Food Tech

• Major food preservation techniques can be categorized based on the mode of action as:

  • Slowing down or inhibiting chemical deterioration and microbial growth
  • Directly inactivating bacteria, yeasts, molds, or enzymes
  • Avoiding recontamination before and after processing
• A good method of food preservation slows down or prevents the action of spoilage agents without damaging the food
• Principles of food preservation include:

  • Removal of micro-organisms or inactivating them by removing air, water, lowering or increasing temperature, increasing salt/sugar/acid concentration
  • Inactivating enzymes by changing conditions like temperature and moisture
  • Removal of insects, worms, and rats by storing food in dry, airtight containers
• Postharvest technology involves handling, preservation, and storage of harvested foods to maintain their integrity, freshness, and quality
• Inhibition methods for food preservation involve controlling the environment, processing methods, and intrinsic properties of foods

  • Chilling and storing at temperatures below 5°C is a popular method
  • Use of chemicals in foods for preservation, including additives to control pH, act as antimicrobes, and antioxidants
• Organic acids and esters like sulfites, nitrites, acetic acid, citric acid, lactic acid, sorbic acid, benzoic acid, sodium diacetate, sodium benzoate, methyl paraben, ethyl paraben, propyl paraben, and sodium propionate are commonly used preservatives
• Antimicrobial agents from natural sources like herbs and spices are used for food preservation

  • Essential oils from herbs and spices show antimicrobial properties
  • Antioxidants are used to control oxidation in foods and have health benefits
• Wood smoke is used for food preservation, imparting flavor, color, and acting as a bactericidal and antioxidant

  • pH levels below 4.5 are considered low-risk foods and need less severe heat treatment
• Acids like propionic, sorbic, and benzoic acids inhibit microbial growth by lowering cytoplasmic pH

  • Inorganic acids like sulfate and nitrite are effective at reduced pH values
  • Enzymes play a role in food preservation by degrading unwanted components in microorganisms
• Antibiotics are used in growth enhancement and disease control in healthy animals
• Increasing antibiotic resistance is a significant concern
• Risk-benefit analysis is crucial when using antimicrobial agents or preservatives
• Physical modifications during preservation can improve sensory, nutritional, and functional properties of foods
• Water is an important constituent of all foods
• Activity of water is correlated with food stability and microbial growth
• Water activity is more important for stability than the total amount of water
• Minimum water activity limits for microbial growth: 0.6 – 0.7 for most foods, 0.85 – 0.86 for pathogenic bacteria, 0.80 for yeast and molds, and no growth below 0.62
• Drying is one of the oldest food preservation methods
• Drying reduces water activity by separating out water
• Drying methods include sunlight drying and the use of sophisticated equipment
• Loss of flavor, aroma, or functional compounds is a challenge with drying
• Freezing changes the physical state of a substance by turning water into ice
• Microbial growth stops below -18°C
• Enzymatic and nonenzymatic changes continue at slower rates during frozen storage
• Freezing retains fresh-like qualities in food
• Edible coatings serve various purposes in food systems
• Coatings can improve appearance, texture, and reduce water loss
• Encapsulation technology coats minute particles or whole ingredients for various purposes
• Gums and gels like casein, guar gum, agar, carrageenan, and pectin provide structure and functionality to food products
• Modified atmosphere packaging helps minimize physiological and microbial decay in perishable produce
• Different methods of maintaining a modified atmosphere include passive, controlled, and active packaging
• Active packaging can absorb or release specific compounds in the gas phase
• Heat energy is widely used for food preservation
• Advantages of using heat include safety, tender cooked flavors, and long shelf life
• Disadvantages include textural disintegration and nutritional deterioration
• Heat treatment processes include pasteurization, sterilization, cooking, extrusion, and frying
• High pressure and ultrasound technologies offer nonthermal preservation effects
• High hydrostatic pressure favors reactions with a decrease in volume
• Ultrasound can be used for food preservation or processing based on its effects
• Various forms of electrical energy are used in food preservation, such as ohmic heating, microwave heating, and high-intensity pulsed electric field