Food Chemistry 139 (2013) 571–577

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Food Chemistry

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The effect of interesterification on the bioavailability of fatty acidsin structured lipids

M. Farfán a, M.J. Villalón b, M.E. Ortíz b, S. Nieto c, P. Bouchon a,⇑a Department of Chemical and Bioprocess Engineering, Pontificia Universidad Católica de Chile, P.O. Box 360, 6904411, Chileb Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, P.O. Box 114D, 8330024, Chilec Laboratory of Lipids and Antioxidants, Institute of Nutrition and Food Technology (INTA), Universidad de Chile, P.O. Box 138-11, 7830490 Santiago, Chile

a r t i c l e i n f o

Article history:Received 5 September 2012Received in revised form 30 November 2012Accepted 7 January 2013Available online 23 January 2013

Keywords:BioavailabilityInteresterificationSolid fat contentStructured lipidFatty acid profile

0308-8146/$ - see front matter � 2013 Published byhttp://dx.doi.org/10.1016/j.foodchem.2013.01.024

⇑ Corresponding author. Tel./fax: +56 2 3547962.E-mail address: pbouchon@ing.puc.cl (P. Bouchon)

a b s t r a c t

Fatty acid (FA) profile is a critical factor in the nutritional properties of fats, but, stereochemistry may alsoplay a fundamental role in the rate and extent to which FAs are absorbed and become available. To betterunderstand this phenomenon, we evaluated the bioavailability of FAs in linseed-oil and palm-stearinblends compared to their interesterified mix, using a sn-1,3 stereospecific lipase, to determine if therewas any difference in terms of FA availability when using this technology. Test meals were fed throughan intragastric feeding tube on Sprague-Dawley male rats after 18 h fasting. Postprandial blood sampleswere collected after meal or physiological serum (control) administration and the FA profile of plasmalipids was determined. Results showed that modification of the melting profile through interesterifica-tion, without altering the bioavailability determined by sn-2 stereochemistry, could delay lipid absorp-tion at the beginning, but had no effect on total lipid absorption.

� 2013 Published by Elsevier Ltd.

1. Introduction

The technological applications of fat depend on its physical andchemical properties. These and nutritional properties are limitedby the composition of fatty acids (FAs) and the stereochemistryof triacylglycerols (TAGs) of fats (Gunstone, 2006). In order to im-prove technological applications and preserve the sensorial attri-butes of fats, scientists have modified them using fractionationand blending. However, the preferred way to achieve the desiredsemi-solid consistency is hydrogenation (Ribeiro, Grimaldi, Gioelli,& Gonçalves, 2009). In cases where hydrogenation is partial, thismay lead to the production of trans fatty acids, which are knownto have detrimental health effects (Hunter, 2006).

Although fractionation and blending are still used, interesterifi-cation is an alternative process that also alters the physical proper-ties of fats without producing the undesirable trans FA (Rodrigues& Gioielli, 2003). Interesterification is a reaction that involves FAredistribution between and within TAG molecules, until a thermo-dynamic equilibrium is reached (Idris & Mat Dian, 2005; Karabulut,Turan, & Ergin, 2004). The resulting products maintain the FA pro-file and saturation degree of the starting blends (Karabulut et al.,2004; Rodrigues & Gioielli, 2003), but present a different TAGs ste-reochemistry, which results in new physical–chemical characteris-tics and nutritional properties (Klinkesorn, H-Kittikun, Chinachoti,

Elsevier Ltd.

.

