli of peel samples were higher than their respective loss moduli, indicating dominant elastic properties over viscous properties in tomato peels. Compared with the control, IR and lye treated peels had higher and lower storage moduli, respectively. Raw peels had significantly (α=0.05) higher transition temperatures (89.4°C) than the IR (72.2°C) and lye (46.2°C) treated peels. Storage moduli at respective transition temperatures were significantly (α=0.05) higher for IR treated peels (9.8MPa) than those of raw (4.4MPa) and lye treated peels (1.0MPa). The storage moduli of Seminis DRI 319 and Hz 5508 at respective transition temperatures were not significantly different (α=0.05). However, they were significantly (α=0.05) lower than those of Seminis HP 849. The difference in storage moduli and transition temperatures of tomato peels obtained from IR and lye peeling processes indicated a fundamental difference in their peeling mechanism.