slide on minerals (food chem)

1. UNIT 5
MINERALS AND VITAMINS
MINERALS AND VITAMINS
Dr. Sudhir Kumar Gupta
Ph.D. IIT Roorkee
1

2. CONTENTS
• Sources and Structures of Minerals and vitamins, Effect of processing and
storage of vitamins, Pro vitamins A and D,Vitamins as antioxidants, Food
pigments & Flavouring agents: types and sources of pigments- their changes
pigments & Flavouring agents: types and sources of pigments- their changes
during processing and storage.
2

3. MINERALS
3

4. • In addition to the major components, all foods contain varying amounts of minerals. The mineral material may be present
as (i) inorganic or organic salts or (ii) may be combined with organic material, as phosphorus is combined with
phosphoproteins and (iii) metals are combined with enzymes. More than 60 elements may be present in foods.
• Minerals Major salt components (K, Na, Ca, Mg, chloride, sulfate, phosphate, and bicarbonate)
•
• Trace elements (usually present in amounts below 50 parts per million (ppm)
1. Essential nutritive elements: which
include Fe, Cu, I, Co, Mn, Zn, Cr, Ni,
Si, F, Mo, and Se.
2. nonnutritive, nontoxic
elements: including
Al, B, and Sn
3. nonnutritive, toxic elements:
including Hg, Pb, As, Cd, and Sb
The minerals in foods are usually
Estimation: The minerals in foods are usually determined by ashing or incineration. the ash does not include the
nitrogen contained in proteins and is in several other respects. Organic anions disappear during incineration, and metals
are changed to their oxides. Carbonates in ash may be the result of the decomposition of organic material. The
phosphorus and sulfur of proteins and the phosphorus of lipids are also part of ash. Some of the trace elements and
some salts may be lost by volatilization during the ashing.
Sodium chloride will be lost from the ash if the incineration temperature is over 600 ⁰C. Therefore, when we compare
data on the mineral composition of foods, we must pay great attention to the methods of analysis used.
4

5. MAJOR MINERALS
1. Some of the major mineral constituents, especially monovalent species, are present in foods as soluble salts
and mostly in ionized form. This applies, for example, to the cations sodium and potassium and the anions
chloride and sulfate.
2. Some of the polyvalent ions, however, are usually present in the form of equilibrium between ionic,
dissolved nonionic, and colloidal species.
3. Metals are often present in the form of chelates. Chelates are metal complexes formed by coordinate
covalent bonds between a ligand and a metal cation; the ligand in a chelate has two or more coordinate
covalent bonds to the metal.
The name chelate is derived from the claw-like manner in which the metal is held by the coordinate covalent
bonds of the ligand. The ligand functions as a Lewis base, and the metal ion acts as a Lewis acid. In a chelate, the
donor atoms can be N, O, P, S, and Cl; some common donor groups are -NH , =C=O, =NH, -COOH, and -OH-
donor atoms can be N, O, P, S, and Cl; some common donor groups are -NH2, =C=O, =NH, -COOH, and -OH-
OPO(OH)2. Many metal ions, especially transition metals, can serve as acceptors of electrons to form chelates
with these donor groups. Formation of chelates can involve ring systems with four, five, or six members. Some
examples of four- and five-membered ring structures are given in Figure 5-1.
An example of a six-membered chelate ring system is chlorophyll. Other examples of food components that
can be considered metal chelates are hemoglobin and myoglobin, vitamin B12, and calcium casemate. A
requirement for the formation of chelates by these polysaccharides is that the OH groups be present in vicinal
pairs.
5

6. 6

7. The stability constant of a chelate is influenced by a number of factors:
a. Basicity of ligand: The chelate is more stable when the ligand is relatively more basic.
b. Nature of metal ion: The chelate's stability depends on the nature of the metal ion and is related to the
electronegative character of the metal.
c. pH: The stability of a chelate normally decreases with decreasing pH.
d. Charge of Ligand. Charged ligands form more stable chelates than uncharged ligands. For example citrate
forms more stable chelates than citric acid.
e. Chemical environment of the donating atom. The relative strengths of metal-ligand bonds are shown
below in decreasing order:
7
Oxygen as donor: H2O > ROH > R2O
Nitrogen as donor: H3N > RNH2 > R3N
Sulfur as donor: R2S > RSH > H2S
f. Resonance in chelate ring: Enhanced resonance tends to increase stability.
g. Stearic hindrance. Large bulky ligands tend to form less stable chelates.

