yuzu peel marmalade

Yuzu-peel marmalade is recorded as a food in which several constituents potentially related to bitterness change at the same time during processing. In a single process-stage analysis reported in 1994, soaking yuzu peel in water and then heating it was reported to reduce naringin (one citrus constituent associated with bitterness) by 63–76% while increasing nomilin (another citrus constituent associated with bitterness) from 5.4 to 15.8ppm. These possible contributors to bitterness did not move in the same direction. Moreover, naringin itself in this sample was described as below the concentration at which bitterness is perceived, so its decrease alone cannot explain any change in the marmalade's bitterness.

In the same 1994 study, constituent analysis was paired with a sensory evaluation by 13 people of marmalades made from yuzu, konatsu, kumquat, and navel orange, separately or in combinations. Across the samples, rated bitterness intensity corresponded broadly with the amount of nomilin present. However, the test was small and limited to one set of conditions, and aroma, acidity, and sweetness can also affect perceived bitterness; nomilin alone cannot account conclusively for marmalade bitterness.

Perceived bitterness may also vary with the processing method itself. A 2014 study had 27 students and staff compare yuzu marmalade made by high-pressure processing with the same formulation made by conventional heating, rating 14 attributes on a 5-point scale. The high-pressure marmalade received a lower bitterness rating than the heated one, while liking of its bitterness, mouthfeel, and overall rating were higher. However, details such as blinding were not sufficiently described, and several properties changed together in the comparison, so the result cannot be isolated as an effect of high-pressure processing alone.