FACTORS INFLUENCING THE ICE RECRYSTALLIZATION INHIBITION EFFECTS OF CELLULOSE NANOCRYSTALS IN MODEL ICE CREAM
In ice cream, ice recrystallization results in the formation of large ice crystals, leading to an icy texture and decreasing consumer’s appeal. Currently, food polysaccharides are used as stabilizers to inhibit ice recrystallization. However, their ice recrystallization inhibition (IRI) effects depend on measurement conditions and opposing results have been reported in literature. In this work, cellulose nanocrystals (CNCs), newly identified IRI inhibitors, are used to understand the influences of measurement conditions on the IRI effect of stabilizers in a model ice cream system.
The first part of this research discussed the influence of sucrose concentrations. The IRI effect of CNCs was higher at low sucrose concentrations, almost disappeared at medium sucrose concentrations, and restored slightly at high sucrose concentrations. The IRI effect was correlated with the coverage of CNCs on the ice surface. The second part studied the influence of storage time. CNCs were IRI inactive within 2 hours but completely stopped the growth of ice crystals after 24 hours. Ice shaping was also observed for CNCs after a long incubation time. The time-dependent IRI activity and ice-shaping behavior were explained by the increased surface coverage of CNCs on ice crystals over time. The third part investigated the influence of stabilizer concentrations and proposed that depletion interaction might be responsible for the reduced IRI effect of CNCs at high concentrations. The fourth part examined the influence of storage temperature. The forms of recrystallization, diffusion rate and surface coverage could explain the temperature-dependent IRI effect of CNCs. The fifth part explored the IRI effect of CNCs in the presence of polymers. With increasing polymer concentrations, anionic polymers first improved and then reduced the IRI effect of CNCs. Further increase of polymer concentration accelerated the ice recrystallization. Neutral polymers had little influence on the IRI effect of CNCs. As a result of polymer addition, the increased effective concentration of CNCs enhanced IRI effect, and depletion interaction reduced IRI effect and accelerated recrystallization.
This work advanced our fundamental understanding of the IRI activity of stabilizers from colloidal science aspect, which is important for screening new IRI materials and manufacturing frozen foods.