FIELD OF INVENTION
The present invention relates to a process for the continuous production of chhana. More particularly it relates to a process for the continuous production of chhana using a heat acid coagulation unit with a vacuum assisted strainer.
BACKGROUND OF THE INVENTION
Coagulation of milk is a common practice in all-dairy sectors. Coagulation is essentially the formation of a gel by destabilizing casein micelles causing them to aggregate and form a network, which partially immobilizes water and traps fat globules in the newly formed matrix. This may be accomplished by enzyme, acid or combination of heat and acid treatment. Accordingly, coagulation of milk is called enzymic coagulation, acid coagulation or heat-acid coagulation.
Chhana is one of the heat-acid coagulated products of milk. The concentrated and preserved milk solids in the form of chhana provide sound nutrition and novelty of flavor and texture to consumer.
With an estimated annual milk production of 91 million tonnes at an annual growth rate of 5 to 6 per cent, against the world's at 1 per cent, India today stands as the largest milk producing country in the world and it contributes about 15 per cent to the world milk production. Pattern of milk consumption indicates that about 6 per cent of milk, produced in the country is coagulated for production of chhana. Chhana forms the base and filler material for manufacture of a large variety of Indian milk sweets like rasogolla, rasamalai, sandesh, chhana-kheer, cham cham, gulabjaman, chhana poda etc. It has been reported that in India the market volume of chhana-based sweets is 1 million tonnes with a value of Rs 7*105 crores.
Chhana is a rich source of fat and protein. It also contains fat-soluble vitamins A and D. With high protein and low sugar content, chhana is highly recommended for diabetic patients. According to Bureau of Indian Standard (BIS, 1969), chhana should not contain more than 70 per cent moisture and milk fat content should not be less than 50 per cent of the dry matter. According to Prevention of Food Adulteration Rules (1976), chhana is defined as a milk product obtained by precipitating a part of milk solid by boiling whole milk of cow and or
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buffalo or a combination thereof by addition of lactic acid, citric acid or any other suitable coagulating agent and subsequent drainage of whey.
Paneer is an important heat-acid coagulated product of milk. Chhana forms the base material for preparation of paneer. Chhana, when pressed at a temperature higher than 60°C and chilled, is called paneer. Paneer is extensively used as an ingredient for preparation of various cooked dishes, sandwiches, sweets and snacks. In the absence of reliable statistics, it is believed that about 5 per cent of total milk produced in India is coagulated for production of paneer.
Chhana may be called as the Indian counterpart of cheese and casein. Chhana, is however more dissimilar in its native characteristics than cheese and casein. The differences in quality are caused by the temperature of coagulation and subsequent handling. Whereas low temperature is employed for both cheese and casein, usually boiling of milk is required for chhana preparation. Unlike cheese, freshly prepared chhana is free from acidic smell. Chhana resembles cheeses including ricotta, Queso Blanco and other related Latin American cheeses.
Traditionally, chhana is prepared by heating milk to its boiling point in an open vat or in a steam-jacketed kettle to denature the whey protein present in milk. The heated milk is allowed to cool to 75-80°C by constant stirring. The milk is added with a suitable coagulating agent like lactic acid, citric acid or calcium lactate solution with slow and constant stirring with the help of a ladle. The process is continued until the milk gets precipitated in lumps, which settle down at the bottom of the vat. The precipitation of milk involves destabilization of casein micelles aided by relatively higher temperature. Acid affects stability of casein directly by disturbing the charges carried by the particles and indirectly by releasing the calcium ion from colloidal calcium-caseinate-phosphate complex. The destabilization results in formation of large, firm and cohesive structural aggregates from the normal colloidal dispersion of casein micelles in which milk fat, other colloidal and soluble solids are entrained with deproteinated whey. The clear whey floating on the top is drained out by using a muslin cloth. The product thus obtained is called chhana. When the chhana is pressed in cloth-lined hoops, it knits together into a compact mass. The pressed chhana block after chilling is called as paneer. Yield and quality of chhana depends on the type of milk, heat treatment given to milk prior to acidification, temperature at the time of coagulation, acidity
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of milk-acid mixture and residence time of the coagulated chhana-whey mixture before separation of milk solids from whey.
Ancja et al., (1997) designed and developed a prototype continuous chhana-making device capable of producing 40 kg.h"1 of chhana. In the unit, milk was heated in a tubular heat exchanger. Thereafter the milk was mixed with sour whey of desired acidity. The mixed milk and whey was then pumped and circulated through holding coils for its complete coagulation and cooling. Ultimately, the product was brought into a mechanical strainer where it was drained to a desired moisture level.
