M.B.P.P. Oliveira

Quantitative detection of poultry meat adulteration with pork by a duplex PCR assay.

A species-specific duplex polymerase chain reaction (PCR) assay was developed for the simultaneous detection of pork and poultry meat species using the mitochondrial cytb and 12S rRNA as target genes for pork and poultry, respectively. By the amplification of binary reference meat mixtures, a linear normalised calibration curve was obtained using the fluorescence intensities of PCR products for pork (149 bp) and poultry (183 bp) species. The proposed method allowed the quantification of pork meat addition to poultry meat in the range of 1-75%, with a sensitivity of 0.1%. The in-house validation using samples with known amounts of pork meat (1.0%, 2.5%, 7.5%, 20.0% and 40%) evidenced a high reproducibility of the methodology (coefficient of variation from 4.1% to 7.6%). The successful application of the duplex PCR was also demonstrated by the high correlation (R(2)=0.99) obtained from regression analysis between the predicted and the actual values of pork meat addition in blind meat mixtures. The suggested methodology presents a low cost, fast, easy and reliable alternative to estimate the level of poultry meat adulteration by the addition of pork meat.

Phenolic profile evolution of different ready-to-eat baby-leaf vegetables during storage.

Ready-to-eat baby-leaf vegetables market has been growing and offering to consumers convenient, healthy and appealing products, which may contain interesting bioactive compounds. In this work, the composition and the evolution of the phenolic compounds from different baby-leaf vegetables during refrigerated storage was studied. The phenolic compounds were extracted using pressurized liquid extraction (PLE) and the phenolic profile of each sample was analyzed and quantified by using LC-MS and LC-DAD methods, respectively, at the beginning and at the end of a 10-day storage period. The baby-leaf vegetables studied included green lettuce, ruby red lettuce, swiss chard, spinach, pea shoots, watercress, garden cress, mizuna, red mustard, wild rocket and spearmint samples and a total of 203 phenolic compounds were tentatively identified and quantified. The main naturally phenolic compounds identified correspond to glycosylated flavonoids, with exception of green lettuce and spearmint leaves which had a higher content of hydroxycinnamic acids. Quantification of the main compounds showed a 10-fold higher content of total phenolic content of ruby red lettuce (483mgg(-1)) in relation to the other samples, being the lowest values found in the garden cress (12.8mgg(-1)) and wild rocket leaves (8.1mgg(-1)). The total phenolic content only showed a significant change (p<0.05) after storage in the green lettuce (+17.5%), mizuna (+7.8%), red mustard (-23.7%) and spearmint (-13.8%) leaves. Within the different classes of phenolic compounds monitored, the flavonols showed more stable contents than the hydroxycinnamic and hydroxybenzoic acids, although the behavior of each compound varied strongly among samples.

Quantification of synthetic phenolic antioxidants in liver pâtés

Abstract Pâtes are products with high fat levels and their consumption has increased in Portugal over the past few years. Owing to their composition, lipid oxidation is one of the primary mechanisms associated with deterioration of their quality. Therefore, antioxidants have become a useful group of food additives because they help to maintain the organoleptic quality of pâtes by avoiding rancidity. The aim of this work was the evaluation of seven synthetic antioxidants with phenolic structure, namely, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert -butyl hydroquinone (TBHQ), propyl (PG), octyl (OG) and dodecyl gallates (DG) and nordihydroguaiaretic acid (NDG), in liver pâtes available on the Portuguese retail market. The high performance liquid chromatography (HPLC) procedure described in AOAC for oils and fats was found to be inappropriate for pâtes, probably owing to their complex matrices. A modification of the Association of Official Analytical Chemists (AOAC) extraction procedure is thus presented. Extensive validation of this extraction procedure was carried out by recovery tests. Over 91% recoveries of added antioxidants were observed, except for PG and OG whose recoveries were 78.0±2.2 and 82.1±1.1 1%, respectively. The precision found was below 3.8%. No synthetic antioxidants were detected in six of the 12 assayed brands. One sample contained BHA and five samples contained NDG (concentrations ranged from trace levels to 26.3±0.0 mg/kg of product). When pepper corn was added as an additive to pâtes, piperine (the main compound of pepper) appeared on the chromatogram but it did not interfere with the evaluation of the other antioxidants.

Walnut allergens: molecular characterization, detection and clinical relevance.

Food‐induced allergies have been regarded as an emergent problem of public health. Classified as important allergenic ingredients, the presence of walnut and other nuts as hidden allergens in processed foods constitutes a risk for sensitized individuals, being a real problem of allergen management. Attending to the increasing importance dedicated to walnut allergy, this review intends to provide the relevant and up‐to‐date information on main issues such as the prevalence of walnut allergy, the clinical threshold levels, the molecular characterization of walnut allergens and their clinical relevance, as well as the methodologies for walnut allergen detection in foods. As the walnut used in human diet comes from Juglans regia and Juglans nigra, the molecular characterization of the allergens from both species included in the prolamins (Jug r 1, Jug n 1 and Jug r 3), cupins (Jug r 2, Jug n 2 and Jug r 4) and profilins (Jug r 5), together with respective clinical relevance, were compiled in this review. The most recent progresses on walnut allergen detection techniques (protein‐ and DNA‐based) are described and critically compared, including the emergent multitarget approaches.

