Evaluation of test conditions during the measurement of coffee stability of instant whole milk powder

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Coffee provides a harsh environment for the reconstitution of milk powder with undissolved powder being manifested as undesirable ‘floaters' or ‘sinkers’. A coffee test method was adapted to explore the behaviour of a range of industrial samples of coffee stable and coffee unstable instant whole milk powders, under varying pH, temperature and water hardness. The development and application of a simulation test suggests evidence of some stabilizing contribution by the coffee itself. High surface fat coverage, as determined by electron spectroscopy for chemical analysis, and high ionic calcium levels were associated with instances of poor coffee stability. The effects of the physicochemical characteristics of the powders on coffee stability appear to predominate when various measures were implemented, such as prior reconstitution of the powder before addition to coffee, increased agitation and use of surface active agents, which succeeded in reducing coffee sediment.