Studies were undertaken to examine the effect of heat treatment on total phenolic content (TPC), colour
value (yellowishness and brightness), polyphenol oxidase (PPO) activity and curcuminoid of fresh turmeric
rhizome. Fresh turmeric rhizomes were subjected to heat treatment at different temperatures (60–100 C) for
different durations (10–60 min), causing a reduction in browning which was evident from the improved
yellowishness and brightness. Activity of PPO was also decreased during heat treatment and PPO was almost
inactivated when heated at 80 C for 30 min. TPC of heat-treated turmeric after drying (powder) is
significantly higher than that after the fresh process. TPC values increased gradually when samples were
heated from 60 to 80 C. At 90 and 100 C, TPC values were almost identical. Maximum brightness and
yellowishness were obtained when the turmeric was heated above 80 C. Quantitation of curcuminoids in the
turmeric sample was made with high performance thin layer chromatography (HPTLC). There was no
significant change in the concentration of curcuminoids among the heat-treated samples. But in the sun-dried
samples, a significant reduction in curcuminoid concentration was observed.