Month: March 2019

Aging of Aglianico and Sangiovese wine on mannoproteins: effect on astringency and colour

By Alessandra Rinaldi

Mannoproteins (Mps) are naturally present in wine, because they are integral constituents of yeast cell wall. In winemaking conditions Mps are released by Saccharomyces cerevisiae during two phases of yeast cell cycle: 1) during alcoholic fermentation when cells are actively growing; and 2) during autolysis when cells are dying. The release of these compounds during wine aging on lees contributes to the organoleptic and physicochemical properties of wines. During the last years different commercial preparations based on yeast derivatives have been used in order to replace traditional ageing on lees, and actually are authorized by the International Organisation of Vine and Wine (Oeno 26/2004). Besides white wines, mannoproteins showed beneficial effects also on red wines, contributing to colour stability, to tasting improvements and flavor complexity (Pozo-Bayón, Andújar-Ortiz, & Moreno-Arribas, 2009). In this work, three commercial mannoproteins (MP; MF; MS) were tested in Aglianico and Sangiovese red wine during one year of aging to evaluate the influence on astringency characteristics (astringency intensity and 16 subqualities), and colour parameters (CIE L*a*b* coordinates, total anthocyanins, pigmented polymers) after 3, 6 and 12 months. The taste, odor and aroma profiles completed the sensory evaluation of one-year aged wines.
Aglianico wine is well known to be a wine rich in tannins, and highly astringent (Rinaldi, Iturmendi, Jourdes, Teissedre & Moio, 2015). Astringency intensity of Aglianico after 12 months, decreased in a significant way with MP treatment. A positive effect of Mps in reducing astringency was also previously stated (Rinaldi, Gambuti & Moio, 2012a), probably the interaction with phenolic compounds could prevent aggregation or precipitation of tannins. The qualitative aspect of astringency was evaluated by the use of the CATA question by a jury trained for astringency subqualities as previously reported (Rinaldi & Moio, 2018). Until now the effect of Mps on the subqualitative profile of astringency in red wines has never been studied.

 

 

Figure 1. Correspondence Analysis performed on the mean of citation frequencies of the astringency subqualities included in the Check-All-That-Apply (CATA) question for Aglianico wine not treated (t=0; C-3,C-6, C-12), and aged with MS, MF, and MP mannoproteins for 3, 6, and 12 months.

In Figure 1, the correspondence analyses (CA) reveals that in tannin-rich wine as Aglianico the treatments with MP and MF were effective in reducing negative subqualities during aging (from 6 to 12 months), providing different sensory results. MP had an effect in removing the green and aggressive character of tannins making the wine silk, soft and full-bodied, while MF contributed to aroma complexity (rich and persistent) together with velvety and mouthcoating sensations.
In Sangiovese no differences in astringency were perceived after 12 months of aging. However, the effect of Mps was to reduce a strong astringency associated to sourness (green) and bitterness (hard), and to reach velvet, full-body, soft, rich and persistent sensations independently from the typology of Mps. The MF resulted the treatment that accelerated the achievement of such positive subqualities of astringency after 3 months of aging (Figure 2).

 

 

Figure 2. Correspondence Analysis performed on the mean of citation frequencies of the astringency subqualities included in the Check-All-That-Apply (CATA) question for Sangiovese wine not treated (t=0; C-3,C-6, C-12), and aged with MS, MF, and MP mannoproteins for 3, 6, and 12 months.

An aging period of 12 months with Mps affected the overall flavor profile of Aglianico depending on the commercial preparation used (Figure 3).

 

 

Figure 3. Sensory profile (-OD: odor; -AR: aroma) of Aglianico wine after 12 months of aging with MS, MF, and MP mannoproteins.

The effect of MF on taste was to reduce the sour sensation of Aglianico. This was in accordance with the proposed benefits of MF, a highly purified product with a high content of mannoproteins, that is to increase the perception of volume, roundness and length on the palate. In addition, the high protein content has been shown to be mainly related with an increase of flavor intensity, body balance and persistence (Ribeiro, Fernandes, Nunes, Filipe-Ribeiro & Cosme, 2014). All treatments in Aglianico significantly decreased the herbaceous aroma respect to control wine. The MS enhanced the floral aroma, mainly associated to violet (Cf > 20%), and together with MF enhanced the spicy one related to black pepper. As regard the odor, the black pepper was enhanced in MP treated wine while the balsamic notes increased both in MP and MF. As concern Sangiovese wine, the MP treatment was highly effective in decreasing the bitter perception, and increased the fruity aroma related to red cherry (Figure 4).

