A recent Purdue study has deciphered why food ingredient blends are more sensitive to changes in climate than single ingredients. Featuring on the cover of the May edition of the Journal of Food Science Understanding, the study shows how food ingredients interact differently when blended and can help those in the industry consider best practices to handle or package their product for a longer shelf life.

“Blending crystalline ingredients such as salt and sugar with amorphous solids (without uniform shape), such as proteins, starch-based ingredients and gums, destabilizes the ingredients when heated or exposed to increasing humidity,” says Lisa Mauer, Professor of Food Science who led the research at Purdue University. “This can be frustrating to food formulators and consumers alike.”

Speaking to FoodIngredientsFirst, Mauer says: “While formulation and handling practices are in place to optimize the quality and shelf-life of powder blends, particularly when the packaged products are stored at ambient temperatures, there is less documentation available on the effects environments (temperature and humidity) have on the potential phase changes of the ingredients when they are blended together.”

She adds: “For particularly sensitive ingredient blends, two important parameters could be documented: 1) identifying how the water activities of the amorphous ingredients change as temperature increases, particularly if there are different starting moisture contents in these ingredients, and 2) identifying how the deliquescence points of the crystalline ingredients change as temperature increases."

“If the moisture content of an amorphous ingredient can be reduced before it is added to a formulation such that its water activity will never exceed the crossover temperature with the deliquescence points of co-formulated crystalline ingredients in expected environments throughout food distribution, then the packaged product quality and shelf-life should be better,” Mauer explains.

How should the industry respond to these concerns? “There are numerous examples ingredient blends that are less stable than their component individual ingredients. To minimize ingredient blend instability, careful selecion of formulations and packaging as well as establishment of quality control parameters including amorphous ingredient moisture contents documented to avoid the crossover point with deliquescence are recommended,” Mauer notes.

The study builds on Mauer’s previous research on the deliquescence behavior of crystalline ingredients which identified the humidities at which crystalline ingredients begin to dissolve (the underlying reason behind salt, sugar, and lemonade mixes clumping). To prevent deliquescence, the humidity must be kept lower than the deliquescence thresholds.

But this becomes more difficult when amorphous ingredients are added. “Picture amorphous ingredients as little sponges,” Mauer says. “These sponges absorb water from the environment and their texture changes.”

Consumers find examples of this when a bag of chips is left open. As the chips absorb humidity, their texture becomes rubbery and stale. Similarly, cotton candy quickly becomes sticky on a warm summer day. The food industry uses the term “water activity” to describe the mobility of water in these foods, which gets higher as more water is absorbed or as the temperature increases.

The study is the first to identify the crossover point between the crystalline ingredient deliquescence point and the amorphous ingredient water activity. Above the crossover point, crystalline ingredients dissolved in a closed system.

The study focused on blends of particulates that can be found in instant beverage mixes, seasoning blends, cake mixes, vitamin preblend mixes and powders used to flavor snack foods.

When food products move through distribution or home from grocery stores in the consumer’s trunk on a hot day, variant climates can affect the food before it ever gets to the pantry.

“While the moisture sorption-related problems can be solved by packaging ingredient blends in individual serving sizes, this approach increases costs and the environmental burden associated with packaging does not solve the enhanced temperature sensitivity of the ingredient blends,” Mauer says.

The research identified the moisture sorption properties of the ingredients, how the deliquescence points of the crystalline ingredients and the water activities of the amorphous ingredients are affected by temperature, how the ingredient blends respond to environments over time, and documented the physical state and thermal properties of ingredients and blends using advanced analytical techniques such as powder X-ray diffraction and differential scanning calorimetry which provides vital information to food formulators and industries seeking solutions to deliver the best product to the consumer.

by Robin Wyers