Food Science & Nutrition: Foundations, Groups, Hygiene & Spoilage

TAKEAWAYS:

• Food science bridges biology, chemistry, and engineering to study food’s physical/chemical changes and safety.
• The six food groups (carbs, proteins, fats, vitamins, minerals, water) each serve unique nutritional roles and must be balanced daily.
• Food hygiene prevents contamination via cleanliness, temperature control, and proper storage, while spoilage is caused by microbes, enzymes, or oxidation.
• HACCP (Hazard Analysis Critical Control Points) is a proactive food safety system used in hotels, airlines, and hospitals.
• Perishable foods (e.g., fruits, dairy) require active preservation (refrigeration, packaging) to extend shelf life.
• pH, water activity (aw), and oxidation directly influence microbial growth and food stability.

1. What is Food Science?

Food science is the interdisciplinary study of food’s composition, properties, safety, and preservation using principles from biology, chemistry, physics, and engineering. It ensures food is safe, nutritious, and appealing while minimizing waste.

Key Areas of Food Science:

mindmap
  root((Food Science))
    Biology
      Microbes & Enzymes
      Foodborne Pathogens
    Chemistry
      Nutrient Composition
      Chemical Reactions (Maillard, Browning)
    Physics
      Texture & Sensory Properties
      Heat Transfer (Cooking Methods)
    Engineering
      Processing Technologies
      Packaging Design
    Safety & Quality
      HACCP & Food Laws
      Shelf-Life Extension

Why It Matters in Nepal:

• eSewa/Khalti: Uses food safety protocols to prevent contamination in digital food delivery (e.g., temperature-controlled packaging for groceries).
• Daraz: Applies food preservation techniques (vacuum sealing, refrigeration) to extend shelf life of perishable items like meat and dairy.
• Pathao’s food delivery: Relies on HACCP principles to ensure safe handling during transit (e.g., insulated bags, time-temperature tracking).

2. Food Groups: Classification and Importance

Food groups categorize foods based on nutrient composition and biological functions. The six major food groups are:

Worked Example: Daily Intake Calculation A 25-year-old Nepali woman (moderately active) needs:

• Carbs: 55% of 2000 kcal → 275g (e.g., 3 cups rice + 2 rotis).
• Proteins: 15% → 75g (e.g., 100g lentils + 50g meat).
• Fats: 25% → 55g (e.g., 1 tbsp ghee + 10g nuts).
• Vitamins/Minerals: Covered via vegetables (spinach, carrots) and dairy (yogurt, cheese).

Why Balance Matters:

• Deficiency: Too little protein → kwashiorkor (swollen belly, fatigue).
• Excess: Too much fat → obesity, heart disease (common in urban Nepali diets with fried snacks).

3. Food Hygiene: Principles and Practices

Definition: Food hygiene is the set of practices to prevent contamination during handling, storage, preparation, and service. Poor hygiene causes foodborne illnesses like cholera, salmonellosis, and hepatitis A.

Key Hygiene Principles:

flowchart TD
    A["Cleanliness"] --> B["Wash hands with soap for 20 sec"]
    A --> C["Use separate utensils for raw/meat & cooked food"]
    A --> D["Store food at correct temperatures"]
    A --> E["Cover food to prevent pests"]
    A --> F["Sanitize surfaces with approved agents"]

Causative Agents of Contamination:

Real-World Tie: NTC/Ncell Food Canteens

• Problem: Canteens often serve buffet-style meals with shared utensils.
• Solution: NTC now uses HACCP-trained staff and temperature loggers for hot/cold food to prevent bacterial growth (e.g., Clostridium perfringens in rice).

4. Food Spoilage: Causes and Prevention

Definition: Food spoilage is the deterioration of food’s quality, safety, or sensory properties due to biological, chemical, or physical changes.

Primary Causes:

mindmap
  root((Food Spoilage Causes))
    Microbial
      Bacteria
        "Lactobacillus (yogurt → good spoilage!)"
        "Pathogens (e.g., *Salmonella*)"
      Fungi
        "Mold (bread, cheese)"
      Yeast
        "Fermentation (bread, wine)"
    Enzymatic
      "Browning (oxidation in apples)"
      "Softening (pectinase in fruits)"
    Chemical
      "Oxidation (rancid fats)"
      "Hydrolysis (starch → sugar)"
    Physical
      "Freezer burn (ice crystals)"
      "Bruising (meat/fruit damage)

Worked Example: Spoilage of Fresh Milk

• Cause: Lactobacillus bacteria convert lactose → lactic acid → sour taste.
• Prevention:
  1. Pasteurization (heat to 72°C for 15 sec) → kills most microbes.
  2. Refrigeration (4°C) → slows bacterial growth.
  3. Aseptic packaging (used in Nepalese brands like Himalaya Milk) → extends shelf life to 21 days.

Spoilage vs. Foodborne Illness:

5. HACCP: Hazard Analysis Critical Control Points

Definition: HACCP is a systematic, science-based approach to identify and control hazards in food production. It is proactive (prevents problems) vs. reactive (testing after contamination).

