Control de los procesos de elaboración, calidad y trazabilidad del vinagre de Jerez

La calidad de un vinagre va a estar condicionada por la materia prima de partida, el sistema de acetificación seguido y el envejecimiento en madera al que pueda estar sometido. Para evaluar dicha calidad, es fundamental disponer de técnicas analíticas de control de las etapas esenciales mencionadas. Dichas técnicas, deben de suministrar la información relacionada con parámetros vinculados con las propiedades organolépticas indicadoras de la calidad del vinagre, como los componentes volátiles, así como cualquier otra información relacionada directamente con la calidad, como el espectro IR o los componentes polifenólicos. Además, no sólo por la influencia que pueda tener en las características organolépticas del vinagre, o por el riesgo en la salud pública que pueda suponer una elevada cantidad de residuos de productos fltosanitarios, sino también por su implicación en la obtención de la denominación de vinagre ecológico, cada vez más demandado y apreciado por el consumidor, es interesante contar con métodos sensibles para poder determinar los niveles de productos fitosanitarios en uvas, mostos, vinos y vinagres, que permitan el control de la trazabiidad del producto. Durante el desarrollo de la Tesis se han realizado diferentes trabajos de investigación, encaminados al control de los procesos de elaboración, calidad y trazabilidad del vinagre de Jerez. Se han desarrollado métodos analíticos para el control de los parámetros relacionados con la elaboración, así como los indicadores de la calidad y los implicados en la trazabilidad, del vinagre de Jerez. Además, se ha estudiado el comportamiento de parámetros relacionados con la elaboración del vinagre (acetificación) y inonitorización del proceso, así como de ensayos de mejoras del mismo. Del mismo modo se han propuesto ensayos alternativos al sistema de envejecimiento tradicional, con vistas a acelerar los procesos, manteniendo la calidad (empleo de virutas, microoxigenación, etc.). Un apartado importante del estudio realizado ha sido el control de la trazabilidad (de la cepa a la mesa) en la elaboración de vinagres de Jerez, controlando la materia prima, los sistemas de elaboración, envejecimiento y tratamientos finales, con vistas a garantizar el origen, la diferenciación y calidad y el caso particular de los vinagres ecológicos. También se ha comparado el vinagre de Jerez, con otros vinagres de elevada calidad, como el vinagre balsámico tradicional de Módena, en términos de su perfil aromático, teniendo en cuenta sus procesos de eavejecimiento similares. Para la realización de esta parte del estudio, se ha realizado una estancia de cuatro meses, en la Universidad de Bolonia (Italia)

Development of Head Space Sorptive Extraction Method for the Determination of Volatile Compounds in Beer and Comparison with Stir Bar Sorptive Extraction

A headspace sorptive extraction method coupled with gas chromatography-mass spectrometry (HSSE-GC-MS) was developed for the determination of 37 volatile compounds in beer. After optimization of the extraction conditions, the best conditions for the analysis were stirring at 1000 rpm for 180 min, using an 8-mL sample with 25% NaCl. The analytical method provided excellent linearity values (R-2 > 0.99) for the calibration of all the compounds studied, with the detection and quantification limits obtained being low enough for the determination of the compounds in the beers studied. When studying the repeatability of the method, it proved to be quite accurate, since RSD% values lower than 20% were obtained for all the compounds. On the other hand, the recovery study was successfully concluded, resulting in acceptable values for most of the compounds (80-120%). The optimised method was successfully applied to real beer samples of different types (ale, lager, stout and wheat). Finally, an analytical comparison of the optimised HSSE method, with a previously developed and validated stir bar sorptive extraction (SBSE) method was performed, obtaining similar concentration values by both methods for most compounds

Application of Microwaves as an Advanced Technique for the Development of Sherry Vinegar Macerated with Pineapple

This work proposes the elaboration of a product based on the maceration of Sherry Vinegar together with pineapple in order to extract certain volatile compounds that can be found in pineapples, giving a final product with new organoleptic properties and increased polyphenolic content. Maceration trials were carried out with the application of microwaves and ultrasound, which reduced the maceration time from the traditional three-day solid-liquid maceration to just a few minutes. In addition, through maceration, the total polyphenol index increased significantly with respect to unmacerated vinegar, and the volatile profile of the vinegars was significantly modified. The tasting scores placed the pineapple macerated vinegar sample obtained by traditional maceration in the first place with respect to pineapple aroma; however, the microwave extraction samples were better rated in terms of overall quality. It can be concluded that the application of extracting energies, such as microwaves, can be a viable alternative for the production of sherry vinegar macerated with pineapple

