26 
CHAPTER III 
PHYSICOCHEMICAL CHARACTERISTIC OF LARD ADULTERATION IN 
RBD PALJ I OIL 
3.0 INTRODUCTION 
Malaysia is one of the exporters of palm oil and it is consumed in more than 
150 countries (Lai, 2005). The special characteristic of palm oil has encouraged it to 
be used in a wide range of products. An oil palm tree consists of 10 % oil and 90 % 
biomass. In order to obtain the final products, palm oil needs to undergo many 
processing steps such as milling, crushing or extraction, refining, pressing. bleached 
and deodorization. After the milling steps, the fresh fruit bunches will produce CPO 
(crude palm oil), PKO (palm kernel oil), palm kernel cake, shell as well as fiber. 
In Malaysia. the oil palm products consists the following categories which are 
palm oil and palm kernel oil products, oleochemicals, bio-fuels, and biomass (Lai, et 
al., 2012). CPO is further processed into refined products such as refined bleached 
deodorized (RI31)) palm oil, RBD palm olein and RBD palm stearin. Towards the end. 
different products are being produced from this process. For example, RBD palm 
olefin is normally used to produce frying and cooking oils, shortening's and 
nlaroarines. While RBD palm stearin is used for fatty acids, soaps, fuel and 
emulsifiers. Palm olefin is the liquid fraction from the fractionation process of palm oil 
after crystallization step at controlled temperature. The physical characteristics of 
palm Mein are fully liquid in warm climate and it also has a narrow range of 
glyccridcs. 
27 
Double- fractionated palm olefin or superolein has an iodine value between 60 
and 67. It comprise of high content of oleic acid (C 18: 1), palmitic (C16: 0) as well as 
linoleic acids (C 18: 2). Super olein will becomes cloudy and tend to crystallizes when 
the temperature is lower than its melting point. Since palm olefin can offer several 
technical characteristics that are desirable in food applications, such as resistance to 
oxidation, thus May increase the shelf life of end products. Moreover, palm olein also 
does not emit undesirable odors, does not contain linolenic acid and has a favourable 
nutritional composition for being free of trans fatty acids and contain tocopherols in 
its composition. 
Deep fat frying Will result in desirable and undesirable flavour compounds, 
changes the flavour stability, quality, colour and texture of fried food and nutritional 
quality of' foods. Common chemical reactions in frying oil include hydrolysis, 
oxidations and polymerization. The non volatile compounds will affect the flavour, 
stability, quality as well as texture of the fried foods during storage. During frying, 
factors such as frying temperature and time, frying oil_ antioxidants and the type of 
fiver will affect the hydrolysis, oxidation and polymerization of the oil. 
Theretore, the objective of' this research was to measure the physichochemical 
(Iodine Value. Peroxide Value, and colour intensity) changes of the RBD palm oil 
containing 0 "i (a). 15 96 (b) and 30 % (c) of lard after heating each sample for I 
hour, 2 hours and 3 hours at 120 °C (A), ISO °C (B) and 240 °C Q. 
28 
3.1 MATERIALS AND METHODS 
3.1.1 Materials 
Fresh Refined Bleach Deodorized (RBD) Palm oil and sample of pig's adipose 
tissue were purchased from a local supermarket at Nilai. Negeri Sembilan. Adipose 
tissues were stored at -20 
°C prior to the analysis. 
3.1 
.2 
Sample Preparation 
Lard samples were extracted by rendering adipose tissue in a conventional 
oven (Pensonic ALL-1 IN) at 100 °C for 2 hours according to Rohman and Che Man 
(2009a) with slight modification. The melted fat was filtered through Whatman filter 
paper and dried by the addition of anhydrous Na2SO4 to remove the water content. 
The filtered samples were stored in a tightly closed container in a refrigerator until 
further analysis. The RBD Palm oil was adulterated with lard at various percentages 
(0 I; and )0 ° %%) in w/w volume. The purpose of spiking lard in the fresh RBD 
palm oil was to act as preliminary study to cmulate recycle RED palm oil that might 
Contain lal'd. 
