Use of pretreatments to enhance the quality attributes and drying characteristics of dehydrated tender jackfruit

Abstract

Tender jackfruit is a perishable tropical food crop with high nutrition. If preserved appropriately, it could be consumed off-season or exported to foreign markets. Convective drying is a simple and economical food preservation technique, which, however, is associated with quality defects such as browning, shrinkage etc. Therefore, this study investigated the possibility of using osmotic dehydration (OD) at 400C , followed by two different treatments using, Sodium metabisulfite (SMB OD) and Citric acid (CA-OD), as pretreatments to improve drying characteristics and quality attributes of dehydrated tender jackfruit. First, convective drying kinetics (at 60℃) of pretreated samples and untreated control (C) were modelled using five thin layer drying kinetic equations (Newton, Logarithmic, Henderson and Pabis, Modified Page, and Page) to predict the time required to reach a standard moisture content of 6% (wb). Page model best fitted the kinetic data of all samples. OD removed nearly 10% moisture from tender jackfruit prior to convective drying, resulting in a significantly (p<0.05) lower drying time (9.08 h) in OD, SMB-OD and CA-OD samples compared to the drying time of control (9.57 h). All treatments with OD reduced sample deformation during drying and resulted in a significantly low (p<0.05) shrinkage (60.33 - 74.89%) compared to shrinkage of control (86.61%). Browning index (BI) measurements showed a marginal yet statistically significant (p<0.05) reduction in enzymatic browning with OD alone (BI=0.66), compared to control (BI=0.80). Greater reductions in browning were observed with SMB-OD (BI=0.07) and CA-OD (BI=0.09). All pretreatments led to insignificant (p>0.05) changes in rehydration ratios. This study demonstrates that OD could reduce convective drying times and shrinkage while coupling it with chemical treatments could preserve the colour of dried tender jackfruit. The developed Page model could be used to predict the drying time of tender jackfruit during industrial processing.