& Sophanodora, 2004). Two kinds of catalysts promote this reac-tion: chemical and enzymatic. Chemical interesterification (CI) isless expensive and has a shorter reaction time than enzymaticinteresterification (Klinkesorn et al., 2004), but lacks stereospeci-ficity. This means that it produces random rearrangements unlessthe lower temperatures are strictly controlled. As a result, solidTAGs cannot react and exchange FA with melted TAGs, and remainas such (O’Brien, 2004). Enzymatic interesterification (EI) usescommercial lipases from plant, animal, and microbial sources. EIis driven under milder temperature conditions (Criado, Hernán-dez-Martín, López-Hernández, & Otero, 2007; Rodrigues & Gioielli,2003; Yankah & Akoh, 2000), undergoes fewer deleterious side-reactions, and produces fewer by-products (Chu et al., 2001; Wang,Wu, Ho, & Weng, 2006). However, the most important characteris-tic of EI is its regiospecificity. For instance, lipases may hydrolizethe sn-1 and sn-3 positions, incorporating FA at these sites withoutchanging the FA in the sn-2 position (Wang et al., 2006). EI is thusmost suitable for interesterifying fats and oils that are more sensi-tive to high temperatures and for producing technological andnutritionally superior fats (Chu et al., 2001; Yankah & Akoh,2000; Zhang, Smith, & Adler-Nissen, 2004). In accordance, CI andEI can create new TAGs from fat and oil blends, changing the FAresidues and/or their positional distribution on the glycerol back-bone. These new fats have been defined as structured lipids (SL),and are synthesized to improve the physical and/or chemical char-acteristics of natural fats (López-Hernández, García, & Hill, 2005).For instance, interesterification modifies the solid fat content

572 M. Farfán et al. / Food Chemistry 139 (2013) 571–577

(SFC), which is responsible for some organoleptic properties(spreadability, thickness, and flavour release), stability, and easeof packing, and may determine the suitability of oils and fats forspecific applications (Karabulut et al., 2004; Zhang et al., 2004).

Interesterification is also used to achieve more efficient deliveryof specific FA for nutritional and medical purposes. The synthesis ofstructured lipids (SL) allows for the supply of the desired FA andTAGs profiles (Hamam, Daun, & Shahidi, 2005). Interesterificationhas been used to synthesize commercial fats such as Betapol™ (Li-pid Nutrition) and Salatrim™ (short and long acyltriglyceride mol-ecule). Betapol is a human milk fat substitute that containspalmitic acid mainly at the sn-2 position and reduces fat and cal-cium fecal loss. This SL was developed because newborns’ imma-ture digestive systems are unable to efficiently absorb a differentfat stereochemistry (López-López et al., 2001). Salatrim is an SLwith a lower energy value (�5 kcal/g) that is produced using shortchain FA that provides fewer calories than a longer FA (Smith et al.,1994). Furthermore, interesterification allows for the introductionof essential FA into oils, which may be useful in the treatment ofcertain clinical disorders (Hamam et al., 2005).

However, the FA profile is not the only factor that determinesthe nutritional properties of fats. Stereochemistry plays a funda-mental role in the rate and extent to which a FA contained in ameal is absorbed and becomes available for any metabolic andstructural functions or as a source of energy, a concept defined asbioavailability (Parada & Aguilera, 2007; Singh & Singh, 2011).The nature of each FA and its position on TAG will determinewhether or not it will be absorbed. First, free FAs and sn-2 monoa-cylglycerols are produced by successive hydrolysis. The latter is ab-sorbed by lymphatic way, regardless of the FA’s nature. However,free FA may be either: (a) absorbed by portal way; (b) absorbedby lymphatic way; or (c) lost as Ca or Mg salts depending on thenature of the FA (Mu & Høy, 2004). In accordance lipids bioavail-ability could be modified to meet specific needs, which in turnwould change the triacylglycerol structure, state of aggregation,and physical properties of the food matrix (Asselin et al., 2004;Yli-Jokipii et al., 2003).

