Recent Advances in Flavonoid Extraction Technology and its Nitrite-Scavenging Activity

Abstract

This review examines recent advances in flavonoid extraction technologies and their relevance to nitrite scavenging in pickled vegetable systems. Nitrite accumulation during vegetable fermentation is             associated with raw-material nitrate content and microbial nitrate reduction, and it may pose health risks through acute toxicity and potential nitrosamine formation. The manuscript summarises current nitrite detection and control strategies, with emphasis on plant-derived flavonoids as natural scavenging agents. Three mechanisms are considered: direct electron-transfer-based nitrite scavenging, inhibition of nitrosation reactions, and regulation of nitric oxide metabolism. Extraction technology is identified as a key factor influencing flavonoid yield, structural retention, and nitrite-scavenging performance. Conventional methods, including reflux extraction, water extraction, and ethanol maceration, are discussed alongside advanced approaches such as semi-bionic extraction, ultrasound-assisted aqueous two-phase extraction, ultrasound-assisted extraction, microwave-assisted extraction, and supercritical fluid extraction. Green extraction using deep eutectic solvents and natural deep eutectic solvents is further reviewed because of its potential to improve extraction efficiency and preserve bioactivity. Evidence from pickled food and in vitro systems suggests that flavonoid extracts can reduce nitrite levels, although efficacy depends on plant source, extraction method, pH, temperature, reaction time, and dosage. The review highlights the need to connect extraction optimisation with practical food-system validation and to assess flavonoid stability in complex fermentation matrices.