Raman spectroscopy, being able to provide rich information about the chemical composition of the sample, is gaining an increasing interest in the applications of food. Raman spectroscopy was used to analyze a set of wine samples (red and white) sourced from rarely studied traditional Bulgarian wines. One of the objectives of this study was to attempt the fast classification of Bulgarian wines according to variety and geographic origin. In addition, calibration models between phenolic compounds and Raman spectroscopy were developed using partial least squares (PLS) regression using cross-validation. Good calibration statistics were obtained for total phenolic compounds (by the Folin–Ciocalteu method) and total phenolic compounds and phenolic acids (spectrophotometrically at 280 nm) where the coefficient of determination (R2) and the standard error in the cross-validation (SECV) were 0.81 (474.2 mg/dm3 gallic acid), 0.87 (526.6 mg/dm3 catechin equivalents), and 0.81 (44.8 mg/dm3 caffeic equivalents), respectively. This study has demonstrated that Raman spectroscopy can be suitable for measuring phenolic compounds in both red and white wines.

Protein profile change of Bulgarian Chardonnay wine under the influence of treatment with bentonite was studied. Protein concentration was determined using the Bradford assay, while fractionation was performed via sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The amount of protein found in the original wine was 147.1 mg/dm3, expressed as bovine serum albumin divided into 9 electrophoretic fractions. Low molecular weight fractions with molecular weights of 20, 22 and 24 kDa, were predominant whose share was equal to 65 % of the total electrophoretic fraction profile of wine. The examined wine was treated with four different types of bentonite-two sodium, one activated calcium and one sodium-calcium bentonites. They were added in increasing doses, covering the range of 0.2-3 g/dm3. At lower treatment doses (0.2-0.8 g/dm3), differences in protein concentration reduction were observed. Above the dose of 0.8 g/dm3, an equalization of their effect compared to the reduction of total protein content was reported. Affinity, however small, of the studied bentonites to the different molecular fractions of proteins was observed.

No abstract

In the present study, beers with an original extract 12°P, 14°P and 16°P were obtained. During the maturation process, on different stages, bilberries (Vaccinium myrtillus L.) from Bulgaria were added. Changes in the protein profile of the beers were investigated, as well as the influence of these changes on the body in the mouthfeel and the head retention of the resulting beers. The electrophoretic analysis of the proteins was performed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The protein concentration was determined by the Bradford method. The sensory evaluation of the beer’s body and head retention was conducted by a trained five-membered testing panel. It was found that independently of the original extract, the bilberry addition led to a significant reduction of the protein concentration and the number of protein fractions. Beers with bilberry addition contained between 74% and 94% less protein, than control beers. The number of protein fractions decreased from 10 in the control beers to 4–6 in the beers with bilberry. The fractions with molecular weight 31 kDa and below 14 kDa were the most stable to the bilberry addition. Their part in the beers with bilberry remained the highest. Despite of the significant changes in the protein profiles, the beers with bilberry had very good mouthfeel body and head retention.

The influence of bentonite and cold treatments on some groups of phenolic compounds, color characteristics and antioxidant activity of young red Cabernet Sauvignon wine from Bulgaria was studied. Bentonite was administered in increasing doses in the range of 0.2-1.6 g/L. The wine was chilled at -5 °C for 24 hours. The influence of bentonite on the index 280, phenolic complex and color characteristics was stronger when it was applied in doses of above 0.6 g/L, whereas antioxidant activity was more substantially affected at doses of above 1 g/L. Cold treatment led to greater changes in the studied indices of the composition and antioxidant activity of the wine in comparison to adding bentonite. It led to a decrease in the index 280 by 19 %, and the concentration of the studied phenolic complex groups decreased by about 6-7 %. Color intensity decreased the most of all studied indices. This index was reduced by about 32 %, without a significant change in the composition of its color and shade. The decrease in the content of phenolic compounds is probably the reason for the 23 % decrease in the antioxidant activity of the studied wine.

This scientific research includes sixteen of the most common bentonites on Bulgarian market, which are used by Bulgarian wine cellars in order to achieve colloidal stability of wines. There are bentonites with different composition: sodium, calcium, sodium-calcium, activated calcium, as well as mixtures between natural calcium and activated calcium. Their capacity to transfer elements from and to a model solution with wine parameters have been investigated. Inductively coupled plasma-optical emission spectrometry (ICP-OES), inductively coupled plasma with mass spectrometry (ICP-MS), flame atomic emission spectrometry (FAES) and flame atomic absorption spectrometry (FAAS) techniques have been used. The selected elements, which are subject to this study, are important for human health as well as for the stability of wine clarity.