基于电学参数的鲜切苹果品质检测

Quality detection of fresh-cut apple on electrical properties

对鲜切苹果块,经10.0 g/L的抗坏血酸溶液保鲜处理,在常温放置96 h的过程中测定了其7项理化指标和4个电学参数的变化情况。结果如下:在常温放置96 h过程中,鲜切苹果块硬度、可滴定酸、可溶性固形物、含水率和质量密度分别下降36.37%、32.58%、24.07%、14.24%和6.34%,褐变度增大2.23倍,固酸比在12~72 h期间呈增大趋势。随放置时间增加,苹果相对介电常数和胞外电阻率下降,胞内电阻率和介质损耗因数呈波浪式变化。对理化品质指标与电学参数间的差异显著性分析发现,相对介电常数、胞外电阻率与硬度、可滴定酸、可溶性固形物、褐变度、含水率、质量密度间显著相关(p≤0.05),介质损耗因数、胞内电阻率与7项理化指标均不相关。据此,建立以相对介电常数和胞外电阻率为自变量,6个生理指标为因变量的线性方程,决定系数R2>0.8。建立的鲜切苹果电学参数和理化指标间的关系,可用于快速检测其放置过程中的品质变化。

The change of seven physicochemical indices and four electrical parameters of fresh-cut apples treated by ascorbic acid solution of 10.0 g/L were measured during room temperature placed 96 h.The experimental results were as follows： during placing of fresh-cut apples,firmness,titratable acidity,soluble solid,moisture content and density decreased by 36.37%,32.58%,24.07%,14.24% and 6.34%,respectively,and brown color increased by 2.23 times,and the ratio of total soluble solid and titratable acidity showed an increase trend in 12 ~ 72 h. With the increase of placing time,relative permittivity and extracellular resistivity decreased,and intracellular resistivity and loss factor showed wave change. The significance analysis of difference between physicochemical indices and electrical parameters showed that there were significant correlations between relative permittivity,extracellular resistivity and firmness,titratable acidity,soluble solid,brown color,moisture content,density,and were significant correlated between loss factor（ p ≤ 0.05）,intracellular resistivity and seven physicochemical indices.According above result,the linear equations were built with relative dielectric constant and extracellular resistivity as independent variables and six physicochemical indices as dependent variable,and the determination coefficient was over 0.8. It can be used to fast evaluate quality change during placing of fresh-cut apples by the relations between physicochemical indices and electrical parameters.