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08 Total Ash Methods​

08-01.01 Ash—Basic Method

Ash is the inorganic residue remaining after high-temperature incineration and is often included as part of the proximate analysis. This analytical method is a procedure to measure the ash content of flours, feeds, feedstuffs, other dry foods, and some food ingredients. In the case of wheat flour and related products, ash may be used as an indicator of residual bran content.

08-02.01 Ash—Rapid (Magnesium Acetate) Method

his analytical method outlines a rapid procedure to measure the ash content of wheat flour, often as part of the proximate analysis. Ash is the inorganic residue remaining after incineration. A sample of flour is placed in a preignited, tared platinum dish, and magnesium acetate solution is added. The dish and sample are placed in an electric muffle furnace (700°C) until incineration is complete (30–40 min). The crucible and ash are cooled in a desiccator and reweighed as soon as possible. Due to the hydroscopic nature of ash, cooling time and sample load in the desiccator should be strictly controlled. In the case of wheat flour and related products, ash may be used as an indicator of residual bran content.

08-03.01 Ash—Rapid (2-Hour, 600°) Method

Ash is the inorganic residue remaining after incineration, often part of the proximate analysis. This analytical method outlines a rapid procedure to measure the ash content of wheat flour, often as part of the proximate analysis. A sample of flour is placed in a preignited, tared platinum dish, and magnesium acetate solution is added. The dish and sample are placed in an electric muffle furnace (600°C) for 2 hr. The dish(es) containing ash are cooled in a desiccator and reweighed as soon as possible. Due to the hydroscopic nature of ash, cooling time and sample load in the desiccator should be strictly controlled. In the case of wheat flour and related products, ash may be used as an indicator of the residual bran content.

08-10.01 Ash in Cacao Products

Ash is the inorganic residue remaining after incineration, often part of the proximate analysis. This multistep analytical method outlines a procedure to determine the ash content of cacao products. A sample is placed in a previously ignited, cooled, and tared platinum or silica dish and then incinerated at 525°C until white ash is obtained. The ash is moistened, redried, and re-ashed at 525°C. Dish(es) containing ash are transferred and cooled in a desiccator, and the weight loss is used to determine the percentage of ash. Due to the hydroscopic nature of ash, cooling time and sample load in the desiccator should be strictly controlled.

08-11.01 Ash in Dry Milk Products

Ash is the inorganic residue remaining after incineration, often part of the proximate analysis. This analytical method outlines a procedure to measure the ash content of dry milk products. A sample is placed in a previously ignited, cooled, and tared porcelain crucible and then incinerated in a muffle furnace at 550°C until carbon-free. Crucibles are transferred to a desiccator and cooled, and the weight loss is used to determine the percentage of ash. Due to the hydroscopic nature of ash, cooling time and sample load in the desiccator should be strictly controlled.

(Note: This AACC method is substantially different from the ash method in the Standards for Grades of Dry Milks Including Methods of Analysis published by the American Dairy Products Institute.)

08-12.01 Ash in Farina and Semolina

Ash is the inorganic residue remaining after incineration, often as part of the proximate analysis. This analytical method outlines a procedure to measure the ash content of farina and semolina. A sample is placed in a previously ignited, cooled, and tared porcelain crucible and then incinerated at 600°C for at least 2 hr. Crucibles are transferred and cooled in a desiccator, and the weight loss is used to determine the percentage of ash. Due to the hydroscopic nature of ash, cooling time and sample load in the desiccator should be strictly controlled.

08-14.01 Ash in Molasses, Sugars, and Syrups

Ash is the inorganic residue remaining after incineration, often as part of the proximate analysis. This multistep analytical method outlines a procedure to determine the ash content of molasses, sugars, and syrups. A representative sample is placed in a previously ignited, cooled, and tared platinum crucible. The sample is dried at 100°C, olive oil is added, and the sample is incinerated at 525°C until white ash is obtained. The ash is moistened, redried, and re-ashed at 525°C to a constant weight. Crucible(s) are transferred and cooled in a desiccator and weighed. Due to the hydroscopic nature of ash, cooling time and sample load in the desiccator should be strictly controlled.

08-16.01 Ash in Soy Flour

Ash is the inorganic residue remaining after incineration, often as part of the proximate analysis. This analytical method outlines a procedure to measure the ash content of high-fat, low-fat, and defatted soy flours. A sample is placed in a previously ignited, cooled, and tared porcelain crucible and then incinerated in a muffle furnace at 600°C for 2 hr. Crucibles are transferred to a desiccator, cooled to room temperature, and weigh immediately. Due to the hydroscopic nature of ash, cooling time and sample load in the desiccator should be strictly controlled.

08-17.01 Ash in Starch

Commercial corn starches contain small amounts of inorganic salts that preexist largely in corn. It is customary practice to determine these collectively as residue after ignition at a specified temperature. This method is applicable to starches, dextrins, and other modified starch products.

08-18.01 Ash in Yeast Foods

This method determines ash (total mineral) content in yeast foods after ignition, often as a part of the proximate analysis.

08-21.01 Prediction of Ash Content in Wheat Flour—Near-Infrared Method

Ash is the inorganic residue remaining after high-temperature incineration of wheat flour and similar products, often part of the proximate analysis. This rapid instrumental analytical method is used to predict the ash content of wheat flour using near-infrared (NIR) spectroscopy, eliminating the time-consuming steps of incineration and cooling. There is a very high correlation between flour ash and bran cellulosic content (see reference), and it is likely NIR calibrations are associated with cellulosic components of bran fragments in the flour, rather than ash components. Mineral (ash) content of bran is about 20 times greater than that of endosperm; thus, ash content is used as an indicator of the degree of bran separation from the endosperm. See Method 39-00.01 for NIR guidelines.