Please enable JavaScript.

Coggle requires JavaScript to display documents.

Week 13: Food Additives, image - Coggle Diagram

- - - - Buffering
      - pH adjustment
        
        adjust to higher pH values to achieve more stable or more desirable characteristics
        
        used to neutralise excess acid in the production of cultured butter
      - CO2 evolution, e.g. carbonate and hydrogen carbonate salts
    - - Organic and inorganic acids occur extensively in natural systems where they function in a variety of roles ranging from intermediary metabolites to components of buffer systems
      - Functions
        
        Sour and tart taste
        
        Lower pH, e.g. citric acid in acidic fruits and vegetables
        
        Chemical leavening
        
        Composed of compounds that react to release gas in a dough or batter under appropriate conditions of moisture and temperature
        
        At elevated temperature, e.g. baking, the released gas, together with expansion of entrapped air and moisture vapour, imparts a characteristics porous, cellular structure to finished goods
        
        CO2 is the only gas generated from currently used chemical leavening systems
        
        CO2 is derived by the action of leavening acid on a carbonate or hydrogen carbonate salt
        
        Common leavening salts: NaHCO3, (NH4)2CO3 and NH4HCO3
        
        (NH4)2CO3 and NH4HCO3 decompose at baking temperatures and thus do not require, as does NaHCO3, an added leavening acid for functionality
        
        Acidic microbial inhibitors, e.g. benzoic acid and sorbic acid
        
        Chelating agents, e.g. ascorbic acid and citric acid
        
        Setting of pectin gel
        
        De-foaming agents and emulsifier
        
        Coagulation of milk proteins, e.g. lactic acid
        
        Induce limited hydrolysis (inversion) of sucrose to fructose and glucose in the manufacture of fondant and fudge, e.g. potassium acid tartrate
  - - - EDTA salts (to 500 ppm) can function in the aqueous phase and at the interface between the aqueous and fat phases, and thus are very effective antioxidants in emulsion systems, such as salad dressings, mayonnaise, and margarine
      - used extensively as a stabilizing agent in the food industry. Food spoilage is often promoted by naturally-occurring enzymes that contain transition-metal ions. These enzymes catalyze the chemical reactions that occur during spoilage.
      - deactivates these enzymes by removing the metal ions from them and forming stable chelates with them. It promotes color retention in dried bananas, beans, chick peas, canned clams, pecan pie filling, frozen potatoes, and canned shrimp.
      - improves flavor retention in canned carbonated beverages, salad dressings, mayonnaise, margarine, and sauces. It inhibits rancidity in salad dressings, mayonnaise, sauces, and sandwich spreads. EDTA salts are used in foods at levels ranging from 33 to 800 ppm
  - - - exerts both beneficial and detrimental effects in foods
        
        Detrimental effects include:
        
        Loss of nutritive values via degradation of lipids, vitamins and pigments
        
        Loss of food colour via degradation of pigments
        
        Development of off-flavours
        
        Control of undesirable oxidation reactions in foods usually achieved by employing processing and packaging techniques that excludes oxygen or involve the addition of appropriate chemical agents
  - - - Sulfites & SO2
        
        Actions
        
        Inhibits non-enzymatic browning
        
        Inhibits enzyme catalysed reactions
        
        Inhibits and controls the growth of microorganisms
        
        Acts as antioxidant and reducing agent
        
        Commonly used SO2 gas
        Na2SO3, K2SO4 and CaSO3
      - Nitrites & nitrates
        
        Nitrite rather than nitrate is functional constituent
        
        Potassium and sodium salts of nitrite and nitrate are commonly used in curing mixtures for meats to develop and fix colour
        
        Functions
        
        Develop characteristics flavours
        Nitrite contributes to cured meat flavours through an antioxidant role, but its chemistry is poorly understood
        
        Develop and fix colours
        Nitrite in meat forms nitric oxide, which reacts with heme compounds to form nitrosomyoglobin (pigment responsible for the pink colour of cured meat)
      - Sorbic acid: Medium chain and longer, monocarboxylic, aliphatic fatty acids exhibit antimicrobial, especially antimycotic (destroys growth of fungi) activities, especially the α-unsaturated acids
        
