Advanced control of microstructure in ice cream by agitation and mixing during freezing process

Abstract

Agitation and mixing play an important role in ensuring the appropriate dispersion of ice crystals, bubbles, and fat globules during the freezing process in ice cream manufacturing. The dispersion determines the internal structure of ice creams and hence, the ice cream quality. To achieve advanced control of the internal structure of ice creams, in this study, the effect of agitation on air entrainment, micronisation of air bubbles, and fat globule agglomeration was investigated using a batch-type freezer with an anchor impeller. Besides, rheological properties of an ice cream sample that was stored in the refrigerator for 24 h after freezing were analysed. In addition to steady agitation, unsteady agitation with a periodical change in the rotation direction was employed. Temperature measurement and flow observation suggested more effective scraping of frozen phase from the cooling surface for unsteady agitation than for steady agitation. Furthermore, air entrainment and fat globule agglomeration during freezing were promoted under unsteady agitation. Consequently, the sample manufactured under unsteady agitation exhibited enhanced thermal robustness compared to that manufactured under steady agitation. Thus, unsteady agitation can be an effective strategy to control the formation of microstructures in ice cream.