Ghee Residue

Ghee residue is a by-product of ghee manufacturing industry and is produced in large quantity (about 91000 tonnes per annum) in India. During the manufacture of ghee, the solids not fat (SNF) present in cream or butter appears in the form of small particles known as ghee-residue. It is obtained after molten ghee has been either strained out with bag filters or muslin cloth or separated by continuous centrifugal clarifiers. The yield of ghee-residue varies with the method of preparation of ghee.

This is due to the variation in the non-fatty serum constituents of the different raw materials used for the preparation of ghee. The average yield of ghee-residue is maximum in direct creamery (DC) method (12%) followed by about 3.7% yield in creamery butter (CB) and desi butter (DB) method. Keeping quality of all types of GR clarified at 120°C is 3 months. Its shelf life can further be increased to more than 4 months by pressing it in cake form.

Physical attributes: Ghee residue is moist brownish sediment. On average, particle diameter of ghee residue is about 115 ì and density is 1.14 g/cm3.

i. Chemical Composition

A look at the chemical composition and yield of GR obtained from various sources(Table) will give an idea of the huge quantity of nutrients in terms of fat, protein,lactose and minerals that go in ghee-residue. There are considerable variations in the chemical composition of ghee-residue depending upon the method of preparation of ghee. The approximate composition (%) of ghee-residue varies as fat (32-70), protein (12-39), moisture (8-30), lactose (2-14) and ash (1-8). Moisture, protein and ash contents are more in CB and DB ghee-residue than in DC ghee-residues.Fat content is higher in DC residues than in butter ghee-residue. Lactose content is the highest in DB followed by DC and CB ghee-residues. Thus ghee residue is a rich source of lipids, proteins and carbohydrates.

Chemical composition and yield of ghee-residue (Hand pressed)

Lipids in ghee-residue

i) Analytical constants: The lipids of ghee-residue have lower Reichert value and polenske value (24.4., 1.3) but higher iodine value (43.4) in comparison to those of corresponding ghee (30.1, 1.6, 33.9 respectively.

ii) Fatty acid composition: The lipids of ghee-residue have lesser lower chain fatty acids C4.0 to C12.0 (5.3%) and total saturated fatty acids (58.7%) and more of unsaturated fatty acids (41.3%) in comparison to those of ghee (10.1, 66.8, 33.2% respectively). The fatty acid composition of phospholipids shows that it has no fatty acids lower than 12 carbon atoms.

iii) Polyunsaturated fatty acids (PUFA): Irrespective of the method of preparation, PUFA content of ghee-residue lipids (4.4%) is higher than those of corresponding ghee (2.8%).

iv) Phospholipids: Ghee-residue is rich in phospholipids (1-9%). The phospholipid content of ghee-residue is dependent upon the method of preparation. It is highest in CB ghee-residue lipids (17.39%) followed by DB ghee residue lipids (4.95%) and the least in DC ghee residue lipids (1.57%). These levels are much higher than those in ghee (0.004 - 0.08%). Phospholipid acts synergistically with reducing substances in ghee residue and protects it from oxidative defect. Higher phospholipid (a good emulsifier) content of ghee residue is beneficial in developing certain products where emulsification of fat and aqueous phase is desired.

The phospholipid content of ghee residue decreases as the period of heating increases due to the transfer of phospholipids from ghee-residue to ghee. While heating cream butter, only a small fraction of the phospholipids get transferred to ghee, most of the phospholipids remain with the residue because of their polar character. The differences observed in the physico-chemical constant, fatty acids and PUFA contents between lipids of ghee-residue and ghee are due to the high phospholipid content of  ghee-residue.

Proteins in ghee-residue: Soluble nitrogen content of ghee-residue prepared from cream or creamery butter decreases with heating time. This decrease is due to the denaturation of the proteins. The total reducing capacity expressed as mg of cysteine hydrochloride/g of CB-ghee-residue (26.0) and free sulphydryl content (μm/g) of ghee-residue (2.90) are much higher than those in ghee (0.075 and 0.02, respectively).These substances are liberated from protein during heat treatment and because of their polar nature are mostly retained in the ghee-residue. Whey proteins, especially ß-lactoglobulin are the main source for these sulphydryl compounds

Milk sugars in ghee-residue: Main sugars in ghee-residue prepared at 120oC are lactose, galactose and glucose. As the period of heating is increased, the lactose content of ghee-residue decreases with a corresponding increase in galactose and glucose content.

ii. Nutritional Properties

Ghee residue is a rich source of protein and fat apart from containing considerable amounts of minerals and can be used as human dietary supplement. However the nutritional value of ghee-residue protein is low due to the damage of some essential amino acids during preparation of ghee at high temperature. The lack of lysine in ghee-residue is the most dominant factor in depressing the PER of ghee-residue.The supplementation of ghee-residue with a combination of lysine (8%), methionine (2.5%) and tryptophane (1.4%) increases its nutritional value even slightly higher than that of SMP. It has been observed that skim milk powder (SMP), SMP: gheeresidue (2:1), SMP: ghee-residue (1:2) and ghee-residue diets have protein efficiency ration (PER) of 3.44, 3.07, 2.46 and 0.66, respectively.