        CH3-CH=CH-CH=CH-COOH
        
        Functions in foods
        
        Inhibit mold and yeast growth in cheese, baked products, fruit juices, wine and pickles
      - Benzoic acid
        
        Naturally present in cranberries, prunes & cloves
        
        Undissociated acid is the active form
        
        Optimal activity at pH 2.5-4.0
        
        Little activity in foods with pH > 5.2
        
        Suitable for use in acid foods, eg. fruit juice, carbonated beverages & pickles
        
        Once in a suitably acidic product, much of the salt converts to the active protonated form
        
        K & Na benzoate salts are generally used as they are readily dispersed into aqueous foods
        
        Most effective against yeasts & bacteria and least effective against molds
        
        Used in combination with sorbic acid or parabens
        
        Levels range from 0.05 to 0.1% by wt
      - Parabens
  - - - Peptides
        
        Aspartame: Dipeptide sweetener
        
        ~ 180-200 times sweeter than sucrose
        
        Noted for clean sweet taste
        
        First approved in the United States in 1981
        
        Now is approved for use in over 75 countries
        
        Technical Disadvantages
        rate of loss of sweetness is gradual and depends on the temperature and pH
        
        Unstable under acidic conditions
        
        Rapid degradation at elevated temperature
        
        peptide nature of aspartame makes it susceptible to hydrolysis, and this feature also permits other chemical interactions and microbial degradations
      - Chlorosaccharides
        
        Sucralose: Noncaloric sweetener produced by the selective chlorination of the sucrose molecule
        
        ~ 600 times sweeter than sucrose
        
        Sucralose possesses a sweetness time-intensity profile similar to sucrose
        
        Exhibits no bitterness or other unpleasant aftertastes
        
        Benefits
        
        High degree of crystallinity
        
        High water solubility
        
        Very good stability at high temperatures
        
        Excellent ingredient for bakery applications
        
        Quite stable at the pH of carbonated soft drinks
        
        Extensive studies have generally demonstrated that the substance is safe at the expected usage levels.
      - Sulfoamides
        
        Saccharin: Free form or as salt of Na & Ca
        
        ~300 times as sweet as sucrose in conc up to the equivalent of a 10% sucrose solution
        
        Ranges from 200 to 700 times the sweetness of sucrose depending on the concentration & food matrix
        
        Exhibits bitter & metallic aftertaste, which becomes more evident with increasing concentration
- - - - is important to many foods
        
        It determines the acceptability of food
        
        Colour may provide an indication of chemical changes in a food such as browning and caramelisation
      - This includes hues, black, white and intermediates greys
        
        Hues include red, orange, yellow, green, blue and violet
      - This is only a small portion of the electromagnetic spectrum
  - - - 4 Pigment Types
        
        Bezopyran derivatives
        
        found in root vegetables and fruits such as berries and grapes
        Responsible for red, blue, and violet colours of many fruits and vegetables
        
        glycosides with benzopyrone nucleus
        
        Flavonoids
        
        low colouring power but may be involved in discoloration
        
        2 more items...
        
        Anthocyanin
        
        High temperature, increased sugar, pH and ascorbic acid can affect the rate of destruction
        
        Artefacts
        
        in syrups and cereal products
        
        Caramels
        
        contain high and low molecular weight coloured compounds as well as a variety of volatile components
        
        Melanoidin
        
        Tetrapyrrole compounds
        
        Hemes: in meat and fish
        
        four pyrrole units joined together into a porphyrin rings the nitrogen atoms are linked to a central iron atom
        
        two pigments
        have globin as the protein portion
        
        Myoglobin (mainly in tissue)
        
        In meat, most of the colour is due to myoglobin
        
        2 more items...
        
        Hemoglobin (mainly in blood)
        
        four myoglobin linked together as a tetramer
        
        1 more item...
        
        Chlorophylls: in green vegetables and leaves
        
        porphyrin rings is in the dihydro form and the central metal atom is magnesium
        
        In many fruits, chlorophyll is present in the unripe state and gradually disappears as the yellow and red carotenoids take over during ripening
        
        is broken down during senescence and the green colour tends to disappear
        
        Loss of green colour during thermal processing: Due to formation of pheophytin and pyropheophytin
        
        1 more item...
        
