BkMUC-Tur
Turmeric 鬱金 (ukon): A yellow dye obtained from the root of the Curcuma longa (or C. domestica) plant native to India. The primary color component in turmeric is curcumin. Turmeric produces a bright deep yellow that has a high tinting strength. Turmeric made its way from Ryūkyū (Okinawa) and Siam (Thailand) through trade.
Turmeric and orpiment have been the most commonly detected yellows as a single colorant or as a mixture of the two. In addition to mixtures with orpiment, turmeric was frequently overprinted or mixed with dayflower and safflower to create green and orange.
For additional information see: Turmeric, Turmeric (Curcuma longa) LC, Uemura Dye Archive: Turmeric 20, Curcuma longa (Kew)
Examples of Turmeric in Ukiyo-e Prints
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Analysis
Excitation Emission Matrix (EEM) spectroscopy can easily identify turmeric due to its high fluorescence and clear, consistent pattern. Another yellow colorant thought to have been traditionally used, Japanese yellow wood or kihada (黄檗) also fluoresces very brightly but produces a very different EEM pattern, making it easy to distinguish between the two materials. Yellow wood has not been detected so far.
3D EEM plot for Turmeric 
3D EEM plots for Yellow references
Images of Turmeric
Curcuma Longa
Curcuma Longa, by National Tropical Botanical Garden
Turmeric rhizomes
Cut turmeric rhizomes
Ground turmeric
Paper dyed with turmeric
Turmeric, by National Museum of American History
Turmeric processing (video), by Foodtechwaale
List of Prints
Below is a list of prints where turmeric was detected.