Plant proteins have come to the fore for a number of reasons. For one, [the raw materials generally] cost less than animal proteins. But they also align well with a number of emergent consumer trends, such as vegetarianism, veganism and sustainability. Thus far, however, proteins’ functionality as ingredients has lagged behind that of animal proteins. This has spurred research into improving plant protein ingredients
Prof. B. Pam Ismail, Associate Professor, Dept. of Food Science and Nutrition, and Director of University of Minnesota’s Plant Protein Innovation Center, discussed some intriguing technologies that should expand the use of plant proteins in foods and beverages. She also provided details on two new, interesting protein-rich oilseeds under evaluation for potential commercialization.
“When investigating new and novel proteins, we need to know how to obtain desired protein ingredient functionalities through cost-eﬀective extraction and processing techniques,” said Ismail. In addition, she said, “If they don’t taste good, consumers won’t eat them.” Cost-eﬀectiveness, functionality and taste must go hand-in-hand.
The search for new plant protein sources to meet rising global demand led Ismail’s researchers to focus on alternate sources to soy, such as peas. She noted that, in 2012, 81% of commercial (plant) protein ingredients were obtained from soy. By 2017, soy protein’s market share had dropped to 61.4%, while pea protein’s share rose from 7.6 to 21.2% and continues to rise. Yet, pea protein processing technology remains in a relatively early stage, said Ismail.
One big quality variable is solubility. Most plant proteins (globulins) exist deeply imbedded within fiber and starch matrices, with water-loving (hydrophilic) amino acids on the surface and water-repelling (hydrophobic) amino acids within the interiors of the protein molecules. The hydrophilic amino acids on the surface are what render proteins soluble. During processing, however, conditions such as temperature, shear or changes in acidity can cause proteins to unfold (i.e., denature) and expose the interior hydrophobic amino acids, causing the proteins to aggregate and precipitate. Therefore, the objective of plant protein extraction and purification is to minimize the denaturation conditions that compromise protein integrity and function. Ismail outlined some of the new technologies being developed at her research center.
The first step is to optimize extraction conditions, said Ismail. She cited three techniques: isoelectric precipitation, salt extraction and ultrafiltration. In addition, Ismail’s researchers are investigating new techniques whereby to modify the surface characteristics of extracted proteins in order to enhance stability, such as targeted enzymatic modification (the selective hydrolysis of protein sub-units); glycation (conjugation of a reducing carbohydrate with a protein to increase stability); and cold plasma (the application of partially ionized air to oxidize protein surfaces).
Comparing extraction techniques, Ismail averred, “We found that salt and ultrafiltration yielded proteins that were less denatured and more thermally stable than proteins extracted through pH modification.”
As Ismail explained: “When considering current commercially available protein choices for beverage applications, whey remains the dominant protein isolate, with close to 100% solubility. Soy protein isolate isn’t that great, with slightly less than 20% solubility, but it is still better than pea protein isolate, which exhibits 5-6% solubility. Using salt-based extraction, we were able to increase pea protein solubility six-fold. When combined with targeted enzyme hydrolysis, we approached 90% solubility; with glycation, we achieved 100% solubility.” (Similar to whey protein, that is.)
Ismail’s group has been applying these protein molecule and process-modification techniques to two promising oil seeds, camelina and pennycress, with encouraging results. “These are winter crops favored for short growing seasons, and both are rich in fat (30-40%) and protein (25-30%),” she said. Modified camelina protein, in particular, shows promise of exhibiting stability in highly acidic beverages, although she admitted some flavor issues remain to be resolved, especially in pennycress protein.
In response to a question from the audience, Ismail added that, while the focus of her team’s research has been on increasing protein solubility, the same techniques could also apply to increasing protein hydrophobicity (insolubility), leading to gluten-free protein alternatives for baking, for example.
In a global market where protein demand is likely to remain, in Ismail’s words, “steep and long-term,” the development and commercialization of new protein sources and modification technologies can only expand product developers’ fields of dreams.
“Plant Proteins: Structural and Functional Properties & Use in Food and Beverage Formulations,” Prof. B. Pam Ismail, Ph.D., Associate Professor Dept. of Food Science and Nutrition, and Director of University of Minnesota’s Plant Protein Innovation Center
This presentation was given at the 2019 Protein Trends & Technologies Seminar. To download free presentations and others on improving plant protein ingredients as well as the Post-conference summary of this event, see posts in the Protein Trends & Technologies Seminar R&D Academy.