Simultaneous dewatering and wax extraction of Chinese winter jujube (Ziziphus jujuba Mill. cv. Dongzao) fruit by subcritical dimethyl ether

Abstract

Due to its highly perishable nature, fresh Chinese winter jujube fruit is preserved, commonly by drying. In this study, dewatering of fresh Chinese winter jujube was carried out by subcritical dimethyl ether (DME). Additionally, wax was simultaneously extracted from the fruit during the dewatering process. The maximum dehydration efficiency was 93.33 ± 0.34% when the dewatering experiment was conducted at 55 °C with 8 cycles. The content of total soluble solids, total sugars, and total flavonoids of dried jujube fruit (JD) by subcritical DME dewatering was somewhat lower than those in the freeze-dried jujube fruit (JF). However, the content of total phenols and VC in JD was close to those in JF, and the protein content in JD was higher than that in JF. The extracted wax primarily comprised acids, the most abundant of which was hexadecanoic acid. It had melting points of 53.71 °C–54.62 °C. The study demonstrates that subcritical DME can be used to dry Chinese winter jujube fruit. There is a small loss of nutritional content, but the speed, economy, and environmental friendliness of the process are advantages compared to other methods. Results further suggest that jujube wax has potential for use in the cosmetic and food industries.