Showing papers by "Raquel Guiné published in 2014"

Effect of drying temperatures on the phenolic composition and antioxidant activity of pears of Rocha variety (Pyrus communis L.)

Abstract: The interest about phenolic compounds and antioxidant activity has been increasing in recent years, mainly due to their beneficial effects on human health, focusing on many different food products. In this way, and since pears are an important source of dietary intake of phenolic compounds with antioxidant activity, this work was done to evaluate the phenolic content and antioxidant activity of pears of cv. Rocha from five different locations and submitted to drying at different temperatures (40 and 60 °C). Although the amounts of phenolic compounds are not very much influenced by drying, the antioxidant capacity does suffer a very marked decrease with drying at both temperatures, when compared to that of the fresh pears. The HPLC analysis of the phenolic extracts allowed identifying some phenolic compounds present in the pears, such as arbutin, gallic acid, chlorogenic acid, syringic acid, protocatechuic acid, catechin and epicatechin. From the results obtained in this study it was concluded that the greatest variations occurred in the peel of the pears, as compared to the corresponding pulps. Furthermore, it was possible to observe that while total phenols and ortho-diphenols do not seem to be very affected by drying, the antioxidant capacity suffers a great decrease with drying, being this effect more pronounced when the drying temperature is increased.

Influence of drying treatments on the physical and chemical properties of cucumber

Abstract: This work aimed at determining the properties of cucumber exposed to convective air drying and freeze-drying. The samples were analysed in terms of colour, texture, chemical properties (moisture content, fibre, ash, vitamin C and sugars), phenolic compounds and antioxidant activity in fresh and after drying. The trials in the convective chamber were done at 40 and 60 °C, in the drying tunnel at 60 °C and in the freeze dryer at −50 °C. The results showed that the antioxidant activity and the phenolic compounds were not affected by any of the drying treatments tested, since the values were quite similar in the fresh product as compared to the dried cucumbers. With respect to colour, the freeze drying treatment was identified as the one originating less colour change, when compared with the colour of the fresh product. Finally, texture was less affected by drying in the chamber at 40 °C and freeze drying.

Convective Drying of Apples: Kinetic Study, Evaluation of Mass Transfer Properties and Data Analysis using Artificial Neural Networks

Abstract: Abstract In the present work, the effect of drying was evaluated on some chemical and physical properties of apples, and the functions were modelled using feed-forward artificial neural networks. The drying kinetics and the mass transfer properties were also studied. The results indicated that acidity and sugars were significantly reduced by drying. Regarding colour lightness decreases, whereas redness and yellowness increased. As for texture, the dried samples were softer and less cohesive as compared to the fresh ones. Mass diffusivity increased with temperature, from 4.4×10−10 m2/s at 30°C to 1.4×10−9 m2/s at 60°C, and so did the mass transfer coefficient, increasing from 3.7×10−10 m/s at 30°C to 7.4×10−9 m/s at 60°C. As to the activation energy, it was found to be 34 kJ/mol. Neural network modelling showed that all properties can be correctly predicted by feed-forward neural networks. The analysis of the networks’ behaviours input layer weight values also shows which properties are more affected by dehydration or more dependent on variety.

Physical, chemical and sensorial properties of healthy and mixture breads in Portugal

Abstract: This study was conducted to characterize different samples of regional bread made from mixed rye and wheat flours and healthy bread produced from a special formulation. The bread samples were evaluated in terms of their physical, chemical and sensory properties following the standard methods. The regional breads showed some differences in the chemical composition: Flor de Carregal had the highest protein content (14.59 %) and the lowest salt content (0.40 %), Pedregal had the highest fibre content (0.89 %), and Pazurara was the richest in minerals (4.90 %). Although the sensory properties of bread samples were not statistically different, Flor de Cabanas obtained the highest overall acceptability among the samples (6.95 points). With respect to the healthy bread samples, slight differences were observed on their physical and sensory properties, which may attributed to their similarity in ingredient compositions. Furthermore, significant differences were observed from the fiber, carbohydrate, protein and chloride contents of healthy bread samples. In comparison with the two types of breads, it was found that they have different chemical, physical and sensory properties. Sensory analysis also showed that regional breads were more preferred by the panellists, with an average punctuation for global appreciation of 5.83 against 4.71.

