A study of fat and air structures in ice cream

Three ice cream mixes of conventional composition with varying emulsifier content (no emulsifier; 0.15% mono- and di-glycerides; 0.15% mono- and di-glycerides plus 0.06% polysorbate 80) were frozen using three different freezing regimes (continuous freezer at low and high back pressure and batch freezer) in order to prepare a series of ice cream samples with varying levels of fat destabilization and foam structures. The hardened samples were viewed by thin-section transmission electron microscopy after freeze-substitution and low-temperature embedding. The images were compared to those obtained by low-temperature scanning electron microscopy. The structures created by increasing levels of fat destabilization were observed as an increasing concentration of discrete fat globules at the air interface and increasing coalescence and clustering of fat globules both at the air interface and within the serum phase. However, air interfaces at the highest levels of fat destabilization were not completely covered by fat globules, nor was there evidence of a surface layer of free fat. Air interfaces from continuous and batch freezing were similar. (C) 2000 Elsevier Science Ltd. AU rights reserved.