3.1.3 11eating, procedure 
All adulterated oils were heated at 3 different temperatures (120 T. 180 °C 
and 240 °(-') usin. u a digital hotplate (Daihan, Korea) with a controlled temperature 
probes for 3 hours. Each sample were taken at 1,2 and 3 hours of heating time and 
cooled to room temperature before kept in a tightly closed and seal universal bottles in 
a refri11 erator until türthcr analysis. 
29 
3.1.4 Measurement of Iodine value (IV) 
0.04 g samples were weight to the nearest 0.0001 g in the glass weighing 
scoop. The scoop was placed in a 500 ml flask. 20 ml of cyclohexane was added to 
dissolve the fat. Exactly 25 ml of Wijs solution was added. The flask was shakes 
gently before being placed in dark for 1 hour. After standing, 20 ml of potassium 
iodide solution and 100 ml of water were added into the flask. The solution was 
titrated with sodium thiosulphate solution until the yellow colour due to iodine has 
disappeared. 1 to 2 ml of starch indicator solution was added and the titration was 
continued until the blue colour just disappeared after very vigorous shaking. Two 
determinations on the same test sample were carried out. Blank test was also 
simultaneously carried out under the same conditions (PORIM Test Method, 1995). 
The Iodine Value (IV) is given by: 
Iodine value = 12.69N (V'-V42 
l'V 
\N'hcrc; N is the exact normality of the sodium th10SUlphatc solution used 
I is the volume, in millilitres of the sodium thiosuphate solution 
used for blanks 
J'1 is the volume, in millilitres of the sodium thiosuphate solution 
used for the determinations. 
11' is the weight in grams of the test portion. 
30 
1 
. 
1. E Measurement of Peroxide Value (PV) 
2 to 5 grams of sample was weight into 250 ml flask. Then, 30 ml of the acetic 
acid-chloroform was added. The flask was swirled until the sample dissolved in the 
solution. 0.5 ml of saturated potassium iodide was added using graduated pipette. The 
solution was later swirled for 1 minute before being added with 30 ml of distilled 
water. Later, it was titratcd with 0.01 N sodium thiosulphate solution. The titration 
was continued until near the end point to liberate all the iodine from the chloroform 
layer. The thiosulphate solution was added dropwise until the blue colour just 
disappear. The blank test was carried out parallel with the determinations (PORIM 
Test Method, 1995). 
The peroxide value (PV) isgiven by: 
PV = Ll, -Vi, Nx 1000 
H/ 
Where is the volume of millilitres, of the sodium thiosulhhate solution 
of normality N, used for the determination 
is the volume in milliliters of the sodium thiosulphate solution 
used l or the blank test 
Il is the weight, in grams of the test portion 
V' is the normality of the sodium thiosulphate solution 
31 
3.1.6 Colour Intensity 
Colour was measured using the Lovibond tintometer. (Labscan XE Hunter 
lab). Oil samples were taken in a cuvette and were placed in the provided space in 
tintometer . 
The hunter colour scale parameters which are redness, yellowness and 
lightness were used to estimate colour changes during frying as a function of the 
process variables (oil temperature, heating time, percentage of lard). The dominant 
factor in this measurement was the red colour. Then, the result was expressed in 
Lovibond colour units. 
3.1.7 Statistical analysis 
Unsupervised multivariate analysis, principal components analysis (PCA) was 
performed by mean center on data of GC-MS-headspace using Unscrambler Software 
(X 10.3) version. 
32 
3.2 RESULTS AND DISCUSSION 
'hen subjected to repeat heating. many properties of oil's characteristic 
features were exhibited with respect to different range of heating temperatures and 
time of heating. Since vegetable oils consist of mono unsaturated fatty acids (MUFA) 
and poly unsaturated fatty acids (PUFA), these compounds begin to degrade and 
produce various oxidation products. Raw data for sample a (0 % lard), b (15 % lard) 
and c (30 °, ö lard) for IV, PV and colour intensity was shown in Appendix G. 
