Abstract
Ice cream is a complex multi-phase structure and its perceived quality is closely related to the small size of ice crystals in the product. Understanding the quantitative coarsening behaviour of ice crystals will help manufacturers optimise ice cream formulations and processing. Using synchrotron X-ray tomography, we measured the time-dependent coarsening (Ostwald ripening) of ice crystals in ice cream during cooling at 0.05 °C/min. The results show ice crystal coarsening is highly temperature dependent, being rapid from ca. −6 to −12 °C but significantly slower at lower temperatures. We developed a numerical model, based on established coarsening theory, to calculate the relationship between crystal diameter, cooling rate and the weight fraction of sucrose in solution. The ice crystal diameters predicted by the model are found to agree well with the measured values if matrix diffusion is assumed to be slowed by a factor of 1.2 due to the presence of stabilizers or high molecular weight sugars in the ice cream formulation.
Highlights
Ice cream is a popular diary product whose microstructure is one of the critical factors that determines its sensorial perception
We aim to provide only a the Ostwald ripening of ice crystals in an aqueous solution of sugars [24]
The term h·K is proportional to g(φ)·h(φ)·ξ(T) where h is given by Equation (7), K is given by Equation (3) and the temperature dependent ice volume fraction, φ, is calculated as set out in
Summary
Ice cream is a popular diary product whose microstructure is one of the critical factors that determines its sensorial perception. The control of the crystal size is widely recognized as a critical factor in the development of a smooth and creamy texture desired by consumers; large ice crystals will be perceived as being grainy and coarse [1]. It is of great interest for the food scientist to develop a predictive description of physical mechanisms that govern the kinetics of the coarsening in order to inhibit a deterioration in the quality of ice cream. The manufacture of Crystals 2019, 9, 321; doi:10.3390/cryst9060321 www.mdpi.com/journal/crystals
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