Incorporation of papaya (Carica papaya L.) leaf extract into cornhusk for glutinous rice snack packaging application

The present work was performed to evaluate the potency of papaya leaf extract (PLE) to improve the characteristics of cornhusk as a packaging material for glutinous rice snack (GRS). Total phenolic, tannin, and saponin contents of PLE were 7.41 ± 0.65 mgTAE/mL, 1.80 ± 0.70 mgTAE/mL, and 11.78 ± 0.36 mgDE/mL, respectively. The presence of bioactive compounds on the surface of GRS was confirmed by Fourier transform infrared spectroscopy analysis. Characteristic bands for saponin were caused by the stretching vibration of C=O (at 1744 cm-1) as well as C‒O and C‒C vibrations (at 1051 cm-1). Tannin was identified as C‒O asymmetric stretch vibration at 1051 cm-1 and C‒H out of plane vibration at 926 and 866-867 cm-1. The antioxidant activity of PLE was found to be 49.53 ± 2.67%. The reductions of total plate counts (TPC), yeast and mould counts (YMC), and Aspergillus flavus-A. parasiticus counts on PLE-incorporated cornhusks after 24 h were in the range of 0.2 - 1.2 log CFU/cm2, and retained the loads below 2 log CFU/cm2 during 14-d storage. PLE decreased the water vapour transmission rate of the cornhusk due to the particles of the extract adhering to the cornhusk surface, as supported by the result of the scanning electron microscopy of PLE-incorporated cornhusk. The incorporation of PLE also increased elongation without reducing the tensile strength of the cornhusk significantly. There were reductions of TPC, YMC, and Aspergillus flavus-A. parasiticus counts of GRS ranging from 0.4 - 2.3 log CFU/g using PLE-incorporated cornhusks during storage. GRS rancidity was minimised by PLE-incorporated cornhusks. Owing to its bioactive compound, PLE could be incorporated into the cornhusk to improve packaging characteristics and controls microbial contamination of GRS while retarding the rancidity.