Protein in Ready-to-Drink (RTD) Beverages: Protein and Heat

A variety of ingredients can be added to an RTD to improve its nutritional profile; but nothing has been as popular as protein. Paired with the popularity of rich, indulgent flavors; neutral pH, shelf-stable RTDs fortified with protein have become a popular product option for both nutrition and snack brands.

The question is, what happens to protein, particularly dairy protein (one of the most popular ingredients to fortify with) when you heat it to 140°C?  And then what happens when you leave it on a shelf for a year?  If you mix up a protein shake and leave it for even just half an hour the taste and texture are going to be different than if you drink it right away; and usually, it’s not for the better.  What exactly is happening when protein and heat cross paths?

How does a protein’s shape impact solubility in RTDs?

When looking at protein in its natural shape, there are a variety of ways to describe it. Whether it’s whey protein, casein, or pea protein, they are all made up of 20 different amino acids linked together in a variety of ways to create unique turns, folds, and shapes. The shape of the protein determines a lot about how it works.

For example, a whey protein, is very long and folded in on itself with a lot of bonds holding it together and is considered a fibrous protein; as opposed to a globular protein, like casein, that is connected neatly into a sphere. Casein is soluble in water while the fibrous whey protein is not.

Imagine a hand-knit sweater, the kind you’d get from your grandma as a Christmas gift that is so warm and yet so itchy at the same time. Ultimately, the sweater started as a long, straight length of yarn, then transformed, connected, folded into a specific shape with a specific purpose – to keep you warm. Change any part of its form, and it might not function anymore. That is also true with protein fortification in RTD beverages. If a process changes the protein form, then the functionality of the protein may be changed as well.

What happens when you heat proteins up to 140°C for RTD processing?

If the sweater is our protein, heating it would be akin to taking a pair of scissors and randomly cutting single pieces of yarn. You’d still have a sweater.  But now it might be fraying in certain places, developing a hole in the sleeve, or maybe even unraveling at the bottom. Heating protein at such high temperatures has a similar effect; the little bonds connecting the amino acids start to ‘get cut’ and the structure of the protein is weakened.

When protein is heated and made shelf-stable something must be done to protect the protein.  Otherwise, it will be ‘unraveled’ and degrade until the beverage becomes un-drinkable.  It’s impossible to keep the protein’s structure together forever, but it is possible to push it off until after the end of shelf life.

How can you tackle these challenges?

You will need a variety of specialized knowledge and equipment to accurately bench, test and trial protein fortification in RTDs. The best coarse of action is partnering with a consultant with access to the required equipment and knowledge of how closely it will mimic a scale-up.

Agropur is both a formulator and contract packer. And our team has a variety of industry contacts if you are looking for something specific that we don’t service. Do not hesitate to contact us, as we would be happy to assist you as you start your journey!