Semi-industrial Countercurrent Extraction of Soybean with 2-Methyloxolane for High-Quality Protein and Oil

Abstract

This study investigates the extraction of soybean oil with 2-methyloxolane (2-MeOx) in a semi-industrial continuous multistage countercurrent extractor (Model IV Crown Iron Extractor). 2-MeOx is a biobased solvent that was added to the list of permitted solvents for food production in Europe in January 2023. 2-MeOx was able to extract an oil fraction that was inaccessible to hexane. This led to a lower residual oil content in the meal extracted with 2-MeOx (0.48 vs 1.94 g oil/100 g meal for hexane). Compared with hexane, 2-MeOx yielded an oil richer in phenolic compounds (3229.7 vs 145.5 mg GAE/kg oil), with higher oxidative stability (>70 vs 17.8 h) and improved unsaponifiable matter (0.63 vs 0.43% w/w). In addition, there was a higher protein dispersibility index (PDI) (55.35 vs 40.84%) and higher protein solubility in KOH solution (94.14 vs 84.79%) observed with 2-MeOx compared to hexane-extracted meal. Furthermore, 2-MeOx (1% water) could provide a meal with a PDI even higher than that of the raw material. These aspects can lead to a considerable economic advantage that could compensate for the higher energy consumption of the 2-MeOx distillation process compared to hexane. However, extraction with 2-MeOx resulted in a higher peroxide value in the oil (12.53 vs 2.65 meq/kg fat) and a higher solvent retention index in the meal (0.424 vs 0.285 g solvent/g meal). The influence of some key extraction parameters (temperature, L/S ratio, solvent water content) on the process efficiency and product quality was investigated. This study confirms the great potential of 2-MeOx in the extraction of oilseeds and suggests optimized extraction conditions for high-quality products and efficient industrial production process.