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Physico-chemical and functional properties of flours from Indian kidney bean (Phaseolus vulgaris L.) cultivars
LWT - Food Science and Technology 53 (2013) 278e284
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Physico-chemical and functional properties of flours from Indian kidney bean (Phaseolus vulgaris L.) cultivars Idrees Ahmed Wani a, b, Dalbir Singh Sogi a, *, Ali Abas Wani c, Balmeet Singh Gill a a
Department of Food Science and Technology, Guru Nanak Dev University, Amritsar 143 005, India Department of Food Science and Technology, University of Kashmir, Hazratbal, Srinagar 190 006, India c Department of Food Technology, Islamic University of Science and Technology, Awantipora, Kashmir 190 221, India b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 10 May 2012 Received in revised form 25 January 2013 Accepted 5 February 2013
Flours of four kidney bean (Phaseolus vulgaris L.) cultivars (French Yellow, Contendor, Master Bean and Local Red) were studied. The moisture, ash, protein, fat and crude fibre contents of kidney bean flours varied from 99e104, 30e35, 223e267, 16e20 and 14e21 g/kg, respectively. Synaeresis of flour gels increased from 141 g/kg after 24 h to 194 g/kg after 120 h of storage at 4 C. Scanning electron microscopy of flours revealed starch granules of varied shapes associated with protein and non-protein components. Peak, breakdown and setback viscosity varied significantly (p 0.05) from 591.0e1030.3 cP, 21.3e93.3 cP and 383.7e750.0 cP, respectively. Kidney bean flours displayed two endothermic transitions corresponding to starch gelatinization (60.9e75.2 C) and disruption of the amyloseelipid complex (103.6e129.6 C). Hardness and adhesiveness of flour gels varied significantly from 14.9e19.5 g and 31.5 e81.3 g, respectively. Foaming capacity and foaming stability at different pH showed significant differences. Emulsion activity index at different pH varied from 6.03 to 25.21 m2/g while emulsion stability index was in the range of 15.51e76.21 min. Protein solubility of 8.1e97.8% was observed in the pH range of 2e10. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Kidney bean Flour Pasting properties Emulsifying Foaming Gel texture
1. Introduction Common dry bean (Phaseolus vulgaris L.) is one of the most important crops of the world with different physical, biochemical and sensory properties. The global production of the dry beans in 2010 was 22.9 million metric tonnes and five leading producers were India, Brazil, Myanmar, United States and Mexico (FAO, 2012). The different classes of common dry bean include black bean, cranberry bean, great northern bean, kidney bean, navy bean, pinto bean and small red bean. Kidney bean is one of the most important legume crops of northern India. Kidney beans are good source of protein, starch and dietary fibres (Osorio-Diaz et al., 2003). Physico-chemical properties of kidney beans change with postharvest handling and storage conditions resulting in a reduction in their cooking, eating and nutritional quality as well as consumer acceptance (Njintang, Mbofung, & Waldron, 2001). Consumption of kidney beans could be improved by processing them into flour (Dzudie & Hardy, 1996). It can satisfy the nutritional requirements of consumers especially in developing countries because of growing urbanization (Njintang et al., 2001). * Corresponding author. Tel.: D91 183 2258802x3217; fax: þ91 183 2258820. E-mail address: [email protected] (D.S. Sogi). 0023-6438/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.lwt.2013.02.006
Interest in the utilization of flours from different types of legumes is growing (Chau & Cheung, 1998; Siddiq, Ravi, Harte, & Dolan, 2010) which depend on their functional properties (Hung, Papalois, Nithianandan, Jiang, & Versteeg, 1990; Singh, Wani, Kaur, & Sogi, 2008). These include foaming, emulsification, texture, gelation, water/oil absorption capacities and viscosity (Adebowale & Lawal, 2004). The functional properties of legume flours mainly depend on proteins, carbohydrates and other components. Hydration properties, binding, swelling, dispersibility and viscosity are known to directly influence the characteristics of a food system (McWatters, 1983). The application of legume flours as functional ingredients in some foods such as breads, cakes, biscuits, doughnuts, tortillas, pasta, and snacks has been reported by several authors (Anton, Ross, Lukow, Fulcher, & Arntfield, 2008; Han, Janz, & Gerlat, 2010). The objectives of the present study were to assess the physico-chemical and functional properties of kidney bean flours from locally available cultivars. 2. Materials and methods 2.1. Materials The seeds of three kidney bean (Phaseolus vulgaris L) cultivars e French Yellow, Contendor, and Master Bean were procured from
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Sher-e-Kashmir University of Agricultural Sciences and Technology, Shalimar, Srinagar, J&K, India, whereas, Local Red cultivar was procured from the local market of Srinagar, J&K, India. Seeds were cleaned manually from the dirt, foreign material etc. and stored until further use at 20 C. All the reagents used in the study were of analytical grade.