8. Distribution of elements in different plant and animal products:
Some elements appear in plant and animal products at relatively constant levels, but in a number of cases, the
abundance of a certain element in the environment may result in a greatly increased level of that mineral in plant or
animal products. Enrichment of elements in a biological chain may occur; note, for instance, the high mercury levels
reported in some large predatory fish species such as swordfish and tuna.
Interactions with Other Food Components:
The behavior of minerals is often influenced by the presence of other food constituents.
i) It has been shown that mineral absorption is decreased by fiber. A study of the behavior of iron, zinc, and
calcium showed that interactions occur with phytate, which is present in the fiber. Phytates can form insoluble
calcium showed that interactions occur with phytate, which is present in the fiber. Phytates can form insoluble
complexes with iron and zinc and may interfere with the absorption of calcium by causing the formation of
fiber-bound calcium in the intestines.
ii) Iron bioavailability may be increased in the presence of meat. This is the so-called meat factor. It has been
suggested that amino acids or polypeptides that result from digestion are able to chelate nonheme iron.
8

9. Minerals in Milk
• The normal levels of the major mineral constituents of cow's milk are listed below:
• A number of factors influence the variations in salt composition, such as feed,
season, breed and individuality of the cow, stage of lactation, and udder infections.
• The ash content of milk is relatively constant at about 0.7%.
An important difference between milk and blood plasma is the relative levels
of sodium and potassium. Blood plasma contains 330 mg/100 mL of sodium
and only 20 mg/100 mL of potassium. In contrast, the potassium level in milk
is about three times as high as that of sodium.
Some of the mineral salts of milk are present at levels exceeding their
9
Some of the mineral salts of milk are present at levels exceeding their
solubility and therefore occur in the colloidal form. Colloidal particles in
milk contain calcium, magnesium, phosphate, and citrate.
The ratios of the ionic species can be calculated by using the Henderson-Hasselbach equation,
The values for the dissociation constants of the three acids are listed in Table 5-2. When these values are substituted in
the Henderson-Hasselbach equation for a sample of milk at pH 6.6, the following ratios will be obtained:

10. From these ratios, we can conclude that in milk at pH 6.6 no appreciable free citric acid or monocitrate ion is
present and that tricitrate and dicitrate are the predominant ions, present in a ratio of about 16 to 1.
10
This indicates that mono- and diphosphate ions are the predominant species.
The predominant forms are bicarbonates and the free acid.

11. # Soluble complex ions such as Ca-citrate can account for a considerable portion of the calcium and magnesium
in milk, and analogous complex ions can be formed with phosphate and possibly with bicarbonate.
# When milk is heated, calcium and phosphate change from the soluble to the colloidal phase.
# Changes in pH result in profound changes of all of the salt equilibria in milk. Decreasing the pH results in
changing calcium and phosphate from the colloidal to the soluble form.
11

12. Effects of Processing
Mineral elements, unlike vitamins and amino acids, cannot be destroyed by exposure to heat, light, oxidizing agents,
extremes in pH, or other factors that affect organic nutrients. In essence, minerals are indestructible. Minerals can,
however, be removed from foods by leaching or physical separation. Also, the bioavailabilities of minerals may be altered
by the various factors.
# The most important factor causing mineral loss in foods is the milling of cereals. Mineral elements in grain
kernels tend to be concentrated in the bran layers and the germ. Thus, the removal of bran and germ leaves pure
endosperm, which is mineral poor. Similar losses occur during the milling of rice and other cereals. These are
substantial losses. During the fortification of milled products in the United States, iron is the only mineral commonly added.
# Retention of calcium in cheese can be dramatically affected by manufacturing conditions. In cheeses where
the pH is low, substantial losses of calcium occur when the whey is drained. The calcium contents of various kinds of
the pH is low, substantial losses of calcium occur when the whey is drained. The calcium contents of various kinds of
cheese are shown in Table 11. Compositions are expressed both as mg/100 g cheese and as a Ca: protein ratio. The latter
expression gives a better comparison of Ca losses because the water content of cheeses varies from one variety to another.
12

