*Nano- and Microencapsulation - Techniques and Applications*

their functional groups possess the ability to protect, reverse binding, and interact with numerous bioactive compounds. Nowadays, two sources of proteins; plant proteins such as soy, pulses, and cereals proteins and animal proteins such as bovine serum albumin, casein and whey proteins are widely used as encapsulating agents in micro- and nanoencapsulation techniques. Proteins are employed to encapsulate solids and liquids including oils. Their ability to encapsulate oils depends on their capacity to adsorb at the interface and form stable emulsions. The following factors affect their emulsifying properties [93]:

• Preparation methods of protein compounds

*DOI: http://dx.doi.org/10.5772/intechopen.95402*

*3.1.3 Plant proteins*

*3.1.3.1 Soy proteins*

*3.1.3.2 Cereal proteins*

*3.1.3.3 Maize (Zein) protein*

**73**

• Environmental conditions include pH of solvent and ionic strength

*Natural Polymers in Micro- and Nanoencapsulation for Therapeutic and Diagnostic…*

in combination with either another protein or polysaccharides which occurs through different possible interactions (such as covalent, electrostatic, H-bonding, hydrophobic, van der Waals, and disulfide interactions) for delivery of various bioactive compounds (**Figure 7**) [94]. Different polysaccharides can be used to fabricate bilayer on the oil droplets surface with protein compounds to increase the physical stability of both emulsion and the interfacial modifying properties [95].

Protein ingredients have been vastly used as good encapsulating agents alone or

Plant proteins have different types such as soy proteins, cereals proteins (e.g., zein, wheat, and barley proteins), and pulses proteins (e.g., pea, chickpea, and lentil proteins).

Soy proteins are globular proteins and are considered as one of the most important food proteins that are applied significantly in human diets because they have good nutritional values, health-benefiting effects, and high functionalities. They are mainly composed of albumins and globulins which represent around 50–90% of total seed proteins. They are divided according to their sedimentation coefficients into four fractions: 2S, 7S, 11S, and 15S fractions. The 2S fraction corresponds to albumins, while the globulins are present in 7S, 11S, and 15S fractions. Also, glycinin (named as 11S or SG, and Mwt 350 kDa) and β-conglycinin (named as 7S or SC, and Mwt of about 70 kDa are two globulin forms). Soy protein isolate (SPI) is considered as an essential product of soy proteins and contains protein range from 85 to 90% as a dry basis [96, 97]. Due to the good properties of soy proteins such as water solubility, fat and water absorption, gel, film, and foaming-formation and emulsion stabilization properties, they have been used as wall materials for micro- and nanoencapsulation of different bioactive ingredi-

ents alone or in combination with either proteins or polysaccharides [98].

glutelins; proteins soluble in the diluted acid or alkali [100, 101].

Cereal grains are grown worldwide and they comprise three main biopolymers which are roughly classified into three groups - protein, starch, and non-starch polysaccharides [99]. Cereal micro- and nanotechnology for biomedical, food, and pharmaceutical applications focus on fabricating highly functional micro- and nanostructures from cereal biopolymers. Cereal proteins (e.g., zein, barley, and wheat proteins) are considered a vital protein source in the diet. Cereal proteins have excellent properties such as low cost, widely available, and versatile molecules which are valuable compounds for nano- and microtechnology applications. They are classified into four classes according to the solubility of fractionations: (a) albumins; proteins soluble in water, (b) globulins; proteins soluble in the diluted salt solution, (c) prolamins; proteins soluble in the aqueous alcohol, and (d)

Zein protein is classified as a storage prolamine protein that makes up 35–60% of

total protein in corn (maize). Pure zein protein is one of the important plant



#### **Table 4.**

*Physicochemical properties of plant and animal proteins used for the delivery of bioactive ingredients.*

*Natural Polymers in Micro- and Nanoencapsulation for Therapeutic and Diagnostic… DOI: http://dx.doi.org/10.5772/intechopen.95402*


Protein ingredients have been vastly used as good encapsulating agents alone or in combination with either another protein or polysaccharides which occurs through different possible interactions (such as covalent, electrostatic, H-bonding, hydrophobic, van der Waals, and disulfide interactions) for delivery of various bioactive compounds (**Figure 7**) [94]. Different polysaccharides can be used to fabricate bilayer on the oil droplets surface with protein compounds to increase the physical stability of both emulsion and the interfacial modifying properties [95].

