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Examining the Influence of Cherry Wood Barrel Aging on Red Wine Color

Rebecca Yeamans — Tue, 11 Sep 2012 10:30:02 +0000

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Oak aging is a very common practice in winemaking, particularly in wines destined for a higher quality designation. In general, with oak aging (and other wood aging, for that matter), the contact between the wine and the wood promotes an influx of compounds into the wine which often has a positive influence on the complexity of the wine, as well as the intensity of the nose and palate. Even more important, the small pores within the wood influence the rate of oxygen diffusion into the aging wine, with has a significant effect on color stabilization, as well as the phenolic composition of the finished beverage.

http://upload.wikimedia.org/wikipedia/commons/
f/f0/Large_botti_size_oak_barrels_in_Chianti.jpg

Color

Let’s focus on color for a bit (or, well, for the remainder of this post). The color of wine can tell you many things, including its age, how it may have been stored, and also its potential overall quality. Color in wine comes primarily from its anthocyanin content, which originates from the skins of grapes. In red wine, the skins of the grapes remain in contact with the must (unfermented wine) for a period of time, which is known as maceration, which extracts more and more anthocyanins (among a barrage of other compounds) the longer the skins sit with the juice.

Once these anthocyanins are extracted from the skins into the grape must, their concentrations decrease over time due to several chemical reactions, including polymerization, oxidation, precipitation, as well as absorption by yeast. Some of the by-products of these chemical reactions between anthocyanins and other compounds in the wine can provide a greater resistance to bisulphite bleaching and pH changes, which is important in regards to the sensory characteristics of the finished wine.

What does wood aging and color have to do with one another?

As I mentioned just previously, anthocyanins can react with other compounds in the wine, which can alter color, in addition to other quality factors in the beverage. Since aging in wood barrels ads an influx of wood-related compounds into the wine, these can interact with anthocyanins and ultimately change the color and overall quality of the finished wine.

What type of wood are you talking about, anyway?

To date, most of the studies examining the influence of wood aging on wine have focused on French and American oak barrels, which are undoubtedly the two most common types of wood used in this type of aging. These types of barrels have been used for generations, and are the traditional woods of choice when aging wine or other distilled beverages. However, more and more alternatives to the traditional French and American oak barrels are being used, partly for variety, but more importantly for cost-savings. These alternatives include chestnut, acacia, cherry, and ash (to name a few); all of which cost markedly less than traditional French or American oak barrels, and also give unique sensory characteristics to the finished wine which are becoming more desirable among consumers.

http://thephotogardenbee.com/wp-content/uploads/
2010/01/Weeping-Cherry-Tree-by-Allan-Bruce-Zee.jpg

Cherry wood, in particular, has been found to contribute to the complexity of wine, by significantly increasing the cherry and red fruit notes to the wine, as well as increase the overall acceptance of the wine. Studies have shown that cherry wood promotes a more oxidative environment for the wine, which suggests a shorter aging period lest one be left with a wine that suffers from too much oxygen exposure (which is not good!).

The study published last year in the Journal of Agricultural and Food Chemistry, the results of which I will present shortly, aimed to take this known information regarding cherry wood aging and anthocyanins and examined the impact of cherry wood aging on the oxidative changes of color and pigment in red wines. In a nutshell, they wanted to know how does cherry wood aging affect the color of the red wine, and how does it compare to red wine aged in more traditional French oak barrels?

How did they do it?

The red wine used for this study was 80% Sangiovese and 20% Merlot from the 2008 vintage by Marchesi de Frescobaldi in Tuscany, Italy (Sieci, to be more specific). Wines followed a traditional vinification protocol, including 20 days of maceration (skin contact with must). After alcoholic fermentation, the wines underwent spontaneous malolactic fermentation.

The barrels used were two 225L medium toasted barriques of French oak and cherry wood, as well as a larger 1000L cask made of cherry wood with light toasting. All aging conditions were performed in triplicate. Barriques and casks were made with staves that had been seasoned for 24 months. A 1000L stainless steel tank was used as a control.

