Category Archives: odor

Sep 06 NO comments
aroma, Cabernet Franc, Cabernet Sauvignon, enology, entertainment, flavor, france, fun, grapes, History, Merlot, odor, Origins, plants, Viticulture, Whos Your Daddy, wine

Who’s Your Daddy?: Merlot



"Like" The Academic Wino on Facebook by clicking here! 

Follow The Academic Wino on Twitter by clicking here! (@TheAcademicWino) 


The “Who’s Your Daddy” series takes a brief look at the parentage of grapes, in order to get a better understanding of where particular varietals come from and how they are genetically related to one another.  So far, we’ve covered: Cabernet Sauvignon, Syrah, Chardonnay, Petit Verdot, Sangiovese, Nebbiolo, Pinotage, Gamay, and Petite Sirah.  Feel free to click on any one of the varietal names to read all about their parentage.

The subject of today’s “Who’s Your Daddy” post is Merlot, which along with Cabernet Sauvignon is one of the most popular varietals in the world.

History

In relative terms, the Merlot grape has not been around very long.  Some sources indicate that the first mention of Merlot came from an official in the Bordeaux region of France in 1784, though others say it wasn’t until the 19th century that Merlot had been noted in the record books.  It has been said that this official declared Merlot some of the finest wine of its time.  Today, Merlot remains one of the five major Bordeaux varietals, and has also seen widespread plantings throughout the world, including in the United States, Chile, Australia, and many others.

In the 1950s, a severe freeze had all but wiped out the Merlot (and Malbec) grape vines in France.  French winegrowers attempted to replant the vines the next year; however those vines were subsequently destroyed by rot.  Year after year, attempts to replant the Merlot were made, only to be met with year after year of failure and ruin.  As a result of the physical and financial loss occurring year after year, the French government placed a ban on planting new Merlot vines in 1970, which was later lifted in 1975 due to increasing popularity of Merlot wines worldwide.

Rather than me telling you about the most recent history of Merlot, including its’ “death” and then it’s more recent comeback, I’ll leave it up to the clever folks at Gundlach Bundschu with this clever video:

Viticulture

Merlot is characterized by having loss grape clusters and large berries.  The name Merlot; likely derived from the word Merle which means “blackbird” in French; is likely a reference to the dark color of the grapes (or perhaps to the fact that blackbirds are known to be very fond of the juicy berries).  The Merlot grapes are a dark bluish color, and also possess relatively thin skins, which contributes to the relative softness of the wine.

Merlot grapes tend to be less hardy than other varieties, which results in greater risk of infection by molds, mildews, or rots.  While it is more able to thrive in cooler climates than Cabernet Sauvignon, it still prefers to grow in a warmer growing environment.

Merlot does best when grown in clay or limestone soils, and ripens earlier than its’ Bordeaux cousin, Cabernet Sauvignon (2 weeks earlier, roughly).  At harvest, Merlot produces higher alcohol and lower acidity than other Bordeaux varieties.  These characteristics allow Merlot to calm the stronger tannins and structure of other Bordeaux varieties such as Cabernet Sauvignon, which allows it to function as a nice blending grape for that region.  Of course, Merlot is also well known and able to function as a single varietal wine as well, though in the Bordeaux region of France and in regions where it is more difficult to grow, it is known primarily to be blended with other varietals.

Sensory Characteristics

In general, Merlot tends to be softer and fruitier than its cousin, Cabernet Sauvignon, though it does share some similar aromas and flavors.  Of course, every bottle of Merlot is going to taste slightly different, depending upon where it was grown, what vineyard management practices were employed, and what winemaking techniques were used, though there are in general some common tones that resonate throughout the Merlot world.  Some of these common aromas and flavors of Merlot are black cherry, currant, and cedar, as well as tobacco, licorice, and chocolate.  Other aromas and flavors found in Merlot wines include black raspberries and plums, as well as jam and blueberries.

So, Merlot….”Who’s your daddy?”…

Enough of this chatter about the history, viticulture, and sensory characteristics of Merlot.  Let’s get down and dirty…Who’s your daddy, Merlot?

In 2009, a group of researchers at the University of California at Davis cleared up some of the fog surrounding the Merlot parentage debate.  Using inheritance analysis of DNA markers from thousands of grape varieties, the group was able to confidently answer the question of which grapes the Merlot grape originated from.

Without further ado, I present to you the parents of Merlot:

http://www.hort.cornell.edu/reisch/grapegenetics/
Varietyphotos/cabernetfranc.large.jpg
Cabernet Franc…….



