Bioactive Compounds of Juice and Peels of Yuzu Fruits Cultivated in Switzerland.

Yuzu is a citrus fruit cultivated mainly in northeast Asia. Due to the huge gastronomic interest emerging in recent years, some attempts to grow yuzu in Europe are being made. Juice and peel of yuzu cultivated in Switzerland have been characterised in this study. Peel constituted the major part of yuzu fruit followed by flesh, juice and seeds. The fruit degree of maturity was investigated by measuring pH, total titratable acidity and total soluble solids of the juice. The analyses were pursued by determining the content of vitamin C, malic and citric acids amounting to 0.560, 6.18 and 44.7 g/L, respectively. Four flavanones: naringin, hesperidin, naringenin, and hesperetin were identified and quantified in both juice and peel. The most abundant flavanone was hesperidin with 47 µg/mL and 640 µg/g dry matter (DM) in juice and peel, respectively. For the first time yuzu grown in Switzerland have been analysed and the obtained values have been compared with literature for other citrus fruits. Yuzu juice showed higher contents of citric and malic acid. Yuzu cultivated in Switzerland contained nearly twice as much vitamin C as yuzu juices from different regions of Japan. The content of vitamin C of yuzu was as high or higher than in most other citrus fruits. Large differences in the content of flavanones in yuzu juice from different regions of Japan were reported, in general the values noted were lower than those in the present study.

Stability of goji bioactives during extrusion cooking process.

Due to the increasing popularity of goji berries, efforts are made to enlarge the offer of goji containing foods. In this study, rice flour based extrudates enriched with goji berries were investigated. The extrusion was performed using a twin screw extruder with constant feed moisture and screw speed. Raw mixtures as well as extruded products obtained were analysed in order to determine antioxidant activity and contents of rutin, zeaxanthin dipalmitate and 2-O-ß-d-glucopyranosyl-l-ascorbic acid. The antioxidant activity of goji extrudates was boosted up to 20times compared to the extrudates without any addition. The process of extrusion increased the antioxidant activity despite of decrease in rutin content. Regardless of extrusion conditions rutin retention in the extrudates was not lower than 60% compared to the respective raw mixtures. In the case of zeaxanthin dipalmitate the retention level was around 40%. 2-O-ß-d-glucopyranosyl-l-ascorbic acid was stable at the conditions applied.