Authentication of vegetable oils.

Authenticity of vegetable oils continues to be a challenge and the target of many studies. Consumers expectancy on healthier products that conform to the labelled information, and the vast amount of legislation a bout the correct characterisation and classification of vegetable oils have boosted a number of scientific works on this subject. Analytical t echniques to face this challenge are, at least, as manifold as ar e the ways of adulteration, ranging from classical determination of chemical parameters to highly sophisticated instrumental and molecular biology techniques. Rather than being an exhaustive revision of published works, the aim of the present chapter is to summarise: i) the analytical methods used in the determination of the main oil components such as fatty acids, triacylglycerols, phytosterols, tocopherols and tocotrienols, phenolic compounds, pigments and volatile compounds, emphasising their importance in authenticity evaluation; ii) the alternative tech niques based on spectroscopic

New domestic processing methods: effect on potato nutritional composition

Background and objectives: Potatoes nutritional and bioactive features are influenced by thermal processing conditions, defining its nutritional composition and health impact. Consumers seek increasingly for faster domestic cooking methods, such as microwave cooking in alternative to current frying or baking. Also, several devices are being commercialized for healthier frying simulation, without a documented characterization of the final processed food nutritional data. Thus, this study aimed to assess and compare the influence of these domestic processing methods on the quality of potatoes processed with olive oil. Methods: Potatoes were processed by frying, baking, microwave and a low-fat frying device, with equivalent shape and olive oil amounts, except frying. Samples were evaluated for crude fat, fatty acid composition, vitamin E, total carotenoids and total phenols. Results: Microwave cooked potatoes presented similar fat contents as standard frying, higher than those achieved by baking or with the low-fat frying device tested, but the fatty acid composition was similar. Vitamin E loss was comparatively higher after frying but no significant differences were found for total carotenoids. Potatoes phenolic compounds were partially loss during cooking, being apparently higher after baking. Conclusions: The distinct nutritional features obtained highlight for the importance of detailing the food compositional tables regarding each processing method, including the “new” domestic methodologies, increasingly used by consumers

Quantification of tocopherols and tocotrienols in Portuguese olive oils using HPLC with three different detection systems

Three different HPLC detection systems were compared for the determination of tocopherols and tocotrienols in olive oil: fluorescence and diode array connected in series, ultraviolet, and evaporative light scattering. The best results were obtained with the fluorescence detector, which was successfully applied in the quantification of tocopherols and tocotrienols in 18 samples of Portuguese olive oils. To support the validity of the method, the parameters evaluated were linearity, detection limits, repeatability, and recovery. All of the studied samples showed similar qualitative profiles with six identified compounds: R-T, -T, γ-T, δ-T, R-T3, and γ-T3. R-Tocopherol (R-T) was the main vitamin E isomer in all samples ranging from 93 to 260 mg/kg. The total tocopherols and tocotrienols ranged from 100 to 270 mg/kg. Geographic origin did not seem to influence the tocopherol and tocotrienol composition of the olive oils under evaluation

Identification of leaf volatiles from olive (Olea europaea) and their possible role in the ovipositional preferences of olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae)

The olive fly, Bactrocera oleae (Rossi), is a monophagous pest that displays an oviposition preference among cultivars of olive (Olea europaea L.). To clarify the oviposition preference, the olive leaf volatiles of three olive cultivars (Cobrançosa, Madural and Verdeal Transmontana) were assessed by headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) at six different periods of olive fruit maturation and degrees of infestation. A total of 39 volatiles were identified, mainly esters and alcohols, with a minor percentage of aldehydes, ketones and terpenic compounds, including sesquiterpenes. At sampling dates with higher degrees of infestation, cv. Cobrançosa had, simultaneously, significantly lower infestation degrees and higher volatile amounts than the other two cultivars, with a probable deterrent effect for oviposition. The green leaf volatiles (GLVs) (Z)-3-hexen-1-ol and (Z)-3-hexen-1-ol acetate) were the main compounds identified in all cultivars, together with toluene. The abundance of GLVs decreas ed significantly throughout maturation, without significant differences among cultivars, while toluene showed a general increase and positive correlation with olive fly infestation levels. The results obtained could broaden our understanding of the roles of various types and amounts of olive volatiles in the environment, especially in olive fly host selection and cultivar preference.The authors are grateful to the Portuguese Foundation of Science and Technology for financial support through the project EXCL/AGR-PRO/0591/2012 “Olive crop protection in sustainable production under global climatic changes: linking ecological infrastructures to ecosystem functions”. R. Malheiro thanks FCT, POPH-QREN and FSE for PhD grant (SFRH/BD/74675/2010). This manuscript is part of Ricardo Malheiro PhD Thesis.info:eu-repo/semantics/publishedVersio