……and……
http://lescepages.free.fr/
photcep/magdeleine_noire_fr.jpg
……Magdeleine Noire des Charentes






There you have it!  This research also found several other relatives of Merlot, including Carmenére, which may be a sort of sibling of Merlot.

If you’d like to learn about the parentage of another grape variety, simply leave a comment below and I’ll see what I can dig up!  Note: there are many grape varieties with unknown parentage still, but I’ll try my best to find data that may suggest particular relationships and origins.  This type of genetic research is ongoing, so even if I can’t find information on a particular grape of your choosing today, that may change in the future!

Cheers!
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!
Aug 27 NO comments
aroma, neurology, neuroscience, odor, psychology, research, sommeliers, Wine Bloggers Conference, wine fingerprint, wine tasting

The Neuroscience of Wine Tasting: Dissecting the Intricacies of the Minds’ Eye


"Like" The Academic Wino on Facebook by clicking here!

Follow The Academic Wino on Twitter by clicking here! (@TheAcademicWino)


 Last week, I attended the annual Wine Bloggers Conference in Portland, Oregon, which you may read all about in my two part summary series here: Part I and Part II.  I wanted to take one particular experience from the conference and elaborate a little more.  Specifically, I’d like to present to you the fascinating research by Tim Gaiser on the Neuroscience of Wine Tasting and some of the interesting findings that have come out the study.

What is the purpose of this research?

http://www.anselmovineyards.com/
wp-content/uploads/wine-tasting-classes.jpg
The most important implication for this research is in the art of teaching tasting.  According to Gaiser, the challenge of teaching wine tasting to individuals is complex: 1) we have to try and present to students our own vocabulary and experiences for wine, which may or may not resonate with each individual mind; 2) each individual student has a different neurology from everyone else, as well as different memories and experiences; and 3) we have to come up with a way to find the common denominator for tasting, so that each student may more easily learn using their own personal experiences instead of using other people’s experiences that have been impressed upon them. Thus, the overall goal of the research is to improve upon the way we teach wine tasting so that the students learn in a shorter period of time and learn to utilize their own memories and experiences.

How did he do it?

In order to find this common denominator, Gaiser set out to examine the strategies/neurological connections of some of the best wine tasters around the world.  What were the individual strategies of these professional wine tasters?  How are their neurologies connected to allow them to pick out intimate details about the wine?  How can we use this information obtained from the experts to teach others how to taste?

2009 Film Session Results

In recorded tasting sessions with Tim Gaiser in 2009, with the help of Behavioral Scientist, Tim Hallbom, it was found that eye positions and patterns are critical to experienced tasters, and olfactory cues (smells) trigger a specific image memory connection to the tasters which allow them to identify a particular smell or taste from the wine. 
http://www.visualphotos.com/photo/2x3798802/
man_smelling_glass_of_red_wine_in_
off-licence_side_3043.jpg

After the film session results, Gaiser set out to repeat the 2009 Film Session experiment with several wine experts. What he found is that these positions and images are unique for every single individual taster, which means finding the common denominator for teaching purposes even more difficult.  In order to find this commonality, each experience needed to be broken down in a sort of sequence, in order to perhaps create a teachable sequence for new and training tasters.  Specifically, the experience was broken down into the following categories: language usage and patterns, eye movements and patterns, olfactory images, internal image maps, and visual constructs for calibrating the structure of the tasting experience.

What were the findings?

One interesting outcome of these tasting sessions was that not only to do individuals make different connections and have different experiences during tasting, but they also taste differently depending upon the reason for tasting.  Were they tasting for pleasure? As a buyer? As a wine reviewer? For teaching purposes?  Depending upon the reason for tasting, the individual strategies of each taster was slightly modified.

One of the first things each taster would notice prior to tasting the wine was the color.  This visual cue gives hints as to how old the wine is, possible grape varieties, and possibly the style of winemaking used.  The tasters were able to identify these characteristics by referencing internal color swatches in their memories from previously experienced/tasted wines.  Often, an internal auditory prompt (such as “what color is this?”) would initiate the image recollection process for identifying certain characteristics elicited from the wine.

Moving on to smelling the wine, Gaiser noted that all of the tasters used an extremely consistent starting eye position or pattern when smelling the wine.  Most tasters had a sort of forward and down eye position while smelling the wine, while one taster appeared to have a darting around-type eye movement position.  This starting position is the place of focus and concentration, and the position which elicits the olfactory image recollection connections in the brain.  Similar to the color, nearly all tasters experienced an auditory prompt in addition to the eye positions to get the tasting started (i.e. “what does this smell like?”).

EXERCISE

How about you?  Where is your starting eye position? 

