FAT RICH DAIRY PRODUCTS

Module 11. Ghee and butteroil

Lesson 35
METHODS OF GHEE PREPARATION

35.1 Introduction

Ghee production is the largest segment of milk utilization in India. Most of the dairy plants have ghee production facility to meet the demand of the market as well as to utilize the excess fat in profitable manner. Since simple technology involved in ghee production and relatively less investment for ghee production unit as already plant have steam boiler with them. Method of production varies from small scale to large scale. Cost reduction on energy consumption for production of unit quantity of ghee is the recent trend and equipments are designed to meet the requirement. Following are the various processes available in the industry to make ghee including Desi method which is following largely at rural household level.

35.2 Methods of Preparation

The principle involved in ghee preparation include;

1. concentration of milk fat in the form of cream or butter.

2. Heat clarification of fat rich milk portion and thus reducing the amount of water to less than 0.5%.

3. Removal of the curd content in the form of ghee residue.

There are five methods of ghee making:

i. Desi or Indigenous Method

ii. Direct Cream Method

iii. Creamery Butter Method

iv. Prestratification Method

v. Continuous Method

35.3 Desi Method

This was the practice from age-old days in rural areas where excessive milk will be cultured and kept for overnight for fermentation. Resultant curd was churned using hand driven wooden beaters to separate the milk fat in the form of desi butter. Some follow slightly different method wherein milk is heated continuously to about 80°C, the malai (creamy layer) that forms over the surface was collected manually. This malai is then churned to get the desi butter. After collection of desi butter over a period of time, this butter is melted in a metal pan or earthenware vessel on an open fire. Extent of frothing is an index to judge when to terminate heating. Heating should be stop when sudden foaming appears and leave the contents undisturbed after heating. Curd particles starts settling down over a period of time and decant the clear fat carefully. In this method it is possible to achieve only 75 – 85% fat recovery.

35.4 Direct Cream Method

This method involves separation of cream of 60 to 70% fat from milk by centrifugation process, fresh cream or cultured cream is heated to 114±2°C in a stainless steel, jacketed ghee kettle. This kettle is fitted with an agitator, steam control valve, pressure and temperature gauges. A movable hollow stainless tube centrally bored for emptying out the contents or alternatively provision can be made for tilting device on the ghee kettle to decant the product. Heating is discontinued as soon as the colour of the ghee residue turns to golden yellow or light brown. Usually, first plenty of effervescence accompanied by a crackling sound in the preliminary stages of boiling but both gradually subsides when the moisture content decreases. When almost all the moisture is evaporated, the temperature of the liquid medium suddenly spurts up and care has to be exercised at this stage to control the heating. The end point is indicated by the appearance of second effervescence, which is subtler than the first one accompanied by the browning of curd particles. At this stage the typical ghee flavour emanates and this indicates that the final stage in the preparation of ghee.

Advantages of this method are

1. No need for butter production prior to manufacturing of ghee.

Limitations

1. Long heating time to remove the moisture.

2. High content of serum solids in the cream may also produce a highly caramelized flavour in the ghee.

3. 4 – 6% loss of butter fat in the ghee residue & during the handling operations.

4. So, 70 – 80% fat cream is recommended to minimize both fat loss and steam consumption

35.5 Creamery Butter Method

This is the standard method adopted in most of the organized dairies. Unsalted or white butter is used as raw material. Butter mass or butter blocks are melted at 60°C to 80°C in butter melter. Molten butter is pumped into the ghee boiler where final heating will be done using steam as heating medium. Increase the steam pressure to raise the temperature. Scum which is forming on the top of the surface of the product is removed from time to time with the help of perforated ladle. Moment of disappearance of effervescence, appearance of finer air bubbles on the surface of the fat and browning of the curd particles indicates to stop heating. At this stage typical ghee aroma is produced. Final heating temperature is adjusted to about 114±2°C. To get the cooked flavour, heating beyond this temperature is also being in practice. Ghee is filtered via oil filter into the settling tank.

35.6 Pre-Stratification Method

Butter is produced from aged cream of 38 to 40% fat using continuous butter making machine or batch churn. Butter is then transferred to butter melter, and melt at 80°C. This molten butter is kept undisturbed in a ghee kettle or boiler at a temperature of 80-85°C for 30 min. Here, in ghee kettle, stratification of mass takes place, product stratifies into 3 distinct layers. Denatured protein particles (curd particles) and impurities are collected on top layer and floats on surface. Middle layer consists of clear fat and bottom layer consists of buttermilk serum carrying 80% of moisture and 70% of solods-not-fat contained in butter.

