Category Archives: winemaking

Sep 13 NO comments
book review, entertainment, History, literature, USA, winemaking

Book Review: The Makers of American Wine: A Record of Two Hundred Years by Thomas Pinney




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It’s been a while since I’ve posted a book review.  To be honest, I’ve been so busy that it’s taken me since the last book review until now to finish this most recent book.  To date, I’ve reviewed 4 books on this site (not including today’s book) including:



To read any of these reviews, feel free to click on the book titles and you’ll be whisked away to the appropriate post.

For today’s book review, I present to you The Makers of American Wine: A Record of Two Hundred Years by Thomas Pinney.  Though at times I found myself skimming through paragraphs quickly due to my busy schedule, overall this is a wonderful summary of the history of winemaking in the United States, and brings to light some of the “fathers” of American wine that would have been otherwise forgotten.
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Since this book encompasses the historical figures in American wine for only the last two hundred years, the trials and tribulations of winemaking in the “New World” had mostly gone unmentioned.  Save for about a sentence or two referencing Thomas Jeffersons’ attempts at growing grapes and making wine, that part of American winemaking history was largely uncovered.  Of course, the scope of this book includes those figures only within the last 200 years, however, I was hoping for a little bit more of the very early history then what was described.  I’m obviously being a little picky and bias, as I live in Charlottesville, VA, the home of Thomas Jefferson.

The aforementioned omission is one of the only qualms I had with this book, as in general it was quite a well-researched and well-written documentary of American winemaking history which captured my attention and educated me on many of the major players in the American wine industry that I wouldn’t have otherwise known about.  For those that don’t realize the American wine industry did not start in California, you need to read this book.

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Chapters 1 through 5 cover winemaking history in America pre-1900.  We first learn about John James Dufour in Chapter 1, as well as his many failures amidst a strong determination to succeed.  Next in Chapter 2, we are introduced to Nicholas Longworth, who was quite the experimenter with different vines, and who built the Cincinnati wine industry up from the ground, only for it to come crashing down soon after his death.  In Chapter 3, we meet George Husmann, who has been deemed the “father of the Missouri grape industry”, who popularized the Norton grape (among others) a very popular grape helped save the European wine industry from total destruction by the Phylloxera plight.



Chapters 4 and 5 introduce us to the first of many pioneers of the California wine industry: Charles Kohler, who according to the author “put California wines on the map”, and Andrea Sbarboro, the first of many Italians who made their name in the California wine industry.  Chapter 6 introduces us to Percy T. Morgan, and describes the formation and plan of the California Wine Association, which brought “big business” to the American wine industry for the first time in history.  Chapter 7 tells the tale of Paul Garrett, who was the “Dean of American Wine Growers” (according to Forbes magazine), and who managed to remain successful throughout the difficult Prohibition years, particularly with his “Virginia Dare” wines.

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Chapters 8 through 12 describe some of the names that many people believe are synonymous American wine history, as these names have and continue to resonate throughout the wine industry in the United States.  Quickly, these chapters describe the life and influence of Ernest and Julio Gallo, Frank Schoonmaker, Maynard Amerine, Konstantin Frank, and Robert Mondavi, all of which are well known in more recent history of American wine, and who all played important roles in shaping what American wine is today.

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The final chapter introduces a relatively new “concept”, that is women becoming winemakers in America.  Women entering the scene as winemakers in the United States are a recent phenomenon, with the first indication of change occurring when Mary Ann Graf received her bachelor’s degree in Fermentation Science (i.e. winemaking) from the Department of Viticulture and Enology at the University of California at Davis in 1965.  From then, women have been steadily gaining ground in the wine industry, with many women today enjoying the trials and tribulations of the illustrious career.  According to the author, there is still much work to be done, as by simply referring to females in the position of winemaker as “women winemaker” instead of “winemaker” indicates that men and women are not yet truly equal in the field.  This book elaborates on the story of Cathy Corison, one of which is one of the more inspiring stories I read throughout the entire book.

Overall, I found The Makers of American Wine: A Record of Two Hundred Years by Thomas Pinney a fascinating glimpse into the history of the wine industry in the United States of which was well-written and at times very captivating.  I enjoyed learning about many of the major players in the wine industry during this time, and certainly learned a thing or two about how and when the wine industry started in this country. 

This book is perfect for those who love wine and love history and I certainly recommend it for those that enjoy historical literature and are seriously into learning about wine!

You may purchase the book on Amazon by click here: The Makers of American Wine: A Record of Two Hundred Years

You may also purchase the book directly from the publisher by clicking here:  University of California Press.

