Comparative Evaluation of Ultrasonic, High Pressure, and Pulsed Electric Field Processing on the Extraction and Storage Stability of Betalains From Red Beet By-Products

This study explores the potential of red beet peel (RBP) and red beet stalk (RBS), often underutilized by-products, as rich sources of natural pigments and bioactive compounds. Three non-thermal green extraction methods, namely, high-pressure processing, ultrasound, and pulsed electric field treatment, were evaluated for their efficiency in extracting betalains, total phenolics, flavonoids, and antioxidant activity (AOX). Among these, sonication at 300 W for 10 min proved most effective for both RBP and RBS, yielding the highest concentrations of bioactives. Crucially, this work goes beyond conventional yield assessments by addressing the post-extraction storage stability of these compounds over 120 days under refrigeration. Kinetic modeling revealed that betalains and phenolics degraded following first-order kinetics, whereas AOX increased over time and followed a zero-order model. Sonicated samples demonstrated superior pigment stability, with betaxanthins more stable than betacyanins. This study highlights the importance of integrating degradation kinetics with extraction optimization and offers a novel perspective on the valorization of red beet by-products. The findings are particularly relevant for food and nutraceutical industries seeking to develop shelf-stable, functional plant-based ingredients.