Optimization of osmotic dehydration of Terung Asam (Solanum lasiocarpum Dunal)

This study was designed to determine the effect of osmotic dehydration (OD) process temperature (35-55 °C), sucrose concentration (40-60% w/w) and immersion time (90-210 min) on the water loss (WL), solid gain (SG), DPPH radical scavenging activity, ferric reducing antioxidant power (FRAP) and sensory quality of the dehydrated Terung Asam slices. Response Surface Methodology with Central Composite Design was applied to investigate the influence of these variables on the aforementioned responses. The increase in the levels of these processing parameters increased the WL and SG. The antioxidant activities also increased with sugar concentration, but reduced with immersion time and temperature elevation. About 36-80% of IC₅₀ and 47-72% of FRAP were depleted after osmotic process. The loss of antioxidants was predominantly due to leaching during osmotic treatment rather than hot air drying. Despite the losses of these compounds, osmotic pretreatment was able to improve the sensory quality of the product. The optimum OD process condition was predicted as process temperature 38.1 °C, sucrose concentration 55.6% and osmotic duration 126.3 min.