In fact, randomization of FAs on TAG molecules may determinethe bioavailability of specific FA. In vivo studies (Lien, Yuhas, Boyle,& Tomarelli, 1993) have demonstrated significant differences in to-tal lipid fecal excretion after randomization. Similarly, plasma orchylomicron TAGs have been evaluated after the intake of random-ized fat. Some researchers (Chistensen & Høy, 1996; Hodge, Li, Red-grave, & Sinclair, 1999) have concluded that there are differencesbetween randomized and non-randomized group absorption ratesduring the first few hours. However, the nature of FA has takenprecedence over stereochemistry (Chistensen, Høy, Becker, &Grove, 1995). Other studies have evaluated the bioavailabilitydetermined by the physical state. Bonnaire et al. (2008) reportedthat fats with different melting profiles and equal FA compositionpresented slower digestion of solids than liquid particles in in vitroassays. Asselin et al. (2004) reported different absorption rates be-tween high melting profile fats and those with medium-low melt-ing profiles within the first 3 h in in vivo tests. Moreover, the high

Table 1Main fatty acids composition of raw materials as well as linseed oil (LO) and palm stearin

Fatty acids (%)

C14:0 C16:0 C18:0

Linseed oil (LO) – 5.60 ± 0.006 4.44 ± 0Palm stearin (PS) 1.14 ± 0.006 57.52 ± 0.006 6.87 ± 0LO/PS mix: 70/30 0.34 ± 0.006 21.18 ± 0.010 5.17 ± 0LO/PS mix: 60/40 0.46 ± 0.006 26.37 ± 0.006 5.41 ± 0LO/PS mix: 50/50 0.57 ± 0.006 31.56 ± 0.010 5.66 ± 0

melting profile group excreted a larger amount of fat (P < 0.05)than other groups. However, it is important to consider that thesefats had different FA profiles since they were obtained from milkfat fractionation, thus, it was not possible to isolate the effect ofthe nature of the FA over the melting point of the fat. Yli-Jokipiiet al. (2003) evaluated the effects of different melting profiles withan equal FA profile and found easier emulsification and fasterabsorption at 30 �C in liquid fat as compared to solid fat (SFC of18.3% and 27.6%, respectively). This agrees with the results pre-sented by Lien et al. (1993), who reported that tri-saturated TAGs(higher melting point) are not as easily digested and absorbed asTAGs with a lower melting point (containing unsaturated fattyacids or short-chain saturated fatty acids). In accordance, the aimof this study was to evaluate the bioavailability of FA in linseed-oil and palm-stearin blends compared to their interesterifiedmix, when using an sn-1,3 stereospecific lipase, that is, withoutmodifying the bioavailability determined by sn-2 stereochemistry,to understand if there could be any drawback in terms of FA avail-ability when using this technology.

2. Materials and methods

2.1. Dietary fats

In order to obtain dietary fats, we developed binary blends oflinseed oil (LO) and palm stearin (PS), which were either intereste-rified (IE) or non-interesterified (nIE). LO and PS were chosen be-cause of the high melting point (49 �C) and saturated FA content(>60%) of PS and the high x-3 content (�50%) of LO. Three blendsof LO/PS mass ratios (70/30, 60/40 and 50/50) were evaluated inorder to have a wide range of solid fat content (SFC). LO was pur-chased from Fontevita (Nutra Andes Ltd., Santiago, Chile), and PSwas supplied by Cox & Co. (Santiago, Chile) as Danfat MIX-4547.Most important FAs of raw materials and mixes are shown inTable 1.

In order to interesterify, we used Lipozyme TL IM as a catalyst(Blumos S.A., Santiago, Chile), which only hydrolyses the sn-1and sn-3 positions of TAGs. Briefly, each blend was melted anddried under vacuum conditions. The catalyst was added at 5%(w/w) and the reaction was performed under vacuum conditions(100 Torr) and agitation (150 rpm) at 70 �C for 120, 180, 240, and300 min (López-Hernández et al., 2005; Zhang et al., 2004). Thecatalyst was separated by filtration and interesterified blends werestored at 4 �C under a nitrogen atmosphere.

2.2. Animals and test meals

Forty-eight male eight week-old Sprague-Dawley rats weighing�300 g were given free access to a 4% fat commercial diet andwater. They were divided into three groups. One was given a testmeal with interesterified fat (IE), one had non-interesterified fat(nIE), and one was used as a control (C) group. After 18 h of fastingwith free access to water, the rats were anesthetized in an induc-tion chamber with isofluorane/oxygen, and intubated with an oral

mixes (PS) used in this study.

