Lard and high-oleic sunflower oil (Trisun ® Extra) were interesterified at 55°C for 24 h with SP435 lipase from Candida antarctica to produce plastic fats. As the amount of trisun increased, percentage free fatty acid, unsaturated fatty acid/saturated fatty acid value, oxidizability, and the amount of 18:1 found at the sn-2 position of triglyceride products increased. Differential scanning calorimetry showed that the lowmelting components in the product contained more 18:1 than the high-melting components. A 60:40 (w/w) ratio of lard to trisun had the widest plastic range (3-26°C). The scaled-up reaction to produce this blend resulted in a product that had 60.1% 18:1 at the sn-2 position compared to 44.9% for the physical blend. The solid fat content of the 60:40 interesterified mixture resembled soft-type margarine oil. JAOCS 75, 1339JAOCS 75, -1345JAOCS 75, (1998. KEY WORDS:Candida antarctica lipase, differential scanning calorimetry of triglyceride, lard, oxidative stability of triglyceride, plastic fats, solid fat content, spreadability of triglyceride, triglyceride structure and properties,Trisun ® Extra, lard.

The structural composition and thermal properties of the products of enzymatic interesterification of triolein and tristearin were investigated. The biocatalyst for the reaction was an immobilized Candida antarctica lipase, SP435. Enzyme load of 10% (w/w reactants) produced 72% of desired total products. Oleoyl-distearoyl triglycerides (SSO, OSS) had higher melting points than dioleoyl-stearoyl triglycerides (OOS, SOO) because the sample contained larger amounts of stearic acid than oleic acid residues. SOS and OSO were hardly produced (0.2 to 1.2%), which indicates that SP435 acted as a nonspecific lipase when catalyzing the interesterification of triolein and tristearin. The maximal yield of OSS and SSO (46.9%) was achieved with a 1:2 mole ratio of triolein to tristearin. As the proportion of tristearin was increased, the production of SOO and OOS decreased, the melting profile of the interesterified triglycerides shifted toward higher melting forms, and the solid fat content increased, indicating formation of hard fats. JAOCS 75, 711-716 (1998). FIG. 2. Differential scanning calorimetry (DSC) heating thermograms of interesterified triolein and tristearin. Pretreatment: heated to 80°C at 200°C/min; cooled to −40°C at 10°C/min; held for 30 min; heating program: heated to 80°C at 5°C/min.FIG. 3. Percentage yield of products from interesterification of triolein with various mole ratios of triolein to tristearin by SP435 lipase. Each mixture was incubated at 55°C for 24 h. Total product: OSS + SSO + SOS + SOO + OOS + SOS, where OOO = triolein, OOS, SOO, and DSD = dioleoyl-stearoyltriglycerides; SSO, OSS, and SOS = oleoyldistearoyl triglycerices; SSS = tristearin.

Two systems were investigated and compared as models for making margarine-type fats. Two immobilized lipases, IM60 from Rhizomucor miehei and SP435 from Candida antarctica, were used to catalyze the transesterification of triolein with stearic acid and stearic acid methyl ester, respectively, in n-hexane. The optimal reaction temperature for both enzymes was 55°C at a mole ratio of triolein to acyl donor of 1:2. Equilibria were reached at 18 h for IM60 and 24 h for SP435. Analysis of the overall yield and incorporation of fatty acid at the sn-2 position indicated that the triacylglycerol products contained 38.4 and 16.2% 18:0 for acidolysis and 34.2 and 11.3% for interesterification reactions, respectively, at the 2-position. With SP435, the softest fat was produced after 18 h of incubation, and the hardest after 30 h. For IM60 system, 18 h of incubation gave the most plastic fat. JAOCS 75, 511-516 (1998).Enzymatic interesterification of fats and oils is at the experimental stage in efforts to replace the hydrogenation process for making margarine-type fats and butters (1). Hydrogenation reduces double bonds to single bonds, thereby increasing the melting point of the fat. However, this method results in the formation of geometric isomers, i.e., trans rather than cis configuration. Several reports have been published on the effect of trans fatty acid (FA) consumption. Epidemiologic evidence has linked trans FA consumption to high blood total cholesterol and low-density lipoprotein cholesterol levels and to increased incidence of death related to coronary heart disease (2).Lipases from Rhizomucor miehei (IM60) and Candida antarctica (SP435) can be used for acylglycerol modifications to achieve desirable physical properties of fats for margarine or specialty fats (3)(4)(5). This can be done through positional and specific FA exchange. Essential and other desirable FA have been used as substrates in enzymatic modification of fats and oils for better nutritional products (3,4). Reports indicate that enzymatic interesterification enables higher unsaturation at sn-2 position (6) where the FA are absorbed most readily (7,8).The use of high-and low-melting fats has been investigated to improve the spreadability of butter (9). Hernqvist et al. (10) studied the polymorphic behavior of complex triacylglycerols that are formed by interesterification of simple triacylglycerols, such as triolein, trielaidin, and tristearin. These triacylglycerols were chosen as model systems for vegetable oils with possible application in the manufacture of margarine. D'Souza et al.(11) compared the chemical and physical characteristics of the high-melting acylglycerols extracted from soft margarines and used the data to explain the differences observed in polymorphic behavior.IM60, a 1,3-specific lipase, has been shown to work best with free FA (12,13), and SP435, which is a nonspecific lipase under some conditions, to perform best with FA esters in transesterification reactions (14,15). Therefore, in this paper, two systems were chosen and c...