Comparative Evaluation of Juices from Red-Fleshed Apples after Production with Different Dejuicing Systems and Subsequent Storage

Abstract

In this work, two vintages (2019 and 2020) of red-fleshed ‘Weirouge’ apples were processed with the innovative spiral filter press technology to investigate juice production in an oxygen-reduced atmosphere. After pressing, a more brilliant red color and appreciably higher amounts of oxidation-sensitive constituents (ascorbic acid, anthocyanins, and colorless (poly)phenols) were seen in spiral filter pressed juices compared to those produced with conventional systems (horizontal filter press and decanter). In a subsequent stability study (24 weeks storage at 4, 20, and 37 °C), the color and phenolic compounds were monitored and differences in the juices produced with the different pressing-systems were widely maintained during the storage period. The analyses of the anthocyanins and colorless (poly)phenols were conducted by UHPLC-DAD-ESI-QTOF-HR-MS/MS and UHPLC-DAD. The spiral filter press emerged as a promising technology for the production of juices with a more attractive color and a better retention of oxidation-sensitive constituents during processing and storage compared to conventional juices.

HS–SPME–GC–MS profiling and sensory analyses of juices from red-fleshed ‘Weirouge’ apples made with innovative and conventional dejuicing systems

“…As described by Volz et al [21], texture-loss occurs much faster in maturing red-fleshed apples as compared to whitefleshed varieties, resulting in a narrow time slot for processing. For this reason, and also due to refrained enzymatical treatment, the yields achieved and presented in our last work [12] of 30.3-35.3 and 35.3-70.1% in 2019 and 2020, respectively, were smaller than those commonly achieved in the industry.…”

“…cv. 'Weirouge') to cloudy juice has been described in detail by Wagner et al [12]. The apples were purchased in both years from a commercial producer Bleichhof (Meckenheim, Germany).…”

“…The most common dejuicing systems for apple juice production are decanter and horizontal filter press that are described in detail in our previous contribution and the respective literature [12,13]. During conventional juice production, oxidation processes are unavoidable and occur immediately after fruit crushing [14].…”

“…The processing steps milling and extraction as well as subsequent steps like filtration and thermal treatment may result in losses or alterations of aroma compounds [15][16][17], affecting both analytical and sensory juice characteristics [18]. Oxygen has been found to be detrimental for color and oxidation-sensitive constituents, i.e., ascorbic acid, anthocyanins, and colorless (poly) phenols when processing red-fleshed apples into cloudy juices applying conventional dejuicing systems, namely a horizontal filter press and a decanter [12]. Our past work showed a better retention of color and the aforementioned constituents, when using an innovative spiral filter press.…”

“…The resulting pressure gradient in the extraction cell causes a simultaneous de-aeration of the product and the juice to leave the extraction cell into an inert buffer tank. A detailed description and graphic illustration of the spiral filter system is shown elsewhere [12]. However, the impact of this promising processing technology on the volatiles and the sensory quality of apple juice has not been assessed in previous studies.…”