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Rapid spectrophotometric methods as a tool to assess the total phenolics and antioxidant potential over grape ripening: a case study of Madeira grapes

Publication . Perestrelo, Rosa; Suilva, Catarina; Silva, Pedro; Câmara, José Sousa

The aim of this study was to improve the knowledge of phenolic content and antioxidant potential during ripening of different grape varieties (Malvasia, Sercial and Tinta Negra) used to produce Madeira wine. Rapid spectrophotometric methods were selected to obtain this information, since these methods could be used as a routine analytical procedure, being easy, simple, rapid, and cost-effective. A significant correlation was observed between total phenolic content and antioxidant capacity for all grape varieties under study, which suggests that phenolics either alone or in combination are responsible for the grapes antioxidant capacity. Our findings showed significant differences (p < 0.05) for phenolic content and antioxidant capacity for all the studied grape varieties. Sercial grapes showed the highest values of phenolics and antioxidant capacity. Moreover, grape ripening stages revealed a significant impact on grapes phenolic content and antioxidant capacity. This information could be used by viticulturists and winemakers to improve and define Vitis vinifera L. grapes harvest management in order to maximize its bioactive potential.

2018Journal article

Restricted access

Fingerprint targeted compounds in authenticity of sugarcane honey: an approach based on chromatographic and statistical data

Publication . Silva, Pedro; Silva, Catarina L.; Perestrelo, Rosa; Nunes, Fernando M.; Câmara, José S.

ugarcane honey (SCH) is a black syrup recognized by its excellent quality, being produced in Madeira Island using the regional sugarcane cultivars and following a traditional and peculiar manufacturing and storage processes. However, some low-quality commercial products have been labeled as SCH but do not respect its criteria, revealing the need of develop powerful strategies in order to detect and prevent adulterations. The knowledge of furanic derivatives (FDs) profile, produced during browning reactions that occurs during food processing and storage, emerged as a promising strategy in food quality and fraud prevention. Therefore, the aim of this study was to establish the FDs profiling of typical SCH produced by certified and non-certified producers, in different geographical regions (Madeira and Brazil), based on microextraction by packed sorbent (MEPS) combined with ultra-high performance liquid chromatography (UHPLC) as a useful approach to define its typicality and authenticity. These parameters are defined through the differentiation and discrimination of FDs profiles among other sugarcane-derived products using multivariate statistical analysis (ANOVA with post-hoc Tukey, principal components analysis, partial least square, linear discriminant analysis and hierarchical clustering). The results demonstrated that SCH samples from non-certified producers present the highest levels of FDs. In addition, SCH samples from Brazil present higher levels of FDs than samples from Madeira region. The obtained results revealed that the proposed approach is a valuable strategy to establish the typicality of SCH, ensuring its quality, authenticity, safety control and a useful support regarding the application of SCH from Madeira Island to EU certification.

2018Journal article

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Unraveling Vitis vinifera L. grape maturity markers based on integration of terpenic pattern and chemometric methods

Publication . Perestrelo, Rosa; Silva, Catarina; Silva, Pedro; Câmara, José S.

The current research attempts to provide an alternative tool for grape maturity measurement related to the wine composition since, the classical parameters (weight grape berries, sugar content, titratable acidity), commonly used in the winemaking industry, do not provide any sensorial information. In this context, the evolution of terpenic compounds (TC) during ripening of four V. vinifera L. grape varieties - Bual, Malvasia, Sercial (white grapes) and Tinta Negra (red grapes), was investigated, in addition to the establishment of terpenic pattern, using headspace solid phase microextraction (HS-SPME) combined with GC–MS. Using the optimal analytical conditions were identified 62 TC in the investigated V. vinifera L. grapes. The integration of chromatographic and chemometric data provides a powerful strategy to identify potential maturity markers. The maximum potential of mono- and sesquiterpenic compounds was reached at maturity, whereas the highest levels of norisoprenoids were observed at véraison. Partial Least Squares Regression (PLS-R) was employed to describe the relationship between classical parameters and TC. Based on PLS-R models, three monoterpenic (linalool, α-terpineol, carvomenthol), one sesquiterpenic (bicyclogermacrene) and two norisoprenoids compounds (vitispirane I, β-damascenone) could be used to define the optimum harvest date. The obtained results represent a very important tool to support, in an objective way, the winemakers decision for long-term strategic planning based on the sensory potentialities of grape varieties and consequently improving the excellence of Madeira wine.

2018Journal article

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Differentiation of fresh and processed fruit juices using volatile composition

Publication . Perestrelo, Rosa; Silva, Catarina; Silva, Pedro; Medina, Sonia; Câmara, José

In the current study, a comprehensive approach based on headspace solid-phase microextraction (HS-SPME), combined with gas chromatography-quadrupole mass spectrometry (GC-qMS), was used to establish the volatile signature of fresh and processed fruit juices, obtained from the same batch of grapes, red fruits, orange, pear, and apple. This is a powerful tool for evaluating the impact of the production process on the volatomic pattern of fruit juice. A total of 169 volatile organic compounds (VOCs) belonging to different chemical groups were identified. Esters, carbonyl compounds, terpenoids, and alcohols are the major chemical groups in the investigated fruit juices. However, their contribution to the total volatile profile varied. Special attention should be paid to processed fruit juices to avoid the possible deleterious effects associated with the formation of furanic compounds (e.g., heat treatment), since their furanic content was significantly higher in comparison to that of fresh fruit juices. The knowledge obtained in the current study will allow for the introduction of modifications to the process involved in processing juice, which will improve the organoleptic characteristics of processed juices, contributing to a better acceptance by consumers. Furthermore, more assays should be performed to assess the effect of harvests, geography, and agronomy on the volatile profile of juices.

2019Journal article

Open access

Comparison of high-throughput microextraction techniques, MEPS and μ-SPEed, for the determination of polyphenols in baby food by ultrahigh pressure liquid chromatography

Publication . Casado, Natalia; Perestrelo, Rosa; Silva, Catarina L.; Sierra, Isabel; Câmara, José S.

In this study, two different high-throughput microextraction techniques, microextraction by packed sorbents (MEPS) and micro solid phase extraction (μ-SPEed®), were evaluated and compared, regarding the performance criteria, for the isolation of polyphenols from baby foods prior to their determination by ultrahigh pressure liquid chromatography (UHPLC). To achieve the best performance, influential parameters affecting extraction efficiency (including type of sorbent, number of extraction cycles, pH, elution solvent and elution volume) were systematically studied and optimized. To enable an effective comparison, selectivity, linear dynamic range, method detection (LODs) and quantification limits (LOQs), accuracy, precision and extraction yields, were determined and discussed for both techniques. Both methods provided the analytical selectivity required for the analysis of polyphenols in baby foods. However, μ-SPEed® sample treatment in combination with UHPLC-PDA has demonstrated to be more sensitive, selective and efficient than MEPS. Appropriate linearity in solvent and matrix-based calibrations, very low LODs and LOQs, ranging between 1.37 and 13.57 μg kg-1 and 4.57 - 45.23 μg kg-1, respectively, suitable recoveries (from 67 to 97%) and precision (RSD values < 5%) were achieved for the selected analytes by μ-SPEed®/UHPLC-PDA. Finally, the validated methodologies were applied to different commercial baby foods. Gallic acid, chlorogenic acid, epicatechin, ferulic acid, rutin, naringenin and myricetin are the most dominant polyphenols present in the studied baby food samples. The proposed methodology revealed a promising approach to evaluate the nutritional quality of this kind of products.

2019Journal article

Restricted access