Cork Supply USA and Silver Oak Cellars have developed a commercial application for a state-of-the-art sensory evaluation process to detect the presence of TCA (2,4,6-trichloroanisol) in corks used for sealing wine bottles of large format.
Silver Oak Large Format Wine Bottle
TCA is a chemical compound that causes cork to taint. The process, known as ‘dry cork screening,’ guarantees that almost all the tested corks are devoid of TCA and any other sensory anomalies.
Christiane Schleussner from Silver Oak cellars has recently demonstrated the dry cork screening process to her colleagues at the American Society for Enology and Viticulture. The process has also been highlighted in a write-up published in Vol 57, Issue 17 of the Journal of Agricultural and Food Chemistry. The article is available at http://pubs.acs.org/doi/abs/10.1021/jf901135p?prevSearch=cork%2Bsoak&searchHistory.
Schleussner revealed that Silver Oaks focused on developing a process to eliminate virtually all cases of corked-tainted large sized bottles and once it had proved the efficacy of the process, the company decided to share the process details with the industry.
Silver Oak and Twomey Cellars, its sister winery, possess one of the most rigorous protocols for quality control in the wine industry. These wineries have drastically decreased the occurrences of TCA in 750ml wine bottles by conducting random blind tests on hundreds of corks taken out from dozens of wine bottles lots. These lots are tracked using a number/letter sequence. Cork lots are retested by utilizing both group and individual cork soaks. However, Silver Oaks also wanted to check whether it was possible to decrease the error rate to zero for wine bottles of large formats.
Schleussner developed a dry soak process of non-destructive nature along with researchers at Cork Supply Portugal and Cork Supply USA. In this process, all large format corks are held in a sealed glass jar having 5 to 10 drops of distilled water for 48 hours. The molecules get volatized by the moist environment in the jar and then the corks are sniffed by a panel of experts. One hundred and thirty eight cork specimens, that is, six percent of the total corks, were discarded because of a mild to severe presence of unusual odors. These discarded corks were later analyzed chemically to detect the presence of TCA, resulting in the identification of 40 corks with very low levels of TCA, that is, 1.0 ppt (parts per trillion) or above.
Schleussner informed that the above process was highly labor intensive and required great commitment. Schleussner noted that the testing team was able to sniff only 200 corks at one stretch due to fatigue, taking a break after sniffing 50 corks. Despite this, dry screening, a non-destructive and clean process, was followed as it ensures the protection of wine in bottles of large formats, according to Schleussner.
Silver Oak Cellars has lately recorked all the large format wine bottles in its library. This library included all large format wine bottles from the 1970s to the 1993 vintage. Each wine bottle was uncorked by the winemaking team and sampled, followed by the rejection of wines with strange flavors and aromas. These bottles were recorked with a cork tested using the dry-soak process, refoiled, and then cleaned. Each bottle was replaced in its original wooden box or case. More than 2,500 bottles were checked and recorked. These bottles included three-, five-, six-, twelve- and eighteen-liters of Alexander Valley, and Bonny’s Vineyard Cabernet Sauvignon, and Silver Oak Napa Valley, and three-, five-, six-, twelve- and eighteen-liters of magnums.
Daniel Baron, Director of Winemaking, informed that the company had an exhaustive collection of library Silver Oak wines. According to Baron, besides being a valuable record of the company’s history, the library collection of wines delights customers who like old vintage wines in large format bottles. Baron revealed that the dry-soak process ensures Silver Oak to guarantee pure and flawless large format bottle wine from its old stock. Baron informed that these wines can be purchased from the tasting room of Silver Oak.