Effect of Selected Pretreatments on Impregnation of Curcuminoids and Their Influence on Physico-chemical Properties of Raw Banana Slices

The effect of pretreatments, namely, blanching, ultrasound, vacuum and their combinations on curcuminoid impregnation in raw banana slices, was studied in conjunction with treatments in pure water as well as in 10 % NaCl solution. The treatments such as ultrasound, vacuum and combination of vacuum and blanching with ultrasound resulted in higher curcuminoid infusion compared to control for both pure water and 10 % NaCl osmotic treatments. The blanching treatment resulted in lower infusion of curcuminoids as compared to that of control due to the gelatinisation of starch present in banana. Further, the increase in surrounding solution concentration from pure water to 10 % NaCl resulted in enhanced curcuminoid infusion (e.g. from 85 to 95 mg/100 g for combined vacuum and sonication treatment). However, the direction of the mass transfer of water as well as solid was reversed. The samples subjected to combined vacuum and sonication treatment resulted in lowest compressive force, highest infusion of curcuminoids and highest total colour difference compared to other treatments. Besides, the dehydration of such product also resulted in the highest retention of curcuminoids compared to the individual treatments. The present study concluded that osmotic treatment can be a feasible technology for the infusion of functional ingredients into foods without altering its matrix. The extent of infusion can be significantly enhanced by the application of combined treatment such as vacuum and ultrasound.