Identifier: TDX:784
Authors: Martí Borras, Maria Pilar
Abstract:
Aroma is an important factor in quality control and quality assurance of foods, but in wines and in alcoholic beverages, this factor is possibly the most important. Wine aroma analysis is not an easy task to perform because aroma is composed of complex mixtures of hundreds of volatile compounds with different sensory and chemical properties and, moreover, the concentration levels of most of them are very low.The research work carried out in this thesis lay in the study and the characterisation of wine aroma by two very important techniques in this field: gas chromatography olfactometry (GCO) and electronic nose. GCO is a very useful technique in the study of wine aroma that makes it possible to identify, among all the volatile compounds, the odorous volatile compounds of the sample by using the human nose as chromatographic detector. The most important study carried out in this thesis by GCO was the development of a method for the characterisation of wine aroma that uses the solid-phase microextraction technique (SPME) as a sample pre-treatment technique. This method evaluates the aromatic intensity of the odorous compounds by a new approach of the aroma extract dilution analysis (AEDA) technique.Quality control of food has been carried out by sensory analysis since immemorial time. However, sensory analysis by a panel of experts is a costly process for industries because it requires trained people who can work for only relatively short periods of time. The purpose of the development of electronic noses was to achieve an instrument that could mimic the human sense of smell and provide rapid sensory information (e.g., differences and similarities among samples, presence of aromatic defects, etc.). Food analysis is probably the field in which the greatest number of applications using electronic noses have been developed. However, in wine and alcoholic beverage research, few studies have been performed with this type of instrumentation because of the problems that ethanol causes in the gas sensors which compose most of the electronic noses. In this thesis, the application of a mass spectromety (MS) based electronic nose to wine analysis has been studied because, a priori, ethanol does not interfere in the analysis by this instrument. Some applications have also been carried out with alcoholic beverages as sugar cane spirits and brandies. The purpose of these studies was to evaluate the potential application of this technique in the quality control of this kind of samples. In wine analysis, this technique was successfully applied to differentiate and classify wines according to their origin, variety and ageing. It was also evaluated its capacity in the monitoring of the aroma profile evolution during grape ripening and alcoholic fermentation in order to study the potential use of this technique in the control of these processes. Other application studied was the determination of compounds with an important sensory impact, such as the off-flavours, by multivariate calibration. Two methods were developed to determine 2,4,6-trichloroanisole which is the main responsible of the aromatic defect known as 'cork taint'. In the quality control of sugar cane spirits, a method to determine the ageing time of these samples in oak wood barrels was developed. It was also studied the correlation between the electronic nose data and the intensity of several odour attributes evaluated by a panel of experts in a sensory analysis of the spirits.
Repositori URV