Research on tomato peeling using flame-catalytic infrared radiation

To improve tomato peeling rate and ensure pulp quality, a flame-catalytic infrared peeling (FIP) method was developed in this study. The peeling parameters, peelability, mechanism (polysaccharides, mechanical property, and microstructure) and pulp quality (firmness, lycopene, and polysaccharides) were investigated. Results showed that FIP under 10 s flame heating and 4 min infrared heating at 350 °C yielded the highest peelability (98%), firmness (6.04 g/mm2), and lycopene (53.73 mg/kg). Compared with hot water peeling (HWP) and lye peeling (LP), FIP had the least degradation of cellulose (92.32%), hemicellulose (61.75%), and pectin (76.47%) in peel and the least damage to their structures and mechanical properties with the reductions of 19.50% and 16.69% (tensile and puncture forces). The only cell collapse of the peel was found in FIP by scanning electron microscopy (SEM), showing a different peeling mechanism from the HWP and LP. In addition, FIP protected pulp quality to the greatest extent, which had the highest retention of cellulose (91.67%), hemicellulose (94.08%), pectin (98.66%), and firmness (6.04 g/mm2), significantly increased the lycopene content and did not change their structures. It proves that FIP has a promising potential to replace the existing peeling technology and can be widely applied in the fruit peeling.