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- Influence of pretreatments on quality parameters and nutritional compounds of dried galega Kale (Brassica oleracea L. var. acephala)Publication . Araújo, Ana C.; Oliveira, Sara M.; Ramos, Inês N.; Brandão, Teresa R. S.; Silva, Cristina L. M.The objective of this work was to evaluate the effect of six pretreatments on quality and nutritional contents of sliced Galega kale submitted to convective drying. Among all treatments, steam blanching was the most favourable, allowing improvements in retention of vitamin C, total antioxidant capacity and chlorophylls in comparison to the absence of pretreatment. Total phenolic losses were not reduced by steam blanching, but the retention was improved by combining this approach with a previous immersion in a metabisulphite solution. Moreover, steamblanching improved the colour parameters and appearance, providing a final dried product more similar to the fresh sample.
- Influence of air-drying temperature on the quality and bioactive characteristics of dried galega kale (Brassica Oleracea L. Var. Acephala)Publication . Oliveira, Sara M.; Ramos, Inês N.; Brandão, Teresa R. S.; Silva, Cristina L. M.Drying processes are often applied to preserve and increase the shelf life of vegetables. These products contain an extensive collection of phytochemicals known to provide health benefits. However, these compounds generally undergo significant degradation during drying because of their sensitivity to heat, light, oxygen, as well as to leaching phenomena. Thus, increased attention has been given to the concerns regarding the quality degradation of vegetables during drying. Galega kale was selected, since this leafy vegetable, often included as soups ingredient, presents high amounts of vitamins and micronutrients. The objective of this work was to evaluate the drying characteristics and the effect of drying temperature on quality characteristics of Galega kale, without any pretreatment. Drying times of 330, 162, 78 and 51 min provided minimal moisture contents, using temperatures of 35, 50, 70 and 85 ⁰C, respectively. Increasing air-drying temperatures originated significant changes in color and nutritional parameters. The L* and a* values diminished, and b* increased, originating increasing values of chroma, total colour difference and browning index, as well as decreasing values of hue angle. A pronounced effect on the retention of total phenolic compounds was observed. Regarding antioxidant capacity and vitamin C, losses of 51.7±7.5- 69.6±3.7 and 4.8±9.7-55.5±7.4% were obtained, respectively. Chlorophyll a content decreased with increasing drying temperatures, with losses between 8.9±6.7 and 35±5.6%, while degradation of chlorophyll b was negligible. In conclusion, the air-drying of Galega kale without any pretreatment resulted in considerable deterioration of its quality characteristics and nutritional value.
- Effect of pretreatments on quality parameters and nutritional compounds of dried Galega kale (Brassica Oleracea L. Var. Acephala)Publication . Araújo, Ana C.; Oliveira, Sara M.; Ramos, Inês N.; Brandão, Teresa R. S.; Silva, Cristina L. M.Galega kale (Brassica Oleracea L. var. Acephala) is a vegetable quite common in several countries. It presents high moisture content at harvest, so it can only be preserved for a few days under room temperature. Therefore, drying processes can be employed to increase its shelf-life. However, drying exposes the product to high temperatures that can result in some losses of flavour, texture, colour and nutrients. To minimize these detrimental effects, several pretreatments may be used as possible strategies to improve nutritional attributes and sensory properties, after dehydration and during long-term storage. The objective of this work was to evaluate the effect of six pretreatments on quality and nutritional contents of Galega kale submitted to convective air drying. Water and steam blanching, simple or combined with chemical treatments, were applied to kale samples before convective drying. When compared to the absence of pretreatment, steam blanching provided improvements on retention percentages of 7.3 and 13.6% for vitamin C and total antioxidant capacity, respectively. Regarding pigments, steam blanching enabled higher retention of total chlorophylls. Total phenolic content was the only nutritional parameter in which steam blanching preceded by chemical treatment with metabisulfite provided better results than isolated steam blanching. Steam blanching for 1 min, without the need of previous chemical treatment, applied to kale samples before drying, demonstrated to be a valuable approach to reduce deterioration of the majority of the parameters in study, and also improved significantly the appearance of Galega kale after the drying process.