Many industry professionals associate dairy drinks with the refrigerated dairy case. But of the more than 5,500 dairy drinks introduced worldwide, over half were designed for ambient storage, according to Innova Market Insights. In addition, virtually all of the clinical nutrition beverages and the sports and energy drinks (which use generous amounts of dairy ingredients) are formulated for ambient conditions.

To achieve shelf stability, these ready-to-drink (RTD) beverages will be subjected to a heat process, which will put dairy proteins to the test.

Heat-stable dairy ingredients

Heat treatment can vary from hot fill with relatively mild conditions to retort with temperatures of 239 F to 253 F for 12 to 20 minutes.

“Heat stability of milk refers to the ability of milk proteins to withstand severe heat treatment before destabilization of milk proteins occurs leading to coagulation, gelation, phase separation, turbidity, sedimentation or precipitation.  It is an important property of milk proteins which determines their applications in many products including beverages, infant formula, evaporated milk, soup, sauces and many other products, particularly ones which involve retort or UHT sterilization,” noted Hasmukh Patel, assistant professor, South Dakota State University, Brookings, S.D.

Researchers and industry are using a variety of newer processes and techniques to improve the heat stability of dairy ingredients. These technologies include pre-heat treatment of nonfat dry milk, hydrolyzing whey protein, ultrasonication and glycosylation. A recent technical report on heat stability explains these processes in detail. (See “Whey Protein Heat Stability” in the Sources box.)

Not all dairy proteins have the same innate heat stability.

“The important thing to understand when working with dairy proteins is that the heat stability of caseins and whey proteins are very different,” said Kimberly (K.J.) Burrington, dairy ingredient applications coordinator with the Wisconsin Center for Dairy Research, Madison, Wis. “Caseins are considered very heat-stable, while whey proteins are not. It is also important to remember that the pH of the system you are using will also have a great effect on the protein, because proteins are charged molecules and their charge will change with pH, and it will also change how they interact with each other during heat processing.”

Also, whey proteins derived directly from milk via filtration have greater solubility than do whey proteins derived from cheese making. (See “Milk Fractionation Technology and Emerging Milk Protein Opportunities” in the Sources box.)

Heat stability of milk protein is a complex subject, Patel said. To understand and improve the heat stability of milk proteins, research is underway at South Dakota State University with an aim to develop heat-stable dairy ingredients by understanding and manipulation of protein interactions through mineral manipulation of milk proteins using CO₂ treatment, enzymatic cross-linking of milk proteins and using food grade additives as processing aids, he said.

Formulation tricks

Manufacturers continue to develop products with higher levels of protein, such as the FitPro Plus drink which touts 40 grams of real milk protein in a 500-milliliter aseptic carton displaying the REAL seal.

An Innova database survey of shelf-stable beverages introduced around the world with the claim “high source of protein” shows that whey protein is the ingredient of choice, followed by milk (which may be ultrafiltered to concentrate protein) and milk proteins. The survey also showed that carageenan, cellulose gum and xanthan gum are used most often as stabilizers in these RTD beverages. Further formulas and tips are included in an application monograph on RTD beverages. (See “U.S. Whey Proteins in Ready-To-Drink Beverages” in the Source box.)

“Proper wetting of dairy ingredients, gums and stabilizers can accelerate hydration, resulting in time and cost savings, as well as improved heat stability of the finished beverage,” said Ron Bentley, vice president, Semi-Bulk Systems Inc., St. Louis.

RTD beverage resources

A large number of dairy ingredient suppliers sell domestic dairy proteins with improved heat stability, including Davisco Foods, Glanbia Nutritionals, Hilmar Ingredients, Lactalis Ingredients USA, Leprino Foods and Milk Specialties Global. Additional suppliers may provide some ingredients with enhanced heat stability upon request, including Darigold and Saputo.

Visit USDEC.org for an RTD application monograph and supplier contact information through the “Find a U.S. Supplier” search tool.   

Sources

• Burrington, K.J. “Technical Report: Whey Protein Heat Stability”  http://bit.ly/1clImgC
• Burrington, K.J. “Technical Report: Milk Fractionation Technology and Emerging Milk Protein Opportunities”  http://bit.ly/1clImgC
• Rittmanic, Steve. “U.S. Whey Proteins in Ready-To-Drink Beverages” http://bit.ly/18lTVzW