ORIGINAL PAPER Interesterification of Lard and Soybean Oil Blends Catalyzed by Immobilized Lipase in a Continuous Packed Bed Reactor Roberta Claro da Silva • Fabiana Andreia Schaffer De Martini Soares • Thaı ´s Gonzaga Fernandes • Anna Laura Donadi Castells • Kelly Caroline Guimara ˜es da Silva • Maria Ine ˆs Almeida Gonc ¸alves • Chiu Chih Ming • Lireny Aparecida Guaraldo Gonc ¸alves • Luiz Antonio Gioielli Received: 5 January 2011 / Revised: 1 April 2011 / Accepted: 26 May 2011 / Published online: 14 June 2011 Ó AOCS 2011 Abstract Structured lipids (SL), formulated by blends of lard and soybean oil in different ratios, were subjected to continuous enzymatic interesterification catalyzed by an immobilized lipase from Thermomyces lanuginosus (Lipo- zyme TL IM) in a continuous packed bed reactor. The original and interesterified blends were examined for fatty acid and triacylglycerol composition, regiospecific distribution, and solid fat content. Blends of lard and soybean oil in the pro- portions 80:20 and 70:30 (w/w), respectively, demonstrated a fatty acid composition, and proportions of polyunsaturated/ saturated fatty acids (PUFA/SFA) and monounsaturated/ polyunsaturated fatty acids (MUFA/PUFA), that are appro- priate for the formulation of pediatric products. These same blends were suited for this purpose after interesterification because their sn-2 positions were occupied by saturated fatty acids (52.5 and 45.4%, respectively), while unsaturated fatty acids predominantly occupied sn-1,3 positions, akin to human milk fat. Interesterification caused rearrangement of triacyl- glycerol species. Keywords Human milk fat substitute Á Lard Á Soybean oil Á 13 C-NMR analyses Á Triacylglycerol composition Introduction The interesterification of lipids catalyzed by lipases rep- resents an alternative to chemical interesterification. Eco- friendly processes for modifying fats and oils by utilizing lipases of different microbial origins have been reported by various researchers [1–3]. Lipase-catalyzed interesterifica- tion reactions can be performed in a batch-type reactor or in a continuous packed bed reactor [4]. The packed bed reactor is one of the most commonly employed apparatus for solid–fluid contacting in heterogeneous catalysis because it: (1) facilitates contact and subsequent separa- tion; (2) and the continuous removal of inhibitory sub- stances; (3) allows reuse of the enzyme without the need for prior separation; (4) permits the handling of poorly- soluble substrates by using large volumes containing low concentrations of substrate; (5) leads to more consistent product quality and improved enzyme stability due to ease of automation and control [5]; (6) is suitable for long-term and industrial-scale production, in contrast to stirred-tank reactors where enzyme granules are susceptible to breaking down because of mechanical shear stress; and (7) is more cost effective than batch operations [6–8]. Lipids are the major source of energy in human milk or infant formulas [9]. Hence, modification of fats and oils for infant formulas in order to obtain not only the correct fatty acid (FA) composition but also the same positional distri- bution as in human milk fat (HMF) via interesterification is a focus of investigation. The major saturated fatty acid (SFA) is palmitic acid (16:0), which represents about a R. C. da Silva Á F. A. S. D. M. Soares Á T. G. Fernandes Á A. L. D. Castells Á K. C. G. da Silva Á L. A. Gioielli (&) Department of Biochemical and Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, University of Sa ˜o Paulo, Av. Prof. Lineu Prestes n. 580, B16, Sa ˜o Paulo, SP CEP 05508-900, Brazil e-mail: lagio@usp.br M. I. A. Gonc ¸alves Department of Pharmacy, Faculty of Pharmaceutical Sciences, University of Sa ˜o Paulo, Av. Prof. Lineu Prestes n. 580, B13, Sa ˜o Paulo, SP CEP 05508-900, Brazil C. C. Ming Á L. A. G. Gonc ¸alves Department of Food Technology, Faculty of Food Engineering, University of Campinas, Caixa Postal 6091, Campinas, SP CEP 13083-970, Brazil 123 J Am Oil Chem Soc (2011) 88:1925–1933 DOI 10.1007/s11746-011-1869-x