**3. Green, lean, and smart product: chicken egg as a model**

An egg is a reproductive unit that develops into a new individual like the one that produced the egg. Although very different from other cells of the chicken body, an egg is a single cell. The intelligence and love ensconced in an egg are infinitely mysterious for the following reasons [18]:

1.An egg is a large single cell.


Consider a chicken egg manufactured by nature in the oviduct of a chicken. An egg has various parts, as shown in **Figure 3**, and each part fulfills one or more functions. All components of an egg are essential for its function. As a food source, an egg is a complete powerhouse. All parts of an egg are designed to support life and provide nourishment. With their unique combination of essential vitamins, minerals, fatty acids, and amino acids, it is hard to ignore the health benefits of eggs. All the parts of an egg are organic and upcyclable. Of more than 100 elements, nature chose to use just four—carbon, hydrogen, oxygen, and nitrogen—to produce all living things. These four elements, with the addition of a little sulfur and phosphorus, can account for 99% of the weight of all living things on the planet. The major parts of an egg and its functions are presented below.

**Figure 3.** *Chicken egg and its parts.*

### **3.1 Bloom**

*Description*: Bloom, known as the cuticle, is the natural protective coating on the eggshell that seals the eggshell pores. Bloom dries and flakes off.

*Functions*: Seals off egg pores. Prevent the entry of harmful bacteria and dust into the shell. Reduces moisture loss from the egg.

### **3.2 Shell**

*Description*: The chicken eggshell is 95–97% calcium carbonate crystals stabilized by a protein matrix; without the protein, the crystal structure would be too brittle to keep its form. The organic matrix is thought to play a role in the deposition of calcium during the mineralization process. The structure and composition of the eggshell formation require enough calcium deposition within hours, which must be supplied via the hen's diet. An eggshell contains between 7000 and 17,000 semipermeable pores. Shells come in an array of colors, from blues and greens to whites, browns, and often including specks.

*Functions*: The avian eggshell holds the parts of the egg and protects the egg against damage and microbial contamination. At the same time, it prevents desiccation, provides calcium for embryogenesis, and regulates gas and water exchange for the growing embryo.

### **3.3 Outer egg membrane**

*Description*: The outer membrane is a translucent, film-like gel that nestles immediately next to the eggshell. Is partially made of keratin.

*Functions*: Outer membranes facilitate the porous activities of eggs. They operate as a bacterial barrier and air molecule vent permitting oxygen, nitrogen, carbon dioxide, and other gaseous particles to flow in and out.

*Principles for Designing Green, Lean, and Smart Microfactories: Chicken as a Model DOI: http://dx.doi.org/10.5772/intechopen.109645*

### **3.4 Inner egg membrane**

*Description*: Inner membrane is the second translucent protein barrier tucked right below the outer membrane. The inner membrane shelters the albumen (egg white). It is partially made of keratin, a fibrous amino acid. It is robust, water-insoluble, and microscopically dense, and acts as a sturdy protective shield.

*Functions*: This inner egg membrane is the strongest of the egg's protective layers. It blocks bacteria and holds the egg white and other contents together.

### **3.5 Air cell**

*Description*: Air cell rest opposite the pointed end of an egg, nestled into the more rotund and spacious bottom curve. A freshly laid egg is hot at around 105°F. As the egg cools in the environment, the air cell is formed.

*Functions*: Air cell stores the oxygen required for a developing embryo. Without this oxygen pocket, a fertilized embryo cannot mature. Air cell assists in maintaining proper internal conditions for the egg. The cascade of chemical interactions that take place between the air cell gases and the rest of the egg's fluids and proteins rely on oxygen transfer for their stability and quality. Air pockets are universal and essential parts of an egg that keep it healthy and whole, with a stable shelf life.

### **3.6 Albumen**

*Description*: Albumen, known as egg white, is a translucent fluid that makes up over 60% of an egg's interior weight. Albumen is 10% protein and 90% water. Egg white fluid consists of four segmented layers, with each alternating between a thin and thick consistency. This mix of consistencies provides protein-packed egg whites with a robust template that holds over 40 different amino acids. Chalaziferous White is the first and most central layer of the albumen. It rests around an egg yolk, restraining the yolk's movement to the center of the egg. Besides proteins, egg white contains micrograms of calcium, folate, choline, selenium, magnesium, phosphorus, and potassium; it does not contain fats.

*Functions*: It holds protein-based nutrients and compounds that aid in overall embryo growth if the egg was fertilized. During embryo development, folate and choline support cell growth, DNA replication, and hormone production. At the same time, calcium and magnesium build and activate hundreds of distinct enzymes to regulate blood sugar, blood pressure, nerves, muscles, and bone development.

### **3.7 Chalazae**

*Description*: Chalazae are the long, stringy, fibrous little squiggles that run through and around an egg's yolk. Chalazae permeate the two ends of the yolk. It is made up of strong fibrous proteins.

*Functions*: They preserve the structure and safety of the yolk. They operate like yolk scaffolding, or like ropes that anchor the yolk's outer casing, supporting and balancing the yolk's movements.

### **3.8 Vitelline membrane**

*Description*: This is a protective covering around the yolk. It is made up of two layers—the inner layer 1–3.5 μm thick, and the outer layer 0.3–0.5 μm. Vitelline membranes are made up of glycoproteins and other proteins.

*Functions*: Vitelline layer protects the yolk from cracking and seeping fluid inside the egg. It keeps the egg's central yolk separate from the albumen. A cracked internal vitelline membrane will destroy the egg. The vitelline membrane is also responsible for protein binding during the fertilization process. Without the signals and receptors held within its inner and outer layers, an egg cannot initiate the development of an embryo. It acts as a gatekeeper for hormones and substances to either pass into the yolk or remains blocked.
