Mayonnaise, milk, butter and various sauces are among the products most associated with the term emulsion.
While this technique is widely used in the food industry, it also has a vital role beyond the kitchen. Emulsifying involves homogeneously mixing two liquids that do not blend well naturally, such as oil and water.
Although this process may appear simple at first glance, it is essential for the manufacture of numerous products such as paints, cosmetics and certain pharmaceuticals.
The Biopren research group at the University of Cordoba has successfully transformed avocado pruning residues into a valuable resource for making emulsions. Specifically, they have extracted the lignin from avocado — one of the primary components of plant cell walls that acts as a natural glue — and transformed it into an emulsifying agent. This agent acts as a bridge between two liquids that do not mix well, helping to stabilize emulsions and maintain their consistency over time.
With this objective in mind, the team, affiliated with the Chemical Institute for Energy and the Environment (IQUEMA), has processed lignin in powder form down to the nanometer scale, transforming it into an emulsifier in a mixture of water and soybean oil, a common combination used in the manufacture of various products.
“One of the problems with conventional emulsifiers is that they are petrochemical based,” explains Ramón Morcillo, the study’s first author. “Now, we have successfully developed a biologically based emulsfier with activity comparable to other bioemulsifiers on the market,” he emphasizes. In fact, according to the research findings, the new emulsifier made from avocado pruning residues can maintain the stability of the mixture for 27 days, meaning the emulsion remains intact without separating back into its original two phases during that time.
'Enhanced' antimicrobial and antioxidant activity
Another advantage of the developed compound is the inherent antioxidant and antimicrobial properties of lignin, which could improve and extend the shelf life of foods when used in culinary emulsions. The study also suggests that these qualities could be further strengthened by adding quercetin — a compound found in fruits and vegetables known for its beneficial properties for health — in the mixture.
As the study’s first author explains, one of the main problems of quercetin is its low solubility in aqueous environments, such as gastrointestinal fluids, which limits its absorption in the body. For this reason, the researchers encapsulated the emulsion itself, that is, they provided the emulsion with a protection that could potentially improve its availability in the organism. Despite this, the Morcillo pointed out that “the study didn’t measure the bioaccessibility of quercetin and it’s something that will have to be explored in future research.” The researcher also underlined that the field of functional foods must always be supported by scientific evidence.
For the time being, the team, which just over a year ago successfully transformed avocado pruning residue into biodegradable food packaging, has now found a new use for a waste with little added value; a waste from a food crop of which Spain is the leading producer in Europe and whose cultivation has grown exponentially in recent years.
