Translated English of Chinese Standard: GB5009.4-2016 www.chinesestandard.net Sales@ChineseStandard.net NATIONAL STANDARD OF GB THE PEOPLE S REPUBLIC OF CHINA GB 5009.4-2016 National Food Safety Standard - Determination of Ash in Foods Issued on: August 31, 2016 Implemented on: March 1, 2017 Issued by: National Health and Family Planning Commission of the People 's Republic of China. www.chinesestandard.net Page 1 of 15
Table of Contents Foreword... 3 1 Scope... 4 2 Principle... 4 3 Reagents and materials... 4 4 Instruments and equipment... 5 5 Analysis steps... 5 6 Expression of analysis results... 7 7 Precision... 9 8 Principle... 9 9 Reagents and materials... 9 10 Instruments and equipment... 9 11 Analysis steps... 10 12 Expression of analysis results... 10 13 Precision... 12 14 Principle... 12 15 Reagents and materials... 13 16 Instruments and equipment... 13 17 Analysis steps... 13 18 Expression of analysis results... 14 19 Precision... 15 www.chinesestandard.net Page 2 of 15
Foreword This Standard replaces GB 5009.4-2010 Determination of Ash in Foods, GB/T 5505-2008 Inspection of grain and oils - Determination of the ash content by incineration, GB/T 22427.1-2008 Starch - Determination of ash, GB/T 9695.18-2008 Meat and meat products - Determination of total ash, GB/T 12532-2008 Determination of ash content in edible mushroom, GB/T 9824-2008 Determination of total ash in oilseed residues, GB/T 9825-2008 Inspection of grain and oils - Determination of insoluble dietary fiber in cereals, GB/T 12729.7-2008 Spices and condiments - Determination of total ash, GB/T 12729.8-2008 Spices and condiments - Determination of water-insoluble ash, GB/T 12729.9-2008 Spices and condiments - Determination of acid-insoluble ash, GB/T 17375-2008 Animal and vegetable fats and oils - Determination of ash, GB/T 22510-2008 Cereals, pulses and by-products - Determination of ash yield by incineration, GB/T 8306-2013 Tea - Determination of Total Ash Content, GB/T 8307-2013 Tea - Determination of Water-soluble Ash and Water-insoluble Ash Content, GB/T 8308-2013 Tea - Determination of Acid-insoluble Ash Content, SN/T 0925-2000 Method for the determination of tea total ash of for import and export, SN/T 0921-2000 Method for the determination of water-soluble ash and water-insoluble ash of tea for import and export, SN/T 0923-2000 Method for the determination of acid-insoluble ash of tea for import and export, NY 82.8-1988 Determination of Fruit Juice - Total Ash. Compared with GB 5009.4-2010, the main modifications in this Standard are as follows: - added the determination of ash in starch and its derivatives according to GB/T 22427.1-2008; - added the determinations of water-soluble ash and water-insoluble ash, the determinations of acid soluble ash and acid insoluble ash in some foods. www.chinesestandard.net Page 3 of 15
National Food Safety Standard - Determination of Ash in Foods 1 Scope Method One of this Standard specifies the determination method of ash in foods. Method Two specifies the determination method of water-soluble ash and water-insoluble ash in foods. Method Three specifies the determination method of acid insoluble ash in foods. Method One of this Standard is applicable to the determination of ash in foods (starch ash method is applicable to starch and modified starch of which the mass fraction is not greater than 2%). Method Two is applicable to the determinations of water-soluble ash and water-insoluble ash in foods. Method Three is applicable to the determination of acid insoluble ash in foods. Method One Determination of total ash in foods 2 Principle The inorganic matter left after the burning of the food is called ash. Ash value is calculated by burning and weighing. 3 Reagents and materials Unless otherwise stated, the reagents used in this method are of analytical grade and water is Grade 3 water specified in GB/T 6682. 3.1 Reagents 3.1.1 Magnesium acetate [(CH3COO)2Mg 4H2O] 3.1.2 Concentrated hydrochloric acid (HCl) 3.2 Reagent preparation 3.2.1 Magnesium acetate solution (80 g/l): weigh 8.0 g of magnesium acetate, add water to dissolve and set volume to 100 ml; well mix. 3.2.2 Magnesium acetate solution (240 g/l): weigh 24.0 g of magnesium www.chinesestandard.net Page 4 of 15
