Eulália Mendes

Quality evaluation of Portuguese honey

Abstract The present work was conducted to evaluate the quality of 25 brands of honey commercially available on the Portuguese market, in a total of 50 samples. The brands included unifloral and multifloral honeys, which were studied and botanically typified. Carbohydrate composition was determined by HPLC-RI to evaluate the contents of monosaccharides fructose and glucose; the disaccharides saccharose, maltose and trehalose and of the trisaccharide melizitose. 5-Hydroxymethyl-2-furfuraldehyde (HMF) was quantified by HPLC-UV and other physicochemical quality parameters were also carried out according to the European (Directive 74/409/EC) and Portuguese Regulations (Decreto-lei No. 131/85, 1985) in order to determine moisture, ash content, diastase activity, free acidity, free acidity and water-insoluble solids. All samples were organoleptically and microscopically examined. Only 13 brands were found to meet all major national and international specifications, the remaining 12 did not agree with one or more of the analysed parameters (HMF, diastase activity, or carbohydrate composition); such observations may reflect an inadequate manufacturing or storing process and a certain ageing of these honeys.

Effect of temperature on evolution of free amino acid and biogenic amine contents during storage of Azeitão cheese

Abstract A study on the evolution of free amino acids and biogenic amines in Azeitao cheese during 4 weeks at different temperatures of storage (4 and 25°C) was performed. Free amino acids and biogenic amines were determined by RP-HPLC with visible detection, following extraction from the cheese and derivatization with dabsyl chloride. The method presented a linear relation between peak area and concentration from 2–200 mg/l. The detection limit value was less than 1.5 mg/l. The average repeatability was less than 4%. The major free amino acids were proline, valine, isoleucine and leucine and the major amines were tyramine, cadaverine and histamine. Room temperature (25°C) promoted a significant increase of the contents of valine, leucine, tyramine and putrescine, expressed as g/kg of dry matter. These two free amino acids and two biogenic amines may serve as indicators of temperatures changes in ripened cheese.

Simultaneous determination of bisphenol A and bisphenol B in beverages and powdered infant formula by dispersive liquid–liquid micro-extraction and heart-cutting multidimensional gas chromatography-mass spectrometry

The purpose of this study was to establish a reliable, cost-effective, fast and simple method to quantify simultaneously both bisphenol A (BPA) and bisphenol B (BPB) in liquid food matrixes such as canned beverages (soft drinks and beers) and powdered infant formula using dispersive liquid–liquid micro-extraction (DLLME) with in-situ derivatisation coupled with heart-cutting gas chromatography-mass spectrometry (GC-MS). For the optimisation of the DLLME procedure different amounts of various extractive and dispersive solvents as well as different amounts of the derivative reagent were compared for their effects on extraction efficiency and yields. The optimised procedure consisted of the injection of a mixture containing tetrachloroethylene (extractant), acetonitrile (dispersant) and acetic anhydride (derivatising reagent) directly into an aliquot of beverage samples or into an aqueous extract of powdered milk samples obtained after a pretreatment of the samples. Given the compatibility of the solvents used, and the low volumes involved, the procedure was easily associated with GC-MS end-point determination, which was accomplished by means of an accurate GC dual column (heart-cutting) technique. Careful optimisation of heart-cutting GC-MS conditions, namely pressure of front and auxiliary inlets, have resulted in a good analytical performance. The linearity of the matrix-matched calibration curves was acceptable, with coefficients of determination (r2) always higher than 0.99. Average recoveries of the BPA and BPB spiked at two concentration levels into beverages and powdered infant formula ranged from 68% to 114% and the relative standard deviation (RSD) was <15%. The limits of detection (LOD) in canned beverages were 5.0 and 2.0 ng l–1 for BPA and BPB, respectively, whereas LOD in powdered infant formula were 60.0 and 30.0 ng l–1, respectively. The limits of quantification (LOQ) in canned beverages were 10.0 and 7.0 ng l–1 for BPA and BPB, respectively, whereas LOQ in powdered infant formula were 200.0 and 100.0 ng l–1, respectively. BPA was detected in 21 of 30 canned beverages (ranging from 0.03 to 4.70 µg l–1) and in two of seven powdered infant formula samples (0.23 and 0.40 µg l–1) collected in Portugal. BPB was only detected in canned beverages being positive in 15 of 30 samples analysed (ranging from 0.06 to 0.17 µg l–1). This is the first report about the presence of BPA and BPB in canned beverages and powdered infant formula in the Portuguese market.