Phenolic compounds and antioxidant activity in red fruits produced in organic farming.

Abstract: Summary In this work were studied three red fruits (raspberry, gooseberry and blueberry) produced in organic mode, to evaluate the variations in the content of phenolic compounds and antioxidant capacity along maturation. The phenols were extracted from the fruits with two solvents (methanol and acetone) and were quantified by the Folin-Ciocalteu method. The antioxidant activity was determined with two methods (HPPH and ABTS). Furthermore, HPLC was used to identify and quantify some phenolic compounds present in the fruits analyzed. The results showed that the total phenolic compounds in all fruits decreased along maturation, either in the methanol or acetone extracts (23 % and 20 % reduction, on average, for methanol and acetone extracts, respectively), although in methanol extracts the levels of phenolic compounds were always higher (0.54 and 0.21 mg GAE/g). The blueberry showed higher level of total phenolics in methanol extract (average 0.67 mg GAE/g), while in the acetone extract it was gooseberry (average 0.31 mg GAE/g). At the end of maturation, all fruits studied had similar values of antioxidant capacity as determined by DPPH method (0.52 mmol Trolox/g). For the ABTS method, blueberries showed higher values of antioxidant activity (6.01 mmol Trolox/g against 3.01 and 2.66 mmol Trolox/g, for raspberry and gooseberry, respectively). Furthermore, the HPLC analysis allowed to identify monomeric anthocyanins and phenolic acids in the three fruits studied.

Quantification of browning kinetics and colour change for quince (Cydonia oblonga Mill.) exposed to atmospheric conditions

Abstract: Because quince is a fruit that shows a very strong tendency for developing an intense browning when exposed to air, even though for short periods of time, the aim of this work was to evaluate the kinetics of colour change for quince exposed to atmospheric air at ambient temperature over a period of 2 hours. The quince was cut into slices that were left exposed to air, and colour measurements were done right after cutting and every 5 min, using a tristimulus colorimeter measuring the CIELab coordinates, L*, a* and b*. The results confirmed that quince suffers a high degree of browning, with total colour difference increasing strongly from 0 to 30 and browning index increasing from 50 to near 140. Furthermore, the major colour changes occurred during the first 30 min of exposure. Different models were tested to fit experimental data and the results showed that the most commonly used models, zero-order and first-order kinetics were totally inadequate in the present case, while the less cited models revealed to be very good at describing the kinetics of colour change for quince: logistic, modified Maskan and exponential rise. Quince (Cydonia oblonga Mill.) is original from Kydonia on the island of Crete, and has evolved into the fruit we know today, as cultivated in the Mediterranean area, with a shape somewhere between an apple and a pear. In the raw form, the rind is rough and woolly, and the flesh is hard and unpalatable, with an astringent, acidulous taste. Because they are rarely used in the raw form, quinces are commonly transformed into jams and jellies. Once cooked and sweetened, they turn red, taste divine and have a strong pleasant fragrance. Sometimes the quince smells like a tropical fruit. When prepared as jelly, it tastes like a cross between an apple and a pear.

Adsorption Isotherms of Maria Biscuits from Different Brands

Abstract: This study aimed to determine the adsorption curves of Maria biscuits from different 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 temperature, 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. Practical Applications The importance of stability for bakery products is critical for the maintenance of physical–chemical properties, and in particular to avoid spoilage and maintain texture. Biscuits are very hygroscopic and therefore, if not properly stored, tend to absorb water from the air, thus compromising texture. Knowledge about adsorption isotherms provides valuable information regarding the stability of products under some conditions. Therefore, the study undertaken in this work could be utilized to select the best storage and package conditions so as to improve product quality, moreover because Maria biscuits are largely consumed and appreciated for their crispy texture.

