M. Beatriz P.P. Oliveira

HPLC/diode-array applied to the thermal degradation of trigonelline, nicotinic acid and caffeine in coffee

Abstract A simultaneous determination of trigonelline, nicotinic acid and caffeine was performed in samples of arabica and robusta coffees, before and after roasting at either different temperatures (160–240°C) or different periods of time exposures, in order to study their thermal degradation. A reverse-phase HPLC/Diode-array detector method was used. The results were compared with a model dry system roast of the compounds under study, individually and in mixture. The loss of trigonelline was strongly dependent upon the degree of roast and was associated with the formation of nicotinic acid. A slight decrease in caffeine was verified in both species. This study showed diversified behavior of the compounds when in their native form or in an artificial mixture, eliciting the chemical environmental influence. Rate constants for the chemical reactions at 240°C were determined.

A SYBR Green real-time PCR assay to detect and quantify pork meat in processed poultry meat products

Species identification in meat products has grown in interest in recent years since these foodstuffs are susceptible targets for fraudulent labelling. In this work, a real-time PCR approach based on SYBR Green dye was proposed for the quantitative detection of pork meat in processed meat products. For the development of the method, binary meat mixtures containing known amounts of pork meat in poultry meat were used to obtain a normalised calibration model from 0.1 to 25% with high linear correlation and PCR efficiency. The method revealed high specificity by melting curve analysis, being successfully validated through its application to blind meat mixtures, which confirmed its adequacy for pork meat determination. The fully applicability of the method was further demonstrated in commercial meat products, allowing verification of labelling compliance and identification of meat species in processed foods.

Castanea sativa by-products: a review on added value and sustainable application

Castanea sativa Mill. is a species of the family Fagaceae abundant in south Europe and Asia. The fruits (chestnut) are an added value resource in producing countries. Chestnut economic value is increasing not only for nutritional qualities but also for the beneficial health effects related with its consumption. During chestnut processing, a large amount of waste material is generated namely inner shell, outer shell and leaves. Studies on chestnut by-products revealed a good profile of bioactive compounds with antioxidant, anticarcinogenic and cardioprotective properties. These agro-industrial wastes, after valorisation, can be used by other industries, such as pharmaceutical, food or cosmetics, generating more profits, reducing pollution costs and improving social, economic and environmental sustainability. The purpose of this review is to provide knowledge about the type of chestnut by-products produced, the studies concerning its chemical composition and biological activity, and also to discuss other possible applications of these materials.

Chemical composition of wild and commercial Achillea millefolium L. and bioactivity of the methanolic extract, infusion and decoction

Medicinal plants used in folk medicine are being increasingly studied and used on pharmaceutical, food and nutraceutical fields. Herein, wild and commercial samples of Achillea millefolium L. (yarrow) were chemically characterized with respect to their macronutrients, free sugars, organic acids, fatty acids and tocopherols. Furthermore, in vitro antioxidant properties (free radicals scavenging activity, reducing power and lipid peroxidation inhibition) and antitumour potential (against breast, lung, cervical and hepatocellular carcinoma cell lines) of their methanolic extract, infusion and decoction (the most consumed forms) was evaluated and compared to the corresponding phenolic profile obtained by high performance liquid chromatography and mass spectrometry. Data obtained showed that the chemical profiles of wild and commercial samples, and also their methanolic extract, infusion and decoction were similar, varying only in the quantities found. Commercial yarrow have higher content of fat and saturated fatty acids, proteins, ash, energy value, sugars and flavonoids, while the wild sample revealed higher levels of carbohydrates, organic acids, unsaturated fatty acids, tocopherols and phenolic acids. The heterogeneity among the antioxidant and antitumour results of the samples and some low correlations with total phenolic compounds indicates that specific compounds, rather than the totality of them, are involved in the bioactive properties of samples.

Effect of gamma and electron beam irradiation on the physico-chemical and nutritional properties of mushrooms: a review.

The short shelf-life of mushrooms is an obstacle to the distribution and marketing of the fresh product. Thus, prolonging postharvest storage, while preserving their quality, would benefit the mushroom industry as well as consumers. There has been extensive research on finding the most appropriate technology for mushrooms preservation. Gamma, electron-beam and UV irradiation have been shown to be potential tools in extending the postharvest shelf-life of fresh mushrooms. Studies evaluating the effects of ionizing radiation are available mainly in cultivated species such as Agaricus bisporus, Lentinus edodes and Pleurotus ostreatus. This review comprises a comprehensive study of the effects of irradiation on physico-chemical parameters (weight, colour, texture and pH), chemical compounds including nutrients (proteins, sugars and vitamins) and non-nutrients (phenolics, flavonoids and flavour compounds), and on biochemical parameters such as enzymatic activity of mushrooms for different species and from different regions of the world.

