Beverages offer an effective way to understand the opportunities and difficulties associated with formulating and fortifying with protein. L Steven Young, PhD, assesses the obstacles
In order to understand applications and limitations of working with protein in a beverage format, it is necessary to consider not only protein sources available, functionalities and desirable use rates, but also beverage types and associated processes and packaging, chemistries, physics and microbiologies. Protein ingredients vary in their function and compatibility in various beverage types.
Many types of commercially available protein ingredients are available (See Table 1, below). Typically, proteins can be classified as being of plant, egg or dairy sources. More typically, soy or dairy-based proteins are used in beverages. However, both soy and dairy can have severe functional (solubility, viscosity), sensory (colour, flavour, effect on flavour, thickening, transparency), or nutritional (amino acid content and use rates) limitations.
The good news is these limitations can be overcome by novel use of the protein of choice, modified proteins, other protein sources and/or protein blends.
Functionality and execution
It is critical to consider the following features of any given protein ingredient when starting the task of formulating with protein in a beverage format.
Composition: The keys to all functionality are total protein, fat, simple carbohydrates (including sugars) and dietary fibre. Further, the amino acid composition of protein and its digestibility are critical to selection of any given protein for nutritional fortification.
Bound fat, such as total fat, saturated fat and trans fat, needs to be taken into account as it can affect both nutritional labelling declarations like total fat and calories, as well as claims such as low fat and fat-free. Dietary fibre, both soluble and insoluble, can offer opportunities and quality risks. Minor nutrients such as minerals, vitamins and sterols can influence function, flavour, nutritional composition and stability in the finished food.
Solubility: Because beverages contain solids dissolved or suspended in water, either within an emulsion or in a colloidal dispersion, the utility of protein ingredients will depend on both general solubility in water and solubility across the full spectrum of pHs. In some instances, low pH can significantly modify flavour and function — both positively and negatively. It depends. Certainly, ready-to-drink (RTD) beverages require more demands related to solubility than dry drink mixes. But dry drink mixes demand more dispersibility.
Dispersibility: Proteins can have varying solubilities and be more or less dispersible at the same time. Dispersibility is critical to both RTD beverage mix making and to ease of use of dry drink mixes. Where solubility may or may not be easily managed, dispersibility can be managed easily by applying mechanical energy to mix making and/or pre-agglomerating or instantising the protein ingredient for more ready dispersion. The rate of dispersion can also be managed depending on how the ingredient or ingredient-containing mix is pre-treated, formulated and handled.
Emulsification and its stability: The ability to emulsify and stabilise fat/oil in an oil-in-water dispersion is a positive function of most proteins. When emulsified, fat/oil can offer milky-white or off-white drink compositions. However, if beverages are desirable with no 'milkiness' or colour, the ability to emulsify even the smallest amount of inherent fat/oil can cause problems.
Water holding and thickening: Proteins are classic water binders. This typically results in viscosities that may or may not be desirable. Further, any modification of protein functionality during manufacture of a beverage can affect final beverage viscosity both positively and negatively. Care is necessary to understand the performance of the selected protein ingredient and conditions of its intended use.
Stability: Not all proteins are 'stable' under all formula and process conditions. Stability is mainly based on the ability of a protein to remain soluble and dispersible, maintain its nutritional function, and not negatively affect colour or flavour. Protein stability can be affected by the process by which the ingredient is made, use rates, other ingredients (minerals, acids, hydrocolloid stabilisers, etc), and other factors. Again, it is important to consider these with your protein supplier before moving forward.
Colour: Proteins have colour of their own that can vary and affect milky-type whiteness, transparency, and in some cases, water-white clarity of beverages. The larger the molecular weight of the protein, the lower the per cent protein in the ingredient. The more fat added or associated with the protein, the more milky-type beverages can be made. When proteins are hydrolysed, fat is removed, and protein as per cent of the ingredient increases; thus, transparent or water-white beverages are possible.
For example, soy and whole-milk proteins are not clear in solution. However, hydrolysed whey (a dairy protein) and canola protein can be formulated into clear solutions. The downside to using hydrolysed proteins is the extreme bitter nature of the ingredient. Formulation considerations can minimise this downside risk.
The reaction between proteins and reducing sugars (ie, Maillard-type nonenzymatic browning) can limit the amount and type of protein and sweetener system that can be used. Often, management of the sweetener system is easier than any modification of the protein system. In any event, reaction by-products can also affect minor nutrients such as vitamins.