If you buy it, please report back and let us know what you think!

Enjoy!
Aug 02 NO comments
agriculture, anthocyanins, chemistry, contaminants, copper, ecology, environment, flavor, grapes, irrigation, phenolics, research, Viticulture, wine chemistry, wine quality, winemaking

The Effect of Irrigation on the Chemical Composition of Grapes



Every chemical compound in grapes and in wine play some role in the life of the grape/wine, be it during physiological processes during the growth stage, or in the finished wine itself, where it may contribute to the taste and flavor of the wine or the stability of the beverage over time.  For example, anthocyanins are responsible for the color of the grape berries, and ultimately for the finished wine.  Also, flavonols, while they are colorless in the skins of grapes, they are thought to act as a sort of shield against UV radiation.  The exact composition of these compounds in grapes and wine depend on a variety of factors, including grape variety/genetics, environmental factors, and viticulture and winemaking practices.  Studies have also suggested that anthocyanin and flavonol composition is a function of grape growth and skin characteristics.

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Most research to date has focused on the phenolic composition of grapes and wine, with very little focus on the many remaining chemical compounds in the fruit and finished beverage.  Phenolics should not be the only thing considered during these research studies, as there is likely a synergistic effect between multiple compounds in the system.  Understanding of the full chemical composition of grapes and wines are important not only from a purely scientific standpoint, but also for the grape grower and winemaker due to the direct effects on fruit and wine quality.

The goals of the study presented today were to determine the effect of irrigation management (a viticultural factor that may possibly alter the chemical composition of grapes/wine) on plant yield and physiology, as well as grape berry morphological characteristics, polyphenol and metal composition.  The study also sought to determine the absence of irrigation all together could have an effect on grape quality.

Methods

The experiment was performed in 2008 in a 5 year old vineyard in Montegiordano Marina, Southern Italy.  The climatic conditions there are considered “very hot” (climatic region 5).

The experimental vineyard plot was 0.3ha, with 10 rows of spur-pruned vines trained to a permanent horizontal unilateral cordon.  Distance between vines was 2.5m with 1m between rows.  Final plant density was 4000 vines per hectare.  Rows were planted in a north-south orientation.

Half of the plants were subject to irrigation from the early stages of fruit set to veraison using water amounts equal to 100% of cultural evapotranspiration.  Specifically, this equaled 24L per plant per each irrigation event (10 total) at 5 day intervals.  The other half of the plants were not subject to irrigation.

Meteorological variables that were measured or calculated were: temperature, rainfall, and photosynthetic photon flux density.  Physiological characteristics measured or calculated were leaf-to-air vapor pressure deficit, stem water potential (in order to determine plant water status), leaf gas exchange, chlorophyll florescence, basal florescence yield in dark-adapted leaves, maximal florescence yield in dark and light conditions, maximum quantum yield of PSII photochemistry in dark-adapted leaves, and finally the effective quantum yield of PSII in light-adapted leaves.

At harvest, 30 plants per treatment were randomly selected and the following were measured/calculated: number of clusters and yield per plant, cluster weight, number of berries per cluster, total berry weight per cluster, and the number of leaves per shoot.  For each plant, 3 clusters were randomly selected.

Berries from each cluster were separated into different weight categories: 1) less than 0.60g; 2) between 0.60 and 0.90g; 3) between 0.90 and 1.25g; and 4) greater than 1.25g.  For each plant, 20 grapes per weight class were randomly selected to measure/calculate berry fresh weight, berry diameter at the “equator”, and berry diameter at the “poles”.  The following characteristics were calculated for the berries: surface, volume, surface/volume ratio, the ratio of berry surface/berry weight, and the ratio of skin weight/berry weight.  Skin thickness and soluble solid content of berries was also measured.

For anthocyanin and flavonol extraction and analysis, three clusters per plant were randomly selected and berries separated into the aforementioned weight categories.  Anthocyanins and flavonols were measured, as well as levels of iron, copper, zinc, and calcium.

Results

(Note: I’m leaving out many exact details about values due to space limitations, but if you need to know exact numbers/values of any item presented in the results, just ask and I’ll see if those details are available and will let you know).

