Reducing atmosphere drying as a novel drying technique for preserving the sensorial and nutritional notes of foods

Reducing atmosphere drying (RAD) was assayed as a novel technique for preserving the color and the nutritional fresh notes of apricot. A freeze, hot air and vacuum drying techniques were applied for a comparison purpose. The results showed that the apricot samples dried by both RADMIX and RADNITROGEN preserved better the fresh color notes while the freeze-drying was characterized by light and dully notes compared to a fresh sample. The total phenolic content significantly differed between fresh, RADMIX, RADAIR, hot air and vacuum with the highest value observed for both vacuum and hot air with 284.8 and 259.5 mg GAE 100 g-1 dm, respectively. DPPH inhibition activity was significantly similar for both fresh (or freeze drying) and each RADMIX, hot air and vacuum dried samples with 83.52, 76.3, 70.31, 67.86%, respectively, with the highest value attributed to RADMIX sample. The RAD-type dried samples (RADMIX, RADNITROGEN, RADAIR) possessed ABTS scavenging activity range of 68.74, 64.49 and 61.61 μmol TE g-1 dm respectively, which were close to that of the fresh sample (63.36 μmol TE g-1 dm) with the highest value attributed to RADMIX sample. The total flavonoid content was significantly similar between fresh (or freeze drying), vacuum, hot air and RADMIX samples with a range of 27.38, 24.25, 19.41 and 18.81 mg QE 100 g-1 dm, respectively, which exhibited an advantageous role of hydrogen in RADMIX system over both RADNITROGEN and RADAIR. For the first time, a technique based on the use of hydrogen in the drying atmosphere of a closed system was successfully proved for drying foods. This novel technique exhibits an opportunity for the food drying processors to produce dried foodstuffs with fresh color and nutritional notes.