 

 

Figure 4. Sensory profile (-OD: odor; -AR: aroma) of Sangiovese wine after 12 months of aging with MS, MF, and MP mannoproteins.

The floral aroma (rose) was significantly enhanced by MP and MF. Similarly, the presence of polysaccharides in wines had showed an effect on the intensities of the floral aroma attributes (Jones, Gawel, Francis & Waters, 2008). The herbaceous odor decreased by means of all Mps, indicating that a “fining effect” was obtained on these molecules negative for appreciation.
As regard colour, at the 6th month of Aglianico aging, the treatments with MS and MF promoted significant pigmented polymers (SPP+LPP) formation respect to control. However, no significant differences were denoted between samples after 1 year of aging. Probably the mannoproteins accelerated pigmented polymers formation by favoring multiple interactions with anthocyanins and flavanols which necessitates additional six months in untreated wines. The effect on the stabilization of the coloring matter by mannoproteins was recently observed, due to an increase in anthocyanin-derived pigments (A-type vitisins and F-A+ dimers) (Alcalde-Eon et al., 2014).
In Sangiovese wine the formation of pigmented polymers was enhanced in MS-6 and MF-6, and then at 12 months by all treatments. These Mps favored the formation of pigmented polymers with anthocyanins resistant to the action of SO2 as observed by others (Del Barrio-Galán, Pérez-Magariño, Ortega-Heras, Guadalupe, & Ayestarán, 2012), thus enhancing the colour stability of Sangiovese wine.
Results were in accordance with many studies on the beneficial effect of mannoproteins on astringency, sensory properties and colour stability. An improvement of the mouthfeel sensations was obtained depending on aging period and Mps typology. Commercial mannoproteins improved the sensorial characteristics related to body and persistence of wine, while not treated wines remained astringent, hard and characterized by green tannins. Finally, mannoproteins may have a positive effect on sensory perception of red wine, reducing astringency and bitterness, and encouraging aroma revelation and odor complexity. As regard the effect on colour, commercial preparations were mostly effective on Sangiovese wine, characterized by low colorant intensity and high hue values, promoting the pigmented polymer formation, and thus contributing to a better stability of wine colour during time.

 

 

 

Alessandra Rinaldi

Alessandra Rinaldi actually is a researcher employed by Biolaffort, a research and development section of the enological society Laffort (Bordeaux, France) and detached at the University of Naples Federico II (Avellino, Italy). She received her master’s degree in Industrial Biotechnology from the University of Naples Federico II (2002) and attended the Laboratory of Enology of Bordeaux University directed by prof. Denis Dubordieu. She received the doctorat degree (funded by Biolaffort) in Science and Technology of Food-Agriculture Production from the University of Naples Federico II (2013) and attendend the Laboratory of Chemistry at ISVV (Bordeaux University) directed by prof. Pierre-Loius Teissedre. She has been working on yeast fermentation, on molecular microbiology, on wine technology, and on astringency sensation of red wines. During the last years she developped an analitical method to assess grape and wine astringency. She received a post-doctorat research bourse funded by Biolaffort on the enological potentiality of a protein extracted from potatoes for must and wine fining.

References:

Alcalde-Eon, C., García-Estévez, I., Puente, V., Rivas-Gonzalo, J. C., & Escribano-Bailón, M. T. (2014). Color stabilization of red wines. A chemical and colloidal approach. Journal of Agricultural and Food Chemistry, 62(29), 6984-6994.

Del Barrio-Galán, R., Pérez-Magariño, S., Ortega-Heras, M., Guadalupe, Z., & Ayestarán, B. (2012). Polysaccharide characterization of commercial dry yeast preparations and their effect on white and red wine composition. LWT-Food Science and Technology, 48(2), 215-223.

Jones, P. R., Gawel, R., Francis, I. L., & Waters, E. J. (2008). The influence of interactions between major white wine components on the aroma, flavour and texture of model white wine. Food Quality and Preference, 19(6), 596-607.

Pozo-Bayón, M. Á., Andújar-Ortiz, I., & Moreno-Arribas, M. V. (2009). Scientific evidences beyond the application of inactive dry yeast preparations in winemaking. Food Research International, 42(7), 754-761.