The bottom layer is then carefully removed without disturbing the both top and middle layers. Middle layer, largely consists of fat is heated to 114±2°C along with top layer of floating curd particles and denatured protein. This step is necessary to develop characteristic ghee aroma. Milder flavour ghee can be produced, since most of the curd content is removed before final clarification temperature of ghee.

35.6.1 Advantages of pre-stratification method

* Removal of buttermilk (bottom layer) eliminates prolonged heating for evaporation of the moisture

* Formation of significantly low quantity ghee residue

* Low quantity of ghee absorbed into ghee residue so less fat loss along with ghee residue

* Production of ghee with lower FFA and acidity

35.7 Continuous Method

This method was developed to meet the requirement of high volume production and to overcome the limitation of batch method. Limitations of batch method are as follows:

* Requires high energy, due to low heat transfer co-efficient

* Cleaning and sanitation of equipments, not satisfactory

* Equipments and process unsuitable for large volume of production

* Floor becomes slippery due to ghee spillage

* Handling losses are more

So, continuous method was invented and has following benefits;

* Better control on quality of the product

* Only small hold-up of raw material in the plant at any time and hence no chance for whole batch getting spoiled

* Contamination by handlers can be eliminated

* CIP can be possible

* No foaming of the product during production

Butter is heated in a butter melter to molten state and then transfer into balance tank, and pumped further to scraped surface heat exchanger(SSHE), followed by flashing in vapour separator. And this heating in SSHE and flashing are repeated in next two stages to reduce the moisture level. Ghee is then pass through centrifugal clarifier where residue will be removed. Clarified ghee is stored for filling and packing.

35.8 Granulation and Cooling of Ghee

Granulation is important criterion of quality; higher temperature of clarification gives better grain size due to high phospholipids content.

35.8.1 Phenomenon

Completely melted ghee on cooling to prevailing Indian temperatures, can assume the form of large, coarse grains suspended discretely or in clusters in a liquid phase. The process of crystallization is initiated with the formation suitable nuclei. Rate of cooling strongly influences the rate nucleus formation. Stirring or agitation and seeding (at the rate of 1 – 3%) encourage the nucleus formation. For better granulation, ghee should be slowly cooled to 28°C in 2-3 hours time and agitation is required during granulation to form smaller granules.

35.8.2 Causes of granulation

The partly granular form assumed by ghee is primarily due to certain content of glycerides of higher melting saturated fatty acids, especially palmitic & stearic. Thus buffalo milk ghee show predominant granulation than cow milk ghee.

35.9 Yield

The yield of ghee from cream or butter is influenced by fat content of raw material. Factors which influence the yield are listed below.

35.9.1 Factors influencing yield

Following factors influence the yield of ghee,

1. Method of production: The fat recovery in indigenous method is lowest in range of 80-85% in creamery butter method it ranges from 88-92% and highest in direct cream method ranging from 90-95%.

2. The fat content of the raw material used: Higher the fat content higher will be the yield and vice versa.

3. Quality of milk or cream: If the acidity of milk or cream intended to use in ghee production is higher then fat losses in ghee residue will be higher , thus it reduces the yield.

4. Fat recovery from ghee residue: Scientific reports suggest to extract as much as fat from ghee residue by dissolving ghee residue in hot water followed by filtration and centrifugation. By this method, it is possible to extract the fat from ghee residue and that fat can be added back to cream or butter melter.

35.10 Use of Substandard Milk for Ghee Production

India is a tropical country, where in ambient temperatures touches the mark of 40°C in summer. Collection system for raw milk in rural area is still carried out at ambient temperature. Especially in summer while collecting the milk cans from ton-of places causes acidity of milk to increase and results in souring of milk. This milk cannot be useful for making market milk or for thermal process.

Therefore, there is a need to utilize, this milk for products preparation. Where in it does not affect such the quality of end product. So, in commercial dairy plants such milk is diverted and collected separately based on platform tests (COB, sensory etc…). This sourced milk is collected in balance tank and circulated using high sped pump. This causes the breakdown of far globule membrane and release the fat. After a circulation of 30 min milk is kept undisturbed. This facilitates the separation of cream base or gravity. Then this cream is used for ghee production directly or collected over-a-period of time and neutralized to produce butter from this cream. This butter will be used for ghee making.

35.10.1 Quality of ghee made from substandard milk

Ghee manufactured from neutralized milk or cream may differ from that prepared from fresh milk. Major differences reported are as follows.

Table 35.1 Quality difference between fresh milk ghee and acid milk ghee