#### *3.1.3 Plant proteins*

their functional groups possess the ability to protect, reverse binding, and interact with numerous bioactive compounds. Nowadays, two sources of proteins; plant proteins such as soy, pulses, and cereals proteins and animal proteins such as bovine serum albumin, casein and whey proteins are widely used as encapsulating agents in micro- and nanoencapsulation techniques. Proteins are employed to encapsulate solids and liquids including oils. Their ability to encapsulate oils depends on their capacity to adsorb at the interface and form stable emulsions. The following factors

**Protein Source Main composition Properties pI Tm (°C)**

soluble

Soluble in aqueous alcohol

alcohol

Globular and water soluble

Rheomorphic, poorly water soluble, and highly stable

Globular, water soluble, and antioxidant

Linear, soluble in hot water, and highly stable 4.5 6787

6–7 75–95

5–8 90

4.4–5.5 60–90

4.7 70–90

4.8 40

125–140

4.6– 4.8

Water soluble 4.3–4.5 85–90

Water soluble 4.5 90

Water soluble 4.5 90

Soybean Albumins and globulins Globular and water

Wheat Gliadin and glutenin Soluble in aqueous

Barley Hordein and glutelin Soluble in alkali 5 115

Glutamic acid, leucine, alanine, and proline

Pea Albumins,glutelins

Chickpea Glutein, albumin,

1.3.3. Lentil Lentil Globulins, albumin,

Cheese or casein

Bovine serum or milk

2.4. Gelatin Collagen Acid (Type-A) gelatin and

*pI: Isoelectric point and Tm: denaturation thermal temperature.*

and globulins

prolamine, and globulin

glutelins, and prolamins

β-lactoglubulin, αlactalbumin, and serum albumin

Mwt colloidal calcium phosphate

583 amino acids and contains three domains: I, II, and III

basic (Type-B) gelatin

*Physicochemical properties of plant and animal proteins used for the delivery of bioactive ingredients.*

Milk 94% protein and 6% low

affect their emulsifying properties [93]:

• The molecular size of proteins

Maize (corn)

• Protein solubility

1.1. Soy protein

1.2. Cereal proteins 1.2.1. Zein protein

1.2.2. Wheat protein

1.2.3. Barley protein

1.3. Pulse proteins 1.3.1. Pea protein

1.3.2. Chickpea

2.1. Whey protein

2.2. Casein protein

2.3. Bovine serum albumin

**Table 4.**

**72**

• Hydrophobicity of the protein surface

*Nano- and Microencapsulation - Techniques and Applications*

• The flexibility of protein compounds

Plant proteins have different types such as soy proteins, cereals proteins (e.g., zein, wheat, and barley proteins), and pulses proteins (e.g., pea, chickpea, and lentil proteins).

#### *3.1.3.1 Soy proteins*

Soy proteins are globular proteins and are considered as one of the most important food proteins that are applied significantly in human diets because they have good nutritional values, health-benefiting effects, and high functionalities. They are mainly composed of albumins and globulins which represent around 50–90% of total seed proteins. They are divided according to their sedimentation coefficients into four fractions: 2S, 7S, 11S, and 15S fractions. The 2S fraction corresponds to albumins, while the globulins are present in 7S, 11S, and 15S fractions. Also, glycinin (named as 11S or SG, and Mwt 350 kDa) and β-conglycinin (named as 7S or SC, and Mwt of about 70 kDa are two globulin forms). Soy protein isolate (SPI) is considered as an essential product of soy proteins and contains protein range from 85 to 90% as a dry basis [96, 97]. Due to the good properties of soy proteins such as water solubility, fat and water absorption, gel, film, and foaming-formation and emulsion stabilization properties, they have been used as wall materials for micro- and nanoencapsulation of different bioactive ingredients alone or in combination with either proteins or polysaccharides [98].

#### *3.1.3.2 Cereal proteins*

Cereal grains are grown worldwide and they comprise three main biopolymers which are roughly classified into three groups - protein, starch, and non-starch polysaccharides [99]. Cereal micro- and nanotechnology for biomedical, food, and pharmaceutical applications focus on fabricating highly functional micro- and nanostructures from cereal biopolymers. Cereal proteins (e.g., zein, barley, and wheat proteins) are considered a vital protein source in the diet. Cereal proteins have excellent properties such as low cost, widely available, and versatile molecules which are valuable compounds for nano- and microtechnology applications. They are classified into four classes according to the solubility of fractionations: (a) albumins; proteins soluble in water, (b) globulins; proteins soluble in the diluted salt solution, (c) prolamins; proteins soluble in the aqueous alcohol, and (d) glutelins; proteins soluble in the diluted acid or alkali [100, 101].