An aging length of 4 months was chosen, due to the nature of the experiment. This experiment was testing anthocyanin changes over time, so the experiment was carried out long enough so that the total anthocyanins would significantly decrease or disappear all together. This magic number turned out to be 4 months. It is important to note that even though the anthocyanin content significantly decreases during this time, the sensory contribution of the cherry wood does not decrease during this time period.

General enological parameters (titratable acidity, pH, etc), dissolved oxygen, pigment, and color were measured for all wines using various analytical techniques.

What did they find?

The authors found many results in this study, but I’ll just share a few of them for space considerations. Please feel free to ask if you’re wondering about any particular result that I may not have mentioned.

Dissolved oxygen stabilization was a function of the wood surface-to-wine volume ratio, with the smaller casks (225L) having a higher dissolution rate than the larger casks (1000L).
Dissolved oxygen levels were similar in wines aged in French oak barrels than cherry wood casks.
During the first month of aging, wine in cherry wood casks showed a higher SO₂ reduction trend than in French oak casks.

o In wines aged in cherry wood casks, the free SO₂ levels were lowest, compared to the French oak casks.

Total phenolic content was similar between wines aged in cherry wood versus wines aged in French oak casks.

o This result contrasts another study that found a significant decrease in polyphenols in cherry wood-aged wines after 3 months of aging. The researches cite differences in experimental methods as a possible explanation of this discrepancy.

Tannins increased for all wines in all aging conditions.
Wines aged in cherry wood saw faster reductions in anthocyanins than wines aged in French oak.

o The total pigment in the larger casks (1000L) was twice that of the smaller casks (225L).

After 4 months of aging, wines aged in cherry wood casks had the lowest percentage of acylated anthocyanins compared with all other storage treatments.
Wines aged in cherry wood casks showed large variations in the pigment profile of the wines at any given point in the aging process, indicating that wines aged in cherry wood casks may more significantly change from the initial anthocyanin content present in the wine than wines aged in other wood casks.
Cherry wood aging promoted the highest levels of adduct formation over time compared with other aging conditions.
Wines aged in cherry wood had the highest levels of color intensity compared to wines aged in other conditions.
After 2 months, wines aged in cherry wood possessed deeper colors, as well as a “redder” tint than the other aging conditions.

o After 2 more months, this redness decreased in shade, resulting in all wines sharing similar coloring regardless of aging condition.

French oak barrels did not contribute to wine color as much as cherry wood barrels.

What does this all mean?

http://www.wineoakbarrels.com/
images/oak%20barrels.jpg

According to the results of this study, the use of cherry wood barrels/casks in the aging of wine significantly influenced the color and pigment of red wine (in this case, Sangiovese/Merlot blend). Also, the anthocyanin content of wines was affected by the type of wood used for aging, with the cherry wood barrels/casks losing nearly all ρ-coumaroylated pigments by the end of the 4 month experimental aging period. According to the authors (and I agree), more work needs to be done to explore this result further: by examining the role of wood porosity and/or phenolic composition of cherry wood.

Due to the significant decrease in anthocyanins and pigments by the end of the 4 month aging period, it is recommended that wines aged in cherry wood barrels/casks are kept for relatively short periods of time or if longer age times are more feasible, then the use of larger barrels with lower wood-surface to wine-volume ratios should be utilized.

Of course, wines aged in cherry oak barrels with yield wines with a different aroma/flavor profile than wines aged in traditional oak barrels, so the decision to choose one type of barrel over another should not be simply based on anthocyanin content alone, as discussed in this post. One must take into consideration all the differences between wines aged in alternative wood barrels and traditional oak barrels (including economic differences) before jumping to any conclusions as to which barrel is right for them or their winery.

I'd also be curious to see how cherry wood aging affects other wines, including both red and white wines. Will we see the same results? Will some wines age better in cherry wood barrels than others?

What do you all think of cherry wood to age wine?

Have you ever tasted a wine aged in cherry wood barrels? I have to admit, I have not, but I would certainly be interested in trying one to compare between that and the more traditional aging methods.

I’d love to hear what you all think of this topic! Please feel free to comment below! (Note: If you do not see the comments section, be sure you are in the post URL and not just on the main page).

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!

