Synthetic Cork Research Articles

Wine Closure Performance of Three Common Closure Types: Chemical and Sensory Impact on a Sauvignon Blanc Wine

A Napa Valley Sauvignon blanc wine was bottled with 200 each of a natural cork, a screw cap, and a synthetic cork. As browning is an index for wine oxidation, we assessed the brown color of each bottle with a spectrophotometer over 30 months. A random-effects regression model for longitudinal data on all bottles and closure groups found a browning growth trajectory for each closure group. Changes in the wine’s browning behavior at 18 months and 30 months showed that the browning of the wine bottles appeared to slow down later in the storage period, especially for natural corks. The between-bottle variation was the highest for the natural cork. At 30 months, we separated the bottles by the extent of browning and samples were pulled from the high, mid, and low levels of browning levels for each closure. The degree of browning is inversely correlated with free SO2 levels ranging from 5 to 12 mg/L. However, a Quantitative Descriptive Analysis (QDA™) sensory panel could not detect any difference in their aroma and flavor profile between closure types regardless of browning level. Even low levels of free SO2 retain protection against strong oxidation aromas, and visual browning detected by spectrophotometer seemed to precede oxidative aroma and flavor changes of the aging Sauvignon blanc.

Combined effects of the vessel type and bottle closure during Chilean Sauvignon Blanc wine storage over its volatile profile

A Sauvignon Blanc wine was subjected to a maturation period of six months by using four different types of vessels in triplicate: cylindrical stainless steel tanks, oval-shaped polyethylene tanks, cubic-shaped polyethylene tanks, and clay jars. After maturation in the different vessels, wines were bottled using three different closures (natural cork, synthetic cork, and screwcaps). The volatile compound profiles of the wine samples were recorded by SPME-GC–MS throughout vessel maturation as well as after the bottle storage period. In general terms, wines stored in stainless steel tanks showed the highest contents of volatile compounds when compared with the other tested vessels. Moreover, wines from bottles capped with screwcaps showed the highest contents of most of the volatile compounds when compared with the other closures. Moreover, an interaction between the vessel and the closure was observed: when screwcaps were used during bottle aging, the resulting wines were very similar to those matured in stainless steel vessels. These results suggest that the use of screwcaps hides the differences originating from wine composition during maturation in vessels other than stainless steel.

What effect does wine bottle closure type have on perceptions of wine attributes?

We examined the effects of an extrinsic attribute of wine—closure type (natural, screw, synthetic, or glass)—on perceptions of intrinsic attributes (appearance, taste, bouquet, and overall quality) by comparing two separate samples of tasters to determine whether differences exist. A convenience sample of students, parents, faculty, staff, and community members in a college town in the northwestern United States participated in the study. The findings confirmed the positive halo effect of natural corks when compared with screw caps and synthetic corks. More specifically, wine thought to have been poured from a bottle with a natural cork closure registered significantly higher ratings on appearance, bouquet, taste, and overall quality compared with wines closed with screw caps or synthetic cork closures, but not those with glass closures. Our findings suggest that glass stoppers could replace natural corks without generating significantly negative effects on perceptions of intrinsic wine attributes.

The Combined Effects of Storage Temperature and Packaging on the Sensory, Chemical, and Physical Properties of a Cabernet Sauvignon Wine

A Californian Cabernet Sauvignon was stored for 6 months at three different constant temperatures to study the combined effects of storage temperature and packaging configuration. Glass bottles with natural cork, synthetic cork, and screw cap closure, as well as two Bag-in-Box treatments, were used in the experiment. A trained sensory panel was able to detect significant changes in aroma, flavor, taste, mouthfeel, and color attributes among the samples, differences that were found also with various chemical and physical measurements (volatile profile, polyphenol pattern, enological parameters, color space). Additionally, two commonly used polyphenol assays were compared to each other in terms of their ability to detect the changes in the polyphenol profile. Generally, sample changes were more pronounced due to the different storage temperatures, with 30 sensory attributes differing significantly among the three different storage temperatures, while only 17 sensory attributes showed a significant packaging effect. With increasing storage temperature the packaging effect became more pronounced, resulting in the largest changes in the Bag-in-Box samples stored at the highest temperature of 40 °C. At the highest storage temperature, all wines showed oxidized characters, independent of the wine packaging configurations, but to a varying degree. Generally, wines that received highest oxygen amounts and storage temperatures were much lighter, less red, and more brown-yellow at the end of the 6-month storage period, compared to their counterparts stored at 10 °C. These changes in color and polyphenols, respectively, were also detected with the two spectrophotometric assays. With increasing storage temperature both assays measured reduced concentrations in total phenols and total anthocyanins, while total tannins, degree of ionized anthocyanins, and color density increased. Various volatile compounds differed significantly among the samples, with largest relative concentration changes in acetates, organic acids, and alcohols, in good agreement with previous literature reports, with some being well correlated to specific sensory attributes too; for example, various acetates correlated to cherry and fruit aromas and flavors. The study shows that storage at elevated temperatures could be a valuable tool for wine packaging screening and testing new and improved wine packaging types under the worst conditions, which are unfortunately not unrealistic.

