WO2023218345A1

WO2023218345A1 - Process and system for preparation of khoa

Info

Publication number: WO2023218345A1
Application number: PCT/IB2023/054787
Authority: WO
Inventors: Tapas Chatterjee
Original assignee: Tapas Chatterjee
Priority date: 2022-05-11
Filing date: 2023-05-09
Publication date: 2023-11-16

Abstract

The invention relates to a process for obtaining improved quality khoa comprising the steps of heating concentrated milk having solid content in the range of 40 to 55% to a temperature in the range of 90 to 120oC to obtain hot concentrated milk; holding the concentrated milk at a temperature in the range of 90 to 120oC for a time period in the range of 15 to 60 minutes to obtain hot denatured milk; passing the hot denatured milk through a Scraped Surface Heat Exchanger to obtain solid mass; and removing steam from the solid mass to obtain khoa. The invention furthermore provides a system for producing the improved quality khoa.

Description

PROCESS AND SYSTEM FOR PREPARATION OF KHOA

FIELD OF THE INVENTION:

The invention relates to a process and a system for preparation of khoa.

BACKGROUND OF THE INVENTION:

Khoa also known as khoya, khawa, kava or mawa is a versatile intermediate base for a wide range of sweets such as barfi and peda, khoa and occupies a prominent place in traditional diary products sector. Khoa has been defined under the PFA as the product obtained by rapid drying of milk obtained from cow or buffalo or goat or sheep or milk solids of a combination thereof. The milk fat content shall not be less than 20 percent of the finished product. Khoa may contain citric acid not more than 0.1 percent by weight.

Koha is produced by boiling milk in a large open pan generally called “Kadai” which is used for concentrating milk until it turns into a dough like consistency using a metal scrapper called “Khunti” to prevent burning of milk in the Kadai. The Kadai is scrapped vigorously particularly at end of the concentration process to prevent browning and burning of milk solids. The concentration of milk is usually carried out by heating it in a Kadai placed on the top of an open fire using coal, charcoal or a gas stove.

The traditional method of manufacturing khoa using Kadai is either done by individual halwais (Sweet Makers) or in a Khoa Bhatti (Hearth). In the Bhatti type manufacturing process, the fire is lit at end of a long Bhatti and the flue gases escape from the other end of the Bhatti. The Bhatti has several chulhas (stove) to accommodate multiple number of Kadais usually the first Kadai is used for boiling milk and when the milk starts boiling this Kadai is moved on to the next Bhatti where partial concentration takes place and a partial concentration is usually done by moving the Kadai to several subsequent chulhas. During the final stages of khoa making, khoa is gathered in the form of a pat which is spread over and over again on the inner surface of the Kadai for concentration. At this stage the khoa losses its stickiness after the desired level of consistency has been obtained a pat of khoa is made, which is usually about a kilo and is put into a katora for cooling and hardening. The final pat of khoa is stamped by the khoa maker with an engraved metal stamp to establish the identity of the khoa maker.

The traditional method of manufacturing khoa suffers from many limitations such as low heat transfer rates, high fouling behavior, batch to batch variation in product quality, poor hygienic, poor sanitary standards and lot of stress on the operator. Thus, several attempts have been made to manufacture khoa using mechanical equipment with the objective of industrializing its manufacturing.

One of the prominent industrial methods for manufacturing khoa is described in Indian Patent Application No. 583/DEL/2010. As per the document, fresh milk is fed to a system comprising three stage thin film scrapped surface horizontal heat exchanger for the purpose of continuous manufacturing of khoa.

National Dairy Research Institute (NDRI), Karnal has successfully tries out a batch processor based on the principal of a conical vat. This conical vat simulates the action of a Khunti on a Kadai by using a rotary scrapper in a conical vat. The entire heating surface is scrapped continuously to avoid burning. The limited capacity of machine and its batch processing nature are the limiting factors.

Apart from the above, Inclined Scraped Surface Heat Exchanger (ISSHE) is also used for continuous manufacture of khoa by National Dairy Development Board (NDDB). Concentrated milk of 42 to 45% total solids is used as feed in this machine and its inclination permits the formation of a pool of boiling milk critical to formation of khoa.

