Comparison of Dried Alpinia officinarum Hance Quality Dried at Different Heat Pump Temperatures
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Abstract:
The effects of different heat pump drying temperatures (45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃) on the color, active substances and volatile components of the Alpinia officinalis with a moisture content of 8±0.5% were analyzed through using sun-drying as the control approach. The results showed that the color of Alpinia officinalis dried at 50 ℃ was the closest to that of sun-dried Alpinia officinalis, with the △Ｅ as 2.16±0.2 and rehydration rate as 2.39±0.03 (the highest). The rehydration ratio decreased with an increase of the heat pump drying temperature; Drying at 50?C led to the highest contents of total phenols and flavonoids (19.33±0.21 mg/g and 8.44±0.19 mg/g, respectively). When the heat pump temperature exceeded 50 ℃, the contents of total phenols and flavonoids decreased with an increase of the heat pump temperature. The effect of heat pump drying temperature on the content of galangin was not significant. The content of galangin in the Alpinia officinarum dried at 50 ℃ was 6.29±0.07 mg/g, and this content in the Alpinia officinarum dried by heat pump was higher than by sun-dyring (5.54±0.1 mg/g). The Alpinia officinalis dried in the sun, at 45 ℃, at 50 ℃, at 55 ℃, at 60 ℃, and at 65 ℃, respectively, had 81, 69, 74, 78, 82 and 85, types of volatile substances, and 42, 39, 37, 32, 34 and 31 olefin substances. Drying at 45 °C led to the highest content of eucalyptol (37.41%), and the content of eucalyptol decreased with the increase of heat pump temperature. Based on the color, quality and flavor of the dried Alpinia officinalis, the optimum temperature for heat pump drying was 50 ℃. The results reported in this paper provide a theoretical basis for the control of drying conditions of Alpinia officinarum by heat pump.
