A brief review of the science behind the design of healthy and sustainable plant-based foods

Abstract

People are being encouraged to consume more plant-based foods to reduce the negative impacts of the modern food supply on human and global health. The food industry is therefore creating a new generation of plant-based products to meet this demand, including meat, fish, egg, milk, cheese, and yogurt analogs. The main challenge in this area is to simulate the desirable appearance, texture, flavor, mouthfeel, nutrition, and functionality of these products using healthy, affordable, and sustainable plant-derived ingredients, such as lipids, proteins, and carbohydrates. The molecular and physicochemical properties of plant-derived ingredients are very different from those of animal-derived ones. It is therefore critical to understand the fundamental attributes of plant-derived ingredients and how they can be assembled into structures resembling those found in animal products. This short review provides an overview of the current status of the scientific understanding of plant-based foods and highlights areas where further research is required. In particular, it focuses on the chemical, physical, and functional properties of plant ingredients; the processing operations that can be used to convert these ingredients into food products; and the science behind the creation of some common plant-based foods, namely meat, egg, and milk analogs.

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PERSPECTIVE OPEN
A brief review of the science behind the design of healthy and
sustainable plant-based foods
David Julian McClements
1
✉and Lutz Grossmann
1
✉
People are being encouraged to consume more plant-based foods to reduce the negative impacts of the modern food supply on
human and global health. The food industry is therefore creating a new generation of plant-based products to meet this demand,
including meat, fish, egg, milk, cheese, and yogurt analogs. The main challenge in this area is to simulate the desirable appearance,
texture, flavor, mouthfeel, nutrition, and functionality of these products using healthy, affordable, and sustainable plant-derived
ingredients, such as lipids, proteins, and carbohydrates. The molecular and physicochemical properties of plant-derived ingredients
are very different from those of animal-derived ones. It is therefore critical to understand the fundamental attributes of plant-
derived ingredients and how they can be assembled into structures resembling those found in animal products. This short review
provides an overview of the current status of the scientific understanding of plant-based foods and highlights areas where further
research is required. In particular, it focuses on the chemical, physical, and functional properties of plant ingredients; the processing
operations that can be used to convert these ingredients into food products; and the science behind the creation of some common
plant-based foods, namely meat, egg, and milk analogs.
npj Science of Food (2021) 5:17 ; https://doi.org/10.1038/s41538-021-00099-y
INTRODUCTION
The modern food and agricultural industries have produced a
plentiful supply of safe, affordable, convenient, and tasty foods,
contributing to a significant reduction in world hunger and
malnutrition over the past century. But current food production
practices are also linked to the high prevalence of some chronic
diseases, as well as to appreciable environmental damage
1–3
.A
higher quantity and enhanced quality of food are required to feed
a global population that is growing and becoming wealthier
3
. The
production of large quantities of animal products, such as meat,
fish, egg, milk, and their derivatives, has been proposed to be a
major factor contributing to the negative impact of the modern
food supply on global environmental sustainability
1
. Rearing
livestock for food typically leads to more pollution, as well as
greater greenhouse gas emissions, water use, land use, and loss of
biodiversity than growing plants directly for consumption
4
.It
should be noted, however, that there are areas unsuitable for the
production of agricultural crops that are suitable for the raising of
animals as foods. Moreover, some studies have shown that
switching to a more plant-based diet may result in a slight
increase in overall water use and only a modest decrease in overall
cropland use
4
. However, many people have ethical concerns
about confining and slaughtering animals, which is motivating
them to switch to a more plant-based diet
5,6
. Moreover, many
consumers believe a plant-based diet is healthier than an animal-
based one, which is driving changes in their eating behaviors
6
, but
it is important to note that a plant-based diet is not necessarily
better than an omnivore diet from a nutritional perspective
7
.
Animal foods, such as meat, milk, and egg, often contain
micronutrients that are lacking from an entirely plant-based diet,
such as vitamin D, calcium, and zinc. For this reason, plant-based
foods often need to be fortified with these micronutrients.
As a result of these environmental, ethical, and health concerns,
the plant-based food sector is expanding rapidly to meet
consumer demand
8
. This sector includes a range of products
created as alternatives to those normally produced from animals,
including milk, meat, fish, eggs, and products where they are used
as ingredients (Table 1). Each product category is expected to
have its own unique physical, functional, nutritional, and sensory
attributes. The food industry must therefore identify appropriate
combinations of ingredients and manufacturing operations to
economically create these attributes in plant-based foods on a
large scale. As a result, they need knowledge of the molecular and
physicochemical properties of plant-derived ingredients, how they
can be assembled into structures that mimic those found in
animal products, and how these structures influence the
physicochemical and organoleptic properties of the end product.
