CC BY-NC-ND
0Annals of Agricultural Science (2011) 56(2), 89-96
Faculty of Agriculture, Ain Shams University Annals of Agricultural Science
www.elsevier.com/locate/aoas
ORIGINAL ARTICLE
Quality characteristics of chocolate - Containing some fat replacer
M. El-kalyoubi a, M.F. Khallaf a, A. Abdelrashid a, Eman M. Mostafa b *
a Food Science Dept., Faculty of Agric., Ain Shams Univ., Shoubra El-Kheima, Cairo, Egypt b Misr Food Additives Company "MIFAD", Cairo, Egypt
Received 28 April 2011; accepted 12 May 2011 Available online 29 December 2011
KEYWORDS
Palm olien;
Particle size distribution; Rheological properties; Sensory evaluation; Chocolate
Abstract Chocolate products are the most important products of candy that are popular with a lot, especially children and as a source of energy in addition to its high nutritional value. In chocolate industry, many of ingredients such as cocoa, sugar, cocoa butter, fats, emulsifiers and flavorings play an important role in product quality. This research aims to assess the fatty replacement and its impact on the organoleptic and rheological characteristics of chocolate for the treatment of some problems that arise during marketing thereby increasing the economic returns of these products. Novel functional chocolate spreads were formulated by replacing palm oil in conventional soft chocolate spread by palm olein and cotton seed oil at 25%, 50%, 75% and 100% levels. Physical, chemical and rheological properties such as particle size distribution, apparent viscosity, flow behavior constants and hysteresis behavior, also sensory evaluation such as smoothness, melt rate, cocoa flavor and milk flavor were measured in soft chocolate samples. Rheological properties indicated that the lower replacement rate 25% of palm olien was closest to the control sample and increasing the ratio of fat replacer had significant advance effect on rheological properties of investigated chocolate. Sensory evaluation revealed that chocolate made from 25% palm olein was more accepted as conventional chocolate.
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* Corresponding author.
E-mail address: emanmmostafa@hotmail.com (E.M. Mostafa).
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Introduction
Chocolate is the most frequently craved food (Hill and Heaten-Brown, 1994), has an uniquely attractive taste (Chiva, 1999) and might even be beneficial for health (Serafini et al., 2003). The popularity of this food appears to be mainly due to its potential to arouse sensory pleasure and positive emotions (Macht and Dettmer, 2006). Chocolate is perceived as a comfort food and has been shown to be craved and consumed during depressive moods (Macdiarmid and Hetherington, 1995). Chocolates are complex multiphase systems of particu-late (sugar, cocoa, certain milk components) and continuous
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doi:10.1016/j.aoas.2011.05.009
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phases (cocoa butter, milk fat and emulsifiers). During manufacture, refining and conching determine particle size and suspension consistency and viscosity, to yield specific textural and sensory qualities (Afoakwa et al., 2008a).
The physical properties, rheological behavior and sensory perception of chocolate are influenced largely by its processing technique, particle size distribution and ingredient composition. To enhance chocolate texture, solid particle size distribution and ingredient composition can be manipulated to modify physical properties, rheological behavior and sensorial attributes (Afoakwa et al., 2007). Particle size distribution and composition have been reported to influence chocolate rheological properties (Servais et al., 2002). Particle size distribution influences rheology and texture with specific surface area and mean particle size influencing yield stress, plastic viscosity, product spread and hardness (Afoakwa et al., 2008b). Smaller particles improve sensory properties (Ziegler et al., 2001) but plastic viscosity and yield stress increase due to changes in surface area of particles in contact with fat phase. Particle size optimizations can reduce requirement for viscosity modifiers and improve process control (Afoakwa et al., 2008c).