Evaluation of the Browning Kinetics for Bananas and Pears Submitted to Convective Drying

Abstract: The aim of this work was to evaluate the kinetics of colour change for bananas and pears dried in hot air at different temperatures, and also to test different kinetic models to verify which describe best the experimental data. Banana fruits from Madeira island and Costa Rica were and pears from cultivar D. Joaquina were peeled, cut and dried with hot air at 0.5 m/s and temperatures ranging from 50 to 70 oC, until reaching a final moisture content lower than 10% (wet basis). Along drying colour measurements were done using a tristimulus colorimeter measuring the CIELab coordinates, L*, a* and b*. The experimental data was then fit to different kinetic models found in literature (first order, second order and exponential rise functional). The results obtained showed that bananas undergo a more intense color change than pears. It was further observed that the increase in drying temperature lead in general to an increase in the colour degradation, being this effect more pronounced in the pears. As to the kinetics of color change, the exponential rise function showed the best fitting, and the values of the kinetic constant found with this model varied from 5.7023x10 to 1.0086 h.

Influence of different processing parameters in physical and sensorial properties of Serra de Estrela cheese

Abstract: Cheese is a classical dairy product, which is strongly judged by its appearance, flavour and texture. Processing parameters that could affect cheese structure play a dominant role upon the features exhibited by the final product. Serra da Estrela cheese is a Protected Denomination of Origin (PDO) cheese manufactured from raw ewes ‘milk and curdled with thistle flowers. The study aimed to evaluate cheeses physicochemical, microbiological and sensorial properties, produced with two thistle flowers ecotypes added in different quantities to milk, sheep bread, salt quantity and ripening moisture. Two dairies were involved in this study, named as A and B, both with certification. The sheep milk chemical composition (moisture, protein, fat, solids-non-fat, lactose, solids, density, freezing point), and microbial analysis (coliforms and total enumeration of microorganism at 30 0C) were determined, using respectively a Lactoscan equipment and norms ISO 4832:2006 and 4833-1:2013. The clotting time, the evolution of weight loss and color, the texture (texturometer TA-XT Plus) and sensorial characteristics of cheeses were evaluated. Both dairies presented similar chemical sheep milk composition and clotting time for the same thistles flower, varying from 36-47 minutes. The loss of weight showed similar decreasing and tendency. Generally, the thistle flower ecotype didn’t influence the L, a* and b* color parameters, during the ripening process and in the final product there was a significant influence on a* parameter. The textural analysis revealed significant differences between the two dairies for the same thistle flower ecotype, considering the inner firmness, stickiness and adhesiveness. Cheeses presented similar sensorial properties, considering the different processing parameters studied. Serra da Estrela cheese produced in both dairies presented different physical and sensorial properties, meaning that with a strong knowledge of the properties assign by processing parameters it is possible to produce a specific cheese attending to different consumer targets.

Effect of packaging and conservation conditions on some physical-chemical properties of almonds.

Abstract: Food quality is a concept that has attracted the attention of Industries and consumers, hence the concern to preserve the products under appropriate conditions, avoiding physical and chemical changes that jeopardize the integrity of the food. In this context, assessments were made of the physical and chemical properties in order to investigate the effects of storage in almonds, under certain conditions of temperature, relative humidity and packaging. The almonds used were from different origins, namely Spain, Portugal and United States and the conservation processes tested were: storage at room temperature, in a stove at 30 and 50 0C without control over relative humidity, in a chamber at 30 and 50 0C with relative humidity of 90%; refrigeration and freezing. The packages used were two types of plastic: linear low density polyethylene (LLDPE) and low density polyethylene (LDPE). The properties evaluated were moisture content, water activity, color and texture. The principal results show that the storage conditions that best preserve the characteristics of almonds are those at low temperatures, because, while the treatments at high temperatures induced in general more changes, the refrigeration and freezing systems had a lower effect on the products characteristics, particularly moisture, water activity, hardness and friability. From the results obtained it was concluded that for a good preservation of almonds during storage should be used a packaging material, preferably LDPE, and that with respect to storage conditions the best methods are at room temperature or, alternatively, in refrigeration or freezing.