Thin Film Scraped Surface Heat Exchanger (TSSHE) system has been developed at NDRI for the continuous manufacture of khoa and it consists of two sets of Scraped Surface Heat Exchangers (SSHE) which are arranged in a cascade fashion. In this machine milk is concentrated in first SSHE to about 40-45% Total Solids and finally to khoa in the second SSHE.

It was found that the khoa manufactured as per traditional processes contains about 65-70% Total solid content and the remaining is the moisture; while the khoa manufactured by the industrial methods contain more than 75% Total Solid content and the remaining is the moisture. Also, the khoa produced by the industrial methods are sticky and lumpy and are lacking in grains. Thus, despite the fact that the khoa manufactured by the industrial methods is having higher amount of solids as compared to the khoa prepared by traditional processes, it is not as firm / grainy as the khoa prepared by traditional processes. Apart from the above, khoa having higher quantity of solid is disadvantageous for the reason that it fetches lesser profit margin. Also, the khoa produced by the industrial methods are of uneven color. As a result only a minuscule quantity of khoa produced in the country using mechanized equipment for its manufacture.

Thus, there exists a need to provide an improved process and system for preparation of khoa which addresses the aforesaid disadvantages.

SUMMARY OF THE INVENTION:

This summary is provided to introduce a selection of concepts in a simplified format that are further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention, and nor is it intended for determining the scope of the invention.

The present invention provides a process for preparation of khoa comprising heating concentrated milk having solids in the range of 40 to 55% to a temperature in the range of 90 to 120°C to obtain hot concentrated milk; holding the concentrated milk at a temperature in the range of 90 to 120°C for a time period in the range of 15 to 60 minutes to obtain hot denatured milk; passing the hot denatured milk through a Scraped Surface Heat Exchanger to obtain solid mass; and removing steam from the solid mass to obtain khoa.

The present invention provides a system for preparation of khoa comprising a heating device for heating concentrated milk having solids in the range of 40 to 55% to a temperature in the range of 90 to 120°C to obtain hot concentrated milk; a holding device being in operational interconnection with the heating device, the holding device being adapted to hold the concentrated milk at a temperature in the range of 90 to 120°C for a time period in the range of 15 to 60 minutes to obtain hot denatured milk; a Scraped Surface Heat Exchanger being in operational interconnection with the holding device, the Scraped Surface Heat Exchanger being adapted to produce a solid mass from the hot denatured milk; and a steam removal equipment being in operational interconnection with the Scraped Surface Heat Exchanger, the steam removal equipment being adapted to remove steam from the solid mass to obtain khoa.

To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES:

In order that the invention may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying drawings. The figures together with a detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present invention where:

Figure 1 shows a flow chart of a process for making khoa from milk in accordance with an embodiment of the invention;

Figure 2 shows another detailed flow chart of a process for making khoa from milk in accordance with an embodiment of the invention;

Figure 3 shows a schematic diagram of a system for making khoa from milk in accordance with an embodiment of the invention.

It may be noted that to the extent possible, like reference numerals have been used to represent like steps in the drawings. Further, skilled artisans will appreciate that the steps are illustrated for simplicity in the form of blocks, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

DETAILED DESCRIPTION OF THE INVENTION:

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.

As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises... a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

As used herein, and unless the context dictates otherwise, the terms "coupled to", “connected to”, “operably connected to”, “operatively connected to” are intended to include both direct connection / coupling (in which two elements that are coupled / connected to each other contact each other) and indirect coupling / connection (in which at least one additional element is located between the two elements). Therefore, the terms "coupled to" and "coupled with" are used synonymously. Similarly, the terms “connected to” and “connected with” are used synonymously.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The methods, devices, and examples provided herein are illustrative only and not intended to be limiting.

The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims. Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Referring to Figure 1, there is illustrated a process (100) for preparing khoa from milk in accordance with an embodiment of the invention. The process comprises heating (102) concentrated milk having solids in the range of 40 to 55% to obtain hot concentrated milk having a temperature in the range of 90 to 120°C; holding (104) the hot concentrated milk at a temperature in the range of 90 to 120°C for a time period in the range of 15 to 60 minutes to obtain hot denatured milk; passing (106) the hot denatured milk through a Scraped Surface Heat Exchanger to obtain solid mass; and removing (108) steam from the solid mass to obtain khoa.

