Development of process protocol to enhance the phospholipid content of ghee residue

Many by-products of the dairy industry contain nutritive and commercial value, which with appropriate technological interventions can be exploited for improving the profitability of the industry. Ghee residue (GR) is one such by-product reported to contain considerable amount of polar lipids dominated by phospholipids (PLs). An attempt was made to develop a stepwise protocol to enhance the PL content in ghee residue, to facilitate its efficient and economical extraction from the residue matrix. As a first step, remnant ghee (about 13%) in the residue was expelled by pressing the ghee residue matrix at 5kg/cm2 for 5 min. This was followed by treating the ghee residue with two solvents, namely n-hexane and water. Treatment with n-hexane at solvent to solid ratio of 1:4, 1:3 and 1:2, for a contact time of 30 min, resulted in a PL content 26.22, 24.68 and 21.29%(on lipid basis), respectively, in the ghee residue samples. Steeping of the ghee residue in hot water (boiled to 100oC) at a solid to water ratio of 1:4 for 60 min resulted in retention of 27.03%lipids in the residue, corresponding to a removal of 16.93% fat with the solvent stream. This resulted in an appreciable enrichment of phospholipids in the ghee residue matrix to the tune of 30.56% on lipid basis; corresponding to the initial PL content of 8.26%. Increase of surface area of the solid matrix through size comminution was also explored to enhance the efficacy of solvent treatment. When the ghee residue was ground to a particle size of 0.25 mm and 0.30 mm and then subjected to hot water treatment, its PL content was found to increase to9.56% and 9.32% (ghee residue basis), respectively. Thus, the physical and chemical interventions significantly improved the phospholipid content of ghee residue.