Improved Tribological Characterization of Acidified Milk Products by Means of a New Rubber Material

Acidified dairy products such as yogurt or quark have been popular for a long time because of their typical creaminess. However, determining creaminess is difficult. Various approaches to measuring creaminess have already been developed, often taking the coefficient of friction into account. Therefore, the aim of this work was to establish a commercially available rubber surface for a tribological method to improve the differentiation of samples with different contents of fat and protein. This improved differentiation should in turn help to gain more information about the creaminess of acidified milk products. Rubber surfaces including natural rubber, styrene-butadiene and nitrile-butadiene as single compounds as well as mixtures of two rubbers (natural rubber/styrene-butadiene and nitrile-butadiene/styrene-butadiene) were screened. An acidified milk matrix with 0% and 3.5% fat was chosen as sample set for the screening. Using the rubber P9540 (mixture of styrene-butadiene and nitrile-butdadiene), the differentiation was improved for 34–58% compared to the widely used SBR 70 (depending on the chosen sliding speed). Afterwards, the application of the rubber was tested using a sample set of acidified milk matrices with fat contents ranging from 0 to 10% and a sample set of commercial products with protein contents from 4 to 11%. The new rubber mixture is suited for differentiating fermented milk matrices with a fat content of 0% and 3.5% and above. Additionally, commercial samples like Skyr with a protein content of 11% can be distinguished from samples with a lower protein content. [Display omitted] •Rough and wavy rubbers are needed to differentiate acidified milk samples with different fat content.•Equal polarity of rubber and sample supports the increase of the differentiation ability.•Samples with different protein content can be distinguished at higher sliding speeds.