Central to sensory character is continuous phase lipid composition, which influences mouth feel and melting properties. Chocolate triglycerides are dominated by saturated stearic
(34%) and palmetic (27%) fatty acids and monounsaturated oleic acid (34%). Chocolates are solid at ambient (20-25 0C) and melt at oral temperature (37 0C) during consumption giving a smooth suspension of particulate solids in cocoa butter and milk fat (Beckett, 1999 and Whitefield, 2005). Differences in the sensory characters of chocolate can be attributed to use of different cocoa types, variations in ingredient proportions, use of milk crumb instead of milk powder, blending techniques and processing methods. Specifications depend on type of chocolate and its intended use (Jackson, 1999).
Some vegetable fats are similar to cocoa butter in triglyceride composition and such cocoa butter equivalents (CBEs) can be added in any proportion to chocolate without causing a significant effect on texture. Cocoa butter replacers (CBRs) such as lauric fats, palm kernel and coconut oils, are used to totally replace cocoa butter (Talbot, 1999). The palm olein is increasingly becoming available in food stores as well (Gee, 2007). The carotenes in palm olein have been demonstrated to have the highest bioavailability among all known plant carotenes. Palm olein has been used in many forms to deliver its provitamin (A) carotenes to children at risk, in several cross-continental studies. The findings are consistent: red palm oil administered even in low dose, protects the malnourished child against vitamin A deficiency and the risk of going blind. Moreover, carotenes are known to have several other physiological
Table 1 Formulation for soft chocolate by replacing palm oil with palm olein and cotton seed oil.
Ingredients % Control 25% 50% 75% 100%
Palm oil 20.20 15.15 10.10 5.05 0.00
Sucrose 44.00 44.00 44.00 44.00 44.00
Cocoa mass 4.00 4.00 4.00 4.00 4.00
Cocoa powder 4.00 4.00 4.00 4.00 4.00
Full cream milk powder 20.25 20.25 20.25 20.25 20.25
Palm olein (or) cotton seed oil 0.0 5.05 10.10 15.15 20.20
Skimmed milk powder 6.75 6.75 6.75 6.75 6.75
Vanillin 0.01 0.01 0.01 0.01 0.01
Lecithin 0.7 0.7 0.7 0.7 0.7
P.G.P.R 0.14 0.14 0.14 0.14 0.14
Table 2 Chemical properties of ingredients used in soft chocolate.
Ingredients % Moisture Chemical constituents g/100 g dry matter % Ash % Fat
Skimmed milk powder Full cream milk powder Cocoa powder Cocoa mass 2.97 ± 0.51 2.48 ± 0.53 3.08 ± 0.42 1.30 ± 0.12 6.49 ± 0.34 0.11 ± 0.01 4.65 ± 0.26 6.80 ± 0.35 1.1 ± 0.01 26.62 ± 0.58 11 ± 0.01 65.0 ± 0.01
Table 3 Physiochemical analysis of fat ingredients used in soft chocolate.
Ingredients Melting point (°C) Start Final FFA Peroxide value Iodine number Saponification value
Palm oil 8.52 ± 0.56 9.29 ± 0.51 0.04 ± 0.01 0.01 ± 0.002 64.89 ± 2.50 190.88 ± 4.72
Palm olien 12.54 ± 0.62 13.33 ± 0.58 0.04 ± 0.01 0.05 ± 0.02 63.30 ± 2.48 -
Cotton seed oil 11.0 ± 0.56 12.0 ± 0.51 0.04 ± 0.01 0.01 ± 0.002 103.4 ± 2.50 191.7 ± 4.72
Table 4 Particle size distribution of soft chocolate.
Treatments Palm olein Cotton seed oil
mi m2/g im mi m2/g im
Control 21.00 1.14 12.52 21.00 1.14 12.52
25% replace 20.26 1.56 10.766 24.01 1.41 12.521
50% replace 21.48 1.53 11.262 22.18 1.46 11.69
75% replace 19.79 1.71 10.349 24.00 1.41 12.59
100% replace 21.55 1.48 11.400 17.56 1.65 9.418
a very high value in the confectionary market (Norulaini et al., 2004).
This study aims to produce high quality chocolate and reduce the problem of hardness encountered in the consumption of soft chocolate processed with palm oil and full cream milk powder. In addition to investigate new ingredients were added to avoid the hardness of chocolate by estimating the rheolog-ical and sensory properties of novel soft chocolate.
