Effects of Opuntia Cactus Mucilage Extract and Storage under Evaporative Coolant System on the Shelf Life of Carica papaya Fruits

ABSTRACT

The increase in papaya production requires new strategies to extend the storage life of the fruit. Edible coatings act as physical barriers when applied on the surface of fruits and effectively change their internal atmosphere and delay the ripening process. In the present study, two different coatings were developed from the mucilage of Opuntia cactus and their effects were investigated on the quality and storability of papaya fruits. The two experimental coatings were pure mucilage extracts (ME) and mucilage extract mixed with 5 mL glycerol (MEG) which served as plasticizer. The parameters measured were weight loss, ascorbic acid content, pH, firmness, total soluble solid and the microbial qualities of papaya fruits. Papaya fruits were stored for six weeks at an average temperature of 27 ± 2 °C and relative humidity of 55-60% under an Evaporative Coolant System (ECS). Prior to storage, the papaya fruits were surface sterilized using 100 mg/L sodium hypochlorite and randomly arranged into three treatments, the control (untreated) and the two coating treatments. After six week of storage the concentration of yeast and mold was found to decrease in the control from 8.89 log CFU/g to 3.87 log CFU/g (MEG) and 4.78 log CFU/g (ME); also the concentration of aerobic psychrotrophic bacteria decreased from 11.22 log CFU/g in the control to 4.21 log CFU/g (MEG) and 6.02 log CFU/g (ME) mucilage treated fruits while the concentration of aerobic mesophilic bacteria was decreased from 9.78 log CFU/g in the control to 4.98 log CFU/g (MEG) and 6.32 log CFU/g (ME) mucilage treated fruits. The above parameters which are related to post-harvest quality loss were however significantly controlled in the coated papaya. The overall result showed that cactus mucilage was effective in extending the shelf-life of papaya fruits when compared to the control. MEG was more effective than ME.

Keywords: Carica papaya, Edible coating, Glycerol, Opuntia cactus, Evaporative Coolant System (ECS)