Non-Thermal Food Processing Quiz

Other Preservation Techniques

• Non-thermal processing is a promising approach for fruit juice and beverage preservation.
• Products using non-thermal techniques retain more sensory and nutritional qualities compared to traditionally processed products.
• Examples include high hydrostatic pressure (HHP), pulsed electric field (PEF), and ultrasound (US).

High Pressure Processing (HPP)

• Also known as high hydrostatic pressure (HHP)
• HHP uses up to 900 MPa to kill microorganisms in food, without degrading vitamins, flavour, or colour.
• High pressures (up to 1000 MPa) are applied to submerged food packages, distributing pressure evenly.
• 350 MPa for 30 minutes or 400 MPa for 5 minutes significantly reduces vegetative cells of bacteria, yeasts, or molds.
• HPP doesn't involve heating, so sensory and nutritional qualities are preserved similar to unprocessed products.
• Processing times are faster than thermal processing.
• Bacterial spores are resistant; therefore, products are chilled or refrigerated.
• Shelf-life varies by product type (e.g., fruit-based chilled products have a shelf-life of 21-28 days, while meat products have a shelf-life of 30-60 days). Meat products may use curing agents to prevent botulism.

Pulse Electric Field (PEF)

• Non-thermal pasteurization technique.
• Used on liquid foods (liquid egg, milk, fruit juices).
• Main purpose is to inactivate pathogenic microorganisms.
• Minimizes energy loss associated with heating foods.
• Superior to traditional heat treatment, as it avoids or greatly reduces detrimental changes in the sensor and physical properties of foods.
• Involves applying pulses of high voltage (typically between 20-80 kV/cm) to food located between electrodes.
• Pulses have specific frequency, duration, and intensity.
• Application is restricted to foods that can withstand high electric fields. PEF treatment chamber consists of at least two electrodes and insulation, creating a volume where food receives pulses. Electrodes are made of inert materials (e.g., titanium).
• The application of electric fields to biological cells causes a buildup of electrical charges at the cell membrane. The resulting pore formation increases membrane permeability leading to cell content loss or intrusion of external media.
• Treatment effectiveness depends on the intensity and number of pulses (frequency).
• Apple juice treated with PEF had a longer shelf life (28 days) compared to fresh squeezed apple juice (21 days).
• No significant changes in ascorbic acid or sugars were observed.

Pulse Light

• Non-thermal method.
• Three main components: power supply, pulse configuration device, and xenon lamp.
• Converts high-speed electronic pulses into high-energy light pulses.
• Uses high-intensity flashes of broad-spectrum light (UV to infrared) at short durations.
• High energy is delivered to the lamp, producing intense pulses of light focused on the treatment area.
• Exposing food to this light disrupts bacterial cell membranes.
• Effectiveness depends on intensity and number of pulses.

Ultrasound Waves

• Defined as energy generated by sound waves over 20,000 vibrations per second.
• Sonic waves with frequencies above human hearing (16-20 kHz).
• Generated by mechanical vibrations above 18 kHz.
• During implosion, very high temperatures and pressures are reached inside bubbles.
• Potentially most useful for sterilizing liquids (e.g., milk and juices).
• Disadvantages have limited lethal effect and effective if applied with pressure (e.g., Mano Sonication or Mano Thermo Sonication).

Oscillating Magnetic Field (OMF)

• Static Magnetic Field (SMF): Constant magnetic field intensity.
• Food is treated with magnetic pulses (millisecond range) with exposure times of 25 to over 100ms
• Frequency applied is between 5-50 kHz and field strength is between 5-50 Tesla.
• Effectiveness is dependent on pulse number and frequency.
• OMF might loosen bonds between ions and proteins in microorganisms.
• The effect on microorganisms may be due to the rotating electric field formed by the variable magnetic field.