Depletion interaction may reduce ice recrystallization inhibition activity of cellulose nanocrystals (CNCs) at high concentrations

In ice cream, food hydrocolloids are commonly used as stabilizers for controlling ice recrystallization. Recent studies suggest that some stabilizers might bind to ice crystal surfaces and inhibit recrystallization. However, this ice-binding mechanism is challenged by the fact that stabilizers at high concentrations sometimes have reduced activity or even accelerate ice recrystallization. In this work, we determined the ice recrystallization inhibition (IRI) activity of cellulose nanocrystals (CNCs) at different concentrations in the 3.0% sucrose solution by the splat assay and in the 25.0% and 40.0% sucrose solutions by the sandwich assay. Reduced activity at high CNCs concentrations was observed in the sandwich assay. It was not linked to the phase separation or liquid crystal phase formation of CNCs but was caused by the accretion of nearby ice crystals and the forming of large ice crystals with irregular morphology and high aspect ratios. A new explanation based on the depletion-interaction -induced accretion of ice crystals was proposed. Our findings might resolve the contradiction between the ice -binding mechanism and the stabilizer concentration effect and add more support to the interfacial mechanism of ice recrystallization inhibition. They also pointed out the importance of selecting suitable stabilizer concen-trations for screening IRI active materials and manufacturing frozen desserts.