Ideally, these plant-based products should also be designed to be
healthy, which involves controlling their nutrient profile, digest-
ibility, and bioavailability. In the case of plant proteins, it is
important to ensure that they are able to provide the full
complement of essential amino acids and that they are
digestible
9
. A well-balanced essential amino acid profile can often
be achieved by consuming a mixture of plant proteins from
different sources, such as grains and legumes.
PLANT-BASED INGREDIENTS
Initially, it is important to identify an appropriate blend of plant-
derived ingredients to produce a specific plant-based food, such
as a meat, fish, egg, or milk analog. These ingredients may be
isolated nutrients (such as proteins, carbohydrates, fats, vitamins,
or minerals) or complex whole materials (such as beans, peas, rice,
wheat, mushrooms, etc.). These ingredients have compositions,
structures, and physicochemical properties that are very different
from those found in animal products. One of the major challenges
is therefore to assemble these ingredients into animal product
analogs. Sometimes plant-derived ingredients can be used as-is
(e.g., mushrooms), but in other cases, they may have to be
dissembled into specific structural elements before being
1
Department of Food Science, University of Massachusetts, Amherst, MA, USA. ✉email: mcclements@foodsci.umass.edu; lkgrossmann@umass.edu
www.nature.com/npjscifood
Published in partnership with Beijing Technology and Business University
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reassembled into animal product analogs (e.g., soy proteins). A
brief outline of some of the main plant-derived ingredients used
to form plant-based foods is given here.
Plant-based proteins
Plant proteins are commonly used in plant-based foods because
of their versatile functional attributes, such as their ability to
thicken, gel, emulsify, foam, and hold fluids
9,10
. In addition, they
are an important source of essential amino acids. These proteins
can be derived from various botanical sources, including
soybeans, peas, faba beans, mung beans, lentils, algae, and
microalgae, each with its own unique characteristics (Table 2).
Most plant proteins have globular structures and are often present
as complex multimers consisting of numerous different types of
protein held together by physical and/or chemical bonds (Fig. 1).
The functionality of these proteins depends on their biological
origin, as well as any changes in their association and native states
during isolation and purification. A major challenge in the plant-
based food sector is the lack of plant proteins with consistent
functional attributes. In the future, more research is required to
identify appropriate botanical sources and isolation procedures for
producing reliable functional ingredients. Another major chal-
lenge is to coax plant proteins into structural organizations that
mimic those found in animal products (Fig. 2), thereby leading to
similar physicochemical attributes.
Plant-based carbohydrates
Carbohydrates, such as sugars, oligosaccharides, or polysacchar-
ides, can also be used as functional ingredients to assemble
animal product analogs
11
. Plant-derived carbohydrates exhibit
different molecular, physicochemical, functional, and biological
properties depending on their biological origin and isolation
procedures. These ingredients may be used to provide a variety of
functional attributes in plant-based foods, including sweetness,
thickness, gelling, emulsification, structure formation, stabilization,
and fluid holding
12
. They may also be digestible or indigestible
(i.e., fibers), as well as fermentable or non-fermentable, which
impacts human nutrition and health. It is therefore important to
select carbohydrate ingredients that provide the required quality
and nutritional attributes in the end product. Polysaccharides are
often used in combination with proteins to obtain desirable
textural and sensory properties in plant-based foods via phase
separation and interactive mechanisms
13
.
Plant-based lipids
Plant-based fats and oils can be economically extracted from
various lipid-rich botanical sources, including algae, canola,
coconut, cocoa, corn, flaxseed, olive, palm, safflower, soybean,
and sunflower. For many applications, the ability of the
triacylglycerols to form a 3D network of fat crystals is important,
as it provides desirable textural attributes, such as the plasticity of
butter and spreads (Fig. 3). Moreover, the change in the solid fat
content with temperature plays a critical role in the functionality
of many foods. This is particularly important when trying to mimic
the behavior of animal fats with plant fats. The melting point of
fats increases as the number of carbon atoms in the fatty acid
chains increases or the number of double bonds decreases. The
crystallization characteristics of fats are responsible for many of
the desired quality attributes of animal products, such as butter
spreadability, whipped cream foamability, cheese meltability, and
ice cream hardness. For this reason, it is often important to
simulate the crystallization characteristics of animal fats using
Table 1. Market value of plant-based food products in the United
States (2019), growth over a two-year period (2017–2019), and market
share (2019).