Agrawal et al., (2002) developed a prototype unit for continuous dewatering and matting of acid coagulated milk curd to produce paneer in a continuous manner. The system consisted of a supply of pre-conditioned milk, acid supply and dosing, a transverse jet for mixer reactor, and a continuous dewatering and matting system for producing paneer cake. The machine was designed to manufacture paneer by employing twin-flanged apron conveyer cum filtering system. This equipment could also manufacture chhana by disengaging the pressing conveyor.
Coagulation of whole milk or skim milk is necessary for preparation of milk casein. In the process, the coagulated mass is continuously washed to reduce its lactose level and further dried to obtain dry casein. Following are some of prior arts, which describe the coagulation process for manufacture of milk protein i.e., casein.
Muller et al., (1967) described a continuous process for co-precipitation of milk in manufacture of milk proteins. In the unit, skim milk was preheated in a plate heat exchanger to about 68.3°C (155°F) before passing through a steam injector where the temperature was raised to 90.6°C (195°F). The heated milk was held in a holding vat. Following the holding, a pump was used to pump the heated milk from the vat. On the discharge side of the pump calcium chloride solution was injected through a spray in the opposite direction to the flow of milk. The mixture was then passed in a zigzag pipeline. Drainage of whey was carried out on a riffle chute attached at the discharge end of the pipeline.
Patent 15028 discloses a continuous process for manufacture of milk casein, wherein the skim milk is heated and mixed in a steam-jacketed pan with suitable mixing mechanism. The
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milk to be treated is mixed in this pan with necessary chemicals to effect the precipitation of the casein, the result being a mixture of casein and whey. Separation of whey is carried out in a revolving hollow drum, the curved surface of which is provided with a number of preferably radial compartments opening outwardly. The bottoms of these compartments consist of wire gauge. Within the drum, a pan for collecting the whey is provided and beneath it there is a second pan for receiving the mixture of whey and water.
Patent Applications US20020197369, US20030175394 and CA2298455 disclose an apparatus for the continuous coagulation of milk for production of soft protein foods, wherein the liquid protein source passes through a heat exchanger followed by one or more holding tubes and then into coagulation tubes. The product could exit onto a perforated conveyor belt, permitting drainage of liquid by-product.
US Patent No 1716799 discloses a continuous process for manufacture of milk casein. In the process, heated milk and acid solution are mixed in a mixing box, where the mixing elements are arranged in a zigzag manner. From the mixing box, the mixed milk and acid is allowed to pass continuously to a screw conveyer, the flight of the first and third quarter of the conveyer arc in form of helical ribbon and the remaining sections are solid.
US Patent No 2807608 discloses a continuous process for manufacture of casein from skim milk. In the process, heated milk and hydrochloric solution are mixed and allowed to flow in a helical tube. Separation of whey from casein is carried out in a drum or an endless belt placed at the outlet end of the helical tube.
US Patent No 2184002 describes a continuous process for manufacture of milk casein from skim milk. In the process, heated milk and acid solution are atomized and sprayed into a mixing tower through nozzles. The tower includes a plurality of downward inclined baffles, which are alternatively and oppositely arranged to provide a positive gravitational flow of the fluid mixture. Separation of whey is carried out in a screw conveyer having solid screw flights mounted at the bottom of the tower. The separator includes a strainer, which is secured to the conveyor casting.
US Patent No 2304429 describes a process for precipitation of skim milk solids for preparation of milk casein. According to the invention heated milk is introduced into a
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conical mixing chamber, where concentrated acid solution is applied at high pressure onto a disc. The disc is sloped to permit the acid to be forced out in a fan shaped fine film directed toward the side of the mixing chamber.
US Patent No 2228151 and 2190136 describe a process for manufacture casein from skim milk. In the process, precipitation of heated milk is carried out in a cylindrical chamber having a dome-shaped head and a frustoconical bottom terminating in an open outlet. The heated milk entering through a pipe into the center of the chamber is atomized when it comes in contact with compressed air. A pipe leading through the opposite side of the milk inlet delivers a precipitating gas or vapor into the chamber to milk with the milk spray and precipitates the casein. Removal of whey is carried out on a filter belt.
