jurnal mutu pangan

ORIGINAL ARTICLE

Employment of Differential Scanning Calorimetry in DetectingLard Adulteration in Virgin Coconut Oil

T. S. T. Mansor Y. B. Che Man M. Shuhaimi

Received: 30 March 2011 / Revised: 24 August 2011 / Accepted: 25 August 2011 / Published online: 22 September 2011

AOCS 2011

Abstract Lard (LD) has been commonly used as an

adulterant in fats and oils. The similar physical character-

istic of virgin coconut oil (VCO) to LD makes LD a desir-

able adulterant in VCO. Differential scanning calorimetry

(DSC) provides unique thermal profiling for each oil and

can be used to detect LD adulteration in VCO. In the heating

thermogram of the mixture, there was one major endo-

thermic peak (peak A) with a smaller shoulder peak

embedded in the major peak that gradually smoothed out to

the major peak as the LD% increased. In the cooling ther-

mogram, there were one minor peak (peak B) and two major

exothermic peaks, peak C which increased as LD%

increased and peak D which decreased in size as the LD%

increased. From Stepwise Multiple Linear regression

(SMLR) analysis, two independent variables were found to

be able to predict LD% adulteration in VCO with R2

(adjusted) of 95.82. The SMLR equation of LD% adulte-

ration in VCO is 293.1 - 11.36 (Te A) - 2.17 (Tr D); where

Te A is the endset of peak A and Tr D is the range of thermal

transition for peak D. These parameters can serve as a good

measurement index in detecting LD adulteration in VCO.

Keywords Virgin coconut oil Lard Adulteration Differential scanning calorimetry Stepwise multiplelinear regression

Introduction

Thermal analysis (TA) is one of the main methods of

analysis in food studies and industries. TA was first

developed in 1887 and has ever since applied for qualita-

tive and quantitative analyses ranging from the studies in

pharmaceutical, polymers, minerals, biological sciences,

ceramics, food and metals [1]. The TA techniques include

differential thermal analysis (DTA), thermogravimetric

analysis (TGA), dielectric thermal analysis (DEA), ther-

momechanical analysis (TMA) and differential scanning

calorimetry (DSC). DSC is in fact, one the most common

TA techniques applied in food analysis [2].

DSC is one of the TA methods that apply the principle of

heat difference of a sample by thermo-physical transitions,

i.e. exothermic and endothermic changes. When a sample is

heated or cooled, it goes through phase transitions from

solid to liquid and liquid to solid in which heat is either

absorbed (endothermic) or released (exothermic). In the

study of fats and oils, DSC is not only capable of deter-

mining the crystallization and the melting behavior, but it

has the sensitivity to detect polymorphism where more than

one crystalline structure exists in a given substance [3].

In addition, DSC does not require the use of excessive

amounts of chemicals and reagents and is an indispensable

tool for understanding the physicochemical properties and

decomposition of fats and oil [4]. In line with diverse

choice of phase change studies, DSC is also applicable to

monitoring thermo-oxidative decomposition [5] as well as

for detecting adulterations in fats and oils [69].

T. S. T. Mansor Y. B. Che Man (&) M. ShuhaimiHalal Products Research Institute, Universiti Putra Malaysia,

43400 Serdang, Selangor, Malaysia

e-mail: [email protected]

Y. B. Che Man

Department of Food Technology,

Faculty of Food Science and Technology,

Universiti Putra Malaysia, 43400

Serdang, Selangor D.E., Malaysia

M. Shuhaimi

Faculty of Biotechnology and Biomolecular Sciences,

Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia

123

J Am Oil Chem Soc (2012) 89:485496

DOI 10.1007/s11746-011-1936-3

In the Muslim and Jewish societies, major concern lies

in detecting unlawful materials, especially pork and lard in

the food. This has gained recognized attention globally as

the Muslim and Jewish markets have grown rapidly due to

the increasing awareness of their needs. Therefore, manu-

facturers and producers alike should be sensitive towards

the issue of unlawful things in food product that includes

LD and other pork derivatives [10]. Animal fats including

LD, have been used as adulterants in vegetable oils as well

as being exploited to develop new products [11] in order to

gain economical profits as LD is one of the cheapest fats

available in the market.

The physical characteristics of virgin coconut oil (VCO)

is quite similar to that of lard (LD), being white to cream in

color [12] and are also solid at room temperature of

2225 C. VCO is recognized by its nutraceutical proper-ties, which can act as primary prevention and treatment for

many illnesses relating to atherosclerosis [13]. It has been

postulated as a good antioxidant source and good throm-

bopreventive supplements as reported by Nevin and

Rajamohan in their studies using SpragueDawley rats [14,

15]. Hence, blending of this VCO with LD would generate

more profit, as LD is comparatively cheaper than VCO. The

objective of this study is to apply DSC and chemometrics to

detect the presence of LD in VCO. In addition, fatty acid

(FA) and triacylglycerol (TAG) analyses were performed by

gas chromatographyflame ionization detector (GCFID)

and high performance liquid chromatography (HPLC),

respectively. The use of GCFID and HPLC managed to

detect the presence of LD in VCO, however, they are

both complex and laborious. In contrast, DSC offers a less

hazardous technique and able to provide qualitative and

quantitative analysis to detect LD adulteration in VCO.

Materials and Methods

VCO was prepared by the fermentation method described

by Che Man et al. [16] with some modifications and

without the use of a pure bacterial culture. Endosperm of

mature coconut was obtained from a local market in

Selangor, Malaysia and grated. It was made into a viscous

slurry with 1:1 coconut meat:water ratio (w/v) and subse-

quently squeezed through cheesecloth to obtain its milk.

The coconut milk was left for 48 h at 35 C for the naturalfermentation process that helps to destabilize the coconut

milk emulsion. The oil obtained was subsequently sieved

through Whatman filter paper No 1 and kept in a refrig-

erator (-4 C) until further use.LD was prepared from rendering the adipose tissues of

pigs according to the method performed by Syahariza et al.

[17]. Adipose tissues from various parts of slaughtered pigs

was rendered and then filtered. The LD obtained was

placed into a container, flushed with nitrogen and stored

until further use. The chemicals and solvents used were of

analytical grade, unless otherwise specified. TAG standards

were purchased from Sigma Aldrich (St. Louis, MO, USA).

Preparation of Blends

Mixtures of VCO and lard were prepared according to

percentage of lard in VCO (v/v). The blends of 1, 2, 3, 5,

7.5, 10, 20 and 30% LD in VCO were prepared in

triplicate.

