EFFECT OF ANTIOXIDANT PRINCIPLES ISOLATED FROM SORGHUM (Sorghum bicolor, Linn.) GRAINS ON OXIDATIVE STABILITY OF GHEE
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Date
1997
Authors
KAUR, RIPUDAMAN
Journal Title
Journal ISSN
Volume Title
Publisher
AAU, Anand
Abstract
A study was carried out to elucidate the effect of addition of sorghum grains (SG) or its pre-extract on the oxidative stability of ghee. A composite sample of sorghum grains powder (SGP) prepared from grains of sorghum contained 9.85 per cent moisture, 9.60 per cent protein, 3.40 per cent lipids, 1.75 per cent ash and 75.40 per cent carbohydrates as the major constituents and 5.5 per cent phenolics, 270.0 mg per cent phospholipids and 0.68 per cent flavanols. Ghee used in the study was procured from Vidya Dairy. To such ghee samples SGP was added either by addition-extraction or by pre-extraction-addition method. In the former method SGP was added directly to ghee at 0, 1.0, 1.5, 2.0, and 2.5 per cent levels and after heating to 120°C, the mixtures were filtered at 60°C. In the latter method, a mixture of SGP plus ghee (1:1, w/w) was heated to 120°C and the fihered material obtained (pre-extract) was added to ghee at 0, 4, 6, 8 and 10 per cent (v/v) levels. For comparison, the last treatment was addition of BHA at a level of 0.02 per cent. To monitor the effectiveness of additives, peroxide value of ghee samples was determined immediately after preparation and after every 48 h interval of storage at 80° + 2°C in an oven. The average phospholipids content of ghee samples under additionextraction method varied fi-om 4.98 to 15.68 mg/lOOg of ghee, the order being : 15.68 mg/lOOg (2.5 per cent SGP) > 14.89 mg/lOOg (2.0 per cent SGP) > 12.41 mg/lOOg (1.5 per cent SGP) > 9.01 mg/lOOg (1.0 per cent SGP) > 5.63 mg/lOOg (0.02 per cent BHA) > 4.98 mg/lOOg (control). The water extractable phenolics content varied on an average from 0.28 to 13.87 mg/lOOg of ghee and were found to be in the sequence: 13.87 mg/lOOg (2.5 per cent SGP) > 1 l.i5 mg/lOOg (2.0 per cent SGP) > 9.12 mg/lOOg (1.5 per cent SGP) > 5.34 mg/lOOg (1.0 per cent SGP) > 0.30 mg/lOOg (control) > 0.28 mg /lOOg (0.02 per cent BHA). In the pre-extraction-addition method, the average phospholipids content in ghee samples under different treatments varied from 4.98 to 30.00 mg/lOOg, the order being : 30.00 mg/lOOg (10 per cent pre-extract) > 27.37 mg per 100 g (8 per cent pre-extract) > 21.46 mg/lOOg (6 per cent pre-extract) > 15.97 mg/lOOg (4 per cent pre-extract) > 5.63 mg/IOOg (0.02 per cent BHA) > 4.98 mg/lOOg (control). The water extractable phenolics content varied on an average from 0.28 to 16.66 mg/lOOg of ghee and were found to be in the sequence : 16,66 mg/lOOg (10 per cent preextract) > 14.61 mg/lOOg (8 per cent pre-extract) > 10.44 mg/lOOg (6 per cent preextract) > 0.30 mg/lOOg (control) >0.28 mg/lOOg (0.02 per cent BHA). From the results of this study it is concluded that : Addition of sorghum grains either by addition-extraction or by pre-extraction-addition method enhances the stability of ghee against autoxidation. Addition of sorghurh grains at the rate of 1.5 per cent or above in direct addition and 4 per cent (v/v) pre-extract in indirect addition has been found to be more effective than addition of 0.02 per cent BHA in ghee. The main antioxidant principles appear to be the various types of phospholipids and the phenolic compounds of sorghum grains. The other possible agents could be the sterols, vitamin C, carotene and the interaction products of carbohydrates and proteins generated during the heating process.
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Keywords
DAIRY CHEMISTRY, A STUDY