3 2.1 lodine Value (1V) 
During \Vijs reaction, iodine will react with the unsaturated fatty acids which 
are in the form of double bonds. The high value of iodine number indicates that high 
amount of carbon double bonds in the fats and oil. Therefore. iodine value can be 
used to directly measure the amount of unsaturated tatty acid present (Gopinath et al., 
2009). As heating time was prolonged, all samples showed a decreased in the amount 
of iodine Value as shown in FIGURE 1. According to Cuesta et al. (1991), the 
decreased of iodine value can be attributed to the destruction of double bonds by 
oxidation, scission and polynmerization. During this heating temperature, it was 
observed that all samples did not show much change in terms of iodine value. This 
might be because at low temperature (120 "C), the heat is not high enough to break 
most of the double bonds. 
33 
FIGURE 1: Relationship between iodine values heated at 120 "C and 3 hours 
heating time 
59 
58 
57 
än 
ö 56 
55 
54 
v 
53 
0 
52 
51 
SO 
y=-0.382 x+ . 
Rz = 0.794 
lhr 2hr 3 hr 
Heating time (hour) 
a (09% lard + 100% palm oil) cb (15% lard +-$5% palm oil) 'c (30% lard + 70% palm oil) 
The iodine values for sample a, b and c at more immense temperature (1 80 °C 
and 240 "C) were shown in FIGURE 2 and FIGURE 3 respectively. All samples 
showed a decreased in terms of iodine value with sample c showed the highest 
changes at both ISO "C' and 240 T. According to Marikkar and Yanty (2013), in lard. 
oleic acid are the most dominant fatty acid (24 "o to 51 °°) followed by palmitic, 
linoleic and stearic acid consecutively. The major triacylglycerol (TAG) in lard are 
PLL, OOL. LPO, OPO. PPO and SPO (0 = oleic acid. P= palmitic acid, S= stearic 
acid, L linoleic acid) where OPO are the most dominant TAG molecular species 
while LPO and SPO are the second and third most abundant. In palm oil. the major 
species are PPO, POO, POL, and PPL (Andrikopoulos. 2002). Since lard contains 
more unsaturated fatty acid, thus the high temperature might cause the unsaturated 
fatty acid to breakdown into other intermediate compounds. Therefore it has 
34 
undergone the highest changes in terms of iodine value when subjected to higher 
temperature. Alireza et al. (2010) obtain the same pattern in the reduction of iodine 
value when subjected the RBD palm oil, sesame oil, canola oil and their blending to 5 
days of heating at 180 T. The highest significant changes (p< 0.05) was observed in 
canola oil due to the presence of high amounts of polyunsaturated fatty acids (30 
X 100 g). 
FIGURE 2: Relationship between iodine values heated at 180 "C and 3 hours heating 
tillle 
0 
0 
v 
ý 
> 
v 
c 
-0 
0 
60 
59 
58 
57 
56 
55 
54 
53 
52 
a (0° lard + 100/palm oil) b (15% lard 
+ 
85% palm oil) c( 
ý/° lard + 70% palm oil) 
3.5 
Heating time (hour) 
35 
FIGURE 3: Relationship between iodine values heated at 240 °C and 3 hours heating 
time 
60 
58 
"C 
Sa 
y= -2.76x + 61.995 
R2 - 0.9965 
-1.3475x-f 57.872 ý ---- -- -ý - ---- ®---- ----- -rtt`=i1I1L83 
y= -1.8425x+ 57.2 53 
52 R' =0.9/81 
,0 
48 
46 
1111 2 fir 
a (016 lard + 100St palm oil) E, b lard +b59q alm il) 
eating time (lioui 
3.2.2 Peroxide Value (PV) 
3 hr 
c (30% lard + 70%% palm oil) 
Peroxide value measures the extent to which oil has undergo primary 
oxidation. It is also a measure of rancidity of the oil. Peroxide value is not a good 
indicator to evaluate the oil quality changes because of the degradation of 
hvdroperoxide in high temperature. However, it can be the indicator of oil instability. 
According to Olaniyan (2010). an increase in heating time and temperature will 
increase the acid value, peroxide value and the colour intensity of the oil. Initially in 
FIGURE 4. all samples showed a low peroxide value, however, the increased in time 
of heating has increased the peroxide value for all samples. Sample c showed the 
highest changes in peroxide value as the heating time was prolonged. This might due 
to the high amount of unsaturated fatty acid contributed by 30 "r'o lard. Bolourian et al. 
