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- Effect of conventional heat and thermosonication treatments on broccoli (brassica oleracea L.) total phenolic contentPublication . Gonçalves, Elsa M.; Alegria, C.; Abreu, Marta; Brandão, Teresa R. S.; Silva, Cristina L. M.
- Stability of sunflower and rapeseed oil-in-water emulsions supplemented with ethanol-treated rapeseed meal protein isolatePublication . Kalaydzhiev, Hristo; Gandova, Vanya D.; Ivanova, Petya; Brandão, Teresa R. S.; Dessev, Tzvetelin T.; Silva, Cristina L. M.; Chalova, Vesela I.A protein isolate (ERPI) was prepared from ethanol-treated rapeseed meal and used as a stabilizing agent in sunflower and rapeseed oil-in-water emulsions. The aim of the current study was to explore the influence of protein and oil concentrations on initial stability of sunflower and rapeseed oil-in-water emulsions by evaluating Gibbs free energy (ΔG) and particle size distribution. The 7-day dynamics of emulsion stability was investigated by turbidity measurement as well. A 32 factorial design was applied to assess the significance of oil (5%, 10% and 15% w/w) and ERPI protein (0.25%, 0.5% and 1.0% w/w) addition on stability of the emulsions. The results demonstrated that the increase of oil concentrations from 5 to 15% positively influenced the initial stability of sunflower and rapeseed oil-in-water emulsions. In both oil types, ERPI protein supplementation at all levels resulted in significant differences in the stability of 5% and 10% oil emulsions but did not alter the initial stability of the emulsions prepared with either 15% sunflower or rapeseed oil. With a few exceptions, there was a good agreement between Gibbs free energy data and microstructural profiles of the emulsions. Overall, emulsions with all sunflower oil concentrations and 1.0% ERPI protein exhibited better initial and a 7-day stability dynamics compared to all rapeseed oil-based emulsions. The study demonstrated the potential of ethanol-treated rapeseed meal protein isolate to serve as an emulsifying agent in sunflower and rapeseed oil containing emulsions.
- Novas tecnologias de prétratamento de hortofrutícolasPublication . Gonçalves, E. M.; Abreu, M.; Oliveira, A. J.; Portela, M.; Vieira, M. M. C.; Brandão, Teresa R. S.; Silva, C. L. M.
- Influence of drying processes and pretreatments on nutritional and bioactive characteristics of dried vegetables: a reviewPublication . Oliveira, Sara M.; Brandão, Teresa R. S.; Silva, Cristina L. M.Drying has been applied to vegetables in order to preserve, store and transport these food products. However, drying implies not only physical changes, easily detectable by the consumer through visual assessment, but also chemical modifications. These are not always visible,but are responsible for alterations in colour, flavour and nutritional value, which compromise the overall quality of the final product. The main chemical changes associated with drying are related to the degradation of phytochemicals, such as vitamins, antioxidants, minerals, pigments and other bioactive compounds sensitive to heat, light and oxygen. Moreover, nutrient losses are inevitably associated with leaching as a result of the water removal from the vegetable during the drying process. In order to prevent or reduce nutrient losses and thus improve the quality of dried products, pretreatments are often applied. In this review, an overview of the procedures developed for dehydration of vegetables applying heat by convection, conduction or radiation is presented. The influence of pretreatments on nutritional and bioactive characteristics of dried vegetables is discussed. Blanching with steam, water or chemical solutions is the most commonly used, but power ultrasound, ohmic blanching, osmotic and edible coatings pretreatments have also been reported. The influence of the drying processes and conditions on nutritional contents and bioactive characteristics is also presented.
- Thermal inactivation of Alicyclobacillus acidoterrestris spores in fruit product processingPublication . Brandão, Teresa R. S.; Silva, Cristina L. M.Alicyclobacillus acidoterrestris spores were recently proposed to be used as design criterion for thermal processes of acid fruit products. This microorganism has been found in commercial pasteurized acid fruit juices, such as orange and apple. Although being non-pathogenic and not easy to detect visually, it is responsible for off-flavours development. On the other hand, the first thermal inactivation kinetic studies confirmed that these spores are much more resistant than the usual spoilage microorganisms in acid foods. Therefore, in 2000 it was firstly proposed to be used in the design of hot-filling and continuous pasteurization conditions of a tropical fruit pulp and juice, respectively. This work presents a critical review on inactivation kinetics of Alicyclobacillus acidoterrestris spores. The available studies were obtained under thermal treatments, and studied the effects of temperature, pH and soluble solids. Those effects were quantified in terms of decimal reduction time (first order model) and z-values (Bigelow model). Furthermore, they were obtained under isothermal conditions. Future challenges in this field are to quantify the inactivation kinetics behaviour under dynamic conditions, using thermal and non-thermal treatments, such as ozonation, ultrasonication or high pressure. These alternative treatments have the advantage of minimizing quality attributes degradation and improving products. Moreover, predictive microbiology skills are suggested as a valuable tool for process design and optimization.