US Patent No. 2099379 describes a method of manufacturing casein. In the process, preheated milk is mixed with dilute mineral acid in a convergent mixing chamber. The acid is introduced into the mixing chamber through a nozzle. An inclined riffle trough with corrugated bottom is placed directly beneath the mixer to give extra coagulation time for the milk-acid mixture. The coagulated mass therefrom is allowed to pass on a vibratory screen and then between two rolls to remove the major portion of remaining whey.
US Patent No. 2369095 discloses a process for manufacturing casein where preheated skim milk is introduced to a funnel shaped mixing chamber. The milk swirls around the sides of the chamber in a rapid manner and passes through the fine film or spray of concentrated acid issuing under pressure. Precipitation of the milk-acid mixture is completed in a gear pump as a result of vigorous agitation of the mixture in the pump.
US Patent No. 2044282 describes a process for manufacturing casein. In the process the heated milk is mixed with acid solution in a vertical mixing chamber. The mixture is further mixed by passing it through an inclined flow box in which there arc a series of baffles staggeredly arranged in oppositely direction.
The main disadvantage of the procedures described in the traditional method of chhana making is that the gravity assisted draining of whey from the chhana-whey mixture does not facilitate quick and greater dewatering of chhana.
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Another disadvantage in traditional method lies in the reduced recovery of milk solids in chhana due to non-standardized process parameters.
One further disadvantage is that the existing methods adopted in most of the dairy sectors are cumbersome, time consuming, labor intensive and difficult for attaining high quality standard, which leads to microbial contamination of chhana and reduces its shelf life.
Due to the above-mentioned disadvantages, the existing methods of chhana making are too rudimentary to meet large-scale demands.
Thus there is a need to develop time, energy and/or cost efficient process suitable for industrial production of chhana and chhana based products.
OBJECT OF INVENTION
It is an object of the present invention to prov ide a process for continuous production of chhana comprising a vacuum assisted straining of whey.
It is a further object of the present invention to provide a heat-acid coagulation unit with a vacuum assisted strainer for the continuous production of chhana, which reduces both time and energy and recovers chhana with higher milk solids.
It is a further object of the present invention to provide an improved quality of chhana with reduced microbial contamination and increased shelf life.
It is yet another object of the present invention to provide a suitable packaging line incorporated at the end of the chhana production to facilitate packaging of chhana in a consumer friendly package.
SUMMARY OF INVENTION
According to an aspect of the present invention there is provided a process for continuous production of chhana comprising the steps of: (i) Mixing acid with heated milk;
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(ii) Passing the milk-acid mixture through a heat acid coagulation unit to give the required
residence time for coagulation of milk solids to chhana; (iii) Draining the whey through a vacuum assisted inclined strainer from the chhana-whey
mixture to attain moisture content of about 0.58 to 0.60 kg per kg chhana.
DETAILED DESCRIPTION
Chhana, one of the important heat-acid coagulated products of milk is generally prepared batch wise in small lots. The whey is separated from the coagulum i.e. chhana-whey mixture by gravity separation which results in a product of lower quality standards in terms of reduced milk solids, increased microbial contamination and reduced shelf life as described in literature.
The present invention describes a process for continuous production of chhana. In the process, a duplex plunger pump is used for metering and dosing milk and acid solution to the unit. A heat exchanger is used to heat the whole milk to 90-95°C prior to acidification. After mixing the acid solution with heated milk, the milk-acid mixture is allowed to move through a vertical column. The intermittent flow characteristic of the duplex pump facilitates proper mixing of milk and acid inside the column before curdling. The coagulated chhana-whey mixture from the discharge end of the column is kept in a holding chute prior to separation of milk solids by using an inclined strainer. Vacuum is maintained under the strainer to remove adequate amount of whey from the coagulated mass. The vacuum assisted strainer reduces the moisture content of chhana quickly and continuously to a value lower than that is obtained by gravity drainage, which is traditionally practiced. The recoveries in milk solids in chhana according to the present invention are higher than reported by various authors (Choudhary et al., 1998; Jonkman and Das, 1993; Iyer, 1978; Ray and De, 1953). Singh (1994) reported the recovery of milk solid and yield of chhana as 0.677 kg per kg and 0.232 kg per kg milk respectively while coagulating buffalo milk for preparation of chhana.
The present inventors have developed a continuous heat-acid coagulation unit with a vacuum assisted strainer for continuous production of chhana, which is advantageous in terms of reducing both time and energy so as to achieve an improved quality of chhana with higher milk solids, reduced microbial contamination and increased shelf life.
