M.L. González-Miret

Influence of prefermentative cold maceration on the color and anthocyanic copigmentation of organic Tempranillo wines elaborated in a warm climate.

The stabilization of red wine color by the copigmentation phenomenon is a crucial process that does not always proceed favorably under natural conditions during the first stages of vinification. The impact of the prefermentative cold maceration technique on the phenolic composition and magnitude of the copigmentation level of organic Tempranillo wines elaborated in a warm climate have been studied as an enological alternative to the traditional maceration for obtaining highly colored wines. Tristimulus colorimetry was applied to study the color of wines during vinification, and a high-performance liquid chromatography (HPLC) procedure was used for the analysis of phenolic compounds. Spectrophotometric and colorimetric analyses were also performed to evaluate the copigmentation level of the wines. Significant chemical and color differences were found depending on the maceration technique applied. Prefermentative cold macerated wines were richer in those compounds accounting directly for the color of red wine (anthocyanins) and those involved in anthocyanin stabilization through copigmentation reactions (phenols), which was in accordance with the higher copigmentation degree and darker, more saturated and vivid bluish colors. The evaluation of the copigmentation based on colorimetric parameters in the CIELAB color space showed that prefermentative cold maceration caused greater effectiveness of copigmentation than traditional maceration since it induces more important and hence more easily perceptible color changes.

Feasibility Study on the Use of Visible–Near-Infrared Spectroscopy for the Screening of Individual and Total Glucosinolate Contents in Broccoli

The potential of visible-near-infrared spectroscopy to determine selected individual and total glucosinolates in broccoli has been evaluated. Modified partial least-squares regression was used to develop quantitative models to predict glucosinolate contents. Both the whole spectrum and different spectral regions were separately evaluated to develop the quantitative models; in all cases the best results were obtained using the near-infrared zone between 2000 and 2498 nm. These models have been externally validated for the screening of glucoraphanin, glucobrassicin, 4-methoxyglucobrassicin, neoglucobrassicin, and total glucosinolates contents. In addition, discriminant partial least-squares was used to distinguish between two possible broccoli cultivars and showed a high degree of accuracy. In the case of the qualitative analysis, best results were obtained using the whole spectrum (i.e., 400-2498 nm) with a correct classification rate of 100% in external validation being obtained.

Validation of parameters in HACCP verification using univariate and multivariate statistics. Application to the final phases of poultry meat production

Abstract For Hazard Analysis and Critical Control Points (HACCP) systems verification in food industries, the selection of parameters that offer significant information about control system at each production stages is necessary. Total Count (TC), Pseudomonas (PS), Enterobacteriaceae (EB) and Staphylococcus aureus (ST) are organisms frequently measured on carcasses at slaughters. Their inclusion in HACCP system can be assessed by means of statistical techniques. Univariate and multivariate statistical methods are of great importance in order to identify most useful variables. In this study the use of these microbiological parameters in verification of refrigeration, and cutup and packaging operations has been evaluated. It has established the usefulness of these variables using statistical techniques. It makes clear the most discriminant effect of EB and TC to establish differences between the stages studied in this process.

Changes in antioxidant capacity and colour associated with the formation of β-carotene epoxides and oxidative cleavage derivatives

In this study HPLC-DAD-MS/MS was applied for the identification of compounds derived from (all-E)-β-carotene following epoxidation and oxidative cleavage. The consequences on the CIELAB colour parameters and antioxidant capacity (AC) were also evaluated. Five apocarotenoids, three secocarotenoids, seven Z isomers and two epoxides were detected as a result of the oxidative cleavage. Four epoxides and three Z isomers were detected as a consequence of the epoxidation reaction. Some compounds were detected for the first time as a result of oxidation reactions. Both treatments led to a marked decrease in b(∗) and Cab(∗) values, indicating that these colour parameters can be used for the rapid assessment of β-carotene oxidation. The oxidative cleavage of β-carotene resulted in increased capacity to both scavenge ABTS(+) and quench singlet oxygen. These results suggest that the study of the AC of these oxidative derivatives and their possible usefulness as food ingredients deserves further attention.

A novel and enhanced approach for the assessment of the total carotenoid content of foods based on multipoint spectroscopic measurements.

We have devised a more sensible approach to estimate the carotenoid content of orange juices, which can be regarded as a model system of food with intricate carotenoid pattern. For this purpose spectroscopic information at several wavelengths and spectra of the juices and not from their carotenoid extracts were considered, such that more accurate and rapid quantitative assessments can be achieved. The wavelengths proposed on the basis of the characteristic vector method were 420, 455, 515, 545 and 610nm or 420, 445, 510, 545 and 605nm, depending on the measurement conditions. The correlations between the carotenoid content and the reflectances at these wavelengths were very good (R=0.94 and 0.90, respectively). Additionally, it was demonstrated that the colour of the juices could be assessed with very good accuracy considering them. Due to its simplicity and rapidity, this method is intended to facilitate the quality control of the carotenoid content of foodstuffs in the industry and/or in the field.

