Addition Protocols and Their Effects on Extraction and Retention of Grape Phenolics during Red Wine Fermentation and Aging

Extraction and retention of red wine phenolics, particularly anthocyanins and tannin, have historically been a primaryconcern for many red wine producers. This research compares two competing protocols designed to facilitate the extraction andretention of grape phenolics through the addition of exogenous enological tannin to evaluate their relative effectiveness. The firstprotocol involves adding exogenous tannin in a single full-dose at or immediately after destemming/crushing the grapes. The secondprotocol, commonly referred to as the ＂sacrificial＂ protocol, involves splitting the addition into two half-doses. The first half-dose, orsacrificial dose, is applied at or immediately aflei＂ destemming/crushing, and the second half-dose is added a few days later. Thespecific mechanisms involved in the extraction dynamics are not elucidated here, however, phenolic profiling before and duringfermentation as well as one full year after, using UV-Vis and AWRI tannin portal methodology, has shown a clear advantage to theuse of a single-dose protocol with respect to the extraction and retention of grape phenolics. Possible explanations are proposed anddiscussed.

Physico-Chemical and Microbiological Profile of Wine Lees of Red Wines from Local Grapes Varieties

In the Republic of Moldova, the viticulture industry is a sector with a high economic impact, and the utilization of secondary products from winemaking represents a growing concern regarding environmental sustainability. Wine lees, one of the types of wine waste, is less studied in order to valorize it. Currently it is used in the production of ethyl alcohol, as aggregates in the soil and others. The aim of this study was to characterize from a physico-chemical and microbiological point of view the lees sediments obtained after the primary fermentation of three types of individualized red wines made from autochthonous grapes varieties. It was found that residual yeasts represent a valuable raw material containing carbohydrates (from 14.35% ± 0.19% to 25.11% ± 1.51% SU), lipids (from 4.61% ± 0.21% to 9.41% ± 2.04% SU), proteins (from 42.62% ± 1.57% to 77.62% ± 9.14% SU), anthocyanins (from 9.18 ± 0.15 to 22.78 ± 1.60 mg cianid) and beta-glucans (from 12.84% ± 0.01% to 17.42% ± 0.02%). The pH value of wine lees ranges from 3.49 ± 0.0 to 3.083 ± 0.01, the dry matter from 9.62% ± 0.22% to 25.06% ± 0.42% and the ash from 0.03% ± 0.42% to 0.035% ± 0.21%. The microbiological study confirmed the presence of live yeasts of the genus Saccharomyces cerevisiae, which remain active due to the presence of residual sugars and oxygen. The results of the research are promising and encourage the obtaining of new products with special purpose and added value.

Application of different pre-fermentation techniques in the winemaking using Guankou table grape(Vitis vinifera×Vitis labrusca)

The study produces white wines with the table grape(Guankou grape,Vitis vinifera×Vitis labrusca)using different pre-fermentation techniques to reduce bitterness and enhance aroma.Pre-fermentation techniques included pressing levels,low-temperature maceration,ultralow temperature freezing,hyperoxidation,and their different combinations.The compounds were analyzed by ultraperformance liquid chromatography(UPLC)and solid-phase microextraction(SPME)coupled with gas chromatography-mass spectrometric(GC-MS)analysis.The results shown that different pre-fermentation techniques influence the extraction of phenolic and aroma compounds,further forming different sensory qualities.The more damaging process increases the bitter phenols and unpleasant aroma compounds.Flavonoids,tartaric acid esters,and gallic acid esters caused bitterness,and 2,5-bis(1,1-dimethylethyl)-phenol mainly generated aromas of stone fruits.Finally,the results of the comprehensive evaluation of the sensory analysis suggested that after destemming and maceration(4±1℃,for 24 h),the most aromatic wines are fermented with pressed juice(pressure from 0.5 to 1.0 bar),and the most harmonious wines are fermented with free juice.The study provides a strong basis for winemaking with table grapes.