What is Stability?

This manuscript is concerned with test methods used for grading HM-pectin for use in acidified milk drinks (AMD). Unlike some other food ingredients, pectin has a long tradition for being standardised for batch-to-batch consistency by the use of grading strength methods. These quantify the dosage necessary for accomplishing a given magnitude of the desired effect. By default this involves for each tested sample a dosage-response curve with some metric for the desired effect as the dependent parameter. Dosage-response curves for an HM-pectin used with two prototypical AMD with 3 % MSNF and 8.5 % MSNF content are presented. The traditional metric for stability, sediment after centrifugation, is compared to - as alternative metrics - particle size and viscosity. Further, the adsorption of pectin to milk protein is measured, and the effect of heat treating the AMD is reported.Besides their direct practical use, the results provide information about the mechanism by which the stabilisation works. The mechanism resembles what university textbooks name “steric stabilisation”, but the lack of stability for low dosages seems not to be explicable by the related concept of bridging flocculation. In addition it was found that stabilisation of the 3 % MSNF AMD was only possible with smaller particle size than with the 8.5 % MSNF AMD, and the former thus required almost the same pectin dosage as the latter.