Flavour and taste: Flavour includes aroma and the elements of taste (sweet, salty, bitter, sour and savoury, aka unami). Anything that affects these elements affects both the flavour of the protein ingredient itself and the finished beverage. Further, high molecular-weight proteins tend to bind fine flavour chemicals, particularly aromatic compounds. This can make just about any protein-containing beverage difficult to flavour.
Some modification of the ability to bind flavours can be accomplished by adding any one of a number of other ingredients. These may include fat, salts, oils and other lipids (many 'off flavours' are fat-soluble), and also by modifying the pH of the beverage — the amount and type of acid can affect protein's ability to bind and hold aromatics. Further, proteins are buffers and it can take unusually high use rates of acid to drive pH down. This can negatively affect harshness, sourness and bitterness in the finished beverage. Thus, in acid beverages, protein use rates will be significantly lower than in more neutral beverages.
Texture: A major influence of solubility, or limited solubility, is its effect on smoothness, coarseness or grittiness of the beverage. This can be due to the specific solubility of the protein itself or the solubility of an associated component of the protein, such as insoluble fibre. It may be possible to modify solubilities, but certainly high solubilities are more highly desirable.
Foaming and foam stability: Foaming is typically an effect due to the water-binding behaviour of protein and entrapment of air. Unless specifically required, foaming can seriously limit mix making, processing, packaging and plant efficiencies. Typically, foaming is undesirable and stable protein foams are even more undesirable. With care, though, even high-foaming proteins can be made to function in beverages.
Availability and cost: While balancing all the various functional attributes of proteins, cost considerations also need to be managed. Typically, proteins from commodity-based raw materials with lower protein contents are less expensive. The more 'refined' the protein, the higher the protein content, and the greater the utility, the more costly on a cost-per-unit protein basis.
However, for example, proteins hydrolysed can be attractive costwise in exchange for novel functionalities, such as colour, transparency or solubility. Thus, it is always desirable to cost-complete formulas and not judge ingredients by a sales price.
Table 2 classifies beverages based on processes and/or packaging used to render the beverage commercially sterile for distribution and consumption. Depending on process and packaging considerations, formulators need to assess supply chain requirements to maintain the safety and suitability of the beverage. Typically, beverages are distributed either at room temperature (20-22oC) or under refrigeration (
Formulas must tolerate whatever variables that need to be applied. This can range from formula (eg, acidity, pH, solids, sweetener systems, amount and type of protein), process (eg, culturing, physical and thermal stress), packaging (eg, glass, paper, flexible, plastic), and distribution conditions. This also means any given protein or protein blend must tolerate these conditions are well.
Formulation objectives of course need to be considered. These may include desirable nutrient content claims, structure/function claims and any available health claims. These would include any and all claims related to protein. Of course, local and/or federal regulatory authorities determine what can or cannot be said about the finished food. These can differ market-to-market and protein-to-protein so care is necessary to formulate for the specific need. This is all related to use rates and other beverage compositional factors.
Formulating with protein
Protein use rates can vary. Typically, 8-10g protein per 236ml serving is a desirable target. More than 10g protein can negatively influence acceptability. For reference, whole milk itself delivers about 8g protein per 236ml serving. Milk need not be the target, as many beverages, such as juices and carbonated drinks, do not contain protein at all.
However, evolving protein hydrolysates and novel application techniques can be used to achieve significantly higher protein use rates than normal. Since this always varies with the specific protein and specific treatment to the protein, it is recommended to seek assistance from your protein supplier. Again, it is critical to match functional and sensory performance with application use rates, beverage types and processes.
For beverages, not all rules apply in any given application. Care is necessary when considering what and how to formulate. Further, consideration of marketing, processing, packaging and distribution options needs to play a role. No formula can be created without consideration of economics. Every beverage concept must deliver nutritional efficacy and economic opportunity while balancing functional and sensory performance. It can be a daunting task, but the consumer market is demanding higher-protein offerings, and protein sources and beverage technologies are coming together to provide them.
L Steven Young, PhD, is principal of Steven Young Worldwide in Houston, Texas, a technical and nontechnical consulting firm specialising in the development and use of novel new food ingredients. www.stevenyoung.net Respond: [email protected]