Espresso coffee residues: a valuable source of unextracted compounds.

Espresso spent coffee grounds were chemically characterized to predict their potential, as a source of bioactive compounds, by comparison with the ones from the soluble coffee industry. Sampling included a total of 50 samples from 14 trademarks, collected in several coffee shops and prepared with distinct coffee machines. A high compositional variability was verified, particularly with regard to such water-soluble components as caffeine, total chlorogenic acids (CGA), and minerals, supported by strong positive correlations with total soluble solids retained. This is a direct consequence of the reduced extraction efficiency during espresso coffee preparation, leaving a significant pool of bioactivity retained in the extracted grounds. Besides the lipid (12.5%) and nitrogen (2.3%) contents, similar to those of industrial coffee residues, the CGA content (478.9 mg/100 g), for its antioxidant capacity, and its caffeine content (452.6 mg/100 g), due to its extensive use in the food and pharmaceutical industries, justify the selective assembly of this residue for subsequent use.

SIMULTANEOUS DETERMINATION OF BENZOIC AND SORBIC ACIDS IN QUINCE JAM BY HPLC

Abstract An isocratic HPLC technique is described for the determination of benzoic acid and sorbic acid in industrial quince jam. The preparation procedure was optimized. Precipitation of proteins and fat by the addition of methanol, followed by centrifugation and/or filtration provided an extract suitable for chromatographic analysis. The chromatographic separation was achieved with a C18 column and acetate buffer (pH=4.4) - methanol (65:35) as the mobile phase. The effluent was monitored at 235 nm. Effective separation and quantification was achieved in less than 7 min. Specificity of the method was checked against common food additives added to industrial quince jam, such as l -ascorbic acid and citric acid. Diode array detection was used for confirmation of the preservatives. Mean recoveries of 95–104% were obtained with a precision less than 2.6%, detection limits of 25 and 6.25 mg/kg were obtained for benzoic and sorbic acids, respectively. Results were in good agreement with the reference methods. The presence of benzoic and sorbic acids in quince jams available on the Portuguese market, was also determined. Eleven commercial brands of quince jam were analysed. All contained benzoic acid. The concentration ranged from 413.9±10.4 to 1501±4.2 mg of benzoic acid/kg of quince jam. Only two brands also contained sorbic acid. The concentrations were 515.0±7.0 and 908.3±5.3 mg of sorbic acid/kg of quince jam.

The determination and distribution of nucleotides in dairy products using HPLC and diode array detection

Abstract A method for the determination of adenosine, cytidine, uridine, guanosine and inosine 5′-monophosphates in milk and dairy products was optimized and its performance evaluated. The technique was based on ion-pair reversed-phase HPLC separation of the nucleotides and diode array detection. The chromatographic separation was achieved using a C18 column and a gradient elution with a mixture of two solvents: solvent A, water/glacial acetic acid/tetrabutilammonium hydrogensulphate (TBAHS) and solvent B, methanol/glacial acetic acid/TBAHS. The effluent was monitored using a Diode Array detector set at 260 nm. Validation of the proposed method was carried out by standard additions method, with recoveries of 98.3%. The precision of the method was also evaluated and reported a coefficient of variation (CV) as less than 3.2. Upon development the technique was applied on different dairy products in order to study the distribution of nucleotides therein. The samples included bovine, ovine and caprine milks, the corresponding manually manufactured cheeses, whey cheese and whey. Three commercial cheeses made from bovine, ovine and caprine milks, respectively, and 20 infant formulae were also analysed. In contrast to their absence in cheese upon preparation nucleotides were present in cheese at the end of ripening; this observation led to the extraction of DNA in order to evaluate whether nucleotides were released from degradation of nucleoproteins.