Who’s Your Daddy?: Merlot

Rebecca Yeamans — Thu, 06 Sep 2012 10:30:05 +0000

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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 19^th 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!

Determining Wine Preferences by Olfactory Cues and Aromatic Attributes

Rebecca Yeamans — Tue, 04 Sep 2012 11:32:13 +0000

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Studies on olfactory influences on physiological and neurological responses are not new to science. It has been found that 80% of flavor sensations during eating in humans are attributed to the olfactory system (i.e. smelling). It is also well known that in humans, and many other living things with functioning olfactory systems, the sense of smell also acts as a sort of defense mechanism against possible threats.

http://www.earthlife.net/birds/images/procellariiformes/fulmar.jpg

For example, something very foul smelling may trigger a defensive response, as the smell may indicate danger or poison if ingested. Evolution has taken advantage of these responses over time, which can be seen in the example of the Fulmar bird. The Fulmar, which is closely related to the Albatross, is an extremely foul-smelling bird, with even smellier eggs. This provides the bird with protection against most predators, as the stench will nearly always trigger a danger response in the predator thus leaving the bird and/or eggs unscathed.

I realize I’m getting away from wine quite a bit, however, it is important to note that responses to olfactory cues (i.e. the aroma of that wine you have in your glass) have an underlying evolutionary and physiological origin that is common across many different living systems. Also, I’m kind of a geek and love sharing my random knowledge of science.

Anyway, I digress….

It is known that olfactory cues from food can alter one’s impression of the food. Does it smell good to you? This may trigger a positive response in your brain. Does it smell like rotten eggs? This may trigger a warning signal in your brain to not eat it due to possible danger. Olfactory triggers in the brain are distributed via two major pathways: through the limbic system and the frontal cortex. The first pathway, through the limbic system, influences the signals made by the hypothalamus and pituitary gland in the brain, and by which olfactory responses can alter mood and behavior without the individual being consciously aware of the change. The second pathway, through the frontal cortex, is where the conscious decisions occur and are processed with past memories and experiences to help make a determination of the identification of the odor.

http://cheriwalters.com/wp-content/
uploads/2010/03/smelling-wine-300x199.jpg

When it comes to wine, the aroma is often assessed to determine wine quality as well as one’s likeability of the wine. Studies have shown even the hunger level experienced by the person smelling the wine can change how one feels about the aroma and therefore the quality/likeability of the beverage.

Earlier this year, a team of Japanese researchers set out to study the decision-making process for selecting one’s favorite wine by using olfactory cues as well as physiological and neurological markers. To tell you the truth, I had a hard time with this paper, which I think can be partially blamed on the poor translation. Several times, what I was reading was not coherent sentences, which forced me to interpret what they were trying to say. Though the paper in and of itself was not the most properly edited, the topic is one I don’t see come up as often as others and so I wanted to share it with you all today.

Experiment I: Mental Impressions of Wine

For the first part of their experiment, the researchers had subjects smell wines to determine certain characteristics without tasting them. They recruited 24 students with no wine knowledge, and divided them up into a wine lovers group, and a non-wine lovers group. Subjects were asked to smell the wines, then answer a questionnaire in which they had to give the wines one of five criteria: “refreshing”, “amiable”, “favorite”, “delicious”, and “poised”.

The research team used analytical hierarchical process (AHP) to analyze the qualitative and quantitative aspects of a decision made on the wines, which according to the authors, has not yet been used in this type of experiment with wine. AHP is a mathematical technique that is used for multi-criteria decision-making processes. The decision problem is presented as a structure hierarchy, with the overall goal/decision positioned at the top. The next level of the hierarchy consists of criteria relevant to this overall goal/decision, while the bottom level are the alternatives being evaluated (the different wines in this example). This method of analysis, coupled with Principle Components Analysis (PCA) allowed the researchers to determine the subjects’ preferences for each wine.

Experiment II: Neuro-physiological responses to wine aromas

For this experiment, 16 subjects (8 wine lovers and 8 non-wine lovers) were seated in an environmentally-controlled room with the edge of a wine glass placed on a stand 10 centimeters under the nostril for the subjects to sniff. Subjects were presented with a non-odor solution, an alcoholic solution, and seven different wines. Solutions and wines were presented to subjects for three minutes at one minute intervals in a random order. Each subject underwent this experiment twice. Blood-oxygen levels were also measured, which were done so by using NIRS and EEG measuring caps.