C18:1n-9 C18:2n-6 C18:3n3

.010 23.97 ± 0.010 16.68 ± 0.006 49.31 ± 0.006

.010 27.66 ± 0.012 6.81 ± 0.010 –

.010 25.08 ± 0.006 13.72 ± 0.006 34.52 ± 0.012

.010 25.45 ± 0.006 12.73 ± 0.006 29.59 ± 0.010

.006 25.82 ± 0.006 11.75 ± 0.010 24.66 ± 0.010

M. Farfán et al. / Food Chemistry 139 (2013) 571–577 573

gastric feeding tube. 1 ml of test meal at 36 �C or 1 ml physiologicalserum for C group was administrated via the feeding tube andrecovery was allowed. The rats were returned to their cages untilblood sample extraction at 0 (before administration), 1.5, 3, 4.5,8, and 12 h after the test meal or physiological serumadministration.

In order to obtain the blood sample, the rats were anesthetizedin the induction chamber and then arranged in surgery positionwith anaesthesia flow through a nosecone. The abdominal cavitywas opened and blood was collected from the abdominal aortausing a K2EDTA vacutainer tube. After blood extraction, rats weresacrificed by exsanguination, which was verified by perforatingthe diaphragm.

All procedures were approved by the Bioethical and BiosafetyCommittee of the Faculty of Biological Sciences of Pontificia Uni-versidad Católica de Chile.

2.3. Analytical procedures

2.3.1. Determination of interesterification kinetics through solid fatcontent measurements

Since interesterification modifies the melting profile of lipids,which is unstable until thermodynamic equilibrium is reached(Idris & Mat Dian, 2005), the solid fat content (SFC) was used asan indicator of this equilibrium. The SFC of enzymatically inter-esterified blends was measured by pulsed Nuclear Magnetic Reso-nance (p-NMR) according to AOCS Official Method Cd 16-81(1993). Briefly, dry and filtered samples were put into glass tubesand completely melted (10 min, 60 �C) and then solidified (0 �C,30 min). Thereafter, samples were allowed to melt into a thermo-stated bathwater at 10.0, 21.1, 26.7, 33.3, and 40.0 �C for 15 min.Finally, the SFC was measured in a Bruker Minispec PC120s p-NMR analyser (Bruker Analytische Mestechnik, Rheinstetten,Germany).

2.3.2. FA profile of dietary fatsThe fatty acid methyl esters concentration of raw materials and

interesterified blends was determined by conversion into corre-sponding methyl esters of fatty acids residues followed by GC(gas chromatograph HP 5890 and a capillar column BPX-70,50 m, 0.25 lm). This was carried out according to AOCS OfficialMethod Ce 1-62 (1997).

2.3.3. FA profile of plasma lipidsBlood samples were centrifuged at 3000 rpm, 4 �C for 10 min.

Plasma was separated and stored at �18 �C until the lipids wereisolated. Lipids were extracted using the method described byBligh and Dyer (1959), converted into methyl esters using themethod described by Morrison and Smith (1964), and analysedby GC using a GC Hewlett Packard 7890 (column J and W DB-FFAP,30 m, 0.25 mm ID, 0.25 lm, FID detector).

Fig. 1. Melting profiles of non-interesterified (0 min) and interesterified blendsduring 120, 180, 240, and 300 min of 70/30 (A), 60/40 (B) and 50/50 (C) weight ratiomixes of LO/PS.

2.3.4. Statistical analysisThe absorption studies were performed in parallel to reduce dif-

ferences caused by external factors. The results are expressed asthe mean ± standard error (SEM) of 3 rats in each group. Statisticalsignificance of differences between groups was determined usingone-way ANOVA followed by the Tukey HSD test. Differences wereconsidered significant at P < 0.05. Statistical analysis was per-formed using Statgraphics 5.0 (Manugistic Inc., Oackland, Va.,USA). Areas under the curve were determined using GraphPadPrism 5.0 (GraphPad Software, Inc., CA, USA).

