Skilled Base Elective MB 3511 Dairy Microbiology Practical 3. Microbiological quality of indigenous dairy products: i. Khoa ii. Kulfi iii. Shrikhand iv. Paneer v. Curd/ Buttermil

 3. Microbiological quality of indigenous (originating or occurring naturally in a particular place;)  dairy products: 

i. Khoa

 ii. Kulfi

 iii. Shrikhand

 iv. Paneer 

v. Curd/ Buttermilk

http://courseware.cutm.ac.in/wp-content/uploads/2020/05/6.-Microbiology-of-Traditional-Dairy-Products.pdf

http://cbseacademic.nic.in/web_material/Curriculum/Vocational/2015/Fluid_milk_processing_XII/Dairy-products-theory%20XII.pdf





Introduction

Since the production of various indigenous milk products is in the hands of ‘halwais’ (sweet makers) and rural areas, where unhygienic processing conditions are prevalent, the products are grossly contaminated. 

The contamination results into a considerable increase in the population of spoilage organisms, thereby, lowering the keeping quality of the products. 

The entry of pathogens which have great significance from the public health point of view is a major issue as the products are consumed by different sections of society including the vulnerable ones.

Dairy scientists have investigated microbiological quality of these products. Efforts are being made to bring improvement in maintaining standards of various indigenous milk products through technological modifications during their production.

i. Khoa ,  ii. Kulfi 

Microbiological Quality of Khoa, Burfi and Peda :

Khoa, like other indigenous milk products, can serve as a favourable medium for the growth of a variety of microorganisms due to its high moisture content and good nutritive value.

 The market khoa usually keeps well for 48 h under usual Indian conditions beyond which it deteriorates due to microbial action.

 These organisms gain access as contaminants from different sources in to product. 

The rapid spoilage of khoa is attributed to contamination with moulds from external sources. 

A number of investigations were carried out by different groups of workers on the microbiological status of khoa and khoa based sweets in different parts of the country.

Types of micro flora

Various groups of bacteria (acid producers, proteolytic, chromogenic, lipolytic, aerobic sporeformers, psychrotrophs, thermophiles, pathogens), yeasts and moulds have been reported to occur in khoa.

Psychrotrophic bacteria mainly Pseudomonas, Achromobacter, Flavobacterium and Alcaligenes, have been isolated from peda.

 On the basis of comparative analysis of khoa, burfi and peda, khoa contained higher population of yeasts and moulds than burfi or peda.

The composite microflora of market burfi and peda was studied in which bacteria, yeasts and moulds were isolated from both the products, though the proportion of yeasts and moulds was extremely low as compared to bacteria. Among the bacteria, Gram-positive (mainly cocci) predominated in both the products.

Microbiological Defects in Khoa

 Rancidity

On storing khoa under ambient conditions, the fat component is degraded by the action of microbial lipases. 

Such lipases are produced by certain lipolytic bacteria, yeasts and moulds. 

Both hydrolytic as well as ketonic rancidity might be produced depending on the nature of microbial activity.

Control measures

Storage of khoa under refrigerated conditions (below 10ºC) coupled with general hygienic measures during production are advisable.



iii. Shrikhand :

Microbiological quality of shrikhand

Analysis of market samples and laboratory made samples indicated that the product was free from coliforms.

 Quality control test of shrikhand showed not more than 85 x 105 cfu/g for yeast and mould count and absence of coliforms in 0.1 gram of shrikhand.

 The contaminants may enter the product during centrifuging / straining or subsequent conversion of chakka to shrikhand or through sugar.

 However, no food poisoning outbreak has been reported so far due to consumption of shrikhand.

iv. Paneer :

Microbiological quality of paneer

The microbiological quality of paneer, like other indigenous milk products, chiefly depends on the conditions of manufacture, subsequent handling, storage and sale of the product.

 The possible sources of contamination might be air, water, utensils, cutting knife, muslin cloth as well as persons handling the product. 

Hence, the number and types of microorganisms and their distribution in the product may vary depending on the location of the halwai shop, extent of exposure of the product to the atmosphere, temperature and period of storage etc.

 According to a survey conducted on the market quality of paneer obtained from Karnal and Delhi samples were found to contain heavy load of total bacterial population, coliforms and yeasts and moulds.

 Another study on market paneer from Ludhiana city indicated heavy contamination of the product with Staphylococci, 25% of which were found to be positive for coagulase and TDNase.

Microbial Defects in Paneer 

Due to high fat and moisture content, these products are prone to microbiological spoilage leading to rancidity (due to fat breakdown) and mouldy surface (due to mould growth).

 Storage of packaged  paneer at low temperature (5ºC - 10ºC) can check the rancid defect.

 The mould growth can be avoided by keeping moisture at an optimum level and by avoiding delays in the marketing and disposal of these products.

v. Curd/ Buttermilk


Dahi or Curd is an indigenous sour milk product obtained by lactic fermentation of cow or buffalo milk or mixed milk through the action of single or mixed strains of lactic acid bacteria. 

This does not include milk coagulated by the addition of acids and milk coagulating enzymes.

 The different starter used in the manufacture of Dahi includes Lactococcus. lactis, L. cremoris, Streptococcus thermophilus, Lactobacillus bulgaricus.and L. plantarum . 

A good quality Dahi is of firm and uniform consistency with a sweet aroma and clean acid taste. 

The surface is smooth and glossy and a cut surface is trim and free from cracks and air bubbles.

MICROBIOLOGY OF DAHI

Population and types of lactic acid bacteria occurring in samples of Dahi vary in different region of India.It has been reported that lactic acid bacteria count should be in the range 132-246x106 cfu/ml.The samples showed presence of a wide range of lactic acid bacteria species and nearly 46 isolates were reported those of S. thermophilus, four each were of L. lactis ssp. Lactis, L. lactis ssp and L. helveticus, 62 isolates were of L. delbruecki ssp. bulgaricus, and eight isolates of L. casei.

Reference:

https://old.fssai.gov.in/Portals/0/Pdf/Draft_Manuals/MILK_AND_MILK_PRODUCTS.pdf

https://scert.kerala.gov.in/wp-content/uploads/2020/06/10-diary%20technology.pdf

http://ecoursesonline.iasri.res.in/mod/page/view.php?id=6325

https://www.basu.org.in/wp-content/uploads/2020/05/8th-PPT-of-Microbiology-of-Indigenous-Milk-Products-Desiccated-Milk-Based-Products-1.pdf

https://www.basu.org.in/wp-content/uploads/2020/06/Microbiology-of-Indigenous-milk-products.pdf

http://ecoursesonline.iasri.res.in/mod/resource/view.php?id=148085

https://www.linkedin.com/pulse/microbiology-health-benefits-good-quality-indigenous-fermented

http://nsdl.niscair.res.in/bitstream/123456789/117/1/dairymicrobiology.pdf

http://nsdl.niscair.res.in/bitstream/123456789/117/1/dairymicrobiology.pdf

https://old.fssai.gov.in/Portals/0/Pdf/Draft_Manuals/MILK_AND_MILK_PRODUCTS.pdf


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