Preparation of Dairy Products

Khoa, Paneer, Chhena and Dahi

Flowchart for Commercial Fluid Milk Processing

Milk condensate is made by the addition of sugar to whole milk and the removal of water from the milk to about one-half of its original volume. The product is canned or packaged in containers without sterilization, with the sugar acting as a preservative.

There are 3 types of khoa based on its moisture content;

• Pindi Khoa is used for the preparation of Burfi and Peda
• Dhap Khoa for Gulabjamun
• Danedar Khoa for Kalakand

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A continuous khoa making machine having steam jacketed drum heater/direct heater with a rotary scarper is used for Khoa making on commercial scale. A product outlet valve has been designed for large scale production of khoa.

1. Khoa

Khoa is a partial dehydrated whole milk product. It is prepared by the action of heating and stirring the milk continuously until it reaches semi-solid (doughy) consistency.

It is an important base for the preparation of various sweets.

Khoa making machine

The milk fat content of the finished product should not be less than 20% (IS: 4883, 1968)

5- 10°C is preferred as it is found to extend the shelf life of Khoa

Composition of Khoa

Pindi

• Fat: 21-26

• Moisture: 31-33

• Sweets: Burfi, Peda etc.

Dhap

• Fat: 20-23

• Moisture: 37-44

• Sweets: Pantooa, Gulabjamun etc.

Danedar

• Fat: 20-25

• Moisture: 35-40

• Sweets: Kalakand,

Gourd barfi etc.

1. Take 5 liters of milk in iron pan on non-smoky fire and boil the milk.
2. Start the stirring of milk continuously. Scrap all the parts of the pan covering the milk.
3. Stir the milk at about 100 rpm for constant evaporation and progressive thickening of milk.
4. The thickened mass shows spurting, abrupt change in colour and consistency; at this stage; vigorous stirring and desiccation are continued till the viscous product reaches a pasty consistency and leaves the sides of pan.
5. Give close attention and reduce the temperature to 80-88 C and the final product is ready when it shows signs of sticking together.
6. Remove the pan from the fire; work the contents up and down, spreading to the cooler part of pan. After some time remove the khoa on bakery paper and make circular pat. Weigh the quantity of khoa

Khoa yield: 18% from cattle milk and 20% from buffalo milk

Paneer refers to the indigenous variety of acid coagulated milk solids and is extensively used as an ingredient with vegetables in Nepal and India.

Analogous to Paneer is cottage cheese prepared by acid coagulation in western countries.

Procedure:�1. Take 5 L fresh buffalo milk and standardize to 6% fat.

2. Heat the milk to 90°C for 5 minutes and promptly cool it to 80°C.

4. Add coagulant slowly, while it is continuously stirred till clear whey separates out (1.8- 2.0 gm citric acid for 1 liter milk)

5. Allow the coagulant to settle down for 5 minutes and drain the whey through muslin cloth.

6. Do not allow to go down the temperature of the whey below 65°C during Straining.

2. Paneer

7. Collect coagulum and fill in hoop lined with strong and clean muslin cloth.�8. Fit up wooden planks on both openings of hoop.�9. Apply pressure (3 kg/sq. cm) on the top of the hoop for 15 to 20 minutes.�10. Remove pressed Paneer from hoop and cut into 6 to 8 pieces.�11. Immerse the pieces of Paneer in chilled brine for 2 to 3 hours for hardening.

12. Remove chilled Paneer and drain the water. Wipe the pieces and wrap in parchment and store in refrigerator.�

Calculations:�                                                Wt. of Paneer�% recovery of Paneer = --------------------------  x  100�                                                 Wt. of milk

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1L of cow's milk makes 200 gm paneer while same from buffalo milk makes 225-250 gm

This coagulated curd mass is called CHHENA

Composition of Paneer

Chemical and physical characteristics of Paneer

As per 10^th Amendment Regulations, 2016, Food Safety & Standards Authority of India (FSSAI) has specified microbiological requirements for process hygiene and food safety.

Microbiological characteristics

Defects of Paneer, its cause and preventive methods

Chhena is the coagulated milk which has not been set and pressed like paneer.

Hence, chhena is more moist than paneer and whenever we want to make sweets like sandesh or rasmalai or kalakand or rasogulla, we should prepare  chhena fresh and use it.

