| Currently, there is a worldwide demand for antioxidant rich foods in diet, especially ready to eat foods, i.e. cereals and snacks. In recent years, the research has got momentum to valorize the underutilized crops, i.e. millet, sorghum and industrial food by-products, i.e. fruit pomace to incorporate into main stream of human diet due to their enrichment in nutritional as well as bioactive compounds like phenolic and flavonoid antioxidants. However, most of the phenolic compounds in plant are present in the bound form with the carbohydrates, lignin, pectin and proteins which reduces their ability to function as good antioxidants. Therefore, in the first part of study, selected non-thermal technologies were compared to liberate the bound phenolic acids in the sorghum flour (SF) and apple pomace (AP) in order to enhance their total content in raw materials prior to secondary processing. Starting with the natural fermentation followed by the batch ultrasonication, SF and AP showed a significant (p<0.05) improvement in the total phenolic content (TPC) and antioxidant activity (AA). The increased TPC and AA were observed as 21.8%, 33.9% and 40.3%, 93% for SF and AP, respectively. Drying as the final unit operation of this process, the microwave drying of ultrasonicated AP showed higher TPC and AA when compared to the oven drying.;After getting improved TPC and AA using the batch ultrasonication process, SF and AP were treated with the continuous ultrasonicator in order to investigate the release of phenolics at the pilot scale. The investigation revealed that the continuous ultrasonication (UC) further improved 15.8% TPC, 6.3% AA in SF and 3.8% TPC, 1.4% AA in AP with compared to the batch process. Although the ultrasonication time and intensity observed in the continuous process were less, similar fermentation time (12 h SF, 24 h AP) and sample concentration (10%w/v SF, 5%w/v AP) were found at the optimum conditions for both the ultrasonication process.;Pulsed electric field (PEF) as a second non-thermal technology was employed to investigate its effect on the TPC, AA of the SF and AP. The optimized conditions of fermentation time of SF and AP from UC were taken into consideration for further research. The mild intensity PEF improved the TPC and AA in both the materials, significantly at higher sample concentration (45%w/v SF, 12.5%w/v AP), however the relative increase was less when compared to the continuous ultrasonication process at its optimum conditions. PEF intensity, treatment time and sample concentration were observed as the important parameters to impact the phenolic release in SF and AP. The TPC, AA for SF and AP were observed 11.5%, 5.9% and 5.7%, 5%, respectively less when compared to the continuous ultrasonication.;As an alternative to ultrasonication, hydrodynamic cavitation (HC), the third non-thermal technology was compared with the previous two for TPC and AA of SF and AP. As investigation revealed, HC increased the TPC, AA in SF and AP by 39.5%, 38.6% and 42%, 97%, respectively when compared to the controls. Both the materials had almost equivalent TPC and higher AA than that found for the continuous ultrasonication. Though the optimum sample concentration of SF for HC was same as UC, AP sample concentration (8.75%w/v) for HC was found higher than that reported for UC (5%w/v). Therefore, among the three, HC was selected as the best non-thermal process in order to release the phenolic compounds in SF and AP.;After selecting the best non-thermal process that increased the phenolics in SF and AP, the second part of study was conducted to retain the maximum phenolics along with the improved textural and functional properties in SF and AP extrudates during extrusion process. Corn flour (CF) and hydrodynamic cavitated sorghum flour, apple pomace blend was extruded for three levels of apple pomace ratio APR (10%, 20%, 30%), feed moisture FM (25%, 30%, 35%wb), extrusion temperature T (80, 110, 140ºC) and screw speed SS (100, 150, 200 rpm). At the optimum conditions of 30% APR, 25%wb FM, 132ºC T and 108 rpm SS, TPC and AA observed in the extrudates were 62.5% and 67.3%, respectively higher than that of the control extrudates (without HC). The expansion ratio, brittleness, crispness, water solubility index (WSI), IVSD, TDF and soluble dietary fiber (SDF) increased whereas hardness and water absorption index (WAI) significantly (p<0.05) decreased in the extrudates when compared to that of the control extrudates.;In another modified extrusion process, carbon dioxide was injected with the same blend of CF, SF and AP. At the optimum conditions of 30% APR, 25%wb FM, 97ºC T and 100 rpm SS, TPC and AA of the extrudates produced with CO2, exhibited 12% and 7% more TPC and AA, respectively with compared to that of the control extrudates (without CO2). It was observed that the extrudates produced in latter extrusion process possessed improved TPC, AA, hardness, brittleness, crispness, WAI and WSI, however due to CO 2 injection, ER, IVSD and TDF slightly decreased with compared to that of the extrudates developed in the former extrusion process.;The whole study concluded that the natural fermentation followed by the hydrodynamic cavitation and CO2 assisted extrusion produced the corn flour, sorghum flour and apple pomace based extrudates with improved TPC, AA, textural, nutritional and functional properties. |
