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Ferro-Lebres V.,University of Porto | Ferro-Lebres V.,Polytechnic Institute of Braganza | Moreira P.,University of Porto | Ribeiro J.C.,University of Porto
Ecology of Food and Nutrition | Year: 2014

This article describes the adaptation of the adult Portuguese version of the General Nutrition Knowledge Questionnaire (GNKQ) for adolescents, and its validation. Respondents were 1,315 adolescents, who completed the questionnaire in two phases. A subsample of 73 adolescents was used to measure test-retest reliability. Concurrent validity was tested using a sample of 32 dietetic students. The adapted version showed high internal consistency (Cronbach's alpha = 0.92), test-retest reliability (R = 0.71) and concurrent validity (U = 22766.0; p <.01). Adolescents' nutrition knowledge can now be assessed with a valid and reliable instrument. Future validation works of this or others questionnaires for children and elderly are warranted. Copyright © Taylor & Francis Group, LLC.

Juneja V.K.,U.S. Department of Agriculture | Cadavez V.,Polytechnic Institute of Braganza | Gonzales-Barron U.,Polytechnic Institute of Braganza | Mukhopadhyay S.,U.S. Department of Agriculture
Food Research International | Year: 2015

The objective of this study was to assess the combined effects of temperature, pH, sodium chloride (NaCl), and sodium pyrophosphate (SPP) on the heat resistance of Escherichia coli O157:H7 in minced beef meat. A fractional factorial design consisted of four internal temperatures (55.0, 57.5, 60.0 and 62.5. °C), five concentrations of NaCl (0.0, 1.5, 3.0, 4.5 and 6.0. wt/wt.%) and SPP (0.0, 0.1, 0.15, 0.2 and 0.3. wt/wt.%), and five levels of pH (4.0, 5.0, 6.0, 7.0 and 8.0). The 38 variable combinations were replicated twice to provide a total of 76 survivor curves, which were modelled by a modified three-parameter Weibull function as primary model. The polynomial secondary models, developed to estimate the time to achieve a 3-log and a 5-log reduction, enabled the estimation of critical pH, NaCl and SPP concentrations, which are values at which the thermo-tolerance of E. coli O157:H7 reaches it maximum. The addition up to a certain critical concentration of NaCl (~. 2.7-4.7%) or SPP (~. 0.16%) acts independently to increase the heat resistance of E. coli O157:H7. Beyond such critical concentrations, the thermo-resistance of E. coli O157:H7 will progressively diminish. A similar pattern was found for pH with a critical value between 6.0 and 6.7, depending upon temperature and NaCl concentration. A mixed-effects omnibus regression model further revealed that the acidity of the matrix and NaCl concentration had a greater impact on the inactivation kinetics of E. coli O157:H7 in minced beef than SPP, and both are responsible for the concavity/convexity of the curves. When pH, SPP or NaCl concentration is far above or below from its critical value, the temperatures needed to reduce E. coli O157:H7 up to a certain log level are much lower than those required when any other environmental condition is at its critical value. Meat processors can use the model to design lethality treatments in order to achieve specific log reductions of E. coli O157:H7 in ready-to-eat beef products. © 2014 Elsevier Ltd.

Juneja V.K.,U.S. Department of Agriculture | Gonzales-Barron U.,Polytechnic Institute of Braganza | Gonzales-Barron U.,University College Dublin | Butler F.,University College Dublin | And 2 more authors.
International Journal of Food Microbiology | Year: 2013

We investigated the combined effect of three internal temperatures (60, 65 and 71.1°C) and four concentrations (0.0, 0.1, 0.5 and 1% vol/wt) of two natural antimicrobials on the heat resistance of an eight-strain cocktail of Salmonella serovars in chicken meat. A complete factorial design (3×4×4) was used to assess the effects and interactions of heating temperature and the two antimicrobials, carvacrol and cinnamaldehyde. The 48 variable combinations were replicated to provide a total of 96 survivor curves from the experimental data. Mathematical models were then developed to quantify the combined effect of these parameters on heat resistance of starved Salmonella cells. The theoretical analysis shows that the addition of plant-derived antimicrobials overcomes the heat resistance of starvation-stressed Salmonella in ground chicken meat. The influence of the antimicrobials allows reduced heat treatments, thus reducing heat-induced damage to the nutritional quality of ground-chicken products. Although the reported omnibus log-linear model with tail and the omnibus sigmoid model could represent the experimental survivor curves, their discrepancy only became apparent in the present study when lethality times (D-values and t7.0) from each of the models were calculated. Given the concave nature of the inactivation curves, the log-linear model with tail greatly underestimates the times needed to obtain 7.0 log lethality. Thus, a polynomial secondary model, based on the sigmoid model, was developed to accurately predict the 7.0-log reduction times. The three-factor predictive model can be used to estimate the processing times and temperatures required to achieve specific log reductions, including the regulatory recommendation of 7.0-log reduction of Salmonella in ground chicken. © 2013.

