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Effect of replacement of fat with sesame oil and additives on rheological, microstructural, quality characteristics and fatty acid profile of cakes
Food Hydrocolloids 23 (2009) 1827–1836
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Effect of replacement of fat with sesame oil and additives on rheological, microstructural, quality characteristics and fatty acid profile of cakes M. Sowmya a, T. Jeyarani b, R. Jyotsna a, D. Indrani a, * a b
Flour Milling, Baking and Confectionery Technology Department, Central Food Technological Research Institute, Mysore 570 020, Karnataka, India Lipid Science and Traditional Foods Department, Central Food Technological Research Institute, Mysore 570 020, Karnataka, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 25 August 2008 Accepted 2 February 2009
Effect of replacement of fat with 25, 50, 75 and 100% sesame oil (on fat basis); 50% sesame oil, hydrocolloids and emulsifiers on the rheological, microstructural, quality characteristics and fatty acid profile of cake was studied. Addition of increasing amount of sesame oil decreased viscosity, increased specific gravity of cake batter; decreased cake volume and overall quality score. Microstructure studies showed disrupted gluten matrix. Among the two different hydrocolloids [hydroxypropylmethylcellulose (HPMC) and xanthan] and emulsifiers [glycerol monostearate (GMS) and sodium stearoyl-2-lactylate (SSL)] tried, HPMC and SSL increased the batter viscosity, decreased the specific gravity, increased the volume and overall quality score. Use of combination of HPMC and SSL improved significantly the quality characteristics of cake with 50% sesame oil in such a way that the overall quality score was higher than that of the control cake with fat. The microstructure of cake crumb with 50% sesame oil and HPMC showed a smooth structure with less number of cavities and SSL showed a continuous protein matrix. On replacing the fat with 50% sesame oil, there was a decrease in saturated fatty acids and increase in unsaturated fatty acids, particularly linoleic acid. The fatty acid profile of cake with 50% sesame oil was better than the control cake as there was 2.4 times decrease in palmitic acid content and 5.9 times increase in essential fatty acids (EFA) content. Ó 2009 Elsevier Ltd. All rights reserved.
Keywords: Sesame oil cake Hydrocolloids Emulsifiers Fatty acid profile Rheology Microstructure
1. Introduction Many bakery products require a relatively large proportion of fat. Cakes, for example are prepared using 25–100% fat. In a cake system, fat serves three major functions, to entrap air during creaming process, to physically interfere with the continuity of starch and protein particles and to emulsify the liquid in formulation thus; fats contribute to the soft and tender eating properties required for cakes (Brooker, 1993). Elimination or replacement of a portion of the fat can lead to adverse consequences affecting the taste, texture and volume of the baked goods. Modified fat systems have to satisfy a host of physical functionality and health/nutritional requirements (Baljit, Dyal, & Narine, 2002). Such systems not only are functional, e.g., providing shortened crumb structure and foam stabilization, but also provide desirable sensory characteristics, e.g., moistness, tenderness, good bite, lubricity, and cohesiveness.
* Corresponding author. Tel.: þ91 821 2517730; fax: þ91 821 2517233. E-mail address: [email protected] (D. Indrani). 0268-005X/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodhyd.2009.02.008
Vegetable oils are normally liquid at room temperature due to the unsaturated fatty acid component of the oil. Hydrogenation of unsaturated oils results in the formation of noticeable levels of trans fatty acids. Hydrogenated shortenings are used in cake production to provide desirable attributes; however, it brings forth some concerns for people with health problems. High consumption of dietary fat is associated with both increased body fat and obesity. As the hydrogenated shortenings are saturated, they tend to raise the level of blood cholesterol and increase the risk of cardiovascular disease (Dogan, Javidipour, & Akan, 2007). Sesame oil is widely used in food industry as cooking oil, in salads, soups, confectionery etc. and as a flavoring agent in the final stages of cooking. The fatty acid composition of sesame oil includes 43% oleic and linoleic each, 9% palmitic, and 4% stearic fatty acids. It increases plasma gamma-tocopherol and enhances vitamin E activity which is believed to prevent cancer and heart disease. It is known to reduce cholesterol due to the high polyunsaturated fat content in the oil. It contains lignans, sesamin, sesamolin and sesamol of which sesamolin and sesamol have antioxidant activity and is very stable against deterioration by oxidation. Heating of sesame oil at 180 C for 4 min did not change the content of lignans, but the level of sesamol increased after heating at 180 C for 20 min (Lee, Lee, & Choe, 2007).
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The objectives of this study were to determine the effect of replacement of fat with sesame oil, hydrocolloids and emulsifiers on the rheological, microstructural, quality characteristics and fatty acid profile of cake. The results of the studies will be useful in producing cakes with 50% reduced oil and combination of emulsifier and gum, having quality characteristics similar to cake with fat and also having improved nutritional characteristics. 2. Materials and methods 2.1. Wheat flour Commercial wheat flour obtained from the local market was used for the studies. The characteristics of the flour such as moisture, ash, dry gluten, falling number, and Zeleny’s sedimentation value were determined using AACC (2000) methods. 2.2. Hydrocolloids Xanthan (EC 234-394-2) was procured from Sigma chemicals, Bangalore, India and hydroxypropylmethylcellulose (HPMC) [Methocel-K4M] was from Dow Chemical International Pvt Ltd, Mumbai, India.
transferred into a cake pan and baked at 180 C for 45 min using the oven (APV, Queensland, Australia). 2.7. Batter microscopy A thin layer of freshly prepared cake batters of the control and with different percentages of sesame oil and additives were placed on a microscope slide, and a cover slip applied. The samples were then observed under a Phase Contrast Microscope (Model BX 40, Olympus Optical Co. Ltd, Hachioji, Japan) with a magnification of 10 (Jyotsna, Sai Manohar, Indrani, & Venkateswara Rao, 2007). 2.8. Batter-specific gravity Specific gravity of cake batter was calculated by dividing the weight of a standard measure of the batter by the weight of an equal volume of water. 2.9. Batter viscosity
Glycerol monostearate (GMS) and sodium stearoyl-2-lactylate (SSL) were procured from Biocon India, Pvt Ltd, Bangalore, India.
The viscosity of cake batter was determined using a Brookfield viscometer (Model DV-III, Stoughton, M.A., U.S.A.) according to Kim and Walker (1992) with slight modifications. Cake batter was transferred to a 100 ml beaker and leveled up to the brim. The spindle speed was set to 20 rpm and spindle no. 7 was used for all experiments. The experiment was run at room temperature (28 1 C). Viscosity was measured after 5 min standing period.
2.4. Ingredients
2.10. Measurement of physical and sensory characteristics of cake
Sugar powder procured from the local market, shortening (Margarine, Hindustan Lever Ltd., Mumbai, India), baking powder, single and slow acting type, acid source sodium aluminium sulphate (Hindustan Lever Ltd.), salt, calcium propionate, glacial acetic acid (S.D. Fine Chem Ltd., Mumbai, India) and pineapple essence (Bush Boake Allen Ltd., Chennai, India) were used in these studies.
2.10.1. Cake volume Cake volume was measured by the Rapeseed displacement method (Chopin, S.A., France).
2.3. Emulsifiers
2.5. Preparation of emulsifier gel Gels were prepared using emulsifier and water in the ratio of 1:4. First dispersions were made and then dispersions under continuous agitation were heated to a temperature of 65 C for GMS and 45 C for SSL. On cooling gels were obtained. For all the experiments the gels were added in order that there was 0.5% emulsifier on wheat flour basis. 2.6. Cake formulation The following formulation for the preparation of cake was used wheat flour (100 g); shortening (60 g); sesame oil (15/30/45/60 g); crystal sugar (100 g); salt (0.5 g); baking powder (2 g); pineapple essence (0.5 ml); calcium propionate (0.3 g); glacial acetic acid (0.1 ml); water (12 ml); hydrocolloids: xanthan/HPMC (0.5 g) and emulsifier GMS/SSL (0.5 g). Wheat flour, salt, baking powder, hydrocolloids and calcium propionate were sifted thrice; sugar powder, margarine and essence were creamed for 1 min at 58 rpm, 1 min at 112 rpm and 5 min at 173 rpm. Simultaneously egg is whipped with crystal sugar and essence (both pineapple and vanilla) at 173 rpm for 7 min. Emulsifiers were added along with egg. Then whipped egg was added to the flour-fat mixture in 2–3 additions at 58 rpm. After 2 min of mixing of egg, flour-fat mixture, acetic acid and water were added and mixed at 112 rpm for 2 min. The batter temperature was 28 C. Cake batter (330 g) was
2.10.2. Cake texture Texture profile analysis of cake was performed at room temperature by using an LR-5K Texture Analyzer (Lloyd Instruments Ltd., Hampshire, England) with 5-kg load cell. The samples (4.0 4.0 2.5 cm) were compressed by using an aluminium 80 mm diameter circular disc probe. The texture parameters were determined with a cross head speed of 50 mm/min, compression distance 50% of cake’s height and 5-s delay between two bites. The data were analyzed by using Nexygen Version 4.0 Software (LR-5K) to measure cake hardness, gumminess and chewiness, as described by Bourne (1978). 2.10.3. Scanning electron microscopic (SEM) studies SEM studies were carried out using Leo scanning electron microscope Model 435 VP (Leo Electronic Systems, Cambridge, UK). Cake samples (size 20 20 mm) were defatted with hexane, followed by freeze-drying using Heto freeze-dryer Model DW3 (Allerød, Denmark). Cake samples were separately placed on the sample holder using double sided scotch tape and was exposed to gold sputtering (2 min, 2 mbar). Finally, each sample was transferred to the microscope where it was observed at 15 kV and 9.75 105 torr vacuum. 2.10.4. Sensory evaluation of cake Sensory evaluation of cakes was carried out by a panel of trained judges by assigning scores for various quality parameters namely, crust color, crust shape, crumb color, crumb grain, texture, mouthfeel for the maximum score of 10 for each parameter. The overall quality score was taken as the combined score of six quality attributes.