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This novel method of continuous production of chhana relates to a continuous milk
coagulation unit attached with a vacuum assisted whey drainage system.
Vacuum maintained under the strainer reduces the moisture content of coagulated chhana-
whey mixture to a value lower than that is obtained by gravity drainage.
The recoveries of milk solids in chhana according to the present invention are high.
BRIEF DESCRIPTION OF ACCOMPANYING FIGURES
Figure 1 illustrates the process lay out of continuous chhana production unit.
Figure 2 illustrates the assembly diagram of continuous chhana production unit.
Figure 3 illustrates the front view of the coagulation column.
Figure 4 illustrates the front and top view of holding and discharge sections.
Figure 5 illustrates the side view of strainer and its components.
Figure 6 illustrates the top view of strainer without cloth-lined-pcrforated sheet.
The numbers indicated in the above figures refer to the following:
1. Milk inlet 18. Vacuum chamber
2. Steam sealer 19. Guided apron
3. Helical tube heat exchanger 20. Chhana discharge chute
4. Saturated steam inlet 21. Whey drainage line
5. Pressure gauge 22. Chhana collecting bowl
6. Helical tube 23. Whey collecting tank
7. Condensate outlet 24. Sight glass
8. Cladding 25. Ball valve
9. Heated milk outlet 26. Whey outlet
10. Tripod stand 27. One way valve
11. Stopcock 28. Vacuum pump
12. Drain guide 29. SMS union connection
13. Acid solution inlet 30. Nylon cloth
14. Coagulating column 31. Cross drain guard
15. Holding chute 32. Inclined drain guard
16. Flapper 33. Slit
17. Strainer T|, T2, T3, and T4 - Thermocouples
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Dosing section
Dosing of milk and acid solution to the chhana-making unit is carried out by using a duplex plunger pump. The pump is provided with a manual adjustment of flow from 0 to 100% of the capacity of the pump. Varying the stroke length of the piston could vary the flow rate of milk and acid solution. Milk from storage tank is pumped to a heat exchanger (3). where it is heated and flows to a coagulation column (14), whereas acid solution (13) is directly pumped to the coagulation column (14). The intermittent flow characteristic of the pump creates an additional turbulence for the milk-acid mixture inside the coagulation column (14).
Milk heating section
Due to the small flow rate of milk in the developed unit, milk is heated to its boiling point prior to acidification by using a helical tube heat exchanger. The heat exchanger (3) consists of a 6 mm diameter and 5 m long stainless tube (6) placed inside a mild steel jacket. By using saturated steam (4) generated by an electrode boiler, milk at ambient temperature is heated to 90-95°C before acidification. Two thermocouples (T1 and T2) are provided at the milk inlet and outlet of the heat exchanger to indicate the temperature of milk before and after heat treatment. Pressure gauge (5) provided in the heat exchanger (3) indicates the saturated steam pressure inside the shell of the heat exchanger.
For the medium and large-scale production of chhana, plate heat exchanger (PHE) can be used for heating milk instead of a helical tube heat exchanger. In the case of heating by a PHE, milk can be heated to 90-95°C by using hot water. The hot water can be generated in the PHE under pressure.
Coagulation section
The coagulation column (14) consists of a stainless steel tube of 0.05 m diameter and 0.79 m length. A SMS connection (29) is provided at the bottom of the column. A stopcock (11) is provided at the bottom of the SMS connection (29). It allows drainage of whey and washed water through a drain guide (12) without opening the SMS connection. Heated milk and acid solution enter the column (14) at its lower end. The inlet of acid solution (13) is located little above that of milk (9) and placed opposite to each other so as to give good mixing of milk and acid solution. The milk is transformed into a mixture of chhana and whey when it travels up the column (14). The pulsating movement of the mixture, created by the dosing pump when it travels up the column (14), ensures the appropriate mixing of the milk and acid without breaking the lumps of solids formed by the milk solids. The time taken by the milk-

acid mixture to travel from the bottom to top of the column (14) is the coagulation time of the milk-acid mixture. The number of milk and acid inlets can be increased depending on the size of the coagulation column (14). Temperature of coagulation is indicated by the thermocouple (T4) placed in the column (14).