#### *3.1.3.3 Maize (Zein) protein*

Zein protein is classified as a storage prolamine protein that makes up 35–60% of total protein in corn (maize). Pure zein protein is one of the important plant

production hardening step that stables the integrity of prepared particles, as the

*Natural Polymers in Micro- and Nanoencapsulation for Therapeutic and Diagnostic…*

Wheat proteins are obtained during the isolation of starch polysaccharide from wheat flour as a byproduct and account for 80% of total wheat seed proteins; it is also used as an essential food source for both humans and animals [106]. Wheat flour is a complex material which composes of small polysaccharide fraction as starch and protein. The latter composes of two main components as gliadin and glutenin. The constitution of gliadin is single chain polypeptides (average molecular weight, Mwt, ranged from 25 KDa to 100 KDa) which are linked by intramolecular disulfide bonds and soluble in the aqueous alcohol (70% ethanol), while glutenin is a soluble fraction and is similar to gliadin composition but they are linked via intermolecular disulfide bonds with Mwt higher than 105 KDa [106, 107]. Wheat proteins have different interesting physicochemical properties such as gel- and film-forming properties due to its low water solubility and viscoelasticity [108].

Barley crop is a very adaptable crop. It is cultivated for both animal feed and brewing industry, in which, the by-product becomes livestock feed. Barley crops and by-products are rich and affordable protein sources which include 8–13% and 20–30%, respectively [109]. Barley proteins composed of two major protein fractions: hordein and glutelin (about 35–55% and 35–40%, respectively). Hordein fraction (alcohol extracted fraction) is divided into five groups - B hordein, C hordein, γ-hordein, D hordein, and A hordein - based on their amino acid compositions and electrophoretic mobility. On the other hand, glutelin is an alkali-soluble protein after hordein extraction, so it is not possible to extract glutelin fraction free from hordein fraction contamination. Barley proteins are highly hydrophobic and they exhibit excellent foaming, emulsifying and film-forming properties indicating that the emulsifying-stabilization

process can prepare micro- and nanocapsules from barley protein [110–112].

Pulse crops are invaluable agricultural commodities that are grown in cool seasons annually. They are grown in many regions around the world such as North America (particularly Canada), Asia, and the Middle East (particularly India and Egypt). They are considered an important source of dietary protein, fiber, essential vitamins, minerals, and carbohydrates. So, they have a health value that relates to decrease of HDL cholesterol, heart disease, and type-2 diabetes. The pulse proteins including lentil, pea, and chickpea proteins which show an attractive alternative to soy proteins because they have a low risk for allergen and non-genetically modified status [113, 114]. Pulse proteins are classified according to their solubility into glutelins (dilute acid and alkaline-soluble and makes up 10–20% of the total pulse protein), globulins (soluble in water-salt solution and accounts for 70% of the total pulse protein), and albumin (water-soluble and represents about 10–20% of the total pulse protein) [113].

Pea protein is extracted from pea seeds which represents 18–30% fraction. It is

mainly composed of globulins (65–80%) that include three various proteins: legumin, convicilin, and vicilin [115]. Also, it contains albumins and glutelins as two

constituting protein does not require to re-dissolve in water [105].

*3.1.3.4 Wheat proteins*

*DOI: http://dx.doi.org/10.5772/intechopen.95402*

*3.1.3.5 Barley protein*

*3.1.3.6 Pulse proteins*

*3.1.3.7 Pea protein*

**75**

**Figure 7.**

*Suggested interactions in two biopolymers components (e.g., protein and polysaccharide) system.*

proteins due to its properties such as clear, tasteless, odorless, and edible properties, making it widely used a protein in different industrial applications [102]. The main composition of zein proteins is amino acids such as glutamic acid, leucine, alanine, and proline that are combined via disulfide bonds. It has four fractions: α, β, and γ as major fractions (accounts for 80% of the total zein protein), while the last one named δ-zein is a minor fraction. α-Zein protein is the main zein type commercially available in the market. It is water-insoluble because of the presence of non-polar amino acids which are previously mentioned but is soluble in the aqueous alcohol (50–95%). Its poor solubility in water due to the absence of essential amino acids including tryptophan and lysine decreased its usage in food products for human consumption, so zein protein nanocarriers have been applied to encapsulate core materials to enhance their distribution in water environment [103, 104]. Prolamine protein as zein protein is a valuable compound used to prepare micro-and nanoscale systems that are stable in water because these systems do not need a postproduction hardening step that stables the integrity of prepared particles, as the constituting protein does not require to re-dissolve in water [105].
