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Plant-based proteins: An alternative to synthetic emulsifiers

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May 2018, Vol. 29 (5)
As consumers become more aware of how their
diets aect their health and the environment, they
are changing their dietary habits and trying to make
healthier and more sustainable choices. A few of the
statements they look for on food labels include “all
natural”, “clean-label”, “earth-friendly”, “pure”, and
plant-based.” Consequently, food companies feel the
need to make a shi and replace synthec or ani-
mal-based ingredients with natural and sustainable
alternaves. Meanwhile, media propaganda advis-
ing consumers “not to eat it if you cannot pronounce
it,” makes consumers even more skepcal of ingre-
dients with complex names they do not recognize.
Hence, to stay strong in the food market, food pro-
ducers are trying to use simpler, easier-to-understand
ingredients. Some companies even woo consumers by
giving their ingredients unique names that sound more
natural, such as “evaporated sugar cane juice” instead
of “sugar.”
Meanwhile, the funconal food market is growing due to the higher
expectaons consumers have for food products. When a millennial eats
a snack, she/he expects not only to sasfy hunger, but also to receive a
benecial health eect. Unfortunately, most of the ingredients that give
health benets are not very stable or compable with food matrixes.
Therefore, food emulsions are becoming more popular in the food
industry, because they can overcome solubility and degradaon issues
and increase the bioavailability of nutrients.
Plant-based proteins:
an alternave
to synthec emulsiers
Cansu Ekin Gumus
• Food companies are trying to nd
natural alternaves to synthec
emulsiers, and plant-based proteins
are promising opons.
• Legume proteins were shown to have
emulsion formaon and stability
characteriscs and lipid oxidaon rates
similar to those of emulsions stabilized
by dairy proteins.
• Digesbility is not an issue when plant-
based proteins are used as emulsiers.
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May 2018, Vol. 29 (5)
15
Emulsiers, compounds that have both hydrophilic and hydro-
phobic parts, have two main funcons: to facilitate emulsi-
caon and to keep emulsions stable over their shelf life. Some
common emulsiers used in the food industry can be pro-
teins (e.g., whey protein), polysaccharides (e.g., gum arabic),
phospholipids (e.g., lecithin), and synthec emulsiers (e.g.,
Tweens).
Synthec emulsiers can be tailored for specic needs and
can be more ecient than natural alternaves in forming an
emulsion and keeping it stable. However, as consumers seek
natural alternaves, plant-based emulsiers (pea, lenl, and
faba bean proteins) were invesgated and shown to have sim-
ilar emulsion formaon and stability characteriscs as those
stabilized by dairy-proteins. In general, protein-coated droplets
tend to become unstable with pH uctuaons and therefore
must be mixed with other emulsiers, such as polysaccharides
to ensure stability.
DIGESTION AND BIOAVAILABILITY
It is important for the protecve layer encapsulang a
bioacve to be digested in the human gastrointesnal
tract so the funconal ingredients can be released in the
small intesne and adsorbed by the body. The type of
emulsier aects the digesbility of the oil droplets and
the bioavailability of the bioacve compounds that are
encapsulated. Small oil droplets, which can be formed
with more ecient emulsiers, can be digested faster and
enhance bioavailability. In addion, the state of the droplets
prior to entering the small intesne ( i.e., in the stomach)
aects the free-fay-acid (FFA) release rate. The thickness
of the protecve layer around the droplet core also aects
digesbility and can sterically prevent lipase from acng on the
To highlight the high protein content, sustainable pro-
ducon, high availability, and low-cost of legumes, the United
Naons named 2016 “the year of pulses.” Recent interest in
nding natural alternaves to animal-based or synthec emul-
siers has since led researchers to focus on plant-based emul-
siers. Among these, pulse proteins are of specic interest due
to the above-menoned advantages.
