Abstract :
[en] The drying of pomegranate seeds was investigated
<br />at 40 °C, 50 °C and 60 °C with air velocity of 2 m/s.
<br />Prior to drying, seeds were osmodehydrated in 55 °Brix
<br />sucrose solution for 20 min at 50 °C. The drying kinetics
<br />and the effects of osmotic dehydration (OD) and air-drying
<br />temperature on antioxidant capacity, total phenolics, colour
<br />and texture were determined. Analysis of variance revealed
<br />that OD and air-drying temperature have a significant
<br />influence on the quality of seeds. Both anthocyanin and
<br />total phenolic contents decreased when air-drying temperature
<br />increased. The radical diphenylpicril-hydrazyl activity
<br />showed the lowest antioxidant activity at 60 °C. Both
<br />chromatic parameters (L*, C* and h°) and browning index
<br />were affected by drying temperatures, which contributed to
<br />the discolouring of seeds. The final product has 22%, 20%
<br />and 16% of moisture; 0.630, 0.478 and 0.414 of aw; 151,
<br />141 and 134 mg gallic acid equivalent/100 g fresh matter
<br />(FM) of total phenolics; 40, 24, 20 mg/100 g FM of
<br />anthocyanins and 46%, 39% and 31% of antioxidant
<br />activity, for drying temperatures of 40 °C, 50 °C and
<br />60 °C, respectively. In view of these results, the temperature
<br />of 40 °C is recommended as it has the lowest impact on
<br />the quality parameters of the seeds. Differential scanning
<br />calorimetry data provided complementary information on
<br />the mobility changes of water during drying. Glass
<br />transition temperature (Tg′) depends on moisture content
<br />and as consequence, on drying conditions. In fact, Tg′ of
<br />seeds dried at 60 °C (Tg′=−21 °C) was higher than those
<br />dried at 50 °C (Tg′=−28 °C) or 40 °C (Tg′=−31 °C) and
<br />osmodehydrated seeds (Tg′=−34 °C). During OD and
<br />drying process, the texture of seeds changed. The thickness
<br />of seeds shrank by 55% at 60 °C.
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