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.