EMULSION FORMATION AND STABILITY
Emulsions consist of a liquid phase dispersed in another liq-
uid. Many foods come in emulsion form, such as mayon-
naise, soups, salad dressings, milk, sauces, and ice cream.
PROTEINS/EMULSIONS
Flocculaon
Metastable
Emulsion
Coalescence
Gravitaonal
Separaon
Phase
Separaon
FIG. 1. Emulsions may become physically unstable through vari-
ous physicochemical processes. (McClements and Gumus, 2016:
hps://doi.org/10.1016/j.cis.2016.03.002)
16
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May 2018, Vol. 29 (5)
droplet and cause slower digeson rates. For these reasons,
protein-coated droplets were shown to aggregate and hence
result in slower digeson in the small intesne, whereas
synthec-emulsier-coated droplets were more stable against
droplet aggregaon in the stomach and resulted in faster FFA
release in the small intesne.
Although plant-based proteins were reported to have
lower digesbility, when used as emulsiers they were
digested at the same rate as commonly used animal-based
emulsiers such as whey protein. Therefore, digesbility is not
an issue when plant-based proteins are used as emulsiers.
LIPID OXIDATION
Lipid oxidaon can impair product quality, decrease nutrional
value, and lead to the formaon of potenally toxic prod-
ucts. The emulsier type is a factor that aects lipid oxidaon.
In cases where an emulsier is suscepble to oxidaon itself
(e.g., phospholipid), the rate of lipid oxidaon was found to be
slower than for synthec emulsier-stabilized emulsions.
Metal-catalyzed decomposion of lipid hydroperoxides is
the leading pathway of lipid oxidaon in emulsions. Emulsiers
can inhibit lipid oxidaon by forming a steric barrier between
the oil droplets and reacve species, such as metal ions. On
the other hand, some emulsiers, such as several proteins, can
bind metals and cause a close proximaon between the oil
droplets and metal ions and promote lipid oxidaon. However,
when there is excess protein in the aqueous phase, the addi-
onal protein will protect the oil droplets from lipid oxidaon
by binding the metal ions in the aqueous phase and prevent-
ing their contact with the oil droplets. The pH of an emulsion
changes the protein’s ability to inhibit or promote lipid oxi-
daon. Below their isoelectric points, proteins are posively
charged, which would repel the posively charged metal ions
from the droplet surface when they are used as emulsiers
and prevent lipid oxidaon. Therefore, the concentraon of
unadsorbed and adsorbed protein and matrix pH are two fac-
tors impacng lipid oxidaon. Pulse-protein-stabilized emul-
sions showed lipid oxidaon rates similar to those of whey
protein-stabilized emulsions. This suggests that they could be
used to replace such animal-based emulsiers.
In summary, the emulsifying capabilies and digesbility
of plant-based emulsiers make them good alternaves to syn-
thec emulsiers. However, more research is needed to under-
stand how other aspects, such as sensory characteriscs, could
aect commercializaon. Pulse proteins, for instance, gave the
emulsion samples a highly beany smell, and this might need to
be masked.
Cansu Gumus received her PhD degree in Food
Science from the University of Massachuses
Amherst in May 2017. Part of her doctoral
research at the Food Colloids and Biopolymers
Laboratory under the advising of David Julius
McClements compared the ulizaon of pulse
proteins to form emulsions with commonly used
whey protein. She now works as a laboratory
expert at the Scienc and Technical Applicaon and Research
Center at Hit University in Çorum Turkey. She can be contacted
at cansu.e.gumus@gmail.com.
Further reading
1. Arancibia, et al., “Comparing the eecveness of
natural and synthec emulsiers on oxidave and
physical stability of avocado-oil-based nanoemulsions,”
Innov. Food Sci. Emerg, Technol. 44: 159–166, 2017.
2. McClements and Gumus, “Natural emulsiers—
biosurfactants, phospholipids, biopolymers, and colloidal
parcles: molecular and physicochemical basis of
funconal performance,” Adv. Colloid Interface Sci. 234:
3–26, 2016.
