Research Of Interesterification Technique Catalyzed By KOH/Glycerol

Interesterification technique catalyzed by chemical catalyst was studied in this thesisusing lard as a model fat. The research mainly involved preparation and characterization ofcatalyst, optimization of interesterification parameters, effect of material qualities oninteresterification process, purification and analysis of interesterified production.New catalyst was prepared using KOH and glycerol. A high catalytic ability ofKOH/Glycerol was found due to its large surface area which was analyzed by SEM. It wasobserved that KOH/Glycerol was water-tolerant(10%), fatty acid-tolerant(2.05mgKOH/g) andhydroperoxide-tolerant(peroxide value7.11mmol/kg). Also the qualities of KOH/Glycerol,including catalytic ability, color, were not altered after9-months storage.Interesterification conditions were optimized using response surface method based onone-factor experiments. Analysis of variance showed that reaction temperature was the mostimportant factor, the second one was catalyst dosage and the third one was reaction time. Theoptimized conditions were as follows: reaction temperature90℃, catalyst dosage1%(oilsweight), reaction time60min, residual pressure≤300Pa, stirring rate450r/min. It was foundthat many kinds of oils and fats were fully interesterified under the optimized conditions.Interesterified oils and fats without processing showed a blown color and semi-solid state atroom temperature and purification is needed before interesterified oils and fats is on sale dueto its2.5~3%base content.Effects of material qualities on the interesterification involving water content, acid value,peroxide value, antioxidant dosage and phospholipid content were studied.Water contentsignificantly extended the induction period but fully randomization was still reached under10%water content. When acid value was up to5.13mg KOH/g, a completely activity loss ofcatalyst was observed with catalyst content of1%(oil weight). The addition of peroxide valueextended the induction period but fully randomization was also observed. A dosage of500mg/kg BHA or TBHQ produced a longer induction period compared with control group. Itwas interesting to found that phospholipid have different effects on interestrificationdepending on dosage with a low content(1.9mg/g), promote and high content(10.5mg/g),inhibit. It is recommended that qualities of oils and fats used to interesterification should be asfollows: water content≤0.2%, acid value≤2.0mgKOH/g, peroxide value≤7.5mmol/kg,antioxidant dosage≤200mg/kg, phospholipid content≤10.5mg/g. Purification of interesterified lard was studied. The results showed that bothwashing(oil:water=1:6w/w) and centrifuging(5000r/min,15min)process were good methodto remove KOH and soap existing in interesterified lard. Washing had a limited ability toremove monoacylglycerols and diacylglycerols. Washing bring wasted water and need a lot ofpower compared with centrifuging.Centrifuging(5000r/min,15min) was able to remove95%totalalkali in the interesterified lard.Analysis of fatty acid compositon showed that there was no alteration in the total fattyacid composition before and after interesterification, sn-2fatty acid composition wassignificantly changed after interesterification and sn-2fatty acid composition of fullyrandomazation lard was similar with total fatty acid comopsiton. Evalution of tran-fatty acidshowed that interesterification process didn’t produce extra tran-fatty acid. Interesterificationproduced substantial rearrangement of the triacylglycerol species by increase the content ofUUU and SSS type triacylglycerol at the expense of UUS and USS type triacylglycerol.Evaluation of thermal behavior of both original and interestirified lard showed that meltingand crystallization thermograms are significantly modified by the randomization. X-raydiffraction analysis revealed that interesterification altered crystalline polymorphism and theinteresterified lard showed a predominance of the β’polymorph. Needle-like crystalmorphology of interesterified lard was observed by PLM analysis with more uniform crystalsize, more crystal number, more dense crystal network. SEM analysis showed that themicro-surface of interestrified lardbecome more smooth. The solid fat content have nochangeafter interesterified according to p-NMR analysis.