Category Value ($) Growth (%) Share (%)
Milk $2,016,540 14% 40.5%
Meat $939,459 38% 18.9%
Meals $376,972 26% 7.6%
Ice cream and frozen novelty $335,549 34% 6.7%
Creamer $286,662 93% 5.8%
Yogurt $282,502 95% 5.7%
Butter $198,359 15% 4.0%
Cheese $189,099 51% 3.8%
Tofu and tempeh $127,856 15% 2.6%
Ready-to-drink beverages $122,276 39% 2.5%
Condiments, dressings,
and mayo
$63,696 1.4% 1.3%
Dairy spreads, dips, sour cream,
and sauces
$29,513 135% 0.6%
Eggs $9,851 228% 0.2%
$4,978,587 29% 100%
Adapted from Cross (2020)
8
.
The bold values show the total amount in each category.
Table 2. Molecular properties of selected plant and animal proteins.
M
W
(kDa) pI T
m
(°C)
Meat proteins
Collagen 300 5–862–67
Hemoglobin 67 6.8 67
Myoglobin 17 6.8–7.2 79
Actin 43 ~5.2 70–80
Myosin 520 ~5.3 40–50
Sarcoplasmic 20–100 Varies 50–70
Egg proteins
Ovalbumin 45 4.6 85
Conalbumin 80 6.6 63
Ovomucoid 28 3.9 70
Ovoglobulins 30–45 5.5–5.8 93
Lysozyme 14.6 10.7 78
Milk proteins
α
S1
−casein 23.6 4.6 –
α
S2
−casein 25.2 4.6 –
β−casein 24.0 4.6 –
κ−casein 19.6 4.6 –
β−lactoglobulin 18.4 5.4 72
α−lactalbumin 14.2 4.4 35 and 64*
BSA 66.3 4.9 64
Plant proteins
Soy protein 150–380 4.5–5.0 80–93
Pea protein 50–360 4.5 75–79
Lentil protein 15–82 4.5 120
Chickpea protein 15–82 4.5 90
Lupin protein 150–216 4.5 79–101
Canola protein 14–59 4.5 84–102
Corn zein 14–27 6.4 89
*The lower and higher temperatures for alpha-lactalbumin are for the apo-
(calcium free) and holo- (calcium bound) forms, respectively.
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plant-derived ones. This is often challenging because plant-
derived fats contain more unsaturated fatty acids than animal fats
and so tend to be more fluid-like at ambient temperatures. This
problem can be overcome by increasing the degree of saturation
of these fats using hydrogenation, but this may have adverse
nutritional effects. As a result, food manufacturers often use
naturally occurring high-melting plant-derived fats in their
products, such as cocoa butter and coconut oil, but these also
have high degrees of saturation that may have adverse health
effects, such as an increased risk of heart disease
7
.
The type of fatty acids present in plant-derived fats and oils also
influences their nutritional profile and oxidative stability. Fats and
oils containing high levels of polyunsaturated fatty acids (PUFAs),
particularly omega-3 ones (like flaxseed or algae oils), have been
claimed to have beneficial health effects, such as the ability to
reduce heart and brain diseases
14,15
. Although further studies are
required to substantiate these claims using randomized clinical
trials and meta-analysis. These fats may be used as an alternative
to fish oils, which are rich in omega-3 PUFAs. Even so, it is
important to prevent these PUFAs from oxidizing during storage
and processing since this leads to the generation of undesirable
off-flavors and toxic reaction products
16,17
. This may be achieved
using numerous strategies including controlling temperature,
oxygen, and light levels; reducing pro-oxidant contamination;
incorporating antioxidants; utilizing chelating agents, or structur-
ing approaches
18–20
. Utilization of these approaches will be
important for creating the next generation of nutritionally-
fortified plant-based foods.
Other additives
The creation of high-quality plant-based foods also requires the
utilization of various other additives, including colors, flavors,
buffers, preservatives, and crosslinking agents
21
. Ideally, these
ingredients should be natural botanical ingredients, like natural
pigments (e.g., carotenoids, anthocyanins, and curcuminoids) or
preservatives (e.g., essential oils or antimicrobial peptides).
