Ghee is a fat rich dairy product of Indian origin and its western equivalent is butteroil. When ghee is stored under ambient temperature, it undergoes oxidative deterioration. The oxidation of unsaturated fatty acids produces hydroperoxides and their subsequent breakdown products viz. aldehydes, ketones, low molecular weight acids and oxy acids. These components are responsible for the development of off flavours in ghee.
The Food Adulteration rules as amended in 1976 permit the addition of 0.02% by weight of butylated hydroxy anisole (BHA) and butylated hydroxy toluene (BHT) either singly or in combination in to the ghee. The problem is the continuous use of these antioxidants result in teratogenic or carcinogenic effect in small animals and primates.
In ancient days, it was a common practice in India to add betel leaves and curry leaves to the butter during the clarification process of ghee making. But it is now recognized that these substances indeed possess antioxidant properties, which will not only improve the shelf life and taste of the product but also they are safe to the consumers.
A scientific research was carried out to study the antioxidant property of betel and curry leaves at different concentration when they are boiled during the clarification process of ghee making. The findings show that the initial peroxide value of ghee (0.00) showed no increase up to 30 days of storage at 30°C. But the control samples showed a steep increase in peroxide value after 60 days of storage. Ghee samples treated with 1% curry leaves were found to be the most resistant up to 135 days. The betel leaves at 1% concentration appeared to be most acceptable and stable even after 147 days of storage at 30°C.
The degree of hydrolysis of ghee during the storage is measured by titration for free fatty acid (oleic acid). After a month storage, there is a progressive increase in free fatty acid content. The control sample of ghee (not treated with any anti oxidant) showed a 100 percent increase in free fatty acid content (after 30 days) where as the betel leaves treated ghee (at 1% level) offered maximum protection to the ghee from hydrolysis.
It is observed that the plant leaves (curry and betel leaves) contain phenolic compounds such as hydroxychavicol, eugenol, and certain amino acids such as aspargine, glycine, serine, aspartic acid, glutamic acid, threonine, alanine, proline, and tryptophan which might possess antioxidant properties and help to improve the shelf life of ghee.
A slight reduction in the iodine value from 35.9 in control to 35.6 in treated ghee samples is observed when the samples are stored at 30°C for 147 days. Ghee samples treated with chemical antioxidants showed similar results. Ghee samples produced with curry and betel leaves showed a lowered butyrorefractometer (BR) reading. The compounds that go in to solution during the clarification process might be responsible for the lowered BR reading.
To conclude, the betel and curry leaves can serve as a potent antioxidant at 1% concentration without any adverse effect on the organoleptic properties of the ghee and help replace the BHA and BHT to extend the shelf life of ghee.
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The author is a dairy expert, specializing in the technology and microbiology of dairy foods and holds a doctoral degree in Dairy Science; for more info on milk and dairy products please visit her site A Professional Dairy Site