Sustainable ultrasound-assisted extraction and encapsulation of phenolic compounds from sacha inchi shell for future application

Sacha inchi shell (SIS), an underutilized by-product of sacha inchi oil processing, is a rich source of phenolic compounds. In this study, ultrasound-assisted extraction (UAE) was optimized by response surface methodology (RSM) with a Box–Behnken design to investigate the effects of time (15–25 min), temperature (25–45 °C), and ethanol concentration (40–80%) on the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity by DPPH assay of the obtained extracts. The maximum TPC was at 15 min, 45 °C and 60%, TFC at 25 min, 45 °C and 60% and DPPH at 15 min, 35 °C and 80%. The optimized condition selected for encapsulation purposes was at 25 min, 35 °C and 80% ethanol concentration. RSM analysis showed that all models analyzed for all three assays were significant at 95% confidence. The SIS extract had a greater inhibitory zone against Escherichia coli measuring 15.34 mm at a concentration of 30 µg/mL than Staphylococcus aureus among the samples. The spray-dried microcapsules using different combinations of gum arabic and maltodextrin (GMM 1 and GMM2) resulted in a proper encapsulation layer and a smoother surface and shape obtained at 1000× magnification. Also, GMM 1 and GMM2 had particle sizes ranging from 2.95 ± 0.02 to 27.73 ± 0.38 and from 5.20 ± 0.01 to 29.30 ± 0.42 µm, respectively. The microcapsules were in the acceptable ranges for moisture content (<5%) and water activity (<0.6). It has been concluded that SIS extract showed high antioxidant and antimicrobial properties and its encapsulation could be further used in food and nutraceutical formulations.

This research project was supported by the 90th Anniversary of Chulalongkorn University Scholarship under the Ratchadaphisek Somphot Fund, Batch 53 Academic Year 2022, Graduate School, Chulalongkorn University.