Ultrasound-IR combination improves physicochemical and antioxidant properties of Mushk budji rice

Abstract

The present study examines the impact of ultrasound assisted infrared (IR) drying on physicochemical, nutritional, and thermal characteristics of Mushk budji rice, an aromatic rice variety locally grown in Kashmir. The effects of ultrasonic pretreatment (2–6 h) and IR drying (35–55 °C) on starch composition (amylose amylopectin ratio), antioxidant activity, vitamin retention and thermal and pasting properties were measured. The outcome showed that ultrasound led to a relative increase in amylopectin content (maximum 84.87%) and a decrease in amylose due to leaching from swollen starch granules. The best result was observed in moderate ultrasonication (4 and 5 hours) with maximum thiamine (0.00627 mg g⁻¹), riboflavin (0.08863 mg g⁻¹), and niacin (0.0689 mg g⁻¹) at low drying temperatures (35 °C). Likewise, the maximum total phenolic content (4.64 mg GAE g⁻¹), total flavonoid content (5.77 mg g⁻¹) and antioxidant activity (DPPH, 68.9%) were observed at 4 h of ultrasonication and declined with increasing exposure or drying temperature, which is an indication of oxidative degradation of bioactives. The analysis of pasting properties and DSC showed that ultrasonic samples had lower peak viscosity and gelatinization temperature, suggesting that the granules were disrupted and their water absorption was enhanced. The outcome also showed that the parameters related to antioxidants (total phenols, flavonoid and DPPH activity) and water-soluble vitamins (thiamine, riboflavin and niacin) were more sensitive to processing conditions compared with starch-related components. Altogether, the use of ultrasound-assisted IR drying showed a significant positive effect on the nutrient and antioxidant activity and starch functionality of Mushk budji rice, which can be considered a promising method for processing rice in terms of high quality and low energy consumption.