Loading...
177 results
Search Results
Now showing 1 - 10 of 177
- Measurement of oxygen transmission rate through foamed materials for bottle closuresPublication . Poças, Maria F.; Ferreira, Belmiro; Pereira, Joel; Hogg, TimThe determination of the oxygen transmission rate (OTR) through closures in glass bottles is becoming increasingly important for quality control of different batches and for development purposes. The Mocon method for measuring OTR is globally accepted and used in different applications. However, one of the major drawbacks this method presents when applied to bottle/closures systems is the long time required to obtain stable measurements when 40 mm long closures are tested. This paper describes a method to obtain OTR values with samples of reduced thickness with much shorter measurements time, since the condition of steady state during measurements is achieved faster and compares the estimated full-length commercial closure OTR with experimental values
- Microbiological profile in Serra ewes' cheese during ripeningPublication . Macedo, A. C.; Malcata, F. X.; Hogg, T. A.The microflora of Serra cheese was monitored during a 35 d ripening period at three different periods within the ewe's lactation season. After 7 d ripening, the numbers of micro-organisms reached their maximum, and lactic acid bacteria (LAB) and coliforms were the predominant groups. Pseudomonads were not detected after 1 week of ripening. At all stages of ripening, cheeses manufactured in spring exhibited the lowest numbers of LAB and yeasts, whereas cheeses manufactured in winter showed the lowest numbers of coliforms and staphylococci. Leuconostoc lactis was the most abundant LAB found in Serra cheese whereas Enterococcus faecium and Lactococcus lactis spp. lactis exhibited the highest decrease in percentage composition. Numbers of both Leuc. mesenteroides and Lactobacillus paracasei tended to increase throughout ripening. The most abundant coliform was Hafnia alvei. Klebsiella oxytoca was found in curd but declined in number during ripening. Staphylococcal flora of curd was mainly composed of Staphylococcus xylosus, Staph. aureus and Staph. epidermidis. Staphylococcus xylosus was the major species found at the end of ripening. Pseudomonas fluorescens, was the only Pseudomonas species isolated from the curd. Although a broad spectrum of yeasts were found in Serra cheese, Sporobolomyces roseus was the most abundant yeast isolated.
- Determination of antioxidant capacity using the biological system bacteriophage P22/bacterium salmonella typhimuriumPublication . Gião, Maria S.; Borges, André B.; Guedes, Catarina J.; Hogg, Tim; Pintado, Manuela E.; Malcata, F. XavierBacteriophage/bacterium systems have been employed in the past in assays for virucidal activity. A novel application of one such system is proposed here for the in vivo determination of antioxidant capacity. It was shown that an antioxidant such as gallic acid can effectively protect against oxidative damage brought about by H2O2sbut only within a narrow range of concentrations (i.e., from 250 to 500 mg L-1); ascorbic acid, on the other hand, did not exhibit any protective effect against H2O2. Finally, neither ascorbic nor gallic acid demonstrated a virucidal effect. The P22/Salmonella typhimurium model system thus proved to be useful in the assessment of antioxidant capacity in vivo, at least using those two alternative model antioxidants.