37 
When the heating temperature was increased to 180 °C (FIGURE 5), at 1 hour 
heating time. all samples showed a higher peroxide value compared to 1 hour heating 
time at 120 °C. As the heating time was prolonged, sample b and sample c showed a 
decreased pattern in peroxide value, while peroxide value for sample a was still 
increased even though not as rapid as in temperature 120 T. When a higher 
temperature was subjected to all samples as in FIGURE 6. they showed a decreased 
in peroxide value. This pattern might occur because at 180 °C, the secondary 
oxidation products started to form and accumulate. Since peroxide value measure the 
primary oxidation products, thus the value decreases as the secondary oxidation 
products formed. 
FIGURE 5: Relationship between peroxide values heated at ISO °C and 3 hours heating 
time 
25 
20 
Q 
C) ý 
15 
v :3 
10 
72 
C) 5 Q- 
y=-1.45x+21.677 
R2 = 0.9317 
RZ = 0.9678 
y=1.415x + 11.98 
Rz = 0.9408 
0II1 
1hr 2hr 3 hr 
Heating time (hour) 
a (0% lard + 100% palm oil) Qb (15% lard + 85% palm oil) c (30% lard + 70% palm oil) 
38 
FIGURE 6: Relationship between peroxide values heated at 240 °C and 3 hours heating 
time 
ý v E 
v 
ý 
> 
v -0 X 
ý 
v 
ý 
10 
9 
8 
7 
6 
5 
4 
3 
2 
1 
0 
y= -0.67x + 9.2033 
RZ = 0.9653 
lhr 2hr 3 hr 
Heating time (hour) 
oa (0% lard + 100% palm oil) 0b (15% lard + 85% palm oil) c (30% lard + 70% palm oil) 
y= -1.755x + 10.843 
3.3 Colour Intensity 
As heating or frying proceeds, oil colour become darker. Many factors may 
influent the changes in oil colour such as type and amount of food being fried. Food 
components will interact with oil and form coloured constituents like Maillard 
browning products. Since changes in oil colour may results from more than one 
chemical process, therefore the use of oil colour to monitor the quality level is not 
valid when evaluating a wide range of frying operations (Takeoka et al., 1997). 
The value for L*, a* and b* for samples a, b and c at 120 °C, 180 OC and 2240 
''C heating at 3 hours were shown in Table 1. L defined lightness, +a depicts a shift 47 
towards red and a towards green, while +b represent a shift towards yellow and -b 
towards blue. . As the heating time increased fiom 1 hour to 3 hours, all samples shows 
39 
a trend in reduction of L* value indicating dark oil formed. On the contrary, all 
samples showed an increased in terms of a* value (Refer TABLE 1). This trend 
showed that the samples become darker as the time of heating was prolonged. 
TABLE 1: Hunter Lab value for 0 %, 15 %, 30 % lard in RBD palm oil at 120 °C, 180 °C 
and 240 °C for 3 hours of heating 
L* a* b* 
aAl 34.26±0.03 -1.97 ± 0.02 7.13 ± 0.01 
aA2 34.05 ± 0.01 -1.62 ± 0.01 7.15 ± 0.03 
aA3 33.25±0.02 -1.58±0.01 7.29±0.03 
aB1 3929±0.01 1.72±0.03 7.42±0.02 
aB2 31.06±0.04 -1.31 ±0.04 7.95±0.01 
aB3 30.6±0.02 -1.29±0.02 7.84±0.02 
--ac 
l 39.76 ± 0.03 -1.76 ± 0.02 8.11 ± 0.03 
aC2 36.88±0.02 -1.33 ± 0.01 8.73±0.02 
aC3 35.84 ± 0.01 -1.23 ± 0.03 8.81 ± 0.02 
bA 1 38.00 10.04 -1.79 ± 0.01 7.6 ± 0.03 
bA2 37.86 f 0.02 -1.54 +0.01 7.67 ± 0.02 
bA3 ')2. 