3. Bouyer, et al., “Proteins, polysaccharides, and their
complexes used as stabilizers for emulsions: alternaves
to synthec surfactants in the pharmaceucal eld?” Int.
J. Pharm. 436: 359–378, 2012.
4. Zhang, et al. “Enhancing nutraceucal bioavailability
from raw and cooked vegetables using excipient
emulsions: inuence of lipid type on carotenoid
bioaccessibility from carrots,” J. Agric. Food Chem. 63:
10508–10517, 2015.
0
20
40
60
80
100
0 20 40 60 80 100 120
FFA Released (%)
Digeson Time (min)
Caseinate
Lactoferrin
Tween 80
FIG. 2. The type of emulsier aects free-fay-acid release in
the small intesne. (Zhang, et al., 2015: hp://pubs.acs.org/
doi/10.1021/acs.jafc.5b04691)
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Food industries search for replace synthetic surfactant with natural ingredients, but emulsifier type has an impact on lipid oxidation and stability of emulsions. The aim of the study was to evaluate the emulsifier type and concentration effect on avocado oil-based nanoemulsion development, specifically on physical and oxidative stability. O/W nanoemulsions were prepared with 10% avocado oil using natural (lecithin) and synthetic (Tween 80) emulsifiers at different concentrations (2.5–10%). Results showed that nanoemulsions exhibited anionic (Z-potential: − 26 to − 59 mV) lipid droplets with particle size between 103 and 249 nm. Emulsifier type and concentration affected physical stability, being the most stable at 7.5–10% Tween 80 (15 days) and 7.5–10% lecithin (10 days). Meanwhile, emulsifier concentration affected oxidative stability of nanoemulsions, being the most unstable at 2.5% Tween 80 and 10% lecithin. Finally, although Tween 80 was more effective than lecithin, it also could be used to develop natural nanoemulsions with good physical properties.
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There is increasing consumer pressure for commercial products that are more natural, sustainable, and environmentally friendly, including foods, cosmetics, detergents, and personal care products. Industry has responded by trying to identify natural alternatives to synthetic functional ingredients within these products. The focus of this review article is on the replacement of synthetic surfactants with natural emulsifiers, such as amphiphilic proteins, polysaccharides, biosurfactants, phospholipids, and bioparticles. In particular, the physicochemical basis of emulsion formation and stabilization by natural emulsifiers is discussed, and the benefits and limitations of different natural emulsifiers are compared. Surface-active polysaccharides typically have to be used at relatively high levels to produce small droplets, but the droplets formed are highly resistant to environmental changes. Conversely, surface-active proteins are typically utilized at low levels, but the droplets formed are highly sensitive to changes in pH, ionic strength, and temperature. Certain phospholipids are capable of producing small oil droplets during homogenization, but again the droplets formed are highly sensitive to changes in environmental conditions. Biosurfactants (saponins) can be utilized at low levels to form fine oil droplets that remain stable over a range of environmental conditions. Some nature-derived nanoparticles (e.g., cellulose, chitosan, and starch) are effective at stabilizing emulsions containing relatively large oil droplets. Future research is encouraged to identify, isolate, purify, and characterize new types of natural emulsifier, and to test their efficacy in food, cosmetic, detergent, personal care, and other products.
Natural emulsifiersbiosurfactants, phospholipids, biopolymers, and colloidal particles: molecular and physicochemical basis of functional performance
  • Arancibia
Arancibia, et al., "Comparing the effectiveness of natural and synthetic emulsifiers on oxidative and physical stability of avocado-oil-based nanoemulsions," Innov. Food Sci. Emerg, Technol. 44: 159-166, 2017. 2. McClements and Gumus, "Natural emulsifiersbiosurfactants, phospholipids, biopolymers, and colloidal particles: molecular and physicochemical basis of functional performance," Adv. Colloid Interface Sci. 234: 3-26, 2016.