THE SCIENCE BEHIND PLANT-BASED FOODS
In general, plant-derived ingredients are being used to create a
wide range of food products to replace animal-based ones (such
as meat, fish, eggs, and milk) or that normally require animal
ingredients as key components (such as cheese, dressings, sauces,
spreads, and yogurts) (Table 1). Here, we give a brief overview of
the science and technology behind the formulation of the main
categories of plant-based alternatives: meat, milk, and egg.
Plant-based meat analogs
The recent commercial success of plant-based meat products,
such as those produced by Beyond Meat and Impossible Foods,
has had a profound impact on the modern food industry
21
.
Indeed, the market for plant-based meats in the US was nearly
$940 million in 2019, with a 38% increase from two years before
(Table 1).
The food industry has been highly successful in producing high-
quality analogs of comminuted meat products, such as burgers,
sausages, nuggets, and ground meat since texturized vegetable
proteins (TVPs) can be used to simulate their structures. However,
it has proved much more challenging to create products that
accurately mimic the properties of whole muscle tissue, which
consists of muscle fibers, connective tissue, and adipose tissue
organized into complex hierarchical structures (Fig. 2). The
structural arrangement of these tissues plays a critical role in
determining the physicochemical and sensory attributes of real
meat products
22
.
The production of high-quality plant-based whole muscle
analogs requires selecting the most appropriate ingredients and
processing operations to simulate muscle fiber, connective, and
adipose tissue (Fig. 4). Here, we highlight some of the key factors
that should be considered when designing meat analogs that
faithfully simulate the attributes of real meat. More details about
this topic can be found in a number of recent review articles
23–25
.
Ideally, meat analogs should reliably mimic the desirable
Fig. 1 Globular plant proteins are often present as multimers linked together. The 3D view is for the soy glycinin hexamer, which is from
the Protein Data Bank 1FXZ: Adachi, M., Takenaka, Y., Gidamis, A. B., Mikami, B., Utsumi, S. Crystal structure of soybean proglycinin A1aB1b
homotrimer. J. Mol. Biol. 305, 291–305 (2001). doi: 10.1006/jmbi.2000.4310.
D.J. McClements and L. Grossmann
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characteristics of real meat products before, after, and during
cooking. Meat analogs are mainly constructed from plant-derived
macronutrients (fats, proteins, and polysaccharides), but also
contain micronutrients and other additives, such as vitamins,
minerals, colors, flavorings, binders, and preservatives
21
. The
ingredients and processing operations used to produce these
analogs must be optimized for each specific meat product being
mimicked.
Appearance. The opaque nature of real meat can be simulated
by including particles or fibers with dimensions (200–2000 nm)
that scatter light strongly. The surface sheen of meat can be
simulated by controlling the surface roughness and wetness of
meat analogs. The analogs should have a wet smooth surface
before heating leading to specular reflectance and a shiny look,
but a rough dry surface after heating leading to diffuse reflectance
and a matt look. The color of real meat is simulated by
incorporating natural pigments that selectively absorb light at
appropriate wavelengths. For instance, a beef analog should be
pinky-red before cooking and brown after cooking. For some
products, such as microwavable ones, it is only required to
reproduce the brownish color of the cooked product.
Food companies have used various strategies to simulate the
color of real meat in their plant-based alternatives. Beyond Meat
TM
uses an extract from beet juice extract containing betalain (a
natural pigment) to recreate the desirable color of meat. The
betalain undergoes a chemical transformation when heated,
causing it to turn from reddish-violet to orangey-yellow
26,27
.
Impossible Foods
TM
uses a plant-based heme protein, leghemo-
globin, in their products. In principle, leghemoglobin can be
extracted from the roots of soybeans, but in practice, it is more
economically viable to generate it by microbial fermentation.
Other natural pigments can be used either alone or in
combination to create desirable meat-like color characteristics
28
.
Texture. It is possible to simulate the textural attributes of
comminuted meat products (sausages, burgers, and nuggets)
fairly accurately using TVPs, which has led to highly successful
commercial plant-based products such as those from Impossible
Foods
TM
and Beyond Meat
TM 25
. It is much more challenging to
Fig. 2 The muscles in meat have a complex hierarchical structure. The image of the meat structure used is from: OpenStax, CC BY 4.0.
https://creativecommons.org/licenses/by/4.0, via Wikimedia Commons.