13. Cottage cheese has the smallest calcium concentration because the pH at the time of whey removal is typically
less than 5. In cheddar and Emmenthal cheeses, the whey is normally drained at pH 6.1 and 6.5,
respectively, and this causes the calcium content of Emmenthal cheese to be greater than that of cheddar.
# Since many minerals do have significant solubility in water, it is reasonable to expect that cooking
in water would result in some losses of minerals. Unfortunately, few controlled studies have been done. In
general, boiling in water causes a greater loss of minerals from vegetables than steaming.
# Mineral losses during the cooking of pasta are minimal for iron but more than 50% for
potassium. This is predictable because potassium is present in foods as the free ion while iron is bound to
proteins and other high-molecular-weight ligands in the food.
# Canned foods may take up metals from the container, tin and iron from the tin plate, and tin and lead
from the solder. There are several types of internal can corrosion. Rapid detinning is one of the most serious
problems of can corrosion.
13

14. Factors Affecting the Mineral Composition of
Plant Foods
In order for plants to grow, they must take up water
and essential mineral nutrients from the soil. Once
taken up by plant roots, nutrients are transported to
other parts of the plant. The ultimate composition of
the edible parts of plants is influenced and
controlled by fertility of the soil, genetics of the
plant, and the environment in which it grows (Fig. 9).
Sources of these minerals include fertilizer, decaying
organic materials, and weathering rocks. The degree
to which mineral content can vary even within a
14
organic materials, and weathering rocks. The degree
to which mineral content can vary even within a
plant species is illustrated by wheat grain. For grain
grown in Australia, North America, an the United
Kingdom, zinc concentrations range from 4.5 to 37.2
mg/kg and iron from 23.6 to 74.7 mg/kg .
Fig. 9

15. Factors Affecting the Mineral Composition of Animal Foods
Mineral concentrations in animal foods vary less than mineral concentrations in plant foods. In general, changes in
dietary intake of the animal have only a small effect on mineral concentrations in meat, milk, and eggs. This is because
homeostatic mechanisms operating in the animal regulate tissue concentrations of essential nutrients.
Fortification
Fortification of the U.S. food supply began in 1924 with the addition of iodine to salt to prevent goiter, a prevalent
public health problem in the United States at the time. In 1933, the American Medical Association recommended that
vitamin D be added to milk to prevent rickets. In the early 1940s, food fortification was expanded further when it
became apparent that many young adults were failing Army physical exams due to poor nutritional status. In 1943, the
government issued an order making enrichment of flour with iron, riboflavin, thiamin, and niacin mandatory. Since the
15
government issued an order making enrichment of flour with iron, riboflavin, thiamin, and niacin mandatory. Since the
introduction of fortification back in the 1920s there has been a dramatic reduction in the prevalences of many nutrient
deficiency diseases in the United States, including iron deficiency and goiter. While general improvements in diets were
major factors in this improvement in nutritional status, fortification undoubtedly deserves much of the credit for the low
prevalences of nutrient deficiency diseases in the United States today.
Addition of iron to foods is a difficult balancing act because some forms of iron catalyze oxidation of unsaturated fatty
acids and vitamins A, C, and E.

16. • Trace elements
An element is essential for life if its removal from the diet or other route of exposure to an organism “results in a consistent
and reproducible impairment of a physiological function”
Mineral Food sources Function
Aluminum Low and variable in
foods, component of
some antacids and
leavening agents
Essential nutrient: Possibly essential, evidence not conclusive.
Deficiency unknown.
Leavening agent:As sodium aluminum sulfate (Na 2SO4 .Al2(SO4)3)
Texture modifier
Chemical and Functional Properties of Minerals in Foods
16
leavening agents Texture modifier
Bromine Brominated flour Essential nutrient: Not known to be essential to humans.
Dough improver: KBrO3 improves baking quality of wheat flour.
It is the most used dough improver.
Calcium Dairy products, green
leafy vegetables, tofu,
fish bones
Essential nutrient: Deficiency leads to osteoporosis in later life.
Texture modifier: Forms gels with negatively charged macromolecules
such as alginates, low-methoxypecitns, soy proteins, caseins, etc. Firms
canned vegetables when added to
canning brine.