Chemical Analysis

Saponification values (SV) were performed on sample

admixtures according to the AOAC official method [18].

Ethanolic potassium hydroxide (0.5 N) were added to the

samples and the mixtures were brought to the boil in a

reflux condenser for about 60 min. After cooling, the

mixtures were titrated with 0.5 N HCl. All determinations

were carried out in triplicate.

Fatty Acid Compositional Analysis

The FA composition was performed using gas chroma-

tography with a flame ionization detector (GCFID)

(Agilent 6890 N Network GC system). Prior to GC anal-

ysis, the sample admixtures were trans-esterified using

sodium methoxide. Samples were mixed with hexane

(0.8 ml) and sodium methoxide (1 M, 0.2 ml). It was

subsequently vortexed for 5 s and the supernatant collected

and stored at -4 C until further use.The fatty acid methyl ester (FAME) analysis was con-

ducted according to the method described by Nor Hayati

et al. [9]. A 1-ll sample was injected by the Agilent 7683BSeries Injector into the GCFID. Helium 99.95% was the

carrier gas used at a flow setting of 6.8 ml/min. The oven

temperature was initiated at 50 C and held for 1 min, thenit was increased to 180 C (8 C/min) and held for another2 min, and subsequently increased to the set point of 200 C(5 C/min) and held for 5 min. Analyses were carried out intriplicate and presented as means and standard deviations.

Triacylglycerol Compositional Analysis by HPLC

TAG analysis was performed using reverse-phase HPLC

(Waters, Milford, MA) coupled with a Waters refractive

index detector. Oil samples were diluted in acetone (1:9 v/v)

and isocratically eluted with acetone:acetonitrile (63.5:36.5

v/v) as the mobile phase. The column used in this study was

a LiChroCART 100-RP-18 (5 lm 9 12.5 cm 9 4 mm i.d.;Merck, Darmstadt). For each analysis, 10-ll sampleswere injected. TAG peaks were analyzed by the Empower

486 J Am Oil Chem Soc (2012) 89:485496

123

software (Milford, MA) and identified based on the reten-

tion time of TAG standards, which were then presented as

percentage areas.

Thermal Analysis by DSC

Approximately 9 mg of each oil sample was weighed into

an aluminum pan and sealed into place. Thermal analyses

were performed using a DSC 823e Mettler Toledo instru-

ment equipped with a sample robot (Julabo FT400

intracooler) and STARe excellence software for data

interpretation. The instrument was calibrated with indium

and n-dodecane. The reference used was an empty covered

aluminum pan of the same size as used in the samples.

Samples were subjected to the following programmed

temperature ramp: 60 C isotherm for 5 min, cooled at5 C/min to -60 C and held for 5 min. It was subse-quently heated from -60 to 60 C at 5 C/min. The scan-ning rate was programmed at 5 C/min to reduce the lag inoutput response from the DSC instrument as well as to

preserve the minor peaks and to reduce the peak smoothing

tendencies, which can occur at a high scanning rate. The

thermal characteristics that were determined in our study

are the melting and cooling transition temperatures (mea-

sured from the DSC curve as the maximum peak tempera-

ture), the onset (To) and endset (Te) temperatures (measured

as the point where extrapolation of the leading and ending

curve edge intersects with the baseline) and the temperature

range for cooling and melting phase (Tr) (determined from

the differences between the onset and endset temperatures).

Statistical Analysis

All experiments were carried out in triplicate and analyzed

using one-way analysis of variance (ANOVA) using the

Minitab version 14 (Minitab Inc., State College, PA, USA).

Tukeys test was utilized to ascertain the significant differ-

ences among means at the level of p \ 0.05. DSC data werefurther evaluated by the stepwise multiple linear regression

model using Minitab version 14 (Minitab Inc., State College,

PA, USA). The significant difference of the independent

variables was set at 0.05 for the entry and stay of the calibration

model. R-square (R2) (adjusted) were chosen for this study to

reduce the chance variation of predictors given by the R2.

Results and Discussion

Chemical Analysis

The SV of pure VCO was 251.44 mg KOH/g while LD has

a SV of 190.55 mg KOH/g. Both SV conform to the

standards given by Asian and Pacific Coconut Community

[19] and Codex Alimentarius Commission [12], for VCO

and LD, respectively. The SV refers to the weight in mg of

potassium hydroxide required to saponify 1 g of fats. This

value also relates to the mean molecular mass of the fats

and oils through an inverse relationship because the longer

the FA chain, the higher mean molecular mass is and

therefore the lower SV it would be.

LD has a lower SV as compared to VCO because LD

contains large amounts of long chain FA, mostly palmitic

and stearic. In contrast, VCO has a high SV because it con-

tains large amounts of lauric and myristic acid. The SV for

the admixtures used in this study are presented in Table 1.

Fatty Acid Compositional Analysis

VCO is known as a medium chain oil because of the high

content of medium chain fatty acids. It contains predomi-

nantly lauric acid (C12:0) and other medium chain FA such

as capric and caproic acids as presented in Table 2. The

content of lauric acid in VCO is 48.47 0.02% of the total

FA. The bulk of FA are mostly of medium chain FA

(containing 612 carbons), which is approximately 63.85%

of the total FA. The rest of FA are long chain FA (36.15%)

and there were only minor presence of monounsaturated

and polyunsaturated fats (6.15%).

In contrast to VCO, LD contains more long chain FA

and higher proportions of monounsaturated (41.36%) and

polyunsaturated FA (18.33%). As the LD concentration

increases in the sample admixtures, the proportion of the

saturated to unsaturated FA decreases. This is in line with

the inherent FA structure of LD, which has high unsatu-

rated FA and lower lauric acids than VCO. The increments

of LD in VCO are reflected in the reduction of lauric acid

and the increase of oleic acid percentage in the mixtures.

Table 1 Saponification value (SV) of virgin coconut oil (VCO)adulterated with lard (LD) (v/v)

Lard concentration (%) SV (mg KOH/g oil)

0 251.44 1.56a

1 247.92 2.12a,b

2 246.38 1.06b,c

3 243.64 2.36c,d

5 242.85 0.84c,d,e

7.5 241.26 1.26d,e,f

10 239.59 1.77d,e,f,g

15 234.62 0.84h

20 229.75 1.15i

30 222.09 0.68j

100 190.55 1.25k

Each value in the table represents the mean standard deviation of

triplicate analyses and means within each column with different

superscript letters are statistically significant at p \ 0.05

J Am Oil Chem Soc (2012) 89:485496 487

123

TAG Analysis by Reverse-Phase HPLC

Oil and fats are mostly composed of TAG and FA, with

small amounts of free fatty acids. TAG is the essence of oil

and fats, which correlates to the cooling and melting

behavior seen in thermal analysis. Table 3 shows the TAG

profiles of pure VCO, LD and admixtures between them.