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simulate the delicate texture and mouthfeel of whole muscle
products, like beef steaks, chicken breast, or pork chops because
of their complex hierarchical structures (Fig. 2). A range of
scientific and technological approaches are being explored for
their potential in creating structures from plant-derived ingredi-
ents that simulate those found in real meat, with the ultimate aim
of accurately mimicking their texture and mouthfeel
29
. These
approaches can be grouped into two different categories that may
be used separately or combined: physicochemical and processing
approaches.
Physicochemical approaches are based on controlling the
molecular interactions and organization of plant-derived biopoly-
mers to create meat-like structures
24,30
. Typically, a mixture of
plant proteins and polysaccharides is used for this purpose.
Appropriate mixtures of biopolymers can be made to phase
separate by controlling the ingredient types and concentrations,
as well as solution properties such as pH, mineral composition,
and temperature (Fig. 4). The two main phase separation
approaches involved are thermodynamic incompatibility and
coacervation, which are based on inducing either repulsive or
attractive interactions between the two types of biopolymers,
respectively. This leads to the formation of a water-in-water (W/W)
emulsion that contains two aqueous phases with different
compositions. A mild shear force is then applied to the phase-
separated biopolymer solution, resulting in the generation of
fiber-like structures. These structures can then be locked into
place by adding a suitable gelling agent or by changing the
temperature (cooling or heating). This approach can be used to
form fibrous structures that simulate some of the characteristics of
those found in real meat, thereby leading to some similar
physicochemical attributes (Fig. 5).
Plant-derived biopolymers can also be used to form meat-like
structures using certain kinds of mechanical processing devices,
such as extruders or high shear cells. As an example, protein-water
mixtures are fed into an extrusion device, which mixes and shears
them under high pressure and then extrudes them through a
shaped die to form meat-like structures and textures
29,31,32
.
Alternatively, these structures and textures can be formed by
placing a mixture of proteins and polysaccharides into a specially
designed cone-in-cone shear cell, which applies strong shear
forces to the mixture by rotating one or both of the plates at a
high speed. The biopolymer mixture can also be heated within the
cell during the shearing process to promote protein unfolding and
aggregation. As a result, the proteins organize into fiber-like
structures that somewhat resemble the structure of meat fibers
13
.
Extrusion methods are currently the most common processing
method to create meat-like textures in commercial products, but
the shear cell is also finding increasing use.
Fig. 3 This figure shows the change in SFC with temperature (top), as well as the different crystal contents in lipids with temperature
(bottom). The SFC-temperature profile of an edible fat determines its functionality.
D.J. McClements and L. Grossmann
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Cooking loss. An important attribute of real meat products is
their ability to retain/lose fluids during cooking, as their fluid
content impacts their look, feel, mouthfeel, and cooking proper-
ties. It is therefore important that meat analogs simulate the fluid-
holding properties of real meat. Researchers have used funda-
mental physical chemistry models to identify the key factors
impacting the fluid-holding properties of meat analogs: the
interactions between the solvent and biopolymer molecules; the
elastic modulus of the gel network formed by the biopolymer
molecules; and, the osmotic pressure generated due to a
concentration imbalance of mineral ions inside and outside the
gel network
33
. The fluid holding properties of meat analogs can
therefore be manipulated by altering biopolymer type, concentra-
tion, and crosslinking. In addition, the incorporation of poly-
saccharides can be used to improve the fluid holding properties
34
.
Flavor. Hundreds of aromatic molecules have been reported in
meat products, but only some of these play a critical role in
determining their characteristic flavor profiles
35
. The aroma profile
depends on the type of meat and cooking method used. In
cooked meat, the aromatic molecules are mainly the result of
complex chemical reactions involving protein, carbohydrate, and
lipid molecules, particularly Maillard and oxidation reactions. The
taste of cooked meat depends on the balance of non-volatile
molecules present that interact with umami, salt, sweet, bitter, and
sour receptors in the mouth. These molecules may be present
within the original raw animal flesh or they may be produced as a
result of the cooking processes used.
Information about the most important flavor constituents
within real meat products can be used to identify plant-based
alternatives that provide meaty flavors in meat analogs. Impos-
sible Foods uses soy leghemoglobin produced by fermentation
processes to create “meaty”notes in their commercial meat
analogs. The heme iron in leghemoglobin is exposed during
cooking, thereby promoting oxidative reactions that generate
aromatic compounds similar to those produced in real meat
36
.
