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 45oF and 50oF.

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 = M1 – M2 x 100
M1 – M
Where, M1 = mass in gms, of the dish with the material before heating to constant
weight
M2 = 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) = M1 – M2 x 100
M
Where, M1 = mass in gms, of the filter paper with residue
M2 = 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
1. 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.
2. 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:
AgNO3 + NaCl AgCl + NaNO3
2AgNO3 + K2CrO4 Ag2CrO4 + 2KNO3
(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 (V1− V2)
M
Where, N = normality of silver nitrate solution (0.1 N)
V1 = volume in ml, of silver nitrate used in the sample titration
V2 = 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
1. Equipment
2. Wash water
3. Air contamination
4. Packing materials
5. Personnel.

16. 1. 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. 2. 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. 3. 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. 4. 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. 5. 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:
i. Total bacterial count,
ii. Yeasts and moulds,
iii. Coliform estimation
iv. 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).

23. THANK YOU