Microbiological Aspect of Butter
Microbiological Aspect of Butter
Microbiological Aspect of Butter
Micro-environment of Butter is unfavorable for growth of Microorganisms compared because of the following
compositional and structural differences.
a) Fat content in butter is relatively resistant to microbial decomposition is present in greater butter in
butter (about 80%) compared to cream (except for high fat plastic cream)
b) Lactose which is readily utilizable by many of the microorganisms is present in lower quantities.
c) Moisture content which is essential for microbial growth is present lower quantities (<16%) in butter.
d) Salt in butter make its micro environment unfavorable for microbial growth.
The nature of distribution of water and fat in cream and butter makes their microenvironment different. In cream
water is in continuous phase and fat is in discontinuous phase, where are the reverse in case of butter where
water is discontinuous phase present as drops dispersed in fat. A large number of water droplets are more than
the number of Microorganisms in butter. Moreover, unlike that in cream, Microorganisms cannot proliferate
easily and spread in butter because of the following reasons.
a) Water phase is separated by relatively resistant fat phase in butter. Molds and Psuedomycelia forming
yeast are able to grow and penetrate through the fat phase of butter.
b) Limited supply of nutrients in the H2O droplet in butter while in cream microorganisms can grow in the
continuous H2O phase having dissolved nutrients and migrate one portion to the other.
Microorganisms which are present in Butter are derived from a variety of sources are explained below.
27.3.1.1 Raw Material (Milk or Cream)
The quality of milk/cream utilized for production of Butter has a direct impact on microbiological quality of the
final product. Butter made from cream separated from EOD (Every other day) collected farm bulk tank milk or
bulk collected milk (refrigerated) was slightly inferior quality with respect to flavor to butter made from daily
collected can milk (cooled at 12°C). This is due to higher microbial number and activity in the EOD or bulk
collected milk. Highly heat resistant extracellular lipases which one secreted by Psychrotropic bacteria in such
milk may resettled in high free fatty acid content and also affect final composition and flavor of cream and butter
manufactured from it. This type of cream exhibited slow acid developed during ripening due to possible adverse
effects of liberated free fatty acids.
Both sour and sweet creams are generally used for manufacture of butter. Sweet cream contains fewer nor
organisms predominantly bacteria compared to yeast and molds. On the other side sour cream contains larger
nor of microorganisms sometimes up to a humdrum million per ml. Sometimes the cream may be accumulated
before churning into butter. During this period microbial growth may occur. In some cases, because of the high
initial population, a large number of bacteria may survive in the pasteurized cream. Since the quality of cream has
a direct bearing on the microbiological quality of butter, these are a need for adopting the following measures to
maintain the quality standards of butter.
1) Hygiene production of milk and cream.
2) Proper quality control of cream before butter making.
3) Avoiding accumulation and high temperature (75°C)
Storage of cream before butter making
The following test may be carried out for quality control of cream for butter making:-
a) Organoleptic test
b) Acidity
c) Sediment test
d) MBR test
e) TBG
f) YGM count
As per the procedure laid down by APHA for milk and cream, the following standards as given in Table 2 have
been suggested for grading of cream on the basis of various microbiological tests.
In India, no separate standard have been suggested for recommended for cream for butter making, though the
prescribed ISI standards are available market cream.
27.3.1.2 Equipments
The sanitary condition of various equipments used during butter manufacture determines to a great extent the
degree of contamination. Among these equipments, butter churn is microorganisms’ important source of
contamination particularly in regard to psychrotrophic organisms and yeast & molds, metals churns are
advantageous from sanitary point of view but still in many places, the wooden churns continue to be in use. These
wooden churns are difficult clean and sanitize since the wood surface is irregular which takes up water and
subsequently cracks, thereby, making the removal of solid particle difficult molds penetrates deep inside pores
and crevices of the wood and serve as a potential entry for contamination. The parts of pasteurizers and allied
units like pipelines, pumps, valves and coolers may be the other sources of contamination.