Effect of pre-treatment on some physical-chemical properties of dried carrots.

Abstract: Carrot is the most commonly used vegetable for human nutrition and is an excellent source of β-carotene, vitamin A and potassium, and contains cholesterol-lowering pectin, vitamin C, vitamin B6, thiamine, folic acid, and magnesium. Carrots are highly seasonal and abundantly available at particular times of the year. For extending the availability of this root, several preservation processes can be used, but convective drying is one of the most important since it not only extends vegetable shelf life significantly but also diversifies the offer of foods for consumers. However, convective drying can also give rise to significant chemical changes (non-enzymatic browning, among others), which may affect the quality of the product. Pre-drying treatments of solid food products can be used as a way to augment product quality and to modify the structure of food products so as to improve mass transfer coefficients in drying. In this context, assessments of the physical and chemical properties were made in order to investigate the effects of sodium metabisulphite at different concentration/time combinations prior convective drying of carrots. The carrots used in this study were purchased in a local market, and hand peeled and cut into slices with thickness of 10 mm. Before convective drying at 60 0C the slices of carrots were submitted to pre-treatments as follows: a) dipping in a water solution of 0.25% of sodium metabisulphite for 60 and 90 min. and 1% of sodium metabisulphite for the same times, at room temperature; b) dipping in an equal mass of plain water for 60 and 90 min. at room temperature (as control sample). Some chemical properties of the fresh and dried samples were evaluated with classical methods, namely moisture content, fiber, ashes and sugars (reducing, total and non-reducing sugars). The physical properties evaluated were color and texture. Color was evaluated with a Colorimeter in the CieLab color space and texture was measured Color was evaluated with a Colorimeter in the CieLab color space and texture was measured by texture profile analysis with a texturometer. The main results show that the different combinations concentration/time of sodium metabishulphite dipping has a similar effect on the chemical properties of the dried carrots. Furthermore, the dried slices of carrots with and without pre-treatment originated products with similar nutritional characteristics. With respect of color, the total difference of color and browning index was similar to the different solutions of sodium metabishulphite. In addition the browning of the dried carrots was, apparently, independent of the pre-treatment. Similarly, the different combinations of pre-treatment had no visible effect on textural parameters and generally the hardness decreased with the pre-treatments. From the obtained results it was concluded that the different concentration/time combinations of sodium metabisulphite solutions had no visible improvement on the quality of the dried carrots.

Port Wine “Caviar”: Product Development, Sensorial Analysis, and Marketing Evaluation

Abstract: The aim of this work was to develop a new product, port wine “caviar,” consisting of products based on red and white port wines used in different concentrations. Sample R+ consisted of red port wine at a concentration of 90%, sample R- was red port at 75%, sample W+ was white port at 90%, and sample W- was white port at 75%, all (m/m). The use of two types of port is related to different colors and the two concentrations related to the intensity. The results from the sensory analysis showed that the red port “caviar” at 90% was the best among the products tested, either in the preference test or in the evaluation of the individual characteristics. Furthermore, the market study revealed that this product can be successfully commercialized, particularly for the gourmet kitchen, which is one the main usages identified by the respondents.

