Browsing by Author "Ferreira, Isabel M. P. L. V. O."
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- Determinação sequencial de anião cloreto e de catião sódio em águas por FIAPublication . Ferreira, Isabel M. P. L. V. O.; Lima, José L. F.C.; Rangel, António O. S. S.
- Flow injection sequential determination of chloride by Potentiometry and Sodium by flame emission spectrometry in instant soupsPublication . Ferreira, Isabel M. P. L. V. O.; Lima, José L. F. C.; Rangel, António O. S. S.A flow injection system for the sequential determination of chloride and sodium in instant soups is described. The chloride is measured with a tubular chloride ion selective electrode with a membrane consisting of a homogeneous mixture of silver chloride and silver sulfide, and the sodium is measured by flame emission spectrometry. Results were in good agreement with the reference procedures and exhibited good precision (relative standard deviations less than 1.1%). The sampling rate was 150 samples per hour.
- Flow injection titration of chloride in food products with a silver tubular electrode based on an homogeneous crystalline membranePublication . Ferreira, Isabel M. P. L. V. O.; Lima, José L. F. C.; Rangel, António O. S. S.A flow injection system for the pseudo-titration of chlorides in food products with potentiometric detection has been developed. For this purpose, a silver ion selective tubular electrode based on a homogeneous crystalline membrane, prepared by pressing silver sulphide at high pressure, was constructed. Its operational characteristics were evaluated and compared with the corresponding conventionally shaped electrodes obtained with the same sensor. The results obtained for chloride determination in wine, milk, beer and vinegar by using the FIA methodology were in good agreement with those provided by reference procedures. The sampling rate achieved varied between 120 and 360 samples per hour.
- In-line monitoring of the coffee roasting process with near infrared spectroscopy: Measurement of sucrose and colourPublication . Santos, João Rodrigo; Viegas, Olga; Páscoa, Ricardo N. M. J.; Ferreira, Isabel M. P. L. V. O.; Rangel, António O. S. S.; Lopes, João AlmeidaIn this work, a real-time and in-situ analytical tool based on near infrared spectroscopy is proposed to predict two of the most relevant coffee parameters during the roasting process, sucrose and colour. The methodology was developed taking in consideration different coffee varieties (Arabica and Robusta), coffee origins (Brazil, East-Timor, India and Uganda) and roasting process procedures (slow and fast). All near infrared spectroscopy-based calibrations were developed resorting to partial least squares regression. The results proved the suitability of this methodology as demonstrated by rangeerror- ratio and coefficient of determination higher than 10 and 0.85 respectively, for all modelled parameters. The relationship between sucrose and colour development during the roasting process is further discussed, in light of designing in real-time coffee products with similar visual appearance and distinct organoleptic profile.
- Interrelationships among microbiological, physicochemical, and biochemical properties of Terrincho cheese, with emphasis on biogenic aminesPublication . Pinho, Olivia; Pintado, Ana I. E.; Gomes, Ana M. P.; Pintado, M. E.; Malcata, F. Xavier; Ferreira, Isabel M. P. L. V. O.Changes in the microbiological, physicochemical, and biochemical characteristics of Terrincho cheese as represented by native microflora, pH, water activity, soluble nitrogen fractions, free amino acids, and biogenic amines (e.g., ethylamine, dimethylamine, tryptamine, phenylethylamine, putrescine, cadaverine, histamine, tyramine, cystamine, and spermine) during ripening were monitored. Terrincho is a traditional Portuguese cheese manufactured from raw ewe's milk. The main groups of microorganisms (lactococci, lactobacilli, enterococci, pseudomonads, staphylococci, coliforms, yeasts, and molds) were determined following conventional microbiological procedures. Free amino acids and biogenic amines were determined by reverse-phase high-performance liquid chromatography, following extraction from the cheese matrix and derivatization with dabsyl chloride. The total content of free amino acids ranged from 1,730 mg/kg of dry matter at the beginning of the ripening stage to 5,180 mg/kg of dry matter by day 60 of ripening; such an increase was highly correlated with the increase of watersoluble nitrogen in total nitrogen, 12% trichloroacetic acid–soluble nitrogen in total nitrogen, and 5% phosphotungstic acid– soluble nitrogen in total nitrogen throughout ripening. Histamine was consistently present at very low levels, whereas putrescine, cadaverine, and tryptamine were the dominant biogenic amines and increased in concentration during ripening. Ethylamine, tryptamine, phenylethylamine, and cystamine reached maxima by 30 days of ripening and decreased thereafter. Significant correlations between amino acid precursors and corresponding biogenic amines, as well as between biogenic amines and microbial viable numbers, were observed.
- Microbiological, biochemical and biogenic amine profiles of Terrincho cheese manufactured in several dairy farmsPublication . Pintado, Ana I. E.; Pinho, Olívia; Ferreira, Isabel M. P. L. V. O.; Pintado, M. E.; Gomes, Ana M. P.Terrincho is a Portuguese traditional cheese, bearing a protected denomination of origin (PDO) status, which is manufactured from raw ewes’ milk and ripened for a minimum period of 30 d. The objectives of this research effort were to characterize the microbiological and biochemical profiles of this cheese, manufactured in several dairy farms during the winter cheesemaking season (December through March), and establish tentative correlations between these profiles and formation of biogenic amines. For this goal, 29 cheeses from five batches, manufactured in as many dairy farms located throughout the PDO region, were analysed. The viable numbers of the total (mesophilic) microflora, enterococci, lactococci, lactobacilli, enterobacteria, staphylococci, pseudomonads, yeasts and moulds were determined by 30 d, following classical plate counting on specific media. Free amino acid and biogenic amine contents were determined by reverse-phase high-pressure liquid chromatography. The concentration of biogenic amines correlated well with microbial viable numbers, in both qualitative and quantitative terms; significant correlations were observed between enterococci and phenylethylamine (r ¼ 0.868, po0.0001), and between lactococci and cadaverine (r = 0.646, p <0.002) and tyramine (r = 0.868, p<0.0001). On the other hand, 220 g of Terrincho cheese would have to be consumed at a given time if the threshold of worst case risk was to be attained, which appears unrealistic for a typically single-doses meal ingredient. This study has contributed to deepen the knowledge on the microbiological and biochemical features of a unique Portuguese cheese throughout ripening, and to rationalize its safe consumption in terms of biogenic amines.