Food Preservation & Additives: Methods, Hazards & Safety

TAKEAWAYS:

• Food spoilage is caused by microbes, enzymes, and chemical reactions, and can be delayed by preservation methods like heat, cold, or acidity.
• Additives (preservatives, antioxidants, emulsifiers) extend shelf life but must comply with Nepal’s Food Safety and Quality Act (2075).
• HACCP (Hazard Analysis Critical Control Point) is a 7-step system to prevent foodborne illness in hotels/restaurants.
• Irradiation and acidity control are non-thermal preservation techniques used in Nepal’s dairy and meat industries.
• Water activity (aw) and pH directly affect microbial growth—low aw (<0.6) or high acidity (pH <4.6) inhibit spoilage.
• Sanitizing agents (chlorine, quaternary ammonium) must be approved by the Department of Food Technology and Quality Control (DoFTQC).

1. Food Spoilage: Causes and Consequences

Food spoilage is the unwanted change in food quality due to biological, chemical, or physical factors. It leads to waste, economic loss, and foodborne illness.

Causes of Spoilage

mindmap:
  root((Food Spoilage))
    Biological:
      Microorganisms:
        - Bacteria (e.g., *E. coli*, *Salmonella*)
        - Fungi (molds, yeasts)
        - Viruses (rare, but in ready-to-eat foods)
      Enzymes:
        - Natural enzymes (e.g., polyphenol oxidase in fruits → browning)
    Chemical:
      Oxidation (rancidity in fats/oils)
      Maillard reaction (browning in cooked foods)
    Physical:
      Contamination (dirt, dust)
      Mechanical damage (bruising in fruits)

Worked Example: Spoilage in Fresh Milk

• Cause: Lactobacillus bacteria (pH drops → curdling).
• Effect: Sour taste, clumping, and economic loss for dairy farmers.
• Prevention: Pasteurization (72°C for 15 sec) kills microbes; refrigeration (4°C) slows bacterial growth.

2. Principles of Food Preservation

Preservation slows or stops spoilage using physical, chemical, or biological methods.

A. Physical Methods

B. Chemical Methods

• Acidity Control: Low pH (<4.6) inhibits bacterial growth (e.g., pickling in aachar).

  flowchart TD
    A["Food (pH >4.6)"] -->|"Add vinegar/lemon"| B["pH <4.6"]
    B --> C["Inhibits *Clostridium botulinum*"]
    C --> D["Safe for fermentation (e.g., *sukuti*)"]

• Antioxidants: Prevent oxidation (e.g., ascorbic acid in jhamri batter).
• Preservatives: Benzoic acid (in jams), sulfur dioxide (in dried fruits).

C. Biological Methods

• Fermentation: Uses beneficial microbes (e.g., yogurt from dahi bacteria, tempeh in Nepalese communities).
• Natural Antimicrobials: Garlic (allicin), turmeric (curcumin).

3. Food Additives: Types and Regulations

Additives enhance safety, texture, or shelf life but must be DoFTQC-approved.

Types of Additives

mindmap:
  root((Food Additives))
    Preservatives:
      - Benzoic acid (pH-dependent)
      - Sulfur dioxide (dried fruits)
    Antioxidants:
      - Ascorbic acid (vitamin C)
      - Tocopherol (vitamin E)
    Emulsifiers:
      - Lecithin (in *milkshakes*)
    Colorants:
      - Turmeric (natural, in *besan chura*)
    Flavor Enhancers:
      - MSG (in instant noodles)

Regulations in Nepal

• Food Safety and Quality Act (2075) bans MSG in infant food and artificial colors in dairy.
• DoFTQC approves additives like:
  • E200–E299 (preservatives: benzoic acid, sulfur dioxide)
  • E300–E399 (antioxidants: ascorbic acid, vitamin E)

Worked Example: Aam Panna Preservation

• Problem: Fermentation causes off-flavors in aam panna (raw mango drink).
• Solution: Add 0.1% benzoic acid (E210) to inhibit yeast/mold.
• Regulation Check: E210 is approved for acidic foods (pH <4.6).

4. HACCP: Hazard Analysis Critical Control Point

HACCP is a 7-step system to prevent foodborne illness in hotels, restaurants, and catering.