  • The growing season was marked with high temperatures and low rainfall.

o   Max temperatures ranged between 15.3 and 38.5oC.
o   Min temperatures ranged from 12.3 and 29.1oC.
o   Rainfall during the experimental growing season was a very low 21.9mm.
  •  There were no significant differences between irrigated and not irrigated plants in regards to net photosynthesis.
  • There were no significant differences in transpiration values between either of the treatments.
  • There were no significant differences in stomatal conductance between either of the treatments.
  • Maximum quantum yield of photosystem II and actual quantum yield of PSII reaction centers in leaves were not affected by irrigation treatment.
  • Mean numbers of clusters per plant were not different between treatment groups.
  • Yield per plant, cluster weight, and total berry weight were significantly different between treatment groups, with higher values occurring in the irrigation group.

o   Irrigation significantly increased the frequency of grapes with greater than 1.25g mass and reduced the frequency of grapes with less than 0.6g mass.
  • Irrigation treatment significantly affected berry fresh weight and skin fresh weight.

o   Irrigation significantly affected berry surface/volume ratios, and were significantly higher in irrigated plants.
o   Skin fresh weights were higher in non-irrigated plants, which resulted in a decrease in skin specific surface and increased in skin specific weight.
o   For the two intermediate weight categories, there were significant differences between the two treatment groups were noted for seed weight per berry as a result in the differences between seed number per berry.
§  There were more seeds in non-irrigated plants than in the irrigated treatment group.
  •  Soluble solid content was significantly higher in the non-irrigated group than the irrigated group.
  • Total anthocyanins were significantly higher in the non-irrigation group than the irrigation group.

o   This result was positively correlated with berry weight.
  • Significant differences were found in the concentrations of petunidin-3-O-acetylglucoside, peonidin-3-O-acteylglucoside, and petunidin-(6-O-caffeoyl)glucoside.

o   Levels were higher in non-irrigated plants (9x, 18x, and 10x, respectively).
  • Levels of single anthocyanins increased with decreasing berry weight.
  • Berries from irrigated plants had significantly lower ratios of acetylated anthocyanins/coumaroylated anthocyanins.
  • Total flavonols were not significantly different between the two treatment groups.

o   Levels of single flavonols were significantly higher in heavier berries.
  • Iron, copper, and zinc levels were significantly higher in berries from irrigated plants than from non-irrigated plants.
  • Calcium levels were not significantly different between the two treatment groups.
  • Metal levels significantly decreased in increasing berry weight.
  • There were no differences in berry skin thickness between either treatment group.
  •  No significant differences were found in the number of skin layers and thickness of the berries between either treatment group.


Conclusions

One undesired outcome of this experiment was the near drought-like conditions of the weather during the experiment.  This resulted in plants being subject to moderate-severe water stress, which caused some leaf necrosis and can influence the micro-climate at the cluster.  Specifically, it has been shown that this type of stress may affect berry size and chemical composition, thereby potentially changing the outcomes of some of the tests, and making it generally more difficult to tease out cause and effect.

The results of this study also showed that total anthocyanins were higher in grapes from non-irrigated plants than in irrigated plants.  This results in a positive influence on the long-term color stability of wines, as these compounds working in concert with tannins and flavonols to strengthen color stability in the aging beverage.  Additionally, increases in these compounds and well as the observed increases in petunidin-3-O-acetylglucoside and peonidin-3-O-acteylglucoside, can have positive sensory benefits to the finished wine as well.

Another interesting result from this study is that metal levels significantly decreased with increasing berry weight.  Excess metal concentrations in wine are known to cause negative sensory characteristics, delay the fermentation process, and increase instability.  Fe, Cu, and Zn were all found to be significantly lower in grapes from non-irrigated plants than in irrigated plants.

Overall, the results of this study suggest that less irrigation increased the quality of the finished wine.  Specifically, little to no irrigation results in lower berry yield and a reduction in berry size without negatively affecting grape quality in terms of the chemical composition of the grapes.  This study confirms what many in the wine industry in that grapes grown under water stress conditions can result in higher quality wine (provided there are no set-backs during the winemaking process).  Even though many already knew less water is better, this study paints a good picture of exactly how the chemical composition of the grapes changes when subject to these drier conditions.

There are many more results to this study that I did not cover due to time and space considerations, but I’d love to hear your thoughts or questions on them, even if I didn’t specifically cover it.  What do you all think of the study?  What would you like to have seen done differently (if anything).  I, for one, would have liked to see them create experimental wines from these two treatment groups and measure the same compounds to see how irrigation actually alters the chemical composition of the finished wine and not just the starting point grapes.  Do these differences carry through the winemaking process?  Are different winemaking techniques better suited to maintaining the original/similar chemical composition of the grapes?

I’d love to hear what you think! Please feel free to comment below!