In an embodiment of the invention, the concentrated milk having solids in the range of 40 to 55% is obtained from raw milk having solid content in the range of 10 to 15%. As shown in Figure 2, the process (100) for preparing khoa from milk may therefore comprise a step of concentrating (110) raw milk having solids in the range of 10 to 15 % to obtain concentrated milk having solids in the range of 40 to 55%. Also, in an embodiment of the invention, khoa thus obtained is cooled and molded (112).

In an embodiment of the invention, the step of concentrating (110) raw milk having solids in the range of 10 to 15 % to obtain concentrated milk having solids in the range of 40 to 55% is performed in an evaporator. In an embodiment of the invention, the evaporator is a singleeffect evaporator or a multi-effect evaporator.

In an embodiment of the invention, the step of heating (102) concentrated milk having solids in the range of 40 to 55% to obtain hot concentrated milk having temperature in the range of 90 to 120°C is performed in a heat exchanger. In an embodiment of the invention, steam is used as the heating medium for heating (102) the concentrated milk.

In an embodiment of the invention, the step of holding (104) the hot concentrated milk at a temperature in the range of 90 to 120°C for a time period in the range of 15 to 60 minutes to obtain hot denatured milk is performed in one or more holding tube. In an embodiment of the invention, the one or more holding tubes are provided with insulation. In an embodiment of the invention, the Scraped Surface Heat Exchanger is maintained at a temperature in the range of 90 to 120° C to effect conversion of the hot denatured milk into solid mass.

In an embodiment of the invention, wherein the solid mass thus obtained contains entrapped steam.

In an embodiment of the invention, the steam entrapped in the solid mass is removed by subjecting the solid mass to a pressure less than atmospheric pressure.

In an embodiment of the invention, the solid mass is subjected to a pressure less than atmospheric pressure in a flash vessel.

It has been observed that it is imperative to hold (104) the hot concentrated milk at a temperature in the range of 90 to 120°C for a time period in the range of 15 to 60 minutes. If either the temperature or the time is substantially outside the respective ranges, the quality of the product in terms of the texture and the solid content is adversely affected.

Apart from maintaining the temperature being in the range of 90 to 120°C for the time period being in the range of 15 to 60 minutes, both the time and the temperature cannot be simultaneously at their lower extremity i.e. when the time is 15 minutes, the temperature cannot be 90°C. Also, apart from maintaining the temperature being in the range of 90 to 120°C for the time period being in the range of 15 to 60 minutes, both the time and the temperature cannot be simultaneously at their upper extremity i.e. when the time is 60 minutes, the temperature cannot be 120°C. In fact, it has been observed that in a preferred embodiment of the invention, a multiplication value of the temperature and the time (i.e. temperature * time) is in the range of 1500 to 6900.

Now referring to Figure 3, there is illustrated a block diagram of a system (200) for preparation of khoa in accordance with the embodiment of the invention. The system (200) comprises a heating device (202) for heating concentrated milk having solids in the range of 40 to 55% to a temperature in the range of 90 to 120°C to obtain hot concentrated milk. The system further comprises a holding device (204) being in operational interconnection with the heating device (202). The holding device (204) is adapted to receive the concentrated milk from the heating device (202). The holding device (204) is further adapted to hold the concentrated milk at a temperature in the range of 90 to 120°C for a time period in the range of 15 to 60 minutes to obtain hot denatured milk.

The system (200) further comprises a Scraped Surface Heat Exchanger (206) being in operational interconnection with the holding device (204). The Scraped Surface Heat Exchanger (206) is adapted to receive the hot denatured milk from the holding device (204). The Scraped Surface Heat Exchanger (206) is further adapted to produce a solid mass from the hot denatured milk.

The system (200) further comprises steam removal equipment (208) being in operational interconnection with the Scraped Surface Heat Exchanger (206). The steam removal equipment (208) is adapted to receive the solid mass thus formed in the Scraped Surface Heat Exchanger (206). The steam removal equipment (208) is further adapted to remove steam from the solid mass to obtain khoa.

The system (200) may further comprise an evaporator (210). The evaporator (210) is adapted to receive milk having solids in the range of 10 to 15 % and concentrates the same to obtain concentrated milk having solids in the range of 40 to 55%. In an embodiment of the invention, the evaporator (210) is operably connected to an inlet port of the heating device (202). In an embodiment of the invention, the evaporator (210) is a single-effect evaporator or a multi-effect evaporator.