Materials and methods
£ 3.5
1 ¡ I \ ¡I
1 10 Particle See (urn)
1000 3000
Fig. 1a Particle size distribution of soft chocolate fat replaced with 25% palm olein.
Fig. 1b Particle size distribution of soft chocolate fat replaced with 25% cotton seed oil.
functions, i.e. antioxidant activity, immune function enhancements and anti-cancer activity (Sundram, 2005). Palm kernel oil (PKO) is regarded as food-grade oil that is of high quality. Its application could be greatly extended if PKO components could be fractionated or modified to have properties that are closer to those of cocoa butter replacers (CBRs), which have
Materials
Cocoa powder and cocoa mass were obtained from Savola Egypt Co., crystal sugar (sucrose) was purchased from Sugar Egypt Co. The sugar had a moisture of 0.2% with a particle size ranged from 0.2 to 0.75 mm. Skimmed milk powder and full cream milk powder of 26% fat were supplied from Al -GARAS FOOD ingredients Co. Crystal vanillin was supplied from N.A. Ibrahim Co. Palm oil (non-lauric specialty oil based on fractionated vegetable fat) was obtained from Loders Cro-klaan Co. RBD olein (refined, bleached and deodorized double fractionated palm olein of low melting point) obtained from IFECO Egypt Co. Hydrogenated cotton seed oil was obtained from Local Egypt Co., Lecithin which had a viscosity of 20003000 CPS was obtained from Luxc Myer Co., while P.G.P.R (polyglycerol polyricinoleate) numerical references - EEC 476 was obtained from Palsgaard Co.
Preparation of chocolate samples
The following ingredients were used in the manufacture of soft chocolate as previously described by Melo et al. (2009) and modified using palm oil, skimmed milk powder and P.G.P.R (polyglycerol polyricinoleate). Samples were prepared by replacing part of the palm oil with palm olein and cotton seed oil at levels of 25%, 50%, 75% and 100%. The quantities of the ingredients that were presented in all the formulations are shown in Table 1.
Methods
Chemical properties
Moisture and fat contents of the raw materials namely full cream milk powder, skimmed milk powder, cocoa powder and cocoa mass as well as free fatty acids, peroxide value, iodine number and saponification value of palm oil, palm olien and cotton seed oil were determined according to A.O.A.C. (2000).
Fig. 2 Apparent viscosity as a function of shear rate of chocolate samples made using palm olien as a replacer for palm oil.
Table 5 Apparent viscosity as a function of shear rate of chocolate samples made using palm olien as a replacer for palm oil.
Shear rate Control 25% Palm olien 50% Palm olien 75% Palm olien 100% Palm olien
0.333 183,514 113,604 113,604 157,297 69,910
0.6 113,975 130,950 77,600 106,700 43,650
1.0 80,025 84,390 52,380 72,750 32,010
1.8 56,583 56,583 35,567 48,500 21,017
3.0 43,650 43,650 27,160 37,830 15,520
5.4 33,681 30,717 19,939 29,639 11,317
9.0 28,453 31,363 14,550 25,543 9700
16.2 19,549 35,543 15,269 2874 719
27.0 24,525 29,856 15,994 24,525 77,840
48.0 22,792 2399 14,395 20,993 8397
81.0 22,037 24,880 13,862 19,549 8175
145.8 19,746 19,746 13,230 15,797 7898
Fig. 3 Apparent viscosity as a function of shear rate of chocolate samples made using cotton seed oil as a replacer for palm oil.
Table 6 Apparent viscosity as a function of shear rate of chocolate samples made using cotton seed oil as a replacer for palm oil.
