梯度干燥温度对核桃感官品质的影响

Effect of the gradient temperature drying on sensory quality in fresh walnut

为了解梯度干燥温度对核桃干燥效率及感官品质影响,以一种薄麻壳核桃为试验材料,采用梯度温度干燥鲜核桃,分析比较核桃水分含量、色差、酸价(AV)、过氧化值(POV)、脂肪酸和氨基酸组成等的变化。结果表明:干燥温度对核桃水分含量影响较大,温度越高,水分散失速率越快;核桃内种皮和种仁色差、AV值、POV值与干燥温度呈现正相关,干燥温度越高,颜色越深,AV和POV值越大,但种仁颜色变化较小;不饱和脂肪酸受干燥温度影响显著,其中油酸、亚油酸、亚麻酸在干燥后会发生氧化,且随着温度的升高,油酸相对含量升高,亚油酸和亚麻酸相对含量降低,当温度达到73℃时,3种脂肪酸比例表现出截然相反的趋势。综合各指标考虑,初步认定核桃干燥的最佳温度应在43℃左右,另外经43℃干燥后,核桃中仅丙氨酸含量有所上升,其余氨基酸含量均呈现不同程度降低。

The main objective of this study is to analyze sensory quality in walnut by the gradient temperature drying. Different temperature was used to dry the ＂Thin hemp shell＂ walnut as raw material in this study. The changes of moisture content, color, acid value（AV）, peroxide value（POV）, fatty acids and amino acids were concerned. The results showed that the temperature had a significant effect on moisture content. The higher temperature caused a higher reduction of moisture content. The color of walnut kernel and pellicle, acid value（AV） and peroxide value（POV） had a positive correlation with the gradient temperature, but the color of walnut kernel had a slight change. The influence of temperature on unsaturated fatty acid was significant. When the drying temperature raised, the ratio of oleic acid increased, the ratio of linoleic acid and linolenic acid showed a significant decreased. Once the temperature reached 73 ℃, the ratio of three fatty acids showed a opposite trend. In conclusion, the drying temperature of 43 ℃ could effectively dry fresh walnut, meanwhile, the original color and main nutrients of walnut kernel were also maintained. After 43 ℃ drying, the content of amino acids all decreased except alanine.