Butter Analysis

Definition, preparation of butter sample, Analysis of butter tests

1. ANALYSIS OF BUTTER FOOD ANALYSIS Submitted by Likitha Boga M. Pharmacy I-I Pharmaceutical Analysis

2. DEFINITION Butter is a smoothy fatty food made from milk or cream, or both, with or without common salt, and with or without additional coloring matter, and containing not less than 80% by weight of milk fat.

3. BUTTER CHARACTERISTICS Butter with a firm waxy body has an attractive appearance, has granules that are close knit, cuts clean when sliced, and has good spreadability. The trier sample from such butter will show this clean cut smooth, waxy appearance. The temperature of the butter at the time of grading is important in determining the true characteristics of body and should be between 45 o F and 50 o F.

4. APPARATUS Gooch crucible or sintered funnel. Glass funnel. Whatmann filter. Flat bottom flask. Desiccator. Asbestos. Hot air oven. Conical flask. Glass beads. Water-bath. Clay pipe triangles. Beakers Volumetric flask Burette Pipette Measuring cylinder

5. PREPARATION OF SAMPLE OF BUTTER Warm the sample   Oven / water bath maintained at 37 ± 2°C Shake To obtain homogeneous fluid emulsion free from un softened pieces [Note: In case, the sample does not mix up properly (water separation can be seen) reject the sample] Heat (50 - 60°C) Portion of emulsified butter in a beaker until the fat separates   Filter the fat layer into a dry vessel   Melt the filtered fat if necessary Re-filter To obtain clear fat free from water.

6. DETERMINATION OF MOISTURE IN BUTTER Clean the dish, glass rod and dry them in hot air oven at 100 ± 1°C for atleast 1 hr. Cool to room temp in desiccators & weigh the dish Weigh 3 - 4 gms of prepared butter sample in the dish   Place the dish on a boiling water-bath supported on a clay pipe triangle for at least 20 min, stirring at frequent intervals until no moisture can be seen. Transfer To the oven maintained at 100 ± 1°C and keep it for 90 min   Cool in the desiccator and weigh to 0.1 mg Heat the dish in an oven for 30 min

7. Repeat the process of heating, cooling and weighing until the differences between two consecutive weights does not exceed 0.1 mg   Record the lowest mass. CALCULATION: Moisture % by mass = M 1 – M 2 x 100 M 1 – M Where, M 1 = mass in gms, of the dish with the material before heating to constant weight M 2 = mass in gms, of the dish with the material after heating to constant weight M = mass in gms, of the empty dry dish.

8. DETERMINATION OF FAT AND CURD Fat portion is removed with the help of petroleum ether and residue left behind is dried for determination of curd content. In case of table butter, it is curd and salt content and thus salt content has to be determined separately for calculating curd content. Prepare a celite mat in a Gooch crucible or sintered funnel. Dry in hot air oven Cool in the desiccator and weigh. Alternatively, dry, cool and weigh ordinary glass funnel with folded 12.5 cm filter paper.   Melt the residue in the moisture dish + 25 to 50 ml of petroleum solvent. Mix well Place the funnel with filter paper on a filter stand.   Wet the filter paper with petroleum solvent. Decant the fatty solution from the dish into the filter paper, leaving the sediment in the dish.

9. Macerate the sediment twice with 20 to 25 ml of petroleum solvent. Decant again the fatty solution into the filter paper. Filter Filtrate is collected in a clean, dried, tared 250 ml flat bottom flask containing 1 to 2 glass beads.   With the aid of a wash-bottle containing petroleum solvent, wash all the fat and sediment from the dish into the crucible or the filter paper.   Wash the crucible or the filter paper until free from fat, collecting all the filtrate in the conical flask.   Preserve the filtrate for the determination of fat. Dry the crucible or filter paper in the oven maintained at 100 ± 1°C for at least 30 min. [ Note: If fat is to be determined only, transfer all the filtrate to a pre-dried and weighed fat flaks containing 2-3 glass beads. Rinse the conical flask with petroleum ether. Evaporate the ether, first on the water-bath and then in the oven at 102 ± 2°C for 1 hour or till the time the constant weight is obtained. Calculate the fat content form the residues obtained by using the formula]

