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Evaluation of drying and storage conditions on nutritional and sensory properties of dried galega kale (Brassica oleracea L. var. Acephala)

Publication . Araújo, Ana C.; Oliveira, Sara M.; Ramos, Inês N.; Brandão, Teresa R. S.; Monteiro, Maria J.; Silva, Cristina L. M.

This work evaluated the effect of the air-drying temperature and vacuum packaging on quality and nutritional compounds of dehydrated galega kale, previously steam blanched, during 5 months of storage. When compared with the vacuum packaged kale, the packaging without vacuum yielded improved nutritional features, in general. This approach combined with a drying temperature of 40°C resulted in retention percentages of 62, 38, 92, and 48% for vitamin C, total phenolic content, total antioxidant capacity, and chlorophylls, respectively. The acceptance of the dried product by the consumer was assessed through a focus group. The participants classified the product as a practical and convenient alternative to cook healthier dishes. The appearance of dried galega kale was described as being fragile and being with nice smell, natural colour, and flavour similar to the fresh product. In conclusion, the herein presented product was addressed as an innovation with multiple possible applications in several recipes.

2017Journal article

Open access

Simulation of solar drying of grapes using an integrated heat and mass transfer model

Publication . Ramos, Inês N.; Brandão, Teresa R. S.; Silva, Cristina L. M.

A mathematical model was developed to simulate solar drying of grapes, integrating heat and mass transfer models solved by an explicit finite differences method, considering changing boundary conditions. The model simultaneously incorporated shrinkage of the product, changes in effective moisture diffusivity and dependence of thermal properties on water content and temperature. Field experiments were carried out in a mixed mode solar dryer located in the North of Portugal, with pre-blanched grapes. A good prediction of experimental solar drying curves was attained. The mathematical model can be applied for simulating solar drying of different foods, once known their specific thermo-physical properties. Simulations obtained with the developed model can be valuable for predicting accurate drying times and consequently to design, control and optimise the production of dried foods.

2015Journal article

Restricted access

Effect 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.

The objective of this work was to evaluate the drying characteristics and the effect of drying temperature on the 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 85C, respectively. The L* and a* values diminished and b* increased, resulting in increasing values of chroma, total color difference and browning index, as well as decreasing values of the hue angle. A pronounced effect on the retention of total phenolic compounds and vitamin C losses ranging from 4.8 ± 9.7 to 55.5 ± 7.4% were observed. Regarding antioxidant capacity, losses from 51.7 ± 7.5 to 69.6 ± 3.7% were obtained. 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.

2015Journal article

Restricted access

Effect of pre-treatments on solar drying kinetics of red seedless grapes (cv. Monukka)

Publication . Ramos, Inês N.; Brandão, Teresa R. S.; Silva, Cristina L.M.

Two di erent pre-treatments were applied to grapes prior to drying in a mixed mode solar dryer. Grapes were blanched in water and in a 0.1% sun ower oil water emulsion, both at 99 C and for approximately 15 seconds. Several models were tested to t the experimental data of drying curves but the normalized Newton model gave the best t results. Samples blanched in hot water or in the 0.1% edible oil emulsion had faster drying rates than untreated samples. Contrary to what was expected, pre-treating with the 0.1% edible oil emulsion did not increase the drying rate to a higher extent than blanching. Pre-treatments did not give a noteworthy di erence in the total drying time. However, they had an important role in accelerating initial drying rates, thus preventing moulds and bacterial growth and consequently increasing farmers' income.

2014Journal article

Open access

Assessment of nutritional quality and color parameters of convective dried watercress (Nasturtium officinale)

Publication . Ek, Pichmony; Araújo, Ana C.; Oliveira, Sara M.; Ramos, Inês N.; Brandão, Teresa R. S.; Silva, Cristina L. M.

The purpose of this study was to evaluate the drying characteristics and the effects of convective drying temperature on quality attrib0utes of watercress, without any pretreatment. Drying temperatures of 40, 55, and 70 8C resulted in drying times of 230, 119, and 92 min, respectively. The nutritional parameters were negatively correlated with the drying temperature. Retentions of 12.563.8272.864.2%, 51.163.3280.464.8%, and 44.366.1292.1612.2% were obtained for vitamin C, total phenolic compounds, and total antioxidant capacity, respectively. Increased values of TCD (total color difference) and BI (browning index), and higher chlorophylls losses (26.163.9255.6614.9%) were also observed as the drying temperature increased. In conclusion, although longer drying periods are required for lower drying temperatures, these are more profitable in terms of watercress nutritional features and overall quality to the consumer.

2018Journal article

Restricted access