Source: Sofo, A., Nuzzo, V., Tataranni, G., Manfra, M., De Nisco, M., and Scopa, A. 2012. Berry morphology and composition in irrigated and non-irrigated grapevine (Vitis vinifera L.). Journal of Plant Physiology 169: 1023-1031.

DOI: 10.1016/j.plph.2012.03.007



I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!
Apr 24 NO comments
antioxidants, aroma, ecology, environment, flavor, oak barrel, oak chips, phenolics, plants, research, soil, Spain, Spanish oak, storage, wine chemistry, winemaking

Influence of Geographical Location on Volatile Composition of Spanish Oak



The use of oak in wine making, be it with oak barrels or oak chips, has a significant effect on the flavor, aroma, texture, and color of the finished wine.  Traditionally, three different species of oak have been used for wine barrel fermentation and/or aging: Quercus alba L. (American oak), Quercus petraea (Matt.) Liebl., and Quercus robur L (both French oak). As a result of overcropping of the oak trees, or the harvesting off more oak trees than can be regrown for future use, in addition to the quest for more variety, new sources of oak for wine making are being explored.  Oak from Eastern European countries such as Ukraine, Russia, Romania and Hungry are starting to be used more in wine making, including similar species as used in France (Q. petraea and Q. robur) and another species used less frequently: Q. pyrenaica, which frequently hails from Spain.

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The use of oak barrels in wine making significantly influences the volatile composition of the finished wine, which in turn affects the flavor, aroma, and taste of the wine.  Studies have shown that there are quantitative differences in the volatile composition of wine made from American versus French oak barrels.  Furthermore, studies have shown that the Spanish oak, Q. pyrenaica, also shows significant differences in volatile composition of the wood, including higher levels of eugenol, guaiacol, and other volatile phenols and furanic aldehydes.  Looking at phenolic aldehydes and ketones, Spanish oak appears to retain levels between that of French and American oak. 

The amounts of these volatile compounds that are extractable from the oak wood are extremely important in determining the overall aromatic profile of the finished wine.  As a result of this, understanding the chemical composition of Spanish oak (Q. pyrenaica) is extremely important.  Studies from other oak species have shown that there is strong variability in the volatile composition of oak wood within the same species, tree, forest, stand, etc, due to various environmental and geographical factors. 

The study presented today aimed to add to the literature of oak wood volatile composition by examining Spanish oak, Q. pyrenaica, and to evaluate the effect geographical location, site, and silvicultural parameters had on them.

Methods

The sample set included 107 samples of Q. pyrenaica that were collected from several stands in three geographical locations in the northwestern Iberian peninsula (from the provinces of Ourense, Lugo, and Pontevedra).

From each tree, disks of wood were collected at a height of 1.3m above the ground.

From each of these disks, test tubes of heartwood were taken (20mm x 20mm x 40mm).

Heartwood samples were dried, then ground with a mechanical mill and sieved (<1mm) in order to obtain sawdust of a homogenous size.

Volatile compounds were isolated and then analyzed using gas chromatography and mass spectrometry. 

Results

  •       The qualitative profile of volatile compounds obtained from Spanish oak was very similar to what has been reported for other oak species.
  •       There was high variability on several levels, including the levels of individual trees, forests, and geographical locations.
  •       Q. pyrenaica samples were high in cis- and trans-β-methyl-γ-octalactone (cis- was the dominant form).
  •        Samples were high in phenolic aldehydes, including vanillin, syringaldehyde, coniferaldehyde and sinapaldehyde.
  •       Eugenol and isoeugenol were the major phenolic compounds found in all Spanish oak samples.
  •       Phenolic compounds also found in all Spanish oak samples were α-terpinol, γ-cadinene, δ-cadinene, 3-oxo-α-ionol, and vomifoliol (fruity and floral aromas).
  •       The most common semi-volatile present in the samples was β-sitosterol (antioxidant properties).


Silvicultural Parameters

  •       The most influential silvicultural parameter on volatile composition of oak samples was altitude.

o   The volatiles that were most affected were α-terpineol, eugenol, and vitamin E.
o   All correlations were negative:  the higher the altitude, the lower the concentration of volatile compounds.
  •       Organic matter and average annual temperature had some influence on volatile composition, specifically α-terpineol, vanillin, oxo-α-ionol, vitamin E, and α-amyrin.
  •       Distance from tree center, average annual precipitation, and number of trees per hectare did not influence the volatile composition of wood.