Also, in an embodiment of the invention, the system (200) further comprises a cooling device (212) and a molding device (214).

In an embodiment of the invention, the heating device (202) is selected from a group comprising of plate heat exchanger, shell and tube heat exchanger, etc.

In an embodiment of the invention, the holding device (204) comprises at least one holding tube. In an embodiment of the invention, the at least one holding tube is provided with insulation. In an embodiment of the invention, the Scraped Surface Heat Exchanger (206) is selected from a group comprising a horizontal Scraped Surface Heat Exchanger, an inclined Scraped Surface Heat Exchanger, and a vertical Scraped Surface Heat Exchanger. In a preferred embodiment of the invention, the Scraped Surface Heat Exchanger (206) is a vertical Scraped Surface Heat Exchanger.

In an embodiment of the invention, the vertical Scraped Surface Heat Exchanger includes inlet port located at about a bottom end of the vertical Scraped Surface Heat Exchanger for receiving the hot denatured milk and an outlet port located at about a top end of the vertical Scraped Surface Heat Exchanger for removing the solid mass formed therein.

In an embodiment of the invention, the steam removal equipment (208) is selected from a group comprising flash vessel, condenser and vacuum system.

Reference is drawn to the following example to illustrate the working of the invention.

Example 1:

10 kg of buffalo milk having about 10 to 15% solids is fed to an evaporator. While the evaporator is of a single effect type evaporator, multi effect type evaporator can also be used in its place. Steam is used as heating medium in the single effect type evaporator. The single effect type evaporator is maintained at a temperature below 70°C to obtain 3 kg of concentrated milk having about 50% solids. The concentrated milk having about 50% solids is heated in a heat exchanger to obtain 3 kg of hot concentrated milk having a temperature in the range of 90 to 120°C. Steam is used in the heat exchanger as the heating medium. The hot concentrated milk having a temperature of about 90 to 120°C is held for 15 to 60 minutes in holding tubes to obtain denatured hot milk. The multiplication value of the temperature and the time (i.e. temperature * time) was maintained in the range of 6000 to 6500. The denatured hot milk is then fed to an inlet port located at a bottom of a vertical Scraped Surface Heat Exchanger. The vertical Scraped Surface Heat Exchanger receives steam as the heating medium and produces solid mass. The vertical Scraped Surface Heat Exchanger is maintained at a temperature of about 90 to 120°C. The solid mass is withdrawn from an outlet port located at about a top end of the vertical Scraped Surface Heat Exchanger. The solid mass is fed to a flash vessel which is maintained at a pressure less than atmospheric pressure. In the flash vessel, the solid mass looses moisture and produces 2.30 kg of khoa. The khoa thus produced is then cooled. The characteristic of the khoa thus obtained is tabulated in Table 1.

Table 1: Properties of Khoa

Example 2:

10 kg of buffalo milk having about 10 to 15% solids is fed to an evaporator. While the evaporator is of a single effect type evaporator, multi effect type evaporator can also be used in its place. Steam is used as heating medium in the single effect type evaporator. The single effect type evaporator is maintained at a temperature below 70°C to obtain 3 kg of concentrated milk having about 50% solids. The concentrated milk having about 50% solids is heated in a heat exchanger to obtain 3 kg of hot concentrated milk having a temperature in the range of 90 to 120°C. Steam is used in the heat exchanger as the heating medium. The hot concentrated milk having a temperature of about 90 to 120°C is held for 15 to 60 minutes in holding tubes to obtain denatured hot milk. The multiplication value of the temperature and the time (i.e. temperature * time) was maintained in the range of 5000 to 5500. The denatured hot milk is then fed to an inlet port located at a bottom of a vertical Scraped Surface Heat Exchanger. The vertical Scraped Surface Heat Exchanger receives steam as the heating medium and produces solid mass. The vertical Scraped Surface Heat Exchanger is maintained at a temperature of about 90 to 120°C. The solid mass is withdrawn from an outlet port located at about a top end of the vertical Scraped Surface Heat Exchanger. The solid mass is fed to a flash vessel which is maintained at a pressure less than atmospheric pressure. In the flash vessel, the solid mass looses moisture and produces 2.25 kg of khoa. The khoa thus produced is then cooled. The characteristic of the khoa thus obtained is tabulated in Table 1. Table 2: Properties of Khoa