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2.10.5. Fatty acid composition 2.10.5.1. Fat extraction. Samples used for the studies were fat (margarine), sesame oil, cake batters (with fat, 50% sesame oil) and cakes (with fat, 50% sesame oil). The batter and the cake samples were partially dried in a vacuum oven (70 C for 3 h) and the fat was extracted in a Soxhlet apparatus using petroleum ether. Margarine was heated in an oven to get two layers of water and oil. The oil was decanted and the residual moisture in oil was removed using anhydrous sodium sulphate. The fatty acid composition of these oil samples was determined by analyzing the fatty acid methyl esters by gas–liquid chromatography. 2.10.5.2. Preparation of fatty acid methyl esters. The methyl esters were prepared by using 14% BF3/methanol (Morrison & Smith, 1964). About 50–80 mg of oil was transferred into a test tube, treated with benzene, methanol and BF3/methanol. The samples were heated, boiled for 10 min and cooled. The methyl esters were extracted using petroleum ether and the aqueous phase was discarded. The ether extract was washed with water and dried using anhydrous sodium sulphate. The solvent was evaporated, dissolved in 1 ml chloroform and taken for further work. 2.10.5.3. Thin-layer chromatography (TLC). The methyl esters were checked for complete esterification by TLC. TLC plates were coated using silica gel (silica gel for thin-layer chromatography, Ranbaxy), activated for 1 h at 105 C. The esterified samples were spotted on the plates and kept in a TLC chamber containing the solvent saturated for 1 h. The solvent system used was 80:20:1 petroleum ether:diethyl ether:glacial acetic acid. Esters gave a dark spot near the solvent front when kept in an iodine chamber. 2.10.5.4. Gas chromatography (GC). Pure fatty acid methyl esters were analyzed using a Shimadzu GC-15A (Shimadzu, Kyoto, Japan) equipped with a flame ionization detector attached to CR-4A data processor, operating under the following conditions: column: 2.4 m 0.3 cm stainless steel packed with 15% diethylene glycol succinate (DEGS) coated on chromosorb W (60-80 mesh); column temperature 180 C; injector temperature 220 C; detector temperature: 240 C; carrier gas, nitrogen at a flow rate of 40 ml/ min. The peaks were identified by comparing the retention time with standard 18:0 and reported as relative percentage of individual fatty acids. 2.11. Statistical analysis Data were statistically analyzed using ANOVA with different experimental groups appropriate to the completely randomized design with four replicates each. The experimental groups were then separated statistically using Duncan’s new multiple range tests, as described by Steel and Torrie (1960). 3. Results and discussion 3.1. Quality of wheat flour The wheat flour had 0.53% total ash, 9.5% dry gluten, 444 s falling number and 20 ml of Zeleny’s sedimentation value. 3.2. Cake making characteristics 3.2.1. Effect of replacement of fat with different levels of sesame oil on the physical characteristics of cake 3.2.1.1. Batter microscopy. Fig. 1A is the photomicrograph of control cake batter made with fat in which some solid in the form of flour
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and starch can be seen. Small and medium sized air bubbles distributed throughout the batter can be observed. In Fig. 1B which is the photomicrograph of cake batter with 25% sesame oil, predominantly large air bubbles could be seen. Medium and small sized air bubbles could be observed in the photomicrograph of batter with 50% sesame oil (Fig. 1C). In the photomicrograph of batter with 75% sesame oil (Fig. 1D) more number of small air bubbles along with medium sized air cells can be seen. Few large and small air bubbles (Fig. 1E) can be seen in photomicrograph of cake batter containing 100% sesame oil and the number of air cells seems to be less. The shortening used in the cakes plays a predominant role in determining the structure (Hartnett & Thalheimer, 1979). It has been demonstrated that dispersion of plastic fat into globules throughout the batter and the ability of the fat to incorporate air were directly related to volume and grain in the finished products. Hence, liquid oils without the ability to incorporate air produced low volume and poor grain. 3.2.1.2. Batter viscosity and specific gravity. Batters of control cake with fat and cakes containing 25, 50, 75 and 100% sesame oil were analyzed for physical characteristics like viscosity and specific gravity. The results are given in Table 1. The viscosity of control batter containing 100% fat after a standing period of 5 min was 28,800 cP. It decreased to 16,000, 14,400, 12,800 and 11,200 cP when 100% fat was replaced with 25, 50, 75 and 100% sesame oil respectively. The specific gravity of control batter was 0.78 g/cc which on addition of increasing amounts of sesame oil from 25 to 100% increased it from 0.89 to 1.04 g/cc. The above results indicate that when compared to fat, sesame oil decreases the cake batter viscosity and increases specific gravity due to less air incorporation. Air incorporation depends both on the aeration process (beater speed and design) and on the physico-chemical properties of the batter (viscosity and surface tension), which are determined by formulation (Sahi & Alava, 2003). 3.2.1.3. Cake volume and moisture. Effect of replacement of fat with different levels of sesame oil on cake volume and moisture is presented in Table 1. Control cake with 100% fat showed the highest volume (805 cm3/330 g) and replacement of fat with increasing addition of sesame oil from 25 to 100% decreased the volume from 770 to 645 cm3/330 g. As sesame oil content increased from 25 to 100%, the moisture content decreased from 21.1 to 20.3%; this is due to decrease in retention of water in the cakes containing sesame oil. The above results indicate that the nature of the batter with sesame oil having lower viscosity and higher specific gravity resulted in low volume. Shelke, Faubion, and Hoseney (1990) also suggested that lower viscosity of the batter during heating is one of reason for decreased end product volume. It is possible that, in the presence of a less viscous batter, carbon dioxide evolved and water vapor produced might not be trapped in the air cells during baking, thus resulting in the cakes with low volume. 3.2.1.4. Cake texture. Fig. 2 represents influence of sesame oil on the texture of cakes. Hardness value for control cake with fat was 16.4 N. Replacement of fat with increasing amount of sesame oil from 25 to 100% significantly increased the hardness values from 20.2 to 28.7 N. The gumminess value for control cake was 6.8 N, 25% sesame oil (8.5 N), 50% sesame oil (9.0 N), 75% sesame oil (10.5 N) and 100% sesame oil (11.7 N). The chewiness value of cake with 25% sesame oil was 90.7 N mm, 50% sesame oil (95.1 N mm), 75% sesame oil (108.8 N mm) and 100% sesame oil (126.4 N mm) as against control (65.5 N mm). The above results indicate that replacement of fat with sesame oil at all levels tried adversely affected the texture of cake.
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Fig. 1. Photomicrographs of cake batter (magnification 10). A – control; B – 25% SO; C – 50% SO; D – 75% SO; E –100% SO; F – 50% SO þ xanthan; G – 50% SO þ HPMC; H – 50% SO þ GMS; I – 50% SO þ SSL; J – 50% SO þ HPMC þ SSL. SO – sesame oil; GMS – glycerol monostearate; SSL – sodium steoryl-2-lactylate; HPMC – hydroxypropylmethylcellulose.
3.2.1.5. Sensory characteristics of cake. Increase in sesame oil percentage from 25 to 100% resulted in decrease in sensory scores (Table 1) for crust color and shape i.e. the crust color became dark and the crust shape showed tendency to become flat. Yellowness Table 1 Effect of replacement of fat with different levels of sesame oil on quality characteristicsb of cake. Parameters
Controla
25
50
75
100
Batter viscosityc (cP) Batter-specific gravity (g/cc) Volume (cm3/330 g of batter) Moisture (%) Crust color (10) Crust shape (10) Crumb color (10) Crumb grain (10) Texture (10) Mouthfeel (10) Overall quality score (60)
28,800e 0.78a
16,000d 0.89b
14,400c 0.91c
12,800b 1.01d
11,200a 1.04e
5.5 0.01
805e
770d
730c
665b
645a
10
21.6c 9c 9d 9d 9c 9e 9e 54e
21.1b 8.5b 8c 8c 8b 8d 8d 48.5d
20.9b 8b 7b 6b 8b 7c 7c 43c
20.6a 7a 7b 6b 6a 6b 6.5b 38.5b
20.3a 6.5a 6a 5a 6a 5a 5a 33.5a
0.2 0.03 0.02 0.02 0.04 0.02 0.03 0.50
a b c d
SEMd ()
Sesame oil (%)
Control cake contains 60 g of fat/100 g flour. Means in the same row followed by different letter differ significantly (p 0.05). Viscosity measured after a standing period of 5 min using Brookfield viscometer. Standard error of the mean at 15 degrees of freedom.
increased with increase in the sesame oil content. The sensory score for crumb grain decreased as the grain showed thick cell walled, compact cells. Control cakes showed soft texture while cakes with sesame oil were firm and the firmness increased with increase in sesame oil from 25 to 100%. This is reflected in the increase in the hardness values (Fig. 2) of cakes with different levels of sesame oil measured using Instron. The mouthfeel indicated that the cakes with sesame oil were chewy and also showed lump formation at 75 and 100% sesame oil level. When compared to other cake samples, cakes with 100% sesame oil showed unacceptable, dominating oily smell. The overall quality score of control cake with fat was 54 and cake with 100% sesame oil was 33.5 for the maximum score of 60. 3.2.1.6. Microstructure of cake. Fig. 3A–E represents the micrographs of cake crumb with different percentages of sesame oil. Fig. 3A is the micrograph of control cake crumb prepared with fat entirely. It shows a continuous gluten matrix with one or two partial outlines of starch granules embedded in the matrix. The starch granules have lost their shape owing to gelatinization. The protein components of wheat flour have been described as network covering the starch granules in earlier studies by Aranyi and Hawrylewicz (1969). Hoseney (1985) also observed in mixed wheat flour dough and reported that it is a random mixture of protein fibrils with adhering starch granules. Fig. 3B which is the micrograph of cake crumb with 25% sesame oil, a rather
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Fig. 2. Effect of different levels of sesame oil and additives on texture profile analysis of cakes. SO – sesame oil; GMS – glycerol monostearate; SSL – sodium steoryl-2-lactylate; HPMC – hydroxypropylmethylcellulose.
