Biodiversity of Total Phenolics, Antioxidant Capacity, and Juice Quality in Apple Cider Taxa

Apples are known to contain antioxidants that may play an important role in human health by providing protection against reactive free radicals affecting a wide range of biological molecules including nucleic acids, lipids, and proteins. While fresh apple juice is a main product of processed apples, there is little information on cultivar differences or on the impact of pasteurization on apple juice antioxidant properties. The objectives of this study were to document differences among apple species and cultivars in antioxidant properties and to define the effect of pasteurization on total phenolics content, antioxidant capacity, and juice quality. Juice from the fruit of 21 apple cultivars (Malus domestica) and eleven apple species (M. sieversii) was extracted and divided into two equal portions. One portion was immediately pasteurized in a water bath for 30 min at 75℃. Non-pasteurized and pasteurized samples were tested for total phenolics content using Folin-Ciocalteu reagent. Depending on their total phenolics content, these were divided into eleven similar groups using Duncan's multiple range test. Nine cultivars and two species representing the eleven groups were selected for further investigations. Juice browning, soluble solids content, pH, and total phenolics content were determined for both non-pasteurized and pasteurized juice samples. Antioxidant radical scavenging capacity was measured with a 2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) assay. In non-pasteurized juice, total phenolics content ranged from 107.9 to 1,555.0 mgㆍL-¹ and from 127.1 to 2,212.3 mgㆍL-¹ in pasteurized juice. ABTS radical scavenging capacity ranged from 16.2 to 63.3 mM trolox equivalent antioxidant capacity in non-pasteurized juice and from 11.5 to 41.3 mM in pasteurized juice. Pasteurization had no effect on total phenolics content, but had a significant effect on antioxidant capacity. There was a significant difference among cultivars and species in both cases. Pasteurization decreased juice browning only for M. sieversii 4002.a and there was no effect on other taxa. Pasteurization had no effect on soluble solids content nor on juice pH. The results suggested an approximate 92 and 73% relationship between total phenolics and ABTS radical scavenging in non-pasteurized and pasteurized juices, respectively. There was no relationship between total phenolics content and juice browning, total soluble solids content, or pH. This study advances the understanding of the biodiversity of total phenolics components and antioxidant capacity of apple juices, their quality, and the relationship among them.