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Module 2 Minerals


Mineral absorption decreased by fiber. Phytate (in fiber) forms insoluble complexes with Fe & Zn interfere with ... causing formation of fiber-bound Ca in ... – PowerPoint PPT presentation

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Title: Module 2 Minerals

Module 2Minerals
  • Food Chemistry 2
  • ND Food Technology

Table of Contents
  • Introduction
  • Major minerals
  • Trace elements
  • Metal uptake in canned foods

1. Introduction
  • Minerals may be present in food as
  • Inorganic salt
  • Organic salt
  • Combined with organic materials (e.g. phosphorus
    combined with phosphoproteins, metals combined
    with enzymes)
  • Can be over 60 elements present in food
  • Divide minerals into groups

1. Introduction
1. Introduction
  • Mineral content determinned by incineration
    (ashing) in muffle oven/microwave furnace
  • To destroy organic compounds, leaving minerals

1. Introduction
  • Different methods temperatures of incineration
    give different results
  • Organic anions disappear
  • Metals changed to their oxides
  • Carbonates may be result of decomposition of
    organic material
  • Some trace elements salts may be lost by
  • Sodium chloride lost if incineration tempgt600C
  • Abundance of certain element (e.g. in soil) ?
    increase level of mineral in plant/animal
  • Enrichment of minerals (e.g. murcury in fish)

2. Major minerals
  • Monovalent minerals present in food as soluble
    salts in ionized form (e.g. in apple cations
    Na, K anions Cl-, S-)
  • Polyvalent minerals present in form of
    equilibrium between ionic, dissolved, nonionic,
    colloidal (e.g. milk, meat)
  • Metals also in form of chelates
  • Metal complexes formed by 2/more covalent bonds
    between a ligand metal cation
  • A ligand is a group bonded to a central atom in a
    complex (capable to donate electron pairs to
    metal ion)
  • Ligand functions as Lewis base metal functions
    as Lewis acid

2. Major minerals
  • Chelate stability
  • More stable when ligand is more basic
  • Depends on nature of metal ion (elecronegativity)
  • Decreases with decrease in pH
  • Formation of chelates can be ring systems (e.g.
    chloropyll 6-membered ring)
  • Metals can form chelates with donor atoms (N, O,
    P, S) or donor groups (NH2, COOH, CO)
  • Examples of chelates in food
  • Hemoglobin, myoglobin, VitB12, calcium caseinate

2. Major minerals
  • Sodium concerns
  • NB for flavour acceptability of food
  • Concerns about sodium cause human hypertension
  • Recommended daily intake 0.5g, but humans use a
    lot more
  • Suggested replace salt with mixture of sodium
    chloride potassium chloride
  • Mineral absorption decreased by fiber
  • Phytate (in fiber) forms insoluble complexes with
    Fe Zn ? interfere with absorption of Ca by
    causing formation of fiber-bound Ca in intestines

2. Major minerals
  • Minerals in milk
  • Depends on feed, season, breed, stage of
    lactation, udder infections
  • Mineral content constant at 0.7
  • Milk contains much more potassium than blood
  • Some minerals in milk present at levels beyond
    solubility thus in colloidal form (e.g. Ca, Mg,
    phosphate, citrate)
  • Coloidal minerals removed by
  • Precipitation with curd when milk is coagulated
    with rennin
  • ultrafiltration

2. Major minerals
  • Minerals in meat
  • Mainly sodium (in extracellular fluid of muscle)
    potassium, phosphorus, magnesium (intracellular
  • Nonsoluble minarals associated with proteins
  • Leaner meat ? higher mineral content
  • Drip loss ? sodium mostly lost
  • Processing does not reduce mineral content of meat

2. Major minerals
  • Cured meats may have increased sodium, because
    cured in brine (sodium chloride/potassium
  • Ionic equilibria NB in water-binding capacity of
  • Normal pH (5.5) of rigor is close to iso-electric
    point of actomyosin
  • Thus net charge on protein at minimum water
    binding also at minimum
  • Addition of acid/base ? cleavage of slat
    cross-linkages ? electrostatic repulsion
    increases ? loosens protein network ? more water
    can be taken up
  • Addition of salts (sodium chloride to meat
    increases water-holding capacity

2. Major minerals
  • Struvite
  • Or magnesium-ammonium-phosphate
  • Usually mistaken for broken pieces of glass in
    canned seafood
  • Mg of seawater ammonia forms struvite by the
    effect of heat on fish muscle protein