VCO had high percentage of LaLaLa (La:Lauric), which

Table 2 Composition of fatty acids (FAs) in virgin coconut oil (VCO) adulterated with different concentration of lard (LD) (v/v)

Lard

concentration (%)

Fatty acids

C6 C8 C10 C12 C14 C16

0 0.68 0.00a 8.20 0.01a 6.50 0.00a 48.47 0.02a 18.25 0.00a 8.77 0.00a

1 0.67 0.01a,b 8.30 0.06a,b 6.53 0.04a,b 46.33 0.21b 17.42 0.02b 9.18 0.07a

2 0.59 0.02a,b,e,f 7.39 0.19a,b,c,e,f 6.00 0.09c,f 44.51 0.37b,f 18.39 0.03a,b,f 10.08 0.11f

3 0.67 0.00a,b,e,f,g,h 8.34 0.05a,b,e,f,g,h 6.57 0.05a,b,h 46.56 0.26 h 17.41 0.02b,h 9.13 0.08a,h

5 0.63 0.01a,b,c,e,f,g,h,i,j 7.80 0.05a,b,c,e,f,g,h,i 6.15 0.03c,f,j 43.64 0.17j 16.54 0.01c,j 9.98 0.05f,j

7.5 0.60 0.00a,b,e,f,g,h,i,j 7.61 0.02c 6.06 0.00a,f,j 43.42 0.03j 16.76 0.00c,j 10.21 0.01f,j

10 0.33 0.24c 6.54 1.30a,b,c,e 5.77 0.25c 42.26 0.04c 16.43 0.38c 10.98 0.42c

15 0.54 0.02a,b,c,e 7.01 0.04a,b,c,e 5.58 0.01c,e 39.75 0.09e 15.34 0.02e 11.48 0.01c,e

20 0.52 0.02a,b,c,e,f,g 6.83 0.11a,b,c,e,f,g 5.48 0.08c,e,g 39.10 0.55e,g 15.03 0.10e,g 12.13 0.16g

30 0.46 0.01a,b,c,e,f,g,h,i 5.86 0.04c,e,g,i 4.68 0.03i 33.22 0.16i 13.07 0.03i 13.90 0.04i

100 0.00 0.00d 0.00 0.00d 0.04 0.06d 0.07 0.10d 1.47 0.00d 24.96 0.28d

Lard

concentration

(%)

Fatty acids

C17:0 C18:0 C18:1 C18:2 C18:3 C20:2

0 0.00 0.00a 2.99 0.00a 6.08 0.00a 0.07 0.00a 0.00 0.00a 0.00 0.00a

1 0.00 0.00a,b 2.93 0.07a,b 6.97 0.16a,b 1.66 0.03b 0.00 0.00a,b 0.00 0.00a,b

2 0.00 0.00a,b,f 3.51 0.16f 7.76 0.35b,f 1.78 0.07b,f 0.00 0.00a,b,c,f 0.00 0.00a,b,c

3 0.00 0.00a,b,f,h 2.78 0.09a,b,h 6.82 0.17a,b,h 1.72 0.04b,f,h 0.00 0.00a,b,c,f,h 0.00 0.00a,b,c,d

5 0.00 0.00a,b,f,h,j 3.50 0.07c,f,j 8.98 0.13j 2.78 0.03j 0.00 0.00a,b,c,f,h,j 0.00 0.00a,b,c,d,e

7.5 0.00 0.00a,b,f,h,j 3.76 0.00c,f,j 9.22 0.01j 2.37 0.00k 0.00 0.00a,b,c,f,h,j 0.00 0.00a,b,c,d,e,f

10 0.08 0.01c 3.94 0.12c 10.46 0.56c 3.14 0.16c 0.06 0.00a,b,c 0.04 0.08a,b,c,d,e,f,g

15 0.11 0.00e 4.33 0.02e 11.86 0.04e 3.82 0.01e 0.13 0.00e 0.05 0.09a,b,c,d,e,f,g,h

20 0.13 0.00g 4.23 0.17c,e,g 12.19 0.46e,g 4.15 0.14g 0.15 0.00e,g 0.06 0.08a,b,c,d,e,f,g,h,i

30 0.19 0.00i 5.63 0.06i 16.50 0.16i 6.06 0.06i 0.24 0.00i 0.19 0.11a,b,c,d,e,f,g,h,i,j

100 0.64 0.00d 13.13 0.17d 41.36 0.54d 17.08 0.18d 0.80 0.05d 0.44 0.62a,b,c,d,e,f,g,h,i,j,k

FA Lard concentration (%)

0 1 2 3 5

SFA 93.85 0.00a 91.37 0.19b 90.47 0.43a,c 91.46 0.21b,c,d 88.42 0.16e

MUFA 6.08 0.00a 6.97 0.16a,b 7.76 0.35b,c 6.82 0.17a,b,d 9.22 0.13e

PUFA 0.07 0.00a 1.66 0.04b 1.78 0.07b,c 1.72 0.04b,c,d 2.37 0.03e

Lard concentration (%)

FA 7.5 10 15 20 30 100

SFA 88.24 0.01e,f 86.31 0.82g 84.14 0.13h 83.45 0.52h.i 77.01 0.17j 40.31 0.06k

MUFA 8.98 0.01e,f 10.46 0.56g 11.86 0.04h 12.19 0.46h.i 16.50 0.16j 41.36 0.54k

PUFA 2.78 0.00e,f 3.24 0.26f,g 4.00 0.10h 4.36 0.07h.i 6.49 0.08j 18.33 0.49k

Each value in the table represents the mean standard deviation of triplicate analyses and means within each column with different superscript

letters are statistically significant at p \ 0.05C6 caproic acid, C8 caprylic acid, C10 capric acid, C12 lauric acid, C14 myristic acid, C16 palmitic acid, C18 stearic acid, C18:1 oleic acid,C18:2 linoleic acid, C18:3 linolenic acid, C20:2 eicosadienoic acid, SFA saturated fatty acid, MUFA monounsaturated fatty acid, PUFApolyunsaturated fatty acids