Mycoproteins, which are also produced using fermentation
processes, are being utilized for their ability to produce meat-
like aromas, tastes, and textures
37
. Algae and microalgae are being
used in plant-based fish and other marine products because they
provide seafood-like flavors
37
. Plant-derived materials can be used
as precursors to form meaty flavors by carrying out controlled
Maillard and oxidation reactions
38
. Research is also being carried
out to reduce the undesirable flavors found in some plant-derived
ingredients, e.g., the beany, earthy, astringent, or vegetative notes
associated with chickpea, mung bean, or pea proteins
38
.
Nutritional profile. A major challenge when developing plant-
based meat analogs is to match the nutritional profile of the
original product. Meats contain high levels of protein, as well as
essential micronutrients, such as zinc, iron, and vitamin B.
Moreover, these micronutrients are often present in a highly
bioavailable form within animal products. Consequently, it is
important to design plant-based meat analogs that are enriched
with bioavailable forms of these micronutrients. This can often be
achieved using advanced encapsulation technologies, such as
emulsions or nanoemulsions
39
.
Plant-based milk analogs
Plant-based milk analogs are currently the most commonly
consumed plant-based food products, contributing over 40% of
the market sales in this sector (Table 1)
8
. The raw materials,
processing methods, physicochemical properties, sensory attri-
butes, and nutritional profiles of milk analogs products have been
reviewed in a number of recent articles
8,40–43
. For this reason, only
Fig. 4 Soft matter physics is used to create meat-like structures from plant ingredients. The authors thank Xiaoyan Hu and Cheryl Chung
(UMASS) for providing the images of adipose tissue and plant-based muscle fibers. The image of the muscle fibers is by Nephron and is
licensed under CC BY-SA 3.0. The image of the raw beef steak is by Jellaluna and is licensed under CC BY 2.0.
D.J. McClements and L. Grossmann
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a short overview of these products is given here, with an emphasis
on their fundamental properties.
Raw materials and production. Milk analogs are complex colloidal
dispersions comprised of various kinds of particles, including oil
bodies, fat droplets, protein aggregates, plant tissue fragments,
and/or insoluble calcium carbonate particles, dispersed in an
aqueous medium containing soluble proteins, polysaccharides,
sugars, and salts
41
. Creating high-quality milk analogs, therefore,
requires basic knowledge of colloid and interface science, such as
particle reduction technologies, light scattering theory, and
particle instability mechanisms. Milk analogs are typically created
using two approaches: (i) plant tissue disruption; (ii) homogeniza-
tion (Fig. 5)
41
. The first approach involves unit operations such as
soaking, mechanical disruption, enzymatic hydrolysis, separation,
formulation, homogenization, and thermal treatment to break
down plant materials (such as soybeans, flaxseeds, almonds, or
coconut flesh) into small particles. The second approach involves
blending isolated plant-based ingredients (e.g., oils, emulsifiers,
and thickeners) with water followed by homogenization and
thermal treatment to produce an emulsion containing small
droplets
41
. These processes must be carefully controlled to create
stable milk analogs with the appropriate physicochemical,
sensory, and functional attributes. Gravitational separation and
aggregation can be inhibited by ensuring all the particles are
sufficiently small (<500 nm), which can be achieved using
appropriate chemical, enzymatic or mechanical size-reduction
methods. Plant-based stabilizers, such as emulsifiers or thickening
agents, may also be included to improve emulsion formation and
stability. Plant-based emulsifiers include surface-active proteins
(e.g., soy, pea, fava bean, and lentil proteins), polysaccharides (e.g.,
modified starches), phospholipids (e.g., soy and sunflower
lecithin), or surfactants (e.g., quillaja and tea saponins)
44
. Plant-
based thickening agents may be added to modify the textural
characteristics or inhibit particle separation, which is usually
polysaccharides like pectin, locust bean gum, gellan gum, starch,
methylcellulose, carrageenan, and alginate
45
. The ingredients and
processing operations used are optimized to create milk analogs
that mimic the desirable properties and functional performance of
cow’s milk
41
. Milk analogs may also be fortified with micronu-
trients to provide nutrients that may be deficient in plant-based
diets, such as vitamin D, vitamin B
12
, and calcium
40
.
Appearance and sensory. A creamy appearance can be achieved
in milk analogs by controlling the concentration and size of the
colloidal particles they contain, such as oil bodies, fat droplets, and
tissue fragments. Their lightness increases with increasing particle
concentration and when the particles have similar dimensions to
light waves (380–780 nm). The inherent color of milk analogs
depends on the type and concentration of natural pigments they
contain
46
. To achieve a desirable appearance it is often necessary
to add or remove certain natural pigments.
