BY-PRODUCTS TECHNOLOGY

Module 7. Ghee-residue

Lesson 46
GHEE-RESIDUE: PROCESSING AND UTILIZATION

46.1 Introduction

Ghee-residue is a nutritious by-product. This by-product has been studied for its physico-chemical characteristics and its utilization in a number of food products like chocolate burfi, samosa filling, chapatis etc. Ghee-residue, by virtue of its chemical composition, bulk of production, physical characteristics, long shelf life permitting its collection and centralized handling, has great potential and is more amenable to exploit its utilization in food industry. Further, the flavour potential of ghee-residue is much greater than that of ghee. Hence it can be utilised for flavouring bland fats and also enhancing their keeping quality.

46.2 Recovery of Ghee from Ghee-Residue

In dairy plants, attempt is made to recover as much ghee as possible from ghee-residue. Two methods of recovery of ghee from ghee-residue are adopted.

46.2.1 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 is simple, efficient, more practical, economical and requires no electricity or sophisticated equipment.

46.2.2 Centrifugation process

This consists of heating ghee-residue in water (65°C) due to which fat entrapped within the residue matrix melts and oozes out, and collects as the top layer above soak water. Ghee is subsequently recovered by centrifuging the water-fat phase. The method yields 25% ghee (46% efficiency). The process is shown in Fig. 46.1.

Alternatively the released fat at the surface of water is recovered by solidification by cooling either by adding ice/cold water or leaving it in a cold store (5-10°C) over night.

46.3 Treatment and Processing of Ghee-Residue

Ghee-residue has soft and smooth body, 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 it becomes 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, lumps are broken and then pulverized by passing through 40 mesh sieve. A number of processing treatments are possible for ghee-residue (Table 46.1). All the treatments make the processed residue soft and smooth. It was reported that the changes brought about in the constituents of the residue remained same. Residues absorb considerable amount of moisture, its acidity reduces; in case of treatments II, IV and VI acidity reduced to nil. Fat and lactose contents of the residue also reduced considerably. Washing of residue with 50% alcohol followed by cooking in baking soda, i.e., treatment IV was reported to be the best as far as removal of excess fat from the residue was concerned. Autoclaving of this residue after incorporating 2% vinegar lowered the moisture content and improved the texture of the product. Keeping quality of all types of GR clarified at 120°C is 3 months. Its shelf life can be further extended to more than 4 months by pressing it in cake form.

Table 46.1 Comparison of chemical composition of ghee-residue subjected to various processing treatments

Treatment I Loosely tying 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.

Sripad et al, (1996) reported that addition of ethanol extracts of browning compounds (1%) from defatted GR to cow and buffalo ghee clarified at 100°C and stored at 37°C extended the shelf life by about 1.5 and 2 months respectively.

46.4 Applications of Ghee-Residue

46.4.1 Preparation of confections

The physico-chemical properties of processed GR make it 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 enzymatic activity and flavour deterioration in the final product. The higher fat content in the residue quite often obviate the need for addition of oils and fats in its preparation.

46.4.1.1 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 (Fig. 46.2). 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.

46.4.1.2 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 (Fig. 46.3). 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.

46.4.2 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 (Fig. 46.4). An edible paste for 'dosa' and 'samosa' can be prepared if 2-4% chutney powder is used instead of marmite. Both these preparations, if properly packaged, can remain marketable for 2 months.

46.4.3 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 (Fig. 46.5), 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 two-third of the mixture, which has already been spread-out as a thick layer on a well-greased tray. The mass is cooled and when set, cut into pieces of uniform size and shape.

46.4.4 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.

46.4.5 Broiler/animal feeds

Ghee-residue because of its nutritional value is used as broiler feeds up to 20% in broilers diet. It can also be served as feed to animals with combination with other feeds.

Selected references

Borawake, K.N. and Bhosale, D.N. 1996. Utilization of ghee residue in preparation of nankatai type cookies and sponge cakes. Indian J. Dairy Sci., 49 (2): 114-119.
Gupta, P.R. 2007. Milk utilization pattern. In: Dairy India-sixth edition, edited by P.R. Gupta and Sharad Gupta, Dairy India Yearbook, New Delhi: 33.
Sripad, S., Kempanna, C. and Bhat, G.S. 1996. Effect of alcohol extract of deffated ghee-residue on the shelf life of ghee. Indian J. Dairy Biosci. 7: 82-84.