Dairy Product Adulteration Detection Methods PDF

Principles of Food and Dairy Sciences course (T 105) Biotechnology Program Students Level (1) BY Dr. OSAMA IBRAHIM ABDEL-SALAM EL BATAWY Prof., Food Science Department, Faculty of Agriculture, Ain Shams University, CHEMICAL ADULTERANTS IN MILK ...

Principles of Food and Dairy Sciences course (T 105) Biotechnology Program Students Level (1) BY Dr. OSAMA IBRAHIM ABDEL-SALAM EL BATAWY Prof., Food Science Department, Faculty of Agriculture, Ain Shams University, CHEMICAL ADULTERANTS IN MILK  CANE SUGAR Introduction Generally sugar is mixed in the milk to increase its solids not fat contents i.e. to increase the lactometer reading of milk, which is normally below the normal value if diluted with water. In laboratory, cane sugar (sucrose) in milk reacts with acidified resorcinol and gives red color.  Materials 1-Test reagent 2-Test tubes 3- Pasteur pipette 4- Spirit lamp 5-Match stick 6-Milk sample  Composition of the reagent Resorcinol 5.0 grams Hydrochloric acid 500 ml Dissolve 5.0 g of resorcinol in 500 ml HCl (1:1.5). One ml concentrated HCl (sp. gr. 1.18) is mixed with 1.5 ml of distilled water. (NI) The resorcinol flakes should be white in color.  Preparation of hydrochloric acid solution (NI) Hydrochloric acid (concentrated) 200 ml in Distilled water ` 300 ml NOTE: 1. Hydrochloric acid solution should be made in fume hood because fumes of the concentrated HCl are toxic for laboratory worker. 2. Add the acid in the water along sides of the container.  Procedure Take two test tubes and label one as “test” and other as “control” Transfer one ml milk sample to each of the tubes. Add 0.5 ml of the reagent in the tube marked as “test” and 0.5 ml distilled water in the tube marked as “control”. Mix the contents of each tube. Boil contents of each test tube  Results Appearance of deep red color indicates presence of sucrose, or a ketose sugar. (VI) Comments: Chemical test can detect the Cane sugar up to 0.5 % in raw milk. Addition of Cane sugar below 0.5% is hardly detectable in the laboratory. Volume of milk sample did not affect the laboratory testing of the cane sugar. Boiling of market milk did not affect the laboratory testing of the cane sugar.  UREA Introduction Urea is generally added in the preparation of synthetic milk to raise the SNF value.  Materials 1-Test reagent 2-Test tubes 3- Pasteur pipette 4-Milk sample Composition of the reagent p –Dimethyl amino benzaldehyde (DMAB) 8.0 grams + Hydrochloric acid 500 ml The reagent is prepared by dissolving 1.6 gm of p – DMAB in 100 ml of 10 % HCl.  Preparation of hydrochloric acid solution Hydrochloric acid (concentrated) 50 ml Distilled water ` 450 ml NOTE: 3. Hydrochloric acid solution should be made in fume hood because fumes of the concentrated HCl are toxic for laboratory worker. 4. Add the acid in the water along sides of the container. (NI)  Procedure Take two test tubes and label one as “test” and other as “control” Transfer one ml milk sample to each of the tubes. Add 1.0 ml of the reagent in the tube marked as “test” and 1.0 ml distilled water in the tube marked as “control”. Mix the contents of each tube.  Results Distinct yellow color is observed in milk containing added urea. However, the control (normal milk) may show a slight yellow color due to presence of natural urea. (VI) Comments: Chemical test can detect the urea in raw milk up to minimum level up to 0.05 %. Addition of urea below 0.05 is hardly detectable in the laboratory. Boiling of market milk did not affect the laboratory testing of the urea.  FORMALIN Introduction Milk is produced in rural areas of the country and is transported twice a day to big cities. ❖ During summer months, milk usually gets spoiled. The milk transporters add ice blocks to keep milk cool and formalin to preserve the milk in the containers. ❖ Formalin is highly toxic and carcinogenic therefore formalin added milk is hazardous for end consumers.  Materials 1-Test reagent 2-Test tubes 3- Pasteur pipette 4-Milk sample Composition of the reagent ✓ Sulphuric acid containing traces of ferric chloride 90% ✓ It is prepared by 10 ml distilled water along the sides of the concentrated sulphuric acid container. (NI) NOTE: 5. Sulphuric acid solution should be made in fume hood because fumes of the concentrated sulphuric acid are toxic for laboratory worker. 