Influence of different drying methods on physico-chemical properties of raspberries
2016
Vakula, Anita | Đurica, Milan | Šumić, Zdravko | Tepić-Horecki, Aleksandra | Vidović, Senka | Pavlić, Branimir
Fresh raspberries (Rubus idaeus) were dried by convective drying with heat pumps, vacuum drying and freeze drying (lyophilization) in order to compare quality of samples dried by different drying techniques. Physico-chemical properties of dried raspberries were investigated in all applied techniques. Moisture content, water activity, shear force, rehydration power, total phenols content, total flavonoids content and antioxidant activity were used as the most suitable quality indicators. The lowest loss of phenolic compounds and the highest antioxidant capacity were observed in sample dried by freeze drying (-30 °C, 10-3 kPa and 72 h), where was also noticed: the lowest moisture content and aw value and the highest rehydration power. In vacuum dried samples (45 °C, 2 kPa, 14 h and 60 °C, 2 kPa, 10 h) was observed lowest shear force and the highest flavonoids content, respectively. Samples dried with convective drying with heat pumps showed less good results of all physico-chemical properties compared to vacuum and freeze dried samples.
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