Ghee is a high-fat dairy product of Indian origin and its Western equivalent is butter oil. When ghee is stored at room temperature, it undergoes oxidative deterioration. The oxidation of unsaturated fatty acids produces hydroperoxides and their subsequent decomposition products, viz. aldehydes, ketones, low molecular weight acids and oxyacids. These components are responsible for the development of off-flavors in ghee.
The Food Adulteration Rules amended in 1976 allowed the addition of 0.02% by weight of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) either alone or in combination in ghee. The problem is that the continuous use of these antioxidants results in teratogenic or carcinogenic effects in small animals and primates.
In ancient times, it was common practice in India to add betel leaves and curry leaves to butter during the clarification process of making ghee. But these substances are now recognized to possess antioxidant properties, which will not only improve the shelf life and taste of the product, but are also safe for consumers.
A scientific investigation was carried out to study the antioxidant property of betel and curry leaves at different concentrations when boiled during the clarification process of ghee making. The findings show that the initial peroxide value of ghee (0.00) did not show any increase up to 30 days of storage at 30°C. But control samples showed a strong increase in peroxide value after 60 days of storage. Ghee samples treated with 1% curry leaves were found to be the most resistant for up to 135 days. Betel leaves at 1% concentration seemed to be the most acceptable and stable even after 147 days of storage at 30°C.
The degree of hydrolysis of ghee during storage is measured by titration of free fatty acids (oleic acid). After one month of storage, there is a gradual increase in the content of free fatty acids. The control ghee sample (not treated with any antioxidant) showed a 100% increase in free fatty acid content (after 30 days), while the ghee-treated betel leaves (at the 1% level) offered maximum protection to ghee against hydrolysis.
Plant leaves (curry and betel leaves) are noted to 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 that may possess antioxidant properties. and help improve the shelf life of ghee.
A slight reduction in iodine value from 35.9 in the control to 35.6 in the 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 lower butyrorefractometer (BR) reading. Compounds that dissolve during the clarification process may be responsible for the reduced BR reading.
To conclude, betel and curry leaves can serve as a powerful antioxidant at 1% concentration without any adverse effect on the organoleptic properties of ghee and help replace BHA and BHT to extend the shelf life of ghee.
For more information on ghee and the different manufacturing methods, visit GHEE MANUFACTURING
The author is a dairy expert, specializing in dairy food technology and microbiology and has a Ph.D. in Dairy Sciences; for more information on milk and dairy products visit his site A Professional Dairy Site