Biotechnological Processes in Fruit Vinegar Production

The production of fruit vinegars as a way of making use of fruit by-products is an option widely used by the food industry, since surplus or second quality fruit can be used without compromising the quality of the final product. The acetic nature of vinegars and its subsequent impact on the organoleptic properties of the final product allows almost any type of fruit to be used for its elaboration. A growing number of scientific research studies are being carried out on this matrix, and they are revealing the importance of controlling the processes involved in vinegar elaboration. Thus, in this review, we will deal with the incidence of technological and biotechnological processes on the elaboration of fruit vinegars other than grapes. The preparation and production of the juice for the elaboration of the vinegar by means of different procedures is an essential step for the final quality of the product, among which crushing or pressing are the most employed. The different conditions and processing methods of both alcoholic and acetic fermentation also affect significantly the final characteristics of the vinegar produced. For the alcoholic fermentation, the choice between spontaneous or inoculated procedure, together with the microorganisms present in the process, have special relevance. For the acetic fermentation, the type of acetification system employed (surface or submerged) is one of the most influential factors for the final physicochemical properties of fruit vinegars. Some promising research lines regarding fruit vinegar production are the use of commercial initiators to start the acetic fermentation, the use of thermotolerant bacteria that would allow acetic fermentation to be carried out at higher temperatures, or the use of innovative technologies such as high hydrostatic pressure, ultrasound, microwaves, pulsed electric fields, and so on, to obtain high-quality fruit vinegars

Effect of the type of acetic fermentation process on the chemical composition of prickly pear vinegar (Opuntia ficus-indica).

BACKGROUND: In several countries, the cactus plant (Opuntia ficus-indica (L). Mill) knows renewed attention due to its ecological, socio-economic, and environmental role. In this study, prickly pear vinegar was produced employing two types of acetification processes: surface and submerged culture. Both acetification processes were performed at different temperatures (30 °C, 37 °C, 40 °C) by using two different species of thermo-tolerant acetic acid bacteria (Acetobacter malorum and Gluconobacter oxydans). Polyphenols and volatiles compounds analyzed by UPLC/DAD and SBSE-GC/MS, respectively, were considered as the main variables to determine the effect of the acetification process on the quality of the vinegar. RESULTS: As a result, fifteen polyphenols and seventy volatile compounds were identified and quantified in the vinegar samples produced by both acetification processes. The results showed that the surface acetification method led to an increase in the concentration of phenolic components, which was higher than that in the submerged process. However, a significant increase of volatile compounds predominated by esters and acids was observed when submerged culture acetification was employed, whereas alcohols were predominant in surface culture vinegars. Moreover, the multivariate statistical analysis showed that the components that mostly contributed to the differentiation between all vinegar samples were the volatile compounds. CONCLUSION: It has been proved that prickly pear vinegar could be successfully produced at higher temperatures than usual, by employing thermo-tolerant bacteria, and that the type of acetification method significantly affects the final quality of the vinegar produced. This article is protected by copyright. All rights reserve

Production of prickly pear (Opuntia ficus-indica) vinegar in submerged culture using Acetobacter malorum and Gluconobacter oxydans: Study of volatile and polyphenolic composition

Prickly pear (Opuntia ficus-indica (L). Mill.) vinegar has been produced by submerged culture using scale laboratory fermenters at three acetification temperatures (30 ◦C, 37 ◦C, and 40 ◦C). Pure thermotolerant Acetic Acid Bacteria (AAB) which had been previously submitted to molecular identification by PCR–RFLP of the 16S–23S rDNA regions and 16S–23S ITS rDNA sequencing, were used. The AAB used were identified as Acetobacter malorum and Gluconobacter oxydans. The acetic fermentation achieved by A. malorum at 30 ◦C and 37 ◦C was more efficient, in terms of acidity, than that accomplished by G. oxydans. The chemical analysis revealed the presence of 85 individual volatile compounds and 17 polyphenolic compounds. The concentration of approximately half the volatile compounds was significantly affected by fermentation temperature, with clearly lower concentrations as temperature increased, whereas few significant differences were observed when comparing the vinegars produced by the two AAB species. Regarding phenolic compounds, significant increases were registered when temperature changed from 30 ◦C to 40 ◦C. Furthermore, the vinegars produced by A. malorum presented a greater concentration of phenolic compounds than those produced by G. oxydans