17. Mineral Food sources Function
Copper Organ meats, sea-foods,
nuts, seeds
Essential nutrient: Deficiency rare.
Catalyst: Lipid peroxidation, ascorbic acid oxidation, nonenzymatic oxidative
browning .
Color modifier: May cause black discoloration in canned, cured meats.
Enzyme cofactor: Polyphenoloxidase.
Texture stabilizer: Stabilizes egg -white foams.
Iodine Iodized salt, seafood, plants and
animals grown in areas where soil
iodine is not depleted.
Essential nutrient: Deficiency produces goiter and cretinism.
Dough improver: KIO3 improves baking quality of wheat flour.
Iron Cereals, leg umes, meat, Essential nutrient: Deficiency leads to anemia, impaired immune response,
Iron Cereals, leg umes, meat,
contamination from iron
utensils and soil,
enriched products.
Essential nutrient: Deficiency leads to anemia, impaired immune response,
reduced worker productivity, impaired cognitive development in children.
Excessive iron stores may increase risk of cancer and heart disease.
Catalyst: Fe2+ and Fe3+ catalyze lipid peroxidation in foods.
Color modifier: Color of fresh meat depends on valence of Fe in
myoglobin and hemoglobin: Fe2+ is red, Fe3+ is brown. Forms
green, blue, or black complexes with polyphenolic compounds.
Reacts with S2- to form black FeS in canned foods.
Enzyme cofactor: Lipoxyg enase, cytochromes, ribonucleotide
reductase, etc.
17

18. Mineral Food sources Function
Magnesium Whole g rains, nuts, legumes,
green leafy,Vegetables.
Essential nutrient: Deficiency rare.
Color modifier: Removal of Mg from chlorophyll changes color from green
to olive-brown
Manganese Whole g rains, fruits, vegetables Essential nutrient: Deficiency extremely rare.
Enzyme cofactor: pyruvate carboxylase, superoxide dismutase.
Nickel Plant foods Essential nutrient: Deficiency in humans unknown.
Catalyst: Hydrogenation of vegetable oils-finely divided, elemental Ni is the
18
Catalyst: Hydrogenation of vegetable oils-finely divided, elemental Ni is the
most widely used catalyst for this process.
Phosphates Ubiquitous, animal products
tend to be good sources
Essential nutrient: Deficiency rare due to presence in virtually all foods.
Acidulent: H3PO4 in soft drinks.
Leavening acid: Ca(HPO4)2 is a fast-acting leavening acid.
Moisture retention in meats: Sodium tripolyphosphate improves moisture
retention in cured meats.
Emulsification aid: Phosphates are used to aid emulsification in comminuted
meats and in process cheeses.

19. Mineral Food sources Function
Potassium Fruits, veg etables,
meats
Essential nutrient: Deficiency rare.
Salt substitute: KCl may be used as a salt substitute. May cause bitter flavor.
Leavening agent: Potassium acid tartrate.
Selenium Seafood, org an meats,
cereals (levels vary
depending on soil
levels)
Essential nutrient: Keshan disease (endemic cardiomyopathy in China) was
associated with selenium deficiency. Low selenium status may be associated
with increased risk for cancer and heart disease.
Enzyme cofactor: Glutathione peroxidase.
Sodium NaCl, MSG, other food
additives, milk; low in
Essential nutrient: Deficiency is rare; excessive intakes may lead to
hypertension.
19
Sodium NaCl, MSG, other food
additives, milk; low in
most raw foods
Essential nutrient: Deficiency is rare; excessive intakes may lead to
hypertension.
Flavor modifier: NaCl elicits the classic salty taste in foods.
Preservative: NaCl may be used to lower water activity in foods.
Leavening agents: Many leaving agents are sodium salts, e.g., sodium
bicarbonate, sodium aluminum sulfate, sodium acid pyrophosphate .

20. Mineral Food sources Function
Sulfur Widely distributed Essential nutrient:A constituent of the essential amino acids methionine and
cystine. Sulfur amino acids may be limiting in some diets.
Browning inhibitor: Sulfur dioxide and sulfites inhibit both enzymatic and
nonenzymatic browning .Widely used in dried fruits.
Antimicrobial: Prevents, controls microbial growth.Widely used in wine
making .
Zinc Meats, cereals Essential nutrient: Deficiency produces loss of appetite, growth retardation,
skin changes. Marginal deficiency exists in United States but extent is
Essential nutrient: Deficiency produces loss of appetite, growth retardation,
skin changes. Marginal deficiency exists in United States but extent is
unknown. Pronounced deficiency was documented in populations in the
Middle East.
ZnO is used in the lining of cans for proteinaceous foods to lessen
formation of black FeS during heating . Zn can be added to green beans to
help stabilize the color during canning .
20

21. REFERENCES
• 1. Principles of Food Chemistry, Third Edition by John M. deMan.,
published by Aspen Publishers.
• 2. Food Chemistry, Third Edition by Owen R. Fennema, published by
• 2. Food Chemistry, Third Edition by Owen R. Fennema, published by
Marcel Dekker.
21