        Isolated in the chloroplastids
        
        2 types
        
        Chlorophyll b
        
        chlorophyll a
        
        Colour linked to Mg
        
        Mg-free chlorophyll derivatives are olive-brown in colour
        
        Mg-containing chlorophyll derivatives are green
        
        Separation: by polar solvents e.g. acetone, methanol, ethanol. Nonpolar solvents are less effective
        
        Paper chromatography
        
        Thin-layer chromatography
        
        HPLC (most popular)
        
        Isoprenoid derivatives
        
        Carotenoids: widely distributed in animal and vegetable products
        
        not synthesized by animals, but they may change ingested carotenoids into animal carotenoids e.g. in salmon, eggs, crustaceans
        
        Crustaceans contain carotenoids bound to protein resulting in a blue or blue grey colour
        
        When the animal is immersed in boiling water, the carotenoid protein bond is broken and the orange-red colour of free carotenoid appears
        
        Widely distributed in crustaceans is astaxanthin
        
        In ripening fruits, carotenoids increase at the same time chlorophylls decrease
        
        Common examples: α and β carotene and lycopene
        
        β-carotene is often determined in fruits and vegetables as a measure of provitamin A content of food
        
        1 more item...
        
        Two structural groups
        
        Oxygenated xanthophylls
        
        Hydrocarbon carotenes
        
        PHYSICAL PROPERTIES
        
        Soluble in oils and organic solvents (lipophilic compounds)
        
        Moderately heat stable
        
        Undergoes oxidation readily (loss of colour)
        
        Easily isomerised by heat, acid and light
        
        Absorbance at 430 – 480 nm
        
        CHEMICAL PROPERTIES
        
        Carotenoids contain large no. of conjugated double bonds (usually in all-trans configuration)
        
        Easily oxidised when removed from cell tissues
        
        Initial oxidation reaction produces epoxides, carbonyl dioxygenated compounds
        
        Thermal processing (canning) will produce cis-β-carotene
        
        Very high temperature will lead to fragmentation products and volatile products
        
        STABILITY
        
        Relatively stable during storage and frozen
        
        Oxidation of β-carotene increase with sulfite and metal ions
        
        Storage of organic solvents increase oxidation
        
        Fatty acid oxidation by lipoxygenase generates peroxides, which in turn oxidises carotenoids
        
        Sensitive to air: dehydration in the presence of air leads to oxidative decomposition
        
        FUNCTIONS
        
        Photoprotection: Quench and inactivate oxygen species formed by exposure to air and light
        
        Photosynthesis: secondary pigments for harvesting light energy
        
        Nutritional Quality
        
        Precursor of vitamin A
        
        β-carotene has the highest provitamin A activity
        
        May decrease the incidence of cancer in humans
        
        Antioxidative Activity contain large number of conjugated double bonds which are easily oxidised
      - BETALAINS
        
        Water soluble pigments including
        
        Betacyanins (red)
        
        Betaxanthins (yellow)
        
        Factors affect stability of betalains
        
        Heat or acid
        
        Degrades under acidic conditions
        
        Degrades under mild alkaline conditions
        
        Best stability at pH 4-5 and at low moisture
        
        Betalains oxidation increase with oxygen and light
        Ascorbic acid and isoascorbic acid improve stability
        Oxidation does not involve singlet oxygen or superoxide. Therefore, any antioxidants that inhibits free-radical oxidation does not inhibit oxidation of betalains e.g. phenolic antioxidants, sulphur-containing antioxidants
        
        TANNINS Polyphenolic compounds present in many fruits
        
        Important as colour compounds and also for their effect on taste as a factor in astringency
        
        Oxidation and polymerisation of phenolic compounds as a result of the enzymic activity of phenoloxidases or peroxidases may result in the formation of brown pigments
        
        May occur during the growth of the fruits or during mechanical damage in processing
- - - - aroma components: volatiles that are detected by the specialised cells of the olfactory epithelium in the nasal cavity.
      - taste :check:
        