HACCP Steps (with Nepalese Example: Thakali Dhaba)

sequenceDiagram
    participant Customer
    participant Dhaba
    participant DoFTQC

    Dhaba->>Dhaba: 1. Conduct Hazard Analysis (e.g., *E. coli* in raw meat)
    Dhaba->>Dhaba: 2. Identify Critical Control Points (CCPs):
    Dhaba->>Dhaba:    - Cooking temp of *momo* filling (>70°C)
    Dhaba->>Dhaba:    - Storage temp of *dal* (<5°C)
    Dhaba->>Dhaba: 3. Set Critical Limits (e.g., *momo* core temp: 74°C)
    Dhaba->>Dhaba: 4. Monitor (use thermometer for *dal* storage)
    Dhaba->>Dhaba: 5. Corrective Action (if *dal* >5°C, reheat)
    Dhaba->>Dhaba: 6. Verification (weekly DoFTQC inspection)
    Dhaba->>Dhaba: 7. Documentation (logbook for CCPs)

CP vs. CCP

Advantages of HACCP in Catering: ✅ Reduces foodborne illness (e.g., Salmonella in poha). ✅ Cost-effective (less waste from spoilage). ✅ Legal compliance (DoFTQC mandates HACCP for large restaurants).

5. Role of pH, Oxidation-Reduction Potential (ORP), and Water Activity (aw)

These three factors determine microbial growth.

A. pH and Microbial Growth

• Acidic foods (pH <4.6): Safe for fermentation (e.g., sukuti, tempeh).
• Neutral/Alkaline (pH 6–8): High risk of Bacillus or Clostridium (e.g., botulism in improperly canned aachar).

B. Oxidation-Reduction Potential (ORP)

• High ORP (>200 mV): Oxidizing environment (inhibits microbes).
  • Example: Cold storage of meat with ORP >200 mV prevents E. coli.
• Low ORP (<100 mV): Reducing environment (favors Clostridium).
  • Example: Vacuum-packed fish in Newari cuisine must be stored at <4°C.

C. Water Activity (aw)

• aw < 0.6: Microbes cannot grow (e.g., dehydrated lentils for dal production).
• aw 0.6–0.9: Moderate growth (e.g., mold on bread).
• aw > 0.9: Rapid microbial growth (e.g., spoilage in fresh tomatoes).

Worked Example: Nepali Pickles (aw Control)

• Problem: Aachar spoils in 2 months due to high aw.
• Solution: Add salt (10%) to lower aw to 0.85 (inhibits Clostridium).
• Result: Shelf life extends to 6 months.

6. Food Safety Practices in Nepal

Sanitizing Agents (DoFTQC-Approved)

Cleaning vs. Sanitizing

In the Real World

1. eSewa/Khalti (Digital Payments)

   • Idea Used: Irradiation for ATM cards
     • Nepal Rastra Bank uses gamma irradiation to sterilize ATM cards and PIN pads, preventing microbial contamination from touch surfaces.
   • Why It Matters: Reduces bacterial growth (e.g., Staphylococcus) on frequently touched plastic.

2. Daraz (Food Delivery)

   • Idea Used: Cold Chain Logistics (aw control)
     • Daraz partners with Nepal Electricity Authority (NEA) for refrigerated trucks to maintain aw < 0.9 in perishable orders (e.g., pizza, biryani).
   • Real Impact: Cuts food waste by 30% in Kathmandu.

3. Nepalese Dairy Farms (e.g., Nepal Dairy Corporation)

   • Idea Used: HACCP in Milk Processing
     • CCP 1: Pasteurization (72°C, 15 sec) to kill Mycobacterium tuberculosis.
     • CCP 2: Storage at 4°C to control Lactobacillus.
   • Outcome: Exports sterilized milk powder to India without spoilage.

Exam Tip

How to Score Full Marks in Unit 5:

1. Define + Explain: Always link definitions to real Nepalese examples (e.g., define food spoilage → mention aachar fermentation).
2. Compare CP vs. CCP: Use a table (as above) and cite a hotel/restaurant scenario.
3. Worked Examples: Show calculations for aw or pH adjustments (e.g., "Add 10% salt to lower aw from 0.95 to 0.85").
4. HACCP Steps: Draw a flowchart (like the sequence diagram above) for a Thakali dhaba.
5. Regulations: Mention DoFTQC and Food Safety Act (2075) in every answer about additives.
6. Visuals: Sketch pH vs. microbial growth or HACCP flowchart in the exam if time permits.

Common Mistakes to Avoid:

• ❌ Saying "additives are harmful" without citing DoFTQC regulations.
• ❌ Forgetting to mention aw < 0.6 for dehydration preservation.
• ❌ Mixing up CP (general control) and CCP (critical control).

Final Note: Focus on Nepal-specific examples (e.g., aachar, dal bhat, Daraz) and DoFTQC compliance—examiners love local relevance!