Study of Kinetic Model for the Adsorption of β-carotene on Activated Bleaching Earth in the Bleaching of Cambodian Soybean Oil

Author(s): Monyneath Bunthan, Laysreng Pov, Sela Kong, Manit Say, Yukleav Nat, Chin Ping Tan, Reasmey Tan.

Soybean oil is a popular vegetable oil that can be obtained using mechanical or chemical extraction methods. Among these approaches, the hydraulic press is a popular mechanical extraction method that has benefits such as minimal starting cost, no solvent usage, and a high level of operating safety. When the soybean oil has been extracted, it is typically sent to a refinery for further processing which includes degumming, neutralization, bleaching, and deodorization. However, during the bleaching process, there is a lack of comprehensive understanding and a specific kinetic model for the adsorption of β-carotene, a prominent colorant, on activated bleaching earth in soybean oil obtained from a hydraulic press. This research aims to investigate the effect of three parameters, including adsorbent dosage, temperature, and contact time on the bleaching efficiency of soybean oil bleaching. Moreover, three different kinetics models such as pseudofirst order, pseudo-second order, and intraparticle diffusion model for adsorption of β-carotene on activated bleaching earth were studied. According to the result, the physicochemical properties such as acid value, peroxide value, iodine value, and p-anisidine value of soybean oil met the standards set by the Codex Alimentarius standard, indicating its goodness for further processing. Additionally, the color of the soybean oil appeared dark-yellowish. The optimum bleaching process parameters applied were 10 wt.% absorbent dosage to oil, 110°C for temperature, and 60 mins for contact time. The adsorption kinetics of β-carotene of the bleaching process was best fit with the pseudo-second order with R2 values of 0.9903. To sum up, the study contributes to the understanding of β-carotene adsorption behavior in crude soybean oil bleaching using a hydraulic press. Moreover, the kinetic model helps optimize the process, predict adsorption capacity and rate constants, and design cost-effective, safe bleaching strategies for refined soybean oil with reduced colorants.