27.3.1.3 Water supplies
During manufacturing of butter, water may be used for different purposes like to flush residual cream form
holding values into churns, for dilution of cream as break water, as chilled wash water, for wet salting and for
adjusting the moisture content of butter. In case of continuous butter making process, water is used for washing
of butter granules. The contaminated water used one or more of those points lead to important sources for the
entry of microorganisms. The psychrotrophic bacteria known to cause spoilage in butter known to cause
spoilage in butter may gain entry into butter through such water supplies. The bacteria which are causing spoilage
into the final product through such water supplies are shown in Table 3.
Psychrotropic bacteria can grow extensively H2O in dairy tanks, when particularly when water contains some
organic matter and has not been efficiently chlorinated Coliforms and some heat resistant Psychrotropic strains of
bacilli and clostridia have been found to occur in natural water.
Psychrotropic counts of >100/ml & lipolytic counts of >10/ml are indicator of faulty chlorination of H2O
supplies. Total colony counts of >250/ml (determined at 21 or 25°C) & Most probable number (MPN) of >
10/ml (at 30°C) for Coliforms are indicator of unsatisfactorily quality of H2O supplies. The effective measures to
check contamination through water is chlorination of H2O supply by adding suitable concentration of chlorine (1-
5 ppm).
27.3.1.4 Air
Air is comparatively important source of contamination a butter plant than any other during product plant. All
plants don’t have a separate packing room or don’t maintain a high standard of hygiene in butter packing room
or don’t maintain a high standard of hygiene in butter packing and printing room. Thus butter often gets exposed
to air for long periods prior to or during packing and get contaminated bacteria are the most predominant
sources of aerial contamination followed by yeast and molds. Suggested standard reported Bacterial counts of
air ranging from 11-132/ft3 & yeast & mold count of 4-26/ft3 during butter packing and printing operations.
Psychrotrophs are also encountered in the air of dairy plants. Molds spores remain suspended in air and
contaminant walls or wooden structures in the packing room, which can serve as growth centres for molds. The
main sources of aerial contamination in dairy plant appear to be announcement of workers, fans, drains and dust
from the surrounding areas.
Personnel
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The persons involved in the manufacture and handling butter may introduce Microorganisms to butter through
contaminated hands, clothing, mouth, nasal discharge, sneezing etc particularly doing packaging stage unhealthy
persons, particularly those suffering from respiratory disorders should not be allowed to handle butter. The
personnel engaged in the packaging room should follow the hygiene measures.
Butter color
The color used for incorporation into butter is particularly free from micro organisms. However, if it is kept in
open containers or is mixed with water in a unclean measuring containers, there are chances of contamination of
butter through butter color.
Packaging material
Normally, parchment paper is used for packing butter. This paper is usually received in a satisfactory condition
from the manufacturer but it may get contaminated especially with molds. Subsequently during transportation or
storage use of dry parchment and or air treatment of parchment with hot brine or antifungal chemicals like sorbic
acid/ potassium sorbate, Propionic acid/ calcium or sodium propionate or benzoic acid/ Sodium benzoate may
reduce the mold contamination. Normally, a combined treatment of hot brine and sorbic acid (0.5%) for 24 hrs
is recommended.
27.3.2 Effect of processing on the microflora of butter
A number of factors like processing of cream, method of manufacture, working and salting and conditions of
storage affect the microflora of final product.
27.3.2.1 Effect of cream processing
The processing of sweet or sour cream like neutralization, pasteurization and cooling have a pronounced effect
on the microbiological quality of butter.
a) Neutralization of cream
The sour cream is neutralized before heat processing. The neutralization step may affect the microbiological
quality in the following manner.
The contaminated neutralization solution as a result of poor quality water used for dissolving neutralizers may add
microorganisms in cream. However, the contaminants entering at this step may get killed during subsequent
pasteurization of the neutralized cream.
