Effect of Ohmic Heating Pre-treatment on Millable Oil Extraction and Physicochemical Properties of Mustard (Brassica juncea) Oil

Author: Rajendra Hamad, Subir Kumar Chakraborty, Ajesh Kumar V. and Adinath Kate

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Abstract

The pre-treatment of seeds plays a crucial role in enhancing oil extraction efficiency. Present study aimed to evaluate the effect of ohmic heating pre-treatment on the extraction of millable oil and physicochemical properties of the oil extracted from mustard seeds. The oil yield, peroxide value, acid value, free fatty acid (FFA) content, colour, refractive index, density and viscosity of the extracted oil were evaluated under varying electric field strengths (EFS) and exposure times. The results showed that ohmic heating pre-treatment significantly increased the oil yield compared to the untreated sample, with the highest recovery achieved at an EFS of 24.5 V/cm and an exposure time of 600 s. However, higher EFS levels and longer exposure times led to undesirable effects on the oil quality, as indicated by increased peroxide value, acid value and FFA content. The colour of the oil varied with EFS and exposure time, showing a decrease with higher EFS and an increase with longer exposure times. The refractive index, density, and viscosity of the oil remained relatively unchanged. These findings suggest the potential of ohmic heating as a pre-treatment strategy for enhancing oil extraction efficiency from mustard seeds, with minimal changes in terms of oil quality.

Keywords

Ohmic heating, mustard seeds, oil extraction, physicochemical properties

Conclusion

This study investigated the effect of ohmic heating pre-treatment on the extraction of millable oil from mustard seeds and the physicochemical properties of extracted oil. The oil yield was significantly improved compared to the untreated sample, with the highest oil recovery (33.18%) obtained at an electric field strength (EFS) of 24.5 V/cm and an exposure time of 600 s. This increase in oil recovery can be attributed to the breakdown of cell membranes and the promotion of oil release through electroporation and thermal softening. However, the increase in EFS and longer exposure times during ohmic heating led to undesirable effects on the quality of the extracted oil. The peroxide value, which indicates the presence of hydroperoxides and primary oxidation components, increased significantly with higher EFS levels and exposure times. This suggests that higher EFS levels promote oxidation reactions and the formation of peroxides in the oil. Similarly, the acid value and free fatty acid (FFA) content of the oil increased with increased EFS and exposure time, indicating hydrolysis of triglycerides into free fatty acids. Regarding the colour of the extracted oil, an increase in EFS led to a significant decrease in colour value, while longer exposure times resulted in an increase. The refractive index, density, and viscosity of the oil were not significantly affected by the ohmic heating pre-treatment. Overall, ohmic heating pre-treatment improved the oil recovery from mustard seeds, but it also had some detrimental effects on the quality of the extracted oil, as indicated by increased peroxide value, acid value, FFA content, and variable colour changes.

References

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How to cite this article

Rajendra Hamad, Subir Kumar Chakraborty, Ajesh Kumar V. and Adinath Kate (2023). Effect of ohmic heating pre-treatment on millable oil extraction and physicochemical properties of mustard (Brassica juncea) oil. Biological Forum – An International Journal, 15(7): 151-156.