Shear rate Control 25% C.S.O* 50% C.S.O 75% C.S.O 100% C.S.O
0.333 183,514 122,342 157,297 174,775 192,252
0.6 113,975 87,300 101,850 121,250 130,950
1.0 80,025 64,020 78,570 87,300 87,300
1.8 56,583 45,267 37,183 63,050 56,583
3.0 43,650 32,980 40,740 47,530 43,650
5.4 33,681 26,944 33,950 37,722 33,411
9.0 28,453 22,957 30,070 41,586 29,747
16.2 19,549 24,880 30,212 28,435 28,435
27.0 24,525 20,260 26,657 26,657 26,657
48.0 22,792 19,193 26,391 26,391 26,991
81.0 22,037 16,350 24,525 24,880 26,657
145.8 19,746 15,994 19,746 19,746 19,746
* C.S.O = Cotton seed oil.
Table 7 Flow behavior constants (K) and (n) of investigated soft chocolate samples.
Samples Palm olein Cotton seed oil
K (Pas.S) n R2 K (Pas.S) n R2
Control 795.21 0.6509 0.9570 795.21 0.6509 0.9570
25% replacer 783.88 0.6987 0.9732 616.20 0.6763 0.9766
50% replacer 502.12 0.6551 0.9516 716.25 0.7074 0.9657
75% replacer 726.83 0.6586 0.9698 874.57 0.6668 0.9790
100% replacer 264.83 0.6000 0.6662 850.80 0.6645 0.9583
3.E+05 2.E+05 2.E+05 1.E+05 5.E+04 0.E+00
Control
25 % Cotton Seed 50 % Cotton Seed 75% Cotton Seed 100 % Cotton Seed
S hear rate ( sce -1 )
Table 8 Hysteresis area of soft chocolate samples replaced
with palm olien and cotton seed oil.
Treatments Hysteresis area in cm2
Palm olein Cotton seed oil
Control 0.10 0.10
25% replacing 0.44 0.48
50% replacing 0.33 0.17
75% replacing 0.17 0.38
100% replacing 0.1 0.34
Physical properties
Melting point. The method given by the Egyptian Standards Specification NO.51 (2005) was applied for measuring the melting point of palm oil, palm olien and cotton seed oil.
Particle size distribution. Particle size was determined with Laser Diffraction Particle Size Analyzer 2000 Ver. 5.31 (Malvern Instrument Ltd., according to Do et al. (2007)).
Rheological properties
Viscosity. Viscoelasticity of soft chocolate was measured at zero time and after 3 and 6 months by a rotational type RV (Rheotest 2 - Germany), the investigated samples were introduced into '' S2''. The development shear stress values were measured at shear rate from 0.333 to 145.8 as described by Aeschlimmann and Beckett (2000). Apparent viscosity was calculated and given with their corresponding curves, from which the slope of the relation between shear stress and shear rate represented the overall apparent viscosity.
Apparent viscosity g = - x 100
Control
■Ascending ■ Descending
Shear rate (S)
using 25 % Palm olein
Ascending Descending
100 200 Shear rate (S-1)
3.50E+04 3.00E+04 O 2.50E+04 -0 2.00E+04
W 1.00E+04
S 5.00E+03
0.00E+00
Using 50 % Palm olein
Ascending Descending
50 100 150 200 Shear rate (S-1)
3.50E+04'
CO 5.00E+03-0.00E+00
Using 75 % Palm olein
Ascending Descending
50 100 110 200 Shear rate (S-1)
Using 100 %Palm olein
■Ascending ■ Discending
Shear rate (S -1)
Fig. 4 Hysteresis curves of soft chocolate using different percentages of palm olien.
where g is Apparent viscosity in cp, s is shear stress (dyn/cm2), and y is shear rate (S_1).
The non-Newtonian behavior index (n) and consistency coefficient (K) were applied and tested according to the formula as given by Dail and Steffe (1990).
s = K ■ yn
The gap between the ascending and descending shear stress curves that was measured by a digital planimeter "KP-g2" reprints hysteresis area in cm2.
