The increasing cost of animal source proteins has motivated the food industry to look for alternative protein sources for use as functional food ingredients. Yet while plant protein production can be more sustainable, problems may occur with extraction and loss of functional qualities.
The fruit of the date palm Phoenix dactylifera L. is one of the richest fruit-based sources of protein, and is an important commercial crop in hot dry areas of the world. Its seeds contain 5-7% protein by weight according to previous studies, but little is known about their functional properties.
Researchers from Heriot-Watt University in Edinburgh said in a previous paper that almost 800,000 tonnes of date palm seeds from global production of dates were wasted, according to 2007 data from the Food and Agriculture Organisation (FAO) of the United Nations (UN).
In their current study published in Food Chemistry, the scientists investigated the extraction of protein from date seed, characterisation of their proteins and emulsifying properties.
Study details
Using Deglet Nour dates from Tunisia, the seeds were milled with a hammer mill to obtain date palm seed powder. The powder was then defatted and the protein isolated and analysed.
They found over 300 proteins of which 91 were identified with confidence. As expected the majority of proteins were associated with metabolism and energy functions which supported the growing plant.
The authors compared the emulsifying properties of date seed proteins to soy protein isolate and whey proteins, which are used widely in the food industry.
They found the stability of the emulsions produced from all three proteins was similar at the pH values tested and concluded that this combined with the large emulsion droplet size suggested potential for date seed protein as a functional food ingredient.
Extraction challenge
However, when asked about the potential of date seed protein in foods, author Stephen Euston commented on the difficulty of extracting the protein from date seeds.
He said date seeds are fed to camels who use their incredibly strong jaw and digestive system to break them down, but extracting the protein in a food production setting proves more challenging.
Having only managed to extract 45% pure protein using food grade methods, Euston told NutraIngredients: "We would need a much better extraction method to extract protein that could be used in food systems."
Date protein, like other plant proteins, has a good amino acid profile. "In terms of nutrition, they’re fine, its functionality that lets them down a little bit," he said.
Sustainable fungal proteins
Euston and colleagues are currently working with fungal proteins produced from waste streams of food manufacturers. This is already food grade and has very good functionality.
"Fungal proteins inhabit this halfway house – they don’t have the problems of animal proteins as they’re sustainable and they don’t seem to have the functional flaws that plant proteins have," he said. "How much protein we’ll be able to produce will be the issue."
He said any further date seed protein research was "on hold" at the moment, adding "it may just be that it’s not economically viable".
Source: Food Chemistry
Published online ahead of print, http://dx.doi.org/10.1016/j.foodchem.2015.11.046
“The major proteins of the seed of the fruit of the date palm (Phoenix dactylifera L.): Characterisation and emulsifying properties”
Authors: I. Akasha, L. Campbell, J. Lonchamp, S.R. Euston