The sensory attributes of cow’s milk are difficult to recreate
because it has a bland but characteristic flavor profile, with over
100 volatile compounds typically present
47,48
. In contrast, milk
analogs contain flavors arising from the plant’s raw materials, as
well as generated during processing and storage. For instance,
soymilks often have a beany flavor, whereas hazelnut milk has a
nutty flavor
43
. Moreover, phytochemicals such as phenols and
glucosinolates may introduce off-flavors, such as bitter, earthy, or
vegetative notes
38
. Researchers are therefore developing new
plant breeds and new processing methods to reduce off-flavors in
milk analogs, including blanching and fermentation
49
.
Nutritional profile. The nutritional profile of plant-based milk
products is often inferior to that of real milk
40
. Cow’s milk naturally
contains high levels of vitamin A and calcium, which may be
lacking in a plant-based diet. This problem can be overcome by
using advanced encapsulation technologies to fortify plant-based
milk with bioavailable forms of these micronutrients
40
.
Fig. 5 Plant-based milk can be produced by fragmentation or homogenization methods. Image of soybeans from CSIRO (CC BY 3.0). Image
of “Soy Milk”by Kjokkenutstyr.net is licensed under CC BY-SA 2.0 (www.kjokkenutstyr.net).
D.J. McClements and L. Grossmann
7
Published in partnership with Beijing Technology and Business University npj Science of Food (2021) 17

Plant-based egg analogs
Whole hen’s eggs are mainly comprised of water (75%), proteins
(12%), and lipids (12%), and contain a diverse range of
constituents that contribute to their various functional applica-
tions in foods, such as emulsification, foaming, water holding, and
gelation
50
. As a result, they are versatile ingredients that can be
used in many different foods, including alone (boiled, scrambled,
poached, or fried eggs) or as a critical part of other foods (like
mayonnaise, dressings, baked goods, and desserts). Ideally, plant-
based egg analogs should simulate these desirable physiochem-
ical and functional attributes. One of the most important
functional attributes is the ability to undergo a sol–gel transition
when heated under similar cooking conditions as used for real
eggs. Ideally, the globular plant proteins used in egg analogs
should therefore have a denaturation temperature in the same
range as real egg proteins (i.e., around 63–93 °C), but many plant
proteins only denature at higher temperatures (e.g., around 90 °C
for soy glycinin
51
). As a result, higher temperatures or longer
heating times are often required to achieve the same structure
formation and textural attributes as real eggs. Instrumental
methods like differential scanning calorimetry and dynamic shear
rheometry can be used to provide information about protein
denaturation and gelation temperatures. Typically, it is important
that the plant proteins used are in a native state prior to heating,
which means their isolation conditions must be carefully
controlled. The nature of the gels formed depends on protein
type (e.g., soybean, pea, chickpea, bean, and sunflower), protein
concentration, and environmental conditions (e.g., ionic strength,
pH, and thermal history), which should therefore all be carefully
controlled
52
. In some applications, the plant-based ingredients in
egg analogs should also exhibit good emulsifying properties, such
as in mayonnaise or dressings. Plant proteins or phospholipids
used for this purpose should typically be soluble in water, capable
of adsorbing to oil droplet surfaces, and able to stabilize oil
droplets from aggregation. In some cases, other plant-based
ingredients may also be required to prevent destabilization of the
product, such as thickening agents that inhibit gravitational
separation. The yellowish appearance of egg yolks may be
achieved by adding natural pigments (such as curcumin or
carotenoids), while an appropriate flavor profile may be achieved
by adding natural flavors, herbs, or spices.
Many different egg analogs have been developed over the
years, with JUST Egg
TM
(www.ju.st) being one of the most
successful recently. Two products are currently on the market
from this company: (i) fluid eggs intended to prepare scrambled
eggs or omelets; (ii) frozen egg slices that can be heated and used
in breakfast sandwiches. Mung bean protein and emulsified
canola oil are two of the main components of these products. The
proteins unfold and aggregate during cooking leading to a gel-like
texture. The canola oil droplets contribute to the opaque
appearance, textural attributes, flavor profile, and mouthfeel of
the final product. These products also contain transglutaminase,
an enzyme that crosslinks the proteins, thereby increasing the gel
strength and water holding capacity so as to better mimic real
egg
53
. The yellowish color of eggs is mimicked in these products
by adding turmeric, which contains curcumin. Other functional
ingredients are also added to more closely simulate the properties
of real eggs, including thickeners/stabilizers (e.g., corn starch and
gellan gum), seasonings (e.g., garlic powder, onion powder, sugar,
and salt), buffering salts (e.g., bicarbonates, citrates, or phos-
phates), and preservatives (e.g., nisin). In the future, more research
is still required to improve the functional versatility of egg analogs
and to enhance their nutritional profiles.
