ASH AND MINERAL MATTER
WATER SOLUBLE ASH DETERMINATION
Weighed five grams sample into a weighed platinum or porcelain dish. Charred. Ash at 500⁰C to 570⁰C until white and free from carbon. Cooled and weighed. Calculate % total ash from the data obtained. Add 25 ml distilled water to the dish. Boiled gently. Decant the liquor through an ash less filter paper. Repeated extraction with 25 ml distilled water. Discard the filtrate. Carefully washed out the dish collecting the residue in the filter paper. Remove the filter paper and transferred to the ashing dish. Dried in an oven at 105⁰C for one hour. Transferred the dish to a muffle furnace and ash at 550⁰C to 570⁰C until free from carbon. Cooled and weighed. Calculate the water soluble ash (%) from the data obtained.
% TOTAL ASH =
% WATER SOLUBLE ASH = % Total Ash - % Water Insoluble Ash
If the filtrate is cooled and titrated with 0.05 M (0.1N) H2SO4 using methyl orange indicator, the alkalinity of the soluble ash can be obtained. The alkalinity is usually calculated as K2O, K2CO3, OR Na2CO3. A low water soluble ash and alkalinity of the ash indicates abstraction of important constituents with consequent lowering of quality. B.
ACID INSOLUBLE ASH
Covered the previously determined ash with conc. HCl and evaporated to dryness on a boiling water bath. Repeated the addition of HCl with sibsequent evaporation. Dried at 150⁰C on a sand bath for one hour. Add 20 ml 10% HCl and warm on a boiling water bath for 10 minutes. Decant the liquor through an ash less filter paper. Repeated using two further additions of 25 ml 10% HCl. Washed all the remaining ash into the filter paper using hot distilled water. Washed all the residue in the filter paper with ample distilled water. Placed the filter paper and residue in the evaporating basin and re-ash in the muffle until the dish reaches a constant weight. % ACID INSOLUBLE ASH =
IDENTIFICATION OF CHEMICAL PRESERVATIVES ADDITIVES AND SYNTHETIC SWEETENING AGENTS IN FOODS METHODOLOGY
II. SODIUM BENZOATE
In sodium chloride solution of the sample, the benzoic acid present in the sample is converted into water-soluble sodium benzoate by the addition of NaOH. When the sodium benzoate solution is acidified with excess HCl, water insoluble benzoic acid is formed which is extracted with chloroform. The chloroform is removed by evaporation and the residue containing benzoic acid is dissolved in alcohol and then titrated with standard sodium hydroxide (NaOH). SAMPLE PREPARATION:
Mixed the sample thoroughly and grind, if solid or semi-solid. Transferred 100 g to a 500 ml volumetric flask. Add enough powdered NaCl to saturated the water in the sample, make alkaline to litmus paper with 10% NaOH solution, and diluted to mark with saturated salt solution. Shake thoroughly, allowed to stand for al least 2 hours with frequent shaking or preferably overnight and filter through Whatman No. 4 paper. If the sample contains large qualities of fat, proteins of which may contaminate the filtrate, add a few ml of the NaOH solution to the filtrate and extract with the ether before proceeding for determination. If alcohol is present, proceed as in the case of ciedr described below. Ketchup
To 100 g of the sample, add 15 g of NaCl and transfer the mixture to a 500 ml volumetric flask rinsing with approximately 150 ml of saturated salt solution, make alkaline to litmus with 10% NaOH and fill to mark with the saturated salt solution. Allow to stand for at least 2 hours, shaking frequently, centrifuge, if necessary and filter. Jellies, jams, Preserves and Marmalades
Mix 100-500 g of the sample in the approximate 300 ml of saturated NaCl solution. Add 15 g of NaCl and make alkaline to litmus with 10% NaOH. Tranfer 500 ml volumetric flak and dilute to mark with the saturated salt solution. Allow to stand for 2 hours, shaking frequently, centrifuge and filter. Cider, Containing Alcohol and Similar...
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