Production of coated preserved eggs using reactor technology

### Coating Methods for Preserved Eggs

#### 1. **Collodion Coating**

- **Ingredients**:

- 70% Ether

- 15% Ethanol

- 10% Nitrocellulose

- 2% Rosin

- 3% Castor Oil

- **Preparation**:

- Mix the ingredients in a fireproof, sealed jar.

- If nitrocellulose is dried, add 5% ethanol (water content <5%).

- Shake until dissolved.

- **Application**:

- Rinse preserved eggs with cold water and dry.

- Coat eggs by applying collodion solution to each end, allowing 10 minutes of drying time per side.

- Ensure the entire eggshell is coated.

- Package the coated eggs in plastic bags or cardboard boxes for storage.

- **Challenges**:

- Labor-intensive manual process.

- High raw material costs.

- Risk of yolk discoloration if coating is delayed after maturation.

#### 2. **White Oil Paint Coating**

- **Formula (32# and 33#)**:

- Liquid Paraffin: 29.71–39.71%

- Span: 2.60–4.6%

- Triethanolamine: 1.04%

- Tween: 3.90%

- Pepega: 0.67–2.57%

- Tap Water: 50–60%

- Stearic Acid: 2.08%

- **Preparation**:

- Heat liquid paraffin, span, Tween, Pepega, and stearic acid in a reactor to 92–93°C.

- Heat water and triethanolamine separately to 94–95°C, then mix into the reactor.

- Cool the mixture to room temperature with stirring (60 rpm) to form a stable white emulsion.

- Use cold water in the reactor jacket to accelerate cooling if needed.

- **Properties**:

- Milky white, odorless, stable emulsion with a pH of 7.5–8.

- Non-toxic, leaves a shiny, mark-free surface.

- **Usage**:

- Dilute with water to desired concentration.

- Dip preserved eggs, rinse off excess, and dry before sealing.

- **Cost**: Approximately 1.29 yuan/kg.

#### 3. **Wax Emulsion Coating (26#)**

- **Formula**:

- White Paraffin: 26.2%

- Oleic Acid: 9.75%

- Ammonia (25–28% NH₃): 4.87%

- Water: 59.18%

- **Preparation**:

- Dissolve white paraffin and oleic acid in a reactor at 95–100°C.

- Heat water and dissolve ammonia separately, then mix into the paraffin-oleic acid solution at 95°C.

- Stir at 60 rpm for 5–10 minutes, then cool to room temperature using a reactor jacket with cold water.

- **Properties**:

- Milky white, stable emulsion that disperses well in water.

- Leaves no white spots on the eggshell and ensures long-term storage quality.

- **Quality Standards**:

- Coated eggs should have no attachments other than the coating.

- Quality is comparable to candied preserved eggs.

These methods provide effective solutions for preserving eggs, with varying costs and application processes.