Ribeiro, T., Fernandes, C., Nunes, F. M., Filipe-Ribeiro, L., & Cosme, F. (2014). Influence of the structural features of commercial mannoproteins in white wine protein stabilization and chemical and sensory properties. Food Chemistry, 159, 47-54.

Rinaldi, A., & Moio, L. (2018). Effect of enological tannin addition on astringency subqualities and phenolic content of red wines. Journal of Sensory Studies, 33(3), e12325.

Rinaldi, A., Gambuti, A., & Moio, L. (2012a). Precipitation of salivary proteins after the interaction with wine: the effect of ethanol, pH, fructose, and mannoproteins. Journal of Food Science, 77(4), C485-C490.

Rinaldi, A., Iturmendi, N., Jourdes, M., Teissedre, P. L., & Moio, L. (2015). Transfer of tannin characteristics from grape skins or seeds to wine-like solutions and their impact on potential astringency. LWT-Food Science and Technology, 63(1), 667-676.

Posted by in Enology

Individual differences and effect of phenolic compounds in the immediate and prolonged in-mouth aroma release and retronasal aroma intensity during wine tasting

By Maria Angeles del Pozo Bayón

Phenolic compounds cover the largest fraction of the non-volatile components of wines. Flavonoids (flavonols, anthocyanins and flavan 3-ols) and non-flavonoids (phenolic acids and stilbenes) are the two major classes of wine phenolics. Among them, flavan-3-ols monomers and their oligomers and polymers, which are called proanthocyanidins or condensed tannins, are the most abundant in wine. These compounds have a large contribution to wine sensory characteristics, such as color, astringency and bitterness.
However, phenolic compounds can also affect wine aroma since they can interact with different types of aroma molecules, changing their volatility and modifying aroma release (Pozo-Bayón & Reineccius, 2009). There are many analytical studies focused on determining aroma-phenolic interactions at the molecular level. Most of these works have been conducted using -in vitro approaches (static and dynamic headspace conditions), which although very valuable in determining the chemical nature of aroma-phenolic interactions, do not represent the retronasal delivery of odorants during wine tasting.
In fact, when the wine is introduced into the oral cavity, it is submitted to oral processing. Once in the mouth, wine components (aromatic and nonaromatic compounds) and oral fluids and structures (e.g. saliva, oral mucosa) act together, determining aroma release patterns (Pozo-Bayón, Muñoz-González, & Esteban-Fernández, 2016). However, the chemical and biochemical changes of these odorant compounds during wine oral processing remain scarcely investigated.

Polyphenols might affect aroma release during wine oral processing through the formation of polyphenol-saliva proteins complexes (Mitropoulou, Hatzidimitriou, & Paraskevopoulou, 2011) modifying the transfer of aroma compounds to the exhalation flows that carry out the aromatic molecules to the olfactory receptors. The delayed aroma release from the oral/throat coatings could be behind the long lasting aroma perception (aroma persistence) closely related with wine quality. Therefore, saliva composition might affect this process.

In a recent work (Pérez-Jiménez et al. 2019) we have explore the role of phenolic compounds on oral aroma release during wine tasting, considering the individual effect and establishing whether this effect might also have consequences on aroma perception. In this study, the same rosé wine was supplemented with three types of commercial phenolic extracts. Two of them composed of rich monomers (GSEM-W) and oligomers (GSEO-W) purified fractions obtained from a grape seed extract, and the third one, a red wine extract (RWE-W) mainly composed of anthocyanins. All the wines were aromatized with a target mixture of six wine typical aroma compounds with different physicochemical properties. Oral aroma release was monitored in six volunteers by means of intra-oral SPME at two different times after wine rinsing, just after spiting off the wines (immediate aroma release) and four minutes later (prolonged aroma release). In addition, the sensory meaning of this effect was assessed using a trained panel (n=10) in the recognition and retronasal evaluation of the aromatic descriptors associated to the odorant molecules used to aromatize the wines. An overview of the work can be seen in figure 1.

 

 

Figure 1. Overview of the work.

Figure 2. PCA obtained with oral release data from all individuals at t=0.