Sensory evaluation
Sensory evaluation of investigated chocolate samples was applied according to methods Misnow et al. (2004). Chocolate
spreads were evaluated by 10 trained panelists, samples were kept at room temperature (24 0C ± 2) for 1 h before evaluation. Samples were served in white plastic cups; water and bread were provided for cleaning the palate between samples. Each panelist was asked to give a number from 1 (extremely dislike) to 9 (extremely like) on the hedonic scales for texture attributes: smoothness (sensation on tongue and roof of mouth while product is melting), melt rate (rate of disappearance in mouth) and viscosity (perception of thickness/thinness of sample in mouth).
Statistical analysis
Analysis of variance was computed using All PC-Stat Version IA procedures (SAS, 1996). Differences arrange means were evaluated using Duncan's multiple range test (p < 0.05).
Control
Using 25 % Cotton Seed Oil
-Ascending - Descending
) 50 100 150 200 Shear rate (S-1)
Using 50 % Cotton Seed Oil
-Ascending ■ Descending
50 100 150
Shear rate (S-1)
Ascending Descending
0 50 100 150 200
Shear rate (S-1) Using 75 % Cotton Seed Oil
Ascending Descending
Shear rate (S-1)
Using 100 % Cotton Seed Oil
55 1.50E+04 1.00E+04 5.00E+03 0.00E+00
-Ascending Descending
Shear rate (S -1)
Fig. 5 Hysteresis curves of soft chocolate using different percentages of cotton seed oil.
Results and discussion
Chemical parameters
Proximate chemical composition of soft chocolate constituents are summarized in Table 2. Moisture content of skimmed milk powder, full cream milk powder, cocoa powder and cocoa mass were 2.97%, 2.48%, 3.08% and 1.30%, respectively. The cocoa mass was found to be higher content of fat reaching 65%.
Data presented in Table 3 showed chemical analysis of fat ingredients of palm oil, palm olein and cotton seed oil. The melting point of palm olein gave the highest value (13.33 0C) while, for cotton seed oil and palm oil were 12.0 and 9.29 oc, respectively. However, the free fatty acid content was equal to each other. Data found that there were no significant differences in peroxide and saponification values between palm oil and cotton seed oil. While, cotton seed oil was the highest one in iodine number (103.4).
Physical properties of soft chocolate
Particle size distribution
Laser scattering analysis indicated a mono modal particle size distribution (P.S.D) of soft chocolate (Table 4). Data of PSD gave volume histograms (0.84 pm), specific surface area (m2/ g) and mean particle diameter D[4,3] (pm). PSD of 25% replacing palm oil with palm olein was less than control in mean particle size (10.76 pm), however replacing with cotton seed oil at the same ratio was similar to control (12.52 pm) as seen in Figs. 1a and 1b. Beckett (1999) concluded that largest particle size and solids specific surface area were the two key parameters for chocolate manufacture. The former determines chocolate coarseness and textural characters; the latter is associated with the requirement of fat for desirable flow properties. From the obtained data, it could be noticed the specific surface area was significantly increased as a function of increasing fat replacer ratio from 25% to 75% when samples were statistically analyzed at p 6 0.05.
Rheological measurements
Apparent viscosity. It seems clear that tested chocolate samples are of Non-Newtonian fluids and when the measured apparent viscosity (cp) is figured against shear rate (S_1) for chocolate
formulated either with palm oil or palm olien (Fig. 2) the following trends may be concluded. Values of viscosity indicated the presence of a noticeable variation within samples at any given shear rate. For instance, at shear rate 5.4 S_1 the apparent viscosity was 33681 cp for the control chocolate and 30,717 cp for the sample replaced with 25% palm olien (Table 5). The noticeable variation is a function of fat replacement effect (Afoakwa et al., 2007).
The available data (Fig. 3 and Table 6) also proved that the replacement of palm oil with cotton seed oil with different ratios showed apparent viscosity of 26,944, 33,950, 37,722 and 33,411 cp for 25%, 50%, 75% and 100% replacement at shear rate 5.4 S_1 comparative with control sample that was 33,681 cp. On the other hand, degree of variation within the apparent viscosity was narrow with control after shear rate 16.2 S_1 and it reflects that there is no significant difference in these ratios, which did not affect chocolate viscosity.
