Moisture content determination Methods by Hema Gavit

Moisture content:
 It is defined as the amount of water that can be removed
without alternation of chemical structure of grains.
OR
 The term grain moisture content normally denotes the
quantity of water present in a grain sample per unit
mass of its dry matter and moisture combined.
3Prof. H. S. Chaudhari

Moisture content Representation
 Moisture content (wet basis, %)
 Moisture content (dry basis, %)

1. Wet basis:
The moisture content on the wet basis is obtained by
dividing the weight of water present in the material by the
total weight of material.
Where, Ww = weight of water in the material
Wd = weight of dry matter in the material

2. Dry basis:
The moisture content on the dry basis is obtained by
dividing the weight of water present in the material by
the weight of dry matter of material.
Where, Ww = weight of water in the material
Wd = weight of dry matter in the material

Relationshipbetween dry basisand wet basismoisture
content:
The value of dry basis moisture content is more
than the wet basis moisture content.

Moisture content DeterminationMethods
DirectMethods
1. Oven Method
a) Air oven Method
b) Vacuum oven Method
c) Water oven Method
2. Brown-Duvel fractional distillation Method
3. Infra-Red Method
IndirectMethods
1. Electrical Resistance Method
2. Dielectric Method
3. Chemical Method

1. Oven Method
A] Air Oven Method:
a] One Stage Method:
It is used for grains under 13% moisture content.
Procedure:
1) Take 2-3 grams of representative ground samples of grain.
2) Place this sample in a air oven at 130 ˚C for about 1-2 hr.
3) Afterwards, the sample are taken out and placed in desiccators to cool
down.
4) The drop in weight of grain is measured.
5) M. C. of material is based on the difference between the initial weight
and final weight of grains.

b] Two stage method:
It is used for grain above 13% moisture content.
Procedure:
1) Take 25-30 grams of whole grains sample.
2) Place this sample in an oven at 100 ˚C for 72 to 96 hrs.
3) Take out the sample from oven and repeat the procedure as
in one stage method.
4) Measure the moisture content of the sample again.
5) M. C. of material is based on the difference between the
initial weight and final weight of grains.

B] Vacuum Oven Method:
It is used for fruits and vegetables.
Procedure:
1) In this method, 2-3 grams of representative sample of
ground material is placed in a vacuum oven (25mm
vacuum) at 100 ˚C for 72-96 hrs.
2) The drop in weight of grain is measured based on its
initial weight.

C] Water oven method:
when warm or hot water (about 100 ˚C) is circulated
around the walls to heat the oven.
This method maintains more uniform temperature
than air oven method.
Procedure:
1) Place 25-30 grams sample in a oven at 100 ˚C for 72-96
hrs.
2) Measure the drop in weight.

2.Brown- Duvelfractionaldistillationmethod
In this method, moisture is removed by heating the
grains in oil and determining the volume or weight of water
removed from the grain in condensed vapour or from the loss
of weight of the sample.
Procedure:
1) Take 100 grams of whole grains sample along with 150 ml of
mineral oil in a flask.
2) Boil the sample, so that moisture from the sample is
evaporated, collected and condensed in a graduated
cylinder. 14Prof. H. S. Chaudhari

3) The millimetre of moisture collected shows the percentage
of moisture content.
4) The determined moisture content is on wet basis.
5) In this method the temperature of mineral oil in flask
should reach to 200o c within 26 minutes.
6) The time required for moisture determination is about 30
minutes.
7) If the temperature of mineral oil reaches to desired
temperature within time, the m. c. determination is found
to be fairly accurate.

graduated cylinder.
Thermometer
Hot water bath
Graduated
cylinder
Brown- Duvel Fractional Distillation Apparatus
Mineral oil
Flask
Heating lamp

3. Infra-red method
In this method, grain moisture content is directly
measured by evaporation of water from a sample of grain
with an infra-red heating lamp. A commercial infra-red
moisture meter is also available in the market.
Procedure:
1) The instrument consists of a balance, a pan counter
balanced by a fixed weight and a variable length of
weighing chain.

2) An infra-red lamp is mounted on an arm above the pan with
provision to change its height.
3) A scale corporate in percentage moisture content is
incarnated in the stem of the instrument.
4) At the end of the test when the balance is zeroed, a direct
reading of moisture content is obtained.
5) The sample of grains may be ungrounded, but when ground
sample is used, the time needed to evaporate the water is
reduced.

Infra
Infra red lamp
Pan
Infra Red Method

1. Electrical resistance method
 The electrical resistance or conductivity of product depends
upon its moisture content.
 Resistance is an electrical quantity that measures how the
material reduces the electric current flow through it.
 This principle is used in résistance measuring devices.
 The moisture meter measures the electrical résistance of the
material and is calibrated against moisture determination
from oven or other primary methods.
 The universal moisture meter gives fairly accurate readings of
moisture content on wet basis. 22Prof. H. S. Chaudhari

2. Dielectric method
 Such devices measure the dielectric constant of grains.
 Dielectric constant is a quantity measuring the ability of a
substance to store electrical energy in an electric field.
 Grains are filled in chamber. The sides of the chamber are
formed by the plates of a condenser between which a high
frequency current is passed to measure capacitance of the
sample.
 The capacitance varies as per the water present in the sample,
the degree of compaction and grain temperature.

3. Chemicalmethod
 In this method, the water is removed by adding a chemical,
which decompose or combines with water.
 From the chemical reaction a gas is produced which can be
measured volumetrically or which decreases the original
weight of sample.
 This method is used for determining the m. c. of forages and
grains by shaking an excess of calcium carbide (Ca C2) with 30
grams of material. About 10 to 25 minutes are required to
reaction.

Estimation of Seed Moisture content by Air-oven
Method
Material required
 Mixer
 4 mm sieve
 2 Containers
 Metal tray
 Hot air oven
 Electronic weighing balance
 Desiccators

Observations
 Weight of empty containers with cover (M1)
 Weight of containers with cover and sample before
drying (M2)
 Weight of containers with cover and sample after
drying (M3)

Formula

Procedure
1. Take weight of empty containers along with their covers and
name them like S1 and S2.
2. Take 20-30 gm of the grain sample and grind it in mixer.
3. Separate the grain sample in two fraction with the 4 mm sieve
and take the sample which is retain on screen of the sieve.
4. Take 2 sample in two containers S1 and S2.
5. Weight both the sample alongwith with electronic weighing
balance and note the readings upto three decimal places.

6. Remove the covers of container and keep the sample in
hot air oven with inverted covers to allow escape of
moisture.
7. The temperature of oven should be raised to 60° Celsius.
8. Remove the sample after 1 hr with the help of thick hand
gloves.
9. Keep both the sample in desiccators for cooling for 1.5
hrs.
10.Take weight of dried sample.

Moisture content determination Methods by Hema Gavit

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