Protein is moving into the beverage category, and it's not just for athletes anymore. However, formulating good-tasting whey protein-fortified drinks requires some finesse. Starla Paulsen gives a tutorial on making whey work
For many years whey proteins have had a following among athletes and body-builders. In recent years, this popularity has spread to other everyday health and wellness seekers. Whey proteins contribute to a beverage's overall nutritional appeal, and can enhance formulations with functional benefits. While these features can make creating a whey protein-fortified beverage irresistible, it is not always the easiest task to accomplish. Fortunately, with an understanding of the basics, an amazing tasting beverage can be produced.
There are a few basic parameters to keep in mind for development of beverages with whey proteins. Always hydrate the protein first by itself in the water. Add the protein slowly with moderate agitation. Don't turn up the speed on the agitation or very large stable foam may be formed, which can be detrimental to further processing and stability. A powder inductor can be used to help hydrate the protein quicker, and an antifoam agent may be incorporated to reduce the formation of foam. Many factors can affect the functional properties of the proteins including pH; ionic strength; sugar content; and the complexity of the other beverage components such as vitamins, minerals, fats and salts. Be mindful of potential ingredient interactions and the reactions that may occur in processing (pH shifts, foaming) and in packaging (separation, precipitation).
In the world of beverages there are two basic categories: low acid (above pH 4.0) and high acid (below pH 4.0). When working with whey proteins, beverages can be split into three categories based on functionality at different pH ranges. These categories are neutral pH (pH 6.0 — 7.0), intermediate pH (pH 3.5 to 4.5), and acid pH (pH
Neutral pH beverages
These beverages are those that fall in the pH range around 6.0 to 7.0, including meal-replacement shakes, high-protein sports supplements and milk-based products. They are usually UHT or retort processed for shelf-stability, and can include other ingredients, especially vitamins and minerals. The biggest challenge, though, is heat-induced gelation. Whey proteins are soluble at neutral pH; however, they will form heat-induced gels (especially at concentrations >six per cent).
There are a few tricks to creating a whey protein-fortified beverage at neutral pH. First, choose the correct type of whey protein, one with reduced water-binding capacity such as a hydrolysed version. If the protein cannot bind water, it will stay fluid through processing. At this pH, the use of stabilizers — usually a carrageenan or cellulose type — and buffers such as sodium phosphates can also protect the protein from the heat treatment. Finally, homogenisation during the processing may be needed to create the desired texture when using higher protein levels.
Acid pH beverages
Acidic beverages (below pH 3.5) includes high-protein sports drinks, isotonics and protein-fortified waters. Whey protein is the perfect choice for this pH range because of its excellent clarity and heat stability at low pH. If a clear product is desired, the clarity increases as the pH decreases. These beverages are typically hot filled, and heat-induced gelation can occur if the balance between protein concentration and pH is not maintained.
In general, the higher the protein content, the lower the pH must be. For example, a two per cent protein beverage could be processed at pH 3.0, whereas a seven per cent protein beverage needs to be at pH 2.7. The major issue that occurs at this pH range is as the pH decreases, the astringency increases. Astringency can be defined as the drying, roughing and sometimes puckering sensation that is experienced when consuming certain foods. This is not usually a desired property for beverages. To overcome this challenge, choose the correct protein — pre-acidified whey-protein isolates help to reduce astringency in high-acid beverages (see chart, below). Masking flavours can also be utilised.
Intermediate pH beverages
These fall in the pH range around 3.5 to 4.2. To developers of protein-fortified beverage, these are known as the 'holy grail' of beverages. They include smoothies, yoghurt beverages and juices. This is the pH range that is most pleasing to consumers and it is the most technically challenging to fortify with whey proteins. At this pH range the greatest hurdle is working with the whey proteins in their isoelectric zone. When a protein is at its isoelectric point, it has no charge and will generally precipitate out of solution.
Whey proteins can be the solution of choice for formulating great tasting, nutritious and functional beverages that consumers demand. Just keep in mind that ready-to-drink beverages are a very delicate system with the potential for complex ingredient interactions and processing issues. Adding protein to these beverages is still relatively new and creates a learning curve for most beverage companies. Use your ingredients-supplier resources to help.