Soil Composition

  •       Volatile composition of oak in different soil types was similar.

o   Significant differences were found for the volatile aldehydes syringaldehyde, sinapaldehyde, and coniferaldehyde; and for tritperpenic compounds such as β-amyrin and derivatives and β-sitosterol (all with antioxidant properties).
o   For those compounds with important sensory influence, significant differences were found with α-terpineol, and 3-oxo-α-ionol (floral notes), and trans-β-methyl-γ-octalactone (coconut/woody notes).
  •       The greatest difference for all the above compounds were found in loamy soils.

o   Samples grown in loamy soils had the lowest levels of all of the above volatile compounds.

Geographical Location

  •       Samples from Lugo and Pontevedra were very similar.
  •       Samples from Ourense had lower levels of many volatile compounds compared to the other two locations.

o   Significant differences were found for guaiacol and vinyl guaiacol (smoky odor), syringol, eugenol (clove aroma), α-terpineol (floral odor), and coniferaldehyde.
  •       According to linear discriminate analysis, different geographical locations could determine/distinguish different chemical composition of wood samples of the same species.


Conclusions

The results of this study showed that some silvicultural parameters, such as altitude, organic matter and average annual temperature influence the volatile composition of Spanish oak, Q. pyrenaica.  Conversely, other silvicultural parameters, such as distance from tree center, average annual precipitation, and number of trees per hectare do not influence volatile composition.

Even though it was shown that Q. pyrenaica grown in loamy soils show some significant differences in regards to volatile composition compared to other soil types, linear discriminate analysis showed that soil type is a poor determinant in volatile composition of wood in Spanish oak. On the other hand, as with French and American oak, geographical location does have a significant influence on oak volatile composition, and is a good factor for volatile composition classification.

The results of this study should arm wine makers with information they need in order to make a decision on whether or not Spanish oak is right for the style of wine they wish to create, and which forest/province they should harvest the trees from.  Ultimately, however, I think the next step in this line of research would be to create a wine using barrels from Spanish oak from different geographical locations, and compare the oak volatile composition results with the finished wine volatile content as well as a sensory analysis.

What do you all think of this topic?  How many of you use Spanish oak barrels or Spanish oak chips in your wine making practice?  Please feel free to leave your comments below (no html tags, please).

Source: Alañón, M.E., Pérez-Coello, M.S., Díaz-Maroto, I.J., Martín-Alvarez, P.J., Vila-Lameiro, P., and Díaz-Maroto, M.C. 2011. Influence of geographical location, site and silvicultural parameters, on volatile composition of Quercus pyrenaica Willd. wood used in wine aging. Forest Ecology and Management 262: 124-130.

DOI: 10.1016/j.foreco.2011.03.011



I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!
Mar 27 NO comments
allergy, aroma, casein, chemistry, egg protein, enology, fining agents, flavor, Louriero, odor, phenolics, research, Trajadura, white blend, wine chemistry, wine quality, winemaking

Alternatives to Casein as Non-Allergenic Fining Agents for White Wine





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Fining agents are extremely common in the wine industry, and are used to clarify wine, control browning caused by oxidation, and improve overall stability of the finished wine.  Animal proteins have often been used, however, with recent knowledge that contaminated animal proteins can cause severe health problems in humans; fining agents of vegetable or other origin have been considered.  Aside from possible contamination, allergic reaction risk in humans is another reason why the wine industry is considering other alternatives for fining agents of wine.  One of the most common fining agents of animal origin is casein, which is derived from milk proteins.  Potassium caseinate, which is derived from casein by dissolving it in aqueous potassium hydroxide, is more often used in wine production than casein itself, due to its higher solubility in wine.

These fining agents of animal protein origin are used quite frequently in the wine industry.  For example, in France (as of 2007), 2060 million liters of wine per year were fined with casein, which equates to approximately 41% of French wines.  Similarly, up to 20% of German wines are fined with casein (again, as of 2007).

One potential alternative to casein as a fining agent in wine is polyvinylpolypyrrolidone (PVPP), a synthetic water-soluble polymer, which is known to effectively remove phenols from wine via adsorption.  It is suggested that PVPP could be used either by itself, or combined with lower levels of casein to reduce the oxidation potential of wines.  PVPP works to remove phenols from wine by hydrogen bonding between the carbonyl group on the PVPP molecule and the hydroxyl groups on the phenolic compounds.  Casein fines wine by directly inhibiting the oxidation of polyphenols into quinones by formation of casein-quinone conjugates.  Since PVPP has been shown to effectively remove phenols from wine, it could be a potentially non-allergenic alternative to casein for wine fining.  On the down side, PVPP tends to be much more expensive, though it is at least more effective at lower concentrations.