The effect of wine closures on volatile sulfur and other compounds during post‐bottle ageing

ABSTRACTThe effect of wine closures on volatile composition during post‐bottle ageing was investigated for Pinot Noir and Chardonnay wines. Natural cork, synthetic cork and screw caps with Saran–tin, Saranex and low density polyethylene (LDPE) liners were investigated over 3 years of storage. Dissolved O2 and SO2 as well as colour were monitored. Volatile sulfur compounds, esters, terpene alcohols, and C13‐norisoprenoids were quantified every 6 months over 3 years. The results showed that the LDPE screw cap gave the highest dissolved oxygen, lowest free SO2 and total SO2 in both wines, while the Saran–tin screw cap gave the lowest dissolved oxygen and the highest free SO2 and total SO2. A decrease of H2S, methanethiol, and thioacetates were observed during the 3 year ageing process for both wines, and their concentrations decreased most in wines sealed with LDPE screw caps and synthetic closures. The decrease of thioacetates was independent of closure type. The accumulation of dimethyl disulfide during storage was not obvious in these two wines. For both wines, no elevated sulfur compounds under any closure were detected; neither dimethyl disulfide nor dimethyl trisulfide were found in any of the experimental wines. Other volatiles also changed with in bottle ageing. Ethyl esters decreased during ageing, whereas ethyl 2‐methylbutanoate and ethyl 3‐methylbutanoate increased during ageing. Terpene alcohols showed a decreasing trend with ageing, as was β‐damascenone, but β‐ionone remained unchanged in Pinot Noir wine during ageing. Both wines under LDPE closure had the highest acetaldehyde at 36 months of ageing. Wine closure affected the concentration of terpene alcohols and C13‐norisoprenoids. Closure had no impact on nerolidol and citronellol, but LDPE screw‐capped wine had lower concentrations of linalool at 36 months of storage. Both wines with LPDE screw cap closures had higher β‐damascenone. Closure had no effect on β‐ionone and other compounds. Copyright © 2013 John Wiley & Sons, Ltd.

The Combined Effects of Storage Temperature and Packaging Type on the Sensory and Chemical Properties of Chardonnay

Californian Chardonnay was stored in five different wine-packaging configurations at three different temperatures for a period of 3 months to study the combined packaging and temperature effects on the sensory and chemical properties of the wines. A trained descriptive panel evaluated aroma, taste, mouthfeel, and color attributes, and the sensory results were correlated to physical and chemical measurements including volatile compounds, SO(2), titratable and volatile acidity, oxygen consumption, and wine color, using partial least squares regression. In general, increased storage temperatures induced the largest changes in the wines; however, significant packaging--temperature effects were found for some attributes as well. Particularly wines stored in bag-in-boxes at 40 °C showed significant increases in oxidized and vinegar aromas and yellow color. Volatile esters also decreased in these wines, while increased levels of compounds generally associated with age- or heat-affected wine were found including 1,1,6-trimethyl-1,2-dihydronaphthalene and furfuryl ether, consistent with previously reported chemical aging reactions. In summary, storing unoaked Chardonnay in different packages significantly changes the sensory and chemical properties depending on the storage temperature. After a storage period of 3 months, bottle storage with various closures (natural cork, synthetic cork, and screw cap) changed the wine in a different way than bag-in-box storage.

The Importance of Wine Bottle Closures in Retail Purchase Decisions of Consumers

This study examines the importance of different wine bottle closures, such as natural cork, synthetic cork, and screw tops, in the retail purchase decision of wine by millennials and baby boomers. By segmenting consumers in this manner, it is possible to better understand their preferences and aid wine producers and retailers in directing their marketing and advertising efforts. The results of this study indicate that the type of bottle closure impacts the consumers purchase decision differently, depending on the type of purchase—whether for personal consumption, gift giving, or special occasion. Wineries and retailers of wine will find that closure type does impact consumer perceptions and its relevancy to market segmentation.