Classification PDO olive oils on the basis of their sterol composition by multivariate analysis

The sterol compositions (GLC/FID/capillary column) of monovarietal olive oils (51 samples) from the most important cultivars of northeastern Portugal (Cvs. Cobranc¸osa, Madural and Verdeal Transmontana) and 27 commercial samples of olive oils with protected denomination of origin (PDO) from the same region and cultivars were evaluated. Δ-sitosterol, Δ5-avenasterol and campesterol were the most representative sterols. Cholesterol, stigmasterol, clerosterol and Δ7-stigmastenol were also found in all samples. All studied samples respected EC Regulation N. 2568, and in all cases total sterols were remarkably higher than the minimum limit set by legislation, ranging from 2003 to 2682 mg/kg. Results were analysed with the help of several statistical techniques, including reduction of dimensionality by principal component analysis with cross-validation of the number of components, followed by the use of canonical variate predictive biplots for model development and canonical variate interpolative biplots for approximate classification of monovarietal and PDO olive oils. These biplots proved to be a very interesting solution in the present case study, overcoming the problems of interpretation and classification that arise whenever different multivariate analyses are coupled together

A novel strategy of acrylamide mitigation in fried potatoes using asparaginase and high pressure technology

The potentiality of high pressure processing (HPP) to possibly enhance diffusion of asparaginase into raw potato sticks, and consequently on reduction of acrylamide levels in fried potatoes was evaluated. Raw potato sticks were immersed in asparaginase (10,000 ASNU/L) and immediately subjected to 0.1, 100, 200 and 400 MPa for 5 min, with total enzymatic reaction times of 5, 10 and 20 min and room temperature. Pressurized raw potato sticks became softer, more flexible, and required lower energy for cutting (up to 47% less); the roughness of potato surface and moisture content were slightly reduced; and the concentration of soluble solids in the exterior solutions increased, indicative of a leaching effect. Due to changes induced by asparaginase and/or HPP on raw potatoes, fried potatoes exhibited higher weight loss after frying, and higher hardness (crispness). The combined treatment with asparaginase and HPP showed to reduce acrylamide levels by 26 -47%, while with asparaginase or HPP alone there was no significant reduction.publishe

Advances in isoflavone profile characterisation using matrix solid-phase dispersion coupled to HPLC/DAD in medicago species

