Comparing Oil Color and Oxidative Stability among Mustard Genotypes under Nitrogen Fertilization

Abstract

Core Ideas The oxidative stability index (OSI) which is the ratio of monounsaturated fatty acid/polyunsaturated fatty acid was slightly improved under N‐fertilization (N80). It is worthy to mention this is the first report on Brassica juncea studying the effect of fertilizer application on oil quality and a comparison among genotypes. Under the control (N0), the oxidative stability of oil was contributed by β‐carotene and at N80 application it was contributed by pheophytins. The change in the contents level of pigments and the rate of transformation of chlorophyll a to pheophytin a is was high compared to chlorophyll b to pheophytin b under N80. The oil with a shift in L*coordinate from 78 to 72 at N80 application showed a reduction in β‐carotene and an increase in pheophytin a. Effect of N fertilization (N80) 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 N80 had lower β‐carotene content, which decreased from 11.3% (IC212031) to 68% (Maya). Among the two classes of pheophytins, pheophytin a was dominant under N80. Chlorophyll a was absent in almost all oil samples. In N80, the rate of degradation of chlorophyll a into its product pheophytin a was greater over that of the control (N0) 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 N0. In the case of acid value (AV), under N0, the stability of oil seems to be more contributed by β‐carotene, whereas under N80, 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 N80 as compared to N0 application. It is inferred that N fertilization does influence the oil pigmentation and its stability which is important for good quality oil.