# Influence of Oak Chips and Oak Barrel Ageing on Volatile Profile in Chardonnay Wine of Romania
## 4 Discussion
### Volatile Compounds in Chardonnay Aged Wine  
The method of ageing influences the amount of chemical compounds at different times of the process. During ageing, specific compounds are transferred to wines as a result of prolonged contact with oak chips [30]. When employing the oak alternatives, the main factors to be considered are the amount and surface area (shape and size) of the materials used. In this respect, chip and barrel-aged wines differ in their content of a range of volatiles, such as vanillin, guaiacol or furfurals [3]. [PERSON] et al. [44] states that young unoaked Chardonnay wines can be discriminated (with 74% correctly classified) by using the following eight volatile compounds: 2-phenylethanol, decanoic acid, diethyl succinate, ethyl hexanoate, ethyl decanoate, ethyl octanoate, hexyl acetate and 1-propanol. In general, alcohols can be the product of sugar fermentation and amino acid metabolism through yeasts. Higher alcohols have a significant impact on the fruity aroma of wine [45]. The major alcohols (iso-butanol, isopentyl alcohol and 2-phenylethanol) varied both depending on the time and type of ageing with different t trends. However, at the end of the maturation period, the major alcohol concentrations were higher, regardless of the method. Also, the concentrations of the minor alcohols group were dependent on ageing time and method. The non-toasted barrel ageing method favored the concentration of hexanol, which supplied a leafy and grassy note to wine samples [31]. Generally, 2,3-butanediol is not expected to affect the sensory qualities of wine appreciably, but some authors [46] noted a bitter taste in variants with a concentration over 700 mg/L of this compound in wines samples. In our research, the higher concentration of 2,3 butanediol in the BAR variant wine sample could be explained by enzymatic reduction of diacetyl and acetoin in this compound under malolactic fermentation which could occur in barrels [47]. Overall, the time and method of ageing, significantly influenced the concentration of major and minor alcohols in wine samples, with higher amount for the variant aged in the non-toasted barrel. Increased amounts of higher alcohols during ageing can be caused by acid-catalyzed ester hydrolysis [48]. The esters chemical family contribute to the fruity character of wines and are one of the predominant chemical groups [49]. In this research, the impact of ageing duration and method on the Chardonnay wines concentration of esters was investigated. Most of them exhibited concentrations above their olfactory perception threshold, providing the wine with pear, apple, pineapple and/or floral notes [30; 31]. During ageing, the esters had interesting trends; most of them have increased in concentration compared with the control wine and only hexyl acetate and trimethylene acetate decreased after ageing. Ethyl fatty acid esters are considered to be very important for the aroma of wines. The concentration of ethyl lactate progressively increases during malolactic fermentation [46]. This result is beneficial for the wine bouquet due to its fruity, buttery or creamy aromas, also contributing to the sensations of roundness in the mouth [46; 50]. Overall, the ageing process, regardless of the method, slightly increased the amount of esters. Even more, after 1, 2 and 3 months of ageing, the concentrations of esters were nearly similar for the same time period of ageing among methods of ageing. The fatty acids chemical group of volatile compounds is produced by yeast and bacteria during fatty acid metabolism. Volatile fatty acids can contribute to the complexity of the wine bouquet even if they are present under threshold levels. They have a negative effect on wine aroma when above their thresholds [51]. Some acids, such as iso-butyric acid and decanoic acid are not associated with wine quality, but they play an important role in the complexity of the aroma [52].