Antioxidant Properties: Ghee-residue is a rich source of natural antioxidants and its antioxidant properties are due to its constituents affected by various technological parameters. The overall antioxidant properties are due to both lipid and non-lipid constituents. Ghee residue can be used as a source of natural antioxidants for improving the shelf life of food products including dairy products where use of synthetic antioxidants is generally not preferred because of their toxic effects.

i) Contribution of lipid constituents: Phospholipids show the maximum antioxidant activity followed by á-tocopherol and vitamin A. Among the various phospholipid fractions, cephalin shows the greatest antioxidant activity. The oxidative stability of ghee can be increased by increasing its phospholipid content to 0.1% either through heat treatment or through solvent extraction process. It has been observed that heating ghee-residue with ghee in the ratio of 1:4 at 130°C have maximum transfer of phospholipids from ghee-residue to ghee.These antioxidant concentrates can be added to ghee to give about 0.1% phospholipids so as to increase the keeping quality of ghee.

ii) Contribution of non-lipid constituents: Among the non-lipid constituents, the amino acid proline, lysine, cysteine hydrochloride and tryplophane show the antioxidant properties. The contribution of proline as antioxidant is maximum, though less than BHA at 0.02% level. Further, the addition of lactose, glucose, galactose and their interaction products with protein and phospholipids to ghee also increase the oxidative stability of ghee. As ghee-residues contain large amount of reducing substances including free sulphydryls, such compounds may also contribute to the antioxidant properties of ghee-residue.

iii) Antioxidant Properties as Affected by the Temperature of Clarification:

The antioxidant efficiency of ghee-residue decreases with increase in the temperature of clearification of ghee. The addition of ghee-residue obtained from ghee prepared at lower temperature (110°C) results in lesser development of peroxides than the addition of ghee-residue prepared at higher temperature (150°C).

iv) Antioxidant Properties as Affected by the Method of Preparation: CB ghee-residue has the maximum antioxidant properties followed by DB and DC ghee residues.

Flavouring Properties: Ghee residue is also a rich and natural source of flavor compounds viz. FFA, carbonyls and lactones. The level of FFA, carbonyls and lactones in ghee-residue are respectively 11, 10 and 132 times than in ghee. Ghee flavour can be induced in vanaspati and butter oil etc. by adding 10% ghee-residue and clarification at 120°C/flash (10%). This treatment also enhances their keeping quality because of the antioxidant property of ghee residue.

 

Chemical composition and yield of ghee-residue (Hand pressed)

 iii. Utilization of Ghee-Residue

Ghee residue, by virtue of its chemical composition, nutritional quality, physical characteristics, bulk of production and long shelf life permitting its collection and centralized handling has great potential and is more amenable to exploit its utilization.Ghee residue can be utilised in a number of products like chocolate burfi, samosa filling, chapatis etc. However, most dairy plants in India have not been utilising ghee residue profitably except for fat extraction. Commercial utilisation of whole ghee residue is yet to pick up. Most of the ghee residue goes to waste. A sincere R & D work and a strong willingness on the part of manufacturer is required to develop food uses of ghee residue and put it in the market

Recovery of Ghee

In dairy plants, attempt has been made to recover as much ghee as possible from ghee residue. Two methods of recovery of ghee from ghee-residue have been developed.

i) Pressure technique: This consists of subjecting the heated ghee-residue (65- 70°C) to a limited pressure in hand screw or hydraulic press. This method gives a yield of about 45% (extraction efficiency of about 67%). This method has been recommended for adoption as it is simple, efficient, more practical, economical and requires no electricity or sophisticated equipment.

ii) Centrifugal process: This consists of heating ghee residue in water (65°C) so as to transfer the occluded ghee of the residue to water. Ghee is subsequently recovered by centrifuging the water-fat phase. The method yields 25% ghee (46% efficiency).

