preparation of yoghurt
TRANSCRIPT
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Preparation of yoghurt
Bangaru. karthikDept .of microbiology
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Introduction
• Fermented milk product
• Word yoghurt comes from turkish word “jugurt”
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Mostly made from……
• Normal milk
• Skimmed milk
• Fortified milk
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Milk source
• Mostly from cow • Rarely from goat and sheep
• Limitation: milk should be free from antimicrobial substance
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Milk used in preparation
• Whole milk• Partially defatted milk• Condensed skimmed milk• Cream• Non fat dry milk• Milk is condensed by removing 15-20% of
water in vaccum pan• Milk fat levels are 1-3.25%
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Limitation of milk
• Infected milk is not used
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Additives permitted
• Nutritive carbohydrate sweetners
• Coloring agents
• Stabilizers
• Fruit preparation for flavouring yoghurt
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Starter culture
• Lactobacillus bulgaricus
• Streptococcus thermophillus
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Sweeteners
• Majorly used : Sucrose• Others : corn sweetners and honey
• The level of sucrose effects preparation– Production of lactic acid– Flavour of yoghurt
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Sucrose…..
• It can be added either in – wet form – dry form– Granulated from– Free flowing form– Crystalline or liquid form
– 67% of sucrose can be added
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Other sweeteners
• Non- nutritive sweetners eg: ca-saccharin• Lactose, glucose & galactose is also
suggested
• Commercial yoghurt have – 4.06% lactose– 1.85% galactose– 0.05% glucose– pH = 4.1
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Stabilizers • Main function :
• Smoothness in body and texture
• To impart gel structure
• To reduce wheying off
• Increase the shelf life
• Provides a degree of uniformity
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Charecters of a good stabilizer
• Should never effect flavour
• Should be effective at low pH
• Should be easily dispersed
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Different stabilizers
• Gelatin
• Sea weed gums
• Algin & sodium alginate
• carrageenan
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Fruit preparations in yoghurt
• Different fruit preparation are blended to satisfy market requirement
• Generally 15-20% of low levels of fruit are present
• Depending on their usage yoghurt is classified into three types
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Different types of yoghurt
• Eastern sundae style
• Western sundae style
• Swiss style yoghurt
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Eastern sundae style
• Also called fruit on bottom
• 59ml of fruit preserves at bottom followed by 177ml of inoculated yoghurt mix
• No flavour or sweetners are added
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Western sundae style
• Fruit preserves or special fruit preparations forms the bottom layer
• Top layer has yoghurt containing sweetners with the flovour and color
• It is identical to eastern sundae style
• Flavor level is usually 2-4% in the top layers
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Swiss style yoghurt
• Also known as continental style or french style or stirred yoghurt
• Fruit preparation is thoroughly blended in yoghurt
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Fruits used are….
• Strawberry• Raspberry• Bluberry• Apples, peaches, orange, lemon
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Starter culture
• Important in preparation
• Should be…• Free from contaminants• Vigorous growth in yoghurt mix• Good flavour• Body and texture production• Resonable resistance to pahges and antibiotics
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Starter cultures used are….
• Lactobacillus bulgaricus• Streptococcus thermophilus
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• Starter culture
– Gives flavor and texture production
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• The lactobacilli grows first and liberate the amino acid glycine and histidine
• This stimulate the growth of streptococci
• Formation of lactic acid, acetaldehyde, acetic acid and diacetyl decides the flavour of yoghurt
• Sterptococci lowers the pH to 5.5
• Then lactobacilli reduces pH still 3.8 – 4.4
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• Homogenization and high fat content gives smooth texture
• Gassiness in yoghurt is due to contamination by some bacilli
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Types of yoghurt
• Plain yoghurt– Set type – Stirred type
• Fruit flavored yoghurt– Eastern sundae style – Western sundae style
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Set type yoghurt
Low fat milk, skim milk, non fat dry milk
Standardized yoghurtMilk fat – 1-2%MSNF – 12.5%
Pasteurize at 95°CFor 30 min
Homogenize at 60°C
Mix in holding VAT43°C
Bulk starter
Packing container
Incubate containerAt 43°C pH 4.5
Cool & store plain Yoghurt at 5°C upto
3-4weeks
Cool to 43°C
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Low fat milk, skim milk, non fat dry milk
Standardized yoghurtMilk fat – 1-2%MSNF – 10.5%
Stabilizers – 0.7%
Pasteurize at 95°CFor 30 min
Homogenize at 60°C
Mix in holding VAT43°C, pH 4.5
Bulk starter
Packing container
Cool & store plain Yoghurt at 5°C upto
3-4weeksCool to 43°C
Cool to 25 °C
Stirred type of yoghurt
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Low fat milk, skim milk, non fat dry milk
Standardized yoghurtMilk fat – 1-2%
MSNF – 10 -12.5%
Pasteurize at 95°CFor 30 min
Homogenize at 60°C
Mix in holding VAT43°C
Bulk starter, fruit syrupAnd color for western style
Packing container, 1 part fruit& 3-4 parts yoghurt
Incubate containerAt 43°C pH 4.5
Cool & store plain Yoghurt at 5°C upto
3-4weeks
Cool to 43°C
Sundae style
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Low fat milk, skim milk, non fat dry milk
Standardized yoghurtMilk fat – 1-2%MSNF – 10.5%
Stabilizers – 0.7%
Pasteurize at 95°CFor 30 min
Homogenize at 60°C
Mix in holding VAT43°C, pH 4.5
Bulk starter
Packing container
Cool & store plain Yoghurt at 5°C upto
3-4weeksCool to 43°C
Swiss style
Cool to 25 °C
Yoghurt fruit is added