488 J Am Oil Chem Soc (2012) 89:485496

123

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a0

.00

0

.00

a0

.00

0

.00

a

PP

O0

.35

0

.01

a0

.36

0

.00

a,b

0.3

8

0.0

0a,b

,c0

.47

0

.00

a,b

,c,d

0.5

2

0.0

0a,b

,c,d

,e

PP

P0

.05

0

.07

a0

.09

0

.00

a0

.08

0

.01

a0

.08

0

.01

a0

.09

0

.00

a

SO

O0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a

SP

O0

.00

0

.00

a0

.14

0

.00

a,b

0.2

1

0.0

0a,b

,c0

.36

0

.00

a,b

,c,d

0.5

6

0.0

0a,b

,c,d

,e

PP

S0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a

SO

S0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a

SS

S8

9.1

9

0.2

4a

88

.98

0

.01

a,b

88

.64

0

.02

a,b

,c8

8.2

9

0.1

0a,b

,c,d

87

.57

0

.01

a,b

,c,d

,e

SS

U7

.21

0

.01

a7

.23

0

.02

a,b

7.3

0

0.0

4a,b

,c7

.60

0

.02

a,b

,c,d

7.9

7

0.0

1a,b

,c,d

,e

SU

U0

.71

0

.24

a0

.95

0

.00

a,b

1.0

4

0.0

0a,b

,c1

.26

0

.02

a,b

,c,d

1.7

8

0.0

0a,b

,c,d

,e

Oth

ers

2.9

0

0.0

0a

2.8

5

0.0

1a,b

3.0

2

0.0

2a,b

,c2

.86

0

.10

a,b

,c,d

2.6

8

0.0

2a,b

,c,d

,e

J Am Oil Chem Soc (2012) 89:485496 489

123

Ta

ble

3co

nti

nu

ed

Tri

acy

lgly

cero

lL

ard

con

cen

trat

ion

(%)

7.5

10

15

20

30

10

0

Cp

Cp

La

1.9

3

0.0

5b,c

,d,f

2.1

9

0.0

3e,f

,g1

.86

0

.05

b,c

,d,f

,h1

.73

0

.04

a,b

,c,d

,f,h

,i1

.36

0

.03

a,j

0.0

0

0.0

0k

Cp

CL

a3

.76

0

.03

a,b

3.9

2

0.2

2a,b

3.7

6

0.2

1a,b

,c3

.47

0

.10

a,c

,d3

.04

0

.00

e0

.00

0

.00

f

CC

La

11

.44

0

.03

b,c

,d,e

,f1

1.7

9

0.8

4a,b

,c,d

,e,f

,g1

1.2

3

0.7

4c,e

,f,g

,h1

1.3

1

0.0

5c,d

,e,f

,g,h

,i1

0.0

9

0.0

1h,i

,j0

.00

0

.00

k

CL

aLa

15

.23

0

.01

c,d

,e,f

15

.57

1

.03

a,b

,c,d

,e,f

,g1

5.0

8

0.9

1e,f

,g,h

14

.97

0

.00

e,f

,g,h

,i1

3.7

1

0.0

2f,

h,i

,j0

.00

0

.00

k

LaL

aLa

19

.06

0

.01

f1

9.4

1

1.1

2c,e

,f,g

18

.91

0

.97

f,g,h

18

.49

0

.02

f,g,h

,i1

7.0

5

0.0

0i,

j0

.00

0

.00

k

LaL

aM1

4.7

1

0.0

1f

14

.61

0

.32

c,e

,f,g

14

.30

0

.25

f,g,h

13

.89

0

.03

f,g,h

,i1

2.7

1

0.0

0i,

j0

.00

0

.00

k

LaL

aO3

.55

0

.01

a3

.04

0

.80

a2

.88

0

.72

a2

.29

0

.03

a2

.11

0

.00

a0

.00

0

.00

b

LaM

M9

.18

0

.00

b,c

,d,e

,f9

.00

0

.04

a,b

,c,d

,e,f

,g8

.78

0

.01

c,e

,f,g

,h8

.47

0

.04

c,d

,e,f

,g,h

,i7

.82

0

.00

h,i

,j0

.00

0

.00

k

LL

L0

.81

0

.00

a0

.55

0

.48

a0

.52

0

.42

a0

.24

0

.00

a0

.27

0

.00

a0

.59

0

.02

b

MM

M0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a1

.71

0

.01

b

OM

L?

LP

L0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a4

.47

0

.01

b

LaM

O2

.72

0

.01

a2

.34

0

.60

a2

.18

0

.53

a1

.72

0

.02

a1

.56

0

.01

a0

.00

0

.00

b

LaM

P5

.19

0

.01

a4

.99

0

.23

a,b

4.9

1

0.2

1a,b

,c4

.68

0

.04

b,c

,d4

.51

0

.02

d,e

0.0

0

0.0

0f

LaO

O0

.86

0

.00

a,b

0.7

1

0.2

5a,b

0.9

7

0.2

9a,b

0.7

9

0.0

2a,b

0.6

5

0.0

0a,b

0.0

0

0.0

0a,c

LaP

O1

.61

0

.00

a1

.45

0

.31

a1

.47

0

.43

a1

.27

0

.01

a1

.23

0

.00

a0

.00

0

.00

b

LaP

P?

MM

O2

.11

0

.00

b1

.93

0

.23

a,b

,c1

.83

0

.17

a,b

,c1

.65

0

.00

a,b

,c1

.54

0

.00

a,b

,c0

.00

0

.00

d

OO

L0

.55

0

.01

b0

.47

0

.19

b,c

0.6

2

0.1

6b,c

0.6

5

0.0

8b,c

1.1

3

0.0

2d

4.5

5

0.1

4e

PP

L0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a1

8.5

3

0.0

1b

MM

P?

LP

O1

.89

0

.00

b1

.89

0

.35

b,c

2.5

2

0.2

2d

3.1

0

0.0

1e

4.6

6

0.0

0f

8.4

5

3.2

6g

MP

O?

PO

L1

.29

0

.00

f0

.98

0

.23

a,c

,f,g

1.1

6

0.2

3c,f

,g,h

1.0

9

0.0

1c,f

,g,h

,i1

.31

0

.00

f,g,h

,i,j

0.0

0

0.0

0k

LP

P?

