Discrimination of Juice Press Fractions for Sparkling Base Wines by a UV-Vis Spectral Phenolic Fingerprint and Chemometrics

White wine phenolics: current methods of analysis

White wine phenolic analyses are less common in the literature than analyses of red wine phenolics. Analytical techniques for white wine phenolic analyses using spectrophotometric, chromatographic, spectroscopic, and electrochemical methods are reported. The interest of research in this area combined with the advances in technology aimed at the winemaking industry are promoting the establishment of novel approaches for identifying, quantifying, and classifying phenolic compounds in white wine. This review article provides an overview of the current research into white wine phenolics through a critical discussion of the analytical methods employed. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Helium Atmospheric Pressure Plasma Jet Source Treatment of White Grapes Juice for Winemaking

In the last few years, new emerging technologies to develop novel winemaking methods were reported. Most of them pointed out the need to assess the barrel aging on the wine product, fermentation process, green technologies for wine treatment for long term storage. Among these, plasma technologies at atmospheric pressure are on the way of replacing old and expensive methods for must, wine and yeast treatment, the goal being the long-term storage, aging and even decontamination of such products, and seems to meet the requirements of the winemakers. Using the principles of dielectric barrier discharge, we power up an atmospheric pressure plasma jet in helium. This plasma is used for treatment of fresh must obtained from white grapes. Our research manuscript is focused on the correlation of plasma parameters (applied voltage, plasma power, reactive species, gas temperature) with the physico-chemical properties of white must and wine (1 and 2 years old), via ultraviolet–visible and infrared spectroscopy, and colorimetry. Two types of white must were plasma treated and studied over time. The 10 W plasma source did not exceed 40 °C during treatment, the must did not suffer during thermal treatment. A higher quantity of RONS was observed during plasma-must exposure, supporting further oxidation processes. The UV-Vis and FTIR spectroscopy revealed the presence of phenols, flavones and sugar in the wine samples. Simultaneous visualization of CIE L*a*b* and RGB in color space charts allows easier understanding of wine changing in color parameters. These experimental results supporting the possible usability of atmospheric pressure plasma for winemaking.

Slovak Tokaj wines classification with respect to geographical origin by means of one class approaches

Tokaj wines could be produced only in so called Tokaj/Tokay wine region that falls within two countries Slovakia and Hungary. Thus, wines bearing Tokaj appellation must be produced only in Hungary and Slovakia by traditional process. Unfortunately, some counterfeit wines from neighbour region in Ukraine could be found in market. The aim of this work is to explore a simple UV-VIS spectrum to recognise true Tokaj/Tokay wines from counterfeits and try to differentiate wines based on their country of origin. This type of question can be duly answered using one class classification approach. Two different approaches, Data Driven Soft Independent Modelling of Class Analogy - DD-SIMCA and One-Class Partial Least Squares - OC-PLS were tested and evaluated for this purpose. In both cases, rigorous way models were built and optimized using only samples of the target class. A set of external samples containing samples from target class and non-target were used to validate the models ability to recognize Slovak samples and reject non-Slovak samples. Model based on DD-SIMCA showed better performance (97% correct rating) compared to OC-PLS models (80% correct rating). Comparing both approaches in terms of sensitivity and specificity, both exhibit high sensitivity (low false negative rate: DD-SIMCA 95% and OC-PLS 100%), however the OC-PLS based model showed low specificity (40%) while DD-SIMCA showed high specificity (100%) rejecting all samples out of Slovak origin. Therefore, the results found in this study show that it is possible to successfully combine UV-VIS spectra and DD-SIMCA models to discriminate Tokaj wine samples of Slovak origin from others. Equally important is environmentally friendly (fast, simple, absence of solvents) classification method in line with green chemistry.

A Comparison of Laboratory Analysis Methods for Total Phenolic Content of Cider

Total phenolic content is widely accepted as a key measure of quality for cider. Apple juice and cider, made from six apple varieties including dessert and cider apples, were analysed for total phenolics using three different methods: (a) the Folin-Ciocalteu method, (b) the Somers method (a spectrophotometric method developed specifically for wine), and (c) ultra-performance liquid chromatography (UPLC) as a benchmark test. Of these approaches, the Somers method had the strongest correlation with UPLC with an R2 value of 0.99, whilst the Folin-Ciocalteu correlated with UPLC with an R2 value of 0.89. The Folin-Ciocalteu method also had a strong positive correlation with the Somers approach with an R2 value of 0.91. Correlations between methods were strongest for apple varieties that were naturally high in phenolic content. These results highlight the potential of the Somers method to rapidly, inexpensively, and accurately report the total phenolic content of apple juice and ciders made from dessert and cider apple varieties.

Phenolic Content of Apple Juice for Cider Making as Influenced by Common Pre-Fermentation Processes Using Two Analytical Methods

Pre-fermentation methods can influence the cider produced from apple juice. This study analyses the influence of pre-fermentation methods; maceration and press fractioning, on the total phenolic content of juice from four apple varieties; ‘Red Delicious’, ‘Pink Lady’, ‘Sturmer’, and ‘Bulmer’s Norman’. The must was macerated for 0 or 2 h and juice was collected at free run or under 200 kpa. Base juice characteristics and total phenolic content was analysed using the Folin–Ciocalteu method and spectrophotometric absorbance at 280 nm (A280), a method used for the analysis of white wine. Both methods of analysing the total phenolic content were used, measuring the same samples to determine if the methods are comparable. No interaction was found between pre-fermentation technique and the results varied by variety and analytical method. High pressure improved the phenolic extraction for ‘Bulmer’s Norman’ juice compared to free run juice when analysed by A280. Non-macerated juice had higher total phenolic content than macerated juice for ‘Red Delicious’ and ‘Pink Lady’ juice when analysed using the Folin–Ciocalteu method. There was a moderate positive correlation between the analytical methods.

Influence of the Scanning Temperature on the Classification of Whisky Samples Analysed by UV-VIS Spectroscopy

The definition of the optimal temperature and its effects (either increasing or variations) during analysis of alcoholic beverages are of importance to develop protocols based in spectroscopy. Although several reports have been published on the use of spectroscopy combined with chemometrics to classify and authenticate alcoholic beverages (e.g., wine, tequila, whisky), few reports deal with issues related with the spectra collection (e.g., temperature, path length) and its effect on the classification performances. The objective of this study was to evaluate the effect of increasing temperature on both the UV-VIS spectra of whisky and on the classification results of the samples according to country of origin. Whisky samples from different commercial labels were analysed at different temperatures (25, 35, 45, 55 °C) using a UV-VIS instrument (Agilent, Cary 3500). Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) models based in cross validation were used to classify whisky samples according to scanning temperature and origin. The results of this study indicated that temperature did not affect the classification of whisky samples according to country of origin. Overall, well defined protocols need to be defined for routine use of these methods in research and by the industry.