Microbiological Analysis of Milk and Milk Products


Defilement of milk:

Defilement of milk happens at two levels:

On ranch:

In every case, fresh milk contains a few germs. Micrococcus and Streptococcus are commonly discovered in aseptically obtained new milk.

Milk is exposed to contamination from the creature's udder and neighbouring places during normal draining contact.

Microscopic organisms found in faeces, dirt, and water poison the udder of the creature, from which milk is produced.

Other conceivable wellspring of pollution is hand and finger of milker or other dairy laborers.

Tainting additionally happens from dairy utensils.

During transport and at handling plant:

During shipping and assembly, tainting occurs through the use of a large hauler, moving pipes, testing utensils, and other equipment.

Microbes from the milk overseer's palm and finger may contaminate the milk here and there.

Milk and mik goods contaminated by microorganisms:

Milk is a fantastic social media medium for the growth of different microorganisms.

As a result, numerous microbes populate it and create waste.

I. Deterioration of Milk and cream:


Sharp taste and subsequent coagulation of milk to create strong like curd are evidence of milk souring.

Many lactic corrosive microbes, coliforms, and other tiny organisms age milk sugar and generate corrosive.

Streptococcus lactis is likely to produce souring at temperatures ranging from 10 to 37 degrees Celsius, with the possible formation of Coliform, Enterococci, Lactobacillus, and Micrococcus.

Streptococcus thermophilus and Streptococcus faecalis may generate 1% corrosive at higher temperatures, 37-50oC, and may be followed by Lactobacillus, which produces more corrosive.

Little souring happens in milk held at refrigeration temperature.

Sanitization of milk kills more dynamic corrosive framing microscopic organisms yet grant endurance of thermoduric lactic corrosive microorganisms, for example, Enterococcus, Streptococcus thermophilus, Lactobacillus, and so forth

Microbes other than lactic corrosive microorganisms produce corrosive uncommonly assuming conditions are troublesome for lactic corrosive microscopic organisms.

For instance: coliform produce acidic corrosive, formic corrosive, ethanol, CO2, H2 and so on

Also, Clostridium produce butyric corrosive.

Gas creation (Strong maturation of milk):

Sugar aging creature produce gas along with corrosive.

Principle gas formers, Coliform, Clostridium, Heterofermentative lactic, Propianics bacillus, and so forth

Coliform, Clostridium, and Bacillus produce both H2 and CO2, while others produce just CO2.

Gas creation in milk is confirmed by froth at top of fluid milk by gas bubble caught in curd, by arrangement of curd.

Unreasonable gas creation causes breaking or breakdown of curd causing purported turbulent maturation of milk.

Clostridium perfringens basically causes turbulent maturation.


Proteolysis is accomplished at a reduced temperature by the annihilation of lactic corrosive bacteria or by the appropriation of presently provided corrosive by form and yeast.

Changed reason by proteolytic life form include:

Corrosive proteolysis in which corrosive creation and proteolysis happen all the while.

Proteolysis with little sharpness or even alkalinity.

Sweet souring which is brought about by renin like catalyst of microorganisms.

Slow proteolysis by intracellular catalyst of microorganisms later their autolysis.

Leftover proteolytic movement of some hotness stable proteinase.

Corrosive proteolysis is brought about by Micrococcus , Streptococcus faecalis var liquefaciens and some lactose aging proteolytic Bacillus species.

Sweet turning sour is brought about by Bacillus cereus.


Ropiness of milk happen both by bacterial and non-bacterial makes non-bacterial ropiness happens due thickness of cream or because of film of cousin or Lactalbumin during cooling.

Bacterial ropiness is brought about by foul capsular material of microscopic organisms which normally create at low stockpiling temperature.

Microscopic organisms creating ropiness in milk are Alcaligenes viscolactis, micrococcus freudenreichii, Enterobacter aerogenes, Klebsiella oxytoca, E. coli.

Change in milk fat:

Different microorganisms, yeast and shape hydrolyses fat of milk and cause rancidity.