3. Results and discussion

3.1. Dietary fats

Interesterification modifies the melting profile of lipids, whichvaries until thermodynamic equilibrium is reached. The SFC wasused as an indicator of this equilibrium. Fig. 1 shows the meltingprofiles of the nIE blends (0 min) and blends interesterified during120, 180, 240, and 300 min of 70/30, 60/40 and 50/50 weight ratiosmixes of LO/PS. There are significant differences between nIEblends and the interesterified blends in all mixes. Further, for allcompositions there are no differences between melting profilesat 120, 180, 240 and 300 min of interesterification. This suggeststhat thermodynamic equilibrium is reached at 120 min of process-ing, which is enough to modify the melting profile of lipids. Pro-longed exposure of the blend to high temperatures could lead to

Fig. 2. Melting profiles of interesterified (IE, at equilibrium) and non-interesterified(nIE) blends of 70/30, 60/40, and 50/50 weight ratio mixes of LO/PS.

574 M. Farfán et al. / Food Chemistry 139 (2013) 571–577

thermo-oxidative degradation of the finished product. Otherauthors have reported shorter and longer periods of interesterifica-tion (Ibrahim, Guo, & Xu, 2008; Yankah & Akoh, 2000), but this de-pends on enzyme load and activity, the variety of TAGs in the rawmaterial, FA-enzyme affinity, and temperature (Wang et al., 2006).

For all nIE blends, the interesterification process reduced theSFC at every temperature measured, as reported in other studies(Chu et al., 2001; Criado et al., 2007). As reflected in this work,the effect of interesterification is notorious in the presence ofhigh-melting TAG species, reducing significantly the SFC of themix. Fig. 2 shows the melting profiles of 70/30, 60/40 and 50/50IE and nIE LO/PS blends. As was expected, when a higher PS con-tent is used a higher melting profile is observed, since PS is a nat-ural hard component. Thus, the 50/50 blend has higher SFC thanthe 60/40 blend and this has higher SFC than the 70/30 blend. Inaccordance, 50/50 IE and nIE blends curves have a stronger slopeand may be considered plastic for a wider temperature range,but are waxier than the 60/40 and 70/30 blends. These resultsare in agreement with those reported by Chu et al. (2001) and Cri-ado et al. (2007).

3.2. Test meals

We decided to use 60/40 blends to evaluate the bioavailabilityof lipids, since at administration temperature (36 �C), the IE blendwas completely liquid and had a higher difference in SFC respect tothe nIE mix, compared to the 50/50 blend. This allowed us to eval-uate whether or not the interesterification process together withthe physical state of the matrix had an influence on lipid absorp-tion. PS is rich in palmitic acid (P) and tripalmitin (PPP), while LO

Fig. 3. Reaction scheme of two characteristic TAGs of PS (tripalmitin: PPP) and LO (trilinconsidered to be equal.

is rich in linolenic acid (Ln) and trilinolein (LnLnLn) (Xu, 2000).As an example, Fig. 3 shows the reaction scheme of these two char-acteristic substrates (PPP) and (LnLnLn), when using sn-1,3 stereo-specific lipase, to illustrate the different combinations that mayresult. As PS and LO contain other TAGs as substrates in additionto PPP and LnLnLn, all previous configurations might be found inboth nIE and IE blends, but at different proportions: nIE is richerin trisaturated and disaturated TAGs than the IE blend. As a result,different SFCs are obtained at the same temperature.

The fatty acid profiles of test meals and the concentration ofmajor FA in plasma lipids before and after test meal administrationare shown in Table 2. No statistical differences were observed inabsorption of total FA and individual FA between IE and nIE testmeals under the conditions used for the study. However, it isimportant to know that the effect of the test meal intake wasquickly reflected in lipemia. For all FA ingested, the individual con-centrations significantly increased after test meal dosification. In-creases were even observed in those administered at a loweramount or not at all as C18:0 and C20:4n6 (5.4% and 0% of dietaryfat), though to a lesser extent.