Detection of Ara h 1 (a major peanut allergen) in food using an electrochemical gold nanoparticle-coated screen-printed immunosensor.

A gold nanoparticle-coated screen-printed carbon electrode was used as the transducer in the development of an electrochemical immunosensor for Ara h 1 (a major peanut allergen) detection in food samples. Gold nanoparticles (average diameter = 32 nm) were electrochemically generated on the surface of screen-printed carbon electrodes. Two monoclonal antibodies were used in a sandwich-type immunoassay and the antibody-antigen interaction was electrochemically detected through stripping analysis of enzymatically (using alkaline phosphatase) deposited silver. The total time of the optimized immunoassay was 3h 50 min. The developed immunosensor allowed the quantification of Ara h 1 between 12.6 and 2000 ng/ml, with a limit of detection of 3.8 ng/ml, and provided precise (RSD <8.7%) and accurate (recovery >96.6%) results. The immunosensor was successfully applied to the analysis of complex food matrices (cookies and chocolate), being able to detect Ara h 1 in samples containing 0.1% of peanut.

Optimization of matrix solid-phase dispersion extraction method for the analysis of isoflavones in Trifolium pratense.

A method based on matrix solid-phase dispersion (MSPD) has been developed for the determination of 12 isoflavones in Trifolium pratense L. Dried leaf samples were blended with C(18), placed in small columns and isoflavones extracted with dichloromethane-methanol. Analyses were performed by high performance liquid chromatography with diode array detection (HPLC-DAD) with 2-methoxyflavone as internal standard. Several dispersants, eluents and clean-up steps were tested during the optimization of the process in order to obtain the best selectivity and yields. Mean recoveries ranged from 70% to 119%, with relative standard deviations <18%. The limits of detection were between 0.006 mg/l for biochanin A and 0.108 mg/l for daidzin. The performance of the optimized method in real samples was compared with a conventional method based in solid-liquid extraction (SLE).

New Trends in Food Allergens Detection: Toward Biosensing Strategies

Food allergens are a real threat to sensitized individuals. Although food labeling is crucial to provide information to consumers with food allergies, accidental exposure to allergenic proteins may result from undeclared allergenic substances by means of food adulteration, fraud or uncontrolled cross-contamination. Allergens detection in foodstuffs can be a very hard task, due to their presence usually in trace amounts, together with the natural interference of the matrix. Methods for allergens analysis can be mainly divided in two large groups: the immunological assays and the DNA-based ones. Mass spectrometry has also been used as a confirmatory tool. Recently, biosensors appeared as innovative, sensitive, selective, environmentally friendly, cheaper and fast techniques (especially when automated and/or miniaturized), able to effectively replace the classical methodologies. In this review, we present the advances in the field of food allergens detection toward the biosensing strategies and discuss the challenges and future perspectives of this technology.

Dietary antioxidant supplements: benefits of their combined use.

Several dietary supplements claim medicinal benefits due to their composition in hydrophilic and lipophilic molecules, natural extracts or synthetic compounds with antioxidant properties. In the present work, the antioxidant activity of selected supplements taken in pills, capsules or infusions were studied either individually or combined. Linear discriminant analysis (LDA) was used to categorize the condensed formulations (pills and capsules), infusion bags and combined samples according with their antioxidant activity measured by radical scavenging activity, reducing power and lipid peroxidation inhibition using brain homogenates as models. AAF proved to have the highest antioxidant activity in all the assayed methods, either singly taken or included in mixtures. Furthermore, the mixtures containing this supplement revealed synergistic effects in 92% of the cases. The intake of antioxidant mixtures might provide some additional benefits.

Development and Validation of a Matrix Solid-Phase Dispersion Method to Determine Acrylamide in Coffee and Coffee Substitutes

The present study describes the development and validation of a new method based on a matrix solid-phase dispersion (MSPD) sample preparation procedure followed by GC-MS for determination of acrylamide levels in coffee (ground coffee and brewed coffee) and coffee substitute samples. Samples were dispersed in C(18) sorbent and the mixture was further packed into a preconditioned custom-made ISOLUTE bilayered SPE column (C(18)/Multimode; 1 g + 1 g). Acrylamide was subsequently eluted with water, and then derivatized with bromine and quantified by GC-MS in SIM mode. The MSPD/GC-MS method presented a LOD of 5 microg/kg and a LOQ of 10 microg/kg. Intra and interday precisions ranged from 2% to 4% and 4% to 10%, respectively. To evaluate the performance of the method, 11 samples of ground and brewed coffee and coffee substitutes were simultaneously analyzed by the developed method and also by a previously validated method based in a liquid-extraction (LE) procedure, and the results were compared showing a high correlation between them.