(ii) Pasteurization
Cream is pasteurized at 71.1o C for 30 min (LTLT) or 90o C for 16 sec (HTST), which is more severe treatment
than that required for fluid milk. This leads to nearly 99% destruction of microorganisms in cream. However,
some of the cream borne Microorganisms are still carried over to the butter due to the following reasons:
a) Resistance of certain microorganisms to survive pasteurization enables some of these organisms like
psychotropic heat resistant bacteria to cause spoilage in butter.
b) Improper pasteurization may results the survival of some spoilage causing Microorganisms. Hence, a
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The nature of moisture distribution in turn affects the microflora of butter. The microbial growth is restricted only
infected droplets and a large number of tiny droplets in properly worked butter remain sterile since migrations of
bacteria through the resistant fat mass is difficult the proliferation of organism in the infected droplet is restricted
due to limited availability of nutrients. On the other hand, in under worked or unworked butter, the bigger water
droplets support greater proliferation of microorganisms, thereby leading to butter spoilage. Based on this
mechanism, working of butter discourages microbial growth due to fines and uniform moisture distribution
whereas printing encourages microbial multiplication by creating bigger droplets. Reworking has been observed
to cause rapid deterioration of butter samples stores for long time probably by renewed microbial activity.
27.3.2.4 Effect of salting
Salt, generally added to butter, is inhibitory to the growth of microorganisms. However, its action is influenced by
its concentration and its uniform distribution in water droplet which in turn in dependent if butter is worked
efficiently. The salted tiny droplets will contain high concentration (>15% salt and hence prevent bacterial
growth). If salt is not is uniformly distributed, the bacteria will grow in regions where the salt concentration in
moisture is low or absent. Therefore, microbial growth is checked in the infected droplet in droplets in salted
butter and as a result microorganisms are more active in can worked or under worked salted butter than in
properly salted butter.
However some salt tolerant organisms for example particularly fluorescent pseudomonades can grow in 3% salt
concentration very few can grow in 5% salt and none can grow in 6% salt concentration certain molds can also
tolerate high slat concentration and grow on the butter surface.
27.3.2.5 Effect of packaging
The addition of contaminating microorganisms in butter, at packaging stage mainly occur through air and
packaging materials, although the role of unhygienic packaging equipment surfaces of personnel cannot be
excluded.
At low temperature storage, particularly in cold stores, the rate of growth of Microorganisms decreases and only
Psychrotropic organisms can multiply at such temperature. Coliform bacteria die out during cold storage. Slight
growth will occur in butter held at temperature below 0°C and none is expected at -15°C. At this, temperature
the total bacterial would be expected to decrease slightly especially unsalted butter. Hence the ideal temperature
for storage of butter for keeping quality (12-18 months) is -12 to 18°C. Since the cooling rate of butter is slow
due to its high fat content, the bacterial counts will often increase especially in unsalted butter during the initial
stage of storage.
Growth of micro organisms in butter causes a variety of color and flavor defects. Most of the microorgansims in
cream gets killed during pasteurization, the spoilage organisms mainly come through post pasteurization steps and
butter making. The defects in butter mainly attributed to the presence of psychotropic bacteria (lipolytic &
proteolytic), yeast and molds. The psychotropic bacteria which are entering the product through unhygienic
equipment grow during low temperature storage. However, molds create problems and relatively high
temperature as prevalent India.
A. Color defects (Discoloration)
Discoloration of butter may be caused by bacteria, yeasts and molds. However major color defect in butter
are caused by yeast and molds.
Bacterial Discoloration
a) Black discoloration (like grease smudge) causative organisms: Pseudomonas nigrificans. Due to
butter stored at low temperature (optimum for pigmentation is 4°C i.e. 15-20% salt concentration in the
moisture droplets.