Processing of Ghee Residue

Ghee residue has soft and smooth texture but gets progressively hardened during storage. The change in the textural characteristics is much faster particularly during the first 15 days and by the end of a month its grain becomes very hard and gritty. In order to eliminate the undesirable characteristics, it is necessary to process it so as to yield a soft and smooth texture essential for edible preparations. Before subjecting the residue to any-treatment, its lumps are broken and then pulverized by passing through 40-mesh sieve. A number of treatments of ghee residue (Table ) have been suggested. All the treatments make the processed residue soft and smooth.The trend of changes brought about in the constituents of residue remains same. Residues absorb considerable amount of moisture and its acidity reduces. In case of treatments II, IV and VI acidity reduces to nil. Fat and lactose contents of the residue also reduce considerably. Washing of residue with 50% alcohol followed by cooking in soda, i.e., treatment IV is best so far as removal of excess fat from the residue is concerned. Autoclaving of this residue after incorporating 2% vinegar lowers the moisture content and improves the texture of the product.

Preparation of confections

The physico-chemical properties of processed ghee-residue are very suitable for preparation of confections. It contains the major constituents in suitable proportion and possesses fine texture that imparts requisite body to such products. Further the treatment during processing of these confections involves heating to such an extent that it completely arrests enzyme activity and flavour deterioration in the final product.The higher fat content in the residue quite often obviates the need for addition of oils and fats in its preparation

i) Preparation of candy: The recipe for candy preparation consists of 1 kg processed ghee-residue, 500 to 625 g sugar and 125 to 250 g dry coconut powder. 50% sugar syrup is prepared and processed ghee residue is thoroughly mixed in it with the help of suitable ladle. The mixture is heated on low fire with continuous stirring to evaporate moisture. When the mass becomes sufficiently sticky, coconut powder is added. The candy is evenly spread on a plate and cooled (5-10°C) for about an hour and cut into small cubes and wrapped in parchment paper.

ii) Preparation of chocolate: The recipe for preparation of chocolate consists of 1 kg processed ghee residue, 500 to 625 g sugar, 60 to 90 g cocoa powder and 250 g skim milk powder. 50% sugar syrup is prepared and processed ghee residue is thoroughly mixed in it with the help of suitable ladle. The contents are desiccated on a low flame till dough is formed. At this stage cocoa and skim milk powder are added and stirred vigorously till pat is formed. Finished product is spread on a plate and cooled overnight in refrigerator and cut into slabs or cubes and wrapped in parchment paper. The product has a shelf life of more than 3 months.

 

                                                        Comparision of chemical composition of ghee-residue

subjected to various processing treatments.

 Treatment I : Loosely tieing the residue in the form of bundle and cooking in boiling water for 30 min.

Treatment II : Cooking the residue in boiling 1.0% sodium bicarbonate for 30 min.

Treatment III : Washing the residue with 50% alcohol and then cooking in boiling water for 30 min.

Treatment IV : Washing the residue with 50% alcohol followed by boiling in 1% sodium bicarbonate.

Treatment V : Autoclaving the residue (15 PSI/10 min) obtained from III after incorporating 2% vinegar

Treatment VI : Autoclaving the residue obtained from IV after incorporating 2% vinegar.

Preparation of edible pastes: For preparation of edible paste for sandwich, processed ghee-residue is first mixed with 2.5-3% salt and then 0.1-0.5% marmite (a yeast product). The whole mass is heated on a low fire for about 5 min till a paste is formed. An edible paste for ‘dosa’ and ‘samosa’ can be prepared if 2-4% chatni powder is used instead of marmite. Both these preparations, if properly packaged, can remain marketable for 2 months.

Preparation of burfi-type sweet: Processed ghee residue is mixed with khoa in the proportion of 1:1, on total solids basis. Sugar is added @75% of the total solids (khoa + ghee residue). The whole mass is heated and worked rigorously for 10-15 minutes so as to dissolve the added sugar completely. At this stage about one-third of the sweetened mass is separated and 8% chocolate powder, on total solids basis, is added to processed ghee residue and khoa and thoroughly mixed. This portion containing the dissolved chocolate is applied as a thin layer over the remaining twothird of the mixture, which has already been spread-out as a thick layer on a wellgreased tray. The mass is cooled and when set, cut into pieces of uniform size and shape.

Preparation of bakery products: Nankatai type cookies and sponge cake can be prepared from processed ghee-residue obtained from ripened cream. 30 and 20% part of vanaspati fat used in preparation of cookies and sponge cake, respectively is replaced by ghee-residue fat. Use of ghee-residue enriches both the bakery products in protein content.