Browsing by Author "Brito, Mariana"
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- Effect of Drying Temperature on the Physical-chemical and Sensorial Properties of Eggplant (Solanum melongena L.)Publication . Guiné, Raquel; Correia, Paula; Correia, Ana Cristina; Gonçalves, Fernando; Brito, Mariana; Ribeiro, JéssicaBackground: Eggplant is an important crop, being cultivated and consumed in many countries. However, like other vegetables, is highly perishable and has a short shelf life. Objective: The objective of this study was to evaluate the effect of hot air drying on some physical, chemical and sensorial properties of eggplant. Methods: Eggplant samples were dried in convective chambers at constant temperatures of 50, 60, 70 and 80°C. The fresh and dried samples were evaluated for moisture, water activity, vitamin C, total phenolic compounds, antioxidant activity, colour and texture. To complement the study, a sensorial evaluation was made by a consumer panel. Results: The results showed that drying decreased importantly the contents of vitamin C and phenolic compounds as well as antioxidant activity. Moreover, the negative impact was higher for higher drying temperatures. Drying also altered the colour, turning the samples darker. The textural properties were similarly considerably altered by drying, although the temperature did not show significant influence. Regarding the sensorial evaluation, even though it allowed establishing the sensory profiles of the dried samples, it was not possible to clearly distinguish among them, particularly the global appreciation. Conclusion: It was concluded that the drying operation substantially changed the physical, chemical and sensory properties of eggplant. Furthermore, the drying temperature had higher effect on the chemical components and colour and nor so much on the texture.
- Effect of drying on the physical, chemical and sensorial properties of kiwiPublication . Correia, Paula; Guiné, Raquel; Correia, Ana Cristina; Brito, Mariana; Ribeiro, Jéssica; Gonçalves, FernandoKiwi fruit is a highly nutritional fruit due to the high level of vitamin C and its strong antioxidant capacity due to a wide number of phytonutrients including carotenoids, lutein, phenolics, flavonoids and chlorophyll [1]. Drying consists of a complex process in which simultaneous heat and mass transfer occur. Several alterations occur during the drying of foods at many levels (physical, chemical, nutritional or sensorial) which are influenced by a number of factors, including processing conditions [2]. Temperature is particularly important because of the effects it produces at the chemical and also at the physical level, particularly colour and texture [3]. In the present work were evaluated the changes in sliced kiwi when exposed to air drying at different temperatures (50, 60, 70, 80 ºC), namely in terms of some chemical properties like ascorbic acid or phenolic compounds, physical characteristics like colour and texture and also at the sensorial level. All experiments followed standard established procedures and several replicates were done to assess each property. The results obtained indicated that moisture was reduced with drying by 74 to 87%, depending on the temperature. Also ascorbic acid decreased with drying, being 7% for 50 ºC and increasing up to 28% for the highest temperature (80 ºC). The phenolic compounds and antioxidant activity were also very much affected by the drying temperature. The water activity of the dried samples varied from 0.658 to 0.753, being compatible with a good preservation. Regarding colour, the total colour difference between the dried samples and the fresh sample was found to vary in the range 9.45 – 17.17. The textural parameters were also much affected by drying, namely hardness which decreased by 45 to 72 %, and all other parameters increased: cohesiveness (approximately doubled), springiness (increased 2 to 3 times) and chewiness which increased up to 2.5 times that off the fresh sample. Adhesiveness, which was observed for the fresh samples (-4.02 N.s) disappeared in all the dried samples. The sensorial analysis made to the dried samples allowed establishing the sensorial profiles as shown in Figure 1.
- Evaluation of some physical, chemical and sensorial properties of eggplant submitted to different drying treatmentsPublication . Guiné, Raquel; Correia, Paula; Correia, Ana Cristina; Gonçalves, Fernando; Brito, Mariana; Ribeiro, JéssicaDrying is the oldest method for food preservation, which people learned from nature, and has been using since ancient times. In Turkey, for example, eggplants are dried in the sun hung up with a string. Although it is a very economic method, it has many disadvantages and has been replaced by other drying methods, like hot air drying. This work intended to analyse the differences originated by drying in eggplant slices when submitted to different temperatures (50, 60, 70, 80 ºC). The characteristics evaluated were some chemical properties (moisture, water activity and vitamin C, total phenols and antioxidant activity), physical characteristics (colour coordinates and textural parameters) also at the sensorial level. All experiments followed standard established procedures and the values obtained resulted from the calculation of the mean and standard deviation considering the different replicates made. The results showed that the moisture varied from 90% in the fresh sample to 16-26% on the dried samples, depending on the temperature. The water activity of the dried samples varied from 0.96 in the fresh sample, a high value that allows degradation of the product to a value in the range 0.63-0.76 for the dried samples, allowing a better preservation. The vitamin C, which is a thermosensitive vitamin, decreased with drying, with variations going from 41% at 50 ºC to 74% for the highest temperature (80 ºC). The contents of phenolic compounds and the antioxidant activity were also influenced by drying temperature. The total colour difference between the dried samples and the fresh sample was found to vary in the range 17.5 – 18.8. As expected, also texture was considerably altered with drying. Hardness decreased (by 16-20%), and so did adhesiveness or cohesiveness while elasticity increased from the fresh to the dried samples. The sensorial analysis made to the dried samples allowed concluding that the sample dried at 70 ºC was slightly more appreciated by the panellists.
- Physical, chemical and sensory properties of kiwi as influenced by drying conditionsPublication . Correia, Paula; Guiné, Raquel; Correia, Ana Cristina; Gonçalves, Fernando; Brito, Mariana; Ribeiro, JéssicaThe present study aimed at studying the effect of convective air drying on some physical, chemical and sensory properties of kiwi (Actinidia deliciosa L.) samples. The kiwi samples were dried in thin layer convective chambers set to constant temperatures at 50ºC, 60ºC, 70ºC and 80ºC. The fresh samples and the dried samples were analysed for moisture, water activity, vitamin C, total phenolic compounds, antioxidant activity, colour and texture. Also the different dried samples were submitted to a sensory evaluation. It was concluded that drying of kiwi importantly decreased the contents of some bioactive components such as vitamin C and phenolic compounds as well as the antioxidant activity. Moreover, the negative impact was higher at higher drying temperature. Drying also altered the colour towards a lower intensity of the green colouration and a higher intensity of the yellow. In what concerns the textural properties, drying produced important alterations, however the influence of temperature was not visible. Regarding the sensory evaluation, it was not possible to clearly distinguish the samples analysed, particularly in what related to the global appreciation. Still, it was possible to establish the sensory profiles of the dried samples, and the attributes that varied most among them were colour intensity, crunchiness and hardness.