Modulation of the phenolic composition and colour of red wines subjected to accelerated ageing by controlling process variables

Effect of Different Winemaking Conditions on Organic Acids Compounds of White Wines

Organic acids represent naturally occurring compounds that are found in many types of food and beverages, with important functions in defining products' final quality. Their proportions in wine are dependent on grape composition and winemaking conditions (temperature, pH levels, oxygen, and carbon dioxide concentration). Therefore, this article studied the influence of different fermentation conditions (200 hL tanks vs. 50 L glass demijohns) and various yeasts on the evolution of the main organic acids during alcoholic fermentation of "Aligoté" wines. The fermentation lasted 22 days and samples were collected daily. Laboratory analyses were quantified according to the International Organization of Vine and Wine recommendations. High-performance liquid chromatography for the identification and quantification of organic acids was used. The data showed the important effect of winemaking conditions on sugar consumption, density or acidity values, and sensory characteristics. Significant differences in organic acid concentrations (especially for tartaric acid) were obtained for all variants, depending on the fermentation conditions, inoculated yeast and the sampling moment. The quantities of most of the identified organic acids were generally significantly increased when glass vessels were used, compared to those fermented in tanks. Most organic acids concentrations were favored by lower pH and showed higher values at lower temperatures.

Evolution of Volatile and Phenolic Compounds during Bottle Storage of Merlot Wines Vinified Using Pulsed Electric Fields-Treated Grapes

This study aimed to elucidate changes in volatile, phenolic, and oenological profiles of wines vinified from Pulsed Electric Fields (PEF)-treated and untreated Merlot grapes during bottle storage of up to 150, 90, and 56 days at 4 °C, 25 °C, and 45 °C, respectively, through chemometrics technique. Wines produced from untreated grapes and those PEF-treated at four different processing conditions (electric field strength 33.1 and 41.5 kV/cm and energy inputs between 16.5 and 49.4 kJ/kg) were used for the bottle storage study. Results showed that hydroxycinnamic and hydroxybenzoic acids in all stored wines, regardless vinified from untreated and PEF-treated grapes, increased as a function of time and temperature, while anthocyanins and selected esters (e.g., ethyl butanoate) decreased. Extreme storage temperature, at 45 °C particularly, resulted in a higher amount of linalool-3, 7-oxide in all stored wines. After prolonged storage, all wines produced from grapes PEF-treated with four different processing conditions were shown to favor high retention of phenolics after storage but induced faster reduction of anthocyanins when compared to wines produced from untreated grapes. Moreover, some volatiles in wines vinified using PEF-treated grapes, such as citronellol and 2-phenylethyl acetate, were found to be less susceptible towards degradation during prolonged storage. Production of furans was generally lower in most stored wines, particularly those produced from PEF-treated grapes at higher energy inputs (>47 kJ/kg). Overall, PEF pre-treatment on grapes may improve storage and temperature stability of the obtained wines.

Impact of Sucrose Addition on the Physiochemical Properties and Volatile Compounds of “Shuangyou” Red Wines

“Shuangyou,” a Vitis amurensis Rupr. variety, is widely cultivated in northeastern and western China. Its berries have high acidity and low sugar content. In this study, different proportions of sucrose were added to the must samples during fermentation to investigate the effect of sugar on the physicochemical properties and volatile compounds of “Shuangyou” wines. The addition of sucrose significantly improved yeast growth and alcohol production, altered the color qualities, and slightly decreased titratable acidity during fermentation. The highest tested proportion of added sucrose resulted in the highest maximum yeast counts and final ethanol concentrations. Moreover, 37 volatile compounds (esters, alcohols, fatty acids, ketones, and aldehydes) were identified and quantified by solid-phase microextraction with gas chromatography-mass spectrometry. The concentrations of these compounds were correlated with the addition of sucrose. Furthermore, the addition of 100 g/L sucrose was sufficient for improving the concentrations of the aromatic compounds. The increase in ester, alcohol, and fatty acid concentration led to a positive OAVs impact (odor activity value > 1) at the end of fermentation.