Figure 2 from Koike et al, 2012.

As an aside, I wanted to point out an example of the awful translation/editing done on this paper. Figure 2 shows an image of the experimental set up for Experiment II. Notice anything odd in this picture? Wine by the Grass? Really? I swear, I did not alter this photograph in any way shape or form. Here is the icing on the cake: to describe the image in detail, the text read something like this: “…the edge of a blade of grass kept on a stand was placed under 10 centimeters from the nostril for the subject to sniff the wine aroma”. I’m sorry, but was there not a single person that could speak any English editing this translation? You can’t make this stuff up.

Again, I digress….

So what did this study find?

This study found that for wine lovers, the criteria of “Favorite” was rated of highest importance in both empty and moderately empty stomach conditions, while the criteria “Poised” was rated lowest.
Not surprising, “Amiable” and “Delicious” were rated higher in empty stomach conditions than in moderately empty stomach conditions.
For wine lovers and non-wine lovers, the highest ranked wine was Wine #3 and Wine #5 for both stomach conditions.
For wine lovers with the moderately empty stomach condition, Wines #3 and #5 at first significantly increased blood-oxygen levels compared to the non-odor solution in the left and right sides of the subjects’ foreheads, respectively.

o Wine #3 significantly changes blood-oxygen levels at 2 and 3 minutes compared to the non-odor solution.

o For non-wine lovers, blood-oxygen levels remained unchanged.

For wine lovers with the empty stomach condition, blood-oxygen levels increased in the third minute when Wine #3 was given.

o For non-wine lovers, blood-oxygen levels remained unchanged.

So, what does this all mean?

The primary result of this study was that both wine lovers and non-wine lovers identified Wine #3 as their “favorite” wine, followed by Wine #5. The study also found that blood-oxygen levels significantly increased for wine lovers in the third minute of exposure to the wine aroma for Wine #3 compared to non-odor and alcoholic solutions. However, for the non-wine lovers, this increase in blood-oxygen level was not found, and instead no significant changes were noted. According to the authors of this study, these results indicate that there is a discrepancy between the psychological expression and the physiological response when smelling wine.

Some studies have found that there is a differing cortical response to the expectation of eating food when the subject was hungry versus full. This study found that blood-oxygen levels decreased from seconds in empty stomachs to minutes in moderately empty stomachs, possibly indicating that the reward response to the wine aroma was decreased and satisfied. In other words, smelling the wine on an empty stomach more quickly satiated the subject than smelling the wine on a fuller stomach, since a fuller stomach is already more satisfied.

It is important to note that this blood-oxygen response was only found with wine lovers. With non-wine lovers, there was no significant change in blood-oxygen levels when presented with wine aromas. According to the authors, this may indicate that non-wine lovers are satisfied by wine aroma. In other words, they may not feel any sort of pleasurable emotion when smelling wine.

“The Big Reveal”

Which wines were Wine #3 and Wine #5, the “favorites” identified by the subjects in this study. Wine #3 turned out to be wine made from Niagara grapes, and Wine #5 was made from Campbell Early grapes; both grapes belonging to Vitis labrusca and having sweet aromas and sweet tastes. The other wines not ranked as highly by the study subjects were Vitis vinifera and dry. The authors suggest that the sweet aroma of the two “favorite” wines for subjects in this study could be leaving a psychological positive impression on them.

What do I think?

Perhaps is preference again due to the evolutionary development of a scent-based defense mechanism. Maybe a sweet smell triggers a positive response that there is something good to eat present, while an astringent or bitter smell (as one may find in some dry wines) may trigger a more negative response indicating to the individual that poison or danger may be afoot.

http://wine-zag.com/wp-content/
uploads/2011/01/what-wine-do-I-like.jpg

This preference could also be attributed to the study subject population. The study subjects were students (i.e. young and inexperienced) with no prior wine knowledge other than knowing whether or not they liked wine at all. Since they have not yet had many wine experiences, these results could be related to the fact that inexperienced wine drinkers tend to gravitate toward sweeter wines than drier wines.