Example 3:

10 kg of buffalo milk having about 10 to 15% solids is fed to an evaporator. While the evaporator is of a single effect type evaporator, multi effect type evaporator can also be used in its place. Steam is used as heating medium in the single effect type evaporator. The single effect type evaporator is maintained at a temperature below 70°C to obtain 3 kg of concentrated milk having about 50% solids. The concentrated milk having about 50% solids is heated in a heat exchanger to obtain 3 kg of hot concentrated milk having a temperature in the range of 90 to 120°C. Steam is used in the heat exchanger as the heating medium. The hot concentrated milk having a temperature of about 90 to 120°C is held for 15 to 60 minutes in holding tubes to obtain denatured hot milk. The multiplication value of the temperature and the time (i.e. temperature * time) was maintained in the range of 4000 to 4500. The denatured hot milk is then fed to an inlet port located at a bottom of a vertical Scraped Surface Heat Exchanger. The vertical Scraped Surface Heat Exchanger receives steam as the heating medium and produces solid mass. The vertical Scraped Surface Heat Exchanger is maintained at a temperature of about 90 to 120°C. The solid mass is withdrawn from an outlet port located at about a top end of the vertical Scraped Surface Heat Exchanger. The solid mass is fed to a flash vessel which is maintained at a pressure less than atmospheric pressure. In the flash vessel, the solid mass looses moisture and produces 2.20 kg of khoa. The khoa thus produced is then cooled. The characteristic of the khoa thus obtained is tabulated in Table 3.

Table 3: Properties of Khoa

Example 4:

10 kg of buffalo milk having about 10 to 15% solids is fed to an evaporator. While the evaporator is of a single effect type evaporator, multi effect type evaporator can also be used in its place. Steam is used as heating medium in the single effect type evaporator. The single effect type evaporator is maintained at a temperature below 70°C to obtain 3 kg of concentrated milk having about 50% solids. The concentrated milk having about 50% solids is heated in a heat exchanger to obtain 3 kg of hot concentrated milk having a temperature in the range of 90 to 120°C. Steam is used in the heat exchanger as the heating medium. The hot concentrated milk having a temperature of about 90 to 120°C is held for 15 to 60 minutes in holding tubes to obtain denatured hot milk. The multiplication value of the temperature and the time (i.e. temperature * time) was maintained in the range of 3000 to 3500. The denatured hot milk is then fed to an inlet port located at a bottom of a vertical Scraped Surface Heat Exchanger. The vertical Scraped Surface Heat Exchanger receives steam as the heating medium and produces solid mass. The vertical Scraped Surface Heat Exchanger is maintained at a temperature of about 90 to 120°C. The solid mass is withdrawn from an outlet port located at about a top end of the vertical Scraped Surface Heat Exchanger. The solid mass is fed to a flash vessel which is maintained at a pressure less than atmospheric pressure. In the flash vessel, the solid mass looses moisture and produces 2.17 kg of khoa. The khoa thus produced is then cooled. The characteristic of the khoa thus obtained is tabulated in Table 4.

Table 4: Properties of Khoa

Example 5:

10 kg of buffalo milk having about 10 to 15% solids is fed to an evaporator. While the evaporator is of a single effect type evaporator, multi effect type evaporator can also be used in its place. Steam is used as heating medium in the single effect type evaporator. The single effect type evaporator is maintained at a temperature below 70°C to obtain 3 kg of concentrated milk having about 50% solids. The concentrated milk having about 50% solids is heated in a heat exchanger to obtain 3 kg of hot concentrated milk having a temperature in the range of 90 to 120°C. Steam is used in the heat exchanger as the heating medium. The hot concentrated milk having a temperature of about 90 to 120°C is held for 15 to 60 minutes in holding tubes to obtain denatured hot milk. The multiplication value of the temperature and the time (i.e. temperature * time) was maintained in the range of 1750 to 2250. The denatured hot milk is then fed to an inlet port located at a bottom of a vertical Scraped Surface Heat Exchanger. The vertical Scraped Surface Heat Exchanger receives steam as the heating medium and produces solid mass. The vertical Scraped Surface Heat Exchanger is maintained at a temperature of about 90 to 120°C. The solid mass is withdrawn from an outlet port located at about a top end of the vertical Scraped Surface Heat Exchanger. The solid mass is fed to a flash vessel which is maintained at a pressure less than atmospheric pressure. In the flash vessel, the solid mass looses moisture and produces 2.14 kg of khoa. The khoa thus produced is then cooled. The characteristic of the khoa thus obtained is tabulated in Table 5.

