|
 Recent University of Illinois research shows amaranth plants are
a good source of red pigments called betalains, which could be
used in a wider variety of food applications than other
plant-derived pigments. The study, published in Frontiers in
Plant Science, quantified betalain content in 48 amaranth
varieties, providing the food industry with multiple promising
candidates for future product development.
“Our paper serves as a global survey of vegetable amaranth to
determine the diversity in hue, concentration, and chemical
structure of magenta-red color compounds. It also provides
methodology for accurate and high-throughput color
quantification. This information builds a strong basis for
additional work to investigate commercial scale-up and color
performance in food applications,” says lead author Jay Howard,
who completed the study as a master’s student in the College of
Agricultural, Consumer and Environmental Sciences (ACES) at U of
I. Howard is now applications manager at Kalsec Inc.
The researchers selected four dozen amaranth varieties from the
USDA National Plant Germplasm System, representing a full
spectrum of foliage coloration from deep burgundy to lime green.
They grew the plants in a greenhouse and extracted pigments from
stem and leaf tissue using a simple water method, in accordance
with FDA guidelines. Then they fed the extracts through lab
equipment to discover which betalain pigments were most
prevalent.
“We developed a chemical profile for each extract, looking at
the ratio of dominant pigments. Some of the minor components,
which are co-extracted in the water method, may contribute to
the color and stability of the main pigments. These properties
are very interesting for food companies, because you might get a
very bright pink or red color, but then if it fades to brown
after a day, it’s useless. We found that, for some of our
plants, the extracts were stable over days or even weeks. We’re
planning to follow up with more research on that,” says study
co-author Chance Riggins, research assistant professor in the
Department of Crop Sciences at ACES.
Most food companies currently source betalains as a co-product
from red beet production, but Riggins says beet-derived pigments
have some drawbacks.
“Beets are off-putting for some people. Those
earthy flavor compounds often get transferred in a basic
betalain extract. So, food companies are really open to natural
food colorants from alternative sources and doing it in a way
that could extend applications for different food products,” he
says.
The researchers did a basic taste and color test by mixing up a
Kool-Aid-type concoction with their amaranth extracts. “A few
were slightly reminiscent of beets, but mostly we couldn’t smell
or taste anything,” Riggins says.
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For a few amaranth varieties in the study, the
betalain extracts appeared bluer than the bright reds from beets.
With further research, the unique color could fill a gap in the
available portfolio of natural colorants.
Another plus? Amaranths are famously tough and can grow in
less-than-pristine conditions. Betalains, along with anthocyanins
and other pigments, allow amaranths to handle environmental stress,
acting as antioxidants and repairing cellular damage due to drought,
heat, or intense solar exposure. But the researchers don’t expect
amaranth plantations to start popping up on weedy roadsides across
the U.S., at least not solely for betalain production.
“I don't think amaranth is ever going to be a crop strictly grown
for pigmentation; there aren't many crops like that. But amaranth is
already approved by the FDA for food use, and under those guidelines
could be approved as a natural food colorant,” Riggins says.
“Amaranth is mainly grown commercially for the seeds, often for
gluten-free applications, but there's a lot of biomass wasted from
the seed harvest. Our data suggests the pigment could be a
value-added product down the line.”
Howard adds, “The shift from synthetic ingredients requires a
diverse toolkit of natural options so that the food industry can
match the color hue and stability of synthetic colors at an
effective cost-in-use. Amaranth is an exciting crop that addresses
each of these points — it is a scalable, resilient, antioxidant-rich
crop with impressive biomass yields. Unlike red beets, the current
sole commercial source of betalains, vegetable amaranth also
provides green chlorophylls and yellow carotenoids that provide
additional hues. These added byproducts enable lower costs and
greater sustainability.”
The study extends a longstanding research theme in the College of
ACES that investigates natural food compounds as colorants and
health promoters. For example, as an undergraduate, Howard got
involved in the purple corn project to identify rich sources of
anthocyanin pigments in purple and blue corn varieties. College
faculty, especially those in the Department of Food Science and
Human Nutrition and the Division of Nutritional Sciences, are also
actively pursuing bioactive compounds for human health.
The article, “Amaranth as a natural food colorant source: Survey of
germplasm and optimization of extraction methods for betalain
pigments,” is published in Frontiers in Plant Science [DOI:
10.3389/fpls.2022.932440]. Authors include Howard, Riggins, and
Maria Villamil. The project was funded in part by the USDA’s
Agriculture and Food Research Initiative and the College of ACES.
[Sources: Chance Riggins and Jay
Howard
News writer: Lauren Quinn] |