Estudo de Mercado sobre a Aceitação de um Novo Sabonete de Vinho do Porto

Abstract: O vinho do Porto e um dos principais produtos Portugueses exportados sendo consumido atualmente em quase todo o mundo. Este facto deve-se a sua elevada qualidade e as suas caracteristicas proprias que fazem dele um vinho inconfundivel e historico e sem duvida uma referencia mundial na area da e da enologia. Este trabalho teve como intuito o desenvolvimento de um produto, neste caso, um sabonete a partir do vinho do Porto. Para a sua producao utilizou-se como base glicerina solida, creme hidratante sem odor, com o objetivo de conferir propriedades hidratantes, e essencia de sândalo, que vai conferir ao sabonete um odor agradavel e duradouro na pele. Atraves da analise sensorial foram comparadas duas amostras com a mesma composicao basica, diferindo apenas porque uma delas continha vinho do Porto e a outra nao. Confirmou-se que os consumidores tem uma preferencia pelo sabonete elaborado a partir do vinho do Porto.

Evaluation of preservation conditions on nuts properties.

Abstract: Dried fruits like nuts are very much appreciated, but because of their hygroscopicity may be susceptible to undesirable changes during storage. Therefore, this work was undertaken to study the effect of different storage conditions on three types of nuts commonly consumed in Portugal (almond, hazelnut and walnut). The samples were originated from different countries and while most had the internal skin on, one sample had it off. The storage conditions tested were: ambient temperature, high temperatures (30 and 50 °C) and low temperatures (refrigeration at + 2 °C and freezing at – 15 °C). The characteristics evaluated were water activity, moisture content, colour and texture. The results obtained in the present work allowed concluding that the storage conditions that best preserve the characteristics of nuts are those at low temperatures, because, while the treatments at high temperatures induced in general more changes, the refrigeration and freezing systems had a lower effect on the products characteristics, particularly moisture, water activity, hardness and friability. Also the results indicate that the nuts stored under all conditions tested had values of water activity lower than 0.6, thus guaranteeing stability at the microbial and enzymatic levels. It was further concluded that the internal skin had a great influence on the characteristics of the nuts, particularly texture and colour, for all treatments tested.

Family and organic farming. New apprenticeship through m-learning

Abstract: The benefits that may accrue from the adoption of organic farming on family farms in Mediterranean countries such as Portugal, Italy and Spain are analysed, together with its impact and major constraints, as well as the contribution that new forms of teaching and learning can give to its spread and success, including through m-learning, as it is the case of the project ECONewFARMERS Building a future for new farmers in ecological farming through vocational training.

Contribution for physical characterization of aromatic rice

Abstract: Rice is consumed mainly as whole grain, and quality considerations are much more important than for any other food crop. Rice grain quality preference varies from country to country and among regions. Nowadays, aromatic rice varieties are playing a vital role in global rice trading, and also in Portugal. The economic value of rice depends on its cooking and processing quality, such us water uptake ratio, cooking time and texture properties. Three types of aromatic rice were collected and analyzed for biometry characteristics, cooking time, water absorption, and texture properties. The rice grains were collected from the Portuguese trade market. Biometric characteristics of all rice grains were evaluated by S21 (LKL) and C-300 (Kett) colorimeter. The rice flour gels texture was performed by a TPA (texture profile analysis), giving information about adhesiveness, chewiness, gumminess, hardness, resilience and cohesiveness. The extrusion force was also determined according to ISO 11747:2012. Rice samples are commercially classified as long grains B type, because they presented a length higher than 6 mm and the ratio length/ width higher than 3. The samples presented a high degree of whiteness, with a strictly relationship between the total and vitrea whiteness (r2 = 0.95). The cooking time varied from 12 to 17 minutes and these properties was strongly related with water uptake (from 155.7 209.1 g). Generally, aromatic rice cultivars presented different textural properties. Aromatic rice samples are different for hardness, adhesiveness, gumminess, resilience, and extrusion force. From the results obtained it was concluded that the studied aromatic rice cultivars presented different physical properties, mainly the cooking time, water uptake and texture. These differences could be a commercial advantage considering the consumer point of view, because the enterprise could provide specific aromatic rice in order to attend different consumer targets.

