Unidade de Investigação - MARE – Marine and Environmental Sciences Centre
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Browsing Unidade de Investigação - MARE – Marine and Environmental Sciences Centre by Author "Abreu, Marta"
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- Effect of heat treatment on smoothie quality by response surface methodologyPublication . Pinheiro, Joaquina; Santos, Diana I.; Gonçalves, Elsa M.; Abreu, Marta; Moldão-Martins, MargaridaSmoothies are a popular and convenient way for to consume bioactive compounds from fruits and vegetables such as total phenolics, carotenoids and flavonoids, with the preservation treatment being an important action to guarantee the safety and extension of shelf-life. The main goal of this study was to evaluate the impact of heat treatment (HT) on smoothie prepared with “Fuji “apple (41%), pineapple (31%), cabbage (8%), pumpkin (10%) and banana (10%), by response surface methodology (RSM), where the temperature (70–100 °C) and treatment time (0.5–10.5 min), were the dependent variables. After optimization of HT conditions, a validation assay was performed to guarantee the minimal changes on color and reduction of 90% of polyphenoloxidase enzyme (PPO). Antioxidant activity (Ferric reducing antioxidant power assay (FRAP), DPPH, ABTS), total phenolics content (TPC), pH and solids soluble content were also analyzed. Predicted models of color parameters (L*, a*, ºh) and PPO enzymatic activity were found to be significant (p < 0.05) with regression coefficients (R2) of 0.84, 0.86, 0.92 and 0.97, respectively. From the RSM-generated model, the HT conditions that ensure a minimal green loss of smoothie and inactivation of PPO enzyme was at 85 °C over 7 min. In the validation study, these conditions were tested and proved to be sufficient to achieve the main goals. In the heat-treated smoothie, increases in TPC (10%) and antioxidant capacity (ABTS: 50%, DPPH: 17%, FRAP: 13%) were attained. This study demonstrated that RSM was efficient to select the optimal conditions of HT and improve the important quality properties that influence the product quality and the potential consumer’s health (TPC and antioxidant capacity).
- Quality changes during thermal processing of two mixed formulas of fruits and vegetables pulpsPublication . Gonçalves, Elsa M.; Raposo, Isa; Pinheiro, Joaquina; Alegria, Carla; Moldão, Margarida; Abreu, MartaThe present work aimed to evaluate, through thermal degradation kinetics (80 °C to 98 °C in time intervals of 0.5 to 25 min), the effects of different thermal treatments on the biochemical, physicochemical, sensory and microbiological parameters of two mixed fruit and vegetable pulps, a yellow and a red one. The evaluated fruit and vegetable pulps resulted from the mixture of different fruits and vegetables proportions (pineapple, beetroot, strawberry and lemon juice) added to a 50% (p/p) pear-based pulp to maximize their bioactivity, physicochemical stability and sensorial acceptance. Evaluated quality parameters included the determination of peroxidase activity (POD), pH, soluble solids content (SSC), total phenolic content (TPC), CIELab colour, sensory evaluation (colour, taste and aroma) and total mesophilic aerobic counts (TAPC). Regarding heat treatments optimization for both pulps with lower pH, it was concluded that higher temperature treatments (90 to 98 °C) applied over a shorter time (less than 5 min) were more effective to inactivate POD, to reduce the initial microbial load (>2 log10 cycles) and to maximize sensorial attributes. In both mix pulps, total phenolic content (TPC) was not significantly influenced by the different applied time-temperature binomials. From the degradation kinetic models and as an example, it was possible to conclude that POD followed a 1st order kinetic, where the temperature effect was well fitted to the Arrhenius equation. The results allowed to obtain optimized time-temperature binomials for each pulp to simultaneously achieve POD enzyme inactivation, microbial reduction, and maximization of quality parameters relatively to fresh pulps, 90 °C/5 min and 98 °C/2.5 min, for the yellow pulp and red pulp, respectively.
- Quality changes of carrots under different frozen storage conditions: A kinetic studyPublication . Gonçalves, Elsa M.; Abreu, Marta; Pinheiro, Joaquina; Brandão, Teresa R. S.; Silva, Cristina L.M.In order to improve the overall quality of frozen carrots (Daucus carota L.), the degradation kinetics of several attributes were quantified during frozen storage under isothermal and nonisothermal conditions. The experimental results showed that the analyzed quality parameters were significantly affected by both tested frozen regimes. For both storage conditions, the degradation of color parameters and drip loss followed zero-order kinetics, and the texture was successfully described by a fractional kinetic model. A first-order kinetic model was adequate in describing total vitamin C decay under isothermal storage conditions. The storage temperature effect was adequately modeled by the Arrhenius law. The carrots shelf life under isothermal storage conditions of −18°C, using a threshold of 50% vitamin C content, will be of 118 days. Practical applications: The objective of this work was to evaluate the degradation kinetics of several quality attributes of carrots when subjected to various frozen storage temperature conditions that may occur along the distribution chain. The quality attributes degradation mechanisms are governed by chemical and/or physical changes that need to be systematically evaluated for further incorporation into product and process designs. The achieved results will be an insight to help manufacturers to predict and optimize products quality and determine its shelf life.