Lactose Crystallization in Ice-Cream with Alternative Sugars and Sugar Substitutes

Grittiness and mealiness are the most common defects of ice-cream structure. As a rule, they are caused by lactose crystallization and recrystallization. In ice-cream, lactose is an oversaturated solution, and its potential crystallization should be considered when replacing sugar with alternatives and substitutes. In this case, crystallization is likely to occur at –10 °C. The article describes the effect of sucrose, fructose, trehalose, glucose, and their compositions with other substitutes on lactose crystals in ice-cream. The methods of light microscopy, dynamic viscosity, and rheology made it possible to study lactose crystals in dynamics. In cross-section, a lactose crystal was an uneven rhombus in the presence of alternative sugars and a trapezoid at ≤5 % sugar content. In the concentrated model solutions of sucrose and a fructose+trehalose, lactose crystals were 4–12 μm smaller after 1 month of storage than in the samples with substitutes. Smaller crystals developed in the samples with fructose+trehalose+maltodextrin and with sucrose+maltitol+maltodextrin. The smallest crystals were observed in the sample with sucrose-maltitol+maltodextrin (≤ 5 μm) while the largest crystals (≤ 18 μm) developed in the sample without additional sugars. In the frozen whipped samples without stabilizers, the average lactose crystals grew as big as 71 μm after 3 months of storage with maltodextrin and 74 μm in the samples with sucrose+maltitol+maltodextrin. The smallest crystal size (41 μm) was found in the sample with 14 % fructose and trehalose. When sucrose was replaced with date-syrup fructose, glucose, or inulin, they triggered lactose crystallization, despite a major increase in viscosity (2.6 times). Sugars (sucrose and fructose+trehalose) in standard amounts inhibited lactose crystallization. When designing new ice-cream formulations, food engineers should keep it in mind that alternative natural sugars, e.g., date syrup, and other sucrose substitutes contain nutrients that may initiate lactose crystallization.