Browsing by Author "Gil, Maria M."
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- Application of microalgae as natural colorant for pastry and confectionary productsPublication . Pereira, Tatiana; Barroso, Sonia; Pinto, Filipa R.; Silva, Frederica; Teixeira, Paula; Mendes, Susana; Gil, Maria M.Modern consumers demand the replacement of synthetic colorants with natural alternatives. Microalgae can serve as an alternative source for these colorants since they hold significant amounts of pigments. This study aimed to evaluate the potential of using microalgae biomass and extracts as natural colorants for pastry and confectionary products. The application of different biomass and levels of Chlorella vulgaris (White, Honey, and a mixture of both) was evaluated in brioche-type breads as egg substitute to confer the typical yellow coloration to the product. A mixture of 1% Chlorella vulgaris (White: Honey [1:1]) showed potential as egg substitute, having minimal impact on the physical–chemical, microbiological, nutritional, and sensory characteristics of the products. Hydroalcoholic Tetraselmis chuii extracts were applied in fondant at a concentration of 0.05%, providing a green coloration with minimal impact on the quality of the product. This study supported the potential of using microalgae, biomass, and extracts, as alternative natural colorants in pastry and confectionary products.
- Application of optimal experimental design concept in microbial inactivation studiesPublication . Gil, Maria M.; Brandão, Teresa R. S.; Silva, Cristina L. M.
- Application of optimal experimental design concept to improve the estimation of model parameters in microbial thermal inactivation kineticsPublication . Gil, Maria M.; Miller, Fátima A.; Silva, Cristina L.M.; Brandão, Teresa R. S.The estimation of model parameters with high precision is of major importance in mathematical predictions. If a mathematical model is properly chosen and if the primary objective is to improve parameter estimation, underlying statistical theories can be applied. Precision increases with the number of experimental points. However, and in many situations,maximum precision is attained when sampling consists of replicates of specific experimental points. Experimental conditions can be optimized using the Doptimal design concept based on minimization of the generalized variance of the parameter estimates. The objective of this work was to use this methodology for the design of experiments for microbial inactivation processes described by a Gompertz-based model under isothermal and non-isothermal conditions. The application of D-optimal design concept considerably improved parameters precision, when compared to the commonly used heuristic designs.
- Chemical-based methodologies approaches to extend the shelf life of fresh fish — a reviewPublication . Amaral, Renata A.; Pinto, Carlos A.; Lima, Vasco; Tavares, Jéssica; Martins, Ana P.; Fidalgo, Liliana G.; Silva, Ana M.; Gil, Maria M.; Teixeira, Paula; Barbosa, Joana; Barba, Francisco J.; Saraiva, Jorge A.Due to its characteristics, fresh fish is a highly perishable food with a very short shelf-life under refrigeration. Several methods have been introduced to slow down its deterioration, such as by means of oxygen depletion of the food package (vacuum packaging), or by changing the natural atmosphere that is in contact with the fresh fish (modified atmosphere packaging), or by the use of chemicals generally recognized as safe: such compounds can be directly applied (by dipping or spraying) or incorporated into packaging materials and slowly migrate to the product, exerting a hurdle effect against microbial development and lipid oxidation (active packaging). This review aims to cover the most recent advances in chemical-based approaches for fresh fish preservation, applied either singly or in combination. Vacuum packaging, modified atmosphere, and active packaging preservation methodologies are presented, along with the inclusion of chemical additives, such as organic acids and natural extracts, and their combination with icing systems. Advantages and disadvantages of these methodologies and their impact on fresh fish quality and shelf-life are discussed, reaching the conclusion that both are positively influenced overall. Indeed, the contribution of chemical-based strategies for fresh fish preservation is undeniable, and is expected to be a research topic of increasing interest in the future.
- Combined effects of temperature, pH and water activity on predictive ability of microbial kinetic inactivation modelPublication . Gil, Maria M.; Miller, Fátima A.; Brandão, Teresa R. S.; Silva, Cristina L. M.It is well known that temperature is the key factor controlling the microbial survival/inactivation. However, the interactive effects of further stressing environmental conditions may influence microbial inactivation behaviour. The objective of this work was to include, in the inactivation model, temperature, pH and water activity effects using a black box polynomial model, aiming at accurate prediction. Experimental data of Listeria innocua obtained within the temperature range of 52.5 and 65.0 °C, pH of 4.5, 6.0 and 7.5, and water activity of 0.95 and 0.99 were used for model assessment. A Gompertz-inspired model for microbial inactivation was used, with shoulder period, maximum inactivation rate and tail as parameters. The relations of such parameters with temperature, water activity and pH were purely empirical and assumed to be polynomials. When these mathematical relationships were included in the primary kinetic model, accurate predictions of the inactivation data were attained, thus validating the predictive ability of the model expressed in terms of the stressing environmental factors studied. © 2015 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of Department of Food Science, Faculty of Food Engineering, University of Campinas.
