Processes and technologies for protein extraction

Vegetable proteins products first appeared on the market in the 80s, with the fungus-based meat created by Quorn, until new vegetable products were developed, covering every category, from dairy products, such as milk and vegetable cheese, to meat and fish.

Today, not only large companies, but also many young startups are investing in the development of innovative vegetable products, always experimenting with new sources, such as legumes, oilseeds and even grass, used to extract vegetable proteins, although the last one is mainly used for feed purposes. This is because at the basis of the growth of the segment of vegetable products there is an increase in demand from consumers, who, guided by ethical or health reasons, choose to consume vegetable products aspiring to a healthier and more sustainable lifestyle. In this direction, the same consumers, more and more educated and aware, are looking for vegetable products that meet many criteria, such as taste and texture, also giving value to the sustainable practices adopted by the company. For this reason, in line with the research of new vegetable protein matrices, the methods of extraction of these proteins are also being explored, in order to have processes that are sustainable, both economically and environmentally, by wisely using the available resources.

What about the extraction methods?

Plant proteins are traditionally extracted using solvents, through a method known as wet separation. In this process, plant proteins are isolated by aqueous extraction under alkaline conditions, followed by centrifugation, isoelectric precipitation, washing, neutralization and drying. Quoting the article “Dry fractionation methods for plant protein, starch and fiber enrichment: A review“ using this method it is possible to obtain high purity protein powders, known as protein isolates, with a protein concentration higher than 90%.

A second extraction method is known as dry separation, which is an alternative to wet separation and does not require the use of solvents.

Dry separation combines milling and dry separation techniques such as air classification. This process can fractionate cereal and legumes into protein-enriched and protein-depleted fractions. In detail, milling is used to separate the individual components, while air classification fractionates the product according density and/or particle size into protein-enriched fractions. However, when the particles do not differ much in density and/or size, it becomes difficult to achieve effective separation. In this case, we can use an alternative fractionation method known as electrostatic separation, which split particles based on their different triboelectric charge behavior.

In general, dry separation uses less energy and water than wet separation, and since it does not require the use of solvents or high temperatures, it is easier to preserve the structure and functionality of proteins. However, these technologies are not suitable for the production of protein isolates yet (protein content >90%), but only of protein concentrates, i.e. powders with a protein content higher than 50%.

One last method, which has recently become very interesting with regard to protein extraction is fermentation. Fermentation has been used in food production since ancient times, for example to preserve food and create alcoholic beverages. It is a process which uses microorganisms, decomposing sugar in order to obtain other organic compounds, such as lactic acid or alcohol.

In recent years, several studies have been conducted for the application of fermentation as a method for the production of new innovative foods. In particular, two types of fermentation can be used to produce proteins: biomass fermentation and precision fermentation. According to this article biomass fermentation uses the high-protein content and rapid growth of microrganisms to efficiently make large amounts of protein-rich foods. Precision fermentation uses microorganisms to produce specific functional ingredients, enables alternative protein producers to efficiently make specific proteins, enzymes, flavor molecules, vitamins, pigments, and fats.

Sustainability of plant-based protein separation methods

The constant research for the development of innovative vegetable products will surely grow in the coming years, in line with the constant demand from consumers. Currently, the panorama of plant-based products is becoming increasingly differentiated, thanks to the diffusion of products not only based on soy, but also based on peas, chickpeas, broad beans and others. However, to be considered healthy and sustainable, a vegetable product must not simply contain vegetable ingredients, but also the process applied to extract them must meet sustainability standards. Innovation and research will undoubtedly optimize these extraction processes in order to have an ideal method that uses the right amount of resources, such as water and energy, reducing the use of solvents and protein denaturation, resulting in a high purity protein powder with good functional properties.