Holding section
The coagulum i.e. chhana-whey mixture from the discharge end of the coagulation column (14) moves onto an inclined chute (15). The cross section of the chute (15) is made trapezoidal, which squeezes the chhana mass gradually when it slides down to the straining and discharge section, expelling the whey out. A flapper (16) attached at the lower end of the holding section (15) controls the residence time of the coagulum. The operation of the flapper (16) is controlled depending on the desired residence time of the mixture.
Straining and discharge section
The straining and discharge section is attached with a perforated strainer lined with a nylon cloth on its top. The chhana-whey coagulum from the holding section (15) moves onto the perforated strainer (17). The perforated strainer has 7 mm diameter holes at a triangular pitch of 8 mm. The cloth has perforations of mesh size 180. A cylindrical vacuum chamber (18) is provided at the lower portion of the strainer (17). Two SMS union connections are provided at both ends of the chamber for its easy cleaning. This can be substituted by CIP cleaning in large-scale units. There is a slit (33) along the chamber (18) on its top surface. A flapper (16) is provided at the discharge end of the strainer for intermittent discharge of strained chhana to the chhana collecting bowl (22). The strained whey is discharged to a whey-collecting tank (23) through a whey drainage line (21). tight drain guards (32), four on each side of the silt, made up of food grade gasket are fixed below the perforated strainer and inclined at an angle equal to 60° in order to canalize the drained whey towards the centre of the strainer. A cross drain guard (31) made up of food grade gasket is placed at the end to hinder the whey to move towards the chhana-collecting bowl. A water ring type vacuum pump (28), connected to the tank (23) creates adequate amount of vacuum inside the chamber (18). A ball valve (25) located at the bottom of the tank (23) allows discharge of whey. A sight glass (24), provided in the tank (23) allows observation of the level of whey inside the tank (23). Tap water is supplied for sealing purpose. Cylindrical container (22) made of wire mesh lined with muslin cloth is used to collect the chhana from the chhana discharge chute (20). The capacity of the container (22) is decided depending on the requirement of chhana for subsequent operations.
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Strength of coagulant for milk coagulation
The value of pH required for the milk-acid solution at the time of coagulation and the amount of coagulant necessary for heat-acid coagulation of milk depends on the type of milk used. Singh (1995) expressed the relationship between the pH of milk acid solution Y and strength of acid solution Xc (kg lactic acid per 100 kg milk acid solution) during heat acid coagulation of milk by Equation (1).
Y = -3.402*Xc+6.95 ...(1)
Optimum pH for chhana obtained from cow and buffalo milk is 5.4 and 5.1 respectively. pH of coagulation principally regulates the moisture content and the body and texture of chhana, which are best obtained at the above pH (Soni et al., 1980). Iyer (1978), however, found that the most suitable pH for coagulating all type milk is 5.1.
Jonkman and Das (1993) and Singh (1995) used acidity of milk-acid mixture Xc as the parameter for coagulation of milk. They expressed the Xc at the time of coagulation by the following equation:
where, Xc (% lactic acid) is the acidity of milk-acid mixture at the time of coagulation, Cm (% lactic acid) is the acidity of fresh milk, wm (kg) is the weight of milk, b (%) is the strength of acid solution, M1a (90 g.mole"1) is the molecular weight of lactic acid, wa (kg) is the weight of acid solution, and A/a (g.mole1) is the equivalent weight of acid used.
Examples for calculating strength of coagulant
Example 1:
Coagulating agent: Citric acid (Ma = 64 g.mole1)
Milk used is cow milk (Cm = 0.15 kg lactic acid per 100 kg of fresh milk)
In the present design, ratio of flow rate of acid solution to that of milk was taken as 0.2 i.e. when wm = 1 kg.h1, wa = 0.2 kg.h1. Considering the pH of milk-acid mixture at the time of coagulation as 5.4 and substituting Y= 5.4 into Eqn (1), the value of Xc was found to be 0.455 kg lactic acid per 100 kg milk-acid solution. Substituting Xc = 0.455, Ma = 64, wm = 1 and wt
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= 0.2 into Eqn (2), the calculated value of the strength of citric acid in acid solution b was 1.41 i.e. 1.41 kg citric acid is required for making 100 kg acid solution. Similar calculation can be made for finding the strength of citric acid to coagulate buffalo milk.
Example 2:
Coagulating agent: Lactic acid (Ma = 90 g.mole')
Milk used is cow milk (Cm = 0.15 kg per lactic acid per 100 kg of fresh milk)
Proceeding as in Example 1, the strength of lactic acid in acid solution was found out to be 1.9 kg per 100 kg of acid solution. Similar calculation can be made for finding the strength of lactic acid for coagulation of buffalo milk.
