the redox theory is one of the important theories in many fields , in my power point i have the effect/role of this theory on food spoilage

1. REDOX THEORY
OF FOOD
SPOILAGE
By ahmed mohammed talaat saeid

2. CONTENTS:
a)definition
b)Characters of food spoilage
c)Types of food spoilage
d)Redox theory
e)Oxidation of food
f)Factors affect redox on food
g)Air and oxygen
K)Effect of redox on microbial growth
l)Mechanism of redox on microbial growth
m)Prevention of oxidation of food spoilage
n)refrences

3. spoilage
 The deterioration of food and other
perishable goods
 Any change which renders a product
unacceptable for human consumption
 Complex event in which a combination of
microbial and biochemical activities may
interact
 Disagreable change in a food’normal state

4. Characters of food spoilage:
1-unpleasant smell
2-unpleasant taste
3-colour change
4-texture change
5-mouldy

5. Types of food spoilage:
• Microbial spoilage
• Non- microbial spoilage
• Based on rate of spoilage : there are three types
 Highly perishable :meat, fish, egg, milk, most fruits and
vegetables
 Semi perishable : potatoes, some apple varities and nut
meat
 Non-perishable or stable : sugar,flour and dry beans
• Pharmaceutical spoilage

6. Pharmaceutical spoilage:
-there are several factors that cause
pharmaceutical spoilage
physical chemical microbial
Deterioration of
pharmaceuticals
due to physical
factors like ,heat
,temperature
,evaporation,etc
Deterioration of
pharmaceuticals
due to chemical
reactions
like,oxidation
,reduction,
Hydrolysis,
Ionization,etc
Deterioration of
pharmaceuticals
due to
contamination of
any microbial cell
like,bacteria,fungi
,moulds,etc

7. What is a redox reaction ?
 Redox- reduction + oxidation
 Both process occur simultaneously
 Hence, one species is oxidized
,another is reduced
 So, what is oxidation, and what is
reduction?
 3 different versions of the
difinition

8. redox
oxidation reduction
Gain in oxygen Loss of oxygen
Loss of hydrogen Gain in hydrogen
Loss of electron Gain in electron

9. Oxidation of food :what a waste
-fruits and vegetables oxidized when left in open air

10. Oxidation of… people!
-oxidation of nutrients causes increased
activity of cells, leading to aging skin

11. Factors affect redox on food
i. Air
ii.Light
iii.oxygen

12. Air
 Oxidation, a chemical process that
produces undesirable changes in
color, flavor, nutrient content,
results when air reacts with food
components

13. light
Light exposure could
result in color and
vitamin loss. light may
be responsible for the
oxidation of fats

14. light
-oxidation of food
 Reversion flavor of soyabean
 Sunlight flavor in milk
 Rabid loss of riboflavin, vitamin D,E,C
 Greening of potato

15. oxygen
 Oxygen can also cause spoilage of foods
spontaneously, by itself. oxidative
spoilage is the chief cause of quality loss
in fats and fatty portions of foods. When
lipid oxidies, short chain carbon
compound are formed ;these compounds
have strong odors and flavors and are very
undesirable and unacceptable.

16. Air and oxygen
 One important cause of food spoilage is air and oxygen.
Because air is colorless, odorless, and tastless , it is
often taken for granted and sometimes forgotten as a
means to cause food to spoil.
 Air consists of 78%nitrogen, 21%oxygen, and 1%mixture
of other gases. While oxygen is essential for life, it can
have deteriorative effects on fats, and food colors,
vitamins, flavors, and other food conistituents.
Basically, oxygen can cause food spoilage in several
ways. It can provide conditions that will enhance the
growth of microorganisms; it can cause damage of foods
with the help of enzymes; and it can oxidation.

17. Effect of redox potential on
microbial growth
 Redox or oxireduction potential is defined as the
sum of all oxidizing (dissolved oxygen, free
radical, hydrogen peroxide, some oxidized metal
ion…) and reducing (some vitamins, some reduced
metal ions, thiol-containing molecules,
hydrogen…)couples found in the medium. This
means when the concentration of the oxidizing
molecules increases the redox potential value of
the medium increases but when the concentration
of the reducing molecule increases the redox
value of the medium decreases.

18. How can redox potential affect the growth
of the microorganism?
 To rerspond this question we must keep in the head the
relationship between the oxygen as oxidant found in the
atmosphere and the redox potential. When
microorganism found in aerobic medium (containing
dissolved oxygen it means the medium is favourable for
the growth of aerobic microorganisms which can use the
oxygen as a final acceptor of electrons produced from
the substrate via the metabolism.
 It is important to indicate here also that every
microorganism possesses a favourable value of redox for
growth. furthermore, It was reported that the redox
potential value affects the pH intracellular of a
microorganism, which form a component of the proton
motive- forc. This effect was attributed to the change
of the permeability of the cellular membrane, which
increased by the decrease of the redox value of the
medium.

19. The mechanism of the effect of the redox
potential on the growth of the
microorganisms
a) Its effect on the structural composition of some
sensitive-components/molecules found on the surface
of the cell. These redox-sensitive
components/molecules could be enzymes located in the
surface of the cell, which its protein part (Apoenzyme)
could be composed of sulfur-containing amino acids
making it sensitive to the redox potential of the
medium. Further more, the cofactors of these enzymes
such as Fe, Zn, Mg, and Cu could be found in the
oxidized or reduced form, which means the
susceptibility of these metal ions to the redox potential
of the substrate or/and the medium.
b) If the energetic system of the cell (proton motive force)
changes the ATP content of the cell will change which
can affect many essential functions of the cell.

20. prevention of oxidation of food
spoilage
 To forestall the effects of the oxidation, some
doctors and scientists recommend antioxidants
- Natural reducing agent such as vitamin C and
vitamin E. the vitamin C in lemon juice can be
used to prevent oxidizing on the cut surface of an
apple, to keep it from turning brown.
- Perhaps, Some experts maintain, natural reducing
agents can also slow the pace of oxidation of the
human body.

21. Thank you