Obtaining a hydrolyzed milk fat fraction enriched in conjugated linoleic acid and trans-vaccenic acid Sergio I. Martínez-Monteagudo, Mohamed Khan, Feral Temelli, Marleny D.A. Saldaña * Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6G 2P5 article info Article history: Received 28 February 2013 Received in revised form 18 December 2013 Accepted 19 December 2013 abstract Anhydrous milk fat (AMF) rich in conjugated linoleic acid (CLA) and trans-vaccenic acid (TVA) was enzymatically hydrolyzed and dry fractionated. Oxidation kinetic parameters of hydrolyzed AMF was determined by differential scanning calorimetry. Hydrolysis yielded 90.4% free fatty acids (FFAs) after 24 h at 50  C, using a ratio of 70 for water to fat (w/w) and a ratio of 40 for enzyme to fat (w/w). The oxidation of hydrolyzed AMF started at a lower temperature (108.3  4.1  C) compared with non- hydrolyzed AMF (155.7  3.4  C). Upon fractionation of hydrolyzed AMF, three fractions were ob- tained (high-, middle- and low-melting point FFA fractions). The middle fraction contained the highest concentration of CLA and TVA (64.8 and 249.3 mg g 1 fat, respectively). The middle fraction shows great potential for fortification of dairy products but further optimization is needed to maximize the CLA and TVA contents, while minimizing the presence of the other fatty acids. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Milk fat is recovered during the production of skim milk and subsequently converted into anhydrous milk fat (AMF), which can be stored for months (Augustin & Versteeg, 2006). The increasing demand for fat-free dairy products due to health concerns associ- ated with the consumption of milk fat have generated a large excess of milk fat stocks worldwide (Lubary, Hofland, & ter Horst, 2011). In addition, AMF presents important technological disadvantages due to its wide melting point range (40 to 40  C) and the relatively high content of saturated fatty acids (Lubary et al., 2011). Various researchers have highlighted the health benefits of some fatty acids naturally found in milk fat while searching for alternatives to add value to milk fat (Küllenberg, Taylor, Schneider, & Massing, 2012; Merrill et al., 1997; Molkentin, 2007). Among these, conjugated linoleic acid (CLA, C18:2) has been shown to have health benefits, such as reducing the risk of cancer and athero- sclerosis, as well as weight control, and bone formation (Cook & Pariza, 1998; Fritsche et al., 1999; Lock & Bauman, 2004; Park, 2009). Another important fatty acid with health-promoting and disease-prevention properties is trans-vaccenic acid (TVA, C18:1 t11), a metabolic precursor of CLA (Jacome-Sosa et al., 2010; Wang et al., 2008). Although trans fatty acids naturally found in milk fat are associated with these positive health benefits, trans fatty acids formed during the hydrogenation process for margarine production have been shown to have negative effects, increasing the risk of heart disease (Wang, Jacome-Sosa, & Proctor, 2012). CLA and TVA are minor components of milk fat, representing about 1 and 3% of the total milk fat, respectively (Creamer & MacGibbon, 1996). However, CLA and TVA can be isolated for further use as an ingredient to fortify food products (Lubary et al., 2011). Romero, Rizvi, Kelly, and Bauman (2000) fractionated non- hydrolyzed AMF using supercritical carbon dioxide and reported an increase of 89%, with CLA reaching a final concentration of 7.8 mg g 1 fat. A 2.3-fold increase of CLA was reported in milk fat crystallized with urea (Kim & Liu, 1999). These authors showed that the long-chain saturated fatty acids formed a complex with urea, which was later eliminated by filtration. Consequently, a reduction in the concentration of saturated fatty acids was reported along with an increase in CLA content. O’Shea, Devery, Lawless, Keogh, and Stanton (2000) obtained a milk fat fraction enriched in CLA with a final concentration of 22 mg g 1 , representing a 63% increase compared with that in the parent fat. In addition, an increase of 36% of TVA was obtained in the same fraction. The fraction was obtained at a crystallization temperature of 10  C and a cooling rate of 0.58  C min 1 . Rehberger, Butikofer, Bisig, and Collomb (2008) concentrated CLA from anhydrous milk butter and highland but- ter using a two-step fractionation. The first fraction was obtained at 20  C, which was fractionated again at 12.5  C using a cooling rate of 0.2  C min 1 . After the second fractionation step, the concen- tration of CLA increased to 18.6% and 9.2% for anhydrous milk and * Corresponding author. Tel.: þ1 780 492 8018. E-mail addresses: Marleny.Saldana@ales.ualberta.ca, marleny@ualberta.ca (M.D.A. Saldaña). Contents lists available at ScienceDirect International Dairy Journal journal homepage: www.elsevier.com/locate/idairyj 0958-6946/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.idairyj.2013.12.010 International Dairy Journal 36 (2014) 29e37