OO

O0

.00

0

.00

a,b

,c,d

0.0

0

0.0

0a,b

,c,d

,e0

.00

0

.00

a,b

,c,d

,e,f

0.9

6

0.0

0b,d

,e,f

,g1

.46

0

.01

h5

.63

0

.19

i

PO

O/O

PO

1.8

2

0.0

1d,e

,f2

.26

0

.06

e,f

,g3

.23

0

.13

g,h

4.6

3

0.0

3i

6.9

2

0.0

1j

26

.03

0

.98

k

SO

L0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a5

.24

0

.10

b

PP

O0

.63

0

.00

b,c

,d,e

,f0

.75

0

.06

e,f

,g0

.85

0

.06

f,g,h

1.1

3

0.0

1i

1.5

3

0.0

1j

5.0

2

0.2

2k

PP

P0

.10

0

.01

a0

.12

0

.02

a0

.13

0

.01

a0

.16

0

.00

a0

.25

0

.00

b,c

0.5

3

0.0

1d

SO

O0

.00

0

.00

a0

.21

0

.03

b0

.44

0

.04

c0

.70

0

.01

d1

.08

0

.01

e4

.42

0

.16

f

SP

O0

.80

0

.00

b,c

,d,e

,f1

.13

0

.11

e,f

,g1

.70

0

.14

g,h

2.6

0

0.0

3i

3.8

7

0.0

0j

15

.07

0

.55

k

PP

S0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

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a0

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0

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.78

0

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c

SO

S0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a0

.00

0

.00

a1

.09

0

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b

SS

S8

3.2

8

0.0

5e,f

82

.15

2

.90

f,g

79

.48

2

.52

f,g,h

77

.42

0

.06

h,i

70

.96

0

.04

j2

0.4

3

0.7

3k

SS

U9

.31

0

.02

a,b

,c,d

,e,f

8.7

1

1.5

5a,b

,c,d

,e,f

,g9

.08

1

.48

a,b

,c,d

,e,f

,g,h

9.0

0

0.0

8a,b

,c,d

,e,f

,g,h

,i1

0.2

9

0.0

3d,e

,f,g

,h,i

,j2

6.4

2

0.9

1k

SU

U3

.23

0

.02

e,f

3.6

6

0.3

5f,

g5

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0

.28

g,h

6.7

8

0.0

1h

9.7

8

0.0

0i

34

.99

1

.28

j

Oth

ers

4.1

9

0.0

1a,b

,c,d

,e,f

5.4

8

1.0

0a,b

,c,d

,e,f

,g6

.17

0

.77

a,b

,c,d

,e,f

,g,h

6.8

1

0.0

1c,f

,g,h

,i8

.97

0

.01

g,h

,i,j

18

.17

2

.92

k

Eac

hv

alu

ein

the

tab

lere

pre

sen

tsth

em

ean

st

and

ard

dev

iati

on

of

du

pli

cate

anal

yse

san

dm

ean

sw

ith

inea

chco

lum

nw

ith

dif

fere

nt

sup

ersc

rip

tle

tter

sar

est

atis

tica

lly

sig

nifi

can

tat

p\

0.0

5

Cp

cap

roic

,C

cap

ric,

La

lau

ric

Mm

yri

stic

,O

ole

ic,

Lli

no

leic

,P

pal

mit

ic,

La

lau

ric,

Lli

no

leic

,P

pal

mit

ic,

Mm

yri

stic

,O

ole

ic,

Sst

eari

c,S

SS

tris

atu

rate

dtr

iacy

lgly

cero

l,S

SU

mo

no

un

satu

rate

dtr

iacy

lgly

cero

l,S

UU

diu

nsa

tura

ted

trig

lyce

rol

490 J Am Oil Chem Soc (2012) 89:485496

123

was 21.43 0.05% of the total TAG. Marina et al. [20]

also reported LaLaLa as the most predominant TAG in

VCO with values ranging from 22.78 to 25.84%, slightly

higher than the value obtained in this study. This could be

attributed to the different method of extractions, the ripe-

ness, the cultivar type, growing condition and the origin of

the coconut. As expected, the values of LaLaLa drops as

the LD% adulteration increases. All TAG that had lauric

acid as one of the FA in the backbone such as CpCpLa,

CpCLa, CLaLa, LaLaM, LaLaO or LaMM all decreased in

percentage as the adulteration increased.

OPO/POO and SPO are two TAG that showed a sig-

nificant increase as LD% adulteration increased. LD is

quite unique in that it has a high predominance of saturated

FA especially palmitic acid at the sn-2 position, unlike

most other oils and fats [21]. The presence of palmitic acid

at the sn-2 position increases the risk of developing ath-

erosclerosis, as it contributes to an increase in fat absorp-

tion and delays chylomicron clearance from the blood

vessels [22]. However, the traditional chromatographic

TAG analysis alone would not be able to distinguish reg-

ioisomerism in fats and oils, in which there are positional

varieties of FA on the glycerol backbone of TAG such as

that seen in OPO/POO, SOO/OSO and PPO/POP. To

identify specific regioisomers in TAG would therefore

require prior analysis such as enzymatic hydrolysis or more

advanced chromatographic analysis [21]. This is particu-

larly seen for OPO/POO TAG in our analysis, as VCO also

contain POO at 0.34%. Although OPO/OOP TAG increa-

ses with increments of LD in VCO, further analysis should

be performed to ensure this TAG is OPO of LD.

The TAG analysis would therefore compliment the

thermal study of VCO in detecting LD adulterations. This

is due to the fact that thermal behavior of fats and oils are

caused by TAG. Indeed, the variety of TAG present in oil

and fats causes the melting and cooling phase to occur over

a temperature span. For these reasons, it should be worthy

to discuss TAG and DSC analysis concurrently.

Thermal Analysis by DSC

Heating Thermogram

VCO and LD contain different amounts of saturated and

unsaturated TAG and FA, although the physical properties

are almost similar. The saturated to unsaturated FA ratio in

VCO from the FA analysis is 15.26 as compared to 0.67 in

LD. TAG is unique because the wide range of TAG

arrangements and saturation levels lead to the development

of multiple endothermic and exothermic peaks seen in the

DSC curves. The more saturated the TAG, the higher the

melting temperature will be and the less saturated the TAG,

the lower the melting temperature. The oils containing

more saturated FA and TAG would have higher melting

points, which is evident from our study where the VCOs

melting temperature is 23.16 C and it shows two over-lapping endothermic peaks. There is a smaller shoulder

peak embedded in the major endothermic peak caused by

the difference in the content of saturated and unsaturated

TAG and FA in the VCO. The smaller shoulder peak

corresponds to the lower melting fraction of the VCO (the

unsaturated TAG and FA) and the bigger major peak cor-

responds to the higher melting fractions (the saturated TAG

and FA). In turn, as LD contains more unsaturated FA and

TAG, therefore, it contributes to the development of a

lower melting point, seen at -3.93 and 18.83 C (Fig. 1) astwo major endothermic peaks.