b) Fungal Discoloration: Butter gets discolored due to surface growth of molds and the defect is also
described as ‘moldy butter’. This is a major defect commonly occurred in India since the ambient
temperature storage condition encourages the growth of Fungi in butter. Fungi growth also favored by
higher moisture content and acidity. Some psychotropic molds like Alternaria, Harmodendrum, phoma
and stamphylium have been appear to grow in butter ( unsalted) at low temperature (5°C) slightly growth
@ -4 to -6°C but not @ -7 to -9°C. Some common fungal discoloration frequently occurred in butter
areas follows
Discoloration Causative agent
a. Mold discoloration
i. Black Cladosporium Eg. C. harbarum, Aspergillus, Hasmodendrum,Alternaria, Mucor,
Rhizopus, and Stamphylium
ii. Brown Aspergillus spp, and Phoma spp (muddy brown)
iii. Green & blue green Penicillium spp and Aspergillus app
iv. Orange & yellow Geotrichum candidum
B. Flavor defects: - Rancid & putrid or cheesy odor is the most common flavor defects in butter. The other
defects like malty, Shunk-like flavor yeasty may also occur in butter.
a. Rancid flavor: - Butter gets rancid due to microbial, enzymatic or chemical degradation of fat
constituents. The fat hydrolysis in butter mainly due to the activity of microbial lipases. Many of the lipolytic
microorganisms are psychotropic and are able to grow @ temperature slightly under 0°C and survive cold
storage @ -10°C. Some of the lipase producing organisms which can grow on butter is as follows.
Bacteria Mold Yeast
c. Cheese taints: - Cheese like flavors in butter is due to association action of different gram
negative rods shaped bacteria due to butter stored above 10°C.
d. Other flavor taints: -
i. Malty flavor: - is due to presence and growth of streptococcus Lactsis variable maltigenes in
cream. The formation of 3-methyl butanol in butter mainly responsible for malty flavor.
Beuro of Indian standards (BIS) has given the following standards for raw and pasteurized cream
i. Raw cream
Plate count/ ml (or g) Grade
< 4 X 105 Very good
Standards Methods for the Examination of Dairy Products, published by the American Public Health
Association. Samples shall be taken as often as necessary to insure microbial control.
Coliform -- Not more than 10 per gram.
E. coli. -- Negative.
Yeast and Mold -- Not more than 10 per gram.
Standard Plate Count -- Not more than 1,000 per gram.
The following terms, as used by the International Commission on Microbiological Specifications for Foods
(ICMSF), are defined and used in Standard 1.6.1.
n = the number of sample units which must be examined from a lot* of food. Most sampling plans specify taking
five sample units. However, when the risk has been assessed as relatively
high, a greater number of sample units is specified.
c = the maximum allowable number of defective sample units. This is the number of sample units, which may
exceed the microbiological limit specified by ‘m’. These are considered marginal results, but are acceptable
providing they do not exceed the limit specified by ‘M’.
m = the acceptable microbiological level in a sample unit. Sampling plans in which m=0 and c=0 are equivalent to
‘absent’ or ‘not detected’ reporting for the stated analytical unit size. In most cases this is 25 g (e.g. not detected
in 25 g).
M = the level which, when exceeded in one or more samples, would cause the lot to be rejected.
*A lot means a quantity of food, which is prepared or packed under essentially the same conditions, usually:
• From a particular preparation or packing unit; and
• During a particular time ordinarily not exceeding 24 hours.
A lot of food does not comply with the standard if the number of defective sampled units is greater than c, or the
level of a micro-organism in a food in any one of the sample units Exceeds M.
M 50,000/g 50,000/g
2 Coliform Count2 m < 10 /g 10/g
M 50/g
3 E.coli3 M Absent/ g Absent/g
4 Salmonella4 M Absent/ 25g Absent /25g
5 Staphylococcus aureus5 m < 10/ g 10/g
(coagulase positive) M 50/g
6 Yeast and mould count6 m - 20/g
M - 50/g
7 Spore Count: - -
(a) Aerobic7a m -
(B. cereus ) M - -
(b) Anaerobic7b m - -
(Clostridium
M - Absent/g
Perfringens)
8 Listeria monocytogenes8 M Absent/g Absent/g
Sampling Guidelines9 5 5
n 1-8
c
2 1-2, 5 2 1-2, 5-6
03,4, 8 03,4, 8
Storage & 0 to 4°C -18°C
transport
Sample size 100ml or g 100ml or g