Analytical methods used in phytochemistry analysis are limited by the sample preparation step, which should ideally be fast, accurate, ecofriendly and achievable using low quantities of the sample. Matrix solid-phase dispersion (MSPD) may be a good alternative for combining extraction and purification procedures, thereby reducing the indicated limitations. Objective-Applying an MSPD extraction procedure coupled to high-performance liquid chromatography diode-array detection (HPLC/DAD) as an alternative methodology to evaluate isoflavone profiles. Methods-Isoflavone profiles were determined for the leaves of nine species of Medicago in the late flower phenological stage (one or more nodes with 50% open flowers, no seed pods). Extraction was performed following MSPD, and isoflavone profiles were characterised using HPLC/DAD. The quantified amounts were compared with previous results in different species commonly recognised as good sources of isoflavones. Results-Formononetin was the major isoflavone in most species, except M. polymorpha and M. truncatula. The isoflavone amounts were significantly different among the assayed species, with M. orbicularis and M. arabica as the major isoflavone sources, while M. rigidula presented the lowest contents. Furthermore, the detected differences allow electing the best species as a primary source of a specific isoflavone. Conclusion-The MSPD allowed good extraction efficiency, reproducibility and recovery. Some of the species showed relevant isoflavone contents, even when compared with acknowledged plant sources such as soy or red clover. To the best of our knowledge the results presented are reported for the first time in these species.T. Visnevschi-Necrasov and João C.M. Barreira are grateful to ‘FCT - Fundação para a Ciência e a Tecnologia’ for their grants (BD/ 31734/2006 and SFRH/BPD/72802/2010, respectively). S.C. Cunha is grateful to ‘POPH-QREN - Tipologia 4.2, Fundo Social Europeu e Fundo Nacional MCTES’.info:eu-repo/semantics/publishedVersio

Medicago spp. as potential sources of bioactive isoflavones: Characterization according to phylogenetic and phenologic factors

A high variety of plant species are often proposed as potential natural sources of specific bioactive components, with emphasis in phenolic compounds. However, the ability to produce a determined phytochemical might be variable, even among species with close phylogeny. Furthermore, the metabolic dynamics vary greatly according to phenologic factors. Herein, it was verified whether isoflavone production in Medicago spp. is more associated with phylogenetic or phenologic determinants, to define the optimal productive conditions. Isoflavone profiles were characterized in field-grown Medicago species in three phenologic stages. Isoflavones were extracted by matrix solid-phase dispersion method and analyzed using high-performance liquid chromatography coupled with a diode-array detector. The obtained data were evaluated by a generalized linear model (GLM) and linear discriminant analysis (LDA). Formononetin, genistein and irilone were the most abundant isoflavones, reaching values higher than those present in acknowledged plant sources like soy or red clover. Outputs from GLM and LDA indicate that the phylogenetic factors are the most defining criteria. This study promotes Medicago spp. as potential isoflavone sources, particularly because the effects of these compounds are highly dependent on their type and concentration, with potential application as foodstuff, feedstuff, or in the nutraceutical and pharmaceutica l industry.Visnevschi-Necrasov and João C.M. Barreira are grateful to ‘‘FCT – Fundação para a Ciência e a Tecnologia’’ for their Grants (SFRH/BD/31734/2006 and SFRH/BPD/72802/2010, respectively). S.C. Cunha is grateful to ‘‘POPH-QREN – Tipologia 4.2, Fundo Social Europeu e Fundo Nacional MCTES’’.info:eu-repo/semantics/publishedVersio

Phylogenetic insights on the isoflavone profile variations in Fabaceae spp.: Assessment through PCA and LDA

Legumes (Fabaceae) are important crops, known as sources of food, feed for livestock and raw materials for industry. Their ability to capture atmospheric nitrogen during symbiotic processes with soil bacteria reduces the need for expensive chemical fertilizers, improving soil and water quality. Several Fabaceae species are acknowledged for the high levels of secondary metabolites. Isoflavones are among the most well-known examples of these compounds, being recognized for their several types of biological activity. Herein, isoflavone profiles were characterized in nine species of four Fabaceae genera (Biserrula, Lotus, Ornithopus and Scorpiurus). Plants were harvested in the late flower physiological stage to prevent biased results due to naturally occurring variations along the vegetative cycle. Isoflavones were extracted using matrix solid-phase dispersion and analyzed by high performance liquid chromatography/diode-array detection. The detected profiles revealed significant differences, inclusively among species belonging to the same genus, indicating that other factors besides the genotypic features contribute to the expression of these phenolic compounds. The classification of the results by principal component analysis placed species belonging to the same genus in different clustering groups, proving this latter assumption. However, the detected profiles proved to be characteristic of the assayed, as it was proved by the applied linear discriminant analysis.info:eu-repo/semantics/publishedVersio