Effect of Closure, Packaging and Storage Conditions on Impact Odorants of Wine

3-alkyl-2-methoxypyrazines (MPs) represent an important and potent class of odor-active compounds associated with wine quality. 30 ng/l each of 3-isobutyl-2-methoxypyrazine, 3-isopropyl-2-methoxypyrazine and 3-secbutyl-2-methoxypyrazine were added to a Riesling and Cabernet Franc wine and monitored with HS-SPME-GC-MS over 18 months to investigate the effects of various closure and packaging options as well as light and storage temperature on MPs. Other impact odorants were monitored using SPE-GC-FID. Changes in MP concentrations during bottle aging varied with closure/packaging option, with the greatest decrease evident in Tetrapak® cartons. We observed similar changes in other impact odorants to previous studies, with synthetic corks displaying an increased capacity for sorption compared to natural corks and screwcaps. MPs did not vary consistently over time with light or temperature conditions. Acetate esters decreased, regardless of light or temperature conditions, while phenethyl acetate and isoamyl acetate decreased at a greater rate in ambient temperature conditions compared with 12°C. Free and bound SO<sub>2</sub> retention was higher in light-excluded conditions and influenced by bottle hue.

Effect of Closure and Packaging Type on 3-Alkyl-2-methoxypyrazines and Other Impact Odorants of Riesling and Cabernet Franc Wines

3-Alkyl-2-methoxypyrazines (MPs) represent an important and potent class of grape- and insect-derived odor-active compounds associated with wine quality. Thirty nanograms per liter each of 3-isobutyl-2-methoxypyrazine (IBMP), 3-isopropyl-2-methoxypyrazine (IPMP), and 3-sec-butyl-2-methoxypyrazine (SBMP) was added to Riesling and Cabernet Franc wines and monitored with headspace solid-phase microextraction and gas chromatography-mass spectrometry over 18 months to investigate the effects of various closure and packaging options on MPs. Changes in MP concentrations during bottle aging varied with closure/packaging option, with the greatest decrease evident in Tetrapak cartons. After 18 months, IBMP, IPMP, and SBMP in both Tetrapak-stored wines decreased by approximately 45, 32, and 26%, respectively. Similar changes were observed in other impact odorants to previous studies, including a greater decrease in odorant concentrations in wines closed with synthetic corks compared to natural corks and screw caps. These differences are thought to be due to the differential sorptive capacities of the various closure types. Overall, the data suggest that differences in gas permeability/contribution from the different closure and packaging options strongly associate with changes in wine composition during aging.

Effects of Bottle Closure Type on Consumer Perceptions of Wine Quality

The effects of natural cork, synthetic cork, and screwcap closures on wine consumer perceptions of the quality of commercial wines bottled for 33 months were examined in two experiments. The first determined that wine consumers could not detect sensorial differences between Chardonnay and Merlot wine samples sealed with the three closure types. The second measured if and how consumer wine-quality perceptions changed based on the type of closure used to seal the wine. Wines were presented twice to the same consumers: first when the closures were not revealed and second when each wine closure was revealed. For the Chardonnay samples, the knowledge that the wine was sealed with a natural cork did not significantly affect the liking or quality scores. However, when participants knew that the sample was bottled with a synthetic cork, the liking score tended to be lower and the difference was nearly significant, but quality ratings did not change. When participants learned the wine had a screwcap, both the liking and quality ratings were significantly lower. For the Merlot samples, there was no change in liking scores for any of the closures, but quality scores for the wine with a natural cork increased significantly.

Effects of Wine Bottle Closure Type on Consumer Purchase Intent and Price Expectation

The effects of natural cork, synthetic cork, and screwcap closures on the purchase intent and price expectation of wine consumers was examined for two commercial wines, a Chardonnay and a Merlot. Consumer purchase behavior was measured in a taste survey where participants tasted and rated the wines twice: once when the closure information was not known and a second time when the closure information was revealed. Causal effects were evaluated for impact on purchase behavior when the closure information was revealed using ordinary least squares regression, logistic regression models, and path analysis. Liking rating for the wine was the most important variable to impact purchase intent. The effect of liking on purchase intent was positive where there was ~10% higher probability of buying the wine for a 1-unit increase in liking rating; type of closure had only limited impact on purchase intent. The results for price expectation are different than for purchase intent in that liking did not impact expected price; quality had the greatest impact. For the expected price models, results indicated that consumers expected to pay significantly less for a bottle with a screwcap for both wines. The significant negative effect of the screwcap on expected price relative to synthetic and natural corks indicated a direct negative effect. However, the positive correlation of natural cork and negative correlation of screwcap with quality rating indicated that closure type also impacts expected price indirectly through consumer perception of quality.