EXAMPLES
Example 1:
Procedure for acid coagulation of milk for preparation of cbhana
1. The strainer is put on the discharge section and is properly fitted with the vacuum
chamber.
2. A solution of sodium hydroxide of strength 2% is prepared.
3. Cold water is put into the two storage tanks, one to be used for milk and the other for the
acid solution. Water is circulated through the unit by running the duplex pump. Leakage
in the whole system, working of thermocouples, pressure gauge, vacuum gauge, and
vacuum pump are checked. The functioning of all the valves attached in the unit is also
checked.
4. The steam is introduced into the shell side of the heat exchanger and a pressure of
lkg.cm-2 is maintained. The pump is run for about 5 minutes.
5. The cold-water circulation is stopped and the sodium hydroxide solution is poured into
the storage tank.
6. Circulation of the alkali solution to the unit is stopped after 5 minutes. Cold water is again
circulated through the unit.
7. The outlet temperature of water coming out of the heat exchanger is adjusted to 95°C by
controlling steam pressure at the shell side of the heat exchanger.
8. The coagulating solution is prepared as described in Eqns (1) and (2). The solution is
stirred thoroughly and kept in the acid storage tank.
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9. The milk is standardized, if required, and the standardized milk is put in the milk storage
tank.
10. The stroke length of piston of the pump is adjusted to get flow rate of milk and acid
solution in desired ratio.
11. The acid solution is pumped into the coagulating column first. Pumping of milk to the
heat exchanger is started only after the column is partially filled by the acid solution.
12. The vacuum pump attached to the whey-collecting tank is switched on.
13. The flapper attached at the discharge end of the holding section is opened and closed as
per the required holding time of chhana-whey,mixture.
14. At the discharge end of chhana, the strained chhana is scraped, if required to the chhana-
collecting bowl.
15. Whey level in whey-collecting tank is observed through the sight glass. When the whey
has nearly filled the tank, it is discharged to atmosphere by breaking the vacuum and
opening the whey discharge valve.
Test results for acid coagulation of milk for preparation of chhana
Flow rate of milk = 60 l.h-1
Initial temperature of milk = 21°C
Coagulating agent is citric acid
Flow rate of coagulating agent =12 l.h"1
Temperature of coagulating agent = 25°C
Temperature of heated milk = 95°C
Holding time of chhana whey mixture in the holding chute = 45 s
Vacuum level inside whey collecting tank = 540 mm of Hg
Holding time of chhana in the strainer = 1 min
Table 1: Average composition of milk, whey and chhana
Particulars of Cow milk Buffalo milk Mixed milk
analysis (5.2% fat) (6.3% fat) (5.8% fat)
Milk
Fat(%) 5.20 6.30 5.80
*SNF(%) 9.49 9.53 8.54
**TS(%) 14.69 15.33 14.34
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pH 6.50 6.61 6.51
Acidity (%) 0.15 0.156 0.152
Whey
Fat(%) 0.48 0.61 0.61
?SNF(%) 5.86 6.02 6.02
??TS(%) 6.34 6.64 6.64
pH 0.19 0.19 0.19
Chhana
Fat(%) 22.30 25.98 24.10
Protein (%) 18.01 16.23 16.30
Moisture (%) 59.77 58.12 58.76
•*TS(%) 43.23 45.24 45.24
pH 6.09 6.01 6.01
Note: *SNF = Solid-not-fat, **TS = Total solid!
Values are average of three trials
Table 2: Average recovery of fat and total solids at different stages of production of chhana
Particulars of analysis Cow milk Buffalo milk Mixed milk
(5.2% fat) (6.3% fat) (5.8% fat)
Yield (kg chhana. kg milk"1) 0.18 0.208 0.191
Milk solids recovery (kg solids in 0.62 0.67 0.65
chhana. kg solids in milk1
Fat recovery (kg fat in chhana. kg 0.93 0.923 0.925
fat in milk"1)
Protein recovery (kg protein in 0.928 0.934 0.938
chhana. kg protein in milk1) Note: Values are average of three trials
Example 2:
Procedure for acid coagulation of milk for preparation of paneer
All the procedures as described for preparation of chhana are followed including the
following steps.
1. Temperature of heated milk is maintained at 90°C.

2. The chhana from the chhana-collecting bowl is taken. The temperature of the chhana
should not be below 60°C.
