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STRUCTURE, PROPERTIESAND FUNCTIONALITY
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Overview of vitaminsSources & FunctionBioavailability
Individual vitaminsStructure & Properties
Vitamin stability to processingmethods
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A vitamin is an organic compound requiredas a nutrient
A compound is called a vitamin when itcannot be synthesized in sufficient quantitiesby an organism
Vitamins are defined by their biologicalactivity, not their structure
Vitamins are usually classified as watersoluble or fat soluble
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Vitamins can be classified as eitherWater soluble (Vitamin B and C)Fat soluble (Vitamin A, D, E, K)
Water soluble vitamins are generally involvedin the cellular metabolism of energysupplying nutrients.
Fat soluble vitamins often have veryspecialized functions
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Vitamin A Vitamin B1 (Thiamin) Vitamin B2 (Riboflavin) Vitamin B3 (Niacin) Vitamin B5 (Pantothenic acid) Vitamin B6 (Pyridoxine) Vitamin B7 (Biotin) Vitamin B9 (Folic acid) Vitamin B12 (Cyanocobalamin) Vitamin C (Ascorbic acid) Vitamin D Vitamin E Vitamin K
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Coenzymes or their precursors Niacin, thiamin, riboflavin, biotin, pantothenic acid,
B6, B12 and folate
Antioxidants Ascorbic acid, certain carotenoids, vitamin E
Genetic regulation Vitamins A and D
Specialized functions Vitamin A (vision), Vitamin C (hydroxylation
reactions), K (carboxylic reactions)
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Recommended daily allowance (RDA):
The average daily dietary intake level that issufficient to meet the requirement of nearly
all (97-98%) apparently healthy individuals ina particular life stage and gender group.
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RDA have been publishedfor Vitamin A, D, E, K, B1,B2, B3, B6, B9, B12 and C
Reference adequate intake(AI) provided for VitaminB5 (Pantothenic acid) andB7 (Biotin), instead of RDA.
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The proportion of the quantity ofvitamins ingested that undergoesintestinal absorption andutilization by the body.
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Diet composition
Physical characteristics of food
Forms of vitamins
Interactions with other diet components
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Vitamin Acid Alkali Light Air Heat
Vitamin A U S U U U
Ascorbic Acid (C) S U U U U
Biotin (B7) S S S S U
Vitamin B12 S S U U S
Vitamin D S U U U U
Folate (B9) U U U U U
Vitamin K U U U S S
Niacin (B3) S S S S S
Vitamin B6 S S U S U
Riboflavin (B2) S S U S U
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Vitamin Food DeficiencyVitamin ARetinol
Liver, fortified Milk Night blindness;Xerophthalmia
Vitamin D Egg Yolk, Milk, Exposureto sun enables body tomake its own Vitamin D.
Rickets
Vitamin E Corn or Cottonseed Oil,Butter, Brown Rice,Soybean Oil, Vegetableoils such as Corn,Cottonseed or Soybean,
Nuts, Wheat Germ.
Rare, seen primarily inpremature or low birthweight babies or childrenwho do not absorb fatproperly.
Vitamin K Green Vegetables, Liver,also made by intestinalbacteria.
Defective bloodcoagulation
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Nutritional deficiency
Vitamin Food DeficiencyB1 Thiamin Meat, pork, liver, whole
and enriched grainsBeri-beri muscleweakness and paralysis
B2 - Riboflavin Meat, liver, milk, greenvegetables, enrichedgrains
Skin disorders andanaemia
B3 Niacin Milk, meat, enrichedgrains
Pellagra Diarrhoea,Dermatitis, Dementia,Death
B5 Pantothenic Acid Beef, poultry, wholegrains, potatoes, broccoli
Fatigue, GI distress,Burning Feet
B6 Meat, poultry, fish,legumes, soy
Depression, convulsions
B7 - Biotin Egg yolks, lots of otherfoods
No major
B9 - Folate Dark leafy veg, fortifiedfoods
NTD
B12 - Cobalamin Milk, fish, poultry,
shellfish (animal)
Pernicious anemia,
fatigue (vegans)
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Restoration: replacement, in full or in part, of vitaminlosses incurred during processing
Fortification: addition of vitamins to food that are suitablecarriers of vitamins, which do not necessarily contain the
vitamin naturally
Enrichment: addition of vitamins above initialnatural ;levels to make a product more marketable
Standardization: addition redesigned to compensate fornatural fluctuations in vitamin content
Nutrification: the addition of vitamins to formulated orfabricated foods marketed as meal replacers
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-carotene Colorants
Vitamin E Antioxidants
Lipid systems
Vitamin C Antioxidants
Lipid systems Inhibits can corrosion Stabilizes color andflavor of wine Prevention of black
spot in shrimps Stabilization of cured
meat color Dough improvement in
baked goods Reducing agents
Prevents enzymaticbrowning
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Retinol
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Present in animal foods as retinol and beta-carotenes in plant foods
Double bonds present make it susceptible tooxidation
Attacked by peroxides and free radicals fromlipid oxidation
Catalyzed by traces of copper and iron Negligible loss due to leaching Heat converts it to a form of lower potency
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Present in animal and plant tissues in free orbound forms
Destroyed by sulfur dioxide in sulpfited fruitsand vegetables