Take a glass of wine (in a standard wine glass).  Now, simply go about your usual method for smelling the wine.  Where do you notice your eyes are? This position is imprinted in your neurology and wherever you notice your eyes are positioned is the position that elicits the olfactory connections in your brain.  For me, this position was down and slightly centered in front.  You are allowed to close your eyes if that is more comfortable, but note your eyes are still in a particular position.

Once you find this position, keep smelling the wine while moving your eyes in a different position.  Do you notice any change in the aroma?  For me, I noticed that the smell almost went away completely when I changed the position of my eyes.  What did you experience?

Eye Assessing Cues

This study of eye patterns is not new to the study of neurology, as many books and scholarly articles have presented results showing relationships between eye movements and internal memories/representations.  During the 1970s and 80s, several collaborating researchers found that eye pattern movements were associated with the activation of different parts of the brain.  These patterns are near consistent across many individuals, however, for left-handed individuals (such as myself), these patterns can be reversed.  Even if an individual recalls visual cues in a different pattern, this pattern is at the very least consistent and repeatable.  Read this article by Robert Dilts for a more detailed analysis on this research by clicking here.
Courtesy: Robert Dilts (see link above)

Olfactory Image Connections

Another interesting finding from Gaisers’ research is that all tasters represent specific aromas and flavors of the wine with internal images or words, or a combination of the two.  These images were both still or moving, depending upon the individual taster.  Also, these images varied in size, location, color and brightness.  Gaiser also found that there was a relationship between the intensity of the aroma and the structure of the image.  These images are presented in a particular sequence for each individual taster, which combine to be what is referred to as an “image map”, which was found to be unique and vary dramatically from individual to individual.

EXERCISE:

After finding your eye position, go ahead and smell the wine.  What do images do you see?  What sort of pattern do you see these images?  How about the size of the images?  Does the main characteristic of the wine present itself as a very large image? Or perhaps not large but maybe very brightly colored?  What do you see in your minds’ eye? 

For me, I only saw words, which was relatively frustrating since nearly all of the others in the room saw bright and vivid images.  I wonder if my experience was so different because I’m left-handed, or maybe I haven’t had the experiences necessary to elicit the appropriate image for the aroma of that particular wine.

Now, try changing these images.  If you see the image as large and up close, try shrinking the image by moving it further into the background.  What happens to the aroma?  Does it change?  Does the aroma become less pronounced and harder to smell?  Is the image in color?  What happens when you change this image to black and white?  How did the aroma change?

Altering Images

Interestingly, this research found that changing the images in one’s mind changed the tasters’ experience of the wine.  Related to the palate versus the nose, a stronger intensity on the palate versus the nose resulted in the image increasing in size, brightness or location.  As one would expect, a lower intensity on the palate versus the nose resulted in the image decreasing in size, brightness or location.

Structure of Wine

The structure of the wine also elicited image recollection for each individual taster.  For some tasters, a sort of ruler or other calibrating image was presented in the mind, and depending upon the structure of the wine, the focal point of the image would change.  For example, for acidity, one taster saw a 12-inch ruler with marks on it for low, medium, and high. After tasting the wine, the taster was able to focus on and point to a particular point on the ruler in order to identify the acidity of the wine.  Similar mechanisms were found for alcohol content, tannin, and finish.
Example of an image elicited for structural identification in wine tasting

How do these results help us teach others about tasting wine?

According to Gaiser, the results of this study indicate that we should teach students to identify color and age in wine using color spectrums and swatches.  We should also help students become aware of the aroma-to-image connections they already have in their mind, and to utilize these images to identify aromas and flavors in the wine.  The students should be presented with images in order to create new memories in their psyche, particularly if they’ve never experienced a particular aroma or flavor on their own.  Finally, Gaiser claims we should teach students how to taste without wine, as well as teach students to calibrate the structural elements of wine by using internal visual scales.

What are your thoughts?

What do you all think of this research?  Of course, it was not a controlled experiment, thereby the results have to be taken with a grain of salt, but regardless, I found the results very fascinating and worthy of future experimentation and research.   I think it’s a great idea to teach students to utilize their own memories and experiences when tasting the wines, and when these memories and experiences do not exists (say, if they’ve never had a fig before and the main flavor component of the wine they are tasting happens to be fig), they should be given the opportunity to create new image maps in the mind by tasting these elements outside of the wine format.