Overall, while the results may be interested from a purely scientific standpoint, they can in no way be extrapolated to any other population. The study subjects were (assumingly) all Japanese students, the age of which I am assuming is relatively young. The study subjects are all very inexperienced in wine. Also, the sample size was extremely small, with only 16 subjects participating in Experiment II. The results of this study can only therefore be interpreted for this tiny subset of a population and cannot be assumed to be the reality for other populations. Would the results of this study be the same as if it were repeated on French wine experts? I highly doubt it (though I could be wrong…).

I am also very disappointed with the quality of editing and the translation of this paper. Some of the mistakes are cringe-worthy (see Figure 2 above) and should absolutely have not passed through the editors without so much as a “hey, that doesn’t make that much sense…”. I’d also like to see the study repeated using a larger and more diverse population (including not only wine novices but also wine experts and general wine enthusiasts). Finally, what about taste? Though olfactory cues are a huge player in determining preferences, one cannot forget about taste. Do decisions made solely by olfactory cues change when taste is introduced?

I’m certain there are many other things that could be improved in this study, but I’ll leave that up to you all to suggest in your comments below. What do you think about this topic and this research? Please feel free to leave your comments below!

References:

Koike, T., Kamimura, H., Shimada, K., Yamada, H., and Kaneki, N. 2012. Determination of Favorite Wine from Comparison of Wine Aroma Attributes. Kansei Engineering International Journal 11(1): 41-50.

http://www.fivesenses.com/Documents/Library/5%20%20Future%20Olfactory%20Research.pdf Accessed 09/03/2012

http://listverse.com/2010/12/23/10-birds-with-truly-odd-defenses/ Accessed 09/03/2012

Using Grape Seed Extract in Beef Patty Marinades: Evidence for the Reduction of Carcinogenic Compounds in Red Meat

rebecca — Tue, 07 Aug 2012 04:01:01 +0000

It has been well established that consumption of red and processed meats increases the risks of developing colorectal cancer, as well as other negative health effects in humans. Specifically, studies have found that people should not eat more than 500 grams of red meat (cooked) per week, and should avoid processed meats entirely. In these meats, heterocyclic amines (HAs) are present, some of which are known to be carcinogenic in animals (including PhIP, MeIQx, and 4, 8-DiMeIQx).

http://www.nmgastronome.com/usa/
burgers/Images/WineBurger01.jpg

Some studies have found that by adding antioxidants, the formation of these carcinogenic HAs is inhibited. Specifically, these studies have examined antioxidant protection from tart cherry tissue, carotenoids from tomatoes, fruit extracts, or various spices. One extract in particular, grape seed extract, is known to have very high antioxidant capacities, and therefore is a viable option for inhibiting the formation of HAs in the food industry.

The goal of the study presented today was to determine the ability of water-in-oil marinades containing grape seed extracts to reduce the HA content in beef patties. Marinades were chosen due to their known ability to reduce HA content in meats, according to some studies.

Methods

Frozen beef patties were approximately 70 grams and measured 8x113x105mm.

Grape seed extract was produced by water extraction and spray drying. The extract was then dissolved in ultrapure water, filtered, and then used in the marinades using the following amounts: 0.2g, 0.4g, 0.6g, and 0.8g per 100g water-in-oil emulsion.

Water in oil emulsions were created by homogenizing 67.5 grams of sunflower oil, 0.5 grams of an emulsifier (citric acid esters of mono- and diglycerides of fatty acids) and 32 grams of the diluted grape seed extract. The emulsions were set to marinade with the beef patties immediately after manufacturing. Water-in-oil emulsion controls without grape seed extract were also included in the study.

Beef patties were fried on two plates of a double contact grill that was preheated to 230^oC. Frozen patties were coated with 1.5 grams of refined sunflower oil alone or water-in-oil emulsions with or without the grape seed extract on both sides. Patties were then covered on both sides with aluminum foil. Patties were fried for 2 minutes and 40 seconds, a time which has been established to result in acceptable sensory character in beef patties. For each treatment, 8 patties were fried and homogenized for chemical analysis. For sensory analysis, 8 patties were fried (after marination) and divided into four pieces each.

