Development of a moisture absorber for packaging of fresh mushrooms (Agaricus bisporous)

Polymeric films used in fruit and vegetable packaging have lower water vapour transmission rates relative to the transpiration rates of fresh products. Therefore, high humidity conditions prevail in the packages, causing moisture condensation, microbial growth and decay of the product. A possible solution to control humidity is to use moisture absorbers. However, existing moisture absorbers either have low absorption capacity and/or absorb moisture quickly, making them unsuitable for mushrooms. This study was undertaken in order to develop a moisture absorber with high moisture holding capacity and slower rate of moisture absorption for packaging of fresh mushrooms. Fast absorbing moisture absorbers such as CaCl2, KCl and sorbitol were mixed with a slow absorbing desiccant such as bentonite in different proportions. The best combination was found to be with bentonite, sorbitol and CaCl2 in proportions of 0.55, 0.25 and 0.2 g g−1 desiccant, respectively. It showed a moisture holding capacity of 0.9 g water g−1 mixed desiccant that remained in powder form during 120 h of storage at 10 °C. Further study was conducted to evaluate the kinetics of moisture absorption of this mixed desiccant at 4, 10 and 16 °C and at different humidity levels of 76, 86 and 96%. The change in moisture content of the mixed desiccant with respect to storage time was fitted to a Weibull distribution model. The moisture holding capacity was found to be dependent on the relative humidity; it increased from 0.51 to 0.94 g water g−1 desiccant when relative humidity was increased from 76 to 96%. The kinetic parameter of the Weibull distribution function was found to be dependent on both temperature and relative humidity. Overall appearance of mushrooms improved when 5 g of mixed desiccant was packed in 250 g of mushroom punnet compared to those packed without desiccant.