Another possible alternative to casein as a wine fining agent is commercial pea protein, a non genetically-modified protein that is currently used in vegan wine production.  It is a non-allergenic protein, and studies have found that it does not leave significant residues behind in either red or white wines. 

Studies investigating alternatives to casein as a wine fining agent are not common.  The goal of the study presented today was to evaluate the potential of a selection of allergen-free fining agents (pea protein and PVPP) as alternatives to casein (specifically, potassium caseinate). 

Methods

Wine used for this study was a white blend (2007 vintage) of 60% Trajadura and 40% Loureiro from the Vinho Verde region (north of Portugal).  The chemical profile of the wine was as following:  alcohol content was 90.7g/L, titratable acidity was 7.0g/L as tartaric acid, volatile acidity was 0.18g/L as acetic acid, the pH was 3.37, free sulfur dioxide was 44mg/L, and total sulfur dioxide was 128mg/L.

Experiment 1:  Individual fining agents and a commercial formulation of fining agents was added to the experimental wine at laboratory and semi-industrial scales.  Individual fining agents included potassium caseinate at 0.4g/L, pea protein at 0.4g/L, and PVPP at 0.25g/L.  The commercial formulation of fining agents was composed of pea protein and PVPP at a ratio of 0.25g/L pea protein: PVPP.  This experiment was performed to compare the effects of fining agent alternatives to potassium caseinate.

Experiment 2:  This experiment was performed at a laboratory scale using four commercial formulations of fining agents:  1) bentonite and potassium caseinate (0.65g/L); 2) bentonite and pea protein (0.65g/L); 3) bentonite, PVPP, and potassium caseinate (0.55g/L); and 4) bentonite, PVPP, and pea protein (0.55g/L).  This experiment was performed to determine if caseinate could be replaced by pea protein in commercial formulations.

Both experiments were performed in 1000mL flasks for the laboratory scale, and 500L tanks for the semi-industrial scale.  A no fining agent wine was used as the control.  Fining agents were thoroughly mixed into the wine, and allowed to remain in contact with it for 7 days at 20oC.  After this time, samples were centrifuged before analysis.  All samples were run in duplicate.

The following chemical characteristics were measured for each wine treatment sample: phenolic content (both flavonoid and non-flavonoid), polyphenolic content, turbidity, browning potential, color, alcohol content, pH, titratable acidity, volatile acidity, free sulfur dioxide, and total sulfur dioxide.

A sensory analysis was performed by a trained panel with “extensive” wine experience.  Wines were sampled at three different sessions; two for the laboratory scale samples, and one for the semi-industrial scale samples.  Samples were presented in a randomized fashion, and were not identified to the panelist as any particular treatment.  Panelists were asked to score on a 5-point intensity scale 15 different attributes: visual (limpidity, ton and color intensity), aroma (limpidity, intensity, finesse, harmony and vegetable), and taste (flavor limpidity, flavor intensity, body, flavor harmony, persistence, mouth end and vegetable flavor).  A total score was calculated by taking the average of the visual, aroma, and taste scores.   All sessions occurred between 10am and 12noon in individual booths following standardized protocols.

Results

Phenols

  •       Most of the fining agents significantly decreased the levels of total phenols in the sample wines, with the exception of pea protein/PVPP formulation.
  •       The fining agents had a greater influence of the flavonoid phenols than any other phenol.
  •       The results from the semi-industrial scale were statistically similar to the results from the laboratory scale.
  •       Alternative fining agents had a greater effect on non-flavonoid phenols than traditional fining agents, however all agents significantly reduced all measured types of phenols.


Color

  •       Samples including potassium caseinate (either alone or in a commercial formulation) were most effective at reducing the browning potential of the wine, which would ultimately lead to a more stable wine. 
  •       Wine color was significantly reduced by all fining agents.
  •       Clarification capacity was higher for pea protein, followed by formulations with PVPP or bentonite.
  •       PVPP was not effective in increasing clarity in either experiment.

o   This suggests that perhaps the sedimentation of PVPP powder particles may be difficult by gravity alone.
  •       After adding PVPP, lightness values were unchanged.

o   This suggests no clarifying action on the part of PVPP.
  •       Yellowness values decreased for all fining agents.

o   The greatest decrease in yellowness was for wines fined with potassium caseinate.
  •       Chroma (yellowness and redness) decreased significantly for pea protein, potassium caseinate, and formulations of pea protein and PVPP.
  •       Hue-angle values increased for pea protein, potassium caseinate, PVPP, and formulations with pea protein and PVPP.

o   This suggests that some yellow pigments may have been removed.
  •       Color variation (the geometric mean of lightness, redness, and yellowness) was greatest for potassium caseinate and pea protein, followed by formulations of pea protein with PVPP and pea protein with bentonite.


