基于酒花水分含量变化研究变温干燥模式对酒花干燥效率的影响

Evaluation of Hop Drying Efficiency Based on Moisture Content Measurement with Different Variable-temperature Drying Modes

为了解决酒花干燥生产过程中干燥时间长、干燥不充分等问题,本研究以甘肃地区主产酒花品种‘拓璞1号’为研究对象,利用改造烘箱模拟车间单层高床烤池的烘干方式,研究了不同变温干燥模式对酒花水分含量及酒花层相对湿度的影响。实验筛选出了两种较优的变温干燥模式,即在酒花烘干过程中,温度设置由30℃上升到50℃(30~50℃)以及由30℃上升到60℃后下降到40℃(30~60~40℃),其在7 h内可分别使酒花整体水分下降54.48%及49.82%。分析车间干燥曲线,30~50℃模式下呈线性拟合(R2>0.95),30~60~40℃模式下呈Weibull分布函数(β<1),表明以上两种变温模式下的干燥类型分别为恒速干燥和降速干燥,进一步验证了30~50℃变温干燥模式下干燥效率更高。而30~60~40℃变温干燥的酒花具有更高的精油含量,约比30~50℃变温干燥下高43%。研究表明,酒花干燥应采用前期低温(30℃)、后期高温(50℃)的方式;为获得更多的精油含量,可适当降低酒花干燥后期的温度(40℃)。

In order to solve the problems of long drying time and low drying sufficiency, the drying experiment was examined to verify the drying efficiency at different variable-temperature modes using the hop variety ’Tuopu No.1’ obtained from Gansu Province A modified oven was taken as the baking media with a single-layer curing barn. The moisture content of the hop cones and the RH values of the hop layers at different drying temperatures were measured. Two optimal variable-temperature drying modes were selected, that was, in the drying process of hops, the temperature was set from 30 to 50 ℃(30~50 ℃) and from 30 to 60 ℃ and then down to 40 ℃(30~60~40 ℃). Baking with these two drying modes, the moisture content of hops could be reduced by 54.48% and 49.82% within 7 h, respectively. The drying efficiency was furtherly verified in the hop bakery of the workshop and the drying curves were analyzed. The linear models could give a good fit to the drying curves of the drying mode of 30~50 ℃(R2>0.96), while Weibull distribution models(β<1)fitted well to the drying mode of 30~60~40 ℃. It was proved that the two drying models belong to constant rate drying and falling rate drying, respectively. It was further verified that the drying efficiency was higher under the drying mode of 30~50 ℃. Hops drying at 30~60~40 ℃ had higher essential oil content, which was about 43% higher than that at 30~50 ℃.The above results indicated that the hops should be dried with a low temperature(30 ℃) in early stage and followed a high temperature(50 ℃) in late stage;In order to obtain more essential oil content in the final hops, the drying temperature could be reduced to some extent(40 ℃).