10. % fat = (weight of fat flask + fat residues) – weight of empty flask x 100 weight of sample taken Cool and weigh Repeat drying, cooling and weighing until the loss of weight between the consecutive weighing does not exceed 0.1 mg.   Preserve the residue for the determination of salt. CALCULATION: Curd and salt % by mass (C) = M 1 – M 2 x 100 M Where, M 1 = mass in gms, of the filter paper with residue M 2 = mass in gms, of the filter paper alone M = mass in gms, of the sample Percent Fat w/w = 100 - (M+C) Where, M = Moisture percent C = Curd & salt percent Curd percent by weight is obtained by subtracting the value of salt percent by weight from the value of C.

11. DETERMINATION OF SALT CONTENT IN BUTTER METHOD: 1 (VOLHARD'S METHOD): In this method, salt present in the butter sample is extracted with hot water from the dried fat-free residue obtained in moisture determination. The chlorides are precipitated by adding excess of silver nitrate. The unused silver nitrate is titrated with potassium thiocyanate using ferric ammonium sulphate indicator. REACTION: Ag ­ ­ + (excess) + Cl - AgCl (solid) Ag + + SCN - AgSCN (solid) Fe +3 + SCN - [FeSCN] +2 (Reddish brown)

12. PROCEDURE: Extract the salt from the residue of curd and salt by repeated washing of the Gooch crucible or filter paper with hot water, or by placing the crucible or filter paper in beaker of hot water. Collect the rinsing in a 100 ml volumetric flask passing the solution through a filter paper. Allow to cool to room temperature and make up to volume. Take 25 ml water extract into a 250 ml conical flask, and add an excess (normally 25 to 30 ml) of 0.05 N silver nitrate solution. Acidify with nitric acid, add 2 ml of the indicator solution and 1 ml nitrobenzene. Mix and determine the excess of silver nitrate by titration with the potassium thiocyanate solution until the appearance of an orange tint, which persist for 15 s. In the same manner determine the equivalent of 25 ml or the added amount of silver nitrate as thiocyanate using the same volumes of reagents and water.

13. CALCULATION: NaCl % by mass = 23.38 x N x (A−B) M Where, N = normality of potassium thiocyanate solution (0.005 N) A = volume in ml, of potassium thiocyanate in blank titration B = volume in ml, of potassium thiocyanate in the sample titration M = mass in gms, of the butter sample. METHOD: 2 (MOHR'S METHOD): In this method, the butter sample is melted in hot water, and the chlorides present in the mixture are titrated with a solution of silver nitrate using potassium chromate as indicator. REACTION: AgNO 3 + NaCl AgCl + NaNO 3 2AgNO 3 + K 2 CrO 4 Ag 2 CrO 4 + 2KNO 3 (Brick red ppt)

14. PROCEDURE: Weigh accurately 5 g of butter sample into the 250 ml conical flask. Carefully add 100 ml of boiling distilled water. Mix the contents of the conical flask. Allow to stand with occasional swirling for 5 to 10 min. After cooling to 50 to 55°C (titration temperature), add 2 ml of potassium chromate solution. Mix by swirling. Add about 0.25 g of calcium carbonate and mix by swirling. Titrate at 50 to 55°C with standard silver nitrate solution while swirling continuously, until the brownish colour persists for half a minute. Carry out a blank test with all the reagents in the same quantity except the butter sample. The maximum deviation between duplicate determinations should not exceed 0.02% of sodium chloride. CALCULATION: NaCl % by mass = 5.844 x N (V 1 − V 2 ) M Where, N = normality of silver nitrate solution (0.1 N) V 1 = volume in ml, of silver nitrate used in the sample titration V 2 = volume in ml, of silver nitrate used in the blank titration M = mass in gms, of the butter sample

15. MICROBIOLOGY OF BUTTER Butter is made as a means of extracting and preserving milk fat. It can be made directly from milk or by separation of milk and subsequent churning of the cream. SOURCES OF CONTAMINATION In addition to bacteria present in the milk other sources of bacteria in butter are Equipment Wash water Air contamination Packing materials Personnel.