ruptured, discontinuous, gluten protein matrix can be seen. Hsu, Gordon, and Davis (1980) stated that in cakes prepared with oil, the matrix appears as lakes that assume irregular shape around starch granules. They also opined that the matrix components most likely are proteins, lipids and solubilized starch. At 50% sesame oil level, the cake crumb micrograph showed slightly more continuous gluten matrix (Fig. 3C) than the micrograph of cake crumb with 25% sesame oil. No starch granules could be observed in the micrographs of cake crumb made with 75% sesame oil (Fig. 3D) or 100% sesame oil (Fig. 3E); the gluten protein matrix appeared discontinuous and most of the starch granules were gelatinized. 3.2.2. Effect of replacement of fat with 50% sesame oil and hydrocolloids on physical characteristics of cakes 3.2.2.1. Batter microscopy. Rusch (1981) stated that various film forming properties in batter form the wall of the foam cell. Integrity of these walls determines the cake volume and uniformity of appearance. Only few number of medium and small air cells can be seen in the photomicrograph of cake batter with 50% sesame oil and xanthan (Fig. 1F). Fig. 1G representing the photomicrograph of cake batter with 50% sesame oil and HPMC shows large, medium and small sized air cells. 3.2.2.2. Batter viscosity and specific gravity. Effect of replacement of fat with 50% sesame oil and hydrocolloids such as xanthan and HPMC separately at the level of 0.5% is presented in Table 2. The specific gravity of control batter was 0.78 g/cc, 50% sesame oil (0.91 g/cc), xanthan (1.06 g/cc) and HPMC (0.88 g/cc). This shows that cake batter with xanthan was heavier than all other samples. Addition of HPMC decreased the specific gravity from 0.91 to 0.88 g/cc indicating improvement in the batter characteristics of cake with 50% sesame oil. Addition of hydrocolloids like xanthan and HPMC to the cake with 50% sesame oil increased the batter viscosity from 14,400 to 25,600 and 20,200 cP respectively. Generally, addition of hydrocolloids increases the viscosity of cake batter due to their water binding capacity. Batter containing xanthan showed the highest viscosity
which was attributed to the high water holding capacity of xanthan and also due to xanthan’s unique, rod-like conformation, which is more responsive to shear than a random-coil conformation (Urlacher & Noble, 1997). Xanthan has a cellulosic backbone which is rendered water soluble by the presence of trisaccharide branches attached to every second glucose unit in the main chain (Sanderson, 1981). It is completely soluble in hot or cold water, turning into a very viscous solution even if the concentration is small. According to Gomez, Ronda, Caballero, Blanco, and Rosell (2006), the influence of hydrocolloids on the final cake volume is due to increase in batter viscosity that slows down the rate of gas diffusion and allows its retention during the early stages of baking. 3.2.2.3. Cake volume and moisture. Among the two hydrocolloids tried, HPMC showed significant improvement in the volume of cake with 50% sesame oil from 730 to 850 cm3/330 g of batter while addition of xanthan decreased it (Table 2). According to Bell (1990) HPMC forms interfacial films at the boundaries of the gas cells that confer some stability to the cells against the gas expansion and processing condition changes. The moisture content of cakes also increased with addition of hydrocolloids. The increase in the moisture content in cake with HPMC and xanthan explains the ability of hydrocolloids to hydrate at room temperature; and its self-interactions without competing with gluten proteins and starchy polysaccharides for the water available in the system (Leon et al., 2000). 3.2.2.4. Cake texture. Fig. 2 represents influence of sesame oil and hydrocolloids on the texture of cakes. Hardness, gumminess and chewiness values for control cake with fat were 16.4 N, 6.8 N mm and 65.5 N mm. Replacement of fat with 50% sesame oil and xanthan significantly increased these parameters to 31.3 N, 13.8 N mm, 140.1 N mm while HPMC reduced these to 15.1 N, 5.8 N mm and 58.5 N mm respectively. The above results indicate that addition of HPMC is beneficial in improving the texture of cake with 50% sesame oil. According to Rosell, Rojas, and de Barber (2001), xanthan gum can provoke a crumb firmness increase probably due to the thickening of the crumb cells
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Fig. 3. Microstructure of cake crumb (magnification 1000). A – control; B – 25% SO; C – 50% SO; D – 75% SO; E – 100% SO; F – 50% SO þ xanthan; G – 50% SO þ HPMC; H – 50% SO þ GMS; I – 50% SO þ SSL; J – 50% SO þ HPMC þ SSL. PM – protein matrix; SG – starch granule; WSG – wrapped starch granule.
surrounding the air spaces. Firmness increase may also be a result of molecular entanglements between xanthan and gluten proteins, possibly enhanced by ionic interactions due to carboxylate groups on the polysaccharide. Furthermore, xanthan addition can also amplify wheat starch granules swelling during heating but it can also increase their rigidity (Mandala & Bayas, 2004), which can influence negatively the final bread firmness when its concentration increases. 3.2.2.5. Sensory characteristics of cake. Effect of replacement of fat with 50% sesame oil and hydrocolloids on sensory characteristics of cake is presented in Table 2. The results showed that the cakes with xanthan had yellowish crumb color, closed crumb grain, firmer texture and exhibited higher degree of chewiness than the cakes with 50% sesame oil. This is indicated by the decrease in the sensory scores for crumb color, crumb grain, texture and mouthfeel. On the contrary, addition of HPMC significantly increased the sensory scores of these characteristics of cake with 50% sesame oil. It is interesting to note that the above quality characteristics not only improved but also were better than the control cake with 100% fat. This is indicated by the overall quality score of 55 when compared to 54 of control cake.
3.2.2.6. Microstructure of cake. In Fig. 3F which is the micrograph of cake crumb with 50% sesame oil and xanthan, partial outlines of a few of starch granules can be seen. Chaisawang and Suphantharika (2006) stated that in SEM micrographs of tapioca, xanthan totally wrapped the native starch granules. In our SEM study, the wheat starch granules seemed to be wrapped by xanthan as the granules are not visible and only a veil-like gluten matrix can be seen. A few partial outlines of starch granules entrapped in protein matrix can be observed in Fig. 3G which is the micrograph of cake crumb with 50% sesame oil and HPMC. Barcenas and Rosell (2005) opined that microstructure of bread crumb containing HPMC showed a smooth structure with less number of cavities. They also stated that HPMC enfolds all the other bread constituents. A similar effect could be observed in the microstructure of cake crumb with HPMC. 3.2.3. Effect of emulsifiers on the physical characteristics of cake with 50% sesame oil 3.2.3.1. Batter microscopy. In the photomicrograph of cake batter with 50% sesame oil and GMS (Fig. 1H), a few large, medium and fine air cells can be seen. Fig. 1I is the photomicrograph of cake batter with 50% sesame oil and SSL in which large and many number of
M. Sowmya et al. / Food Hydrocolloids 23 (2009) 1827–1836 Table 2 Effect of hydrocolloids on quality characteristicsc of cake with 50% sesame oil. Parameters
Batter viscosityd (cP) Batter-specific gravity (g/cc) Volume (cm3/330 g of batter) Moisture (%) Crust color (10) Crust shape (10) Crumb color (10) Crumb grain (10) Texture (10) Mouthfeel (10) Overall quality (60) a b c d e
Controla
50% Sesame oil
SEMe ()
50% Sesame oil
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Table 3 Effect of emulsifiers on quality characteristicsb of cake with 50% oil. Parameters
Controla
Hydrocolloids (0.5%)
50% Sesame oil
b
Xanthan
HPMC
28,800d 0.78a
14,400a 0.91c
25,600c 1.06d
20,200b 0.88b
60 0.01
805c
730ab
710a
850d
10
21.6b 9b 9b 9c 9c 9b 9c 54c
20.9a 8a 7a 6b 8b 7a 7b 43b
23.5d 8a 7a 5a 6.5a 7.5a 6a 40a
22.8c 9b 9b 9c 9c 9.5c 9.5d 55d
0.20 0.03 0.04 0.02 0.03 0.04 0.02 0.45
Control cake contains 60 g of fat/100 g flour. HPMC – hydroxypropylmethylcellulose. Means in the same row followed by different letter differ significantly (p 0.05). Viscosity measured after a standing period of 5 min using Brookfield viscometer. Standard error of the mean at 12 degrees of freedom.
small air cells evenly distributed are seen. According to Ellinger (1962) hydrophilic emulsifiers promote the uniform dispersion of minute fat particles and their entrapped air cells in a cake batter, thereby creating a large number of sites where the water vapor can expand during the baking stage. Expansion of water vapor occurs only within the fat-entrapped air cells. Excessively large and buoyant air bubbles tend to rise out of the batter, this results in a coarse-grained cake of low volume. Contrariwise, the smaller the individual air cells are, the larger will be the cake volume and the finer its grain. However, Jyotsna, Prabhasankar, Indrani, and Venkateswara Rao (2004) reported that in the photomicrograph of cake batter with fat and SSL gel, the number of air cells was decreased and most of the entrapped air cells were of smaller size with non-uniform distribution. According to Wootton, Howard, Martin, McOsker, and Holme (1967), the emulsifiers provide protection to protein-film cell walls. The emulsifiers also coat the exterior of fat particles so that the surface of the particle is no longer disruptive to the protein film. 3.2.3.2. Batter viscosity and specific gravity. Effect of replacement of fat with 50% sesame oil and emulsifiers on the physical characteristics of cake is presented in Table 3. The results showed that addition of GMS and SSL increased the batter viscosity of cake with 50% sesame oil from 14,400 cP to 16,200 and 18,200 cP respectively. The batter-specific gravity decreased with addition of emulsifiers. According to Pyler (1988) emulsifiers aid the incorporation and sub division of air into the liquid phase to promote foam formation and also promote uniform dispersion of fat which contains entrapped air cells and thereby giving more sites for the expansion of gas resulting in greater volume and soft texture. 3.2.3.3. Cake volume and moisture. The volume increased significantly with emulsifiers (Table 3) however among two emulsifiers tried, SSL showed the highest improvement in volume of 860 ml followed by GMS (840 ml) and control cake with fat (805 ml). Addition of GMS and SSL increased the moisture content of cake with 50% sesame oil.
Batter viscosityc (cP) Batter-specific gravity (g/cc) Volume (cm3/330 g of batter) Moisture (%) Crust color (10) Crust shape (10) Crumb color (10) Crumb grain (10) Texture (10) Mouthfeel (10) Overall quality (60) a b c d e
SEMd ()
Emulsifiers (0.5%) GMSe
SSLe
28,800b 0.78a
14,400a 0.91c
16,200c 0.84b
18,200d 0.83b
45 0.001
805b
730a
840c
860d
10
21.6b 9b 9c 9c 9c 9b 9c 54d
20.9a 8a 7a 6a 8a 7a 7a 43a
22.0a 9b 8.5b 8.5b 8.5b 9b 8.5b 52b
22.5c 8.5a 8b 8.5b 9.5d 9.5c 9.5c 53.5c
0.25 0.03 0.04 0.02 0.03 0.02 0.03 0.45
Control cake contains 60 g of fat/100 g flour. Means in the same row followed by different letter differ significantly (p 0.05). Viscosity measured after a standing period of 5 min using Brookfield viscometer. Standard error of the mean at 12 degrees of freedom. GMS – glycerol monostearate; SSL – sodium stearoyl-2-lactylate.
