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Week 12: Antioxidants / Sequestrants - Coggle Diagram
Week 12: Antioxidants / Sequestrants
Oxidation
(Involves)
trace metals
in almost all oxidation sensitive foods and serve as pro-oxidation catalysts.
Significantly enhance oxidation in trace levels (Eg copper and iron in fats and oils)
Result: rancidity & off flavour in foods.
Prevented/Inhibited by
Sequestrants or chelating agent:
the food additive used to chelate these metals and is synergist for antioxidants and
antioxidants
Antioxidants STOP free radical propagation. :green_cross:
Mechanism of Antioxidant :green_cross:
Donate H+ to scavenge free radicals O-
The resulting antioxidant-free radical does NOT initiate another free radical.
The antioxidant-free radicals can also react with lipid free radicals
to form stable complex compounds.
as antioxidant free radical has low activation energy.
Natural Antioxidants :check:
Ascorbate salts
Eg. Sodium ascorbate
Widely used in meat product to preserve the colour
Ascorbic acid
present mostly in fruits & vegetables ie. orange
used in beverages eg. soft drinks, fruit juices
Erythorbic acid (d-isoascorbic acid)
stereoisomer of ascorbic acid (vitamin C): same molecular formula, but different 3D orientations of their atoms
Salts of erythorbic acid
Eg. Sodium erythorbate
In meat processing, it increases the rate nitrite reduction to nitric oxide, thus speeding the curing process and retaining the pink color. It also improves flavor stability and prevents the formation of carcinogenic nitrosamines from barbecuing.
Clostridium botulinum produces toxins that cause paralysis which can be life-threatening. Their growth can be prevented by nitrite.
Does not act as vitamin C. Hence cheaper than Vitamin C
Tocopherol (act as Vitamin E)
present mostly in plants.
used at max 0.02% of the fat
applicable for fats, oils, fat containing food & feed products, eg. vitamin E enriched cheese, bread.
EssenRose by Fenchem
an organic rosemary extract
Origanox range by Frutarom
made from oregano, lemon balm, maté
sold in U.S for approx 10 years
used in meat products,
baked goods, dressings etc.
OthersTea polyphenols, blueberries etc
Synthetic Antioxidants (FDA Certified :check:
Butylated hydroxy anisole (BHA)
Made up of 2 isomers:
2-tert-butyl-4-hydroxyanisole
3-tert-butyl-4-hydroxyanisole
Fat soluble, white, waxy solid in tablets or flakes.
Effective in animal products but fairly in vegetable oils & products.
Good carry-through: survive processing and remain stable in food, esp. for baked products.
Best antioxidant for protecting flavour/colour of essential oils.
Also used in packaging materials in the form of wax or emulsion.
Synergistic with acids, BHT, propyl gallate, lecithin etc.
Butylated hydroxy toluene (BHT)
White, water insoluble, crystalline solid.
Less fat soluble and heat stable than BHA.
Inexpensive.
Good carry-through.
Effective in vegetable oil (nuts) when combined with BHA for synergistic effect.
Widely used in industrial applications: petrol, rubber, plastic.
Propyl Gallate
Tertiary ButylHydroQuinone (TBHQ)
White to light tan powder.
Adequate fat & oil solubility.
Most effective antioxidant for most fats & oils esp. highly unsaturated vegetable oil.
Does not react with metal ions to cause discolouration.
Carry-through: Excellent for frying, but poor in baking
improved performance when combined with BHA.
Not permitted to be used with Propyl Gallate.
Sequestrants BIND mineral ions and help prevent oxidation
Complex doesn’t promote oxidation.
Usually form water soluble complexes.
Must be suitable for the product’s
Solubility
Texture
Color
Taste / after taste
Some commercial categories
Carboxylic acids
Citric acid
Calcium citrate
Sodium citrate
Malic acid: More acidic than citric acid
Oxalic acid (made from oxidation of carbohydrates such as glucose using nitric acid)
Succinic acid (obtained from amber by distillation)
Tartaric acid
Polyphosphates
Pyrophosphate
Hexametaphosphate
Amino acids
Glycine
Leucine
Cysteine
Aminocarboxylates
EDTA
Applications
Dairy
Frequently used as stabilisers of flavour & odour.
EDTA
prevents the poor flavour caused by copper-catalysed oxidation and enhances foaming properties of reconstituted skim milk.
Sodium citrate is also used as emulsifier in cheese.
Polyphosphates aid in producing foam in milk proteins.
Vitamins
Vitamins are prone to metals catalysed oxidation.
Sequestrants are excellent stabilisers for vitamins in aqueous systems eg. Carotene, Folic acid, Thiamine & Vitamin B12
EDTA inhibits copper-catalysed oxidation of Vitamin C enriched beverage
beer
EDTA
Inhibit oxidative effects such as haze, cloudiness upon storage.
no contribution of flavour to finished product.
Fruits & Vegetables
Trace metals of Cu, Fe & Cr in canned corn, producing greenish-grey discolouration.
Add EDTA prior to blanching / retorting prevent the off colour.
Similarly for potatoes, yams, cauliflower, asparagus and brussels sprouts.
Sodium metasulfite is a preservative in water-based products and prevent browning. Without EDTA, sodium metasulfite might be used in higher amounts. Some people are allergic to it in various concentration.
What kind of foods will you find antioxidants and sequesterants
Products containing unsaturated fatty acids, especially polyunsaturated fatty acids where:
Lipid content is a major ingredient in the food.
Long shelf-life is desired.
Significant levels of copper or iron are present.
The package permits exposure to light/oxygen.
Oxidation Accelerators :green_cross:
Oxygen
Removing through
Gas (N2, CO2) flush
Vacuum pack (Not useful for all products such as strawberries which can get their texture destroyed due to their softness. Can be used on meat with tough texture)
Exhaust before closing
Used on tin food with headspace before canning. Take out oxygen before the lid of can can go in. Oxygen not only cause oxidation but can cause aerobic microbial growth.
Chemically remove (enzymatic reaction using glucose oxidase)
In canned food
https://pubmed.ncbi.nlm.nih.gov/18330562/
GOX-catalysed reaction removes oxygen and generates hydrogen peroxide, a trait utilised in food preservation.
Oxygen impermeable packages
Oxygen scavengers/ absorbers
Unsaturation (double bonds)
Unsaturated fatty acids are subject to oxidation
Reduce Unsaturation by
Hydrogenation: Making double bonds into single bonds with hydrogen added
Different fat source with different degree of unsaturation (Grapeseed has less unsat than palm oil)
Reduce fat
Heat
lipids still oxidize in the freezer
Metal ions such as copper, iron ions
Some chelating agents to reduce them
Ethylene-Diamine-Tetra-Acetate (EDTA)
Citrate
Phosphates
Free radicals O- with free electrons
Scavenged by Antioxidant
Light
3-Steps mechanism :check:
Initiation
Problems:
Light
Metal ions
Oxygen
Solutions
Modified Atmosphere Packaging (MAP)
Sequestrants in canned food
Singlet oxygen quenchers (Antioxidants) in beverages. Acts as vitamin supplements
Propagation
As problems escalate
solutions to be used together
Antioxidants (free radical scavengers)
Sequestrants (metal ions stabilizers)
Termination
No one cares !
because your product is already PAST the point where it can be sold.
