Protein, from source to digestibility: important for healthy ageing

Global demographic shifts and a world population projected to reach 9.7 billion by 2050 lead to an increasing demand for high-quality nutritional products, especially for elderly people. This will put pressure on food production and protein supply. To meet this growing demand, producers are combining vegetable and animal proteins and finding innovative ways to use available proteins more efficiently. The biggest challenge is developing high-protein applications with the right properties (structure, texture, flavour, digestibility) without increasing the food product’s carbon footprint. 

Everyone needs protein

Elderly people need to maintain their muscle mass, so their diet must contain enough highly digestible protein. Other consumers need foods that help control weight and reduce the risk of obesity. For them, too, high-protein products can play an important role because they create a relatively high sense of satiety. 

While proteins have obvious benefits, products with a high protein content can be undesirable from a sensory perspective: too viscous and hard to swallow in liquids, or too chewy in a solid state. Texture problems can also occur in low-fat products where fat has been replaced with extra protein. These products are often perceived as drier and less juicy. To improve consumer acceptance of high-protein products, it is crucial to control their viscosity and texture. This means decreasing liquid products’ viscosity and improving the overall mouthfeel of both liquid and solid products. 

Optimal digestibility

To meet the growing demand for protein, food manufacturers are turning to high quality proteins from alternative sources, such as plants, algae and insects. Protein quality is related to a good amino acid composition. In general, animal proteins are better sources of the essential amino acids, but there certainly are high quality plant sources as well. Digestibility is also of importance. Whether the proteins can be used by the body depends on how much of the protein is broken down in free amino acids and very small peptides, and for some physiological functions it is important how fast this happens. The impact of plant proteins on health may be increased by different solutions: enhancing intake, by providing higher protein products, improving amino acid composition (for example by combining protein sources), or by enhancing digestibility, for example by smart processing or applying fermentation. 

In vitro models of digestion mimic the enzymatic and pH conditions in the stomach and small intestine. They measure the gastric behaviour and overall breakdown of the proteins. Using NIZO’s in vitro platform for modelling of food behaviour in the stomach and small intestine, the impact of protein source, processing or fermentation on the digestibility of plant proteins can be compared.  

In vivo measurement

Studies in healthy volunteers can show the impact of differences in protein digestibility.  Malnourished older adults need high levels of essential amino acids, including leucine, to stimulate the formation of muscle protein, but their intake is limited. Oral nutritional supplements can support the protein intake of malnourished people by providing fast-digestible, high-quality proteins. In a trial in healthy, older adults, we evaluated the digestion of a mixture of milk proteins, developed by FrieslandCampina. Consumption of 20 g of this protein mixture (RESANA™) by older volunteers resulted in a fast and high rise in the levels of essential amino acids in their blood, staying relatively high for a prolonged period of time, which is expected to support muscle building. This finding in the human digestion trial may be (partially) explained by limited formation of protein aggregates in the stomach, as shown in a vitro digestion assay. The aggregates stay in the stomach for a longer period, until they are broken down again. Further degradation by the enzymes in the small intestine and subsequent absorption is therefore delayed. 

Processing

Just as the source of protein affects its digestibility, the way of processing could also have an impact on digestibility and hence the quality of proteins. Go4Dairy, a recently successfully completed research programme, focuses on the impact of glycation on protein’s nutritional value. In the literature, Maillard products are associated with negative health effects, including hypersensitivity of the immune system, reduced digestibility, reduced bioavailability of lysine in particular, changes in gut bacteria and even carcinogenic effects. Much remains unknown, however. Go4Dairy’s aim was to reduce and control the glycation of proteins so as to optimise their nutritional value. 

Proteins for the future

High-quality proteins are essential in our diet and are crucial for healthy ageing. In view of the impending protein shortage, current technological developments in plant protein structure, texture, taste and digestibility are all important steps toward creating a sustainable protein supply for a growing world population.