cake with 50% sesame oil and GMS was 16.0 N, SSL (15.5 N) as against control 16.4 N. Gumminess and chewiness of cake with 50% sesame oil and GMS were 6.5 N mm, 62.5 N mm, SSL (6.0 N mm and 60.2 N mm) as against control (6.8 N mm and 65.5 N mm) and cake with 50% sesame oil (9.0 N mm and 95.1 N mm). Addition of GMS and SSL significantly improved the texture of cake with 50% sesame oil but the improvement brought about by SSL was higher than GMS. 3.2.3.5. Effect of emulsifiers on sensory characteristics of cake with 50% oil. Sensory evaluation of cake showed that addition of emulsifiers to cakes with 50% sesame oil significantly increased the overall quality score of cake. The overall quality score for control cake was 54, cake with 50% sesame oil, 43 and it increased to 52.0 with GMS and 53.5 with SSL as shown in Table 3. The above results indicate that addition of emulsifiers increased the overall quality score of cake with 50% sesame oil. However the improvement in the overall score of cake with 50% sesame oil brought about by SSL was highest. The above results indicate that among the two emulsifiers tried, SSL significantly improved the quality of cake with 50% sesame oil. The volume and texture of cake with SSL were better than the control cake. Table 4 Effect of replacement of fat with 50% sesame oil, HPMC and SSL on quality characteristicsb of cake. Parameters
Controla
50% Sesame oil
50% Sesame oil þ HPMCe þ SSLe
SEMd ()
Batter viscosityc (cP) Batter-specific gravity (g/cc) Volume (cm3/330 g of batter) Moisture (%) Crust color (10) Crust shape (10) Crumb color (10) Crumb grain (10) Texture (10) Mouthfeel (10) Overall quality (60)
28,800c 0.78a
14,400a 0.91c
20,800b 0.80b
50 0.001
805b
730a
880c
15
21.6b 9b 9b 9b 9b 9b 9b 54b
20.9a 8a 7a 6a 8a 7a 7a 43a
23.5c 9.5c 9.5c 9b 9.5c 9.5c 9.5c 56c
0.25 0.04 0.03 0.02 0.02 0.03 0.02 0.30
a
3.2.3.4. Effect of emulsifiers on the texture profile analysis of cake with 50% sesame oil. Fig. 2 shows that addition of GMS and SSL lowered the hardness, gumminess and chewiness values of control cake with fat and cake with 50% sesame oil. The hardness value of
50% of Sesame oil
Control cake contains 60 g of fat/100 g flour. Means in the same row followed by different letter differ significantly (p 0.05). c Viscosity measured after a standing period of 5 min using Brookfield viscometer. d Standard error of the mean at 9 degrees of freedom. e HPMC – hydroxypropylmethylcellulose; SSL – sodium stearoyl-2-lactylate at (0.5%). b
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Fig. 4. Photograph of cakes. A – control; B – 50% sesame oil; C – 50% sesame oil þ HPMC þ SSL.
3.2.3.6. Microstructure of cake. Fig. 3H represents micrograph of cake crumb with 50% sesame oil treated with GMS. The micrograph shows partial outlines of a couple of starch granules enmeshed in protein matrix. A few starch granules trapped in protein matrix can be seen in micrograph (Fig. 3I) of cake crumb with 50% sesame oil and SSL. Evans, Volpe, and Zabik (1977) stated that in the ultra structure of bread dough with SSL, the gluten sheet in the dough was extremely thin, intact and translucent in many areas. Starch granules silhouettes were visible beneath the veiling proteins. The proteins draped finely over the mass of granules. A similar effect can be seen in our SEM studies. 3.2.4. Effect of replacement of fat with 50% sesame oil, HPMC and SSL on physical characteristics of cake 3.2.4.1. Batter microscopy. Fig. 1J represents the cake batter with 50% sesame oil, HPMC and SSL. The photomicrograph shows medium and small uniform cells distributed throughout the batter when compared to the medium and small sized bubbles unevenly distributed in the cake batter of 50% sesame oil (Fig. 1C). 3.2.4.2. Batter viscosity and specific gravity. Cake batter with 50% sesame oil and HPMC and SSL showed higher viscosity of 20,800 cP and specific gravity (0.80) lower than the cake with 50% sesame oil (0.91) as shown in Table 4. 3.2.4.3. Cake volume and moisture. Table 4 shows the effect of combination of HPMC and SSL on moisture and volume of cake with 50% sesame oil. It showed highest moisture (23.5%) and volume (880 ml) and lower specific gravity (0.80 g/cc) than the cake with 50% sesame oil. The volume of cake with 50% sesame oil, HPMC and SSL was better than control as seen in Fig. 4.
3.2.4.4. Effect of HPMC and SSL on the texture profile analysis of cake with 50% sesame oil. Fig. 2 shows the texture profile analysis of cake with 50% sesame oil and HPMC and SSL. Cake with 50% sesame oil and HPMC and SSL had the least hardness value of 14.1 N, gumminess value of 5.4 N and chewiness value of 57.3 N mm, indicating improved texture profile than control. 3.2.4.5. Effect of combination of hydrocolloids and emulsifiers on sensory characteristics of cake with 50% sesame oil. Sensory evaluation of cake with 50% sesame oil and combination of HPMC and SSL as given in Table 4 showed that use of HPMC and SSL improved the crust color and shape, crumb grain, texture and mouthfeel of the cake with 50% sesame oil. This is reflected in the significant increase in the overall quality score from 43 to 56. The improvement was so significant that the quality characteristics of cake with 50% sesame oil and HPMC and SSL were better than control cake with fat. 3.2.4.6. Microstructure of cake. Fig. 3J which represents the micrograph of cake crumb with 50% sesame oil, HPMC and SSL, a continuous gluten matrix with no ruptures can be observed. 3.3. Fatty acid composition Fatty acids play an important role in human diet. The fatty acid composition in Table 5 shows that the major fatty acid in fat (commercial margarine) is palmitic (44.2%) followed by oleic acid (33.5%). The trans fatty acid (TFA) content of margarine has been reported earlier. The TFA content of margarine used for cake preparation was 18.5% (Yella Reddy & Jeyarani, 2001). It also contains lauric, myristic, stearic and linoleic acid. The high palmitic acid content indicated that palm oil or palm stearin is the major
Table 5 Fatty acid composition (%) of fat, sesame oil, batter and cake samples. Samples
12:0
14:0
16:0
16:1
18:0
18:1
18:2
P
Fat Sesame oil Batter with fat Batter with sesame oil Cake with fat Cake with sesame oil
9.1 2.3 0 5.1 0.5 0.1 5.5 0.8 0.2 0.1
5.1 0.8 0 3.6 0.2 0.1 3.9 0.7 0.3
44.2 0.42 10.8 0.8 39.1 0.7 12.1 0.7 41.4 1.6 17.4 0.8
0 0 0.6 0.1 0.4 0.1 0.6 0.4 1.3 0.4
3.9 0.6 5.7 0.1 4.9 0.1 6.2 0.2 4.4 0.5 5.4 0.3
33.5 2.8 43.0 0.5 41.1 0.7 43.0 0.3 38.8 2.2 42.7 0.7
3.5 0.8 40.1 0.8 5.5 0.1 37.6 0.5 5.5 0.6 32.6 0.5
63.0 16.5 52.6 18.5 55.2 23.3
SFA
P
USFA
37.0 83.1 47.4 81.0 44.9 76.6
SFA – saturated fatty acid; USFA – unsaturated fatty acid; 12:0 – lauric acid; 14:0 – myristic acid; 16:0 – palmitic acid; 16:1 – palmitoleic acid; 18:0 – stearic acid; 18:1 – oleic acid.
M. Sowmya et al. / Food Hydrocolloids 23 (2009) 1827–1836
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Fig. 5. Gas chromatogram of fatty acid methyl esters of oil extracted from cakes prepared using (A) fat (margarine) and (B) after replacing fat with sesame oil. 12:0 – lauric acid; 14:0 – myristic acid; 16:0 – palmitic acid; 16:1 – palmitoleic acid; 18:0 – stearic acid; 18:1 – oleic acid; 18:2 – linoleic acid.
ingredient used for the hydrogenated fat. The content of palmitic and myristic acids which elevate blood cholesterol (Zock, De Vries, & Katan, 1994) was significantly high (49.3%). The total saturated fatty acid (SFA) content was 63%. Sesame oil contained only 16.5% SFA and also contained 43% mono unsaturated fatty acid (MUFA) and 40.4% polyunsaturated fatty acid (PUFA). When compared with the cakes prepared using the fat and after replacing with sesame oil, the cakes prepared using the fat contained 55.2% SFA while the cake prepared using sesame oil contained only 23.3% SFA as shown in Table 5. Fig. 5 shows the GC profile of these samples indicating the reduction in palmitic acid and increase in linoleic acid content. On replacing the fat using sesame oil, the palmitic acid which is reported to increase the blood cholesterol decreased from 41.4 to 17.4% and the essential fatty acid (EFA) content increased from 5.5% to 32.6%. Thus the product contains nutritionally superior fatty acids as there was 2.4 times decrease in palmitic acid content and 5.9 times increase in EFA content. 4. Conclusions Total replacement of fat with different levels of sesame oil showed that increase in sesame oil content decreased batter viscosity, cake volume and overall quality score. HPMC and SSL improved the overall quality score of the cake with 50% sesame oil. Combination of HPMC and SSL in cake with 50% sesame oil showed results better than the control cake. On replacing the fat with 50% sesame oil, there was a decrease in saturated fatty acid content and
increase in linoleic acid. The fatty acid profile of cake with 50% sesame oil was better than the control cake as there was 2.4 times decrease in palmitic acid content and 5.9 times increase in EFA content. The results presented in this paper have shown that reduced fat, nutritionally superior cakes with quality characteristics better than control can be prepared by replacing fat with 50% sesame oil and using combination of additives like HPMC and SSL. These results should be useful for the production of nutritious cakes by the baking industry on a large scale. Acknowledgements The authors are greatly indebted to Mr. K. Anbalagan, CIFS, CFTRI, Mysore for his help in carrying out scanning electron microscopy. References American Association of Cereal Chemists (AACC). (2000). Approved methods of American Association of Cereal Chemists (9th ed.).. St. Paul, Minnesota: moisture (44-15), ash (08-01), gluten (38-10), Zeleny’s sedimentation value (56-60), falling number (56-81B). Aranyi, C., & Hawrylewicz, E. J. (1969). Application of scanning electron microscopy to cereal specimens. Cereal Science Today, 14, 230–233, 253. Baljit, S. G., Dyal, S. D., & Narine, S. S. (2002). Lipid shortenings: a review. Food Research International, 35, 1015–1047. Barcenas, M. E., & Rosell, C. M. (2005). Effect of HPMC on the microstructure, quality and aging of wheat bread. Food Hydrocolloids, 19, 1037–1043. Bell, D. A. (1990). Methylcellulose as structure enhancer in bread baking. Cereal Foods World, 35, 1001–1006. Bourne, M. C. (1978). Texture profile analysis. Food Technology, 32, 62–66, 72.