Types of Proteus, Pseudomonas fragi, Staphylococcus, Bacillus, Micrococcus, Clostridium, and so on are lipolytic.

Pseudomonas fragi and Staphylococcus aureus produce reasonably heat safe lipase.

Soluble base creation:

Pseudomonas fluorescence and Alcaligene viscolactis produce salt.

Salt creation is because of development of alkali from urea and arrangement of carbonate from natural corrosive.

Flavor deformity:

Corrosive flavor: Acid flavor might be fragrant or sharp. Sharp flavor is brought about by creation of acidic corrosive formic corrosive, butyric corrosive and so on by Coliform and Clostridium. It is unwanted. Fragrant flavor is brought about by Streptococcus lactic and Leuconostoc when they become together. It is attractive.

Caramel or consumed flavor: It is brought about by Streptococcus lactic var. maltigens.

Severe flavor: It is brought about by proteolytic creature.

Other flavor: They incorporate natural flavor by Actinomycetes, fruity flavor by Pseudomonas fragi, latheriness by Pseudomonas sapolactic and so on

Shading imperfection: Growth of pigmented microorganisms and other living being give bothersome shading. A few models include:

Blue milk: It is brought about by Pseudomonas syncyaneum

Yellow milk: brought about by Pseudomonas synxantha and furthermore by flavobacterium.

Red milk: brought about by Serratia marcescencs and Micrococcus roseus.

Earthy colored milk: brought about by Pseudomonas putrefaciens and by enzymatic oxidation of tyrosin by Pseudomonas fluorescence.

ii. Deterioration of Butter:

Numerous deterioration microorganisms come in spread from cream or milk from which it is ready.

Shading deformity:

Some shading imperfection of margarine is non-microbial. They incorporate pink tone brought about by sulfur-dioxide refrigerant, surface obscuring brought about by vanishing of water from surface.

Staining brought about by microorganisms rely upon kind of organic entity. For instance, Stemphylium give dark spots, Penicillium give green spot, Alternaria or Phoma give earthy colored spots, Pseudomonas nigrificans give ruddy earthy colored spot and so on

Flavor deformity:

Cream and margarine have ability to assimilate dampness from encompassing.

Margarine might acquire such flavor from assimilation of flavor is created in spread during microbial development.

A few scents in margarine brought about by development of life forms include:

Suspiciousness brought about by Aeromonas hydrophila.

Ester like flavor brought about by Pseudomonas fragi.

Malodorous scent brought about by lipase creating organic entity.

Yeasty flavor brought about by yeast and so on

iii. Deterioration of Cheese:

Deterioration of cheddar happens either by mechanical harm or by microorganisms.

Microbial deterioration of cheddar happens during following three phases:

Decay during assembling:

During production of most cheddar lactic starter culture is added to complete lactic corrosive maturation.

On the off chance that these lactic starters are not viable or when pollution is weighty, many defiling living beings fill in it and get unfortunate changes cheddar. assuming starter culture isn't compelling, Clostridium and Bacillus develop and deliver openings and different changes.

Corrosive proteolytic microbes might deliver harsh flavor.

Leuconostoc might deliver openings in cheddar.

Different living being cause proteolysis, gas creation, vileness and off flavor that harm the nature of cheddar.

Cheddar with too low causticity as a result of disappointment of starter culture or on account of expansion of cream is regularly made vile by alcaligenes, melalcaligenes and Pseudomonas fragi.

Deterioration during aging:

During maturing, waste happens by chemical set free from autolyzed microscopic organisms or by development of microorganisms during aging.

Primary kind of decay contrasts with sort of cheddar.

In the greater part of cases, similar to gas creation by Clostridium, Heterofermentative lactis, Propionibacterium, Yeast and so forth cause eye arrangement or breaking of cheddar.

Clostridium likewise produce unfortunate flavor by creation of butyric corrosive.

Certain lactic streptococci give severe flavor.

