Parmigiano Reggiano and Grana Padano cheese curd grains size and distribution by image analysis

Grain sizes (projected area and radius ratio) of 93 Parmigiano Reggiano and Grana Padano cheese curds from four dairies produced using different cutting procedures were measured by bi-dimensional image analysis. Curds were sampled at the end of cutting (fresh curd grains, FCG) and cooking (cooked curd grains, CCG). Mean and median areas of FCG particles were 2.72 and 1.53 mm2, respectively. Curd grain shrinkage due to cooking to 54.6 °C ± 0.8 reduced the mean and median area values to 1.63 and 1.09 mm2, respectively, with a mean area reduction ratio of 1.76 ± 0.43. Size distribution of the particles was not symmetric and the span value of the distribution of area values of FCG and CCG ranged from 2.6 to 5.8 and from 1.6 to 4.0, respectively. The measuring of cheese curd grains' size and distribution with a simple method can become a key element to increase the uniformity of curd grains' size, improving the coagulum cutting operation.

► Curd grain's size contributes to determine cheese moisture content and distribution. ► Size and distribution up to date were measured with multi-stack sieving methods. ► An image analysis method was applied to 93 Italian hard cooked cheese curds. ► Grain size variability among dairies and within each dairy was discussed. ► Curd grains size and distribution were compared to those of other cheeses.