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Brooker, B. E. (1993). The stabilization of air in cake battersdthe role of fat. Food Structure, 12, 285–296. Chaisawang, M., & Suphantharika, M. (2006). Pasting and rheological properties of native and anionic tapioca starches as modified by guar gum and xanthan gum. Food Hydrocolloids, 20, 641–649. Dogan, I. S., Javidipour, I., & Akan, T. (2007). Effects of interesterified palm and cottonseed oil blends on cake quality. International Journal of Food Science and Technology, 42, 157–164. Ellinger, R. H. (1962). The development and uses of fluid shortenings. Baker’s Digest, 3, 65. Evans, L. G., Volpe, T., & Zabik, M. E. (1977). Ultrastructure of bread dough with yeast single cell protein and or emulsifier. Journal of Food Science, 42, 70–74. Gomez, M., Ronda, F., Caballero, P. A., Blanco, C. A., & Rosell, C. M. (2006). Functionality of different hydrocolloids on the quality and shelf-life of yellow layer cakes. Food Hydrocolloids, 21, 167–173. Hartnett, D. I., & Thalheimer, W. G. (1979). Use of oil in baked products – part II: sweet goods and cakes. Journal of the American Oil Chemists’ Society, 56, 948–952. Hoseney, R. C. (1985). The mixing phenomenon. Cereal Foods World, 30, 453– 457. Hsu, E. E., Gordon, J., & Davis, E. A. (1980). Water loss rates and scanning electron microscopy of model cake systems made with different emulsification systems. Journal of Food Science, 45, 1243–1255. Jyotsna, R., Prabhasankar, P., Indrani, D., & Venkateswara Rao, G. (2004). Improvement of rheological and baking properties of cake batters with emulsifier gels. Journal of Food Science, 69, 16–19. Jyotsna, R., Sai Manohar, R., Indrani, D., & Venkateswara Rao, G. (2007). Effect of whey protein concentrate on the rheological and baking properties of eggless cake. International Journal of Food Properties, 10, 599–606. Kim, C. S., & Walker, C. E. (1992). Interactions between starches, sugar and emulsifiers in high ratio cake model systems. Cereal Chemistry, 69, 206– 212. Lee, J. Y., Lee, Y., & Choe, E. (2007). Effects of sesamol, sesamin, and sesamolin extracted from roasted sesame oil on the thermal oxidation of methyl linoleate. LWT – Food Science and Technology. doi:10.1016/j.lwt.2007.11.019.
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Effect of replacement of fat with sesame oil and additives on rheological, microstructural, quality characteristics and fatty acid profile of cakes M. Sowmya a, T. Jeyarani b, R. Jyotsna a, D. Indrani a, * a b
Flour Milling, Baking and Confectionery Technology Department, Central Food Technological Research Institute, Mysore 570 020, Karnataka, India Lipid Science and Traditional Foods Department, Central Food Technological Research Institute, Mysore 570 020, Karnataka, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 25 August 2008 Accepted 2 February 2009
Effect of replacement of fat with 25, 50, 75 and 100% sesame oil (on fat basis); 50% sesame oil, hydrocolloids and emulsifiers on the rheological, microstructural, quality characteristics and fatty acid profile of cake was studied. Addition of increasing amount of sesame oil decreased viscosity, increased specific gravity of cake batter; decreased cake volume and overall quality score. Microstructure studies showed disrupted gluten matrix. Among the two different hydrocolloids [hydroxypropylmethylcellulose (HPMC) and xanthan] and emulsifiers [glycerol monostearate (GMS) and sodium stearoyl-2-lactylate (SSL)] tried, HPMC and SSL increased the batter viscosity, decreased the specific gravity, increased the volume and overall quality score. Use of combination of HPMC and SSL improved significantly the quality characteristics of cake with 50% sesame oil in such a way that the overall quality score was higher than that of the control cake with fat. The microstructure of cake crumb with 50% sesame oil and HPMC showed a smooth structure with less number of cavities and SSL showed a continuous protein matrix. On replacing the fat with 50% sesame oil, there was a decrease in saturated fatty acids and increase in unsaturated fatty acids, particularly linoleic acid. The fatty acid profile of cake with 50% sesame oil was better than the control cake as there was 2.4 times decrease in palmitic acid content and 5.9 times increase in essential fatty acids (EFA) content. Ó 2009 Elsevier Ltd. All rights reserved.
Keywords: Sesame oil cake Hydrocolloids Emulsifiers Fatty acid profile Rheology Microstructure
1. Introduction Many bakery products require a relatively large proportion of fat. Cakes, for example are prepared using 25–100% fat. In a cake system, fat serves three major functions, to entrap air during creaming process, to physically interfere with the continuity of starch and protein particles and to emulsify the liquid in formulation thus; fats contribute to the soft and tender eating properties required for cakes (Brooker, 1993). Elimination or replacement of a portion of the fat can lead to adverse consequences affecting the taste, texture and volume of the baked goods. Modified fat systems have to satisfy a host of physical functionality and health/nutritional requirements (Baljit, Dyal, & Narine, 2002). Such systems not only are functional, e.g., providing shortened crumb structure and foam stabilization, but also provide desirable sensory characteristics, e.g., moistness, tenderness, good bite, lubricity, and cohesiveness.
* Corresponding author. Tel.: þ91 821 2517730; fax: þ91 821 2517233. E-mail address: [email protected] (D. Indrani). 0268-005X/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodhyd.2009.02.008
Vegetable oils are normally liquid at room temperature due to the unsaturated fatty acid component of the oil. Hydrogenation of unsaturated oils results in the formation of noticeable levels of trans fatty acids. Hydrogenated shortenings are used in cake production to provide desirable attributes; however, it brings forth some concerns for people with health problems. High consumption of dietary fat is associated with both increased body fat and obesity. As the hydrogenated shortenings are saturated, they tend to raise the level of blood cholesterol and increase the risk of cardiovascular disease (Dogan, Javidipour, & Akan, 2007). Sesame oil is widely used in food industry as cooking oil, in salads, soups, confectionery etc. and as a flavoring agent in the final stages of cooking. The fatty acid composition of sesame oil includes 43% oleic and linoleic each, 9% palmitic, and 4% stearic fatty acids. It increases plasma gamma-tocopherol and enhances vitamin E activity which is believed to prevent cancer and heart disease. It is known to reduce cholesterol due to the high polyunsaturated fat content in the oil. It contains lignans, sesamin, sesamolin and sesamol of which sesamolin and sesamol have antioxidant activity and is very stable against deterioration by oxidation. Heating of sesame oil at 180 C for 4 min did not change the content of lignans, but the level of sesamol increased after heating at 180 C for 20 min (Lee, Lee, & Choe, 2007).
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The objectives of this study were to determine the effect of replacement of fat with sesame oil, hydrocolloids and emulsifiers on the rheological, microstructural, quality characteristics and fatty acid profile of cake. The results of the studies will be useful in producing cakes with 50% reduced oil and combination of emulsifier and gum, having quality characteristics similar to cake with fat and also having improved nutritional characteristics. 2. Materials and methods 2.1. Wheat flour Commercial wheat flour obtained from the local market was used for the studies. The characteristics of the flour such as moisture, ash, dry gluten, falling number, and Zeleny’s sedimentation value were determined using AACC (2000) methods. 2.2. Hydrocolloids Xanthan (EC 234-394-2) was procured from Sigma chemicals, Bangalore, India and hydroxypropylmethylcellulose (HPMC) [Methocel-K4M] was from Dow Chemical International Pvt Ltd, Mumbai, India.
transferred into a cake pan and baked at 180 C for 45 min using the oven (APV, Queensland, Australia). 2.7. Batter microscopy A thin layer of freshly prepared cake batters of the control and with different percentages of sesame oil and additives were placed on a microscope slide, and a cover slip applied. The samples were then observed under a Phase Contrast Microscope (Model BX 40, Olympus Optical Co. Ltd, Hachioji, Japan) with a magnification of 10 (Jyotsna, Sai Manohar, Indrani, & Venkateswara Rao, 2007). 2.8. Batter-specific gravity Specific gravity of cake batter was calculated by dividing the weight of a standard measure of the batter by the weight of an equal volume of water. 2.9. Batter viscosity
Glycerol monostearate (GMS) and sodium stearoyl-2-lactylate (SSL) were procured from Biocon India, Pvt Ltd, Bangalore, India.
The viscosity of cake batter was determined using a Brookfield viscometer (Model DV-III, Stoughton, M.A., U.S.A.) according to Kim and Walker (1992) with slight modifications. Cake batter was transferred to a 100 ml beaker and leveled up to the brim. The spindle speed was set to 20 rpm and spindle no. 7 was used for all experiments. The experiment was run at room temperature (28 1 C). Viscosity was measured after 5 min standing period.
2.4. Ingredients
2.10. Measurement of physical and sensory characteristics of cake
Sugar powder procured from the local market, shortening (Margarine, Hindustan Lever Ltd., Mumbai, India), baking powder, single and slow acting type, acid source sodium aluminium sulphate (Hindustan Lever Ltd.), salt, calcium propionate, glacial acetic acid (S.D. Fine Chem Ltd., Mumbai, India) and pineapple essence (Bush Boake Allen Ltd., Chennai, India) were used in these studies.
2.10.1. Cake volume Cake volume was measured by the Rapeseed displacement method (Chopin, S.A., France).
2.3. Emulsifiers
2.5. Preparation of emulsifier gel Gels were prepared using emulsifier and water in the ratio of 1:4. First dispersions were made and then dispersions under continuous agitation were heated to a temperature of 65 C for GMS and 45 C for SSL. On cooling gels were obtained. For all the experiments the gels were added in order that there was 0.5% emulsifier on wheat flour basis. 2.6. Cake formulation The following formulation for the preparation of cake was used wheat flour (100 g); shortening (60 g); sesame oil (15/30/45/60 g); crystal sugar (100 g); salt (0.5 g); baking powder (2 g); pineapple essence (0.5 ml); calcium propionate (0.3 g); glacial acetic acid (0.1 ml); water (12 ml); hydrocolloids: xanthan/HPMC (0.5 g) and emulsifier GMS/SSL (0.5 g). Wheat flour, salt, baking powder, hydrocolloids and calcium propionate were sifted thrice; sugar powder, margarine and essence were creamed for 1 min at 58 rpm, 1 min at 112 rpm and 5 min at 173 rpm. Simultaneously egg is whipped with crystal sugar and essence (both pineapple and vanilla) at 173 rpm for 7 min. Emulsifiers were added along with egg. Then whipped egg was added to the flour-fat mixture in 2–3 additions at 58 rpm. After 2 min of mixing of egg, flour-fat mixture, acetic acid and water were added and mixed at 112 rpm for 2 min. The batter temperature was 28 C. Cake batter (330 g) was
2.10.2. Cake texture Texture profile analysis of cake was performed at room temperature by using an LR-5K Texture Analyzer (Lloyd Instruments Ltd., Hampshire, England) with 5-kg load cell. The samples (4.0 4.0 2.5 cm) were compressed by using an aluminium 80 mm diameter circular disc probe. The texture parameters were determined with a cross head speed of 50 mm/min, compression distance 50% of cake’s height and 5-s delay between two bites. The data were analyzed by using Nexygen Version 4.0 Software (LR-5K) to measure cake hardness, gumminess and chewiness, as described by Bourne (1978). 2.10.3. Scanning electron microscopic (SEM) studies SEM studies were carried out using Leo scanning electron microscope Model 435 VP (Leo Electronic Systems, Cambridge, UK). Cake samples (size 20 20 mm) were defatted with hexane, followed by freeze-drying using Heto freeze-dryer Model DW3 (Allerød, Denmark). Cake samples were separately placed on the sample holder using double sided scotch tape and was exposed to gold sputtering (2 min, 2 mbar). Finally, each sample was transferred to the microscope where it was observed at 15 kV and 9.75 105 torr vacuum. 2.10.4. Sensory evaluation of cake Sensory evaluation of cakes was carried out by a panel of trained judges by assigning scores for various quality parameters namely, crust color, crust shape, crumb color, crumb grain, texture, mouthfeel for the maximum score of 10 for each parameter. The overall quality score was taken as the combined score of six quality attributes.