3. The chhana is put in paneer moulds (15*6*6 cm3) and pressure at 0.07 kg.cm"2 is applied
for 30 min.
4. The pressed chhana is cooled in chilled water for 45 min.
Table 3: Average composition of milk, whey and paneer
Particulars of Milk Whey Paneer
analysis
25.98
SNF(%) 9.53 5.90 24.77
TS(%) 15.73 6.51 50.75
pH 6.51
Acidity (%) 0.153
Note: *SNF = Solid-not-fat, **TS = Total solids
Values are average of three trials
The average recovery of fat and protein (Table 2) is above 90% with the developed process, but there are many operational factors which influence the recovery i.e., pH of milk-acid
mixture at the time of coagulation, time and temperature combination of milk-acid mixture
and residence time of chhana-whey mixture before separation of milk solids from whey.
With the above-developed process, the yields of chhana are 0.18, 0.208 and 0.191 kg per kg milk for cow milk, buffalo milk and mixed milk having 5.2 and 6.2 and 5.8% fat respectively (Table 2). The corresponding recoveries in milk solids are 0.62, 0.67 and 0.65 kg per kg solids in milk (Table 2). This higher recovery and yield of chhana was due to the higher fat content (6.3%) in the milk used for coagulation. The recovery in milk solids is basically dependent on percent fat present in milk, used for chhana preparation.
The vacuum maintained under the strainer reduces the moisture content of chhana-whey mixture to a level of 0.58 to 0.60 kg per kg chhana (Table 1). Draining of whey by using vacuum allows the chhana making process quick and continuous.

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The process of the present invention reduces 40% of labor cost assdciated with heating milk, cooling the heated milk and draining of whey manually, which is practiced in traditional method of chhana preparation.
Energy saving involved with the continuous chhana making process are significant and have been estimated to exceed 40% compared to traditional process. Such savings are achieved by avoiding heating citric acid solution and cooling the heated milk to the coagulation temperature. The saving in energy is further increased by recirculating the deproteinated hot whey from the whey-collecting tank through the regeneration sectibn of the heat exchanger.
The process of the present invention reduces level of contamination of product due to totally self-contained process resulting in a product having longer shelf life.
Cleaning and sanitation of the unit
1. Tap water is circulated for 10 minutes through the system.
2. 1 per cent nitric acid solution at 80°C is circulated for 10 minutes followed by water
rinsing and then 1 per cent NaOH solution is allowed to flow at the same temperature for
another 10 minutes.
3. The system is washed by circulating hot water at 60°C for about 5 minutes.
4. The system is cooled to room temperature by circulating tap water for 10 minutes.

WE CLAIM
1. A process for continuous production of chhana comprises the steps of:
(i) Mixing acid with heated milk;
(ii) Passing the milk-acid mixture through a heat acid coagulation unit to give the
required residence time for coagulation of milk solids to chhana; (iii) Draining the whey through a vacuum assisted inclined strainer from the chhana-
whey mixture to attain moisture content of about 0.58 to 0.60 kg per kg chhana
2. The process for the continuous production of chhana as claimed in claim 1 wherein the
heated milk is at a temperature of 90-95°C.
3. The process for the continuous production of chhana as claimed in claim I wherein the
milk is selected from cow milk or buffalo milk or mixed milk.
5. The process for the continuous production of chhana as claimed in claim 3 wherein the
cow milk has a fat content around 5.2%.
6. The process for the continuous production of chhana as claimed in claim 3 wherein the
buffalo milk has a fat content around 6.2%.
7. The process for the continuous production of chhana as claimed in claim 3 wherein the
mixed milk has a fat content around 5.8%.
8. The process for the continuous production of chhana as claimed in claim 1 wherein the
milk-coagulating agent is selected from citric acid or lactic acid.
9. The process for the continuous productionjof chhana as claimed in claim 1 wherein the
pH of coagulation is around 5.0-5.5.
10. The process for the continuous production of chhana as claimed in claim 1 wherein the
recoveries in milk solids are around 0.62, 0.67 and 0.65 kg per kg solids in milk
corresponding to cow milk, buffalo milk and mixed milk respectively.
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11. The process for the continuous production of chhana as claimed in claim 1 wherein the
chhana obtained has reduced microbial contamination and increased shelf life.
12. The process for the continuous production of chhana as claimed in claim 1 wherein the
chhana is used for the preparation of paneer.