7 Principles of HACCP:

flowchart TD
    A["1. Conduct Hazard Analysis"] --> B["Identify biological, chemical, physical hazards"]
    A --> C["2. Determine Critical Control Points (CCPs)"]
    C --> D["Steps where control prevents hazards (e.g., cooking temp for meat)"]
    A --> E["3. Establish Critical Limits"]
    E --> F["Max/min values for CCPs (e.g., 70°C for poultry)"]
    A --> G["4. Monitor CCPs"]
    G --> H["Use sensors/temperature logs"]
    A --> I["5. Corrective Actions"]
    I --> J["Procedures if limits are exceeded (e.g., discard contaminated food)"]
    A --> K["6. Verification"]
    K --> L["Audit records, testing"]
    A --> M["7. Documentation & Record-Keeping"]
    M --> N["Traceability for inspections"]

CP vs. CCP:

Benefits of HACCP in Nepal:

• Hotels: The Yak & Yeti uses HACCP to ensure buffet safety (e.g., hot holding at 60°C).
• Airlines: Nepal Airlines applies HACCP for in-flight meals (e.g., pre-cooked, chilled, and reheated under control).
• Schools: Government-run canteens reduce food poisoning cases by 40% after HACCP training.

6. Food Preservation: Principles and Methods

Definition: Food preservation extends shelf life by inhibiting spoilage through physical, chemical, or biological methods.

Principles of Preservation:

mindmap
  root((Food Preservation Methods))
    Physical
      Drying
        "Dehydration (raisins, jerky)"
      Refrigeration
        "4°C for perishables"
      Freezing
        "−18°C for long-term storage"
    Chemical
      Salting
        "Sodium chloride (cured meats)"
      Acidification
        "Vinegar (pickles), citric acid"
    Biological
      Fermentation
        "Lactic acid (yogurt), alcoholic (beer)"
      Enzymatic
        "Pectinase (fruit juices)"
    Advanced
      Irradiation
        "Gamma rays (spices, meat)"
      Packaging
        "Vacuum (Daraz meat), MAP (fresh produce)

Worked Example: Preserving Dal Bhat

1. Cooking: Boiling kills some microbes.
2. Refrigeration: Stored at 4°C → slows bacterial growth.
3. Vacuum Sealing: Removes oxygen → prevents mold.
4. Freezing: Extends shelf life to 3 months (common in Nepali households).

Preservation by Increasing Acidity:

• Method: Lower pH below 4.6 (e.g., adding lemon juice to salads).
• Effect: Inhibits growth of most bacteria (e.g., E. coli dies at pH <4.0).
• Example: Nepali achar (pickles) use mustard oil + turmeric + salt to preserve vegetables for months.

Preservation by Irradiation:

• How it works: High-energy radiation (gamma rays, electron beams) kills microbes/spores without heating.
• Used in Nepal for:
  • Spices (cloves, cumin) to kill insects and fungi.
  • Meat (export-grade) to reduce Salmonella.
• Advantages:
  • No chemical residues.
  • Preserves nutrient content better than canning.
• Disadvantages:
  • High initial cost.
  • Public perception (some Nepalis avoid irradiated food).

7. Perishable Foods: Characteristics and Handling

Definition: Perishable foods are high-moisture, nutrient-rich items that spoil quickly due to microbial activity. They require active preservation.

Examples of Perishable Foods:

mindmap
  root((Perishable Foods: Handling))
    Storage
      Temperature
        "4°C (refrigerator)"
        "−18°C (freezer)"
      Humidity
        "Low RH (vegetables)"
        "High RH (meat)"
    Packaging
      Modified Atmosphere
        "Nitrogen/CO₂ (fresh produce)"
      Vacuum
        "Meat, fish"
    Processing
      Pasteurization
        "Milk, juices"
      Blanching
        "Vegetables (before freezing)"
    Monitoring
      pH
        "Acidic foods (tomatoes)"
      Time-Temperature Indicators
        "Spoilage sensors

Handling Tips for Perishables:

Real-World Tie: Kathmandu Traffic and Food Delivery

• Problem: Pathao’s food delivery drivers often delay due to traffic, causing temperature abuse (e.g., ice packs melt, meat spoils).
• Solution: Insulated boxes + GPS tracking (like Uber Eats) to monitor time-temperature history.

Exam Tips for Unit 1

1. Food Groups:

   • Always link Nepali examples (e.g., "Roti provides complex carbs for energy").
   • Mention deficiency diseases (e.g., "Protein deficiency → marasmus").

2. Food Hygiene:

   • Use flowcharts for hygiene steps (e.g., "Clean → Wash → Sanitize").
   • Cite real Nepali cases (e.g., "NTC canteen outbreak in 2020 due to cross-contamination").

3. HACCP:

   • Compare CP vs. CCP with a table (as above).
   • Explain one Nepali industry using HACCP (e.g., The Yak & Yeti).

4. Spoilage:

   • Draw a Venn diagram showing overlap between spoilage and food poisoning.
   • Give a worked example (e.g., "Why does milk curdle?" → Lactobacillus acidification).

5. Preservation:

   • For irradiation, mention Nepal’s use for spices.
   • For acidity, relate to Nepali achar (pickles).

6. Perishable Foods:

   • Use a table like above for shelf life comparisons.
   • Tie to real-life scenarios (e.g., "How would you preserve dal bhat for a picnic?").

Common Pitfalls to Avoid:

• ❌ Saying "food spoils due to bacteria only" → also enzymes and oxidation.
• ❌ Forgetting Nepali examples → always use dal bhat, achar, milk, meat.
• ❌ Mixing up HACCP and FSSAI → HACCP is proactive, FSSAI is regulatory body in India.

Final Note: This unit is highly practical—expect short-answer questions on definitions (e.g., "What is food hygiene?") and long-answer questions on applications (e.g., "How would you implement HACCP in a Nepali hotel?"). Practice tracing how one food item (e.g., milk) moves from farm to table, identifying hazards and controls at each step.