Influence of Different Bacteria Inocula and Temperature Levels on the Chemical Composition and Antioxidant Activity of Prickly Pear Vinegar Produced by Surface Culture

This work intends to determine the effect on the aroma profile, phenolic content and antioxidant activity of prickly pear vinegars produced by the surface culture at two different fermentation temperatures and using different acetic acid bacteria (AAB) inocula. Prickly pear wine was fermented at two temperature levels (30 and 37 degrees C) by using bacteria inocula containing Acetobacter, Gluconobacter or a mixture of bacteria isolated from Sherry vinegars. Eighty-five individual volatile compounds from different families and sixteen polyphenolic compounds have been identified. It was confirmed that the highest temperature tested (37 degrees C) resulted in a lower concentration of volatile compounds, while no significant effect on the vinegars' volatile composition could be associated with the AAB inoculum used. Contrariwise, the highest content of polyphenolic compounds was detected in those vinegars produced at 37 degrees C and their concentration was also affected by the type of AAB inoculum used. Prickly pear wine displayed greater antioxidant activity than juices or vinegars, while the vinegars obtained through the mixture of AAB from Sherry vinegar showed higher antiradical activity than those obtained through either of the two AAB genera used in this study. It can be therefore concluded that, although the volatile content of vinegars decreased when fermented at a higher temperature, vinegars with a higher content in polyphenols could be obtained by means of partial fermentations at 37 degrees C, as long as thermotolerant bacteria were employed

The impact of ultrasound, micro-oxygenation and oak wood type on the phenolic and volatile composition of a Tempranillo red wine

The accelerated ageing of a Tempranillo red wine has been studied at pilot scale through the combined application of ultrasound, micro-oxygenation and different oak wood type chips (American, French and Spanish). The phenolic and volatile content of the aged samples and their sensory profiles have been determined. The wine samples that had been aged using micro-oxygenation, French or American oak chips, and ultrasound revealed to be similar in terms of polyphenols to those wines that had been aged without implementing this last accelerating technique. Ageing time, with a high extraction kinetics, was the most significant variable with regard to their polyphenol content. In terms of volatiles, Spanish and French oak wood wine samples showed a similar behaviour closely associated to ageing time, while American oak wood achieved a rather low enrichment in volatile constituents, resulting in a poor sensory profile of the final wines, which was particularly poor in the case of ultrasound aged wines

Influence of Two Different Cryoextraction Procedures on the Quality of Wine Produced from Muscat Grapes

Freezing grapes is a winemaking technique known as cryoextraction that intends to modify the composition of the final wines. The changes that take place in the frozen grapes facilitate the transfer of certain compounds from the grape skins into the musts because of the grape's unstructured tissues. For this study, the white grape variety Muscat of Alexandria was selected. Two different cryoextraction procedures have been analyzed as follows: (i) Ultrafast freezing, and (ii) liquid nitrogen freezing. The wines obtained using liquid nitrogen freezing exhibited higher levels of terpenoids, as well as higher levels of hydroxylic compounds and fatty acids than both the wines obtained through traditional methods and ultrafast freezing wines. In any case, both freezing techniques produced wines of a more intense aroma compared with those wines obtained by traditional methods. In fact, liquid nitrogen freezing produced the wines with the most intense aroma and were the best valued by the tasting panel

Characterization and Di erentiation of Spanish Vinegars from Jerez and Condado de Huelva Protected Designations of Origin

Thirty one Jerez vinegar samples and 33 Huelva vinegar samples were analyzed for polyphenolic and volatile compound content in order to characterize them and attempt to di erentiate them. Sixteen polyphenolic compounds were quantified by means of ultraperformance liquid chromatography method with diode array detection (UPLC–DAD), and 37 volatile compounds were studied by means of stir bar sorptive extraction–gas chromatography–mass spectrometry (SBSE–GC–MS). Spectrophotometric CIELab parameters were also measured for all the samples. The results obtained from the statistical multivariate treatment of the data evidenced a clear di erence between vinegars from the two geographical indications with regard to their polyphenolic content, with Jerez vinegars exhibiting a greater phenolic content. Di erentiation by the volatile compound content was, however, not so evident. Nevertheless, a considerable di erentiation between the two groups of vinegars based on their volatile fraction was achieved. This may bring to light the grape varieties and geographical factors that have a clear influence on such di erences