Development of An HPLC-UV Method for Determination of Taurine in Infant Formulae and Breast Milk

Abstract A rapid and accurate high performance liquid chromatographic (HPLC) procedure was proposed for routine and selective determination of taurine in infant formulas and breast milk. The sample preparation was simple, involving protein removal and filtration operations. Afterwards, taurine was derivatised with o-phtha]aldehyde/2-mercaptoethanol prior to injection onto a reversed phase column C18 (S10ODS2). Isocratic elution was carried out using 0.05 M phosphate buffer pH 5.3/ methanol (60:40) mixture. The effluent was monitored by a UV detector at 350 nm. A linear relationship was found between peak area and a concentration range of 1–70 μg/mL. The detection limit was 0.3 μg/mL. Effective separation and quantification was achieved in under six minutes. No interference of other amino acids was observed. Extensive validation of the proposed method was carried out both by the standard additions method and by comparison with a fluorimetric method of known accuracy. The precision was better than 1.4%.

Antioxidant activity and bioactive compounds of lettuce improved by espresso coffee residues

The antioxidant activity and individual bioactive compounds of lettuce, cultivated with 2.5-30% (v/v) of fresh or composted espresso spent coffee grounds, were assessed. A progressive enhancement of lettuces antioxidant capacity, evaluated by radical scavenging effect and reducing power, was exhibited with the increment of fresh spent coffee amounts, while this pattern was not so clear with composted treatments. Total reducing capacity also improved, particularly for low spent coffee concentrations. Additionally, very significant positive correlations were observed for all carotenoids in plants from fresh spent coffee treatments, particularly for violaxanthin, evaluated by HPLC. Furthermore, chlorophyll a was a good discriminating factor between control group and all spent coffee treated samples, while vitamin E was not significantly affected. Espresso spent coffee grounds are a recognised and valuable source of bioactive compounds, proving herein, for the first time, to potentiate the antioxidant pool and quality of the vegetables produced.

DEVELOPMENT AND APPLICATION OF AN HPLC/DIODE ARRAY METHODOLOGY FOR DETERMINATION OF NUCLEOTIDES IN INFANT FORMULAE AND FOLLOW-UP MILKS

This paper describes a procedure performed by high performance liquid chromatography/diode array detection for quantification of 4 nucleotides (cytidine 5-monophosphate, uridine 5-monophosphate, guanosine 5-monophosphate and adenosine 5-monophosphate) in infant formulae and follow-up milks. The sample preparation was simple and involved protein removal and filtration. The chromatographic separation was achieved using reverse-phase column C18 (S10ODS2). Isocratic elution was used, with 90% buffer A and 10% buffer B. Buffer A consisted of 5 mM tetrabutylammonium hydrogensulphate (TBAHS) and 20 mM potassium dihydrogenphosphate (KH2PO4) and buffer B of 5 mM TBAHS, 100 mM di-potassium hydrogen phosphate (K2HPO4), and 10% (v/v) acetonitrile. The pH of both solutions was adjusted to 5.2. The effluent was monitored using a diode array detector at 260 nm. A linear relationship was found between peak area and concentration of nucleotides, over the concentration range of 2–30 mg/L for cytidine and uridine and of 4–3...

Improvement of vegetables elemental quality by espresso coffee residues

Spent coffee grounds (SCG) are usually disposed as common garbage, without specific reuse strategies implemented so far. Due to its recognised richness in bioactive compounds, the effect of SCG on lettuces macro- and micro-elements was assessed to define its effectiveness for agro industrial reuse. A greenhouse pot experiment was conducted with different amounts of fresh and composted spent coffee, and potassium, magnesium, phosphorous, calcium, sodium, iron, manganese, zinc and copper were analysed. A progressive decrease on all lettuce mineral elements was verified with the increase of fresh spent coffee, except for potassium. In opposition, an increment of lettuces essential macro-elements was verified when low amounts of composted spent coffee were applied (5%, v/v), increasing potassium content by 40%, manganese by 30%, magnesium by 20%, and sodium by 10%, of nutritional relevance This practical approach offers an alternative reuse for this by-product, extendable to other crops, providing value-added vegetable products.