Abd. Manaf, Mohd Yazid

Che Man, Yaakob

Lai, Oi Ming

Long, Kamariah

Mohd Ghazali, Hasanah

Mohd Ismail, Mariam

Yusof, Salmah

Universiti Putra Malaysia Institutional Repository

FOR Category F10800: Biological SciencesPREPARATION, CHARACTERISATION ANDAPPLICATIONS OF LIPASE-CATALYSEDINTERESTERIFIED FATS AND OILSHasanah Mohd Ghazali, Lai Oi Ming, Kamariah Long,Mariam Mohd. Ismail, Yaakob Che Man,Salmah Yusof and Mohd Yazid Abd. ManafFaculty of Food Science and BiotechnologyUniversiti Putra Malaysia, 43400 UPM, Serdang, Selangor,MalaysiaKeywords: microbiallipases, cell-bound lipase, trans-esterification, acidolysis, fat products.IntroductionInteresterification (interchange of the fatty acid molecules ofoils and fats) reactions can be catalysed either by chemi-cal/metal catalysts or enzymes (lipases). The latter has theadded advantages of being, natural, biodegradable, renew-able and more specific, and performs catalysis under mildconditions. Lipases catalyse a more directed reaction, form-ing more specific end products. Also, interesterification doesnot lead to the synthesis of trans fatty acids, usually formedduring the hydrogenation (hardening) of oils. These havebeen implicated in adversely affecting the levels of high-density lipoproteins in the blood. Some products that can beproduced using lipase-aided interesterification are margarine,shortenings, and replacement fats for processed cheese andice cream. The objective of the project was to evaluate the'interesterification performance of several lipases in the pro-duction of hard fat feedstock, low-temperature stable oils,and replacement fats from palm oil and its fractions. Studiesof cell-bound lipases were also carried out.Materials and MethodsLipases from several microbial sources were immobilisedonto Celite, lyophilised and then added to reaction mixturescomposed of oil/fat substrates. The mixtures were incubatedat 600C at 200 rpm for up to 6 h. At the end of reaction, theenzyme was removed and the reaction mixture were analysedto obtain the free fatty acid content, triglyceride profile,melting point, melting and cooling, and solid fat content. Ex-cept for the lformer, all other analyses were done after re-moval of the acids. Products like margarine, and processedcheese were formulated using blends of transesterified fats asthe feedstock. These were evaluated in terms chemically,physically and sensorily when freshly prepared and afterstorage. A cell-bound lipase is a naturally immobilised li-pase, and its application would reduce cost of immobilisa-tion. Aspergillus flavus isolated locally was found to producecell-bound lipase. A dried preparation of the lipase was usedin acidolysis reaction between an oil and an exogenous fattyacid. Incorportion of the fatty acid is monitored using GC,and the properties of the altered oils were determined as be-fore including texture analysis.Results and DiscussionResults when palm stearin was reacted with palm kernelolein, sunflower oil or milk fat show that two lipase sources _a Pseudomonas sp. and Rhizomucor miehei - were superior tothe other microbial lipases in causing changes to the stearin.Of the two, the Pseudomonas lipase was better, where theproducts of reaction were usually softer, and J3' crystals weredominant. Being GRAS, the Rhizomucor miehei lipase(Lipozyme IM60) was used in the preparation of transesteri-fied palm stearin: sunflower oil (40:60) mixture. The mixturewas then used in a pilot plant production of margarine. Stor-age studies indicated that the margarine was relatively stableto oxidation and change in colour. Storage also resulted inthe margarine becoming slightly firmer, making speadabilityless. Lower concentrations of palm stearin are recommendedto obtain a softer margarine. Lipozyme was also used to pro-duce a fat substitute for the production of processed cheese.The substrates of reaction were palm kernel olein and anhy-drous milk fat. Processed cheese was prepared by incorpo-rating known quantities of the transesterified fat into mix-tures containing mature cheddar cheese and plastien casein.Sensory evaluation of the product indicated that while textureand colour were acceptable (compared to commercial proc-essed cheese which acted as the control), the taste was foundto be slightly rancid. This was due to the presence of fattyacids, a by-product of the transesterification reaction, andshould be removed before the development of the cheese.The production conditions, properties and applications of thecell-bound lipase of a locally isolated strain of Aspergillusflavus was studied, and was the first to be reported in the lit-erature. The enzyme is an inducible enzyme, produced onlywhen oil was included in the growth medium. The bound en-zyme could be released from the cell wall through agitationin an aqueous solution. The presence of EDTA in the extrac-tion medium lowers losses due to proteolytic action. Thesoluble enzyme was found to be l,3-specific. In the dry form,the bound lipase was sufficiently stable to allow catalysis inorganic solvents. Acidolysis between coconut oil (containsmainly lauric and myristic acids and negligible quantities ofstearic acid) for example, and stearic acid in the presence ofthe dry enzyme resulted in the formation of 'coconut oil'containing significant quantities of stearic acid. The slipmelting point of this product which was higher than coconutoil, and the triglyceride and melting profiles obtained fromHPLC and DSC analyses reflected the incorporation ofstearic acid into coconut oil. Similar 'novel' products wereobtained when different oils and fatty acids were used as thesubstrates. Transesterification reaction was also successfullycarried out.ConclusionsLipases are capable of transforming the physical and chemi-cal characteristics of fats and oils, and through proper selec-tion of fats/oils mixtures, feedstocks could be prepared thatare suitable for margarine and processed cheese production.Naturally immobilised cell-bound lipase can successfully beused in fats and oils transformation reactions.Supported by [RPA Grant 03-02-04-0025209

Preparation, characterisation and applications of lipase-catalysed interesterified fats and oils

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Preparation, characterisation and applications of lipase-catalysed interesterified fats and oils

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