3. Chhena

• Yoghurt is a fermented dairy product made by blending milk with various ingredients that provide flavor and colour.
• The bacteria used in youghurt making is known as starter or cultures. Fermentation of sugars in milk by these bacteria produce lactic acid, which acts on milk protein to give yoghurt its characteristic texture and tart flavor.
• Yoghurt is produced using a culture of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus.
• Initial use is documented in Mesopotamia thousands years ago.

4. Yoghurt

Dahi is the product obtained from pasteurized milk by souring, using lactic acid or other bacterial culture. Dahi may contain added cane sugar.

• Yoghurt is made with variety of ingredients including milk, proteins, fats, sugars, stabilizers, emulsifiers, fruits, flavours and bacterial cultures.
• The main ingredients in yoghurt is milk. The types of milk used depends on the type of yoghurt- whole milk for full fat yoghurt, low fat milk for soft yoghurt and skim milk for non-fat yoghurt
• Stabilizers may be used in yoghurt to improve the body and texture by increasing firmness, preventing separation of whey and helping to keep the fruit cubes uniformly mixed
• Common stabilizers: Alginates (Carrageenan), gelatines, gums (locust bean, Gaur), pectin and starch

Ingredients

These are the beneficial active growing desirable strains of selected microorganisms which are responsible for production of desirable characteristics as acidity, flavour and aroma in dairy products. The function of the starter culture is:

• To ferment lactose to lactic acid
• To production of proteolytic and lipolytic enzymes- useful in cheese making
• To produce bacteriocins- inhibit the growth of pathogenic bacteria
• To produce specific colour and to enhance viscosity and firmness of the final product

Starter culture

• The main starter culture in yoghurt are Lactobacillus bulgaricus and Streptococcus thermophilus.
• The function of the culture is to ferment lactose to produce lactic acid. The increase in lactic acid decrease pH and causes the milk to clot or form soft gel that is characteristics of the yoghurt
• Other bacterial cultures, such as L. acidophilus, L. casei and Bifidobacterium may be added to yoghurt as a probitic cultures
• These bacteria are ultimately responsible for the flavour and aroma of the final product. To achieve this, they produces acetic acid, diacetyl compounds, acetoin and acetaldehyde in addition to lactic acid

Classification of starter culture

The mixed starter culture in yoghurt are Streptococcus salivarius sub. thermophilus and Lactobacillus delbruekii sub. bulgaricus.

• Produces lactic acid and reduce pH (precipitates casein)
• Produce flavour substances (acetaldehyde, acetic acid and diacetyl)

Synergistic growth of yoghurt starters

• SST start the reaction, grow fast and produce acid and CO₂, which stimulates growth of LDB
• LDB prodecues more acidity (pH4) and proteolytic enzymes that results in small peptides and amino acids, aging stimulating SST growth
• SST:LDB is 1:1 or 2:1
• Added at 2% v/v for 4-6 h at 45°C (short set) or at 0.5% for 14- 16 h at 30°C (long set but rarely used)

Starter cultures used in yoghurt making

Initial Treatment of Milk

• Clarification to remove somatic cells and solid impurities
• Thermalization at 60–69 °C for 20–30 s
• For killing vegetative microbes
• Partial inactivation of some enzymes

Standardization

• Milk composition adjusted for desired fat and solids content
• Fat content ranges from 0.1%–10%
• Addition of skim milk or milk fat
• The separation of fat from milk
• Evaporation
• SNF of yogurt ranges from 9% to 16% adjusted by addition of
• Skimmed milk powder,
• Milk concentrate,
• Whey powder,
• Sodium caseinate powder
• Sugars, sweeteners and stabilizers (gelatin, pectin, agar, starch) added

Steps of Yogurt Processing

Pasteurization

• Pasteurized at 85°C for 30 minutes or at 95°C for 10 minutes
• Denature the whey proteins, form more stable gel
• Eliminates the number of pathogenic and spoilage organisms in the milk

Homogenization

• Homogenized at 2000 to 2500 psi
• Thorough mixing and improve yogurt consistency

Cooling

• Cooled to 42°C for the starter culture growth

Inoculation with Starter Cultures

• Fermentation culture added in a conc. of about 2%

Incubation

• Incubation at 42°C until a pH 4.5 reached
• Fermentation form a soft gel and characteristic flavor

Cooling

• At pH 4.5 yogurt cooled to 15-22°C to stop the fermentation
• Add Fruit & Flavors
• Packaging

Fig. Block diagram showing production steps for set, stirred and drinking yoghurt