_76±0.0_3 
-1.26±0.033 7.61 ± 0.01 
bBl 36.78±0.03 -1.83±0.04 8.2±0.01 
hß2 36.35±0.01 -1.81 ±0.02 8.44±0.05 
bB3 36.38±0.04 -1.44±0.01 8.47±0.03 
bCl 36.75±0.04 -1.56±0.01 8.52±0.02 
bC2 36.54-+-0.01 -1.33±0.04 8.44±0.02 
bC3 33.9±0.02 -1.18±0.01 9.08±0.04 
cAl 3 i. 44±0.03 -1.9±0.02 8.27 ± 0.02 
cA2 >>. 87-+-0.04 -1.6±0.02 8.22±0.04 
cA3 34.09 ± 0.03 -1.36 ± 0.03 8.07 ± 0.02 
cBl , 
33.83+0.02 -1.6±0.01 9.30±0.03 
c132 
-- 
33.9±0.05 
-- 
-1.55±0.02 9.15±0.02 
cB3 
--- 
-- 33.58 ± 0.02 
-- - 
- -- 
-1.17 ± 0.01 
- 9.16±0.03 
-- cC1 - ---- -- 34.23±0.01 -2.38±0.01 8.23±0.01 
cC2 
cc'3 
34.74±0.04 
----- --- 35.38±0.05 
-1.31 ±0.04 
---- - --- 
-1.07±0.02 
8.49±0.02 
8.36±0.03 
Nute: ntcan % aluc L standard dcx ia(iun 
* +a ^ rcd, -a Srecn, ý+b -- yellow, -b = blue. L. 0 == black. 100 = white 
*a -0 " lard, b-Iý "i, lard, A- 120 °C, 13- 180 °C, C= 240 T. I= I hr. 2= 2 thrs, ;- =hrs 
40 
At low heating temperature (120 °C), even though the a* value increased, 
however not much changes was observed in a* value for all samples as in FIGURE 7. 
It was observed that the lowest a* value among 3 samples were 0% lard while the 15 
°0 and 30 "0 lard showed almost the same values for 3 hours heating time. The 
formation of non volatile decomposition which contained carbonyl group caused the 
darkening of paten oil (Tsaknis. 2002). During frying, the carbonyl will absorb the 
energy of the visible light magnitude. 
FIGURE 7: Colour changes a* for all samples heated at 120 °C for 3 hours heating 
time 
0 
-0.5 
* -1 ý 
y=0.265x - 2.06 
R2 = 0.9989 
y=0.27x-2.16 
: ý: -RZ = 0.9959 C 
ý -1.5 
-z 
-2.5 
y=0.195x - 2.1133 
R2 = 0.826 
0 0.5 1 1.5 2 2.5 3 3.5 
Heating time (hour) 
a (0% lard + 100% palm oil) Lb (15% lard + 85% palm oil) c (30% lard + 70% palm oil) 
When the temperature was increased to 180 °C for 1 hour heating time, not 
much differences were observed when compare to 3 hours heating time at 120 T. 
I Iowever. as the heating time was prolonged, the a* value increased (FIGURE 8). 
41 
FIGURE 8: Colour changes (a*) for all samples heated at 180 °C for 3 hours heating 
time 
0 
-0.2 
-0.4 
-0.6 
-0.8 
ö -1 
-1.2 
y =0.215x - 1.87 y=0.215x-1.87 
R2 = 0.8359 RZ = 0.7848 
-1.4 
-1.6 y=0.195x-2.0833 16 R2 = 0.7884 
-2 
0 0.5 1 1.5 2 2.5 3 3.5 
Heating time (hour) 
a (0% lard + 100% palm oil) b (15% lard + 85% palm oil) c (30% lard + 70% palm oil) 
I 
The changes in colour was the biggest when all samples were heated at 
highest heating temperature (240 °C) as shown in FIGURE 9. As the heating time 
was increased, the a* values for all samples also increased with sample c showed the 
highest changes during 3 hours heating time at 240 T. 
