The plant-based milk trend has expanded in recent years, not only because of consumer concerns around environmental sustainability of dairy milks, but also because of evidence that milk alternatives have some nutritional benefits. These include associations with helping to protect against cardiovascular disease and reduce blood glucose and cholesterol levels.
However, this is not always the case, and in the past, some studies have pointed to the nutritional superiority of cow’s milk.
A new study, published in the journal, Food Research International, suggests that processing methods have a role to play in reducing the nutritional quality of plant-based milks.
How does processing affect the chemical makeup of plant-based milks?
Plant-based milks are developed by soaking and grinding plant materials to release oils and proteins, stabilising the result with thickening agents and emulsifiers, and fortifying with key nutrients such as calcium, riboflavin and vitamin B12.
Other techniques, such as high-pressure homogenisation and ultrasound, are sometimes used to increase shelf life and product stability, and reduce off-taste. Heat treatment is often an important part of this process, and the Maillard reaction is a common heat-induced reaction. This reaction is well known for forming melanoidins, brown pigments that give foods such as steak, bread and toasted nuts their brown colouring. It also results in the formation of Maillard Reaction Products (MRPs), compounds which, researchers believe, may have the potential to reduce the digestibility of proteins, and therefore the overall nutritional value of foods.
The study hypothesised that plant-based milks, because of their different amino acid profile and greater amount of carbohydrates, may have a higher susceptibility to the formation of MRPs.
MRP’s have a negative impact on the nutritional quality of plant-based milk, explains Marianne Nissen Lund, one of the researchers on the study. The reason for this being that they all lead to the modification of essential amino acids.
How different is the nutritional content of plant-based milk to cow’s milk?
Comparing UHT-treated cow’s milk to a range of plant-based milks, the researchers found that the nutritional content varied significantly.
For example, the rice drink and the majority of oat milks tested had a higher carbohydrate content than the UHT-treated cow’s milk, whereas the soy and almond drinks contained lower levels of carbohydrates. In terms of carbohydrate types, only lactose was found in the cow’s milk, while dextrins, maltotriose, maltose, and in some cases glucose, were found in the plant-based milks.
In terms of protein content, soy milk had higher levels of protein than the UHT-treated cow’s milk, whereas all other plant-based milks had a lower protein content.
All the plant-based milks assessed contained significantly lower levels of essential amino acids than cow’s milk.
How does processing affect these differences?
MRPs, which are produced through the heat-induced Maillard Reaction, were found at significantly different levels in plant-based milks, compared with cow’s milk.
Furosine, a marker of the early stages of the Maillard Reaction, was found at lower levels in most plant-based milks than UHT-treated cow’s milk.
However, per gram of protein, all AGEs, advanced MRPs, were higher in plant-based milk than cow’s milk.
LAL and LAN concentrations were also higher in plant-based milk. LAL and LAN are amino acid cross-links, and not formed during the Maillard Reaction, but during alkaline or heat processing, explains Lund. They also have a significant effect on nutritional composition, lowering protein digestibility.
In order to reduce the negative effects on nutritional quality detailed in the study, suggests Lund, the industry could use less intensive heat treatments.
Sourced From: Food Research International
‘Investigation of Maillard reaction products in plant-based milk alternatives’
Published on: 28 November 2024
DOI: 10.1016/j.foodres.2024.115418
Authors: M Pucci, H Gül Akıllıoğlu, M Bevilacqua, G Abate, M N Lund