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2.10.5. Fatty acid composition 2.10.5.1. Fat extraction. Samples used for the studies were fat (margarine), sesame oil, cake batters (with fat, 50% sesame oil) and cakes (with fat, 50% sesame oil). The batter and the cake samples were partially dried in a vacuum oven (70 C for 3 h) and the fat was extracted in a Soxhlet apparatus using petroleum ether. Margarine was heated in an oven to get two layers of water and oil. The oil was decanted and the residual moisture in oil was removed using anhydrous sodium sulphate. The fatty acid composition of these oil samples was determined by analyzing the fatty acid methyl esters by gas–liquid chromatography. 2.10.5.2. Preparation of fatty acid methyl esters. The methyl esters were prepared by using 14% BF3/methanol (Morrison & Smith, 1964). About 50–80 mg of oil was transferred into a test tube, treated with benzene, methanol and BF3/methanol. The samples were heated, boiled for 10 min and cooled. The methyl esters were extracted using petroleum ether and the aqueous phase was discarded. The ether extract was washed with water and dried using anhydrous sodium sulphate. The solvent was evaporated, dissolved in 1 ml chloroform and taken for further work. 2.10.5.3. Thin-layer chromatography (TLC). The methyl esters were checked for complete esterification by TLC. TLC plates were coated using silica gel (silica gel for thin-layer chromatography, Ranbaxy), activated for 1 h at 105 C. The esterified samples were spotted on the plates and kept in a TLC chamber containing the solvent saturated for 1 h. The solvent system used was 80:20:1 petroleum ether:diethyl ether:glacial acetic acid. Esters gave a dark spot near the solvent front when kept in an iodine chamber. 2.10.5.4. Gas chromatography (GC). Pure fatty acid methyl esters were analyzed using a Shimadzu GC-15A (Shimadzu, Kyoto, Japan) equipped with a flame ionization detector attached to CR-4A data processor, operating under the following conditions: column: 2.4 m 0.3 cm stainless steel packed with 15% diethylene glycol succinate (DEGS) coated on chromosorb W (60-80 mesh); column temperature 180 C; injector temperature 220 C; detector temperature: 240 C; carrier gas, nitrogen at a flow rate of 40 ml/ min. The peaks were identified by comparing the retention time with standard 18:0 and reported as relative percentage of individual fatty acids. 2.11. Statistical analysis Data were statistically analyzed using ANOVA with different experimental groups appropriate to the completely randomized design with four replicates each. The experimental groups were then separated statistically using Duncan’s new multiple range tests, as described by Steel and Torrie (1960). 3. Results and discussion 3.1. Quality of wheat flour The wheat flour had 0.53% total ash, 9.5% dry gluten, 444 s falling number and 20 ml of Zeleny’s sedimentation value. 3.2. Cake making characteristics 3.2.1. Effect of replacement of fat with different levels of sesame oil on the physical characteristics of cake 3.2.1.1. Batter microscopy. Fig. 1A is the photomicrograph of control cake batter made with fat in which some solid in the form of flour
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and starch can be seen. Small and medium sized air bubbles distributed throughout the batter can be observed. In Fig. 1B which is the photomicrograph of cake batter with 25% sesame oil, predominantly large air bubbles could be seen. Medium and small sized air bubbles could be observed in the photomicrograph of batter with 50% sesame oil (Fig. 1C). In the photomicrograph of batter with 75% sesame oil (Fig. 1D) more number of small air bubbles along with medium sized air cells can be seen. Few large and small air bubbles (Fig. 1E) can be seen in photomicrograph of cake batter containing 100% sesame oil and the number of air cells seems to be less. The shortening used in the cakes plays a predominant role in determining the structure (Hartnett & Thalheimer, 1979). It has been demonstrated that dispersion of plastic fat into globules throughout the batter and the ability of the fat to incorporate air were directly related to volume and grain in the finished products. Hence, liquid oils without the ability to incorporate air produced low volume and poor grain. 3.2.1.2. Batter viscosity and specific gravity. Batters of control cake with fat and cakes containing 25, 50, 75 and 100% sesame oil were analyzed for physical characteristics like viscosity and specific gravity. The results are given in Table 1. The viscosity of control batter containing 100% fat after a standing period of 5 min was 28,800 cP. It decreased to 16,000, 14,400, 12,800 and 11,200 cP when 100% fat was replaced with 25, 50, 75 and 100% sesame oil respectively. The specific gravity of control batter was 0.78 g/cc which on addition of increasing amounts of sesame oil from 25 to 100% increased it from 0.89 to 1.04 g/cc. The above results indicate that when compared to fat, sesame oil decreases the cake batter viscosity and increases specific gravity due to less air incorporation. Air incorporation depends both on the aeration process (beater speed and design) and on the physico-chemical properties of the batter (viscosity and surface tension), which are determined by formulation (Sahi & Alava, 2003). 3.2.1.3. Cake volume and moisture. Effect of replacement of fat with different levels of sesame oil on cake volume and moisture is presented in Table 1. Control cake with 100% fat showed the highest volume (805 cm3/330 g) and replacement of fat with increasing addition of sesame oil from 25 to 100% decreased the volume from 770 to 645 cm3/330 g. As sesame oil content increased from 25 to 100%, the moisture content decreased from 21.1 to 20.3%; this is due to decrease in retention of water in the cakes containing sesame oil. The above results indicate that the nature of the batter with sesame oil having lower viscosity and higher specific gravity resulted in low volume. Shelke, Faubion, and Hoseney (1990) also suggested that lower viscosity of the batter during heating is one of reason for decreased end product volume. It is possible that, in the presence of a less viscous batter, carbon dioxide evolved and water vapor produced might not be trapped in the air cells during baking, thus resulting in the cakes with low volume. 3.2.1.4. Cake texture. Fig. 2 represents influence of sesame oil on the texture of cakes. Hardness value for control cake with fat was 16.4 N. Replacement of fat with increasing amount of sesame oil from 25 to 100% significantly increased the hardness values from 20.2 to 28.7 N. The gumminess value for control cake was 6.8 N, 25% sesame oil (8.5 N), 50% sesame oil (9.0 N), 75% sesame oil (10.5 N) and 100% sesame oil (11.7 N). The chewiness value of cake with 25% sesame oil was 90.7 N mm, 50% sesame oil (95.1 N mm), 75% sesame oil (108.8 N mm) and 100% sesame oil (126.4 N mm) as against control (65.5 N mm). The above results indicate that replacement of fat with sesame oil at all levels tried adversely affected the texture of cake.
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Fig. 1. Photomicrographs of cake batter (magnification 10). A – control; B – 25% SO; C – 50% SO; D – 75% SO; E –100% SO; F – 50% SO þ xanthan; G – 50% SO þ HPMC; H – 50% SO þ GMS; I – 50% SO þ SSL; J – 50% SO þ HPMC þ SSL. SO – sesame oil; GMS – glycerol monostearate; SSL – sodium steoryl-2-lactylate; HPMC – hydroxypropylmethylcellulose.
3.2.1.5. Sensory characteristics of cake. Increase in sesame oil percentage from 25 to 100% resulted in decrease in sensory scores (Table 1) for crust color and shape i.e. the crust color became dark and the crust shape showed tendency to become flat. Yellowness Table 1 Effect of replacement of fat with different levels of sesame oil on quality characteristicsb of cake. Parameters
Controla
25
50
75
100
Batter viscosityc (cP) Batter-specific gravity (g/cc) Volume (cm3/330 g of batter) Moisture (%) Crust color (10) Crust shape (10) Crumb color (10) Crumb grain (10) Texture (10) Mouthfeel (10) Overall quality score (60)
28,800e 0.78a
16,000d 0.89b
14,400c 0.91c
12,800b 1.01d
11,200a 1.04e
5.5 0.01
805e
770d
730c
665b
645a
10
21.6c 9c 9d 9d 9c 9e 9e 54e
21.1b 8.5b 8c 8c 8b 8d 8d 48.5d
20.9b 8b 7b 6b 8b 7c 7c 43c
20.6a 7a 7b 6b 6a 6b 6.5b 38.5b
20.3a 6.5a 6a 5a 6a 5a 5a 33.5a
0.2 0.03 0.02 0.02 0.04 0.02 0.03 0.50
a b c d
SEMd ()
Sesame oil (%)
Control cake contains 60 g of fat/100 g flour. Means in the same row followed by different letter differ significantly (p 0.05). Viscosity measured after a standing period of 5 min using Brookfield viscometer. Standard error of the mean at 15 degrees of freedom.
increased with increase in the sesame oil content. The sensory score for crumb grain decreased as the grain showed thick cell walled, compact cells. Control cakes showed soft texture while cakes with sesame oil were firm and the firmness increased with increase in sesame oil from 25 to 100%. This is reflected in the increase in the hardness values (Fig. 2) of cakes with different levels of sesame oil measured using Instron. The mouthfeel indicated that the cakes with sesame oil were chewy and also showed lump formation at 75 and 100% sesame oil level. When compared to other cake samples, cakes with 100% sesame oil showed unacceptable, dominating oily smell. The overall quality score of control cake with fat was 54 and cake with 100% sesame oil was 33.5 for the maximum score of 60. 3.2.1.6. Microstructure of cake. Fig. 3A–E represents the micrographs of cake crumb with different percentages of sesame oil. Fig. 3A is the micrograph of control cake crumb prepared with fat entirely. It shows a continuous gluten matrix with one or two partial outlines of starch granules embedded in the matrix. The starch granules have lost their shape owing to gelatinization. The protein components of wheat flour have been described as network covering the starch granules in earlier studies by Aranyi and Hawrylewicz (1969). Hoseney (1985) also observed in mixed wheat flour dough and reported that it is a random mixture of protein fibrils with adhering starch granules. Fig. 3B which is the micrograph of cake crumb with 25% sesame oil, a rather
M. Sowmya et al. / Food Hydrocolloids 23 (2009) 1827–1836
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Fig. 2. Effect of different levels of sesame oil and additives on texture profile analysis of cakes. SO – sesame oil; GMS – glycerol monostearate; SSL – sodium steoryl-2-lactylate; HPMC – hydroxypropylmethylcellulose.