I did leave slightly frustrated, however, in that I never saw images when smelling the wine.  Gaiser noted later in a question-and-answer session that these images are moving at an extremely fast pace, so perhaps I have not yet learned to slow down these images to a point where I can see them.  I did, however, see words pop up instead of images, which perhaps may be the way my neurological connections function in this type of olfactory recollection.  He mentioned left-handers may experience things differently than right-handers, so perhaps this is another reason why I wasn’t seeing what most others were seeing.  A controlled experiment may get at these types of questions.

I am very interested in hearing what you all think of this research.  Please leave your comments below!

References

“The Neuroscience of Wine Tasting: Unlocking the Tasting Strategies of Genius”. Tim Gaiser, MS. Presentation at the Wine Bloggers Conference August 18th, 2012, Portland, Oregon.

“Eye Movements and NLP” by Robert Dilts: http://www.nlpu.com/Articles/artic14.htm Accessed August 26, 2012.

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!
Jun 26 NO comments
aroma, chemistry, Crush, dehydrated grapes, electricity, electronic nose, enology, flavor, grapes, odor, phenolics, research, sweet, volatiles, wine chemistry, wine fraud, wine quality

Using an Electronic Nose to Determine Optimum Dehydration Time of Grapes: A Novel Approach to Controlling Wine Quality



The article presented today is mainly a short test of methods, though it could have some interesting and potentially important applications in the wine world.

There are several ways to create wines with higher levels of residual sugar, one of which is the process of dehydration.  In particular, the dehydration process is a critical step in creating Andalusian sweet wines such as Pedro Ximénez wine.  The dehydration process significantly alters the chemical composition of grapes, including sugar concentration, volatile compounds, phenolic compounds, and enzyme activities.  This process of dehydration can take anywhere from 7 to 10 days, after which the grapes are pressed and the remaining must undergoes the winemaking process.

Quality of wine made from dehydrated grapes is determined by many factors, including grape variety, enzymatic activity, and the length of time allotted for dehydration.  In an attempt to further control wine quality, winemakers attempt to control the drying time of the grapes by monitoring water loss and sugar concentrations.  If the grapes are allowed to dehydrate for too long, the aromatic quality of the wine can be compromised.  Therefore, according to the authors of the study presented today, an easy tool that utilizes a sensor that can detect small metabolic changes during grape dehydration could help winemakers determine the optimal drying time for grapes based on conditions other than just sugar concentrations, which is very important for controlling wine quality for these types of wines.

http://nanoscent.files.wordpress.com/
2012/04/electronic_nose_concept.gif
One such tool that is already in use in other parts of the food industry is the Electronic Nose (E-nose).  In regards to wine, the E-nose has been used for vintage or variety determination (employed most often when trying to find counterfeit wines), quality characteristic discrimination, and identifying Brettanomyces contaminations.

The short paper presented today examined the evolution of aromatic compounds during the dehydration process of Pedro Ximénez grapes and analyzed the use of an electronic nose to determine if the tool could be a reliable mechanism for analyzing aromatic quality of wines created from these dehydrated grapes.

Methods

Pedro Ximénez grapes were randomly sampled from 15 different locations in the Montilla-Moriles region of Spain after 0, 2, 4, 6, and 9 days of drying.  Each sample contained 25kg of healthy, dried grapes and pressed in a vertical laboratory press.  Musts were clarified using centrifugation and the preserved until analysis.

Sugars (oBrix), titratable acidity, pH, and volatile compounds were measured in the wine.  Volatile compounds were measured by gas chromatography/mass spectrometry (GC-MS).

The electronic nose used was created and assembled at the University of Rome Tor Vergata.  The nose was based on an array of 8 quartz microbalances, which are electromechanical resonators with a resonance frequency that changes proportionally to that mass which is absorbed on the sensors’ surface.

Results

  • Drying after 9 days multiplied oBrix by 1.95.
  • In the first 48 hours of drying, grape dehydration reached 11.2% and diminished 7.6% over the 48 hours following.

o   Grape dehydration continued to reach 3.45% per day until the 6th day.
o   After the 6th day, dehydration continued to reach 1.5% per day and finished the process at 30.2%.
  • As the dehydration process continued, pH decreased and titratable acidity increased.

o   This is likely due to the loss of water during the drying process.
  • The loss of water and likely the cellular structural damage that occurred during the drying process resulted in a general increase of volatile compounds in the wine.