Before any test meal administration, the content of 18:3n3 waslower than 10 lg/ml. After the administration, the 18:3n3 contentincreased to 375.84 and 255.31 lg/ml in the first measurement forIE and nIE test meals, respectively. Similar results were observed inthe studies using rats published by Chistensen and Høy (1996) andChistensen et al. (1995). They reported null content of EPA or DHA(essential FAs) before test meal administration and significant in-creases after administration. This is possible because an essentialFA cannot be synthesized de novo by humans and other mammali-ans. As such, C18:3n3 was defined as our biomarker. But how couldplasma in fasting state be as rich in other essential FA as C18:2n6and C20:4n6? Although plasma lipids reflect the dietary fat in-gested over a period of a few hours (mainly transported by chylo-microns), other lipoproteins synthesized in enterocyte ininterprandial and fasting states transport important amount of lip-ids as well. The lipoproteins responsible for TAG transport at thesemoments are very low-density lipoproteins (VLDLs), which may besynthesized in both the liver and enterocyte. The VLDLs of entero-cyte transport remained and have sloughed enterocyte lipids.Therefore, FAs that are plentifully ingested may appear in interp-randial and fasting states including essential FAs as C18:2n6 andits desaturated and elongated product C20:4n6.

A similar effect is observed for total FA, as shown in Fig. 4A,where an unexpected increase is observed at t = 8 h in the controlgroup. The variability in serum triglycerides may be due to the pro-longed fasting and carbohydrate starvation with the resulting needfor sources of energy (Man & Albrink, 1956).

It is also important to note the rates at which lipids are ab-sorbed. Fig. 4B shows that the absorption kinetics of 18:3n3 inthe nIE test meal appeared to be slightly retarded than the onepresent in the IE test meal, showing absorption peaks after 4.5

olenin: LnLnLn), when using sn-1,3 stereospecific lipase. TAGs in each rectangle are

Tabl

e2

Mai

nfa

tty

acid

sco

mpo

siti

onof

test

mea

lan

dco

ncen

trat

ion

inpl

asm

alip

ids

afte

rin

tere

ster

ified

(IE)

and

non-

inte

rest

erifi

ed(n

IE)

test

mea

lad

min

istr

atio

n( l

g/m

l).

Fatt

yac

idPe

rcen

tage

inte

stm

eal

(%)

Con

cen

trat

ion

offa

tty

acid

sin

plas

ma

lipi

dsbe

fore

(0h

)an

daf

ter

1.5,

3,4.

5,8

and

12h

test

mea

lad

min

istr

atio

n(l

g/m

l)

IEte

stm

eal

nIE

test

mea

l

01.

53.

04.

58.

012

1.5

3.0

4.5

8.0

12

14:0

0.46

7.08

±0.

8717

.18

±1.

939.

68±

0.13

11.3

8±

2.16

21.5

9±

3.75

13.8

2±

1.64

12.9

9±

1.99

11.4

2±

0.74

14.3

9±

3.42

17.6

6±

2.79

12.9

1±

0.90

16:0

26.3

732

0.59

±23

.22

764.

69±

82.0

642

5.13

±15

.47

595.

08±

92.3

655

1.56

±69

.86

517.

23±

46.4

361

8.08

±68

.49

496.

55±

18.2

763

1.24

±11

0.00

782.

75±

154.

1649

2.38

±23

.87

18:0

5.41

169.

66±

19.1

825

6.48

±13

.23

207.

91±

7.04

243.

44±

28.2

623

1.76

±11

.75

255.

39±

22.7

023

9.85

±19

.48

220.

90±

4.19

240.

89±

29.3

928

2.38

±36

.63

239.

17±

5.81

18:1

n9

25.4

524

1.10

±15

.11

623.

48±

64.2

534

3.01

±9.

5947

1.78

±84

.97

440.

33±

72.8

536

5.52

±41

.85

484.

71±

52.1

740

3.77

±25

.52

553.

86±

98.2

158

3.79

±11

6.30

300.

58±

15.3

018

:2n

612

.73

307.

84±

17.0

560

4.02

±48

.70

353.

98±

15.3

047

2.40

±73

.33

446.

