Application of hydrodynamic cavitation to improve antioxidant activity in sorghum flour and apple pomace

- Successful use of hydrodynamic cavitation to release the bound phenolics in sorghum flour and apple pomace.
- Potential use of fermentation followed by cavitation.
- Antioxidant activity increased by 37% and 97% in sorghum flour and apple pomace, respectively at optimum process condition.
- Hydrodynamic cavitation could be a better alternative to the ultrasonic cavitation in terms of scale up capability.

To overcome the energy inefficiency and scale-up issues of ultrasonication, hydrodynamic cavitation was studied to release the bound phenolics in sorghum flour (SF) and apple pomace (AP) to enhance their antioxidant activity. In this study, SF and AP, naturally fermented at optimized conditions, were hydrodynamic cavitated at different flour to water (FWR) of 100, 275, 450 g/L and 50, 87.5, 125 g/L, respectively. In addition, three types of cavitators with 2, 3 and 4 rows of holes in rotor were used to cavitate SF and AP for the cavitation temperatures as 30, 35, 40 °C and 40, 45, 50 °C, respectively. For SF and AP, optimized conditions were determined as 100 g/L and 87.5 g/L FWR, 3 and 4 rows of rotor holes, 35 °C and 45 °C cavitation temperature, respectively. At these conditions, total phenolic content (TPC) and antioxidant activity (AA) of SF were 39.5% and 38.6%, respectively higher than the control SF, while for AP, these numbers were observed as 42% and 97%, respectively. IVSD in SF showed 4.7% increase, whereas AP exhibited 7.6% increment in TDF as compared to that of control samples. The study suggests that hydrodynamic cavitation can be successfully used for the preparation of processed foods with increased levels of phenolic antioxidants.

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