Optimization of Residual Hexane in Edible Oils Analysis Using Static Headspace Gas Chromatography

This study aims to determine the residual hexane in four edible oils in Malaysia using a simple, rapid, and automated method in order to improve the efficiency and productivity of the analysis. Gas chromatography (GC/FID) equipped with a headspace autosampler (HS-20) was used to perform the analysis. Incubation time for each injection was successfully optimized from one hour to 30 minutes (50% reduction) compared to the official AOCS method Ca 3b-87. Out of the four tested edible oils, only the hexane residues detected in sunflower oil exceeded the maximum residue limit (MRL) set by the European Union regulation. Significant difference of the results obtained between large calibration range (0–938 mg kg−1) and small calibration range (0–68 mg kg−1) suggests that there is a need to use a lower standard calibration concentration to avoid misinterpretation of analysis results. Method validation applies to the technical hexane; 2-methylpentane, 3-methylpentane, cyclohexane, and methylcyclopentane, the signal-to-noise (S/N), as well as the limit of quantification (LoQ) values was found to be 218.20, 221.45, 746.37, 97.37 and 0.85, 0.84, 0.25, 1.93 mg kg−1, respectively. Good linearity, repeatability, and low carryover of this method have provided an alternative way to analyze the content of the residual hexane in edible oils in a more efficient manner. Current study might provide a fundamental reference for the improvement of the AOCS official Ca 3b-87 method for determination of hexane residues in fats and oils analysis in the future.

Microbial Fermentation Extraction Processing of Protein from Soybean

Although hexane extraction of soybean oil has the high recovery，residual hexane in oil is noxious for consumer health. Crew pressing and extruding-expelling extraction processes denature protein to render functional properties poor for food and meal use. This processing employed microbial fermentation to extract protein from full fat soy flour so that denaturation degree of protein reduced. The results showed that low temperature flaking and extrusing soy flakes was beneficial to improving protein extraction, after optimizing the fermentation conditions with the Response Surface Methodology (RSM), total protein extraction yield achieved the highest value - 86.66% at optimal fermentation conditions - 6.6% extruded full fat soy flour, 5.4% inoculation volume, the initial pH8.1. These advances make the microbial fermentation extraction process of protein from soybeans attractive channel as the environmentally – friendly technology.