81±

81.3

545

4.34

±38

.27

518.

20±

44.0

943

8.53

±19

.52

530.

11±

87.0

359

8.94

±10

7.73

419.

41±

23.3

018

:3n

329

.59

9.56

±0.

3037

5.84

±87

.27

187.

68±

9.15

306.

26±

66.8

419

2.86

±39

.62

44.1

0±

11.8

325

5.31

±47

.04

231.

98±

23.7

141

1.90

±87

.27

400.

08±

129.

6028

.56

±1.

6220

:4n

6–

268.

20±

19.9

434

2.02

±21

.69

323.

31±

8.77

288.

82±

33.7

134

3.53

±19

.44

414.

49±

43.5

440

1.12

±20

.71

321.

60±

5.73

283.

33±

28.9

832

3.70

±26

.24

381.

46±

15.3

2To

tal

100

1498

.54

±55

.76

3290

.21

±31

6.32

2060

.22

±72

.97

2603

.70

±41

3.53

2512

.60

±31

7.79

2330

.22

±20

1.76

2823

.47

±27

3.41

2351

.21

±96

.97

2886

.86

±47

8.02

2433

.97

±11

2.21

2094

.46

±44

.44

Fig. 4. Absorption curve of Total FA (A) and C18:3n3 (B) after interesterified (IE),non-interesterified (nIE) and control sample administration.

M. Farfán et al. / Food Chemistry 139 (2013) 571–577 575

and 1.5 h, respectively. This may be attributed to the higher melt-ing point of nIE test meal that is richer in trisaturated and disatu-rated TAGs, which may retard the absorption of the meal. Thiscoincides with the findings of Asselin et al. (2004), who reportedlower absorption and higher lipid fecal losses for high melting pro-files as compared to low and medium melting profiles. However,this study compared fats with different FA profiles and thus en-hanced the differences between the test meals. It is important tonote that the control group’s C18:3n3 levels were constant and al-most zero during the experiment. This confirms the usefulness ofthis FA as a biomarker. Finally, plasma C18:3n3 had practically dis-appeared at t = 12 h.

Fig. 5 shows the area under the C18:3n3 plasma concentrationtime curve (AUC) after nIE and IE test meals as well as the control,which reflects the absorbed FA at all measurements. Due to the re-tarded maximum concentration of individual FA of nIE comparedto IE, there are differences in the means, but they are not signifi-cant at any time. These findings suggest that different melting pro-files do not interfere with absorption of C18:3n3 when the FAprofile is preserved. In this way, C18:3n3 is equally bioavailablein both semisolid and liquid fats.

4. Conclusions

This study was designed to evaluate enzymatic interesterifica-tion as a tool for modifying fats in order to improve their physicalproperties and observe these changes on lipid absorption.

Our results indicate that the methodology and conditions usedare good tools for evaluating the bioavailability of lipids elaboratedwith modified fats. Furthermore, it proves the suitability ofC18:3n3 as a biomarker. Our results show that a higher meltingpoint could delay lipid absorption at the beginning, but that ithas no effect on total lipids absorbed. Finally, the results of thisstudy suggest that modifying the melting profiles of fat blends

Fig. 5. Area under the C18:3n3 plasma concentration time curve (AUC) after interesterified (IE), non-interesterified (nIE) and control sample administration.

576 M. Farfán et al. / Food Chemistry 139 (2013) 571–577

through interesterification, without altering the bioavailabilitydetermined by sn-2 stereochemistry, while maintaining the FAprofile, does not alter the bioavailability of such fats. Enzymaticinteresterification has proved to be instrumental to achieve thismodification in fats and, thus, as an effective tool to introduceessential FA that could be absorbed in the same way. We believethat the interesterified blend might be used in food emulsions,which is the focus of our ongoing research.

Acknowledgements

The authors would like to acknowledge the Pontificia Universi-dad Católica de Chile’s Central Nursery and Department of Physio-logical Sciences (Faculty of Biological Sciences) and the financialsupport provided by the institution’s VRI.

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