Measurement Uncertainty Evaluation of the Aqueous Solutions of Gelatin’s Rheological Characteristics by Penetrometer

Gelatin, as a gelating component, influences on the structure of the finished product and, therefore on its parameters of the quality and the term of the shelf life. The main rheological characteristics of gelatin are the following: viscosity, gel strength, limit shear stress. Gelatin with the gel strength 220-240 Bloom is usually used at the development of the extruded marshmallow. The results of the researches of the limit shear stress of the 12 examples of the gelatin's solutions with the different values of the pH (in the range from pH=3 pH=8,5 with the step 0,5) are presented in the paper. Penetrometer “Labor” was used for the multiple measurements of the depth of penetration for each example of gelatin. The maximum strength of the structure was obtained at the researches of the example with the value pH5,0. The analysis of the measurement uncertainty of the shear stress (using one example of the gelatin with the value pH=3) was done. The shear stress, calculated by Rebinder's formula, is the result of the non-linearity indirect measurements. The components of the measurement uncertainty of the input quantities to the measurement uncertainty of the shear stress were analysed. The corresponding standard uncertainties type A and type B were calculated for each input quantities, using results of the multiple measurements and data, presented in the technical instruction of the penetrometer. The expanded uncertainty of the measurement of the shear stress for the example of the gelatin with the value pH=3 was calculated.