Multi-elemental analysis of ready-to-eat “baby leaf” vegetables using microwave digestion and high-resolution continuum source atomic absorption spectrometry

The mineral content (phosphorous (P), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu)) of eight ready-to-eat baby leaf vegetables was determined. The samples were subjected to microwave-assisted digestion and the minerals were quantified by High-Resolution Continuum Source Atomic Absorption Spectrometry (HR-CS-AAS) with flame and electrothermal atomisation. The methods were optimised and validated producing low LOQs, good repeatability and linearity, and recoveries, ranging from 91% to 110% for the minerals analysed. Phosphorous was determined by a standard colorimetric method. The accuracy of the method was checked by analysing a certified reference material; results were in agreement with the quantified value. The samples had a high content of potassium and calcium, but the principal mineral was iron. The mineral content was stable during storage and baby leaf vegetables could represent a good source of minerals in a balanced diet. A linear discriminant analysis was performed to compare the mineral profile obtained and showed, as expected, that the mineral content was similar between samples from the same family. The Linear Discriminant Analysis was able to discriminate different samples based on their mineral profile.

Cholesterol determination in foods: Comparison between high performance and ultra-high performance liquid chromatography.

Analytical methods for cholesterol evaluation in foods are crucial since this compound was closely related with cardiovascular disease. In the present study, two chromatographic methods were implemented and validated, in order to achieve the ideal analytical method for the quantification of cholesterol in food matrices. The developed methods were applied to different foodstuffs, sour cream, egg, egg yolk and chicken nuggets. Both HPLC and UHPLC methods are rapid, specific, sensitive, precise (RSD<2.5%) and accurate. The achieved LOD and LOQ for UHPLC were 0.7 and 2.4μg/mL, respectively, while for HPLC were 3 and 11μg/mL. UHPLC method allowed reduction of the organic solvents consumption (8 times lower) and decreased analysis time in 4min, being more eco-friendly, than conventional HPLC methods. Moreover, it will be very useful for the quality control of cholesterol content in food matrices and can be easily adopted by analytical laboratories.

Characterization of Three Portuguese Varietal Olive Oils Based on Fatty Acids, Triacylglycerols, Phytosterols and Vitamin E Profiles: Application of Chemometrics

Publisher Summary The authenticity and traceability of olive oils has been the object of numerous studies in the past few years. Generally, characterization of monovarietal olive oils requires the study of several compounds, including major components, such as fatty acids (FA) and triacylglycerols (TAG), and the minor ones, such as phytosterols, polyphenols, tocopherols, tocotrienols, and pigments. FA have been successfully used for grouping olive oils according to the olive variety used. Besides, their knowledge is also important to estimate nutritional properties of oils, as saturated FA are associated with a higher risk of cardiovascular diseases, contrarily to mono- and polyunsaturated FA. Several results have also proved the usefulness of TAG in grouping monovarietal olive oils, suggesting that the FA content and distribution on the glycerol moiety can contribute to the establishment of a cultivar chemical fingerprint. Minor compounds, such as phenolics and tocopherols, important for their antioxidant activity, are also able to provide useful information for authenticity assessment. The geographical characterization of olive oils is another important aspect of concern, especially for those certificated as PDO, since they are added-value products. Chemical characterization followed by multivariate statistical analysis has been reported in several studies to be a useful tool for the classification of olive oils regarding their geographical origin. Known as high-quality products, the olive oils from Tras-os-Montes region achieve very high market prices, which can propitiate unfair commercial practices. It is therefore important to use analytical techniques to ensure the assessment of identity and quality of these oils, and guarantee the proper product classification.

Game: Types and Composition

In the last years, game meat consumption has been increasing possibly due to different motivations, including the perception that it is healthier, its particular taste and flavor, and the attraction for new experiences such as tasting exotic meats. Game meat is generally considered as a healthy food due to its low fat content, favorable fat composition, and rather high protein content. In this article, the main topics related to game meat are discussed, including data regarding game meat production and consumption, chemical composition, nutritional considerations, and general safety concerns.

Applicability of a real-time PCR system to verify labelling compliance of nut allergens in chocolates

Background Chocolate is probably one of the most appreciated food products all over the world. However, for allergic individuals to tree nut ingredients, the enjoyment of a simple milk or black chocolate is denied owing to the excessive use of precautionary labelling practiced by the food industry. Thus, it is of utmost importance the development of accurate analytical methodologies to verify labelling compliance and to contribute for a better control of cross-contamination occurrences during food processing. This work intended to demonstrate the applicability of real-time polymerase chain reaction (PCR) to detect and quantify hazelnut in commercial chocolates.

Protective effect of Crataegus monogyna Jacq. ethanolic extracts in oxidant-induced DNA damage evaluated through comet assay with human peripheral lymphocytes

Foundation for Science and Technology (FCT, Portugal) through CESAM (UID/AMB/50017/2013), CNRS/INEE and COMPETE/QREN/EU (PEst-C/EQB/LA0006/2013, NORTE-07-0124-FEDER-000069 CIENCIA DO ALIMENTO and PEst-OE/AGR/UI0690/2014). J.C.M. Barreira and Carla Costa thank FCT, POPH - QREN for their grants (SFRH/BPD/72802/2010 and SFRH/BPD/96196/2013, respectively).