- Virulence genes amongst strains of L. monocytogenes isolated from cheesesPublication . Almeida, Gonçalo; Teixeira, Paula; Hogg, Tim
- Knowledge on food hygiene of food service staff working in nursing homes and kindergartens in Porto region - PortugalPublication . Martins, Ricardo Bessa; Ferreira, Denise; Moreira, Luís M.; Hogg, Tim; Gestal, JuanIn this study the food-hygiene knowledge of food handlers working in nursing homes and kindergartens was evaluated. From a global population of 1392 food handlers, a sample was selected of 335 participants from 155 institutions (kindergartens and nursing homes), in the region of Porto, Portugal. Data was collected through a self-administrated, multiple-choice questionnaire that was filled-in individually, in the presence of the researchers. The average score of correctly answered questions was 13.9 ( 3.65SD), corresponding to 60.7% of the questions. The level of knowledge shown was heterogeneous, varying according to the topics covered and the socio-demographic characteristics of the participants, although some pattern could be discerned as to areas of strength and weakness. Knowledge relating to temperature control (44.2% of correct answers) and to risk associated to foods (50.2% of correct answers) was significantly lower (p < 0.001) than the overall knowledge (60.7% of correct answers). Education and training (over the previous 12 months) were positively correlated to higher knowledge on food hygiene (p < 0.001). The same could not be verified in relation to hazard analysis and critical control points (HACCP) implementation (p ¼ 0.454). The results underline the importance of assessing training needs and consider such needs when designing training programs
- Kinetics of oxidative degradation of white wines and how they are Affected by selected technological parametersPublication . Ferreira, António César Silva; Pinho, Paula Guedes de; Rodrigues, Paula; Hogg, TimThe negative effects of oxygen on white wine quality and the various factors which influence it (including temperature, dissolved oxygen, pH, and free SO2) are well documented both at the sensory and compositional levels. What is less defined is the quantitative relationship between these parameters and the kinetics of the development of the negative effects of oxidation. The experiment presented here attempts to generate data which can be used to predictively model the oxidative degradation of white wines. Bottled wines were submitted to extreme conditions (45 °C temperature, O2 saturation) during 3 months witth samples taken every 15 days for both sensorial and chemical analysis (GC-O/FPD/MS, 420 nm). The synergistic effects of increasing temperature and O2 at lower pH are evident, both on the decrease in levels of terpene alcohols and norisoprenoids (which impart floral aromas), and on the development of off-flavors such as “honey-like”, “boiled-potato”, and “farmfeed” associated with the presence of phenylacetaldehyde, methional, and 1,1,6-trimethyl-1,2- dihydronaphthalene.
- Determination of carotenoid profiles in grapes, musts, and fortified wines from Douro varieties of vitis viniferaPublication . Pinho, Paula Guedes de; Ferreira, António C. Silva; Pinto, Manuela Mendes; Benitez, Juan Gomez; Hogg, Timβ-Carotene and six xanthophylls (lutein, neoxanthin, violaxanthin, luteoxanthin, cryptoxanthin, and echinenone) have been identified and semiquantitatively or quantitatively determined in musts and port wines for the first time. An HPLC method was developed and compared with that of one based on thin layer cromatography with scanning densitometry. The most abundant carotenoids present in red grape varieties are β-carotene and lutein. In wines, significant quantities of violaxanthin, luteoxanthin, and neoxanthin were found. This study was done with berries (skin and pulp), musts, and fortified wines. Some experiments were performed to follow carotenoid content from grapes to wines. Although the levels of β-carotene and lutein found in fortified wines were lower than those found in musts, other xanthophylls, such as neoxanthin, violaxanthin, and luteoxanthin, exist in appreciable amounts in young ports.
- Exposure assessment of chemicals from packaging materials in foods: reviewPublication . Poças, Maria de Fátima; Hogg, TimIt is recognised that chemicals from packaging and other foodcontact materials can migrate into the food itself and thus be ingested by the consumer. The monitoring of this migration has become an integral part of ensuring food safety. This article reviews the current knowledge on the food safety hazards associated with packaging materials together with the methodologies used in the assessment of consumer exposure to these hazards. Special attention is given to the most promising approaches for exposure assessment and to the technical and other barriers which need addressing.
- Characterisation of alheiras, traditional sausages produced in the North of Portugal, with respect to their microbiological safetyPublication . Ferreira, Vânia; Barbosa, Joana; Silva, Joana; Felício, Maria Teresa; Mena, Cristina; Hogg, Tim; Gibbs, Paul; Teixeira, PaulaThe objective of this study was the characterisation of alheiras, traditional Portuguese sausages, with respect to their microbiological safety. Thirty-eight lots from 17 producers were analysed. The microbiological status of the analysed product can be considered of concern in terms of food safety. Although Campylobacter spp. and Escherichia coli O157 were not detected in any sample,and Clostridium perfringens when present was not at levels of concern with reference to public health, Salmonella spp. were detected in 2 lots of industrially produced alheiras, and more than 60% of the lots analysed were contaminated with Listeria monocytogenes in concentrations higher than 100 cfu/g.
- An overview of hazards and risks in food contact materialsPublication . Poças, M. F.; Hogg, T.