Flow behavior constants. The calculated parameters (flow behavior index n) and (consistency coefficient K) for control, fat replacer with palm olein as well as cotton seed oil soft chocolate samples are summarized in Table 7. Correlation coefficient (R2) for the regression analysis of log shear stress log shear rate data was 0.9516 indicating a strong correlation for the tested parameter within the aforementioned chocolate samples.
The flow behavior index (n) of control and treated chocolate samples was less than 1.0 giving a value ranging from 0.6000 to 0.7074; a pattern which is indicating their strong non-Newtonian pseudoplastic behavior. The added level of palm olein caused high reduction in consistency coefficient (K) from 783.88 (25% replacing) to 264.83 (100% replacing) Pas.S in soft chocolate. These results confirm with those reported by El-Hadad et al. (2011). On contrary, added level of cotton seed oil caused increase in consistency coefficient from 616.20 to 850.80 Pas.S, respectively.
Hysteresis behavior. The hysteresis area of tested soft chocolate samples was given in Table 8, which was based on Figs. 4 and 5. Soft chocolate with 25% palm olein showed a hysteresis area of 0.44 cm2, while 100% replacing showed a decremental trend in hysteresis area to be 0.1 cm2. However, hysteresis area of soft chocolate with cotton seed oil replacer at 25% was higher than the other treatments (0.48 cm2). Generally, fat replacer showed a higher hysteresis area than control sample. These
Table 9 Sensory evaluation of the soft chocolate replacement the palm oil with palm olein and cotton seed oil. Treatments Texture attributes Assess flavor
Smoothness Meltrate Viscosity Cocoa flavor Milk flavor
Palm olein
Control 9.6 ± .5a 9.7 ± .5a 9.8 ± .4a 9.8 ± .4a 9.7 ± .5a
25% 9.2 ± 4 b 9.6 ± .5a 9.3 ± .5a 9.2 ± .4b 9.2 ± .4b
50% 8.7 ± .5bc 9.2 ± .4a 9.5 ± .5a 8.8 ± .6bc 8.7 ± .5c
75% 8.2 ± .1.0c 7.8 ± 1.0b 8.0 ± .9b 8.5 ± .6c 8.4 ± .5cd
100% 8.2 ± .1.0c 8.3 ± .9b 8.4 ± .7b 7.9 ± .7d 8.2 ± .6d
Cotton seed oil
Control 9.6 ± .5a 9.7 ± .5a 9.7 ± .5a 9.7 ± .5a 9.7 ± .5a
25% 9.0 ± .9a 8.6 ± .5a 8.6 ± .5b 8.2 ± .4b 8.2 ± .4b
50% 8.1 ± .3b 8.2 ± .4b 8.6 ± .5b 7.5 ± .7c 7.6 ± .5c
75% 7.4 ± .8b 6.8 ± 1.0c 6.6 ± .9c 7.0 ± .8cd 6.7 ± .5d
100% 7.4 ± 1.173b 7.2 ± .788b 7.0 ± .9c 6.6 ± .5d 6.7 ± .5d
evidences are in agreement with those obtained by Dail and Steffe (1990).
Sensory properties
Mean scores of sensory properties of soft chocolate Table 9 reveal that 25% replacing is the best acceptable ratio either with palm olien or cotton seed oil. Chocolates which were prepared with replacing palm oil with palm olein at ratio 25% had higher scores of cocoa flavor (9.2) which was found to be significantly higher at p 6 0.05 in comparison with all treatments. Utilization of cotton seed oil as a fat replacer up to 50% resulted chocolate smoothness that was significantly comparable in acceptability compared to the control. As cotton seed oil replacement increased, the chocolate melt rate was less acceptable, as judged by panelists. Finally, a high quality functional chocolate was able to be produced by replacing palm oil with palm olein at 25% level. These results are in agreement with those mentioned by El-Hadad et al. (2011) who studied the high quality functional chocolate spread by replacing the butter fat with red palm olein at 20% level.
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