In LD, the first major peak at -3.93 C is due mostly tothe unsaturated TAG and FA (ratios of unsaturated to sat-

urated are 61.41:20.43 and 59.69:40.31 for TAG and FA,

respectively) and the second peak is caused mostly by the

saturated TAG and FA. Due to the higher ratio of

Fig. 1 Differential scanningcalorimetry (DSC) heating

thermogram of pure virgin

coconut oil (VCO) and pure

lard (LD)

J Am Oil Chem Soc (2012) 89:485496 491

123

unsaturated FA and TAG in LD, the first major peak is seen

to be bigger than the second endothermic peak. Marikkar

et al. [7] reported another minor endothermic peak at

-17.2 C, which was observed as a peak broadening thatstarts at sub-zero temperatures in our study, corresponding

to the minor peak found in genuine LD studied by Marikkar

et al. [7]. This phenomenon could be related to the use of a

different DSC model and different sample preparations.

As LD was successively added to VCO from a zero to a

30% concentration, the melting thermogram showed one

major endothermic peak with a smaller shoulder peak

embedded in the major peak. This major peak was called

peak A and is shown in Fig. 2. As explained by Tan et al.

[23, 24], the presence of the inseparable shoulder peak is

due to the complex nature of TAG that can melt over the

same temperature range and the presence of a smaller or

shoulder peak is due to differing type of TAG. The more

saturated the TAG is, the higher the melting point and vice

versa. Qualitatively, there was gradual smoothing of the

shoulder peaks which was obvious at the level of 20% LD

adulteration. In addition, the To and the Te of peak A slid

down to a lower temperature transition from the pure VCO

with increasing LD, as evident from Table 4. The melting

enthalpy for VCO, taken from the measurement of the area

under the peaks in the melting curve was 110.53 4.18 J/g,

which decreases as the LD% increases. This is in agreement

with the high saturation in VCO that renders a higher melting

enthalpy than LD.

It was deduced here that the peak at higher temperatures

belongs to the multiple TAG that are more saturated and

hence the higher melting temperature. It is known that

multiple TAG can melt at the same temperature range

simultaneously, leading to the formation of a single broad

peak. However, it is impossible to determine which specific

TAG contributes to the specific peak by DSC alone in the

fats and oil system as they are composed of mixtures of

TAG that melt or crystallize over the same temperature

range. Further evaluation should be made using X-ray

Fig. 2 Differential scanningcalorimetry (DSC) heating

thermogram of virgin coconut

oil (VCO) adulterated with

lard (LD) (v/v)

Table 4 Differential scanning calorimetry (DSC) heating thermogram peak maxima (max T peak A), onset (To A), endset (Te A) and range ofthermal transition (Tr A) of virgin coconut oil (VCO) adulterated with lard (LD) (v/v)

% Lard To A Max T peak A Te A Tr A

0 10.27 1.77a 23.16 0.10a 25.10 0.13a 14.89 1.68a

1 9.23 0.12a,b 23.03 0.20a,b 25.15 0.13a,b 15.92 0.03a,b

2 9.06 0.05a,b,c 22.91 0.23a,b,c 25.11 0.20a,b,c 16.05 0.15a,b,c

3 8.42 0.31a,b,c,d 22.65 0.18a,b,c,d 24.88 0.07a,b,c,d 16.46 0.26a,b,c,d

5 8.42 0.11a,b,c,d,e 22.64 0.05a,b,c,d,e 24.81 0.02a,b,c,d,e 16.29 0.17a,b,c,d,e

7.5 8.19 0.54a,b,c,d,e,f 22.13 0.54a,b,c,d,e,f 24.62 0.19,d,e,f 16.43 0.35a,b,c,d,e,f

10 9.26 2.98a,b,c,d,e,f,g 21.66 0.13c,d,e,f,g 24.20 0.03f,g 14.94 3.01a,b,c,d,e,f,g

15 10.00 2.34a,b,c,d,e,f,g,h 21.09 0.93f,g,h 24.05 0.28g,h 14.05 2.48a,b,c,d,e,f,g,h

20 8.96 2.50a,b,c,d,e,f,g,h,i 19.87 0.36h,i 23.30 0.13i 14.34 2.36a,b,c,d,e,f,g,h,i

30 7.92 1.77a,b,c,d,e,f,g,h,i,j 18.93 0.84i,j 22.91 0.16i,j 14.99 1.93a,b,c,d,e,f,g,h,i,j


letters are statistically significant at p \ 0.05Max T peak max temperature of the peak, To peak onset, Te peak endset, Tr range of thermal transition

492 J Am Oil Chem Soc (2012) 89:485496

123

diffraction, neutron diffraction, or other techniques that

would gather the structural information [6].

DSC was able to perform a qualitative analysis towards

detecting the presence of LD adulteration as we can see

that when VCO is successively adulterated with LD from 1

to 30%, the endothermic max T peak A was gradually

formed at lower temperatures as the LD concentration

increases (Fig. 2; Table 4). The temperature at the com-

pletion of heating phase (Te) also decreased as VCO is

increasingly adulterated with LD. Other changes that were

observed are the smoothing effect of the small shoulder

peak on VCO as the LD increased.

Cooling Thermogram

The DSC cooling thermograms for pure VCO and pure LD

are shown in Fig. 3. There is one minor exothermic peak at

-18.95 C followed by two distinct but overlapping majorexothermic peaks that were observed in VCO at 3.95 and

-2.14 C, slightly higher than those reported by Marinaet al. [25]. This can be attributed to the different nature of

preparation of the VCO, the growing condition of the

coconut, the cultivar type and the maturity of the coconut.

