Wine acidification methods: a review

Global warming is directly linked to a lower concentration in organic acids in grape berries, leading to higher pHs in wine. Because of this lack of acidity, many important factors are impacted, as wine acidity and pH play a crucial role in various equilibriums. Indeed, the lower acidity and the higher pH modify the parameters of wine, such as free and molecular sulfur dioxide availability, colour and sensory aspects. Therefore, it is an ongoing challenge for winemakers to deal with wine acidification and thus preserve wine physico-chemical properties and prevent early spoilage due to microbiological instability induced by high pH. Different acidification methods are allowed by the OIV, chemical acidification being one the most common, followed by physical acidification and microbiological acidification. This review examines these three methods of acidification. The first part details chemical acidification and gives a complete description of various organic acids used in winemaking, and their different properties and regulations; the second part focuses on physical acidification, such as cation exchange resins and electrodialysis; and the last part briefly reviews the novelty of microbiological acidification in wine

Wine acidification methods: a review

Global warming is directly linked to a lower concentration in organic acids in grape berries, leading to higher pHs in wine. Because of this lack of acidity, many important factors are impacted, as wine acidity and pH play a crucial role in various equilibriums. Indeed, the lower acidity and the higher pH modify the parameters of wine, such as free and molecular sulfur dioxide availability, colour and sensory aspects. Therefore, it is an ongoing challenge for winemakers to deal with wine acidification and thus preserve wine physico-chemical properties and prevent early spoilage due to microbiological instability induced by high pH. Different acidification methods are allowed by the OIV, chemical acidification being one the most common, followed by physical acidification and microbiological acidification. This review examines these three methods of acidification. The first part details chemical acidification and gives a complete description of various organic acids used in winemaking, and their different properties and regulations; the second part focuses on physical acidification, such as cation exchange resins and electrodialysis; and the last part briefly reviews the novelty of microbiological acidification in wine

Anthocyanins: Dietary Sources, Bioavailability, Human Metabolic Pathways, and Potential Anti-Neuroinflammatory Activity

The objectives of this chapter are to summarize and discuss (i) the anthocyanins structure and content in foodstuffs and their dietary intake (ii) the anthocyanins bioavailability and human metabolic pathways and (iii) the in vitro and in vivo potent anti-neuroinflammatory effects of anthocyanins and their metabolites. Indeed, anthocyanins are polyphenolic compounds belonging to the group of flavonoids, and are one of the most commonly consumed polyphenols in a normal diet. They are responsible of red, blue and purple color of several fruits and vegetables and their intake has been related with several human health benefits. The anthocyanins structures diversities as well as their content in various fruits, vegetables and cereals is addressed. Moreover, despite the growing evidence for the protective effects of anthocyanins, it is important to highlight that the in vivo bioavailability of these compounds is relatively low in comparison to their more stable metabolites. Indeed, after consumption, these bioactives are subjected to substantial transformations in human body. Phase I and II metabolites generated by intestinal and hepatic enzymatic reactions, and phenolic acids produced by gut microbiota and their metabolized forms, are the most important metabolic anthocyanins forms. For this reason, the study of the biological properties of these circulating metabolites represents a more in vivo realistic situation. Although the anthocyanin bioavailability researches in humans are limited, they will be discussed together with a global metabolic pathway for the main anthocyanins. Moreover, several works have demonstrated that anthocyanins can cross the blood brain barrier, and accumulate in brain endothelial cells, brain parenchymal tissue, striatum, hippocampus, cerebellum and cortex. Consequently, the study of anthocyanins as potent therapeutic agents in neurodegenerative diseases has gained relevance and the principal and the most recent studies are also discussed in the book chapter

Impact of enological tannins on laccase activity

Aims: The aim of this research was to determine and quantify the ability of enological tannins to reduce laccase activity and, consequently, to protect wine color against enzymatic browning and/or oxidasic haze. Methods and results: Botrytized grape juice with laccase activity was obtained by inoculating Botrytis cinerea in healthy mature grapes. Laccase activity was determined in grape juice before and after supplementation with enological tannins using the syringaldazine method. White micro-fermentations were performed in the presence or not of laccase activity and supplemented or not with enological tannins in order to determine how the color was affected. Similarly, red micro-fermentations were performed using white grape juice supplemented with malvidin-3-O-glucoside. All enological tannins inhibited laccase activity and protected the wine color. Conclusion: Supplementation with enological tannins is an interesting tool to inhibit laccase activity and protect the color of white wines from browning and the color of red wines from oxidasic haze. Significance and impact of the study: This is the first scientific study evidencing the inhibitory effect of enological tannins on laccase activity in winemaking conditions. Keywords: enological tannins, Botrytis cinerea, grey mould, laccase activity, contact time, dose effec

Impacts of added oenological tannins on red wine quality to counteract Botrytis infection in Merlot grapes