16. EQUIPMENT In smallholder butter-making, bacterial contamination can come from unclean surfaces, the butter maker and wash water. Packaging materials, cups and leaves are also sources of contaminants. Washing and smoking the churn reduces bacterial numbers. But traditional equipment is often porous and is therefore a reservoir for many organisms. When butter is made on a larger processing scale, bacterial contamination can come from holding-tank surfaces, the churn and butter-handling equipment. A wooden churn can be a source of serious bacterial, yeast and mould contamination since these organisms can penetrate the wood, where they can be destroyed only by extreme heat. If a wooden churn has loose bands, cream can enter the crevices between the staves, where it provides a growth medium for bacteria which contaminate subsequent batches of butter. However, if care is taken in cleaning a wooden churn this source of contamination can be controlled. Similar care is required with scotch hands and butter-working equipment.

17. WASH WATER Wash water can be a source of contamination with both coliform bacteria and bacteria associated with defects in butter. Polluted water supplies can also be a source of pathogens.

18. AIR CONTAMINATION Contamination from the air can introduce spoilage organisms, mould spores, bacteria and yeasts can fall on the butter if it is left exposed to the air. Moulds grow rapidly on butter exposed to air.

19. PACKAGING Care is required in the storage and preparation of packaging material. Careless handling of packaging material can be a source of mould contamination.

20. PERSONNEL A high standard of personal hygiene is required from people engaged in butter-making. For example, in New Zealand the 1938 dairy produce regulations stated "no person shall permit his bare hands to be brought in contact with any butter at any time immediately following manufacture or during the wrapping, packaging, storage and transport of such butter". Personnel pass organisms to butter via the hands, mouth, nasal passage and clothing. Suitable arrangements for disinfecting hands should be provided, and clean working garments should not have contact with other clothes.

21. CONTROL OF MICRO-ORGANISMS IN BUTTER Salting effectively controls bacterial growth in butter. The salt must be evenly dispersed and worked in well. Salt concentration of 2% adequately dispersed in butter of 16% moisture will result in a 12.5% salt solution throughout the water-in-oil emulsion. The acid pH of serum in butter made from ripened cream or sour milk may control the growth of acid-sensitive organisms. Microbiological analysis of butter usually includes some of the following tests: Total bacterial count, Yeasts and moulds, Coliform estimation Estimation of lipolytic bacteria. Yeast, mould and coliform estimations are useful for evaluating sanitary practices. The presence of defect producing types can be indicated by estimating the presence of lipolytic organisms. All butter contains some micro-organisms. However, proper control at every stage of the process can minimize the harmful effects of these organisms.

22. RANCIDITY OF BUTTER A sour-bitter taste is identifiable with rancidity (i.e. soapy, baby-vomit, blue cheese). Rancid butter becomes yellow to brown and the flavor becomes harsh. There appears to be a seasonal effect, with the months between July and September having the highest occurrences, and is also caused by stressed cows, and plumbing issued with the processing tanks. Rancidity is caused by a chemical development, which continues until the milk is pasteurized. It often occurs if the membranes around milk fat globules are weakened or broken. When butter becomes rancid, the enzyme lipase breaks it down into glycerol and fatty acids. Hydrolytic rancidity results in the formation of free fatty acids and soaps (salts of free fatty acids) and is caused by either the reaction of lipid and water in the presence of a catalyst or by the action of lipase enzymes. Low levels of free fatty acids are not objectionable if they are sixteen or eighteen carbon fatty acids as commonly found in soybeans, corn or animal fat. However, in butter fat (and coconut oil), low levels of shorter carbon chain fatty acids may be quite objectionable. The worst offender being butyric acid (butanoic acid).

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