The existence of the two major exothermic peaks in VCO

is related to crystallization of the TAG [25]. The small

Fig. 3 Differential scanningcalorimetry (DSC) cooling

thermograms of pure virgin

coconut oil (VCO) and pure

lard (LD)

Fig. 4 Differential scanningcalorimetry (DSC) coolingthermogram of virgin coconut

oil (VCO) adulterated with lard

(LD) (v/v)

J Am Oil Chem Soc (2012) 89:485496 493

123

exothermic peaks could be related to the unsaturated TAG,

in particular, the PPO and POO/OPO as exothermic peak at

-18.95 C in VCO corresponds to the first major peak seenin pure LD at -16.13 C. According to the TAG analysis(Table 3), only PPO and POO/OPO TAG existed in both

oils, which can explain the small peak in VCO due to the

small amount of PPO and POO/OPO TAG and vice versa

for the major first peak and the amount of the same TAG in

LD. Nevertheless, the presence of first major peak in LD is

not representative of these two TAG only. It represents the

wide variety of TAG in LD that are mostly unsaturated

since the level of saturation reflects the temperature at

which these TAG crystallize. While the TAG within VCO

is abundant with differing combinations of medium FA

(lauric acid and myristic acid), short chain FA and long

chain FA that differs in terms of its molecular mass, hence

the widely distributed major two exothermic peaks are seen

in Fig. 3.

In contrast, LD has two major exothermic peaks

observed at 8.84 and -16.13 C. These two peaks are wellseparated as compared to the major exothermic peaks in

VCO and that the phase transition has a wider temperature

range than VCO. This is contributed to by the different

crystallization profile of each specific group of FA and

TAGthe unsaturated FA and TAG crystallize at lower

temperature and the saturated FA and TAG crystallize at

higher temperatures. Based on the study by Fasina et al.

[26], the FA composition of fats and oils correlates well

with their thermal behavior. This can be explored as a basis

of using FA composition and heating and cooling profiles

Table 5 Differential scanning calorimetry (DSC) cooling thermogram peak maxima (max T peak B), onset (To B), endset (Te B) and range ofthermal transition (Tr B) of virgin coconut oil (VCO) adulterated with lard (LD) (v/v)

Lard (%) To B Max T peak B Te B Tr B

0 -18.05 1.85a -18.95 2.33a -19.64 2.45a 1.58 1.15a

1 -18.29 4.32a,b -18.52 4.01a,b -19.19 4.02a,b 0.90 0.01a,b

2 -18.37 2.04a,b,c -18.53 2.05a,b,c -19.29 2.00a,b,c 0.92 0.04a,b,c

3 -18.39 0.94a,b,c,d -18.72 0.93a,b,c,d -19.49 1.07a,b,c,d 1.10 0.21a,b,c,d

5 -18.21 4.02a,b,c,d,e -18.44 4.12a,b,c,d,e -18.97 4.02a,b,c,d,e 0.76 0.25a,b,c,d,e

7.5 -18.43 7.65a,b,c,d,e,f -19.00 7.64a,b,c,d,e,f -20.76 7.02a,b,c,d,e,f 2.33 1.22a,b,c,d,e,f

10 -20.76 4.07a,b,c,d,e,f,g -21.18 3.90a,b,c,d,e,f,g -21.86 4.08a,b,c,d,e,f,g 1.09 0.20a,b,c,d,e,f,g,h

15 -21.21 4.42a,b,c,d,e,f,g,h -21.70 4.96a,b,c,d,e,f,g,h -22.50 5.27a,b,c,d,e,f,g,h 1.28 0.85a,b,c,d,e,f,g,h

20 -24.36 3.94a,b,c,d,e,f,g,h,i -24.55 3.93a,b,c,d,e,f,g,h,i -25.19 3.99a,b,c,d,e,f,g,h,i 0.83 0.07a,b,c,d,e,f,g,h,i

30 -13.29 2.75a,b,c,d,e,f,g,h,i,j -15.41 2.92a,b,c,d,e,f,g,h,i,j -16.14 3.05a,b,c,d,e,f,g,h,i,j 2.85 1.59a,b,c,d,e,f,g,h,i,j



Table 6 Differential scanning calorimetry (DSC) cooling thermogram peak maxima (max T peak C), onset (To C), endset (Te C) and range ofthermal transition (Tr C) of virgin coconut oil (VCO) adulterated with lard (LD) (v/v)

Lard (%) To C Max T peak C Te C Tr C

0 -0.09 0.25a -2.14 0.11a -4.39 0.26a 4.30 0.01a

1 -0.46 0.16a,b -2.23 0.11a,b -4.45 0.14a,b 4.09 0.06a,b

2 -0.44 0.02a,b,c -2.36 0.06a,b,c -4.71 0.07a,b,c 4.27 0.06a,b,c

3 -0.63 0.75a,b,c,d -2.94 0.32d -5.36 0.28d 4.74 0.49a,b,c,d

5 -0.54 0.67 s,b,c,d,e -2.91 0.23d,e -5.36 0.13d,e 4.83 0.62a,c,d,e

7.5 -0.32 0.14b,c,d,e,f -3.11 0.09d,e,f -5.61 0.09d,e,f 5.29 0.06d,e,f

10 -1.43 0.29b,c,d,e,f,g -3.88 0.10 g -6.38 0.27 g 4.95 0.04a,b,c,d,e,f,g

15 -1.64 0.35b,c,d,e,f,g,h -4.01 0.38 g,h -6.43 0.02 g,h 4.79 0.33a,b,c,d,e,f,g,h,i

20 -1.55 0.75b,c,d,e,f,g,h,i -4.74 0.38i -7.11 0.22i 5.56 0.54d,e,f,g,h,i

30 0.66 0.06a,b,c,e,f,j -2.53 0.17a,b,c,d,e,j -5.76 0.04d,e,f,j 6.42 0.04j



494 J Am Oil Chem Soc (2012) 89:485496

123

for food quality control besides correlating the TAG

composition alone with DSC thermal parameters.

The presence of the small exothermic peaks in VCO at

-18.95 C (peak B) present in all the adulterated VCO. Themaximum peak B temperature stayed around -18 C from 1to 5% LD adulteration and started to decrease as % LD

adulteration increased to 20%. Nonetheless, at 30% LD

adulteration, the max peak B temperature increased back to

-15.41 C. This can be explained by the possibility thatsome of the unsaturated TAG joined the saturated TAG to

form a subsequent major exothermic peak at a higher crys-

tallization temperature, explaining why the adulterant peak

C has a higher crystallization temperature range (Tr peak C).

