SOP for Moisture Analysis by Hot Air Oven (As per FSSAI Method)

Objective

To determine the moisture content in food samples using the Hot Air Oven Method according to FSSAI Manuals of Methods of Analysis.

1. Purpose

This SOP describes the standardized procedure for determination of moisture content in food products by drying the sample in a hot air oven and calculating loss in weight. The method is commonly used for cereals, bakery products, spices, fish products, oils, fats, and other food materials. (FSSAI)

2. Scope

Applicable for:

• Food grains
• Flour and cereals
• Bakery products
• Fish products
• Oils & fats
• Powdered foods
• Processed foods

3. Principle

Moisture present in the sample is removed by heating in a hot air oven at specified temperature until constant weight is obtained. Loss in mass is considered as moisture content. (FSSAI)

4. Apparatus & Equipment

• Hot Air Oven (Temperature controlled)
• Analytical balance (Accuracy: 0.001 g)
• Moisture dishes/aluminium dishes/silica crucibles
• Desiccator with silica gel
• Tongs or heat-resistant gloves
• Spatula
• Grinder/blender (if required)

5. Reagents

Silica gel or phosphorus pentoxide as desiccant

6. Sample Preparation

1. Mix the sample thoroughly to obtain homogeneity.
2. Grind coarse samples if necessary.
3. Store in airtight container to avoid moisture gain/loss before analysis. (FSSAI)

7. Procedure

Step 1: Preparation of Dish

• Clean and dry the moisture dish.
• Place empty dish with lid in hot air oven at 105°C for 30 minutes.
• Cool in desiccator for 20–30 minutes.
• Weigh the empty dish and record weight as W.

Step 2: Weighing of Sample

• Weigh accurately about 2–5 g of sample into the dish.
• Record weight of dish + sample as W1.

Step 3: Drying

Place uncovered dish in hot air oven.

Method 1 – 105°C for 3 Hours

Place sample in hot air oven at 105°C ± 2°C.

Dry continuously for 3 hours.

Method 2 – 130°C for 2 Hours

Place sample in hot air oven at 130°C ± 3°C.

Dry continuously for 2 hours.

D. Cooling

Step 4: Cooling

• Cover the dish immediately.
• Cool in desiccator for 20–30 minutes.
• Weigh and record as W2.

Step 5: Constant Weight

Repeat drying for 30 minutes intervals.

Continue until difference between two successive weights is less than 1 mg.

8. Calculation

Formula

Moisture (%) = {W1 - W2}*100/{W1 - W}
 

Where:

W = Weight of empty dish

W1 = Weight of dish + sample before drying

W2 = Weight of dish + sample after drying

9. Example Calculation

{Moisture (%)} ={50.000 - 48.500}*100 / {50.000 - 45.000} 
 = 30%
 

10. Precautions

• Preheat oven before use.
• Avoid frequent opening of oven door.
• Use calibrated balance and thermometer.
• Cool samples only in desiccator.
• Avoid moisture absorption during weighing.
• Do not overload oven trays.

11. Safety

• Wear heat-resistant gloves.
• Handle hot dishes carefully.
• Use desiccator cautiously to avoid vacuum breakage.
• Follow laboratory PPE requirements.

12. Acceptance Criteria

• Duplicate results should be within laboratory acceptable variation.
• Constant weight must be achieved before reporting results.

13. Reference

FSSAI Manual of Methods of Analysis of Foods

AOAC Official Methods

IS Standards for Moisture Determination (Scribd)