Stability, release mechanisms, and applications of double emulsions loaded with Opuntia extracts: a comprehensive review

Abstract

Background: Opuntia cactus, or prickly pear, is a good source of bioactive compounds, especially betalains that have high antioxidant activity and play an important role in human health. However, despite their nutritional and functional benefits, these compounds are highly sensitive to environmental conditions, leading to reduced stability and bioactivity during processing and digestion. Scope: To overcome the stability challenges, double emulsions (W1/O/W2) have emerged as an innovative encapsulation and delivery system for bioactive compounds. This review explores the structural characteristics of double emulsions, their encapsulation mechanisms, and models describing release kinetics under digestive conditions. Factors influencing emulsion stability—including emulsifier type, droplet size, phase ratio, and processing conditions—are critically discussed. Studies demonstrate that double emulsions can significantly enhance the stability, bioaccessibility, and controlled release of sensitive compounds such as betalains, while maintaining desirable sensory and functional properties. Their successful incorporation into various food matrices, including beverages, dairy, and bakery products, has resulted in improved nutritional profiles, antioxidant retention, and extended shelf life. Additionally, industrial scalability and formulation challenges are examined, emphasizing the importance of optimizing processing parameters and ensuring consumer acceptability. Conclusion: Double emulsions provide a novel approach to improve the stability and delivery of bioactive ingredients in functional foods. Future research and development should focus on optimizing their design and functionality, enabling widespread application across the food industry and healthier food products.