- Combined effects of temperature, pH and water activity on predictive ability of microbial kinetic Inactivation modelPublication . Gil, Maria M.; Miller, Fátima A.; Brandão, Teresa R. S.; Silva, Cristina L.M.It is well known that temperature is the key factor controlling the microbial survival/inactivation. However, the interactive effects of further stressing environmental conditions may influence microbial behaviour. The objective of this work was to include, in the inactivation model, temperature, pH and aw effects using a black box polynomial model, aiming at accurate prediction. Data of Listeria innocua obtained within the temperature range of 52.5 and 65.0 °C, pH of 4.5, 6.0 and 7.5, and aw of 0.95 and 0.99 were used for model assessment. The relations of such parameters with temperature, aw and pH were assumed to be polynomials.
- Combined effects of temperature, pH and water activity on predictive ability of microbial kinetic inactivation modelPublication . Gil, Maria M.; Miller, Fátima A.; Brandão, Teresa R. S.; Silva, Cristina L. M.
- Development and optimization of high-protein and low-saturated fat bread formulations enriched with lupin and microalgaePublication . Pereira, Tatiana; Costa, Sandrina; Barroso, Sónia; Teixeira, Paula; Mendes, Susana; Gil, Maria M.Increased consumer awareness of healthier foods is driving the growth in the functional bread market. In view of this potential, three bread formulations were developed using various types of flour enriched with microalgae. The multigrain breads were composed of lupin and rye (F–R), lupin and spelt (F–S), and lupin, oats, and carob (F-OC) enriched with a mixture of Chlorella vulgaris (C. vulgaris White and C. vulgaris Smooth (4:1)). All breads were high in protein and low in saturated fat. Response surface methodology (RSM) following a central composite design (CCD) was used to evaluate the effect of selected technological parameters, namely water content (64.6–94.6% (w/w of flours)) and microalgae concentration (1.9–3.9% (w/w of flours)) on color, aroma, taste, texture, and overall sensory acceptance of the products. Only water content was found to affect the bread's sensory scores, especially texture, with higher water content increasing bread acceptance. This study allowed the development and optimization of three novel multigrain bread formulations enriched with microalgae that met the requirements of “rich in proteins” and “low in saturated fats” claims.
- Dynamic approach to assessing food quality and safety characteristics: the case of processed foodsPublication . Brandão, Teresa R. S.; Gil, Maria M.; Miller, Fátima A.; Gonçalves, Elsa M.; Silva, Cristina L. M.Consumers expect that food products will be safe and convenient to use and still have all the qualities of a fresh product. Foods often undergo processing, which has three major aims: to make food safe while providing products with the highest quality attributes, to transform food into forms that are more convenient or more appealing, and to extend shelf-life. Food processes such as thermally based ones (i.e. pasteurization and drying) or frozen storage occur in time-varying temperature conditions. Mathematical models that describe/predict changes in processed food characteristics with accuracy and precision in realistic, dynamic conditions are important tools in the development of new products and control systems. In this chapter, mathematical models that include time-varying temperature conditions (i.e. dynamic approach) will be presented for two relevant situations in the domain of processed foods: the case of microbial thermal inactivation and the case of food quality alterations under frozen storage.
- Heat inactivation of Listeria innocua in broth and food products under non-isothermal conditionsPublication . Miller, Fátima A.; Ramos, Bárbara F.; Gil, Maria M.; Brandão, Teresa R. S.; Teixeira, Paula; Silva, C. L. M.The objective of this work was to study the effect of three linear temperature profiles (heating rates of 1.5, 1.8 and 2.6 °C/min, from 20 to 65 °C) on Listeria innocua inactivation in liquid medium. The inactivation was also analyzed in artificially contaminated parsley (heating rate of 1.8 °C/min) and throughout a frying process, using a pre-cooked frozen food as case study. Inactivation showed a sigmoidal behaviour and all data was fitted with a Gompertz-inspired model. Results demonstrated that, in liquid media, Listeria inactivation is influenced by the temperature profile used. As heating rate increases, the shoulder decreases and the tail effect disappears. If Listeria was in parsley, its heat resistance increased (for identical experimental conditions in broth). Besides model adequacy was proven in all studied situations, the heating rate affected parameters’ precision.
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