When LD was added to VCO, the two overlapping

peaks in VCO (assigned as adulterant peak C and D,

respectively) can still be observed with subtle morpho-

logical changes in the thermal curve as the LD concen-

tration increases from 1 to 30%. Figure 4 shows the

adulterant exothermic peak C, which was seen to increase

as the percentage of adulteration increased, while the peak

D reduced in size as the percentage of adulteration

increased. Tables 5, 6 and 7 presents the cooling peak

maxima (Tmax), onset (To), endset (Te) and the range of

thermal transition (Tr) for peak B, C and D. From Table 8,

the cooling enthalpy (taken from the measurement of the

area under the peaks in the cooling curve) for VCO is

-107.11 J/g as compared to LD with -55.02 J/g for LD.

The cooling enthalpy supports their comparative FA and

TAG saturation levels, i.e. VCO has a higher saturation

leading to a larger cooling enthalpy.

Quantitatively, DSC can estimate the percentage of LD

adulteration in VCO using the stepwise multiple linear

regression analysis (SMLR). The data of the temperature

peaks, To, Te and the melting and cooling range (Tr) were

gathered as independent predictors in the SMLR analysis.

The regression models obtained are as follows:

Step (1) % LD adulteration = 295.6 - 11.72 (Te A)

(R2 adjusted = 94.67)

Step (2) % LD adulteration = 293.1 - 11.36 (Te A)

- 2.17 (Tr D) (R2 adjusted = 95.82)

where, (Te A) = endset peak A (Tr D) = temperature

range for peak D

From the above equations, Te A and Tr D were good

predictors for determining LD% adulteration in VCO.

Therefore, both the melting and cooling profiles of VCO

are important in determining the presence of LD

adulteration.

Table 7 Differential scanning calorimetry (DSC) cooling thermogram peak maxima (max T peak D), onset (To D), endset (Te D) and range ofthermal transition (Tr D) of virgin coconut oil (VCO) adulterated with lard (LD) (v/v)

% Lard To D Max T peak D Te D Tr D

0 5.13 0.05a 3.95 0.12a 2.17 0.16a 2.96 0.11a

1 4.50 0.29b 3.28 0.06a,b 1.60 0.07a,b 2.90 0.29a,b

2 4.45 0.02b,c 3.36 0.01a,b,c 1.71 0.04a,b,c 2.74 0.05a,b,c

3 4.37 0.03b,c,d 3.10 0.13b,c,d 1.34 0.12a,b,c,d 3.05 0.45a,b,c,d

5 4.40 0.20b,c,d,e 2.97 0.36b,c,d,e 1.26 0.43b,c,d,e 3.14 0.69a,b,c,d,e

7.5 4.32 0.02b,c,d,e,f 3.16 0.09b,c,d,e,f 1.46 0.12a,b,c,d,e,f 2.86 0.11a,b,c,d,e,f

10 4.17 0.02c,d,e,f,g 2.85 0.26b,c,d,e,f,g 1.01 0.18c,d,e,f,g 3.16 0.19a,b,c,d,e,f,g

15 4.17 0.01c,d,e,f,g,h 2.62 0.61b,d,e,f,g,h 0.69 0.84c,d,e,f,g,h 3.48 0.84a,b,c,d,e,f,g,h

20 3.94 0.02g,h,i 2.81 0.05b,c,d,e,f,g,h,i 0.83 0.15b,c,d,e,f,g,i 3.11 0.17a,b,c,d,e,f,g,h,i

30 3.95 0.04g,h,i,j 3.35 0.02a,b,c,d,e,f,g,h,i,j 2.05 0.05a,b,c,d,e,f,j 1.90 0.02b,c,f,j



Table 8 Cooling and melting partial enthalpy (D) of virgin coconutoil (VCO) adulterated with lard (LD) (v/v)

Lard

concentration

(%)

Cooling enthalpy (J/g) Melting enthalpy (J/g)

0 -107.11 3.04a 110.53 4.18a

1 -106.23 0.89a,b 110.03 0.89a

2 -106.12 0.68a,b,c,e,f 109.66 0.98a,c,d

3 -105.41 2.45a,b,c,e,f,g 109.38 4.69a,b,c,d,e,f

5 -105.49 1.23a,b,c,e,f,g,h,i 109.65 0.90a,b,c,d,e,f,h

7.5 -103.74 1.61a,b,c,e,f,g,h,i 106.92 5.30a,b,c,e,f,g,h

10 -101.91 0.99a,b,c 108.57 1.27a

15 -100.44 2.13a,b,c,e 105.94 3.87a,c

20 -99.18 2.29a,b,c,e,f 104.70 2.09a,c,d,e

30 -97.46 1.02b,c,e,f,g,h 99.64 1.77c,e,g

100 -55.02 8.87d 57.00 1.48b

Each value in the table represents the mean standard deviation of

triplicate analyses and means within each column with different

superscript letters are statistically significant at p \ 0.05

J Am Oil Chem Soc (2012) 89:485496 495

123

Conclusions

This work showed the ability of DSC to detect changes in

the cooling and heating curves of VCO when it is adulter-

ated with LD. Qualitatively, the curves showed subtle

changes such as the size increase of exothermic peak C,

reduction in exothermic peak D and the smoothing effect of

shoulder peak A in the endothermic peak as the percentage

of LD adulteration increased. Through the use of stepwise

multiple linear regression analysis, two independent DSC

parameters were able to predict LD% adulteration in VCO

with an R2 (adjusted) of 95.82. These parameters are the TeA in the endothermic curve and Tr D in the exothermic

curve. Although TAG and FA analysis by the HPLC and

GCFID, respectively, were able to detect LD adulteration

in VCO with high confidence, they did not provide a

qualitative analysis and are restricted by the use of chemi-

cals and the requirement for highly trained personnel to

operate the systems. The Te A in the endothermic curve and

Tr D in the exothermic curve may offer an attractive mea-

surement index for the detection of LD in VCO. In addition,

DSC also offers the advantage of being a simple and

chemical free method in the study of adulteration in oils.

Acknowledgments The authors are grateful and would like to thankUniversiti Putra Malaysia (UPM) for providing the funding support

awarded to Prof. Dr. Yaakob B. Che Man through the RUGS 91032

grant.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

Employment of Differential Scanning Calorimetry in Detecting Lard Adulteration in Virgin Coconut OilAbstractIntroductionMaterials and MethodsPreparation of BlendsChemical AnalysisFatty Acid Compositional AnalysisTriacylglycerol Compositional Analysis by HPLCThermal Analysis by DSCStatistical Analysis

Results and DiscussionChemical AnalysisFatty Acid Compositional AnalysisTAG Analysis by Reverse-Phase HPLCThermal Analysis by DSCHeating ThermogramCooling Thermogram

ConclusionsAcknowledgmentsReferences

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