| Abstract
| - Rice color changes from white to amber during parboiling (soaking and steaming). Color parametersindicated that, during soaking, yellow bran pigments leached out in the water. The levels of the Maillardprecursors (i.e., reducing sugars (RS) and free α-amino nitrogen (FAN)) depended on soakingtemperature and time: leaching of RS was compensated by enzymic formation for long soakingtimes (>60 min), while proteolytic activity was too low to compensate for FAN leaching. Rice soakingunder nitrogen, oxygen, or ambient conditions and determination of polyphenol oxidase activity allowedus to conclude that the effect of enzymic color changes on the soaked rice color was rather small.Color measurements of brown and milled mildly, intermediately, and severely parboiled rice samplesshowed that both brown and milled rice samples were darker and more red and yellow after parboilingand that the effect depended on the severity of parboiling conditions. Furthermore, steaming affectedthe rice color more and in a way opposite to that observed in soaking. The changes in RS and theloss of FAN during parboiling suggested that Maillard type reactions occur during brown rice steaming.Analyses of furosine levels confirmed Maillard browning of outer bran layers and endosperm duringsteaming. The level of this Maillard indicator increased with the severity of parboiling conditions inboth brown and milled parboiled rice. Measurements of the levels of bran pigments indicated thatbran pigments diffuse into the endosperm during parboiling and contribute to the parboiled rice color. Keywords: Rice; parboiling; color; Maillard reaction; furosine; pigment
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