Reintegration of grape stem, a by-product from wine production, into the food chain is of high interest from an economic and environmental perspective. Therefore, an investigation of stems was undertaken and is described here. It is known that quality of stems is of high variability. In this study the stems from four grapevine varieties (Syrah, Cabernet Sauvignon, Merlot and Chasselas) cultivated in Switzerland were treated in following ways: drying, cutting and separation into fractions based on particle size. All fractions were then characterised for their phenolic compounds content. It was found that Chasselas fractions contained most phenolic compounds. The addition of grape stems of the four different varieties allowed reduction of the protein content of a model wine. The extent of protein precipitation was highly correlated with the amount of phenolic compounds in stems added. Among the examined varieties, Chasselas brought most promising results, with the high reduction of the protein at low level of stem addition.

on the content of phenolic compounds depends on two opposite outcomes: decomposition of heat-labile compounds and disruption of the cell wall followed by a release of covalently bound phenolic compounds [Wang et al., 2014]. Stating about a potential health effect of food components should be preceded by bioaccessibility assessments confirming that after the digestion process the compound of interest is still present and available for absorption. Bioaccessibility is defined as the amount of a compound that is released from the food matrix and is considered to be available for absorption through the gut wall [Fernández-García et al., 2009]. Bioaccessibility depends on processing and interactions with components of the food matrix, such as proteins for example. It may be determined by analysing the digesta after an in vitro gastro-intestinal digestion using enzymes under controlled conditions such as pH, temperature, ionic strength, and digestion time. Conducting human trials being costly and ethically disputable, simulated in vitro digestions have the advantage to be more rapid and less expensive [Minekus et al., 2014]. Gou Qi Zi, Lycii Fructus, wolfberry or goji berry are the names given to fruit of Lycium barbarum, a plant from the Solanaceae family, growing in the temperate and subtropical zones of the world [Levin et al., 2011]. In the traditional Chinese medicine, goji berries are recommended for their capacity to strengthen muscles, protect liver functions, regenerate the vital essence, and improve visual acuity [Huang, 1998]. Due to their potential benefits for human health

Awareness of health benefits of goji berries coming from their bioactive compounds, mostly antioxidants like ascorbic acid, has grown. Recently, an ascorbic acid analogue from goji berries, the 2-O-β-D-glucopyranosyl-L-ascorbic acid has been reported. In rats, the analogue is absorbed intact and in the form of free vitamin C and consequently has been proposed as a provitamin C. Synthesis of the analogue is demanding and laborious and therefore reliable natural sources are searched. Knowledge concerning the analogue's occurrence in other parts of goji plant is lacking. The aim of this study was to evaluate the contents of 2-O-β-D-glucopyranosyl-L-ascorbic acid in rhizomes, stems and leaves from Lycium barbarum. Rhizomes, stems and leaveswere extracted and the content of 2-O-β-D-glucopyranosyl-L-ascorbic acid and non glucosylated, free ascorbic acid was determined by HPLC-DAD. 2-O-β-D-glucopyranosyl-L-ascorbic acid was found in all goji plant tissues investigated. Based on dry weight, 3.34 mg/100 g were found in the leaves, 4.05 mg/100 g in the stems and up to 12.6 mg/100 g in the rhizomes. Nevertheless, the analogue content in goji berries is much higher (40 to 280 mg/100 g dry weight). The present study confirmed the presence of 2-O-β-D-glucopyranosyl-L-ascorbic acid in rhizomes, stems and leaves of Lycium barbarum. However, their content compared to goji berries is considerably lower.