Results showed a strong individual effect on total oral aroma release at the two sampling points (t=0 and t=4 minutes after wine expectoration). The first oral aroma monitoring could be more related to the immediate aroma release from oral mucosa, while the second one could be linked to the delayed release, or aroma persistence. These differences on aroma release can be linked to differences in saliva composition. For instance, as it is shown in the results from the principal component analysis (PCA), some aroma compounds (linalool, β-ionone and β-phenylethanol) were highly correlated with saliva total protein content and saliva flow (Figure 2). Individual #4 showed a high oral release of the above mentioned aroma compounds as compared to the rest. This could be related to his saliva composition. This individual had the highest concentration of saliva proteins (2700 µg/mL) and the lowest saliva flow (0.36 mL/min). As lower the salivary flow, lower dilution of aroma compounds and therefore, more aroma compounds will be available to be released to the exhalation flows. On the contrary, the highest saliva protein content of this individual might have affected the retention of aroma compounds, and mainly esters, by saliva proteins through noncovalent interactions has been described (Friel & Taylor, 2001).

 

 

Regarding the effect of phenolic extracts, a general decrease in aroma release after the oral exposure to wines with all phenolic extracts was observed. However this effect was dependent on individual. This happened for all six aroma compounds in individuals #5 and #6, for five compounds in the case of individual #3, and for three compounds in the case of individuals #1 and #4.This situation was very similar in the second monitoring time, in which phenolic compounds also decreased oral aroma release. An example of the effect of phenolic extracts on the oral release of ethyl hexanoate is shown in figure 3. Four minutes after spitting-off the wines, the effect of phenolic extracts was also significant for many aroma compounds, and especially for the two esters, isoamyl acetate and ethyl hexanoate.

 

 

Results from the sensory analysis confirmed that wines with phenolic extracts even at the very low dose like that used in this study (150 mg/L), exhibited significantly lower intensity for the attributes "banana" and "apple" which were associated with the compounds isoamyl acetate and ethyl hexanoate (Figure 4). These compounds were also lower oral released, confirming the good agreement between the -in vivo analytical approach using intra-oral SPME and the sensory findings, at least for these chemical odorants (ester compounds).

 

 

Figure 4. Intensity scores of the aroma descriptors determined by the trained panel (n=10) in the control wine (C-W) and in the wines supplemented with the phenolic extracts (GSEM-W, GSEO-W, RWE-W). Asterisks denote statistically significant differences from ANOVA results (p<0.05).

Figure 3. Oral release of ethyl hexanoate after mouth rinsing with the control wines and the wines spiked with phenolic extracts.

Overall, from a technological point of view this study provides new insights for the development and/or improvement of polyphenol base oenological formulations to enhance wine aroma persistence.
More information about this work can be found in the original article:
Perez-Jiménez, M., Chaya, C., & Pozo-Bayón, M. Á. (2019). Individual differences and effect of phenolic compounds in the immediate and prolonged in-mouth aroma release and retronasal aroma intensity during wine tasting. Food Chemistry. Volume 285, Pages 147-155

 

 

Maria Angeles del Pozo Bayón

Maria Angeles del Pozo Bayón is a Research Scientist at the Institute of Food Science Research (CIAL) in Madrid, which belongs to the Spanish National Research Council (CSIC). She has a graduate Degree in Biology and in Food Science and Technology. During her PhD she studied the effect of technological variables influencing important wine quality markers such as the aroma and phenolic compounds. She was granted with a Marie-Curie postdoctoral fellowship to work at the CSGA-INRA Dijon (France) in aspects related to matrix-aroma interaction and its effect on aroma release. She also was a Postdoctoral Research Associate at the Food Science and Nutrition Department in the University of Minnesota (USA), where she worked on real time aroma monitoring using PTR-MS technique. Currently she has a Tenure position at CIAL, and she is the leader of a National Project focused on investigating the effect of oral physiology on the interindividual differences on wine aroma release and aroma perception and its effect of consumer choice. Recently she has received the ENOFORUM 2018 Award “Spanish Research for Development”. She is the author of numerous publications in scientific and technical journals mainly regarding the topic of flavor chemistry.

 

References:

Friel, E., & Taylor, A. (2001). Effect of salivary components on volatile partitioning from solutions. Journal of agricultural and food chemistry, 49(8), 3898-3905.

Mitropoulou, A., Hatzidimitriou, E., & Paraskevopoulou, A. (2011). Aroma release of a model wine solution as influenced by the presence of non-volatile components. Effect of commercial tannin extracts, polysaccharides and artificial saliva. Food research international, 44(5), 1561-1570.

Perez-Jiménez, M., Chaya, C., & Pozo-Bayón, M. Á. (2019). Individual differences and effect of phenolic compounds in the immediate and prolonged in-mouth aroma release and retronasal aroma intensity during wine tasting. Food Chemistry, 285, 147-155.