The following were measured/analyzed for all treatments: antioxidant capacity, total phenolic content, concentrations of HAs, beef patty weight loss, creatine content, and glucose levels.

For the sensory analysis, 8 panelists were selected and trained to analyze sensory characteristics of beef in this type of marinade system. Sensory characteristics were ranked on a hedonic scale, ranging from 1 (best color and/or flavor) to 6 (worst color and/or flavor). Panelist also described any potential negative color or flavor characteristics.

Results

Beef patties broke down into the following components: 61.1g/100g moisture, 0.72g/100g minerals, 21.2g/100g fat, 17.6g/100g protein, 0.293g/100g hydroxyl proline, and 0.84g/100g glucose.
Beef patties were found to contain the HAs MeIQx, PhIP, and the co-mutagenic β-carbolines Norharman and Harman.
The highest amount of grape seed extract present in the marinades (8g/kg) resulted in a reduction in MeIQx of 68% and a reduction in PhIP of 90%.
Increased amounts of grape seed extract in the marinades led to increased concentrations of the β-carbolines Norharman and Harman.
There were no significant differences between patty weight loss in the control samples versus the samples marinated in grape seed extract.
Patties pretreated with grape seed extract were significantly darker at the highest concentration of extract that all other samples (8g/kg).
Compared to rosemary extract (which was also studied in this paper but not presented for the purpose of this blog’s theme), grape seed extract had a significantly higher antioxidant activity.
Total phenolic content in grape seed extract was 26 times higher than in rosemary extract.
Linear correlation analysis suggested that formation of the HAs MeIQx and PhIP are dependent upon the antioxidant capacity of the extract.
Sensory analysis found no differences between control beef patties and beef patties marinated in grape seed extract.

o Both color and flavor were not significantly different between these treatments.

Conclusions

The results of this study indicate that levels of the two carcinogenic HAs that were found in frozen beef patties, MeIQx and PhIP, were significantly reduced after a marinade treatment containing grape seed extract. This result is likely due to the fact that grape seed extract contains high concentrations of antioxidants, which are effective free radical removers and thus overall effective HA reducers.

By looking at water and oil as bases for the beef patties marinades, the authors determined that the solubility of the grape seed extract components were not as important as the total phenol and antioxidant content of the marinades. In addition to antioxidants, according to the authors it is possible that other compounds are playing important roles in the reduction and inhibition of HAs, including hexose and pentose, the effects of which warrant further study.

Overall, the results of this study indicate that using grape seed extracts in beef patty marinades is an effective pretreatment prior to the cooking process, since it significantly reduces the levels of carcinogenic HAs in the meat as well as having no effect on the sensory characteristics of the finished hamburger. It is possible that this pretreatment may be recommended to restaurants that cook significant numbers of beef patties (including fast food chains) and also possibly the pretreatment of meat going to grocery stores and specialty shops.

I’d love to hear what you all think about this topic! Would you like to have seen the authors perform any other types of analysis? Please feel free to leave your comments below!

Source: Gibis, M., and Weiss, J. 2012. Antioxidant capacity and inhibitory effect of grape seed and rosemary extract in marinades on the formation of heterocyclic amines in fried beef patties. Food Chemistry 134: 766-774.

DOI: 10.1016/j.foodchem.2012.02.179

Eliminating the Fishy Aftertaste of Wine-Seafood Pairings: A Novel Approach

rebecca — Fri, 03 Aug 2012 10:30:04 +0000

There is a whole host of information, both scientific and anecdotal, on how to pair wine with food, which is in a continual state of flux. One example of a wine and food pairing that is often not recommended is red wine with seafood. This pairing is often not recommended as a result of the perception of a fishy aftertaste and metallic odors due to the tannins and other compounds in the wine. It has also been observed that white wine sometimes carries with it this same fishy aftertaste when paired with seafood, and since white wine has very little tannin, the recommendation that red wine not be paired with seafood as a result of the tannin is likely anecdotal. In fact, a recent study found that iron was actually a key cause of the fishy aftertaste in wine, occurring both in red and white wines.