o   Most volatile compounds reached a maximum concentration when the percentage of dehydration was 18.8%.
o   The only two volatile compounds analyzed that decreased during the dehydration process were (E)-2-hexen-1-ol and (E)-2-hexanal.
o   Acetoin reached a maximum when grape dehydration was at 11.2%.
o   Hexanoic and octanoic acids reached maximums after 4 days of drying.
o   At the end of the dehydration process, the following volatiles showed increases in concentrations (likely due to the loss of water): isobutanol, isoamyl alcohol, 2-phenylethanol, benzyl alcohol, 1-pentanol, ethyl lactate, and 1,1-diethoxyethane.
  • Dehydration conditions (i.e. high temperatures) favored the formation of Maillard reaction products, which give rise to toasty aromas with notes of coffee and/or chocolate.
  • Volatiles grouped into chemical families significantly changed concentrations during the dehydration process.

o   Carbonyl compounds and carboxylic acids were lower in concentration at the end of the drying process.
o   Alcohols, esters, and acetals significantly increased by the end of the drying process and reached maximum concentrations between 18.8% and 25.7% dehydration of the grapes.
  •  Since monitoring a high number of volatile compounds is extremely difficult, cluster analysis was used to monitor similar groups of volatiles.

o   Samples taken on day 0 and 2 of drying were very similar to each other and different from the rest.
o   Samples taken on day 4 and 6 of drying were very similar to each other and different from the rest.
o   Samples taken on the last day were similar to the sample day taken right before it.
§  Results indicate that the drying process tends to homogenize the must composition.
  • At the beginning of the dehydration process, herbaceous aromas were most prominent.

o   As the drying process continued, these herbaceous aromas diminished and aromas of floral and milky became more prominent.
o   Samples displaying primarily floral and milky aromas increased when the grape dehydration was at 18.8%.
o   Samples displaying primarily toasty aromas reached a maximum 6 days into drying.
  • Historically, sugar concentrations have been measured to determine the end of the drying process.

o   This may be problematic, as while the sugars are still increasing by the last stage of dehydration, aromatic compounds are decreasing significantly by this time.
o   Optimum drying time for volatile aroma compounds maximized when grape dehydration was around 26%.
§  According to the authors, sensors could help the winemaker determine this optimum drying point for each wine, depending on the grapes and other conditions that act to alter the chemical and aromatic composition of the finished wine.
  • Based on discriminant analysis of readings taken by the E-nose, two separate phases were observed during the grape drying process.

o   All grapes under 19% dehydrated fell into one group, while grapes from the later stages of the dehydration process fell into a second group.
§  Results indicate the E-nose is able to discriminate between grapes at different stages of the dehydration process.
  • By combining both E-nose data and results obtained from the chemical analysis and running a multiple regression, the model was able to explain 99.796% of the variability in the associated with the dehydration process.

o   Multiple regression analysis showed that there is a relationship between the dehydration process of grapes and the value that is associated with dried fruit, herbaceous, floral, and milky aromas (which are highly correlated with stage in dehydration process).

Conclusions

Based on the results of this short study, the authors concluded that there is a strong relationship between data reported by the E-nose and the aromatic volatile components of the finished Pedro Ximénez wines.  Therefore, the E-nose could be used as a way to quickly and accurately measure the optimum drying time for grapes in order to produce these sweet wines with high aromatic quality. 

There wasn’t really a lot done in this study, as it was simply a validation of methodologies, however, its results could have important applications for the wine industry, particularly when it comes to determining aromatic quality of wines created from dehydrated grapes.  What other types of wines do you think this type of aromatic quality testing could be employed?  What other tests would you have liked to see performed during this study? 

I’d love to hear your thoughts on this topic!  Please feel free to leave your comments below (reminder: all unauthorized html tags will be treated as solicitations and promptly removed).

Source: Lopez de Lerma, N., Bellincontro, A., Mencarelli, F., Moreno, J., and Peinado, R.A. 2012. Use of electronic nose, validated by GC-MS, to establish the optimum off-vine dehydration time of wine grapes. Food Chemistry 130: 447-452.

DOI: 10.1016/j.foodchem.2011.07.058.



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!
Jun 14 NO comments
aroma, Australia, chemistry, consumer preference, enology, fermentation, flavor, odor, phenolics, research, Sauvignon Blanc, wine, wine chemistry, wine preference, wine quality

Altering the Chemical Profile of Sauvignon Blanc Wines to Match Consumer Preferences



Tip on reading my reviews:  If it's getting too technical for you in the methods/results, or if you don't have much time to read through everything, just read the bolded results and skip to the conclusions for a brief summary ;)


Many aromatic compounds, be they desirable or undesirable, are produced by yeasts during the fermentation process.  In Sauvignon Blanc wines, common compounds that are known to produce specific aromatic characteristics include the thiols 4-mercapto-4-methylpentan-2-one (4MMP) and 3-mercaptohexan-1-ol (3MH) and the acetate 3-mercaptohexyl acetate (3MHA).  These compounds often express characteristics of grapefruit, passionfruit and other tropical fruit.  Depending on concentration, these sensory characteristics may change; for example, at high concentrations, these compounds have been known to take on “sweaty”, box hedge, cat urine, or sulfur-like characteristics.

