Questions & Answers
from "On Ice Cream" featured in Dairy Foods magazine
and sourced from "On Ice Cream" technical short courses.

Shelf Life of Ice Cream:

Question: We would like to change our "sell by" date from 9 to 12 months. What implications does this have on product quality?

Answer: Quality degradation of packaged ice cream primarily involves body and texture, with the most common problem being the development of a coarse, icy texture. Control over the stability of body and texture begins with the freezing point of the mix composition. It includes water immobilization properties that involve stabilizer type and level, protein functionality and the amount and type of sweeteners. Processing control elements include dairy ingredient variables, pasteurization and homogenization conditions and mix aging, as well as a myriad of freezing factors like mix temperature, barrel residence time, exit temperature and condition of the scraper blades. There are also post-freezing variables that need to be monitored. These include the nature of the package, including any shrink-wrap application, the rate of hardening and the final hardened temperature, as well as the amount of post-hardening heat shock to which the product is exposed.

A sample of ice cream representing the most favorable combination of conditions could maintain excellent quality for a year or more. However, a sample from another batch representing undesirable processing elements, as well as possibly having suffered heat shock abuse during distribution might reach an unacceptable level of quality much sooner. Since there is no way to identify the conditions under which ice cream will be handled once it leaves the control of the manufacturer, it is not practical to predict the shelflife of any ice cream product.

Accelerated shelflife testing, which involves extremes of heat shock exposure under controlled conditions, is useful in evaluating shelflife, but only in a relative way and only if it is correlated with consumer acceptance data. Accelerated testing is useful in comparing behavior of one product to another or to a given control; however, it will not provide information about the specific shelflife of the product, given the uncertain nature of the conditions to which it will be exposed. A more practical approach can be based on the profile of consumer or customer complaints received, combined with the evaluation of products purchased at or near the sell by date. A low level of complaints involving body/texture deterioration, or other quality attributes in most aged products would support a decision to extend the sell by date. Ongoing monitoring to evaluate the effect of that extension is necessary.