A few microbes and yeast give sweet, fruity and yeasty flavor.

In cheddar with deficient causticity, rot is brought about by anaerobic Clostridium.

Microorganisms additionally caused staining on surface of cheddar.

Bluegreen or dark staining are created by response of H2S delivered by Microorganisms with metal or metallic salt.

Oxidation of tyrosine by microscopic organisms give rosy brown to grayish earthy colored tone.

Propionibacterium develop as yellow, pink or earthy colored hued complex.

Decay of completed cheddar:

Delicate cheddar is generally transitory and hard cheddar, for example, cheddar and swiss cheddar are generally steady.

Most normal decay creature of completed cheddar are molds.

They develop on surface or into openings or breaks and cause staining.

In some cases off flavor is likewise created.

A few molds causing decay of cheddar are:

Cladosporium: It becomes on surface and gives dark staining.

Oospora (Geotrichum): Oospora lactis (called dairy shape) develop on surface of delicate cheddar. For this situation, curd slowly becomes liquified under the development. Oospora crustacea give red spots.

Penicillium: Penicillium puberulum and other green spored species develop on surface or into openings and give green shading.

Monilia: Monilia nigra develop on surface of hard cheddar and give dark circles.

Conservation of milk and milk items from microbial waste

1) Reducing defilement:

Keeping nature of milk is further developed when defilement of milk is diminished.

Udder and neighboring regions ought to be washed with water and if conceivable, by germicidal arrangement prior to draining.

Hand and finger of milker ought to be perfect.

Dairy gear and other milk handling hardware ought to be cleaned appropriately.

Bundling of milk and milk items in can or bundles additionally keeps away from pollution.

2) Removal of microorganisms:

Microorganisms from milk are hard to eliminate.

High velocity centrifugation (called bactofugation at 10,000 rpm eliminates around almost 100% spores and over half of vegetative cell in addition to some protein.

In any case, bactofugation isn't done industrially for eliminating microorganisms from milk.

Form can be eliminated actually from surface of cheddar by rejecting or occasional washing.

3) Use of hotness:

For milk, pasteurization is used.

Cream can be warmed by infusing steam or by blend of steam infusion and clearing in an interaction called vacreation.

Heat is additionally applied for cheddar.

Cooking at 65.6oC or higher in softening of cheddar during produce lessens numerous waste microorganisms.

Vanished milk is canned and afterward warmed by steam under tension.

4) Use of low temperature:

Refrigeration temperature is suggested for milk or comparative item during capacity in plant during transportation and during stockpiling in home until utilization.

Fermenter milk and cheddar are chilled later their assembling and kept chilled until they arrive at the utilization.

Chilling stockpiling is most generally applied procedure of conservation of milk and milk item in home for momentary capacity.

5) Drying:

Many sorts of milk item are ready by drying or eliminating dampness from them.

There are two kinds of such item, one is dense item and the other is dry item.

One consolidated item is dissipated milk, in which 60% dampness is taken out, so that leftover high lactose focus in arrangement is inhibitory to miniature organic entities.

Mass dense milk, improved consolidated milk, semisolid spread are different instances of dense item.

Milk item ready in dry structure incorporate dry milk, frozen yogurt blend and so forth

Milk can be dried by drum drying or splash drying.

6) Use of synthetic additive:

There are two kinds of synthetic additives for example created and added additive significant in milk item.

Created corrosiveness in many aged milk item hinders development of numerous microorganisms.

Propionic corrosive create in swiss cheddar is inhibitory to shape.

Numerous compound additives are added from outside in many milk items.

Sorbic and propionic corrosive included cheddar and yogurt forestall surface waste by shape.

Sugar is added in improve consolidated milk to lessen Aw.

NaCl utilized in cheddar during assembling gives flavor and furthermore goes about as additive.

The expansion of H2O2 consolidate with gentle hotness treatment has been utilized for purification of milk for specific sort of cheddar. Some cheddar is additionally smoked.

Post a Comment