Juneja V.K.,U.S. Department of Agriculture | Cadavez V.,Polytechnic Institute of Braganza | Gonzales-Barron U.,Polytechnic Institute of Braganza | Mukhopadhyay S.,U.S. Department of Agriculture | Friedman M.,U.S. Department of Agriculture
Food Control | Year: 2016

Health concerns have led to a search for natural plant-based antimicrobials. Ellagic acid has been shown to have antimicrobial activity against foodborne pathogens. The objective of this study was to assess the effect of a high-ellagic acid commercial pomegranate on the heat resistance of Escherichia coli O104:H4 in ground chicken. A full 24 factorial design was used, consisting of temperature treatment with four levels (55.0, 57.5, 60.0, and 62.5 °C) and pomegranate with four levels (0.0, 1.0, 2.0, and 3.0 wt/wt. % containing 70% ellagic acid). Experiments were conducted twice, providing a total of 32 survival curves. A three-parameter Weibull primary model was used to describe survival kinetics. Secondary models were then developed to estimate the shape parameter β (i.e., curvature representing susceptibility of cells to stress), scale parameter γ (i.e., time to reach the first decimal reduction) and the 5.0-log lethality time t5.0 (i.e., time to reach a 5.0-log reduction), all as polynomial functions of temperature and pomegranate powder concentration. The positive effect of pomegranate concentration on both β and γ demonstrated that the phenolic-rich pomegranate powder causes E. coli O104:H4 cells to become more susceptible to heat, increasing the steepness and concavity of the isothermal survival curves. It was estimated that the 5.0-log reduction time would reach a minimum at a pomegranate powder concentration of 1%, producing a 50% decrease in lethality time, in comparison to that without added pomegranate powder. Nonetheless, a mixed-effect omnibus regression further confirmed that the greatest difference in the thermal resistance of E. coli O104:H4 happened between tests with and without pomegranate powder. In fact, adding more than 1.0% pomegranate powder, at a constant temperature, resulted only in a marginal decrease in thermal resistance. Meat processors can use the model to design lethality treatments in order to achieve specific reductions of E. coli O104:H4 in ground chicken. © 2016.

Gonzales-Barron U.,Polytechnic Institute of Braganza | Cadavez V.,Polytechnic Institute of Braganza | Butler F.,University College Dublin
Food Control | Year: 2014

Mixed Poisson distributions have been shown to be able to represent low microbial counts more efficiently than the lognormal distribution because of its greater flexibility to model microbial clustering even when data consist of a large proportion of zero counts. The objective of this study was to develop an alternative modelling framework for low microbial counts based on heterogeneous Poisson regressions. As an illustration, Poisson-gamma regression models were used to assess the effect of chilling on the concentration of total coliforms from beef carcasses (n=600) sampled at eight large Irish abattoirs. Three Poisson-gamma and three zero-modified (hurdle and zero-inflated) models were appraised with a series of random-effects variants in order to extract any variability in microbial mean concentration, dispersion and/or proportion of zero counts. Models were compared and validated in their ability to predict the coliforms counts on carcasses after chilling. In all five test batches, the hurdle Poisson-gamma distributions predicted the observed post-chill counts closer than the Poisson-gamma distributions. This is justified by the better capacity of the hurdle model to represent a higher proportion of zero counts, which were in fact observed in the post-chill batches. Thus, with a coded variable (pre-chill/post-chill) as treatment, and extracting the significant variability of batches nested in abattoirs for the coliforms mean concentration (σ2 u=2.68), the dispersion measure (σ2 v=2.39) and the probability of zero counts (σ2 w=0.89), the validated hurdle Poisson-gamma model confirmed that chilling has a decreasing effect on the viability of coliforms from beef carcasses, and that the concentration is reduced by an average (pre-chill to post-chill) factor of 2.2 (95% CI: 2.15-2.24) at batch level. The model also indicated that chilling increases the odds of producing a zero count from a carcass swab in about 13.5 times, and that the higher the coliforms concentration in a batch, the weaker the effect that chilling has to reduce such contamination on the beef carcasses. © 2013 Elsevier Ltd.

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