Activity and purity test of starter culture

Activity and purity test of starter culture

1. Assignment of Starter Culture and Fermented Dairy Products Topic – Activity and Purity Test for Starter Culture Submitted By- Saumya Sonal(SDT-04/22)

2. Activity and purity of starter culture are judged by different types of tests such as – 1 2 3 4 5

3. Organoleptic tests This test measure the qualities such as appearance , flavour and consistency a)Body- The body should be firm like custard .The texture should be such that the curd be able to retain its shape during gentle tapping of culture. b)Texture- It should not be lumpy and should have whey pockets and should be smooth and viscous after agitation. c)Taste- The taste should be acidic without bitterness and saltiness. d)Flavour- It should have typical aroma be free from off flavours and free from malty, bitter, rancid ,unclean ,yeasty ,fruity and putrid.

4. CHEMICAL TEST Various chemical parameter used for assessing the activity of starter include-

5. MICROBIOLOGICAL METHOD

6. PURITY TEST The purity of starter is evaluated by using microscopic or chemical test- 1.Microscopic examination- This is performed by gram staining. Gram negative bacteria ,spore formers , yeast and moulds and staphylococci should be absent. Lactic acid bacteria should be appeared as gram positive cocci or thin rods. 2.Catalase test- Add 3% of hydrogen peroxide to starter culture. Presence of effervescence indicates possible contamination of given culture .

7. ACTIVITY TEST 1.Titrable acidity test- The culture loose their activity due to acid injury if they are allowed to over ripen. A developed acidity in the range of 0.7 to 0.85% LA is optimal. 2.Horral Elliker’s test- It is used for mesophilic type of cultures. Prepare and sterilize the reconstituted milk. A titration value of 0.4 %LA or higher indicate that the culture should be well suited for cheese making . A titration value of 0.30 to 0.35%LA indicates a slow culture . Starter developing acidity of less than 0.30%LA is graded as inactive and it produce little or no acid in cheese .

8. 3. Creatine Test- It is common method used for indicating diacetyl content in flavour producing mesophilic cultures. The culture form a pink colour complex with creatine. 4. Dye Reduction Test – An excellent culture reduces the resazurin dye or methylene blue dye in 35 minutes and a good culture take 50 to 60 minutes.

9. Whitehead-Cox Activity Test It is an activity test stimulating some basic conditions of starter development in cheddar cheese and have used their method extensively for determining how well suited culture are for this purpose. The test procedure is shown in next slide……..