http://si.wsj.net/public/resources/images/
PT-AK895_TASTIN_G_20090213175737.jpg
Different yeast strains can produce different concentrations of these thiols, as well as acetates and ethyl esters, which would effectively change the sensory characteristics of the finished wine.  By inoculating with multiple yeast strains, the concentration of these thiols increase further and change the sensory characteristics of the finished wine even more.  Armed with this knowledge, winemakers have the ability to alter their techniques in the cellar in order to produce a very specific type of wine with specific desired sensory characteristics.

In regards to consumer preferences, studies have shown that the choice of yeast strain used in Sauvignon Blanc fermentation affected their preferences for the wines.  For example, one study found that most consumers enjoyed wine with an intermediate sensory profile compared to other wines in the study, and did not enjoy wines with high ester-like and fruity aromas (which were higher in thiols).  According to studies, these thiols plus 2-isobutyl-3-methoxypyrazine (IBMP) drive consumer preferences for Sauvignon Blanc wines.  IBMP is known to produce “green” characteristics in Sauvignon Blanc wines, though higher concentrations of the compound have less-than-desired aromatic effects.  Though much work has been done in this area, it is not known at what concentrations these compounds can be to produce a wine that is desirable to the market.

The goal of the study presented today aimed to determine what sensory characteristics shape consumer preferences for Sauvignon Blanc wines, and to examine the interactions between various key aromatic compounds that give rise to these different characteristics.

Methods

Aromatic compounds were added to a white base wine at different concentrations and combinations to create a 21 total samples.  The thiols added were 3MH, 3MHA, 4MMP, and IBMP were added to the base wine at both moderate and high concentrations.  Esters added were ethyl butanoate, isoamyl acetate, ethyl hexanoate, ethyl octanoate, and phenyethyl acetate.  Two enantiomers (a.k.a. configurations) of 3MH and 3MHA were also added (both R and S configurations)

The base wine used in this study was a 2009 Yalumba Classic Dry White bag-in-box wine.  The base wine had the following enological characteristics:  3.1g/L glucose + fructose, 3.26 pH, 6.5g/L titratable acidity, 0.3g/L volatile acidity, and 12.0% v/v alcohol.  96% v/v food grade ethanol was added to both the treatments samples and the control base wine in order for all samples to have the same ethanol content.  The following were measured for all samples: methoxypyrazines, acetate esters, ethyl esters, and thiols.

For the sensory analysis, 10 people were recruited (7 female, 3 male) all who had previous experience with white wine descriptive analysis research.  Individuals were selected from the local community (Adelaide, Australia) based ability to distinguish aroma and flavor in wine through difference testing, as well as smell and taste identification tests.  All individuals went through 5 training sessions, including three two-hour discussion sessions to determine wine attributes and how to use the scale, as well as two practice rating sessions before the actual experimental rating sessions began.

Wine samples were assessed during five sessions that lasted approximately 2 hours each.  Sessions occurred under sodium lighting in isolated and temperature-controlled tasting booths.  During each session, 18 samples were presented to the panel in sets of three, with rest breaks in between each sample and 15 minutes between each set of three.  Samples were presented randomly and balanced across all panelists. No samples were swallowed/consumed during the sessions.

To test consumer acceptance of the different wine samples, 7 of the 21 samples were analyzed.  Consumer acceptance testing occurred within a few weeks of the panelist sampling as described above.  Consumers were recruited by advertisements in a local newspaper as well as the Australian Wine Research Institute website.  In order to participate in the study, consumers had to be over the age of 18, regular white wine drinkers (consuming white wine at least once per week), regular white wine purchasers (between AUD$ 10-20), having no professional wine education, in good health, no allergies to any foods, and no ethical or medical reasons for not being able to consume alcohol.

Once deemed eligible to participate, each individual attended one of 12 hour long sessions.  The testing conditions were nearly identical between this session and the sensory analysis sessions described above.  7 samples were presented to participants with a three minute break between samples (with water rinsing).  Participants were asked to rate their “liking” for each sample on a conventional hedonic 9-point scale (from “dislike extremely” to “like extremely”).

There were a total of 150 participants, with 73 of them being female and 77 of them being male.  Questionnaires were also used to determine demographics of participants, as well as their wine usage and attitudes toward wine.  Wine knowledge was ranked from low to high, with those in between falling into the medium category.  Participants also ranked either liking of four different white wine styles; Riesling, Chardonnay, Australian Sauvignon Blanc, and New Zealand Sauvignon Blanc.