Nutritional profile. The nutritional profile of plant-based eggs is
often worse than that of real hen’s eggs. Hen’s eggs naturally
contain a variety of vitamins and minerals that are not commonly
found in a plant-based diet. For this reason, it is often important to
fortify plant-based egg products with bioavailable forms of these
micronutrients, which often require the utilization of advanced
encapsulation technologies.
CONCLUSIONS AND FUTURE DIRECTIONS
Recent reports suggest that human and global health would be
greatly improved by replacing animal-based foods (such as meat,
fish, eggs, milk, and their products) with plant-based alternatives.
This transition would be facilitated by the availability of more
plant-based foods that are affordable, convenient, sustainable,
nutritious, and tasty. Consumers would then find it easier to
change their dietary habits and adopt a more healthy and
sustainable diet. There are, however, various hurdles that need to
be addressed to achieve this goal:
●Consumer-based hurdles: Improved knowledge of the behavior
of consumers is needed to create effective approaches to
encourage them to try, like, and adopt plant-based foods.
There has already been a considerable amount of consumer
research carried out for certain kinds of plant-based pro-
ducts
54–56
. However, more research is required to develop
effective materials to educate consumers about the potential
benefits and drawbacks of consuming plant-based foods so
they can make informed choices.
●Technological-based hurdles: The creation of plant-based foods
is being held back by a lack of high-quality plant-derived
ingredients, particularly proteins, as well as large-scale
manufacturing processes to convert these ingredients into
desirable end products. In particular, it is still challenging to
create analogs of whole muscle meat, fish, yogurt, and cheese
because of their complex structural hierarchies. Consequently,
more research is required to understand the relationship
between the structure and properties of plant-based ingre-
dients and their ability to form high-quality meat, fish, egg, or
dairy analogs people want to consume.
●Commercial-based hurdles: The commercialization of plant-
based foods is being held back by a lack of knowledge about
the relative advantages and disadvantages of different plant-
derived ingredients and manufacturing processes, as well as
of safety concerns (such as allergenicity), regulations in
different countries, and supply chain issues. Increased knowl-
edge about these issues would help companies to successfully
enter the plant-based food market.
●Social-based and economic-based hurdles: Changes in govern-
ment policies, such as taxation, incentives, and educational
programs, would facilitate the transition to a more plant-
based diet. However, improved knowledge about the social,
economic, environmental, and health implications of replacing
animal products with plant-based ones is still required to craft
and implement these policies.
In the future, it will be important for governments, industries,
and non-profit organizations to support efforts to obtain this
information, thereby facilitating a more rapid transition to a
healthy and sustainable plant-based diet. It should also be noted
that many plant-based foods are highly processed and contain
numerous additives, which is undesirable to many consumers.
Consequently, there is a need for more research on the
development of processed plant-based foods that contain fewer
ingredients and involve less processing. In addition, it is often
assumed that plant-based foods are healthier than animal-based
ones. But this is often not the case. More research is required to
ensure that plant-based foods are carefully designed to ensure
that they have beneficial nutrient profiles and that the nutrients
are in a bioavailable form.
D.J. McClements and L. Grossmann
8
npj Science of Food (2021) 17 Published in partnership with Beijing Technology and Business University

DATA AVAILABILITY
Data sharing not applicable. This is a review article and no new datasets were
generated or analyzed during this study.
Received: 18 January 2021; Accepted: 13 May 2021;
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ACKNOWLEDGEMENTS
This work was supported by the USDA National Institute of Food and Agriculture,
Agricultural and Food Research Initiative Competitive Program, grant number: 2020-
03921. It was also supported by funding provided by the Good Food Institute.
AUTHOR CONTRIBUTIONS
D.J.M. planned the article. D.J.M. and L.G. then wrote and edited the various sections
of the article. D.J.M. and L.G. are considered co-first authors.
COMPETING INTERESTS
The authors declare no competing interests.
ADDITIONAL INFORMATION
Correspondence and requests for materials should be addressed to D.J.M. or L.G.
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npj Science of Food (2021) 17 Published in partnership with Beijing Technology and Business University