42 
FIGURE 9: Colour changes (a*) for all samples heated at 240 °C for 3 hours 
heating time 
0 
-0.5 
* -1 m 
ö 
-1.5 0 u 
= 0.265x 
-z 
y=0.655x - 2.8967 
R' = 0.882 
-2.5 
0 0.5 1 1.5 2 2.5 3 3.5 
Heating time (hour) 
a (0% lard + 100% palm oil) b (15% lard + 85% palm oil) c (30% lard + 70% palm oil) 
?. 4 Principal Components Analysis 3 
Principal components analysis is a tool to reduce a large set of variables to a 
small scale but still contains most of the information from the large set. Results of 
PCA were summarized from scores plot (Appendix H) and loadings plot (Appendix 
I). 
The scores plot for sample a. b and c at I ?0 
°C, I SO "c and 240 °C was shown 
in FIGURE 10. From the plot, it was observed that samples are clustered according to 
their heated temperatures despite contain a 
lard or no lard. Scores plot may be used to 
Interpret the similarities or 
differences among samples. The close' the sample in the 
score plots, the more similar they are with respect to the two components concerned. 
43 
Conversely, samples that are far away from each others are different from each other. 
In FIGURE 10, each group was different from each other since a significant clustered 
\\ as observed. A was denoted for samples heated at 120 °C, B for samples heated at 
1 S0°C, while C for samples heated at 240 °C. However, some samples that were 
heated at 120 °C were seemed to be presented at group B. This might he because of 
the high heating temperature as they were heated at 2 or S hours of heating at 120 T. 
FIGURE 10: Scores plot of physicochemical tests for all samples heating at 120 °C, 
180 °C and 240 °C for 1.2 and 3 hours heating time 
Scores 
-35 -30 -25 -20 -15 -10 -5 PC-1 (96%) 
0 5 10 15 
*a 11 °o lard in IN °o RBD palm oil, b= 15 % lard in $5 °o RBD palm oil. c- 30 00 lard on 70 °%o 
RI3D palm oil. A= 120 "C. B= ISO 
"C. C= 240 "C, 1= 1 hour heating. 2_2 hours heating, 3= 3 
hours heating 
The importance of the different variables for the components specified was 
shown in FIGURE 11. PV was correlated with cA3 
(samples c heated at 120 "C for 3 
hours). Among all samples, it showed the 
highest PV Which were 46.67 f 0.01. This 
might he because it contains 
high amount of unsaturated fatty acid compared to other 
44 
sample and the heating time was longer. When the heating temperature was increased, 
the PV value was low due to the formation of secondary oxidation products. 
FIGURE 11: Loadings plot of physicochemical tests (PV, IV and color 
intensity) 
0 
Ill. ior 
-0.2 ý 
-0.3 
-0.4 
U 
-0.6 
-0.7 
-0.8 
-0.9 
IV 
cA3 
PV* 
-1 ý "1 
-01 0 0.1 0.2 0ý3 0.4 0.5 0.6 0.7 0.8 0.9 
PC-1 (95%) 
3.3 CONCLUSION 
Heating affects the physicochemical characteristic of oil. For iodine value, at 
low heating temperature (120 °C), all samples did not showed much changes. 
However, when the heating temperature was increased to 180 °C and 240 T. all 
samples showed a decrease in iodine value with sample c showed the highest changes. 
Heating destructs the double bonds in the unsaturated fatty acid. As for peroxide 
value, at prolong heating time at 120 °C, all samples showed an increased in peroxide 
value with samples c with the highest changes due to the formation of primary 
oxidation product. However, as the heating temperature was increased to 180 °C, a 
different pattern was observed as there was a decreased in PV for sample b and c due 
45 
to the formation and accumulation of the secondary oxidation products. While sample 
a still showed an increase in PV. At 240 
°C, all samples showed a decreased in PV. In 
terms of colour, at temperature 120 
°C, not much changes was observed in a* values 
for all samples. It was observed that as heating time 
increased, there was a reduction 
in the L* value and increment in the a* value. 
Changes in colour was the highest 
when all samples were heated at 240 
T. The scores plot showed an accumulation of 
samples based on the heating temperature and there was no 
difference observed 
between samples that contain lard and no 
lard. Therefore, it was concluded that the 
physicochemical tests in terms of colour 
intensity, PV and IV could not differentiate 
between 0 °ö, 15 °ö and 30 % lard heating at 120 
°C, 180 °C and 240 °C for 3 hours 
heating time.