SOP: Moisture in Spices and Condiments

GIFSQ — Global Institute for Food Safety & Quality

Principle

Water is distilled from the sample with an immiscible solvent and collected in a calibrated trap, the volume of water collected giving the moisture content. Spices whose sugars may decompose and form water are distilled with benzene instead of toluene; capsicum, dehydrated onion, garlic and vegetables are dried in a vacuum oven instead.

Apparatus required

• Immiscible solvent distillation apparatus with calibrated trap and distillation flask of 500–1000 ml capacity
• Vacuum oven

Reagents

a. Toluene (distillation solvent; benzene for red pepper, paprika and chilli powder).

b. Potassium dichromate–sulphuric acid cleaning solution (see Chapter 35).

c. 0.05 N alcoholic KOH solution.

Procedure

Clean the entire apparatus with potassium dichromate–sulphuric acid cleaning solution, rinse first with water, then with approximately 0.05 N alcoholic KOH solution, and drain for 10 min — if the alcoholic KOH contains carbonates, follow with an alcohol rinse

↓

Calibrate the trap: add 1 ± 0.01 ml of distilled water to 100 ml of toluene in the distillation flask, distil, and read the volume of water collected; note any correction required and repeat until the trap is calibrated

↓

Weigh 40 g of the prepared sample (sufficient to give 2–5 ml of water) and determine the moisture by the immiscible solvent distillation method as given in Chapter 1, using a 500–1000 ml flask — for red pepper, paprika and chilli powder, which contain larger amounts of sugar and other materials that may decompose and form water, use benzene as solvent instead of toluene

↓

For capsicum and dehydrated onion, garlic and vegetables: weigh 2–5 g of the sample and determine the moisture by the vacuum oven method at 70 °C under a pressure of not more than 100 mm of mercury for 6 hr

Precautions

• While determining moisture in the vacuum oven, do not place samples having high moisture content along with samples having low moisture content.

References

Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.