| The high amount of fat peroxide will affect the flavor of food, go to oxidation, the peroxide will break into low-lever aldehydes, ketones, carboxylic acids, and esters, have a special pungent odor of hazardous chemicals. The peroxide value of lipid is an important indicator of oil quality, is the important standard to determine the freshness and quality grade grease, which reflects the extent of oxidative rancidity of fats.In this study, an iron thiocyanate spectrophotometric method was chosen, uses to determine the peroxide value of oil samples, and determines the peroxide content. The topics selected solution phase spectrophotometry, organic microporous membrane adsorption color, activated silica gel adsorption color and resin phase spectrophotometry to determine the peroxide value of lipid. The optimal conditions of solution determination: Mixed the sample solution and0.05mL ferrous chloride solution (3.5g/L), use chloroform+methanol (7+3) to10mL, and then add0.05mL potassium thiocyanate solution (300g/L), stand for5min, measured at500nm. The optimal conditions for organic microporous membrane adsorption color:the sample solution and0.05mL ferrous chloride solution (3.5g/L) reaction, and membrane adsorption the generated Fe3+, by adding150g/L potassium thiocyanate solution0.10mL color. The optimal conditions of activated silica gel adsorption color:200mg activated silica gel for solid phase carrier, add the sample solution and0.2mL ferrous chloride solution (3.5g/L) reaction, and then add0.1mL potassium thiocyanate solution (300g/L),160r/min shaking for10min. The optimal conditions of resin phase:150mg macroporous resin D4020; add the sample solution and0.2mL ferrous chloride solution (3.5g/L) reaction, and then add0.1mL potassium thiocyanate solution (300g/L), reaction for10min, and the absorbance measured at490nm and800nm. Several solid-color determination of peroxide value in oil samples by solid phase adsorption enrichment, to determine the range of peroxide value in samples with low content of lipid peroxide.Using several methods to determinate the actual sample, and compared with the standard Iodometric titration method. Experimental results show that the iron thiocyanate method has good accuracy, and the peroxide value of Iodometric titration method within the three solid-phases adsorption results. That shows three kinds of solid-phase carrier (organic microporous membrane, activated silica gel, macroporous resin) adsorption enrichment color to determine the scope of the peroxide value of samples are accurate. |