starch, wheat starch and rice starch, 10 g for corn starch and tapioca starch), nearest to 0.0001 g. Evenly distribute the sample in the crucible. Do NOT press. 5.3 Determination 5.3.1 Beans and their products, meat and poultry and their products, eggs and their products, aquatic products and their products, milk and dairy products of high phosphorus content 5.3.1.1 After weighing sample, add 1.00 ml of magnesium acetate solution (240 g/l) or 3.00 ml of magnesium acetate solution (80 g/l) to make the sample completely wet. After 10 min of placement, evaporate the water to dryness on the water bath. Heat the sample on a hot plate with a small fire to fully carbonize the sample to smoke-free. Then place it in the high temperature furnace. Burn it at 550 C ± 25 C for 4 h. Cool it to around 200 C. Take it out. Put it in the dryer for 30 min of cooling. Before weighing, if the burning residues are found to have carbon particles, it shall drip a little water into the sample to moist, loosing the agglomeration. Evaporate the water. Burn it again till there are no carbon particles, which means the ashing is completed. Then it can be weighed. Repeat burning till the difference between two weighings before and after shall not exceed 0.5 mg. And that shall be constant weight. 5.3.1.2 Pipet 3 magnesium acetate solutions of same concentration and volume with 5.3.1.1. Carry out 3 reagent blank tests. When the standard deviation of 3 test results is less than 0.003 g, take the arithmetic mean as the blank value. If the standard deviation exceeds or equals to 0.003 g, it shall carry out the blank value test one more time. 5.3.2 Starchy food Place the crucible on a high temperature oven or a hot plate. Half-lid the crucible cover. Carefully heat the sample to completely carbonize to smoke-free in a ventilated condition. Immediately place the crucible in a high temperature oven. Raise the temperature to 900 C ± 25 C. Keep this temperature until the remaining carbon disappears. Generally, it takes 1 h to complete the ashing. Cool it to around 200 C. Take it out. Put it into the dryer to cool for 30 min. Before weighing, if the burning residues are found to have carbon particles, it shall drip a little water into the sample to moist, loosing the agglomeration. Evaporate the water. Burn it again till there are no carbon particles, which means the ashing is completed. Then it can be weighed. Repeat burning till the difference between two weighings before and after shall not exceed 0.5 mg. And that shall be constant weight. 5.3.3 Other foods www.chinesestandard.net Page 6 of 15
m3 - masses of crucible and sample, in grams (g); w - sample dry matter content (mass fraction), %; 100 - unit conversion factor. When the ash content in sample is 10 g/100g, three valid digits shall be remained. When the ash content in sample is < 10 g/100g, two valid digits shall be remained. 7 Precision The absolute difference between the two independent determinations obtained under reproducible conditions shall not exceed 5% of the arithmetic mean. Method Two Determination of water-soluble ash and water-insoluble ash in foods 8 Principle Extract the total ash with hot water. Filter by ashless filter paper. Burn. Determine the water-insoluble ash. Calculate the water-soluble ash by the mass difference between total ash and water-insoluble ash. 9 Reagents and materials Unless otherwise stated, the water used in this method is Grade 3 water specified in GB/T 6682. 10 Instruments and equipment 10.1 High temperature furnace: maximum temperature 950 C 10.2 Analysis balance: resolutions are 0.1 mg, 1 mg, 0.1 g 10.3 Quartz crucible or porcelain crucible 10.4 Dryer (with desiccant) 10.5 Ashless filter paper 10.6 Funnel www.chinesestandard.net Page 9 of 15
15 Reagents and materials Unless otherwise stated, the reagents used in this method are of analytical grade and water is Grade 3 water specified in GB/T 6682. 15.1 Reagents Concentrated hydrochloric acid (HCl) 15.2 Reagent preparation Use distilled water to dilute 10% hydrochloric acid solution, 24 ml of analysis pure concentrated hydrochloric acid to 100 ml. 16 Instruments and equipment 16.1 High temperature furnace: maximum temperature 950 C 16.2 Analysis balance: resolutions are 0.1 mg, 1 mg, 0.1 g 16.3 Quartz crucible or porcelain crucible 16.4 Dryer (with desiccant) 16.5 Ashless filter paper 16.6 Funnel 16.7 Surface dish: diameter is 6 cm 16.8 Beaker (high): volume is 100 ml 16.9 Constant temperature water bath: temperature control accuracy is ± 2 C 17 Analysis steps 17.1 Crucible pretreatment See 5.1 Crucible pretreatment. 17.2 Sample weighing See 5.2 Sample weighing. 17.3 Total ash preparation www.chinesestandard.net Page 13 of 15
where, X1 - acid-insoluble ash content, in grams per 100 grams (g/100g); m1 - masses of crucible and acid-insoluble ash content, in grams (g); m2 - mass of crucible, in grams (g); m3 - masses of crucible and sample, in grams (g); w - sample dry matter content (mass fraction), %; 100 - unit conversion factor. When the ash content in sample is 10 g/100g, three valid digits shall be remained. When the ash content in sample is < 10 g/100g, two valid digits shall be remained. 19 Precision The absolute difference between the two independent determinations obtained under reproducible conditions shall not exceed 5% of the arithmetic mean. END www.chinesestandard.net Page 15 of 15