vitamins lecture 11-08-10

8/7/2019 Vitamins Lecture 11-08-10

1/49

STRUCTURE, PROPERTIESAND FUNCTIONALITY

11/08/10


2/49

Overview of vitaminsSources & FunctionBioavailability

Individual vitaminsStructure & Properties

Vitamin stability to processingmethods


3/49

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


4/49

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

4


5/49

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


6/49

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)


7/49

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.


8/49

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.


9/49

The proportion of the quantity ofvitamins ingested that undergoesintestinal absorption andutilization by the body.


10/49

Diet composition

Physical characteristics of food

Forms of vitamins

Interactions with other diet components


11/49


12/49

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


13/49

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


14/49

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)


15/49

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


16/49

-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


17/49


18/49

Retinol


19/49

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


20/49


21/49

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


22/49


23/49

Occurs as free form in milk

Bound to phosphate in other foods

Destroyed by alkaline conditions, light andexcessive heat

Stable to air and acids


24/49


25/49

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


26/49


27/49

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


28/49


29/49

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


30/49


31/49

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


32/49


33/49

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


34/49


35/49

Small losses due to interaction with Vitamin C

Reacts with sulfydryl compounds in thepresence of oxygen in milk

Generally stable


36/49


37/49

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


38/49

Vitamin D2 Vitamin D3


39/49

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


40/49


41/49

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


42/49


43/49

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


44/49

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


45/49

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


46/49

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


47/49

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


48/49

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


49/49

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)

vitamins lecture 11-08-10

Documents