FOOD PRESERVATION

• Food preservation

  Process of treating and handling food in ways that slow down or completely stop spoilage and prevent foodborne illnesses while maintaining nutritional quality, flavour, and texture of food
• Importance and needs to preserve food

  • To prevent spoilage, foodborne illnesses and foodborne infections by eliminating/effectively reducing pathogen and microbes
  • To ensure food safety and allow for a wide variety of food
  • To help overcome issues in agriculture of uneven production and supply such as by maximising availability and minimising waste
  • To introduce high-value foods into diets such as truffle with a unique and enjoyable flavour and aroma
• Principles behind food preservation

  • Eliminating/reducing microbial load
  • Controlling enzyme activity
  • Controlling environmental factors
  • Reducing physical damage
  • Adding preservatives
• Vinegar

  Acetic acid is a key component, providing an acidic environment unfavourable for microbial growth
• Low temperature

  Slows down or inactivates microbes from growing and reproducing. Common methods using low temperature are freezing and refrigeration. Can extend shelf life for long periods of time
• High temperature

  Eliminates or significantly reduces growth of microbes. Can eliminate spores (sterilization). May cause changes in food quality including its texture and nutrients
• Nitrite

  Antimicrobial that is used to inhibit the growth and reproduction of Clostridium botulinum and gives the characteristic flavour and colour of meat
• Antioxidants

  Prevent or slow down spoilage caused by oxidation such as lipid oxidation. Helps to maintain flavour, and colour of foods. Example of foods using antioxidants for preservation are nuts
• Dehydration

  1. Moisture is lost from the apples and the apples become higher in solid content (lowering water activity) so there is no available water for microbes to grow

  2. Water activity is one of the crucial factors of microbial growth. Low water activity means there is less free water so they cannot grow

  3. Dehydration results in concentrated flavour and longer shelf life. The apples can be sundried to become crisps
• Adding sugars

  Sugar binds to water molecules within the food (lowering a=water activity). Microbes do not have access to free water for growth. Sugar incorporated into the food also draws moisture out of microbial cells eventually leading them to death. An example would be turning the apple into a jam that is high in sugar content
• Adding acids

  This creates an unfavourable environment for microbial growth as it denatures proteins for metabolic processes. A method which incorporates this is pickling. The apples can be treated with vinegar or brine
• The preferred method is dehydration with the addition of sugars. Dehydration results in longer shelf life and concentrates the flavour of the apples. Adding sugars like maple syrup can improve the flavour of the apples by making it more sweeter
• Advantages of food preservation

  • Enhances shelf life
  • Reduces food waste
  • Seasonal availability
  • Food security
• Disadvantages of food preservation

  • May result in loss of nutritional value
  • May contain salts or sugars which is not ideal for those who need to restrict their intake
  • Flavour or freshness may not be the same
• Causal factors for food deterioration

  • Microbial load
  • Physical damage
  • Oxidation
  • Environmental factors
  • Enzymatic activity
• pH

  The growth of most microbes is inhibited at high acidity levels (pH below 4.6). Acidity can cause denaturation of enzymes necessary for metabolic processes fueling their growth and reproduction. Different microbes are active at different levels of pH above 4.6
• Antioxidants

  Prevent lipid oxidation that causes discolouration and off-putting flavours
• Post-harvest management

  System for handling, storing, and transporting agricultural goods after harvest
• Strategies to reduce food loss in a food supply chain

  • Temperature control
  • Storage conditions
  • Packaging and handling
  • Transportation logistics
  • Lack of infrastructure or resources
  • Knowledge or training
• Factors affecting post-harvest quality

  • Microbiological (Microorganisms that cause spoilage, Enzymes)
  • Environmental (Temperature, Oxygen, Humidity, Light)
  • Physical (Improper storage, Improper handling)
• Components of a post-harvest management system

  • Technical activities (Harvesting, cleaning, storage, processing)
  • Economic activities (Nutrition, quality control, marketing, transportation)
• Food supply chain

  Activities in the process of getting food from farm to table
• Food supply chain management (FSCM)

  System of actively monitoring and optimising activities within the food supply chain
• Importance of food supply chain management

  • Food security
  • Food safety
  • Reduces waste
  • Sustainability
  • Cost efficient
• Ways food preservation contributes to sustainable agriculture and food security

  • More food, less waste
  • Seasonal availability
  • Wider market, better livelihoods
  • Eco-friendly
  • Climate resistance
• Ohmic heating

  Alternating electrical current passes through the food product which acts as a resistor in the circuit. Due to resistance, the electrical energy is converted into heat energy. Ohmic heating generates heat from within the food unlike microwave heating (a traditional method) that provides heating from outside in
• Advantages of ohmic heating

  • Faster and more uniform heating
  • Reduces the occurrence of 'cold spot'
  • Reduces the thermal impact on nutrients and flavour of the food product
  • Can heat low-moisture foods effectively
• Pasteurization

  Affects the physical and sensory attributes of foods. Liquids like milk and juices can become slightly thick caused by protein denaturation. Foods like fruits and vegetables can become softer in texture. Some vitamin loss is possible especially Vitamin C which is susceptible to loss. Slight change in taste and aroma is possible due to heat-sensitive aroma components
• Mechanism of microorganism inhibition by heat treatment

  • Protein denaturation
  • Melting of lipids
• Cold point

  The slowest-heating point of a food product undergoing thermal processing. It is the point the processing conditions must be applied to to ensure maximum effectiveness of the heat treatment such as canning (a sterilisation method)
• Sterilization

  Completely eliminates all microorganisms, including spores
• Pasteurization

  Reduces the number of viable microorganisms to a safe level, but does not eliminate all microorganisms, including spores
• Mechanism of microorganism inhibition by heat treatment

  1. Protein denaturation

  2. Melting of lipids
• Cold point

  The slowest-heating point of a food product undergoing thermal processing
• Sterilization

  Eliminates all microbes including spores so food product has longer shelf life at room temperature
• Pasteurization

  Does not eliminate all microbes, requires refrigeration to prevent spoilage from the surviving ones
• Pasteurization methods

  • Ultra High Temperature (UHT)
  • Low Temperature Long Time (LTLT)
• Sterilisation uses high temperatures so that there are no spoilage or pathogenic microogranisms in food products until consumption
• Clostridium botulinum spores can grow in low acid (pH above 4.6) in stored food products
• Sterilisation should be done by using the F0 value (measures effectiveness of the heat treatment, usually 121.1 degrees Celsius) of 3