Results

Demographics

  •       There was a relatively equal distribution for age and gender among participants.
  •       There was a slight bias toward higher levels of education and higher household incomes among participants.
  •       75% of participants were born in Australia, while most others were born in the United Kingdom.


Sensory Descriptive Analysis

  •       7 aroma characteristics and 2 palate characteristics were significantly different among the 21 samples tested.

o   These were: overall fruit aroma, tropical, confectionary, cat urine/sweaty, fresh green, cooked green vegetal, solvent, citrus flavor, and green flavor.
  •       There was a strong, positive correlation between “fresh green” and “green flavor”.
  •       There was a strong, positive correlation between “overall fruit aroma” and “tropical”.
  •        All samples containing IBMP (methoxypyrazine) were rated highly in “green” character, and rated low in “fruit” and “confectionary” characteristics.

o   The remainder of the samples (including the base wine) had relatively low ratings for “green” characteristics.
  •       There was a positive correlation of the characteristics “solvent” and “citrus flavor”.
  •       The base wine was not rated high for any specific characteristic, though it did have relatively high ratings for “solvent” and “citrus flavor”.
  •       Samples with moderate levels of thiols (MHA: mercaptohexyl acetate; and MMP: mercapto-4-methylpentan-2-one; in particular) showed higher ratings for “overall fruit aroma”, “tropical” and “cooked green vegetal” characteristics compared with the base wine.
  •        Samples with MH (mercaptohexan-1-ol) showed higher ratings for “citrus flavor” and “tropical”, and lower ratings for “cooked green vegetal” compared with the base wine.
  •        Thiol combinations at moderate concentrations showed increased levels of “overall fruit aroma”, “tropical”, and “cooked green vegetal” compared with the base wine.

o   At higher concentrations, ratings for “cat urine/sweaty” and “cooked green vegetal” increased, while “overall fruit aroma” and “tropical” decreased, compared with thiols present at more moderate concentrations.
o   Results indicate that thiols can contribute to “green” characteristics in wine.
  •       Thiol + high concentrations of  MHA sample had the highest rating of “cat urine/sweaty” compared to high concentrations of Thiol alone, and also displayed high levels of “”overall fruit aroma” and “tropical” characteristics.
  •       Thiol + high concentrations of  MMP and Thiol + high concentrations of MH showed intermediate ratings in all characteristics and were usually lower than samples with moderate concentrations of thiols.
  •        There was a positive correlation between 3MHA concentrations and “cat urine/sweaty” characteristics.
  •       3MH and 4MMP did not contribute any specific sensory characteristics to thiols when at moderate or high concentrations.
  •        Samples with higher levels of the S-enantiomer for thiols had more dominant effects on aroma characteristics than samples with higher levels of the R-enantiomer. (Reminder: enantiomer is a fancy word for “configuration”).

o   Sensory perception changes when the ratio of S- to R- enantiomers changes.
  •       Thiol + Ester had higher ratings for “overall fruit aroma”, “tropical”, and “cooked green vegetal”, and had the highest rating for “confectionary” characteristics.
  •       Ester combinations alone (no thiols) were similar to the base wine, but had higher ratings for the “confectionary” characteristic.

o   When combined with thiols, the “confectionary” characteristic remained high.
o   When combined with high concentrations of thiols, the “confectionary” characteristic decreased significantly.
§  Results suggest thiols suppress esters when present in high concentrations.
  •       “Overall fruit aroma”, “tropical”, and “cooked green vegetal” increased with Thiols + esters at all concentrations and “cat urine/sweaty” increased with high concentrations of Thiols + esters.
  •       Thiol + IBMP and high concentrations of Thiol + IBMP showed increased in “overall fruit aroma”, “tropical”, and “cooked green vegetal”, and a decrease in “fresh green” characteristics.

o   Thiols were able to suppress dominance of IBMP-induced “green” characteristics.
  •       Holding the thiol concentration constant while doubling the concentration of IBMP resulted in significant increases of “fresh green”, “green flavor”, and “cooked green vegetal”, and decreases of “overall fruit aroma”, “tropical”, and “cat urine/sweaty”.

o   Results suggest a mutual suppression of methoxypyrazines and thiols on when another when in combination.
  •       IBMP had a greater impact on sensory profiles of wine than thiols.

o   Results suggest there is a balance between dominance of IBMP and thiols that result in very different styles of wine, depending upon the concentrations of each compound.

