Effect of heating on the quality of clarified butter, called ghee, in Ayurveda

Abstract

　Clarified butter (CB) is often used in cooking and is called ghee in Ayurveda, a traditional medicine practiced in India. It is prepared by heating butter, a process which can cause oxidation and decomposition of fat-soluble vitamins, thus altering the nutritional content. In this novel report, we prepared various CBs with different heating or reheating methods and evaluated their quality by measuring their retinol, α-tocopherol (α-Toc), parameters of oxidative deterioration, milkfat content, and water content. There was little effect on retinol, α-Toc, and peroxide values among samples heated for 0, 15, and 30 min after the oil became transparent, but the color turned brown in a time-dependent manner. In the CB that was reheated for 15, 30 min at 140℃, the color faded, retinol and α-Toc contents decreased, and peroxide value increased depending on time. These fluctuations were inferred to be associated with the production of melanoidin, an antioxidant caused by the Maillard reaction. This experiment revealed the following two points regarding heating and quality: (1) Preparation at <30 min after the oil became transparent hardly affects the CB quality. (2) In the CB that was deproteinized before color change, reheating is the cause of quality degradation, which occurs even at 140℃. These results suggest that temperature control and heating in the presence of protein are important for producing higher quality and stable CB. This study is important as it guarantees the nutritional function of CB and provides research on quality stabilization in preparing ghee as an alternative medicine.