3.6 Microstructure
The microstructure of ice creams without stabilizer or containing two levels of
stabilizers before and after temperature cycling as seen by cryo-SEM is shown inFigs. 3 and 4. Smaller size of ice crystals after heat shock in samples containing BSG
compared to others was obvious in these images, which confirmed the results of
bright-field microscopy. Air cells were also smaller in ice cream containing BSG,
which may be due to either its high viscosity or its emulsification properties, as
discussed previously. Because the air cell dispersion is controlled by the ratio of
disruption and coalescence in the freezer barrel, a higher viscosity produces smaller
air cells. This smaller size has positive impacts on the stability of the foam and on the
perception of creaminess during consumption (Eisner et al. 2005). The air bubbles in
ice cream are usually partially coated with fat globules and the fat globules are coated
with a protein/emulsifier layer (Goff 1997). More fat globules could be seen in ice
creams stabilized by BSG, which is related to more air cells as well as the
emulsifying capacity of this hydrocolloid. Measurement of air bubble size
distribution or composition of the air interface could help in better understanding
of BSG function in ice cream.