Destroyed by enzymes thiaminase andpolyphenoloxidase (PPO)
Substantial losses due to leaching and driplosses
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Occurs as free form in milk
Bound to phosphate in other foods
Destroyed by alkaline conditions, light andexcessive heat
Stable to air and acids
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Occurs as nicotinamide and as nicotinic acid
Bound to polysaccharides and peptides
Not available in many cereals unless liberatedby heat or alkaline conditions
Synthesized from amino acid tryptophan
Generally stable
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Stability in acid and calcium salt highlydependent on pH
More stable at alkaline pH Unstable to autoclaving Unaffected by atmospheric oxygen and light Susceptible to leaching during blanching and
home cooking
Loss of
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Pyridoxine, pyridoxal and pyridoxamine
Free form in milk, bound state in other foods
May be deficient in some diets
Lost by reaction with SH2 groups of proteinsand amino acids when heated or duringstorage
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Dry crystalline form stable to heat and oxygen Gradually destroyed by UV Acidic or alkaline solutions more heat labile Abundance usually low in natural foodstuffs Animal products: mostly in protein-bound form
May be freed by strong acid hydrolysis at elevatedtemperature
Freed by proteolytic enzyme Plant foods: water-extractable form
Susceptible to leaching during washing and blanching
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Occurs in various forms
Most abundant in dark green leaves, liver andkidney
One of main causes of deficiency diseases indeveloped countries affecting pregnant
women, pre-term infants and the elderly
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Small losses due to interaction with Vitamin C
Reacts with sulfydryl compounds in thepresence of oxygen in milk
Generally stable
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Occurs as both ascorbic and dehydroascorbicacid (heat labile)
Very soluble and most labile of vitamins Readily lost by leaching and drip losses
(substantial loss during processing)
Destroyed by plant enzymes Copper and iron catalyze oxidation in air Sulfur dioxide protects against oxidation
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Vitamin D2 Vitamin D3
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Occurs in foods as cholecalciferol (D3)
Produced in the skin under influence of UVlight
Synthetic ergocalciferol (D2) added to somemilk products, baby foods and margarine
Stable under all normal processing andstorage conditions
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Formerly, thought to occur as eightcompounds: four tocopherols and fourtocotrienols
Activity expressed as -tocopherolequivalents
Naturally occurring antioxidant Lost relatively slowly Generally stable during processing exceptfrying
Destroyed by peroxides
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Insoluble in water but soluble in organicsolvents
Decomposed by UV radiation, alkali, strongacids, reducing agents
Reasonably stable to oxidizing agents andheat
Unaffected by freezing, heat processing(canning) and -irradiation
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Freezing Commercial freezing: pre-freezing, freezing and thawing Main loss occurs during pre-freezing steps Vitamin B9susceptible to freezing Rapid freezing with appropriate packaging minimizes
loss of most vitamins
Inappropriate freezing and ineffective packaging canresult in drip loss of water-soluble vitamins andoxidation of Vitamin A, C and E
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Blanching Steam and microwave blanching most common Significant loss of water-soluble vitamins Inefficient blanching can incur loss of Vitamin C by
oxidation and leaching
Vitamin C stable to heat during blanching Vitamin B1 highly susceptible to heat during
blanching
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Pasteurization and UHT Processing
Milk pasteurization minimal effect on water-soluble vitamins except for Vitamin C
Fruit juice pasteurization inactivates endogenousenzymes minimize oxidation of Vitamin C
Aseptic processing higher content of headspaceoxygen than in package pasteurization
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Dehydration
Sun-drying of fruit, fish, meat and grain Spray-drying of milk, coffee and eggs Steam-heated revolving drums Tunnel drying of fruits and vegetables Freeze-drying of meat
Drying in presence of air result in losses of Vitamin A, -carotene and Vitamin C
Freeze-drying no loss of Vitamin C since carried out inabsence of oxygen
Sun-dry > Drum > Spray-dry ~ Tunnel dry > Freeze-dry
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Canning
Destroys thermo-labile vitamins Destruction rate and extent depends on time/
temperature conditions of process Vitamin B1 and B5 undergo greater loss at lower
retort temperature for longer periods than at highretort temperature for a short time
Vitamin C loss exacerbated by presence of oxygenduring canning
Subsequent low temperature storage improvesretention of vitamins
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Extrinsic parameters Storage temperature Relative humidity Type of container
Intrinsic parameters Dissolved or headspace oxygen pH Water activity Opportunity to leach Prior processing condition (drying, freezing, heat)