Table 5: Properties of Khoa

Example 6:

10 kg of buffalo milk having about 10 to 15% solids is fed to an evaporator. While the evaporator is of a single effect type evaporator, multi effect type evaporator can also be used in its place. Steam is used as heating medium in the single effect type evaporator. The single effect type evaporator is maintained at a temperature below 70°C to obtain 3 kg of concentrated milk having about 50% solids. The concentrated milk having about 50% solids is heated in a heat exchanger to obtain 3 kg of hot concentrated milk having a temperature in the range of 90 to 120°C. Steam is used in the heat exchanger as the heating medium. The hot concentrated milk having a temperature of about 90 to 120°C is held for 15 to 60 minutes in holding tubes to obtain denatured hot milk. The multiplication value of the temperature and the time (i.e. temperature * time) was maintained in the range of 7100 to 7400. The denatured hot milk is then fed to an inlet port located at a bottom of a vertical Scraped Surface Heat Exchanger. The vertical Scraped Surface Heat Exchanger receives steam as the heating medium and produces solid mass. The vertical Scraped Surface Heat Exchanger is maintained at a temperature of about 90 to 120°C. The solid mass is withdrawn from an outlet port located at about a top end of the vertical Scraped Surface Heat Exchanger. The solid mass is fed to a flash vessel which is maintained at a pressure less than atmospheric pressure. In the flash vessel, the solid mass looses moisture and produces 1.94 kg of khoa. The khoa thus produced is then cooled. The characteristic of the khoa thus obtained is tabulated in Table 6.

Table 6: Properties of Khoa

Example 7:

10 kg of buffalo milk having about 10 to 15% solids is fed to an evaporator. While the evaporator is of a single effect type evaporator, multi effect type evaporator can also be used in its place. Steam is used as heating medium in the single effect type evaporator. The single effect type evaporator is maintained at a temperature below 70°C to obtain 3 kg of concentrated milk having about 50% solids. The concentrated milk having about 50% solids is heated in a heat exchanger to obtain 3 kg of hot concentrated milk having a temperature in the range of 90 to 120°C. Steam is used in the heat exchanger as the heating medium. The hot concentrated milk having a temperature of about 90 to 120°C is held for 15 to 60 minutes in holding tubes to obtain denatured hot milk. The multiplication value of the temperature and the time (i.e. temperature * time) was maintained in the range of 1300 to 1500. The denatured hot milk is then fed to an inlet port located at a bottom of a vertical Scraped Surface Heat Exchanger. The vertical Scraped Surface Heat Exchanger receives steam as the heating medium and produces solid mass. The vertical Scraped Surface Heat Exchanger is maintained at a temperature of about 90 to 120°C. The solid mass is withdrawn from an outlet port located at about a top end of the vertical Scraped Surface Heat Exchanger. The solid mass is fed to a flash vessel which is maintained at a pressure less than atmospheric pressure. In the flash vessel, the solid mass looses moisture and produces 1.98 kg of khoa. The khoa thus produced is then cooled. The characteristic of the khoa thus obtained is tabulated in Table 7.

Table 7: Properties of Khoa

It has been observed that heat treatment given to the milk in the traditional kadai based method of making khoa is far more intensive than the heat treatment given to the milk in the previously known mechanised processes. Hence, the previously known mechanised processes failed to produce khoa whose texture is same like that of traditional kadai based method. The heat treatment is characterized by holding temperature and holding time and governs solid content concentration and degree of protein denaturation.

As can be seen from the above examples, more is the solid content in the khoa, less is the production of khoa and also less is the grainy texture of the khoa thus produced. It is clear from examples that the texture of khoa does not depend on the total solid contents alone and there are some elements like concentration, temperature, holding time and most importantly the degree of protein denaturation.

