Hadimani Lingaraj, Mittal Neerja
1Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002 India.
Present Address: Department of Computational Instrumentation, CSIR-Central Scientific Instruments Organisation, Chandigarh, 160030 India.
J Food Sci Technol. 2019 Apr;56(4):2305-2311. doi: 10.1007/s13197-019-03641-9. Epub 2019 Feb 13.
Maturity of a citrus fruit is generally expressed by a numerical value called citrus colour index (CCI). The success of methods employed in estimating the maturity depends on the cultivar and climatic conditions of growing regions. In this work, an image processing based method using CIELAB color model has been developed to estimate the CCI of Kinnow mandarin fruits. A polynomial transformation based camera characterization method was employed to reduce the number of transformations required for RGB to colour space transformation, which resulted into a colour difference of 2.191 with CIELAB 2000 colour difference formula. In order to analyse the performance of this method, linear regression and partial least square (PLS) models were built on a dataset of 271 Kinnow fruit images wherein spectrophotometer was used for the validation of computed CCI values. The proposed method achieved a high adjusted value of 0.9660 using PLS regression, which ascertain the feasibility of image processing based system in estimating the maturity of Kinnow fruits. Additionally, a correlation analysis between colour coordinates and physicochemical properties was conducted to analyze the relation between the fruit's external peel colour and its internal characteristics.
柑橘类水果的成熟度通常用一个称为柑橘颜色指数（CCI）的数值来表示。用于估算成熟度的方法是否成功取决于种植地区的品种和气候条件。在这项工作中，开发了一种基于图像处理的方法，使用CIELAB颜色模型来估算金诺橘的CCI。采用基于多项式变换的相机表征方法，将RGB到颜色空间变换所需的变换次数减少，使用CIELAB 2000色差公式时，色差为2.191。为了分析该方法的性能，在271张金诺橘果实图像的数据集上建立了线性回归和偏最小二乘（PLS）模型，其中使用分光光度计对计算出的CCI值进行验证。所提出的方法使用PLS回归获得了0.9660的高调整值，这确定了基于图像处理的系统在估算金诺橘果实成熟度方面的可行性。此外，还进行了颜色坐标与理化性质之间的相关性分析，以分析果实外皮颜色与其内部特征之间的关系。
