Unit 6 - Food Processing

REASONS TO PROCESS FOOD

  • Definition of Food Processing:

    • Any operation carried out on raw food is termed a process, resulting in a processed food product.

  • Key Reasons for Food Processing:

    1. Preservation:

    • Extends the shelf life of food.

    1. Edibility:

    • Makes the food edible.

    1. Nutritional Quality:

    • Enhances nutritional quality of foods.

    1. Convenience:

    • Makes food more convenient to consume.

    1. Cost Reduction:

    • Reduces waste and inefficiencies.

PRINCIPLES OF FOOD PRESERVATION

  1. Asepsis:

    • Keeping out microorganisms to ensure food safety.

  2. Slowing Microbial Growth:

    • Microorganisms require specific conditions (water activity, pH, temperature, substrate, and oxygen levels) to grow. Altering any of these can decrease growth rate, extending food shelf life.

  3. Inhibition of Microbial Growth:

    • Environmental conditions can be modified to inhibit certain microbes.

  4. Killing Microorganisms:

    • Methods include:

      • Intense heat treatment (thermal treatment)

      • UV treatment

      • Chemical preservatives

  5. Controlling Chemical Reactions in Foods:

    • Food quality (color, texture, flavor) can change due to chemical reactions over time.

    • Controlling these reactions involves removing reactants (e.g., preventing oxidation).

    • Examples:

      • Unsaturated fatty acids easily oxidize; storing away from oxygen can prevent rancidity.

      • Enzymes present in fresh foods can be inactivated to preserve quality.

SOME FOOD PRESERVATION METHODS

Thermal Methods: Heat Treatment

  1. Pasteurization:

    • Definition: “Application of heat to a food product in order to destroy pathogenic microorganisms, inactivate spoilage enzymes, and reduce spoilage microorganisms.”

    • Higher temperatures require shorter times for microbial destruction.

    • Examples:

      • Low temperature long time (LTLT) pasteurization: 63 °C for 30 minutes.

      • High temperature short time (HTST) pasteurization: 73 °C for 15 seconds.

      • Higher temperature treatments (e.g., 94 °C for 0.1 seconds) achieve similar results with less impact on heat-sensitive vitamins.

  2. Sterilization:

    • Definition: Killing all microorganisms in food.

    • Commercial sterilization aims for a reduction to 10⁻⁶ cells/spores per ml (or one cell/spore in a million milliliters).

    • Example: Ultra high temperature (UHT) milk is treated at temperatures over 138 °C for a few seconds, maintaining quality while achieving sterilization.

  3. Canning:

    • Objective: Destroy nearly all microorganisms (1 in a million cans may contain a microbial cell/spore).

    • Canning procedure steps:

    1. Cleaning the food

    2. Filling the can

    3. Exhausting (removal of air)

    4. Sealing the can (airtight)

    5. Cooking the sealed can (thermal treatment)

    6. Cooling the cans to room temperature

    • High acid foods are canned at 100 °C; low acid foods at temperatures above 116 °C using retort canning (pressure canning).

  4. Blanching:

    • Briefly dipping food (usually vegetables and fruits) in boiling water followed by cold water treatment to stop the cooking process.

    • Purpose: Inactivate enzymes that otherwise deteriorate food quality.

  5. Dehydration:

    • Removal of water prevents microbial growth.

    • Methods:

      • Sun drying: Least controlled, longest method.

      • Plate drying: Uses heated trays and chambers to remove moisture.

      • Drum drying: Used for viscous fluids, coating them on a heated drum to form powder.

      • Spray drying: Atomizes food into droplets dried instantly in hot chambers.

      • Freeze drying (lyophilization): Minimizes nutrient damage and water loss; more than 99% water removed via sublimation.

  6. Refrigeration:

    • Cooling food to temperatures between 0°C and 4°C slows down microbial growth and prevents spoilage.

    • 45% of vegetables and fruit grown are wasted; refrigeration has helped reduce waste significantly.

  7. Freezing:

    • Freezing food at temperatures below 0 °C halts microbial growth.

    • Quick freezing (IQF): Food is immersed in cryogenic fluids for rapid freezing, preventing clumping.

  8. pH Modification:

    • Direct Addition: Acids (e.g., acetic acid, citric acid) enhance preservation (e.g., pickling).

    • Indirect Methods: Fermentation processes can also reduce pH, exemplified by yogurt production using specific bacteria like Lactobacillus bulgaricus.

  9. Reduction of Water Activity:

    • Methods like sugar and salt are used in jams, jellies, and salted fish to reduce microbial risks.

Special Topic: Table Salt and Hypertension

  • Sodium Content: Table salt contains about 40% sodium.

    • Dietary recommendations: 1500 mg/day (3.75 g salt).

    • Tolerable upper intake level: 2300 mg/day.

    • Average intake in Canada (2017): 2760 mg/day; higher in 2004 (3400 mg/day).

    • Health risks associated with excessive sodium intake: linking diets high in processed foods to hypertension.

FOOD IRRADIATION

  • Definition: Exposure of food to ionizing radiation (gamma rays, electron beams, X-rays) to reduce microbial populations or sterilize food.

  • Methodology: High energy waves destroy biomolecules in microbes without direct contact with radioactive materials.

  • Regulatory Notes: Not all foods can be irradiated; various regulations govern the irradiation process in Canada.

PACKAGING

  1. Purpose of Packaging:

    • Branding, information labeling, prevention of physical damage, enabling shipping, and protection against spoilage and contamination.

  2. Types of Packaging Materials:

    • Glass:

      • Advantages: Chemically inert, durable, recyclable, sturdy construction, transparent, can be produced in multiple shapes.

      • Disadvantages: Heavy, less durable.

    • Metals (Tin, Aluminum):

      • Malleable, durable, lightweight; provides effective barrier against moisture and gases.

    • Paper:

      • Lightweight and biodegradable but permeable to moisture; used for dry foods.

    • Plastics:

      • Variety of synthetic polymers available; offers flexibility but concerns regarding permeability and chemical leaching.

    • Controlled/Modified Atmospheric Packaging (CAP/MAP):

      • Altering gas concentrations within packages to extend shelf life; used for fruits like bananas and potatoes to manage ripening and rancidity.

  3. Concerns:

  • Chemical leaching in plastic packaging (e.g., BPA issues).

  • Environmental impact of packaging materials (recycling challenges).

CHEMICAL PRESERVATION METHODS

  • Regulations classify preservatives used in Canada:

    • Class 1: Curing preservatives (GRAS - Generally Recognized as Safe)

    • Class 2: Antibacterial

    • Class 3: Antifungal and antimicrobial

    • Class 4: Antioxidants

  • Natural Preservatives:

    • Include table salt, sugars, nitrates, nitrites; effective in microbial control.

  • Synthetic Preservatives:

    • Sodium benzoate (antibacterial), propionates (antifungal), BHT/BHA (antioxidants).

  • Health Implications:

    • Consumption of processed meats linked to certain cancers (WHO 2014).

DISCUSSION POINT

  • Food Processing: A Boon or a Bane?

    • Explore various perspectives on the impact of food processing on health, economy, and food security.

CONCLUDING REMARK

  • Final Note: Food processing is a critical component of food safety and preservation but entails careful consideration of methods and implications for health and sustainability.