Instrumental assessment of the sensory quality of juices

: Over the years, the application of analytical chemistry in the wine industry has done much to improve the level and consistency of wine sensory quality. Nowadays, instrumental analysis, particularly chromatography and spectroscopy, is applied to all aspects of wine production, from vineyard to bottle. Key sensory parameters or components are determined directly – or indirectly using rapid methods such as Fourier transform infrared (FTIR) spectroscopy and chemometric/statistical analysis. The structures of many complex sensory components have been elucidated by techniques such as mass spectrometry (MS) and nuclear magnetic resonance spectroscopy, the former usually being combined with gas chromatography (GC) or high performance liquid chromatography (HPLC). Over the past few decades, sample preparation techniques, especially extractive/focusing methods, have greatly facilitated instrumental analysis.

Raman spectroscopy for analyzing anthocyanins of lyophilized blueberries

The non-destructive nature of spectroscopy as a modern analytical method for food analysis is particularly attractive for rapid quality checks. This paper shows how Raman spectroscopy can be used for assessing the nutraceutic properties of lyophilized blueberries which were selected at different ripeness. The Raman spectra of powder samples were processed together with their reference data by means of Principal Component Analysis for classifying the ripeness. Then, Partial Least Square regression was applied, so as to create predictive models for quantifying the total content of anthocyanins as well as their sub-groups.

Near-infrared spectroscopy and pattern-recognition processing for classifying wines of two Italian provinces

This paper presents an experiment making use of the near-infrared spectrum for distinguishing the wines produced in two close provinces of Abruzzo region of Italy. A collection of 32 wines was considered, 18 of which were produced in the province of Chieti, while the other 14 were from the province of Teramo. A conventional dual-beam spectrophotometer was used for absorption measurements in the 1300-1900 nm spectroscopic range. Principal Component Analysis was used for explorative analysis. Score maps in the PC1-PC2 or PC2-PC3 spaces were obtained, which successfully grouped the wine samples in two distinct clusters, corresponding to Chieti and Teramo provinces, respectively. A modelling of dual-band spectroscopy was also proposed, making use of two LEDs for illumination and a PIN detector instead of the spectrometer. These data were processed using Linear Discriminant Analysis which demonstrated satisfactory classification results.

Optical spectroscopy and pattern recogition techniques for discriminating and classifying Scotch whiskies

The present study shows how optical spectroscopy can be innovatively used as a rapid and non-destructive tool to differentiate distinctive single malt Scotch whiskies with respect to commercial-grade blends, and for their classification according to the region of production. Absorption and fluorescence spectroscopy were combined with multivariate data analysis so as to build a discriminating map. The map showed that the clusters representing the single malt whiskies from selected distilleries were sharply separated from the cluster grouping the other whiskies of commercial-grade. Moreover, the cluster of single malt whisky was split into two subgroups, representing samples from two main macro-areas, the islands and the highlands, respectively.

Application of imaging techniques for the evaluation of phenolic maturity of grape seeds

espanolLa calidad del vino depende en gran medida del estado en que se encuentren los diferentes componentes de la uva en el momento de la recoleccion y, en este sentido, las semillas afectan directamente a su astringencia, asi como a la estructura y estabilidad del color del vino. En el presente trabajo se han evaluado semillas de uva de diferentes variedades aplicando distintas tecnicas de analisis de imagen. En todos los casos se han desarrollado metodologias que implican la minima preparacion de muestra y la maxima rapidez del metodo, con el objeto de poder sustituir, en la medida de la posible, el analisis quimico, que suele suponer largos y tediosos procesos que impiden un seguimiento rapido de la maduracion. La metodologia propuesta para la medicion y evaluacion del color y el espectro infrarrojo cercano ha dado resultados satisfactorios en la estimacion del estado de madurez de las semillas de uva, y ha sido util para establecer etapas de maduracion a partir de sus propiedades opticas. EnglishQuality of wine depends fundamentally on the condition of the components of grapes at the moment of harvest. In this respect, their seeds directly affect to structure, astringency, stability, and indirectly to colour of wine. In this work, the grape seeds have been evaluated by techniques of image analysis. In all cases, the methodology was developed trying to entail the minimum sample preparation and maximum quickness of the method, and as far as possible, substitute the chemical analysis that usually involves long and tedious processes that hamper monitoring of ripening in a rapid way. The proposed methodology for measuring and evaluating colour and near infrared spectrum has yielded satisfactory results for estimating the ripening of grape seeds, and it has been useful for establishing stages of ripeness from their optical features.