It was observed that more the holding time of concentrated milk at elevated temperature, more is the protein denaturation. Also, more the holding temperature more is the protein denaturation. However, with both extremes of holding time and temperature, the khoa produced becomes spongy in nature and does not have approved flavour and colour.

The present invention uses conditions such as higher heat treatment at higher concentration level and desired holding time to denature the milk proteins to the extent that the system produces khoa of the same texture and firmness continuously from the present mechanized system.

While certain present preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereto. Clearly, the invention may be otherwise variously embodied, and practiced within the scope of the following claims.

Claims

CLAIM:

1. A process for preparation of khoa, said process comprising: heating concentrated milk having solids in the range of 40 to 55% to a temperature in the range of 90 to 120°C to obtain hot concentrated milk; holding the concentrated milk at a temperature in the range of 90 to 120°C for a time period in the range of 15 to 60 minutes to obtain hot denatured milk; passing the hot denatured milk through a Scraped Surface Heat Exchanger to obtain solid mass; and removing steam from the solid mass to obtain khoa.

2. The process as claimed in claim 1, wherein the concentrated milk having solid in the range of 40 to 55% is obtained from raw milk having solids content in the range of 4 to 8%.

3. The process as claimed in claim 2, wherein raw milk having solid in the range of 10 to 15 % is subjected to a step of concentrating (110) to obtain concentrated milk having solids content in the range of 40 to 55%.

4. The process as claimed in claim 1, wherein the solid mass thus obtained contains entrapped steam.

5. The process as claimed in claim 4, wherein the steam entrapped in the solid mass is removed by subjecting the solid mass to a pressure less than atmospheric pressure.

6. The process as claimed in claim 1, wherein both the time and the temperature cannot be simultaneously at their lower extremity and both the time and the temperature cannot be simultaneously at their upper extremity.

7. The process as claimed in claim 1, wherein a multiplication value of the temperature and the time (i.e. temperature * time) is in the range of 1500 to 6900.

8. A system (200) for preparation of khoa, said system comprising: a heating device (202) for heating concentrated milk having solids in the range of 40 to 55% to a temperature in the range of 90 to 120°C to obtain hot concentrated milk; a holding device (204) being in operational interconnection with the heating device (202), the holding device (204) being adapted to hold the concentrated milk at a temperature in the range of 90 to 120°C for a time period in the range of 15 to 60 minutes to obtain hot denatured milk; a Scraped Surface Heat Exchanger (206) being in operational interconnection with the holding device (204), the Scraped Surface Heat Exchanger (206) being adapted to produce a solid mass from the hot denatured milk; and a steam removal equipment (208) being in operational interconnection with the Scraped Surface Heat Exchanger (206), the steam removal equipment (208) being adapted to remove steam from the solid mass to obtain khoa. The system as claimed in claim 8, comprising an evaporator (210) adapted to receive milk having solids content in the range of 10 to 15 % and concentrating the same to obtain concentrated milk having solids content in the range of 40 to 55%. The system as claimed in claim 9, wherein the evaporator (210) is a single-effect evaporator or a multi-effect evaporator. The system as claimed in claim 8, comprising a molding device (212) and cooling device (214). The system as claimed in claim 8, wherein the heating device (202) is selected from a group comprising of plate heat exchanger, and shell and tube type heat exchanger. The system as claimed in claim 8, wherein the holding device (204) comprises at least one holding tube which is insulated and cladded. The system as claimed in claim 8, wherein the Scraped Surface Heat Exchanger (206) is selected from a group comprising a horizontal Scraped Surface Heat Exchanger, an inclined Scraped Surface Heat Exchanger, and a vertical Scraped Surface Heat Exchanger. The system as claimed in claim 14, wherein the Scraped Surface Heat Exchanger (206) is a vertical Scraped Surface Heat Exchanger. The system as claimed in claim 15, wherein the vertical Scraped Surface Heat Exchanger includes inlet port located at about a bottom end of the vertical Scraped Surface Heat Exchanger for receiving the hot denatured milk and an outlet port located at about a top end of the vertical Scraped Surface Heat Exchanger for removing the solid mass formed therein. The system as claimed in claim 8, wherein the steam removal equipment (208) is selected from a group comprising flash vessel, condenser and vacuum system.