Directions for teachers: Ask students to read the online Science News article “Grainy ice cream is unpleasant. Plant-based nanocrystals might help,” and answer the following questions. A version of the article, “Cellulose helps ice cream go down smooth,” appears in the May 7, 2022 & May 21, 2022 issue of Science News.
1. Why does ice cream sometimes develop a grainy texture?
Ice cream becomes grainy when ice crystals in the mixture grow to a diameter of 50 micrometers or more. The crystals grow as they melt and reform over time due to natural temperature fluctuations.
2. How do ice cream manufacturers currently keep ice cream from getting grainy? How well does this solution work?
Food stabilizers such as guar gum are added to ice cream. These gum stabilizers slow the ice crystals’ growth, but do not stop it. Ice cream with gum stabilizers will eventually become grainy, but not as quickly as ice cream without stabilizers.
3. What new potential solution are scientists investigating?
Scientists are investigating cellulose nanocrystals, or CNCs, as an additive. CNCs are derived from wood pulp and have properties similar to guar gum.
4. In your own words, describe food scientist Tao Wu and colleagues’ experimental setup. What did they use as a substitute for ice cream in their study, and what were the components of each test solution?
The team used a sucrose solution as a substitute for ice cream. They compared crystal growth in sucrose solution with CNCs added and sucrose solution with guar gum added.
5. What did the experiments reveal?
In the sucrose solution with CNCs added, ice crystals stopped growing after 24 hours and after one week, remained at a diameter of 25 micrometers. In sucrose solution with guar gum, ice crystals grew to 50 micrometers in three days.
6. What does food engineer Richard Hartel say about the findings? Why do you think the author of the Science News article included Hartel’s perspective in the story?
Hartel says the findings suggest that the CNCs are more effective than gum stabilizers. The author may have included Hartel’s perspective because he is an expert in the field who was not involved in the research, so his analysis of the work is likely to be unbiased.
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