- Non-thermal technologies for Alicyclobacillus acidoterrestris inactivation in apple juicePublication . Tremarin, A.; Brandão, Teresa R. S.; Silva, Cristina L. M.
- Kinetics of quality changes of pumpkin (Curcurbita maxima L.) stored under isothermal and non-isothermal frozen conditionsPublication . Gonçalves, E.M.; Pinheiro, J.; Abreu, M.; Brandão, Teresa R. S.; Silva, C. L. M.The effects of freezing process and frozen storage at isothermal (−7, −15 and −25 °C) and non-isothermal (accelerated life testing with step-stress methodology; temperature range from −30 to −5 °C) conditions on pumpkin quality were investigated. Storage temperature conditions were selected to embrace the limits practiced in the cold chain. Quality changes, such as texture, colour CIE Lab and vitamin C (ascorbic acid) content, were evaluated for both frozen storage regimes. The freezing process (that included a pre-blanching step) and subsequent frozen storage had significant impacts on all quality parameters analysed. A fractional conversion kinetic model was adequate in colour, texture and vitamin C data fits. The storage temperature effect was successfully described by the Arrhenius law. This study shows that non-isothermal frozen storage has a marked effect on pumpkin quality.
- Evaluation of antibiotic resistance patterns of food and clinical Listeria monocytogenes isolates in PortugalPublication . Barbosa, Joana; Magalhães, Rui; Santos, Isabel; Ferreira, Vânia; Brandão, Teresa R. S.; Silva, Joana; Almeida, Gonçalo; Teixeira, PaulaThe aim of this study was to characterize a broad collection of isolates of Listeria monocytogenes, of different serotypes, recovered in Portugal between 2003 and 2007 from foods (n = 353) and from clinical cases of human listeriosis (n = 95), in terms of antimicrobial susceptibility. All the isolates were susceptible to ampicillin, the preferred agent to treat listeriosis. Resistances to nitrofurantoin (n = 99), to ciprofloxacin (n = 18), to erythromycin (n = 10), to tetracycline (n = 2), to gentamicin (n = 1) and to rifampicin (n = 1) were observed. One hundred (28.3%) and 20 (21.0%) food and clinical isolates, respectively, were resistant to at least one antibiotic. Eight isolates (1.8%) were resistant to two or more antimicrobials of different classes, and all were collected from foods. Serogroup IVb included the highest percentage of isolates resistant to erythromycin. The highest percentages of isolates resistant to nitrofurantoin were of serogroup IVb and IIc. It was demonstrated that the incidence of antibiotic-resistant isolates of L. monocytogenes, during the period 2003 to 2007, was low in Portugal but still higher than that observed in other countries. Given the increasing population at greater risk of listeriosis, namely, the elderly, the high mortality rate of the infection and the detection of resistant isolates, monitoring for antibiotic resistance in strains of L. monocytogenes on a large scale, and assessing the risk of infection by these strains, is highly recommended.
- Thermal and non-thermal Cantaloupe melon juice pasteurization: Assessment of the impact of ozone exposure on microbiological, physicochemical and bioactive characteristicsPublication . Sroy, Sengly; Fundo, Joana F.; Miller, Fátima A.; Brandão, Teresa R.S.; Silva, Cristina L. M.
- Fresh fruits and vegetables – An overview on applied methodologies to improve its quality and safetyPublication . Ramos, B.; Miller, F. A.; Brandão, T. R. S.; Teixeira, P.; Silva, C. L. M.The consumers' demand for fresh fruits and vegetables has increased in recent years. These foods may be consumed raw or minimally processed, and therefore can be a vehicle of several pathogens. The microorganisms most frequently linked to produce-related outbreaks include bacteria (Salmonella spp., Listeria monocytogenes, Escherichia coli, and Shigella spp.), viruses and parasites. There are many traditional technologies to reduce/eliminate the microorganisms present in food products. However, further research on this topic is still required, since none of the methods reported can control all the parameters necessary to achieve produce with an extending shelf-life, without compromising its quality. In this paper, an analysis of the alternative and traditional methodologies is made, pointing out the significant advantage and limitations of each technique. Industrial relevance: The significant increase in the incidence of foodborne outbreaks caused by contaminated minimally processed produce in recent years has become of extreme importance. The extensive knowledge of gentle (non-thermal) processes to enhance safety, preservation and shelf-life of these products is crucial for the food industry. This manuscript presents non-thermal processes that have shown efficient microbial reductions on fresh produce and highlights some of their challenges and limitations.