9.2 Non-thermal processing technologies

Non-thermal food processing technologies offer exciting alternatives to traditional heat treatments. These methods, like high pressure processing and pulsed electric fields, can kill microbes and extend shelf life while preserving food quality and nutrients.

From irradiation to ultrasound, these innovative techniques harness physical forces to make food safer without compromising taste or texture. They're revolutionizing how we process and preserve food, addressing consumer demands for fresh, minimally processed products.

Pressure and Electric Field Technologies

High Pressure Processing (HPP)

• Uses high hydrostatic pressure (100-1000 MPa) to inactivate microorganisms and enzymes in food products
• Pressure is applied uniformly throughout the product, regardless of its size or shape
• Can be used on both solid and liquid foods (juices, guacamole, ready-to-eat meats)
• Maintains the original flavor, texture, and nutritional value of the food
• Extends shelf life without the need for preservatives or heat treatment
• Requires specialized equipment and packaging materials that can withstand high pressures

Pulsed Electric Field (PEF) and Cold Plasma

• PEF applies short, high-voltage pulses to food products
  • Causes electroporation of microbial cell membranes, leading to cell death
  • Minimal impact on food quality attributes (flavor, color, texture)
  • Suitable for liquid and semi-solid foods (fruit juices, milk, yogurt)
• Cold plasma uses ionized gases to inactivate microorganisms on food surfaces
  • Generated by applying electrical energy to a gas (air, nitrogen, helium)
  • Plasma contains reactive species (electrons, ions, free radicals) that damage microbial cells
  • Can be applied to a wide range of foods (fruits, vegetables, meats, nuts)
  • Potential to replace chemical sanitizers and reduce water usage in food processing

Ultrasound

• Uses high-frequency sound waves (>20 kHz) to create cavitation bubbles in liquid foods
  • Bubbles collapse and generate localized high temperatures and pressures
  • Disrupts microbial cell membranes and inactivates enzymes
• Can be combined with other technologies (heat, pressure) for enhanced effects (thermosonication, manosonication)
• Applications include microbial inactivation, extraction of bioactive compounds, and improvement of mass transfer processes (brining, marination)
• Requires optimization of process parameters (frequency, power, time) for specific food applications

Electromagnetic Spectrum Technologies

Irradiation

• Uses ionizing radiation (gamma rays, X-rays, electron beams) to inactivate microorganisms and parasites in food
• Damages microbial DNA, preventing reproduction and growth
• Can be used on a wide range of foods (spices, fruits, vegetables, meats)
• Extends shelf life and improves food safety without significant changes in food quality
• Requires strict safety measures and regulated facilities for radiation sources
• Consumer acceptance remains a challenge due to misconceptions about the technology

Ultraviolet Light (UV) and Ozonation

• UV light (200-280 nm) inactivates microorganisms by damaging their DNA
  • Commonly used for surface decontamination of food products and packaging materials
  • Effective against a wide range of bacteria, viruses, and molds
  • Requires direct exposure and may be limited by surface irregularities or shadowing
• Ozonation uses ozone gas (O3) as a powerful oxidizing agent
  • Inactivates microorganisms by oxidizing cell membranes and critical enzymes
  • Can be applied in gaseous or aqueous form (washing, storage atmospheres)
  • Effective against a wide range of bacteria, viruses, and parasites
  • Requires on-site generation due to ozone's instability and toxicity
  • May cause oxidation of food components and affect sensory qualities at high concentrations