The contamination of grape berries by Botrytis cinerea can drastically damage wine quality, in particular causing colour degradation. In musts obtained from botrytised grapes, SO2 addition is the main means of avoiding oxidation damage due to laccases excreted by the pathogen. However, consumers are becoming increasingly reluctant to accept SO2 addition to wine. Oenological tannins are used for fining wines because of their colloidal properties, and for wine colour stabilisation due to their ability to condense with anthocyanins. They are also known for their antioxidant and antioxidasic properties. They were thus investigated in the present study for their potential as an alternative to SO2 against laccase oxidation. The impact of various types of oenological tannins on musts and wines was studied once added to musts obtained from the Merlot cultivar, comprising 20 % and 50 % botrytised grapes. Laccase activity, antioxidant capacity, composition of phenolic compounds, spectrophotometric and CIELAB colour parameters were assessed in the musts and wines. Sensory analyses were also performed on 3-month-old wines to evaluate the visual, olfactory and gustative consequences of tannin addition. At a 50 % botrytisation rate, the addition of any type of oenological tannins (at a concentration of 100 g/hL) had no effect on laccase activity and did not protect phenolic compounds. However, at the same concentration and at a 20 % botrytisation rate, proanthocyanidin tannins from grape skin were found to be the most promising tannins with simultaneous protective effects, such as an inhibitory effect on laccase enzymes, protection of colour from complete degradation and preservation of some procyanidin compounds. Oenological tannins are promising candidates for protecting wines from Botrytis damage and they induce a differential effect according to their origin and structure. They could be used to reduce the amount of SO2 that is added during vatting. More research is needed to confirm and better understand the mode of action of various tannins at levels lower than the 20 % botrytised rate tested in the present study

Pomegranate juice ameliorates dopamine release and behavioral deficits in a rat model of parkinson’s disease

Pomegranate juice (PJ) is a rich source of ellagitannins (ETs), precursors of colonic metabolite urolithin A, which are believed to contribute to pomegranate’s neuroprotective effect. While many experimental studies involving PJ’s role in Alzheimer’s disease and hypoxic-ischemic brain injury have been conducted, our knowledge of pomegranate’s effects against Parkinson’s disease (PD) is very limited. Previously, we have reported that PJ treatment improved postural stability, which correlated well with enhancement of neuronal survival, protection against oxidative damage, and ?-synuclein aggregation. Since olfactory and motor deficits are typical symptoms of PD, in this study, we aimed to investigate the capability of PJ to protect against olfactory, motoric, and neuro-chemical alterations. To evaluate its efficiency, Wistar rats were given a combined treatment with ROT (1.3 mg/kg b.w./day, s.c.) and PJ (500 mg/kg/day, p.o.) for 35 days. After this, we assessed the olfactory discrimination index (DI) and vertical and horizontal activities as well as levels of dopamine and its main metabolite 3,4-Dihydroxyphenylacetic acid (DOPAC) in the dissected midbrain of animals. Our findings provide the first evidence that PJ treatment protects against ROT-induced DA depletion in the midbrain, which correlates well with improved olfactory function and vertical activity as well as with the presence of urolithin A in the brain

Antisense down-regulation of 4CL expression alters lignification, tree growth and saccharification potential of field-grown poplar

Transgenic down-regulation of the Pt4CL1 gene family encoding 4-coumarate:coenzyme A ligase (4CL) has been reported as a means for reducing lignin content in cell walls and increasing overall growth rates, thereby improving feedstock quality for paper and bioethanol production. Using hybrid poplar (Populus tremula 3 Populus alba), we applied this strategy and examined field-grown transformants for both effects on wood biochemistry and tree productivity. The reductions in lignin contents obtained correlated well with 4CL RNA expression, with a sharp decrease in lignin amount being observed for RNA expression below approximately 50% of the nontransgenic control. Relatively small lignin reductions of approximately 10% were associated with reduced productivity, decreased wood syringyl/guaiacyl lignin monomer ratios, and a small increase in the level of incorporation of H-monomers (p-hydroxyphenyl) into cell walls. Transgenic events with less than approximately 50% 4CL RNA expression were characterized by patches of reddish-brown discolored wood that had approximately twice the extractive content of controls (largely complex polyphenolics). There was no evidence that substantially reduced lignin contents increased growth rates or saccharification potential. Our results suggest that the capacity for lignin reduction is limited; below a threshold, large changes in wood chemistry and plant metabolism were observed that adversely affected productivity and potential ethanol yield. They also underline the importance of field studies to obtain physiologically meaningful results and to support technology development with transgenic trees

Astringence et amertume dans les vins : origines, mécanismes et maîtrise oenologique.

Article dans une revue professionnell

Carbohydr Res

It is widely accepted that alcoholic beverage quality depends on their ageing in premium quality oak wood. From the choice of wood to beverage ageing, through the different steps in cask manufacturing, many factors should be considered. One of the biggest challenge in cooperages is to take into account all these factors. Most of the studies are interested in phenolic compounds, extracted during ageing and especially involved in wine oxidation, colour, and sensory properties such as astringency and bitterness. Oak aroma volatile compounds have also been the subject of numerous studies. These compounds of interest are part of low molecular weight compounds which represent 2%-10% of oak wood composition. However, three polymers constitute the main part of oak wood: cellulose, hemicellulose and lignin. As far as we are aware, few studies concerning the role of these major macromolecules in oak wood have been published previously. This article reviews oak wood polysaccharides and lignin, their potential interest and different assays used to determine their content