        Compounds that contribute to flavour perception (taste sensations) are usually
        
        Water soluble
        
        Relatively non-volatile
        
        Usually in high concentrations
        
        Four main taste sensations
        Have receptors on the tongue for each taste and have specificity
        
        Sweet and bitter tastes are related from a molecular structure-receptor relationship
        triggered by similar features on the molecule i.e. sugar structures possess features that interact with sweet and/or bitter receptor
        
        Sweet: – a compound must contain a H-bond donor (AH), and a Lewis base (B), separated by 0.3 nm. AH-B unit of a sweetener binds with a corresponding AH-B unit on the biological sweetness receptor
        
        bitter: vary with genetic make-up of a population
        
        Quinine, an alkaloid, is used as a standard for bitter taste sensation
        
        Threshold is 10ppm
        
        General characteristics
        
        Less soluble in water than other taste sensations
        
        Lower taste threshold than other taste sensations
        
        in foods
        
        Citrus industry
        
        1 more item...
        
        Beverages
        Caffeine in coffee and cola, 150-200 ppm
        Theobromine in cocoa
        
        Protein hydrolysate
        
        1 more item...
        
        Salty
        
        have complex tastes and difficult to describe
        
        Na and Li produce only salty tastes, K and other alkaline earth cations produce salty and bitter tastes
        
        Sour
        
        Other taste sensations
        
        Pungency: collection of hot, sharp & stinging sensations
        
        Pungent & volatile foods e.g. mustard, horseradish, vegetable radishes, onions, garlic, and watercress.
        
        Pungent & nonvolatile foods e.g. chilli peppers, black peppers & ginger
        
        The active compound in chilli peppers is capsaicinoids.
        
        Spice and clove are aromatic spices which contain eugenol as the active ingredient
  - - - Threshold concentration is the concentration of flavour where at least half of the panel can detect
        
        Odour unit (OU) = concentration present/threshold concentration
  - - - Yeast hydrolysates contain 5’-ribonucleotides
      - Maltol and ethyl maltol are commercial flavour enhancers of sweets and fruits
        
        Maltol and ethyl maltol are sweetness enhancers. Both compounds can fit the AH-B portion of the sweet receptor
  - - - Allium – strong penetrating aromas e.g. onions, garlic, leek, chives, and shallots
        
        Allium sulphur-containing volatiles
        Released when the tissues are damaged and the enzymes are in contact with the precursors
      - Cruciferae e.g. cabbage, turnips, horseradish, broccoli, watercress, and brown mustard
        
        formed through enzymatic process when the tissues are disrupted or cooked
        The flavour compounds are mainly isothiocyanates
        Allyl isothiocyanate is the source of pungency and aroma of horseradish and black mustard
    - - Enzyme catalysed oxidation of fatty acids produce pleasant fruity flavours
      - Aromas derived mainly from medium chain-length (C6-C12) fatty acids by β-oxidation
      - Enzyme catalysed reaction are more specific than autoxidising reaction
    - - Branched-chain amino acids are precursors for the biosynthesis of fruity flavours e.g. bananas and apples
        The reactions are enzyme-catalysed
    - - The flavours (aromas) of citrus fruits are mainly aldehydes and terpenes
      - -Sinensal is important for the ripe orange-citrus flavours
      - The flavour of lemon is due to several terpene ethers
    - - Trimethylamine has been associated with fish and crab-like aromas (ammoniacal and fishy)
      - Trimethylamine and dimethylamine have stale fish aroma
      - Trimethylamine oxide is converted to trimethylamine and dimethylamine by an enzyme degradation reaction
      - Fresh fish do not have trimethylamine, but has aldehydes, ketones and alcohols – similar to those produced by plant lipoxygenase
      - Flavour of cooked snow crab meat consists of 12 amino acids, nucleotides and salt ions.
    - - Flavours developed during processing or cooking depend on
      - Precursors, temp, time, and water activity
      - Browning reaction is associated with flavour development e.g. nutty, meaty, roasted, toasted, burnt, floral or caramel flavours
      - Distinctive profile of flavours compounds can be made using selected ingredients e.g. sugars, amino acids and sulphur compounds