Sensory Analysis

  •       There were no sensory differences between any of the treatment sample wines.

o   These results suggest the addition of pea protein or other alternatives to casein has no sensory impact on the finished wines.

Conclusions

According to the results of this study, potassium caseinate, pea protein, and PVPP all decreased the concentrations of phenols in the finished wine.  It was also found that only potassium caseinate, the animal protein most often used in winemaking, was effective at reducing browning potential of the wine.  Finally, there were no sensory differences between the wines produced from all of the tested fining agents.

The authors of this study suggest that these results using pea protein as an allergy-free alternative to casein as a wine fining agent is a real possibility, though more research would most certainly need to be completed.  Pea protein was not as effective as casein in regards to reducing oxidation potential; though using pea protein in a formulation with more effective fining agents would be an acceptable alternative to animal protein-based agents alone.

I’d love to hear what you all think about this topic!  Feel free to comment below (any HTML tags will be deleted).

Source: Cosme, F., Capão, I., Filipe-Ribeiro, L., Bennett, R.N., and Mendes-Faia, A. 2012. Evaluating potential alternatives to potassium caseinate for white wine fining: Effects on physiochemical and sensory characteristics. LWT-Food Science and Technology 46: 382-387.

DOI: 10.1016/j.lwt.2011.12.016




I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!
Mar 07 NO comments
bacteria, chemistry, contaminants, enology, flavor, new, odor, phenolics, research, S. cereviase, spoilage, wine chemistry, wine quality, winemaking, yeast

Using Ultrasound Technology to Combat Wine Spoilage: A Novel Approach



Many types of bacteria and yeasts are relied upon in the winemaking process.  However, sometimes these organisms can cause the resulting wine to spoil.  Often, this spoilage results in undesirable textures as well as off odors or flavors in the finished wine, including bitterness, too much buttery character, and excessive volatile acidity.

Acetobacter pasteurianus http://bacmap.wishartlab.com/system/images/
966/medium/Acetobacter_pasteurianus.jpg?1319706510
Winemakers often combat these issues conventionally by adding antimicrobials such as sulfur dioxide or dimethyl dicarbonate, pasteurization, or by physically removing the organisms by filtration methods.  These methods may not always be completely effective, and sometimes results in other off-flavors in the finished wine.

In other aspects of the food industry, ultrasound is often used for the treatment of microbial spoilage.  It is because of this, the authors of the study presented today suggested that perhaps the technology could also be used in treating microbial spoilage in wine.

How this ultrasound technique works is that high power ultrasound waves pass through a liquid (potentially wine) causing small bubbles to form and pop (a.k.a. cavitation).  This cavitation process creates localized areas of high temperatures and pressures, as well as the formation of hydroxyl radicals.  These conditions of high temperature and pressure can cause breakdowns in microbial cell walls, rendering the organisms more susceptible to the hydroxyl radicals, which ultimately destroy them. 

Perhaps by applying these ultrasound waves to wine at some point during the winemaking process, spoilage-causing microbes could be destroyed without causing ill effects on the wine.  The study presented today set out to research just that very idea.

Methods

The microbes chosen for this study were representative strains of bacteria and yeasts that are commonly associated with spoilage in wine.

The grape juice used in the study was a Semillon from the 2008 vintage.  The finished red wine used in the study was produced in 2007 at the Hickinbotham Roseworthy Wine Science Laboratory at the University of Adelaide.  Yeast and bacteria cells were cultured and then inoculated into saline solution (control), sterile grape juice, or sterile red wine.  If you’d like to know more details about the culture methodology, just ask.

High power ultrasound was performed using a titanium alloy radial probe.  The different media (grape juice or red wine) was kept in an ice bath to maintain a temperature of 23oC during the high power ultrasound irradiation.  During ultrasound exposure, cultures were exposed for 2 minutes followed by a 2 minute rest.  This cycle was repeated for up to 40 minutes, for a total ultrasound exposure time of 20 minutes.

Viability of bacteria and yeasts were calculated for each media.  In a nutshell, 0% viability indicates that all cells are dead, whereas 100% viability means that all cells are healthy and alive.

Ultrasound-treated wines were tested for sensory impact by 31 participants (unclear who they were) who were asked to pick the wine with the same flavor and aroma as a reference that did not undergo ultrasound treatment.