Determination of the content of coenzymes Q9 and Q10 in pork meat from different breeds.

Abstract: Meat contains basic and essential nutrients to humans, and recently has been given a special attention to the presence of bioactive compounds. The objective of this work was the simultaneous determination of coenzymes Q9 and Q10 in pork meat, using HPLC. For this study were used 122 meat samples from different muscles and different breeds of pork. Besides, it was also evaluated the influence of animal breed and muscle type in the contents of CoQ9 and CoQ10. The results showed that the breed influenced significantly the mean content of CoQ9 (0.70 mg 100 g -1 ) and CoQ10 (3.76 mg 100 g -1 ) (p<0.0001), being this significantly higher in the meat from the breed ‘ Alentejano’ when compared to the other breeds (Large White and Landrace). The type of muscle was also responsible for the variation in the levels of coenzymes in the samples analysed (p<0.05) and (p <0.0001) respectively. From the results obtained it was concluded that the breed ‘Alentejano’ presented the highest contents in both coenzymes (CoQ9 and CoQ10) and that, among the muscles evaluated, the muscle Semimembranousus (Sm) showed higher concentrations of CoQ10.

Estudo de mercado sobre a aceitação de um novo sabonete de vinho do porto market study about the acceptance of a new port wine soap

Abstract: Resumo O vinho do Porto e um dos principais produtos Portugueses exportados sendo consumido atualmente em quase todo o mundo. Este facto deve-se a sua elevada qualidade e as suas caracteristicas proprias que fazem dele um vinho inconfundivel e historico e sem duvida uma referencia mundial na area da e da enologia. Este trabalho teve como intuito o desenvolvimento de um produto, neste caso, um sabonete a partir do vinho do Porto. Para a sua producao utilizou-se como base glicerina solida, creme hidratante sem odor, com o objetivo de conferir propriedades hidratantes, e essencia de sândalo, que vai conferir ao sabonete um odor agradavel e duradouro na pele. Atraves da analise sensorial foram comparadas duas amostras com a mesma composicao basica, diferindo apenas porque uma delas continha vinho do Porto e a outra nao. Confirmou-se que os consumidores tem uma preferencia pelo sabonete elaborado a partir do vinho do

Comparative evaluation of Portuguese goat and sheep cheeses

Abstract: Resumo Seis queijos portugueses produzidos unicamente com leite de ovelha ou de cabra, adquiridos numa grande superficie, foram avaliados ao nivel fisico (textura e cor), quimico (humidade, aw, cinzas proteina e gordura) e sensorial (perfil de preferencia) Ao nivel quimico, os resultados obtidos revelam alguma variabilidade entre amostras por tipo de queijo, sendo a amostra de queijo de ovelha V a que apresentou valores de proteina e gordura mais elevados, 29,7% e 63,5%, respetivamente Tambem foi essa amostra que, ao nivel dos parâmetros fisicos avaliados, se destacou das restantes, sendo a mais corada, com maior dureza, mastigabilidade, gomosidade, maior firmeza da casca e da pasta Contudo, ao nivel sensorial foi a amostra com menor preferencia dos provadores

Influence of pre drying treatment on physical properties of carrots.

Abstract: In the present work, the effect of pre-treatment with ascorbic acid on colour changes and texture was investigated during convective hot air drying at 60oC. The pre-treatments were done at 0.25% and 1 % of ascorbic acid with treatment times of 60 and 90 minutes. Changes in colour and total colour difference were evaluated by the CIELab colour system and texture of dried carrots was accessed in terms of hardness, springiness, and cohesiveness.Regarding the total colour difference, soaking carrots in ascorbic acid at both concentrations and treatment times turned out to be an ineffective method for reducing the browning reactions during drying. With respect to textural attributes non-significant differences were observed in springiness and cohesiveness of untreated and pre-treated dried carrots but the hardness increased at a pre-treatment time of 90 minutes.