Pozo-Bayón, M. Á., & Reineccius, G. (2009). Interactions between wine matrix macro-components and aroma compounds. In  Wine chemistry and biochemistry,  (pp. 417-435): Springer.

Pozo-Bayón, M. Á., Muñoz-González, C., & Esteban-Fernández, A. (2016). Wine preference and wine aroma perception. In  Wine Safety, Consumer Preference, and Human Health,  (pp. 139-162): Springer.

Posted by in Enology

Impact of high temperature on red grape flavonoids

By Julia Gouot and Celia Barril

Flavonoids are key compounds for red grape berry and wine quality. Among those, flavonols (UV protectors), anthocyanins (red pigments), flavan-3-ols and tannins (contributing to colour and mouthfeel) are affected by several abiotic factors. In particular, high temperature seems to affect their biosynthesis, accumulation and degradation. Under high temperature, a decrease in total anthocyanins is reported in most cases, while changes in anthocyanin profile, and flavonol and tannin responses are less consistent. This article provides an overview of experimental conditions impacting on flavonoids, including developmental stage, duration, intensity, nocturnal and diurnal temperature ranges, and cultivar diversity of Vitis vinifera L. and interspecific hybrids.
Flavonoids are important secondary metabolites protecting plants against biotic and abiotic stresses and derive from the precursors: phenylalanine, 3-malonyl-CoA and 4-coumaroyl-CoA. They have a common C6-C3-C6 backbone and are divided into sub-families depending on their exact structure and subsequent properties. Three of the main sub-families are flavonols, anthocyanins, and flavan-3-ols giving rise to tannins (Figure 1).

 

Figure 1. Flavonol (A), anthocyanin (B) and tannin (C) chemical structures. Substituent R1, R2 and R3 vary depending on compounds (-OH, -OCH3) (Adapted from Gouot et al, 2018).

To understand the impact of temperature on flavonoid metabolism, experimental methods are required to prevent interactions with light and water status, as they also affect flavonoid biosynthesis (Downey et al, 2006). Direct methods, which modify the fruit or whole-vine temperature involve controlled environments such as glasshouses, growth chambers/cabinets, small climatic chambers, cold rooms or more complex designs such as passive or heated set-ups in the vineyard called open-top chambers (Bonada and Sadras, 2015). Review of the literature highlighted several key parameters to consider when designing an experiment studying temperature:
Plant material. Several plant materials such as vines of different age, field grown or potted vines, grafted or non-grafted, fruiting cuttings, mutant dwarf vines (microvines) have been used. Grapevine variety must also be considered with vines grown in cool climate regions (Aki Queen, Kadainou R-1, Sangiovese and Pinot Noir) appearing more sensitive to temperature while others, well established in hot climate regions (Malbec and Shiraz), maintain their secondary metabolism under high temperature, although they are still affected by more extreme conditions.
Treatment scale. Temperature treatments can be classified into three levels: whole vine, bunch and detached berry or cell suspension (Figure 2). Whole-vine heating experiments have mainly been conducted in controlled environments or using open-top chambers in the field, often with a broader scope of studying the effect of long-term average warming or heat events on photosynthesis, vine development and subsequent changes in berry composition. Other experiments, designed to only change bunch temperature, used chamber-free systems to investigate the effect of temperature on berry metabolism independently of the canopy (Tarara et al, 2000). To complement field and controlled experiments, single berry studies have also been conducted in vitro on detached berries or cell suspension to gain a detailed understanding of flavonoid degradation mechanisms using isotope tracers.

 

 

Figure 2. Summary of the effect of high day temperature on grape flavonoids at different treatment scales: whole vine, bunch and detached berry (Adapted from Gouot et al, 2018).

