Food Processing Techniques

Heat Processing Techniques

• Moist Heat Preservation

  • Blanching:

  • Process before freezing, canning, or drying.

  • Inactivates natural enzymes to maintain texture, color, and nutritional value.

  • Destroys enzymatic activity in vegetables/fruits.

  • Most resistant enzymes: peroxidase and catalase.

  • Not a preservation method but a pre-treatment for further processing (sterilization, dehydration, freezing).

  • Influencing factors:

    • Type of fruit/vegetable

    • Size of pieces

    • Blanching temperature

    • Heating method

• Pasteurization:

  • Destroys pathogenic microorganisms in food and beverages.

  • Named after Louis Pasteur; essential for preventing fermentation in liquids.

  • Common temperatures:

  • 63°C (145°F) for 30 minutes

  • Higher temperatures (72°C for 15 seconds, 138°-150°C for UHT).

  • Destroys spoilage microorganisms to prolong food storage.

• Tyndallization (Fractional Sterilization):

  • Involves boiling goods for 20 minutes on three consecutive days.

  • Kills microorganisms by repeat boiling; allows spores to germinate and be killed.

Evaporation and Distillation

• Evaporation:

  • Partially removes water from liquid foods; typically involves boiling.

  • Concentrates liquid foods, increasing shelf life and reducing microbial damage.

  • Common applications: concentration of sugar, milk, juices.

  • Challenges include heat sensitivity and potential quality loss due to concentration.

  • Operated under vacuum to lower boiling point and minimize thermal degradation.

• Distillation:

  • Separates components based on boiling point differences.

  • High energy consumption but effective for separating liquid mixtures,

  • Utilizes vapor pressures and primarily performed in columns.

Extrusion

• Extrusion Process:

  • Material is pushed through an opening, creating desired shapes under heat, pressure, and shear.

  • Often used in cereals and snacks (pasta, breakfast cereals).

  • Involves cooking, flavor encapsulation, and shaping.

  • Fast process; retains nutrients better than traditional methods due to high temperature and short duration.

  • Effective in reducing anti-nutritional factors in legumes.

Heat Processing with Hot Air

• Baking/Roasting:

  • Changes food physicochemical properties (flakiness, tenderness).

  • Key reactions:

  • Melting fats (32-55°C): traps air for texture.

  • Gas expansion (carbon dioxide) for leavening.

  • Protein coagulation (60-85°C): forms structure.

  • Starch gelatinization (40-95°C): affects texture.

  • Browning reactions (above 150°C) for flavor.

• Frying:

  • Combination of heat and mass transfer, influences sensory characteristics (color, flavor).

  • Simultaneous dehydration: 5 dehydration zones defined based on oil absorption and quality.

  • Changes in nutriient profile & quality must be monitored closely to prevent spoilage and develop undesirable flavors.

Heat Processing by Radiation

• Dielectric, Ohmic, and Infrared Heating:

  • Involves using radiant energy for cooking, with applications in food production.

  • Ideal for rapid heating without direct contact with hot surfaces.

Controlled and Modified Atmosphere Storage

• Chilling and Freezing:

  • Controls microbial activity, enhances shelf life, reduces spoilage risk.

  • Importance of rapid freezing to maintain food quality.

• Smooth Transition in Packaging:

  • Utilizes low temperatures for food preservation.

  • Controlled atmosphere for reducing quality loss during storage.

Applications and Benefits of Technologies

• Food Irradiation:

  • Effective microbial inactivation and shelf-life extension.

  • Does not make food radioactive; safe approved methods established globally.

  • Versatile applications across a variety of food products.

In summary, food processing techniques utilize heat or radiation for preservation, enhancing food safety, extending shelf life, and focusing on quality management during production to prevent spoilage while retaining nutritional value.