Consumer Acceptance

  •        Among the 7 samples tested, there were no significant differences in “liking”/consumer preferences.

o   There were trends, however, showing that samples with esters had the highest “liking” values, followed by samples with thiols, and finally the base wine and the samples with IBMP.
  •        Analysis revealed three distinct groups of consumers related to their preferences.

o   Group 1 (26% of consumers) most “liked” the base wine (high in “solvent” and “citrus flavor” characteristics) and the combination of  high Thiol levels + high IBMP levels (high in “green” character).  Thiols alone were “liked” the least.
§  Positive associations found between “liking” and “solvent”, “fresh green”, and “green flavor” characteristics.
§  Negative associations found between “liking” and “overall fruit aroma”, “tropical” and “cat urine/sweaty” characteristics.
o   Group 2 (43% of consumers) most “liked” samples containing IBMP (high in “green” character).  Added esters and the base wine were “liked” the least.
§  Positive associations found between “liking” and “fresh green”, “cooked green vegetal”, and “green flavor” characteristics.
§  Negative associations found between “liking” and “solvent” and “citrus flavor” characteristics.
o   Group 3 (31% of consumers) most “liked” samples with esters (high in “overall fruit aroma”, “tropical”, “cat urine/sweaty”, and “confectionary” characteristics). IBMP and base wine were “liked” the least.
§  Positive associations found between “liking” and “confectionary”, “overall fruit aroma”, and “tropical” characteristics.
§  Negative associations found between “liking” and “fresh green”, “cooked green vegetal”, and green flavor” characteristics.
  •       The strongest drivers of “liking” or “not liking” for all groups were “confectionary”, “cat urine/sweaty”, and green characteristics such as “fresh green” and “green flavor”.
  •       There was a strong difference between consumers that preferred “green” characteristics and consumers that preferred “fruity” characteristics.


Demographics/Consumer Preference Behavior

  •       Group 2 had equal numbers of males and females, Group 1 had more males than females, and Group 3 had more females than males.
  •       There were differences between the liking of and consumption of New Zealand Sauvignon Blancs and red wine consumption.

o   Group 2 liked New Zealand Sauvignon Blanc significantly more than Group 1.
o   Groups 2 and 3 had a larger percentage of consumers drinking three or more glasses of NZ Sauvignon Blanc per week than Group 1.
o   Group 3 consumers drank significantly less red wine per week than consumers in Group 1 or 2.
  •        Group 2 had the largest percentage of consumers with low wine knowledge, Group 3 had the largest percentage of consumers with moderate wine knowledge, and Group 1 had the largest percentage of consumers with high wine knowledge.
  •       Group 2 consumers (with lowest wine knowledge) preferred wines with “green” characteristics.
  •       Group 3 consumers (with more moderate wine knowledge) preferred wines with “fruity” characteristics.
  •        Group 1 consumers (with the highest wine knowledge) did not appreciate high “fruity” wines.


Conclusions

According to the authors, the results of this study show that there is a strong dominance of methoxypryazines in combinations with thiols, and also an enhancing effect of esters in white wine.  Specifically, thiols were able to suppress sensory effects of methoxypryazines and esters when present at high concentrations.  The sensory analysis suggest that winemakers may use methoxypyrazine levels in grapes and wine as an approximate estimation of “green” characteristics in wine, which would help create a specific type of wine with particular sensory attributes.

The authors claim that this is the first study to show the direct effects of aromatic compounds on wine quality as perceived by wine consumers.  They found that there is no one single aromatic characteristic that drives consumer preferences in regards to Sauvignon Blanc wines, and that consumer preferences are very complex.  The results clearly show that it is extremely difficult to predict consumer acceptable of Sauvignon Blanc based on any one particular characteristic alone. 

However, since the results did show that there are clear group preferences among consumers in regards to Sauvignon Blanc wines, winemakers should be able to take what has been found regarding the chemistry, sensory, and preference analyses, to create different types of Sauvignon Blanc wines that are tailor-made for any particular group of consumers.

I’d love to hear what you all think of this study!  Please feel free to comment below (Reminder: any unapproved HTML tags will be promptly removed).

Source: King, E.S., Osidacz, P., Curtin, C., Bastian, S.S., and Francis, I.L. 2011. Assessing desirable levels of sensory properties in Sauvignon Blanc wines – consumer preferences and contribution of key aroma compounds. Australian Journal of Grape and Wine Research 17: 169-180.

DOI: 10.1111/j.1755-0238.2011.00133.x




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





http://www.yfilling.com/blog/wp-content/
uploads/white_wine_and_glass.jpg
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!