6. Add the acid in the water along sides of the container. (NI) Procedure Take two test tubes and label one as “test” and other as “control” Transfer one ml milk sample to each of the tubes. Add 1.0 ml of the reagent in the tube marked as “test” from the side of the test tube slowly and 1.0 ml distilled water in the tube marked as “control”. Mix the contents of each tube.  Results Formation of purple ring at the junction indicates formaldehyde is present in milk. (VI) Comments: Chemical test can detect minimum 0.0001 % formalin in raw milk. Addition of formalin below this level is hardly detectable in the laboratory. Note: It is noteworthy that formalin more than 1% in milk is undetectable by this test. Boiling of market milk did not affect the laboratory testing of formalin.  SODIUM BI-CARBONATES Introduction Sodium bi-carbonates or other neutralizers such as sodium hydroxide, sodium carbonate etc, are used to avoid curdling of milk during transportation. Addition of neutralizers is generally prohibited.  Materials 1-Test reagent 2-Test tubes 3- Pasteur pipette 4-Milk sample Preparation of the reagent Resolic acid 5 grams Ethanol 500 ml  Procedure Take two test tubes and label one as “test” and other as “control” Transfer one ml milk sample to each of the tubes. Add one ml of the reagent in the tube marked as “test” and one ml distilled water in the tube marked as “control”. Mix the contents of each tube.  Results Development of pink red color indicate that the milk is adulterated with sodium carbonate / sodium bicarbonate Comments ✓ Volume of milk sample did not affect the laboratory testing of the sodium bi-carbonate. ✓ Boiling of market milk did not affect the laboratory testing of the sodium bi-carbonate  STARCH Introduction Starch is commonly added to increase the density of milk (Lactometer reading) that reduces if it is adulterated with water. Uncooked starch may be health hazard for consumers but it is deceiving/ cheating to the end consumers. The presence of starch or cereal flours is detected in the laboratory.  Materials 1-Test reagent 2-Test tubes 3- Pasteur pipette 4-Milk sample Preparation of reagent Iodine crystal 6.5 grams Pot. Iodide 7.5 grams Distilled water 500 ml  Procedure Take two test tubes and label one as “test” and other as “control” Transfer one ml milk sample to each of the tubes. Add one ml of the reagent in the tube marked as “test” and one ml distilled water in the tube marked as “control”. Mix the contents of each tube.  Results Presence of starch is indicated by the appearance of a blue color which disappears when the sample is boiled and re appears on cooling. Comments: Chemical test can detect the starch up to 0.01 % in raw milk. Addition of starch below 0.01% is hardly detectable in the laboratory. Volume of milk sample did not affect the laboratory testing of the starch. Boiling of market milk did not affect the laboratory testing of the starch.  SODIUM CHLORIDE IN MILK Introduction Sodium chloride is normal components of milk but its normal concentration is not detectable by laboratory test. It is added in the milk to increase its density. Addition of table salt in milk is toxic for the consumers if suffering from blood pressure.  Materials Test tubes Pasteur pipette Solution A Potassium dichromate 25 grams Distilled water 500 ml Solution B Silver nitrate 840 grams Distilled water 500 ml Milk sample  Procedure Take two test tubes and label one as “test” and other as “control” Transfer one ml milk sample to each of the tubes. Add one ml of solution A in the tube marked as “test” and one ml water in the tube marked as control. Add one ml of solution B in the tube marked as “test” and one ml water in the tube marked as control.  Result Appearance of red precipitate indicate the absence of dissolved chloride in milk and appearance of yellow color indicate presence of dissolved chloride o Chemical test can detect the sodium chloride up to 0.25 % in raw milk. o Addition of sodium chloride below 0.25% is hardly detectable in the laboratory. o Volume of milk sample did not affect the lab testing of sodium chloride.