Upcycling Chili Pepper Processing Waste into a Capsaicinoid-Rich Spicy Oleoresin Food Ingredient: A Review of Ultrasound-Assisted Extraction Studies

The growing demand for spicy foods and industrial production of hot sauces and spicy condiments from chili pepper (Capsicum spp.) generates substantial quantities of by-products, mainly composed of placenta, seeds, and fibrous tissues, which retain significant concentrations of capsaicinoids and other valuable phytochemicals. These residues represent an underexploited resource for the development of high-value food ingredients. This review critically examines the valorization of chili pepper processing by-products through the recovery of capsaicinoid-rich oleoresins, with particular emphasis on ultrasound-assisted extraction (UAE) using ethanol-based solvents. The ultrasound-enhanced mass transfer and processing parameters, extraction yields, oleoresin spiciness, and scalability challenges were discussed. Past studies showed UAE substantially reduces extraction times while improving process efficiency and enabling the production of oleoresins with high pungency. Sonication times of 8–20 min and temperatures between 35 and 65 °C produced oleoresin yields ranging from 19 to 28% (dry basis) depending on the chili pepper variety and processing conditions. Pungency values reached 953,920 Scoville Heat Units for oleoresin obtained from the by-product of Carolina Reaper pepper variety. Limitations of ultrasound technology regarding process standardization and scale-up were also discussed. Overall, UAE emerges as a promising technology for transforming chili pepper industrial waste into natural spicy ingredients.