Browsing by Author "Pereira, Daniela"
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- Adsorption isotherms of maria biscuits from different brandsPublication . Guiné, Raquel; Barroca, Maria João; Pereira, Daniela; Correia, PaulaThis study aimed to determine the adsorption curves of Maria biscuits from dif- ferent brands at temperatures of 25 and 40C. The equilibrium between the sample and the atmosphere was achieved by placing the samples inside flasks containing saturated salts, at the temperatures studied for 5 days, to allow reaching equilibrium.From the results, it was possible to observe that by increasing the tem- perature, the stability of the product is augmented, as for the same moisture content the water activity is greatly reduced. Four sorption models were fitted with the adsorption data, but the Guggenheim–Anderson–deBoer and Henderson were better than the other models tested. In addition, the monolayer moisture content at temperature of 25C ranged between 0.0495 and 0.1981 g water/g dry basis, and at the temperature of 40C this parameter varied between 0.0529 and 0.1960 g water/g dry basis.
- Analysis of the physical-chemical and sensorial properties of Maria type cookiesPublication . Pereira, Daniela; Correia, Paula; Guiné, RaquelGiven the importance of the cookies of type Maria worldwide, and considering the absence of any scientific study setting out their main features, it becomes important to identify the differentiating characteristics of several commercialized brands, in particular related to the chemical, physical and sensory characteristics. In this way, the aim of this work was to study and compare eight different brands of cookies of type Maria. The elemental chemical analysis (moisture, ash, protein, fat, fibre and carbohydrates contents), determination of physical parameters (volume, density, texture and colour) and sensory evaluation of studied cookies were performed. Multivariate statistical methods (Pearson correlation, principal component analysis and cluster analysis) were applied to estimating relationships in analysed data. The results for the elemental analysis showed that the samples were very similar in terms of some components, like for example ashes, while quite different in terms of other components, such as moisture and fat contents. With respect to texture and colour the samples showed, in general, some important differences. In terms of sensory evaluation, the sample C was the one that in most sensory tests gathered the preference of the panellists. The cluster analysis showed that the sample A was much different from the other samples. The results of principal component analysis showed that the main component explains 32.6 % of the total variance, and is strongly related to variables associated to colour.