2. Major minerals
  • Minerals in plants
  • Potassium, sodium (only trace element),
    phosphorus, Ca, Mg, sulfur
  • Minerals in wheat all concentrated in bran/areas
    close to bran coat
  • Ash content in flour related to quality (the
    higher the ash content, the darker the colour)
  • High grade patent flour (pure endosperm)
    0.3-0.35 ash, wholewheat meal 1.35-1.8 ash
  • Also influenced by rainfall, soil conditions,
  • Soybeans
  • 5 ash mostly potassium phosphorus
  • Phosphorus in form of phytic acid
  • Phytates NB effect on protein solubility
    interfere with absorption of Ca in diet

3. Trace elements
  • Present in all foods from
  • uptake from soil (absorption through roots),
  • feed (e.g. milk),
  • contamination from processing (metal pickup from
    packaging/equipment, nickel in milk from
    stainless steel tanks)
  • Industrial air pollution, fertilizers, chemicals,
    sewage sludge (nitrogen phosphate)
  • Abundance depends on abundance in environment
  • Very high concentrations may lead to sclerosis
  • Aluminium (used in packaging, utensils, food
    additives) may cause Alzheimers disease

3.1. Cobalt
  • Only metal containing VitB12 Marmite!
  • In corn, legumes, cereals
  • Human requirement small, no deficiencies

3.2. Copper
  • Present in foods as part of enzymes (e.g.
  • Powerful prooxidant catalises oxidation of
    unsaturated fats, oils ascorbic acid

3.3. Iron
  • Component of heme pigment enzymes
  • Iron deficiencies in population disappearance
    of iron equipment in processing plants
  • In animal liver well absorbed, veg eggs not
    well absorbed
  • Absorption depends on form
  • Ferrous sulphate well absorbed, but will
    discolour/oxidize food to which its added
  • Elemental iron well absorbed not change food
    (added to enrich flour)
  • The meat factor amino acids from digestion can
    chelate nonheme iron ? the complexes formed can
    facilitate absorption of iron

3.4. Zinc
  • 2nd most NB mineral for humans
  • Stimulates activity of enzymes promote biochem.
    reactions in body, helps heal wounds, sense of
    taste smell
  • Abundant - deficiencies unknown
  • In beans, nuts, whole grains, dairy products
  • Zinc poisoning acid foods (fruit juice) stored
    in galvanized containers ? zinc dissolves

3.4. Manganese
  • In wide range of foods, but not easily absorbed
  • High concentration in germ and bran of wheat
  • Associated with activation of some enzymes
  • Maintains blood sugar levels

3.5. Molybdenum
  • Plays role in enzymes (e.g. aldehide oxidase,
    sulfite oxidase, xanthine oxidase)
  • In cereal grains, leafy veg (rich in
    chlorophyll), animal organs
  • Contents in food varies

3.6. Selenium
  • Bound to organic molecules (bound to proteins in
  • Protects against liver necrosis, works as
    antioxidant (protects against cancer)
  • Most active form is selenite
  • Volatile can be lost during processing
  • In nuts (Brazil nuts), tuna, grains

3.7. Flourine
  • plays a role in the development and health of
    bones and teeth
  • In veg (spinach), milk, fish, flouridated tap

3.8. Iodine
  • High levels in fish shellfish
  • NB for functioning of thyroid gland - deficiency
    leads to goiter

3.8. Nickel
  • Legumes, nuts, cocoa, shellfish, hydrogenated
    fats (mostly plants)

3.9. chromium
  • In wheat (flour)
  • Refining processing lead to loss in chromium,
    but can also leach into food product from
    stainless steel equipment
  • Needed for sugar metabolism maintain blood
    sugar level
  • Dietery intake suboptimal in most people can
    lead to nutritional problems

3.10. Silicon
  • High in foods from plant origin (unrefined
    grains, cereal products, root crops)
  • Required, along with VitC, for collagen
    formation, prevention of osteoporosis

4. Metal uptake in canned foods
  • Canned foods take up minerals from container
  • Tin iron from the tin plate
  • Tin and lead from the solder
  • In acid foods canned in the absence on O2, tin
    forms the anode of the tin-iron couple ? tin goes
    slowly in solution ? protect product for 2 years
    or longer
  • Rapid detinning
  • When iron forms the anode ? in presence of
    oxidizing agents dissolution of tin is
    accelerated ? after all tin is in solution, H2
    forms ? can swells ? can becomes a springer
  • Spinach, greenbeans, tomato, veg soups, fruit

4. Metal uptake in canned foods
  • Sulfide staining (in pork, fish, peas)
  • When food contains sulphur containing amino acids
    (cysteine, methionine)
  • Upon heating ? reduction ? sulfide ions form ?
    react with tin iron ? SnS FeS ? sulfide stain
  • Type of tin plate size of crystals in tin
    coating effects corrosion resistance
  • Tin can preserve light colour of food (wax beans)
  • Iron can darken food
  • Black compound of iron (dissolved from can)
    rutin (flavonol extracted from the food) in
    all-green asparagus
  • Black colour forms after iron is oxidized to the
    ferric state
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