Chemical constituents and antioxidant activity of Japanese quince (Chaenomeles japonica) juice and pomace

Abstract

Juice is one of the most valuable fruit and vegetable processing products. Quince (Chaenomeles japonica) juice is an important and natural product with high nutrient value and positive influence on human health. Quince juice can be used in the food industry as a high acidity ingredient, as well as a strong antioxidant due to the high content of phenolic compounds and vitamin C. When it comes to juice processing, about half of the fresh produce is considered waste, since pomace left after the juice pressing content is 32 to 51% of fresh fruit weight. In this study, we investigated the biochemical composition and antioxidant activity of pomace, focusing on the benefits of the by-products and their potential for use. Fresh quince fruits were processed into juice and pomace left after the juice pressing was dried, ground and extracted with methanol. The antioxidant activity of the samples was tested using the DPPH free radical scavenging assay. The concentrations of total phenolic compounds were measured spectrophoto-metrically using the Folin-Ciocalteu phenol reagent and expressed as gallic acid equivalents and proanthocyanidin contents were expressed as (+)-catechin equivalents. The total phenolics content in pomace was 22.9 and 25.9 mg/g dry weight (DW) for peeled and unpeeled fruits respectively. Proanthocyanindin content in pomace obtained from peeled and unpeeled quince was 5.23 and 9.62 mg/g DW, respectively. Antioxidant activity of dried pomace was found to be more than four times higher than in quince juice. The results of this study show that quince pomace is a rich source of phenolic antioxidants which could be used for new value-added products development.