An analysis of the correlations between the hardness index and selected physicochemical properties of wheat grain

Abstract

The processes of grain grinding and milling are affected by the physical properties of kernels, whereas energy consumption during these processes is influenced mainly by their mechanical properties. Therefore, the main aim of this study was to determine the relationships between selected physicochemical properties of wheat grain classified into different hardness groups. Technological (processing), mechanical and geometric properties of grain were evaluated in 12 wheat cultivars produced in Poland. The cultivars were divided into four grain hardness groups. The results were analyzed using the following statistical modules: descriptive statistics, one-way analysis of variance (ANOVA), correlation analysis, and regression analysis. Kernels of various hardness were found in each of the evaluated wheat cultivars, in particular those classified as medium soft and medium hard. The type and strength of correlations between the analyzed properties of grain were considerably affected by kernel hardness. The greatest differences were observed in comparisons of the following pairs of kernel parameters: length and width, length and relative strain, length and rupture force, and rupture force and relative strain. On average, the strongest correlations were noted between rupture force and rupture energy, and between kernel thickness and mass, whereas the weakest correlation was found between kernel mass and relative strain. The study demonstrated that the mechanical properties of wheat grain were not affected by crude protein content or total ash content. Grain hardness was correlated with kernel length, vitreousness, rupture force, and rupture energy. The hardness index (HI) increased by 110% within the range of average kernel length values (from approx. 5.4 mm to approx. 8.0 mm). The increase in HI values was accompanied by an increase in rupture force (by approx. 90%) and rupture energy (by approx.115%).