The aim of this work was to study the combined application of a pulsed electric field (PEF) and an enzymatic treatment to white wine mash. The resulting impact of membrane permeabilisation by electroporation and pectin degradation by enzymes on fermentation behaviour and quality of white wine was assessed. The mash of two varieties, Traminer and Grüner Veltliner, was PEF treated (3 and 10 kJ/kg) using a continuous co-linear treatment chamber. Pectinases were added immediately afterwards and maceration was performed for 4 and 24 h. Various physico-chemical parameters were analysed at different stages of the production process and the impact of the combined treatment on volatile compounds such as esters and terpenes was analysed by gas chromatography-mass spectrometry and a sensory panel in the final white wine after bottling and storage. Regardless of the PEF treatment intensity, the variety and the maceration time, the release of juice was not significantly influenced. For Traminer, the fermentation time was reduced through the enhanced extraction of nitrogen from 322 to 359 mg/L due to PEF treatment (10 kJ/kg). The release of phenols which were localized in the pulp, were significantly more affected than phenols from the skin. Although the concentration of selective esters especially of the variety Traminer significantly increased, the sensory evaluation indicated no positive effect on the olfactory properties. Overall, the combination of PEF and enzyme pretreatment showed benefits in reducing the fermentation time and increasing the content of selective esters for Traminer.

The impact of different amounts of the hydrocolloid xanthan gum (E415) on the typicity and flavour intensity of cloudy apple juice was tested by means of a survey for the first time by consumers. Consumers distinguished juice with even 0.5 g L–1 xanthan gum significantly in its typicity from the original apple juice. Increasing amounts of the stabilizer led to further degradation of typicity. The thickened juices were described as “slimy” with an untypical mouthfeel. Aroma intensity of the apple juice was affected negatively by addition of xanthan gum as well. Even 1.0 g L–1 of the stabilizer caused a significant decline of flavour intensity assessed by the consumers compared to the original juice. Viscosity increased significantly by adding xanthan gum, as well as turbidity. Colour components were affected differently. The addition of xanthan gum can therefore not be recommended for apple juice. Practical applications Presently, a worldwide discussion is going on about the legal permission of hydrocolloids in beverages, especially in fruit and vegetable juices and nectars. In Europe the addition of pectin (E440) is only allowed in pineapple and passion fruit juices. Additives belonging to the food additive group 1 (including xanthan gum (E415), gellan (E418), carboxymethyl cellulose (E446) and others) are allowed in vegetable juices only (regulation (EC) No 1333/2008). Studies show divergent results of the necessity and the impact of hydrocolloids on sensorial properties of beverages. The results of this study show that an average untrained consumer rejects cloudy apple juices thickened with xanthan gum even at low levels. Therefore, neither quality can be improved nor consumption of fruit juice can be increased by the addition of xanthan gum.