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Finding a way to eliminate this fishy aftertaste in wine is very important, especially since statistics show that the world consumption of seafood is on the rise, and one should be able to drink any wine they’d like with their meal without incurring any unwanted flavors. The average concentration of iron found in wines around the world ranges from 2.8 to 16mg/L. Iron gets into the wine by way of the soil, dust, and the winemaking equipment. When there are excess levels of iron present in the wine, certain fining agents or cooling may be used to precipitate the iron and subsequently remove it from the finished wine.

One major problem with this removal method is that only very low levels of iron are needed to elicit the fishy aftertaste in wine after seafood pairing, and current methods used for removing iron would not be able to bring iron levels down low enough without removing other important quality compounds in the wine. Ferrocyanide is known to effectively remove iron, however, its’ disposal is problematic as it is considered toxic waste. Phytic acid is a more trusted and safe compound for removing iron in food products though, like other removal methods, it does not effectively remove enough iron to prevent the fishy aftertaste.

The goal of the study presented today was to determine an effective method for removing iron from wine in order to reduce the fishy aftertaste in wine-seafood pairings by using yeast as an adsorbent.

Methods

Wine yeast OC-2 was cultured in pre-prepared media at 25^oC for 3 days.

Generic white grape juice concentrate was dissolved and diluted to 20^oBrix. The final adjusted concentration of iron in the juice was 4-7mg/L.

Fermentation between the OC-2 yeast and prepared grape juice was performed at 20^oC for 30 days in a 50mL test tube while in the presence of oxygen. Samples were taken throughout the fermentation process to measure sugar, yeast concentration, and yeast viability.

Wines made for sensory analysis started off with the same grape juice base as described previously. Active dry yeast DV10 was used for fermentation, which was performed at 20^oC for 7 days in a 15L jar fermentor. After fermentation, wine was centrifuged and fined with chitosan and bentonite. Other wines (both red and white) were purchased from the domestic market in Japan.

Titratable acidity, sulfur dioxide, and pH of all wine samples were measured. Yeast cell viability was also measured.

To prepare yeast cell with alcohol (in order to function as the adsorbant), yeast cells were cultured for 3 days then alcohol was added to a final concentration of 20-70% (v/v). Wet alcohol-treated yeast cells were then dried.

Once alcohol-treated yeasts were created, they were added to the wines and grape juices at varying concentrations and shaken. Wines were treated by the addition of 1, 2, and 3g/L of alcohol-treated yeasts. Yeasts were left to sit in the wines for one day, then were centrifuged and removed.

A Phytic acid treatment was also included in this study. Phytic acid was added to the wines and grape juices, left for one day, then centrifuged and removed.

Efficacy of iron removal from wine by using alcohol-treated yeast cells was determined by measuring the iron left over in the wines after treatment and comparing these values with the iron levels measured before the treatment began.

A sensory analysis was also performed on the wines to determine the intensity of fishy aftertaste. The panel was made up of 11 staff members (7 men and 4 women) ranging from age 26 to 59, all with wine tasting experience.

A triangle test was performed by comparing an untreated control wine to wine treated with alcohol-treated yeast cells, followed by a 30 minute incubation and then clarification using fining agents. Panelists were given three glasses of wine and were told one differed from the other two. 20 sets of wine in two sessions were evaluated. Alcohol-treated yeast wines were always compared to a no treatment control.

Panelists were first trained to the fishy aftertaste by way of a reference solution that contained 3mM FeSO₄.

Perceived intensity of the fishy aftertaste was measured as: 1) barely detectable; 2) weak; 3) moderate; 4) strong; and 5) strongest imaginable.

Commercial dried scallops were used for the wine-seafood pairing, since scallops are known to elicit a very strong fishy aftertaste in wine. The protocol was as follows: 1) chewing and swallowing scallops; then 2) taking a sip of wine; and then 3) evaluating the intensity of the fishy aftertaste. Drinking water was provided in between each food-seafood pairing.

Wine samples were presented at random. At first, panelists only tasted wines. Afterwards, panelists tasted three wines with dried scallops.

Wine without the alcohol-treated yeast was the positive control.

