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

Abstract

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)

ABSTRAK

Peningkatan dalam pengeluaran betik memerlukan strategi baru untuk melanjutkan jangka hayat penyimpanan buah. Salutan yang boleh dimakan bertindak sebagai sekatan fizikal apabila digunakan pada permukaan buah yang mana ianya berkesan dalam mengubah keadaan dalaman buah betik dan melambatkan proses pematangan. Dalam kajian ini, dua jenis lapisan yang berbeza telah dibangunkan dari lendir kaktus dan kesan mereka terhadap kualiti dan jangka hayat buah betik telah dikaji. Kedua lapisan eksperimen: Ekstrak Lendir Tulen (ELT) dan ekstrak lendir bercampur dengan 5 mL gliserol (ELTG) telah bertindak sebagai agen plastik. Parameter yang diukur ialah penurunan berat buah, kandungan asid askorbik, pH, kekerasan, jumlah pepejal terlarut dan kualiti mikrob buah betik. Buah betik disimpan selama enam minggu pada suhu purata 27 ± 2 °C dan kelembapan relatif 55-60% di bawah Sistem Penyejuk Penyejatan (SPP). Sebelum penyimpanan, permukaan buah betik telah disterilkan dengan menggunakan 100 mg/L natrium hipoklorit dan disusun secara rawak kepada tiga jenis rawatan; kawalan (tidak dirawat) dan dua rawatan salutan. Selepas enam minggu penyimpanan, kepekatan yis dan kulat didapati menurun bagi kawalan dari 8.89 log CFU/g kepada 3.87 log CFU/g (ELTG) dan 4.78 log CFU/g (ELT), secara berurutan, juga kepekatan bakteria aerobik psikrotrofik menurun daripada 11.22 log CFU/g (kawalan) kepada 4.21 log CFU/g (ELTG) dan 6.02 log CFU/g (ELT), manakala kepekatan bakteria aerobik mesofilik turut menurun daripada 9.78 log CFU/g (kawalan) kepada 4.98 log CFU/g (ELTG ) dan 6.32 log CFU/g (ELT). Parameter-parameter di atas yang berkaitan dengan pengurangan kualiti lepas tuai bagaimanapun telah dikawal dengan ketara dalam betik yang bersalut. Keputusan keseluruhan menunjukkan bahawa lendir kaktus adalah berkesan dalam melanjutkan jangka hayat buah betik berbanding dengan kawalan. ELTG didapati lebih berkesan daripada ELT.

Kata kunci: Carica papaya, salutan yang boleh dimakan, gliserol, kaktus Opuntia, Sistem Penyejuk Penyejatan (SPP)