ruptured, discontinuous, gluten protein matrix can be seen. Hsu, Gordon, and Davis (1980) stated that in cakes prepared with oil, the matrix appears as lakes that assume irregular shape around starch granules. They also opined that the matrix components most likely are proteins, lipids and solubilized starch. At 50% sesame oil level, the cake crumb micrograph showed slightly more continuous gluten matrix (Fig. 3C) than the micrograph of cake crumb with 25% sesame oil. No starch granules could be observed in the micrographs of cake crumb made with 75% sesame oil (Fig. 3D) or 100% sesame oil (Fig. 3E); the gluten protein matrix appeared discontinuous and most of the starch granules were gelatinized. 3.2.2. Effect of replacement of fat with 50% sesame oil and hydrocolloids on physical characteristics of cakes 3.2.2.1. Batter microscopy. Rusch (1981) stated that various film forming properties in batter form the wall of the foam cell. Integrity of these walls determines the cake volume and uniformity of appearance. Only few number of medium and small air cells can be seen in the photomicrograph of cake batter with 50% sesame oil and xanthan (Fig. 1F). Fig. 1G representing the photomicrograph of cake batter with 50% sesame oil and HPMC shows large, medium and small sized air cells. 3.2.2.2. Batter viscosity and specific gravity. Effect of replacement of fat with 50% sesame oil and hydrocolloids such as xanthan and HPMC separately at the level of 0.5% is presented in Table 2. The specific gravity of control batter was 0.78 g/cc, 50% sesame oil (0.91 g/cc), xanthan (1.06 g/cc) and HPMC (0.88 g/cc). This shows that cake batter with xanthan was heavier than all other samples. Addition of HPMC decreased the specific gravity from 0.91 to 0.88 g/cc indicating improvement in the batter characteristics of cake with 50% sesame oil. Addition of hydrocolloids like xanthan and HPMC to the cake with 50% sesame oil increased the batter viscosity from 14,400 to 25,600 and 20,200 cP respectively. Generally, addition of hydrocolloids increases the viscosity of cake batter due to their water binding capacity. Batter containing xanthan showed the highest viscosity
which was attributed to the high water holding capacity of xanthan and also due to xanthan’s unique, rod-like conformation, which is more responsive to shear than a random-coil conformation (Urlacher & Noble, 1997). Xanthan has a cellulosic backbone which is rendered water soluble by the presence of trisaccharide branches attached to every second glucose unit in the main chain (Sanderson, 1981). It is completely soluble in hot or cold water, turning into a very viscous solution even if the concentration is small. According to Gomez, Ronda, Caballero, Blanco, and Rosell (2006), the influence of hydrocolloids on the final cake volume is due to increase in batter viscosity that slows down the rate of gas diffusion and allows its retention during the early stages of baking. 3.2.2.3. Cake volume and moisture. Among the two hydrocolloids tried, HPMC showed significant improvement in the volume of cake with 50% sesame oil from 730 to 850 cm3/330 g of batter while addition of xanthan decreased it (Table 2). According to Bell (1990) HPMC forms interfacial films at the boundaries of the gas cells that confer some stability to the cells against the gas expansion and processing condition changes. The moisture content of cakes also increased with addition of hydrocolloids. The increase in the moisture content in cake with HPMC and xanthan explains the ability of hydrocolloids to hydrate at room temperature; and its self-interactions without competing with gluten proteins and starchy polysaccharides for the water available in the system (Leon et al., 2000). 3.2.2.4. Cake texture. Fig. 2 represents influence of sesame oil and hydrocolloids on the texture of cakes. Hardness, gumminess and chewiness values for control cake with fat were 16.4 N, 6.8 N mm and 65.5 N mm. Replacement of fat with 50% sesame oil and xanthan significantly increased these parameters to 31.3 N, 13.8 N mm, 140.1 N mm while HPMC reduced these to 15.1 N, 5.8 N mm and 58.5 N mm respectively. The above results indicate that addition of HPMC is beneficial in improving the texture of cake with 50% sesame oil. According to Rosell, Rojas, and de Barber (2001), xanthan gum can provoke a crumb firmness increase probably due to the thickening of the crumb cells
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Fig. 3. Microstructure of cake crumb (magnification 1000). A – control; B – 25% SO; C – 50% SO; D – 75% SO; E – 100% SO; F – 50% SO þ xanthan; G – 50% SO þ HPMC; H – 50% SO þ GMS; I – 50% SO þ SSL; J – 50% SO þ HPMC þ SSL. PM – protein matrix; SG – starch granule; WSG – wrapped starch granule.
surrounding the air spaces. Firmness increase may also be a result of molecular entanglements between xanthan and gluten proteins, possibly enhanced by ionic interactions due to carboxylate groups on the polysaccharide. Furthermore, xanthan addition can also amplify wheat starch granules swelling during heating but it can also increase their rigidity (Mandala & Bayas, 2004), which can influence negatively the final bread firmness when its concentration increases. 3.2.2.5. Sensory characteristics of cake. Effect of replacement of fat with 50% sesame oil and hydrocolloids on sensory characteristics of cake is presented in Table 2. The results showed that the cakes with xanthan had yellowish crumb color, closed crumb grain, firmer texture and exhibited higher degree of chewiness than the cakes with 50% sesame oil. This is indicated by the decrease in the sensory scores for crumb color, crumb grain, texture and mouthfeel. On the contrary, addition of HPMC significantly increased the sensory scores of these characteristics of cake with 50% sesame oil. It is interesting to note that the above quality characteristics not only improved but also were better than the control cake with 100% fat. This is indicated by the overall quality score of 55 when compared to 54 of control cake.
3.2.2.6. Microstructure of cake. In Fig. 3F which is the micrograph of cake crumb with 50% sesame oil and xanthan, partial outlines of a few of starch granules can be seen. Chaisawang and Suphantharika (2006) stated that in SEM micrographs of tapioca, xanthan totally wrapped the native starch granules. In our SEM study, the wheat starch granules seemed to be wrapped by xanthan as the granules are not visible and only a veil-like gluten matrix can be seen. A few partial outlines of starch granules entrapped in protein matrix can be observed in Fig. 3G which is the micrograph of cake crumb with 50% sesame oil and HPMC. Barcenas and Rosell (2005) opined that microstructure of bread crumb containing HPMC showed a smooth structure with less number of cavities. They also stated that HPMC enfolds all the other bread constituents. A similar effect could be observed in the microstructure of cake crumb with HPMC. 3.2.3. Effect of emulsifiers on the physical characteristics of cake with 50% sesame oil 3.2.3.1. Batter microscopy. In the photomicrograph of cake batter with 50% sesame oil and GMS (Fig. 1H), a few large, medium and fine air cells can be seen. Fig. 1I is the photomicrograph of cake batter with 50% sesame oil and SSL in which large and many number of
M. Sowmya et al. / Food Hydrocolloids 23 (2009) 1827–1836 Table 2 Effect of hydrocolloids on quality characteristicsc of cake with 50% sesame oil. Parameters
Batter viscosityd (cP) Batter-specific gravity (g/cc) Volume (cm3/330 g of batter) Moisture (%) Crust color (10) Crust shape (10) Crumb color (10) Crumb grain (10) Texture (10) Mouthfeel (10) Overall quality (60) a b c d e
Controla
50% Sesame oil
SEMe ()
50% Sesame oil
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Table 3 Effect of emulsifiers on quality characteristicsb of cake with 50% oil. Parameters
Controla
Hydrocolloids (0.5%)
50% Sesame oil
b
Xanthan
HPMC
28,800d 0.78a
14,400a 0.91c
25,600c 1.06d
20,200b 0.88b
60 0.01
805c
730ab
710a
850d
10
21.6b 9b 9b 9c 9c 9b 9c 54c
20.9a 8a 7a 6b 8b 7a 7b 43b
23.5d 8a 7a 5a 6.5a 7.5a 6a 40a
22.8c 9b 9b 9c 9c 9.5c 9.5d 55d
0.20 0.03 0.04 0.02 0.03 0.04 0.02 0.45
Control cake contains 60 g of fat/100 g flour. HPMC – hydroxypropylmethylcellulose. Means in the same row followed by different letter differ significantly (p 0.05). Viscosity measured after a standing period of 5 min using Brookfield viscometer. Standard error of the mean at 12 degrees of freedom.
small air cells evenly distributed are seen. According to Ellinger (1962) hydrophilic emulsifiers promote the uniform dispersion of minute fat particles and their entrapped air cells in a cake batter, thereby creating a large number of sites where the water vapor can expand during the baking stage. Expansion of water vapor occurs only within the fat-entrapped air cells. Excessively large and buoyant air bubbles tend to rise out of the batter, this results in a coarse-grained cake of low volume. Contrariwise, the smaller the individual air cells are, the larger will be the cake volume and the finer its grain. However, Jyotsna, Prabhasankar, Indrani, and Venkateswara Rao (2004) reported that in the photomicrograph of cake batter with fat and SSL gel, the number of air cells was decreased and most of the entrapped air cells were of smaller size with non-uniform distribution. According to Wootton, Howard, Martin, McOsker, and Holme (1967), the emulsifiers provide protection to protein-film cell walls. The emulsifiers also coat the exterior of fat particles so that the surface of the particle is no longer disruptive to the protein film. 3.2.3.2. Batter viscosity and specific gravity. Effect of replacement of fat with 50% sesame oil and emulsifiers on the physical characteristics of cake is presented in Table 3. The results showed that addition of GMS and SSL increased the batter viscosity of cake with 50% sesame oil from 14,400 cP to 16,200 and 18,200 cP respectively. The batter-specific gravity decreased with addition of emulsifiers. According to Pyler (1988) emulsifiers aid the incorporation and sub division of air into the liquid phase to promote foam formation and also promote uniform dispersion of fat which contains entrapped air cells and thereby giving more sites for the expansion of gas resulting in greater volume and soft texture. 3.2.3.3. Cake volume and moisture. The volume increased significantly with emulsifiers (Table 3) however among two emulsifiers tried, SSL showed the highest improvement in volume of 860 ml followed by GMS (840 ml) and control cake with fat (805 ml). Addition of GMS and SSL increased the moisture content of cake with 50% sesame oil.