Duration, intensity and timing. Two main categories depending on the duration of the treatment can be differentiated: short-term, when high temperature is applied for a few hours, or several days, up to 14 (Lecourieux et al, 2017); and long-term, when treatments are applied from several weeks to several months or for the whole season. The imposed temperatures also vary from a couple of degrees Celsius to represent future climate conditions, to a high temperature differential reproducing heat event conditions. Treatments can also be applied at different timings in relation to day and/or night.
Phenological stage. The development stage at which berries are exposed to heat stress is probably the most important parameter to consider, with responses varying depending on the phenological stage. Long-term studies have assessed the effect of a higher average temperature during the whole season: from flowering to maturity or the whole year with interruption during winter. Other studies have focussed on specific growth stages targeting gene expression at a given time of berry development and/or ripening. Early berry development experiments are rare, and most studies have commenced just before the onset of véraison or just after. Véraison, a 24-hour phase when berries begin to colour, has been identified as a particularly sensitive window for abiotic stress responses and anthocyanin biosynthesis. Late ripening experiments have shown a less pronounced effect, or none, on flavonoid profiles, but have impacted concentrations due to degradation and changes in berry water content/size due to shrivelling.
Overall, flavonols do not seem to be directly affected by high temperature but rather more indirectly impacted by a change in primary and secondary metabolism. Flavonols are intermediates in the flavonoid pathway and changes in expression of the genes shared with other flavonoids could explain why they are sometimes affected by temperature. On the other hand, anthocyanins are significantly and directly reduced under high day temperature (Figure 2). Several hypotheses suggest there is a complex combination of enzyme inhibition, up- and down-regulation of phenylpropanoid genes as well as anthocyanin degradation. To date, there is insufficient research on flavan-3-ols to conclude on a direct or indirect temperature effect, especially as very early berry development stages such as flowering have not yet been studied. Tannins have been inconsistently affected and no clear patterns have yet been identified (Cohen et al, 2008, Cohen et al, 2012a, 2012b).

 

 

Julia Gout

Julia Gout completed her education in France and graduated with a Diplome National d'Oenologue and Diplome d’Ingenieur Agronome from ENSA Toulouse. She also studied a Research Master in analytical chemistry/chemometrics at AgroParisTech. She first joined the NWGIC (National Wine and Grape Industry Centre, Charles Sturt University, Australia) to undertake her 6-month Master internship with Dr Celia Barril in 2015. In 2016, she was granted with a scholarship and started her PhD with Dr Barril on the effect of high and extreme high temperatures on Shiraz grape tannin composition.

 

Celia Barril

Dr Celia Barril is a Senior Lecturer in Chemistry at Charles Sturt University (Australia), and currently Course Director in the Faculty of Science. Celia’s research activities make use of her knowledge in organic and analytical chemistry, as applied to current issues in the food, and grape and wine industries. A key theme of her research is the use and development of analytical tools targeted to grape and wine composition, from the impact of canopy management practices and bunch microclimate on grape growing and quality to wine stability quality.

 

References:

Bonada M, Sadras VO. 2015. Review: critical appraisal of methods to investigate the effect of temperature on grapevine berry composition. Australian Journal of Grape and Wine Research 21, 1-17

Cohen SD, Tarara JM, Gambetta GA, Matthews MA, Kennedy JA. 2012a. Impact of diurnal temperature variation on grape berry development, proanthocyanidin accumulation, and the expression of flavonoid pathway genes. Journal of Experimental Botany 63, 2655-2665

Cohen SD, Tarara JM, Kennedy JA. 2008. Assessing the impact of temperature on grape phenolic metabolism. Analytica Chimica Acta 621, 57-67

Cohen SD, Tarara JM, Kennedy JA. 2012b. Diurnal temperature range compression hastens berry development and modifies flavonoid partitioning in grapes. American Journal of Enology and Viticulture 63, 112-120

Downey MO, Dokoozlian NK, Krstic MP. 2006. Cultural practice and environmental impacts on the flavonoid composition of grapes and wine: a review of recent research. American Journal of Enology and Viticulture 57, 257-268

Gouot JC, Smith JP, Holzapfel BP, Walker AR, Barril C. 2018. Grape berry flavonoids: a review of their biochemical responses to high and extreme high temperatures. Journal of Experimental Botany 70, 397-423

Lecourieux F, Kappel C, Pieri P, Charon J, Pillet J, Hilbert G, Renaud C, Gomès E, Delrot S, Lecourieux D. 2017. Dissecting the biochemical and transcriptomic effects of locally applied heat treatment on developing Cabernet Sauvignon grape berries. Frontiers in Plant Science 8, 53

Sadras VO, Bubner R, Moran MA. 2012a. A large-scale, open-top system to increase temperature in realistic vineyard conditions. Agricultural and Forest Meteorology 154–155, 187-194

Tarara JM, Ferguson JC, Spayd SE. 2000. A Chamber-Free Method of Heating and Cooling Grape Clusters in the Vineyard. American Journal of Enology and Viticulture 51, 182-188

Posted by in Viticulture