Dry microwave and hot water blanching of underutilized star fruit (Averrhoa carambola): A comparative assessment of quality attributes and sensory evaluation using chemometric approach

Star fruit is an underutilized fruit with a shorter shelf life and astringent taste due to its high amount of ascorbic acid content. In this study, microwave blanching (MWB) as an alternative heat treatment was compared with conventional hot-water blanching (CHWB) to increase the shelf life and retain the nutrition. Different temperature-time combinations for CHWB (80 °C and 300-900 s) and MWB (100-600 W and 30-120 s) were assessed for blanching adequacy and adequate blanched samples were compared on quality and sensory parameters. The effect of treatment conditions on pH was non-significant (p>0.05), while total soluble solids increased for MWB samples at higher power levels from 5° to 5.8° Brix. Browning index increased significantly from 0.097±0.003 to 0.214±0.012 for CHWB (80 °C-900 s) and 0.193±0.009 for MWB (600 W-120 s). In blanched samples, B7 (600 W-60 s) showed 27.8% better retention of total ascorbic acid and 26.99% of total carotenoid content than B4 (80 °C-900 s). Quantitative descriptive analysis (QDA) showed better resemblance of MWB samples with the control sample than CHWB samples. MWB samples at higher power levels are microbiologically safe even after 15 days of storage at refrigerated conditions. MWB may be used as a more effective technique for retaining nutritional content, sensory qualities, and microbiological safety, hence enhancing the healthiness and quality of fruit-based products.