MOISTURE CONTENT, NUTRIENTS, AND OSMOSIS ON THE GROWTH OF MICROORGANISMS.

1. MOISTURE CONTENT, NUTRIENTS
AND OSMOSIS ON THE GROWTH
OF MICROORGANISMS
JANAVI BHANDARI
M.SC- FOOD AND NUTRITION
N-2005

2. CONTENT :-
 Introduction
 factors affecting microbial growth
1. moisture content
2. nutrients content
3. Osmosis
 Research papers

3. INTRODUCTION :-
 Microbial growth is define as increasing number of cells, not the size of the cell.
 Microbial cells obtain all the nutrients from the food nearby.
 Food may be plants or animal origin.
 Each type of food has it own characteristics constitutedwhich may affect the
growth of microbial cell.
 The growth depend on the availability of nutrient and other factors present over
there.
 In general, there are two type of factors exist:-
1. Intrinsic factor
2. Extrinsic Factor

4. INTRINSIC FACTOR :- MOISTURE
CONTENT :-
 Microbial cells require water in an available form to grow in food products.
 In ancient time food are preserved by controlling the moisture content.
 It is defined as the ratio of water vapour pressure of the food substrate to the
Vapour pressure of pure water at the similar temperature.
 Most fresh food that is Fresh Meat vegetable and truth half and value data close
to the optimum growth level of most microorganism (0.97 to 0.99).
 Microbiologist usually Express the water requirement of microorganisms in terms
of the water activity (aw )of the food or environment.

5. MOISTURE CONTENT WATER ACTIVITY : aw
 Moisture content = (% water/100 g of the product)
Ex:- Bananas – 75.7%
Asparagus – 91.7%
Pasta – 10.4%
 Water activity = index of availability water to microbial growth
Relative humidity RH = 100×aw
P = vapour pressure about the product
Po = vapour pressure of pure water
Aw = P/ Po

6. • Temperature
• Oxygen supply
• pH
• Inhibitors
• Culture medium
Factors that may affect aw
requirements of microorganism:-

7. INTRINSIC FACTORS:- NUTRIENT
CONTENT
 Microorganism have need of certain basic nutrients for the growth and
maintenance of physiological functions.
 These nutrients include water, source of energy, nitrogen, vitamins and
minerals
 Microorganisms select their food as substrate on the basic kinds and
proportions of nutrients present in food.
 Plant food have high concentrations of different types of carbohydrates and
varying level of protein, minerals and vitamins
 Milk and milk products and eggs are rich in nutrients.
 Meat is rich in protein, lipids, minerals and vitamins.

8. GROWTH CURVE :-
The population of growth is understood by
studying the growth curve. The growth of
microorganism reproducing by Binary
fusion can be plotted as the logarithm of
the number of viable cells versus the
incubation time. There are four distinct
phases:-
• Lag phase
• Log phase
• Stationary phase
• Death phase.

9. OSMOSIS:-
 Osmosis is the movement of
water from the lower solute
concentration into the solution
with high solute concentration.
 Equilibrium is reached once
sufficient water has moved to
equalize the solute
concentration on both side of
the membrane and at that
point net flow of water ceases
( water molecules still move
between two sides of the
membrane).

10. OSMOREGULATION IN BACTERIA :-
 Regulation of osmetic pressure of an organism fluid’s to
maintain the hemostatic of the organism water content.
 If organism have similar osmoregulation process this
indicate a common ancestry.
 In BACTERIA: If water is flowing into bacterium, it plum
pumps out salt. If water is going out of the bacterium it
pumps out water. Unicellular and relies on a single pump
mechanism to maintain homeostasis.

11. ISOTONIC :
◇ External concentration of
solute is equal to cell
internal environment.
◇ Diffusion of blood equals
in both direction.
HYPERTONIC :
◇ Environment has higher
solute concentration than
cell internal environment.
◇ Cells wrinkle (crenate).

12. RESEARCH PAPERS :-
 This research was done by two different scientists
FARZANEH REZAEI and JEAN S VANDERGHEYNST on
microbial activity of tomato pomace (TP), grape
pomace (GP), fermented grape pomace (FGP) and
sugar beet pulp (SBP) was monitored at nine different
moisture contents. And the results revealed that the
critical moisture content below which no microbial
activity was detected for SBP, TP, FGP and GP was 24-
31, 16-21, 23-33 and 43-46% (dry basis) respectively.

13. RESEARCH PAPER 2 :-
 SE-KEUN PARK and JIANG YONG HU has done their research on
the assessment of the extent of bacterial growth in reverse
osmosis system for improving drinking water quality. They
consulted that more than 99% of bacterial cells in the tap water
was retained by the RO membranes, leaving <50 cells/mL in the
permeate water. In spite of the low nutrient contents and few
cells in the RO permeates, showed that remarkable biofilm
accumulation and bulk cell growth occurred in the RO permeate
water.