The following were measured to determine if the treatment affected other compounds in the wine: organic acids, alcohols, esters, aldehydes, and finally, iron.

Results

Wine yeast cells adsorbed iron rapidly during the early stages of fermentation.
Gradual release of iron was observed after 10 hours of incubation.
The OC-2 yeast strain did not take up iron during fermentation as well as the common wine yeast Saccharomyces cerevisiae.
Approximately 100 hours after fermentation, as the proportion of dead cells increased, the concentration of iron in the wine decreased.

o This suggests dead yeast have a significant ability to adsorb iron in wine.

Greater than 40% v/v ethanol in treated yeasts was required for effective iron adsorption.

o Less the 30% v/v ethanol is not recommended, as it may not kill all of the yeast and thus risk refermentation or other complications.

The addition of ethanol-treated yeast cells to wine pretreated with phytic acid was observed to remove all of the residual iron in the wine.

o This synergistic effect was not affected by the drying process of the yeast, as iron removal was the same for both fresh and dried treated yeasts.

Using 1g/L or 3g/L of ethanol-treated yeasts alone removed all residual iron from the wines.

o Using a mixture of phytic acid plus ethanol-treated yeasts allowed the concentration of yeasts needed to remove all residual iron to drop down to only 0.5g/L.

The combination of ethanol-treated yeasts plus phytic acid was the most effective treatment in reducing iron levels in wine.

o Other alcohols tested and found to be just as effective as ethanol were: n-propanol and isopropyl alcohol.

Sensory Analysis

Panelists were not able to tell the difference between control wines and wines treated with 1 and 2g/L of ethanol-treated yeasts.
Wines treated with isopropyl alcohol-treated yeasts plus phytic acid resulted in the least fishy aftertaste.
In regards to organic acids, esters, alcohols, and aldehydes, there were no differences in concentrations of these compounds between untreated control wines and wines treated with alcohol-treated yeasts and/or phytic acid.

Conclusions

According to the results of this study, the authors claim that they have successfully developed a novel method for enhancing the iron-adsorbing ability of yeasts (and thus iron removal from wine) by treating the yeasts with greater than or equal to 40% v/v ethanol. The drying process did not seem to have any effect on the iron-adsorbing ability of the yeasts, which is good news for large scale processing and distribution of the product.

Iron removal was found to be very effective with the combination of alcohol-treated yeasts and phytic acid, however, phytic acid alone was not nearly as effective. This study found that phytic acid is more effective in some wines than others, and that using alcohol-treated yeasts in concert with the compound would removal all iron from the wine without question.

The authors suggested one problem with using alcohol-treated yeasts to remove iron in wine and that is that there is a relatively high cost to filtering something with such high a density. When using alcohol-treated yeasts alone, 3 g/L of cells were required to be effective. This could be costly to filter such a relatively dense mass once the iron removal process was complete. By using a combination of alcohol-treated yeasts and phytic acid, the authors found that significantly less alcohol-treated yeasts would be required to effectively remove iron in wine. Specifically, when used in concert with phytic acid, only 0.5 g/L of alcohol-treated yeast cells are needed. By using much less alcohol-treated yeasts, the cost of filtering and removal is markedly reduced.

The results of this study present an effective method for iron removal from wine using alcohol-treated yeast cells followed by a phytic acid treatment. The sensory results were promising in that this treatment resulted in wine that had no hints of fishy aftertaste when consumed after eating scallops; nor were there any negative changes in the desirable sensory characteristics of the wine. I’d be curious to see if the results are repeatable at a commercial level, and also if the treatment is effective in all varietals and blends.

Being that it is the first paper showing the effectiveness of this new iron removal method for wine, much more research needs to be done. I’m curious, what do you all think should be the next step in this line of research? Leave your comments below!

Source: Tsuji, T., Kanai, K., Yokoyama, A., Tamura, T., Hanamure, K., Sasaki, K., Takata, R., and Yoshida, S. 2012. Novel Method to Reduce Fishy Aftertaste in Wine and Seafood Pairing Using Alcohol-Treated Yeast Cells. Journal of Agricultural and Food Chemistry 60: 6197-6203.

DOI: 10.1021/jf300265x