Usha Thiyam-Holländer

Value-added potential of expeller-pressed canola oil refining: characterization of sinapic acid derivatives and tocopherols from byproducts.

Valuable phenolic antioxidants are lost during oil refining, but evaluation of their occurrence in refining byproducts is lacking. Rapeseed and canola oil are both rich sources of sinapic acid derivatives and tocopherols. The retention and loss of sinapic acid derivatives and tocopherols in commercially produced expeller-pressed canola oils subjected to various refining steps and the respective byproducts were investigated. Loss of canolol (3) and tocopherols were observed during bleaching (84.9%) and deodorization (37.6%), respectively. Sinapic acid (2) (42.9 μg/g), sinapine (1) (199 μg/g), and canolol (344 μg/g) were found in the refining byproducts, namely, soap stock, spent bleaching clay, and wash water, for the first time. Tocopherols (3.75 mg/g) and other nonidentified phenolic compounds (2.7 mg sinapic acid equivalent/g) were found in deodistillates, a byproduct of deodorization. DPPH radical scavenging confirmed the antioxidant potential of the byproducts. This study confirms the value-added potential of byproducts of refining as sources of endogenous phenolics.

Effect of Conventional and Microwave Toasting on Sinapic Acid Derivatives and Canolol Content of Canola

Canola seeds were subjected to conventional and microwave heat treatments to investigate changes in the phenolic profile of defatted meal and oil obtained from the toasted seeds. Different temperature (120–200 °C) and time (5–20 min) combinations were applied for toasting the seeds in a conventional oven. The seeds were also toasted using a microwave oven at 300 Watt power level with and without steaming. Phenolics were extracted from the defatted meal and oil of raw and toasted seeds. The main phenolic compounds namely sinapine (SP), sinapoyl glucose (SG), sinapic acid (SA) and canolol were identified and quantified by HPLC-DAD. Total phenolics and SA derivatives in the meal were found to decrease in both toasting treatments. Canolol was formed in the oil and subsequently increased with increasing toasting temperature up to 200 °C. The optimum toasting conditions under which the canolol content of the oil showed the highest increment rate (more than 2200 folds) were found to be 200 °C for 15 min in the conventional oven. However, the optimum microwave toasting conditions were 20 min with steam which increased canolol content by more than 1700 folds.

Endogenous Phenolics in Hulls and Cotyledons of Mustard and Canola: A Comparative Study on Its Sinapates and Antioxidant Capacity

Endogenous sinapic acid (SA), sinapine (SP), sinapoyl glucose (SG) and canolol (CAN) of canola and mustard seeds are the potent antioxidants in various lipid-containing systems. The study investigated these phenolic antioxidants using different fractions of canola and mustard seeds. Phenolic compounds were extracted from whole seeds and their fractions: hulls and cotyledons, using 70% methanol by the ultrasonication method and quantified using HPLC-DAD. The major phenolics from both hulls and cotyledons extracts were SP, with small amounts of SG, and SA with a significant difference of phenolic contents between the two seed fractions. Cotyledons showed relatively high content of SP, SA, SG and total phenolics in comparison to hulls (p < 0.001). The concentration of SP in different fractions ranged from 1.15 ± 0.07 to 12.20 ± 1.16 mg/g and followed a decreasing trend- canola cotyledons > mustard cotyledons > mustard seeds > canola seeds > mustard hulls > canola hulls. UPLC-tandem Mass Spectrometry confirmed the presence of sinapates and its fragmentation in these extracts. Further, a high degree of correlation (r = 0.93) was noted between DPPH scavenging activity and total phenolic content.