Effect of microwave-assisted extraction and autoclave extraction on the physicochemical properties of holy basil (Ocimum sanctum L.) by-product powder

This study investigated the potential to valorize Holy Basil ( Ocimum sanctum L. ) processing by-products into a functional powder by comparing the effects of two novel extraction methods, Microwave-Assisted Extraction (MAE) and Autoclave Extraction (AE), applied for 10, 20, and 30 minutes. While employing standard, non-comparable solid-to-liquid ratios optimized for each technology (MAE 1:0.4 w/v, AE 1:10 w/v), the experiment aimed to determine the optimal conditions for enhancing physicochemical and antioxidant properties through distinct thermal modification mechanisms. Results showed that both MAE and AE treatments significantly improved the nutritional profile, achieving a substantial increase in crude fiber and total dietary fiber by reducing non-fiber components. Crude fiber peaked at 42.90% (AE-30). Both methods significantly increased antioxidant activity (DPPH, ABTS, FRAP) and the concentration of Total Phenolic Compounds (TPC) and Total Flavonoids (TF) ( p < 0.05). Crucially, the methods exhibited divergent functional effects: MAE-30 was superior for maximizing TPC (103.21 mg GAE/g sample) and Water Solubility Index (WSI) (98.21%), linked to the large, irregular pores observed via microstructural analysis. Conversely, AE-30 optimized Water Holding Capacity (WHC) (6.18 g/g) and Insoluble Dietary Fiber content due to better structural integrity. Both methods successfully transform agricultural by-products into valuable, high-fiber, antioxidant-rich ingredients, with MAE-30 providing the optimal conditions for a highly soluble, bioactive powder. • Holy Basil by-products are valorized into high-fiber, bioactive powders. • MAE is superior for maximizing TPC (103.21 mg GAE/g) and WSI (98.21%). • AE maximizes IDF (62.20%) and WHC (6.18 g/g). • Thermal extraction disrupts cell structure; Crude Fiber increased (up to 42.9%). • MAE-30 offers the optimal profile for soluble, antioxidant-rich ingredients.