Results

Yeasts

  •       Decreases in viability following ultrasound treatments occurred for all yeast strains, though some yeasts were more susceptible than others.
  •       Saccharomyces cerevisiae viability decreased to 20% in the saline control, and decreased only to 75% in the grape juice.
  •       Schizosaccharomyces pombe viability decreased to 20% in the saline control, and decreased only to 75% in the grape juice.
  •       Z. bailii viability initially increased after ultrasound exposure, but after 20 minutes decreased by 15% in wine, and 50% in grape juice.

o   This initial viability increase may be due to the fact that Z. bailii grows in clusters, creating the illusion of increased viability when the individual cells were shaken away by the ultrasound waves from the cluster group.
  •       Yeasts least affected by the ultrasound treatment were Hanseniaspora uvarum (47% viability loss) and Dekkera bruxellensis (43% viability loss).
  •       The control for yeasts (no ultrasound treatment) did not show any increase or decrease in viability over the entire 40 minute incubation period.


Bacteria

  •       The control for bacteria (no ultrasound treatment did not show any increase or decrease in viability over the entire 40 minute incubation period.
  •       Viability of A. aceti in grape juice was 82%, but dropped to 40% in the saline control medium.  A. aceti did not grow at all in the wine medium, so viability could not be tested.
  •       Acetobacter pasteurianus viability decreased to 12.8% in saline, 24.4% in red wine, and remained around 74% in juice.
  •       Oenococcus oeni viability decreased by around 25-35% in all media.
  •       Pediococcus sp. showed 45% viability in wine, 75% viability in grape juice, and 100% viability in the saline control.
  •       Lactobacillus plantarum viability remained between 75% and 100% for all media.


Sensory Analysis

  •       There were significant sensory differences between wines treated with high power ultrasound and untreated control wines.


Conclusions

It appears from the results of this study that some yeasts and bacteria were more affected than others during the high power ultrasound treatments.  The most greatly affected yeast was S. cerevisiae, while the greatest affected bacteria was A. pasteuranus.  According to the authors, the variability in the effectiveness of ultrasound on yeast and bacteria viability could be a result of differing configurations of cell walls between the different species.  For bacteria, some species have a thicker cell wall (gram-positive), thereby possibly making them more resistant to the physical damage caused by ultrasound treatment compared to bacteria with thinner cell walls (gram-negative).

The medium used also greatly affected the ability of the ultrasound to decrease viability of the yeasts and bacteria.  According to the authors, this could be a result of the viscosity, vapor pressure, and surface tension of the different media, as all of these things alter cavitation efficiency in liquid media. 

In regards to sensory changes, it is clear from this study that ultrasound treatment significantly altered the flavor/aroma of the wine.  The authors speculated that this may be due to the increase in free radicals as a result of the cavitation process of ultrasound treatments.   Since they do not know for sure what exactly caused this different in sensory characteristics, more research needs to be done.  The authors bring up the concept of “bottle shock”, in that perhaps this change in sensory characteristics is only temporary, and needs to undergo a rest period before consumption.  Again, this idea would need testing to confirm or refute it.

High power ultrasound technology may be a way to control different types of wine spoilage microorganisms, however, a lot more work needs to be done to determine exactly when in the winemaking process is ideal for treatment, as well as exactly which microorganisms the treatment would be used to treat against.  This study touches briefly on these questions, but much more research needs to be done for a better understanding of the mechanisms involved.

Also, since the ultrasound treatment significantly altered the sensory characteristics of the wine, a lot more research needs to be done to try and optimize the procedure so that spoilage is maximally decreased while sensory characteristics remain unchanged (if that’s even possible).  This study did not go into exactly how the flavor and aroma of the wine was just, just that it was different.  More detailed sensory analysis should be conducted, in order to get a greater understanding of how this technology affects these characteristics.

Overall, I think the moral of the story is that ultrasound technologies could potentially be a treatment for preventing wine spoilage; however, there is a significant amount of research that needs to be done in order to optimize the system without resulting in any negative impacts on wine sensory characteristics.

What do you think about using ultrasound technology for combating wine spoilage?  Do you think these initial results warrant further research?  Or should they just toss the idea in the trash?  Please leave your comments below! (no html tags, please).

Source: Luo, H., Schmid, F., Grbin, P.R., and Jiranek, V. 2012. Viability of common wine spoilage organisms after exposure to high power ultrasonics. Ultrasonics Sonochemistry 19: 415-420.

DOI: 10.1016/j.ultsonch.2011.06.009





I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!