The Experiment of Floating Ability of Material of Polyurethane and Styrofoam

Polyurethane can be used as alternative of substituted material of synthetic cork (Styrofoam) giving buoyancy at float vest. The research was aimed to observe the difference both materials (Polyurethane and cork) on acceptable load, so that efficiency can be estimated. The same load was given to gravity at both material that is 234.576 g, then checked the float ability. Results showed that Polyurethane indicated buoyancy of polyurethane better cork, with efficiency 3.6 %, for sample material with size of 10 cm x 7.5 cm x 5.5 cm. The Significant change of efficiency was expected can be done by determination of material (sample) according to use in field and different density of polyurethane when conducting moldings process. Key words : The experiment of floating ability

Wine bottle closures: physical characteristics and effect on composition and sensory properties of a Semillon wine 1. Performance up to 20 months post-bottling

A Semillon wine was bottled using 14 different closures: a screw-cap type, two grades of conventional natural cork, two 'technical cork' closures (natural cork with a synthetic component), and 9 closures manufactured from synthetic polymer material. Closure performance was evaluated for physical aspects (e.g. extraction force and energy, change in closure diameter, and ease of closure reinsertion), and for wine composition and sensory properties. Wine under the screw cap closure retained the greatest concentration of sulfur dioxide (SO2) and ascorbic acid and had the slowest rate of browning. For other closures the trend of SO2 loss relative to the screw cap closure was apparent from an early stage of testing, and was most evident in the group of synthetic closures, intermediate in the conventional corks, and least evident in the technical cork closures. The loss of SO2 was in general highly correlated with an increase in wine browning (OD420) and the concentration of SO2 in the wine at six months was a strong predictor of future browning in the wine, particularly after eighteen months. Neither the concentration of dissolved oxygen at bottling (0.6-3.1 mg/L), nor the physical closure measures were predictors of future browning. For several closures upright storage tended to accelerate loss of SO2 from the wine, but in many cases this effect was marginal. The closures differed widely in regard to physical characteristics, and in general synthetic corks appeared least 'consumer-friendly' in terms of extraction forces, energies, and ease of closure re-insertion, but there was a trend for natural cork closures to exhibit larger variability in physical characteristics than technical cork and synthetic closures. Sensory analysis indicated large differences in wine flavour properties, with closures which tended to result in the best retention of free SO2 having wine sensory scores for 'citrus' that were generally high whilst scores for the attributes 'developed'/'oxidised' were low. The situation was reversed for wine under closures that performed poorly in the retention of free SO2. It was found that below a critical level of free SO2 remaining in the wine, closures exhibited substantially higher 'oxidised' aroma. Whilst trichloroanisole-type (TCA) taint was a noticeable problem for some cork and technical cork closures, any plastic-type taint appeared not to be a problem with most synthetic closures.

Consumer Acceptance of Synthetic Corks

Problems with corks are a major issue in the wine industry. The key problem has been the lack of consumer acceptance of alternative closures. This research used an interview and survey approach with 200 wine shoppers in Australia to determine: 1) consumer perceptions of cork problems; 2) acceptance of a synthetic cork with no information provided; and 3) acceptance of a synthetic cork after providing information concerning cork problems and solutions. Consumers who purchased more than one bottle of wine per week had the most problems with corks, but 75% of all consumers interviewed had experienced some problems in the last 12 months. The provision of information was key in gaining consumer acceptance of the synthetic corks. Measures of which attributes of the synthetic corks attracted consumers is also provided along with recommendations for introducing these closures into the marketplace.

Measurement of Oxygen, Nitrogen, and Carbon Dioxide in Beverage Headspace

A method has been developed to analyze headspace oxygen, nitrogen, and carbon dioxide in a variety of beverages and packages. A package is punctured with a specialized sampler. The headspace gases flow into an evacuated gas sampling valve. The gases are automatically switched onto a gas chromatographic column where they are separated and then detected using a thermal conductivity detector. The peak areas of the headspace gases are compared to those of calibration gases to determine the quantity of each gas present. Gases may be determined at concentrations as low as 150 ppm v/v (0.002 psia; 20.5°C) for oxygen and up to 100% v/v (70 psia; 20.5°C) for carbon dioxide. After calibration, the time for duplicate analysis of all three gases is 11.0 min. The procedure has been used to study nitrogen purging in cans, antioxidant effects in juices, headspace oxygen in aseptic packages, wine headspace composition, permeation through synthetic corks, and beverage carbonation corrected for the effect of headspace oxygen and nitrogen.