Agricultural Product Standards Act, 1990 (Act No. 119 of 1990)RegulationsGrading, Packing and Marking of Dried Fruit intended for sale in the Republic of South AfricaAnnexuresAnnexure B : Determination of Moisture Content |
ANNEXURE B
DETERMINATION OF MOISTURE CONTENT
The moisture content of dried fruit, excluding dates, shall be determined by the following method:
| A. | Laboratory Reference Method·1 |
| (a) | Definition |
The moisture content of dried fruit is defined as being the loss of mass determined under the operating conditions described below.
| (b) | Principle |
The principle of the method is the heating and drying of a sample of dried fruit at a temperature of 70°C ± 1°C at a pressure not exceeding 100 mm Hg.
| (c) | Apparatus |
Usual laboratory apparatus is used together with the following items:
| • | Electrically heated constant-temperature oven, capable of being controlled at 70°C at a pressure of 100 mm Hg. |
| • | Dishes with lids of about 8,5 cm in diameter. |
| • | Hand or mechanically operated mincer. |
| • | Desiccator, containing an effective desiccant. |
| • | Analytical balance. |
| (d) | Procedure |
| (i) | Preparation of the sample |
Take approximately 50 g of dried fruit from the laboratory sample and mince these twice with the mincer.
| (ii) | Test portion |
Place 2 g of finely divided asbestos*2 into the dish. Tare the analytical scale with the dish with its lid and the asbestos, dried beforehand. Weigh, to the nearest 0,01 g, 5 g of prepared sample.
| (iii) | Determination |
Moisten the sample and the asbestos thoroughly with a few ml of hot water. Mix the sample and the asbestos together with a spatula. Wash the spatula with hot water to remove the sample residues from it, letting the residues and the water fall into the dish.
Heat the open dish on a boiling-water bath to evaporate the water. Then place the dish, with the lid alongside it, in the oven and continue drying for six hours at 70°C under a pressure not exceeding 100 mm Hg, during which time the oven should not be opened. During drying admit a slow current of air (about two bubbles per second) to the oven, the air having been dried by passing through H2SQ4. The metal dish shall be placed in direct contact with the metal shelf of the oven. After drying, remove the dish, cover it immediately with its lid and place it in the desiccator. After cooling to ambient temperature, weigh the covered dish to the nearest 0,01 g.
| (e) | Calculation and expression of results |
The moisture content of the sample, as percentage by mass is given by the expression:
Moisture Content = (M1 - M2) x 100
(M1 - Mo)
Where:
Mo: is the mass of the empty dish with its lid and containing the asbestos, g.
M1: is the mass of the dish with its lid, asbestos and test portion before drying, g.
M2: is the mass of the dish with its lid, asbestos and test portion after drying, g.
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| *1 | This method is the same as that prescribed by the AOAC: Official methods of Analysis, XIIIth Edition, 1980, 22.013 - Moisture in Dried Fruits, Official Final Action . The results are expressed to one decimal place. Duplicate determination should agree to 0,2% moisture. |
| *2 | Dried sand which has previously been washed in hydrochloric acid and then rinsed thoroughly with water shall be used in the place of the asbestos. Analysts using this technique should note that it is a deviation from the AOAC procedure and should mention this in their report. |