Effect of Hot Air Drying and Hot Air-pulsed Sudden Decompression Flash Drying on the Color and Quality of Strawberries
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Abstract:
To study changes in strawberry quality after drying by hot air drying (HAD) or hot air-pulsed sudden decompression flash drying (HA-PSDFD), the effects of drying temperature, vacuum drying temperature, and pre-drying water content on drying characteristics, color, and physical and chemical qualities of dry strawberry products were studied. Uniform design tests and drying technologies were analyzed and evaluated using analytic hierarchy processes. The results showed that the optimum HA-PSDFD drying conditions were a pre-drying water content of 60%, flashing temperature of 90 ℃, dead time of 15 min, pressure difference of 0.10 MPa, vacuum drying temperature of 70 ℃ (60 min) -60 ℃ (40 min), and a total drying time of 255 min. Drying temperature had a more significant impact on strawberry drying rate during HAD. The optimum HAD drying process was a drying temperature of 70 ℃ for 360 min. Comparing these two optimal process conditions, the quality of strawberry products dried by HA-PSDFD was superior to the quality of products dried by HAD, resulting in a lower hardness value (2323.65 N) and a higher Vc content (339.38?10-2 mg/g DW). In addition, pelargonidin-3-glucoside and cyanidin-3-glucoside contents after HA-PSDFD were 2.5 and 2.2 higher than those by HAD, respectively. Moreover, drying time was reduced and the color of the product was superior, upon HA-PSDFD treatment, with a hue value of 24.66.
