Plant-based drinks face multiple barriers as suitable dairy alternatives: NUS-led study

The global surge in demand for plant-based alternatives to traditional dairy milk has reached unprecedented levels, driven by ethical concerns, environmental sustainability and health consciousness. In recent years, plant-based drinks have emerged as a diverse and popular choice, offering a range of nutritional benefits and catering to lactose-intolerant individuals, as well as vegans and vegetarians.

Concerns over dairy milk production’s environmental impact revolve around land and water use, greenhouse gas (GHG) emissions and animal welfare, and plant-based drink production generally requires fewer resources and generates fewer emissions. Nutrition-wise, plant-based drinks are said be a rich source of essential nutrients, including proteins, dietary fibre, fats, vitamins and minerals — beyond the calcium and protein associated with dairy milk.

These alternatives are typically derived from plant sources such as nuts, grains, legumes and seeds; examples include almond, soy, oat, rice and coconut drinks. Each variety usually has a unique flavour, texture, and nutritional composition, providing consumers with a broad array of choices to suit individual preferences and dietary needs. However, considerations such as amino acid profiles, digestibility and the presence of anti-nutritional factors should be taken into account.

Compelling components?​

A review conducted by researchers at the National University of Singapore, King’s College London, Changzhou University and Shenyang Agricultural University found soy-based plant drinks to have the highest protein content, comparable to that of cow milk.

These are considered a complete protein source for adults, with other plant-based drinks exhibiting lower protein content (rice-based drinks having the lowest). Differences in amino acid profiles and the presence of anti-nutritional factors contribute to variations in nutritional value, with plant proteins generally considered slightly lower than animal proteins.

Dietary fibre, which is crucial for promoting gastrointestinal health, controlling blood sugar and cholesterol levels and providing satiety, is a notable component in plant-based drinks. The prebiotic characteristics of certain fibres in these drinks contribute to gut microbiota health, offering potential benefits for immune responses, neurological health, and weight management.

Additionally, plant-based drinks predominantly contain unsaturated fatty acids, offering positive effects for cardiovascular health by lowering cholesterol levels. These drinks are rich in minerals, including calcium, magnesium, selenium, potassium, zinc, phosphorus, copper and manganese. They also provide fat-soluble vitamins, with advantages over cow's milk in terms of vitamin E and A content, though water-soluble vitamins may require fortification.

At the same time, plant-based drinks are a source of beneficial bioactive molecules, such as flavonoids, phenolic acids, lignans and phytosterols. These compounds contribute to antioxidant properties, supposedly offering health benefits like anti-cancer effects, protection against radiation damage, and lipid-lowering effects. The inclusion of these bioactive molecules in plant-based drinks presents potential advantages for overall health.

Factors of flavour​

In the plant-based drink processing sector, industry leaders are confronted with multi-faceted challenges that demand strategic solutions for sustainable evolution. Key issues include the persistent beany smell and urease in soy drinks that affect their culinary appeal, and the presence of starch granules in oat drinks that affect their otherwise smooth taste. Other challenges include product safety, nutritional considerations, and stability during processing.

Plant-based drink processing involves several steps, from pre-treatment of raw materials to extraction, enzymatic processing, fermentation, germination, separation, formulation, homogenisation, heat treatment, and packaging. Each step plays a crucial role in determining the final quality of the drink, while the flavour of plant-based drinks plays a crucial role in consumer acceptance.

Aromatic compounds, including aldehydes, ketones, alcohols, esters and acids, contribute to their overall flavour profile. Understanding flavour formation pathways, such as the Maillard reaction, helps in optimising the aroma and minimising off-flavours. Selecting high-quality ingredients and employing environmentally friendly processing techniques contribute to the market potential of plant-based drinks.

Oxidative fat degradation is a common issue in developing plant-based beverages, leading to off-flavours and undesirable tastes. Researchers have found that when plant-based drink ingredients are stored under normal conditions, their quality remains stable. However, during processing, the activation of endogenous lipoxidases can trigger oxidative fat degradation, resulting in the development of rancidity and other unpalatable flavours.

Oxidative fat degradation in plant-based drinks takes place via two main pathways — enzymatic and non-enzymatic. Saturated and unsaturated fatty acids undergo oxidation, forming various flavour compounds, including aldehydes, alcohols, esters, lactones and methyl ketones.

Soy drinks are particularly susceptible to off-flavours, with specific aldehydes and their corresponding alcohols being significant constituents. Furthermore, factors like heat, light, photo-sensitisers, oxygen and transition-metal ions contribute to non-enzymatic oxidations, generating volatile compounds such as aldehydes and furans.

Health benefits and risks​

The health benefits of plant-based drinks hinge on their structure, particularly their cell wall composition. Cell walls, rich in cellulose and polysaccharides, limit the dissolution of proteins, oils, fibres and phytochemicals. Optimising processing technologies, such as heat treatment and extrusion, is crucial to break down cell walls and enhance nutrient dissolution.

Heat-sensitive health risk factors, including cyanogenic glycosides and anti-vitamin factors, pose challenges. Elimination methods, such as enzymatic hydrolysis and fermentation, are employed to address allergens like soybean proteins and gluten. To ensure product safety, manufacturers use various methods to achieve the elective reduction of phytic acid in different raw materials.

Furthermore, multi-phase dispersion systems in plant-based drinks are prone to physical instability and phase separation. Factors contributing to instability include force-induced separation, floating and sinking of particles, and aggregation. Chemical and bio-chemical processes like oxidation and hydrolysis further threaten stability, impacting the safety and taste of plant-based drinks.

Rich in carbon and nitrogen sources, plant-based drinks are susceptible to spoilage. Challenges include mildewed or spoiled raw materials, improper sterilisation methods and process control issues. Developing efficient methods to control harmful micro-organisms is imperative to ensure the safety and shelf life of plant-based drinks.

Multi-faceted solutions to multi-faceted challenges​

The plant-based drink industry faces a critical bottleneck in consumer acceptance due to bitter and astringent flavours. The imperative lies in addressing scientific issues and exploring new extraction technologies to improve flavour. Presently, researchers are exploring non-heat treatment technologies and novel processing methods to extend shelf life and improve the overall sensory experience of plant-based drinks.

At the same time, the industry must tackle challenges like environmental sustainability, supply chain resilience, nutritional adequacy, allergen labelling precision and adherence to evolving regulatory frameworks. Moreover, market dynamics, consumer education, infrastructure development, waste management and regional preferences add layers of complexity to the development and commercialisation of plant-based alternatives to dairy beverages.

The researchers concluded that collaboration, innovation, and adherence to ethical and labour standards were essential for the sustainable development of the plant-based drink processing industry, saying: “Addressing these complexities while upholding ethical and labour standards constitutes an imperative dimension of sustainable plant-based drink development, necessitating a collaborative effort among stakeholders to navigate these intricacies effectively.”

Source: ​National Center for Biotechnology Information​

“A Review of Plant-Based Drinks Addressing Nutrients, Flavor, and Processing Technologies”​

https://doi.org/10.3390/foods12213952​

Authors:​ Aijun Xie, et al​.