Comparing Oil Color And Oxidative Stability Among Mustard Genotypes Under Nitrogen Fertilization

Effect of N fertilization (N-80) on oil color was investigated in 24 genotypes of Indian mustard (Brassica juncea). Most of the genotypes were found to have oil color coordinates of L* 72 to 78, while a* and b* color coordinates did not vary. Genotypes with a shift in L* coordinates from 78 to 72 under N-80 had lower beta-carotene content, which decreased from 11.3% (IC212031) to 68% (Maya). Among the two classes of pheophytins, pheophytin a was dominant under N-80. Chlorophyll a was absent in almost all oil samples. In N-80, the rate of degradation of chlorophyll a into its product pheophytin a was greater over that of the control (N-0) as evident from the negative correlation of chlorophyll a and pheophytin a (r = -0.54). Peroxide value (PV) was negatively correlated to all pigments under N-0. In the case of acid value (AV), under N-0, the stability of oil seems to be more contributed by beta-carotene, whereas under N-80, the oxidative stability of oil indicated by AV and PV appears to be contributed more by pheophytins. There was also improvement in oil stability index (OSI) under N-80 as compared to N-0 application. It is inferred that N fertilization does influence the oil pigmentation and its stability which is important for good quality oil.