Determination of phenolic compounds in apples and processed apple products

Abstract

The aim of this preliminary research was to evaluate phenolic compounds content in apples and their processed products. Four cultivars of apples: 'Jonagold', 'Sampion', 'Idared' and 'Topaz' were harvested at commercial maturity during the season of 2004 and processed into clear and cloudy juice as well as apple sauce according to typical industrial technologies. The content of phenolics was determined by the HPLC method using a novel type of chromatographic column Phenomenex Fusion RP. On average the total amount of the determined phenolic compounds in the investigated fresh fruits was 857 mg/kg of fresh weight. The most abundant group was flavonols (417 mg/kg), followed by phenolic acids (229 mg/kg). Significant variations were found comparing the content of different phenolic groups in the investigated cultivars. A highest content of phenolic acids was found in the 'Idared' fruits. Most abundant in flavonols was the cultivar 'Sampion' (477 mg/kg) simultaneously having the lowest amount of phenolic acids. A high content of quercetin glycosides was found in the cvs. 'Jonagold' and 'Topaz'. Processing of apples into apple sauce caused rather small changes in phenolic content whereas during processing into cloudy juices only 53% of fruit phenolics were found in juices. Much higher losses of phenolics were found during clear juices production. A strong effect of temperature on phenolics content was found during the production of clear juices. Juices produced with Panzym MK at 50°C contained 40% of fruit phenolics but juices produced with Rohapect MA Plus at 20°C contained only 19% of initial fruit phenolics.