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BIODETERIORATION image - Coggle Diagram

- - - - live at 45 to 122 degree Celsius.
      - Optimum temperature is 50 degree Celsius
      - have enzymes that are functional at high temperatures
      - Not pathogens as they cannot grow at body temperature
      - Example bacteria
        
        Clostridium thermosaccharolyticum
        
        Thermoanaerobacterium thermosaccharolyticum
        
        cause spoilage of acid and acidified products such as tomato and other fruit-containing products
        
        also spoilage food containing starchy (farinaceous) ingredients, such as spaghetti.
        
        Geobacillus stearothermophilus
    - - not heat resistant as well as the thermophiles
      - survive in inadequate heated canned foods ( in low acid home canned foods) at 100 degree Celsius.
      - Mostly spoiled foods are Seafoods, meats and evaporated milk.
      - Usually spoiled food by contamination through leakage container
      - Example bacteria
        
        B. subtilis
        
        B. mesentericus
        
        c.pasteuranium
        
        C. sporogenes
    - - known as facultative or psychrotolerant psychrophiles
      - optimum growth temperature is in the mesophilic range, above 15 to 20 degree Celsius, closer to room temperature, but they can also multiply at temperatures below 7 degree Celsius.
      - main microorganism involved in deterioration of refrigeration foods
      - Example bacteria
        
        Microbacterium
        
        Enterobacter
        
        Acinetobacter
    - - optimum growth temperature is low, ( 15 degree Celsius or lower) and maximum growth 20 degree Celsius.
      - Growth at refrigeration temperature
      - Present in arctic and alpine soils, high latitudes, ice formation and deep ocean waters.
      - Most are bacteria or archeas, also fungi and some species of yeast.
      - Example
        
        Alcaligenes
        
        Flavobacterium
        
        Pseudomonas
    - - able to survive pasteurization temperature treatment
      - Example bacteria
        
        Lactobacillus
        
        Bacillus (spores)
        
        Enterococcus
        
        Clostridium (spores)
        
        Micrococcus
  - - - Lactase
        
        formation of lactic acid cause sour and curd taste in milk
      - Catalase
      - Lipase & Lipoxygenase
        
        affecting colour ,texture and flavour in milk
      - Chlorophyllase
      - Polygalacturanase & Pecnitetase
        
        During the ripening of fruit, the activity of this enzymes increases and causes softening of tissue.
      - Amylase
        
        Produce by Bacillus subtilis, Bacillus amyloliquefaciens and Bacillus licheniformis
        
        degrade starch with the effect that the viscosity of the food is reduce as the macro-molecular starch granules broken down into their constituent sugar.
  - - - Caramellization
        
        chemical reaction that takes place involving sugar in food.
        
        pyrolytic reaction
        
        take place 165 degree Celsius
        
        Sucrose has glucose and fructose
      - Maillard reaction
        
        Dextrose has D-glucose unit
        
        result from condensation of an amino group and a reducing sugar at its carbonyl carbon.
        
        non pyrolytic reaction
        
        take place around 140 to 165 degree Celsius
  - - - can act as
        
        Regulatory
        
        control the biochemical process
        
        Specificity
        
        allowing the food processor to change individual food components
        
        catalyst
        
        accelerate the rate of chemical reaction
      - Type of enzyme change
        
        Exogenous enzymes
        
        Food sensory quality is affected by microbial enzymes during food decomposition
        
        Endogenous enzymes
        
        Fruit and vegetable browning and spoilage
        
        Lipid and phenolic oxidation
        
        Lipase & Lipoxygenase in milk
        
        affecting colour, texture & flavour of milk
        
        Lactase in milk
        
        formation of lactic acid cause sour and curd taste
        
        Phenolase
        
        browning
        
        Phospholipate
        
        changes in texture
    - - Type of quality
        
        Sensory quality
        
        Non-enzymatic browning
        
        colour changes
        
        Lipid oxidation
        
        Nutritional quality
        
        vitamins
        
        proteins
        
        lipids
      - Factor affecting chemical change
        
        Light
        
        oxygen concentration
        
        temperature
        
        water activity
    - - Lipid oxidation
        
        Unsaturated fatty acid combine with oxygen during lipid oxidation to create lipid hydroperoxides, which are then degraded into tiny, volatile compounds such as aldehydes ( R-CH=O) and ketones ( R-C-R')
        
        the lipid oxidation mechanism consists of four steps:
        
        propagation
        
        branching
        
        initiation
        
        termination
      - Non - enzymatic browning
        
        Frmation of heterocyclic compounds such as pyrazines and pyrroles will form a brown melanoidin pigments ( brown colour)
      - colour changes
        
        Chlorophylls
        
        Heat and Acid ( Phenophytinization)
        
        Dark colour ( brown)
        
        Heme Pigments
        
        O2 + myoglobin oxymyoglobin ? brown colour