Batter viscosityc (cP) Batter-specific gravity (g/cc) Volume (cm3/330 g of batter) Moisture (%) Crust color (10) Crust shape (10) Crumb color (10) Crumb grain (10) Texture (10) Mouthfeel (10) Overall quality (60) a b c d e
SEMd ()
Emulsifiers (0.5%) GMSe
SSLe
28,800b 0.78a
14,400a 0.91c
16,200c 0.84b
18,200d 0.83b
45 0.001
805b
730a
840c
860d
10
21.6b 9b 9c 9c 9c 9b 9c 54d
20.9a 8a 7a 6a 8a 7a 7a 43a
22.0a 9b 8.5b 8.5b 8.5b 9b 8.5b 52b
22.5c 8.5a 8b 8.5b 9.5d 9.5c 9.5c 53.5c
0.25 0.03 0.04 0.02 0.03 0.02 0.03 0.45
Control cake contains 60 g of fat/100 g flour. Means in the same row followed by different letter differ significantly (p 0.05). Viscosity measured after a standing period of 5 min using Brookfield viscometer. Standard error of the mean at 12 degrees of freedom. GMS – glycerol monostearate; SSL – sodium stearoyl-2-lactylate.
cake with 50% sesame oil and GMS was 16.0 N, SSL (15.5 N) as against control 16.4 N. Gumminess and chewiness of cake with 50% sesame oil and GMS were 6.5 N mm, 62.5 N mm, SSL (6.0 N mm and 60.2 N mm) as against control (6.8 N mm and 65.5 N mm) and cake with 50% sesame oil (9.0 N mm and 95.1 N mm). Addition of GMS and SSL significantly improved the texture of cake with 50% sesame oil but the improvement brought about by SSL was higher than GMS. 3.2.3.5. Effect of emulsifiers on sensory characteristics of cake with 50% oil. Sensory evaluation of cake showed that addition of emulsifiers to cakes with 50% sesame oil significantly increased the overall quality score of cake. The overall quality score for control cake was 54, cake with 50% sesame oil, 43 and it increased to 52.0 with GMS and 53.5 with SSL as shown in Table 3. The above results indicate that addition of emulsifiers increased the overall quality score of cake with 50% sesame oil. However the improvement in the overall score of cake with 50% sesame oil brought about by SSL was highest. The above results indicate that among the two emulsifiers tried, SSL significantly improved the quality of cake with 50% sesame oil. The volume and texture of cake with SSL were better than the control cake. Table 4 Effect of replacement of fat with 50% sesame oil, HPMC and SSL on quality characteristicsb of cake. Parameters
Controla
50% Sesame oil
50% Sesame oil þ HPMCe þ SSLe
SEMd ()
Batter viscosityc (cP) Batter-specific gravity (g/cc) Volume (cm3/330 g of batter) Moisture (%) Crust color (10) Crust shape (10) Crumb color (10) Crumb grain (10) Texture (10) Mouthfeel (10) Overall quality (60)
28,800c 0.78a
14,400a 0.91c
20,800b 0.80b
50 0.001
805b
730a
880c
15
21.6b 9b 9b 9b 9b 9b 9b 54b
20.9a 8a 7a 6a 8a 7a 7a 43a
23.5c 9.5c 9.5c 9b 9.5c 9.5c 9.5c 56c
0.25 0.04 0.03 0.02 0.02 0.03 0.02 0.30
a
3.2.3.4. Effect of emulsifiers on the texture profile analysis of cake with 50% sesame oil. Fig. 2 shows that addition of GMS and SSL lowered the hardness, gumminess and chewiness values of control cake with fat and cake with 50% sesame oil. The hardness value of
50% of Sesame oil
Control cake contains 60 g of fat/100 g flour. Means in the same row followed by different letter differ significantly (p 0.05). c Viscosity measured after a standing period of 5 min using Brookfield viscometer. d Standard error of the mean at 9 degrees of freedom. e HPMC – hydroxypropylmethylcellulose; SSL – sodium stearoyl-2-lactylate at (0.5%). b
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Fig. 4. Photograph of cakes. A – control; B – 50% sesame oil; C – 50% sesame oil þ HPMC þ SSL.
3.2.3.6. Microstructure of cake. Fig. 3H represents micrograph of cake crumb with 50% sesame oil treated with GMS. The micrograph shows partial outlines of a couple of starch granules enmeshed in protein matrix. A few starch granules trapped in protein matrix can be seen in micrograph (Fig. 3I) of cake crumb with 50% sesame oil and SSL. Evans, Volpe, and Zabik (1977) stated that in the ultra structure of bread dough with SSL, the gluten sheet in the dough was extremely thin, intact and translucent in many areas. Starch granules silhouettes were visible beneath the veiling proteins. The proteins draped finely over the mass of granules. A similar effect can be seen in our SEM studies. 3.2.4. Effect of replacement of fat with 50% sesame oil, HPMC and SSL on physical characteristics of cake 3.2.4.1. Batter microscopy. Fig. 1J represents the cake batter with 50% sesame oil, HPMC and SSL. The photomicrograph shows medium and small uniform cells distributed throughout the batter when compared to the medium and small sized bubbles unevenly distributed in the cake batter of 50% sesame oil (Fig. 1C). 3.2.4.2. Batter viscosity and specific gravity. Cake batter with 50% sesame oil and HPMC and SSL showed higher viscosity of 20,800 cP and specific gravity (0.80) lower than the cake with 50% sesame oil (0.91) as shown in Table 4. 3.2.4.3. Cake volume and moisture. Table 4 shows the effect of combination of HPMC and SSL on moisture and volume of cake with 50% sesame oil. It showed highest moisture (23.5%) and volume (880 ml) and lower specific gravity (0.80 g/cc) than the cake with 50% sesame oil. The volume of cake with 50% sesame oil, HPMC and SSL was better than control as seen in Fig. 4.
3.2.4.4. Effect of HPMC and SSL on the texture profile analysis of cake with 50% sesame oil. Fig. 2 shows the texture profile analysis of cake with 50% sesame oil and HPMC and SSL. Cake with 50% sesame oil and HPMC and SSL had the least hardness value of 14.1 N, gumminess value of 5.4 N and chewiness value of 57.3 N mm, indicating improved texture profile than control. 3.2.4.5. Effect of combination of hydrocolloids and emulsifiers on sensory characteristics of cake with 50% sesame oil. Sensory evaluation of cake with 50% sesame oil and combination of HPMC and SSL as given in Table 4 showed that use of HPMC and SSL improved the crust color and shape, crumb grain, texture and mouthfeel of the cake with 50% sesame oil. This is reflected in the significant increase in the overall quality score from 43 to 56. The improvement was so significant that the quality characteristics of cake with 50% sesame oil and HPMC and SSL were better than control cake with fat. 3.2.4.6. Microstructure of cake. Fig. 3J which represents the micrograph of cake crumb with 50% sesame oil, HPMC and SSL, a continuous gluten matrix with no ruptures can be observed. 3.3. Fatty acid composition Fatty acids play an important role in human diet. The fatty acid composition in Table 5 shows that the major fatty acid in fat (commercial margarine) is palmitic (44.2%) followed by oleic acid (33.5%). The trans fatty acid (TFA) content of margarine has been reported earlier. The TFA content of margarine used for cake preparation was 18.5% (Yella Reddy & Jeyarani, 2001). It also contains lauric, myristic, stearic and linoleic acid. The high palmitic acid content indicated that palm oil or palm stearin is the major
Table 5 Fatty acid composition (%) of fat, sesame oil, batter and cake samples. Samples
12:0
14:0
16:0
16:1
18:0
18:1
18:2
P
Fat Sesame oil Batter with fat Batter with sesame oil Cake with fat Cake with sesame oil
9.1 2.3 0 5.1 0.5 0.1 5.5 0.8 0.2 0.1
5.1 0.8 0 3.6 0.2 0.1 3.9 0.7 0.3
44.2 0.42 10.8 0.8 39.1 0.7 12.1 0.7 41.4 1.6 17.4 0.8
0 0 0.6 0.1 0.4 0.1 0.6 0.4 1.3 0.4
3.9 0.6 5.7 0.1 4.9 0.1 6.2 0.2 4.4 0.5 5.4 0.3
33.5 2.8 43.0 0.5 41.1 0.7 43.0 0.3 38.8 2.2 42.7 0.7
3.5 0.8 40.1 0.8 5.5 0.1 37.6 0.5 5.5 0.6 32.6 0.5
63.0 16.5 52.6 18.5 55.2 23.3
SFA
P
USFA
37.0 83.1 47.4 81.0 44.9 76.6
SFA – saturated fatty acid; USFA – unsaturated fatty acid; 12:0 – lauric acid; 14:0 – myristic acid; 16:0 – palmitic acid; 16:1 – palmitoleic acid; 18:0 – stearic acid; 18:1 – oleic acid.
M. Sowmya et al. / Food Hydrocolloids 23 (2009) 1827–1836
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Fig. 5. Gas chromatogram of fatty acid methyl esters of oil extracted from cakes prepared using (A) fat (margarine) and (B) after replacing fat with sesame oil. 12:0 – lauric acid; 14:0 – myristic acid; 16:0 – palmitic acid; 16:1 – palmitoleic acid; 18:0 – stearic acid; 18:1 – oleic acid; 18:2 – linoleic acid.
ingredient used for the hydrogenated fat. The content of palmitic and myristic acids which elevate blood cholesterol (Zock, De Vries, & Katan, 1994) was significantly high (49.3%). The total saturated fatty acid (SFA) content was 63%. Sesame oil contained only 16.5% SFA and also contained 43% mono unsaturated fatty acid (MUFA) and 40.4% polyunsaturated fatty acid (PUFA). When compared with the cakes prepared using the fat and after replacing with sesame oil, the cakes prepared using the fat contained 55.2% SFA while the cake prepared using sesame oil contained only 23.3% SFA as shown in Table 5. Fig. 5 shows the GC profile of these samples indicating the reduction in palmitic acid and increase in linoleic acid content. On replacing the fat using sesame oil, the palmitic acid which is reported to increase the blood cholesterol decreased from 41.4 to 17.4% and the essential fatty acid (EFA) content increased from 5.5% to 32.6%. Thus the product contains nutritionally superior fatty acids as there was 2.4 times decrease in palmitic acid content and 5.9 times increase in EFA content. 4. Conclusions Total replacement of fat with different levels of sesame oil showed that increase in sesame oil content decreased batter viscosity, cake volume and overall quality score. HPMC and SSL improved the overall quality score of the cake with 50% sesame oil. Combination of HPMC and SSL in cake with 50% sesame oil showed results better than the control cake. On replacing the fat with 50% sesame oil, there was a decrease in saturated fatty acid content and
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