Analysis of Frozen Desserts Using Low-Temperature Scanning Electron Microscopy (LT-SEM)

Commercial vanilla ice cream and other frozen desserts from the United States were analyzed for ice crystal length using low-temperature scanning electron microscopy (LT-SEM). Average ice crystal length was determined using multiple micrographs of each sample/product. Out of the products tested, 11 out of 15 samples had an average ice crystal length above the consumer sensory threshold limit of 55 µm. Products containing stabilizers tended to have smaller average ice crystal lengths than products without stabilizers. With a few exceptions, lower fat products tended to have larger ice crystals because there was less fat to stabilize the ice crystals. Four brands of frozen dessert were studied in detail: a super-premium ice cream (Brand P), a regular ice cream (Brand R), a dietary high protein ice cream (Brand D), and a non-dairy coconut-based frozen dessert (Brand ND). All brands were purchased from two separate supermarket supply chains (Store I and Store P) and analyzed for ice crystal size, weight loss/shrinkage, melting rate, texture, and sensory characteristics before and after being heat-shocked (HS). Brand P, R, and ND all had mean ice crystal sizes that were not significantly different when purchased from either Store I and Store P. The mean ice crystal size increased after HS for all brands except Brand ND. Brand D and Brand P had the highest melting rates, while Brand ND had a much lower melting rate than the other brands tested. Brand ND had a slight decrease in the average ice crystal size and had a decrease in peak force/hardness after HS, while all other brands had an increase in average ice crystal size and an increase in peak force/hardness after HS. Significance was determined using α = 0.05 for all sensory data. The iciness attribute was found to be significantly affected by both brand and HS and an increase in ice crystal size corresponded with an increase in iciness for most samples. The use of stabilizers and emulsifiers in the brands affected various melting characteristics. Additional research is needed on non-dairy frozen desserts and how their physical and sensorial properties are affected by heat-shock