279
Warriewood, Australia). An aqueous dispersion of flour e 14% moisture basis (12.28%, w/w; 28.5 g total weight) was equilibrated at 50 C for 1 min, heated at the rate of 12.2 C/min to 95 C, held for 2.5 min, cooled to 50 C at the rate of 11.8 C/min and again held at 50 C for 2 min. A constant paddle rotational speed (160 rpm) was used throughout the entire analysis, except for rapid stirring at 960 rpm for the first 10 s to disperse the sample.
2.2. Flour preparation Seeds were ground in a laboratory mill (Newport Supermill1500, Newport Scientific Pvt. Ltd, Warriewood, Australia), sieved through 60-mesh screen and stored in airtight containers at refrigerated temperature until used. 2.3. Physico-chemical properties 2.3.1. Composition Moisture (925.10), protein (920.87), fat (920.85), crude fibre (978.10) and ash (923.03) contents were determined according to standard methods of AOAC (1990). 2.3.2. Bulk density Bulk density was measured as a ratio of mass to volume. A graduated cylinder, previously tarred, was gently filled upto 10 ml mark with flour. The sample was then packed by gently tapping the cylinder on the bench top from a height of five cm until there was no further diminution of the sample level and noted the volume. The weight of the filled cylinder was taken and the bulk density was calculated as the weight of sample per unit volume (kg/L). 2.3.3. Swelling & solubility index Swelling power and solubility of the flour were determined using 2% w/v (db) aqueous suspension of flour at 90 C (Leach, Mc Cown, & Schoch, 1959). 2.3.4. Synaeresis Synaeresis was measured as percentage of water released from 2% w/w (db) flour gel stored at 4 C for 1, 2 and 5 days after centrifugation at 3000 g for 10 min (C-24 BL, Remi, Mumbai, India). 2.3.5. Colour The surface colour of flours was measured using Hunter Colour Lab (Hunter Associates Laboratory Inc., Reston, VA, USA). A glass cell containing uniformly sized flour was placed against the light source, covered with a black cover and L (Lightness), a (red-green), and b (yelloweblue) values were recorded. The instrument was calibrated with black and white tile before colour measurement. Total colour difference (DE) was calculated as:
h
DE ¼ ðDLÞ2 þ ðDaÞ2 þ ðDbÞ2
i1=2
2.4. Scanning electron microscopy The flour was placed on an adhesive tape attached to a circular aluminium specimen stub and then coated vertically with golde palladium. The samples were photographed at an accelerator potential of 10 kV using a scanning electron microscope (JSM-6100, JEOL Ltd, Tokyo, Japan). 2.5. Pasting properties The pasting properties of the flours were measured using a Rapid Visco Analyzer (RVA-4, Newport Scientific Pty Ltd,
2.6. Flour gel texture Textural properties of the gels were evaluated with slight modifications to the methods of Singh, Mc-Carthy, and Singh (2006) as described by Wani, Sogi, Wani, Gill, and Shivhare (2010). 2.7. Thermal properties Thermal properties of kidney bean flours were analysed using DSC (200 PC-Phox Phoenix, Netzsch, Burlington, Germany) equipped with a thermal analysis data station. A 10 mg sample was weighed into a 40 ml capacity aluminium pan and 20 ml distilled water was added with the help of Hamilton micro syringe. Pans were hermetically sealed and allowed to stand for 1 h at room temperature before heating in DSC. The DSC was calibrated using indium and an empty aluminium pan was used as reference. Sample pans were heated at a rate of 10 oC/min from 20 to 180 C and thermal parameters viz. onset (To), peak (Tp), conclusion (Tc) temperature and enthalpy (DH) were calculated from the DSC curves. 2.8. Functional properties 2.8.1. Protein solubility Protein solubility was determined in the pH range 2e10 using 0.1% w/v flour aqueous dispersion. The suspensions were adjusted to the desired pH, solubilised by shaking at 210 rpm at 25 C for 60 min in a shaking incubator (LSI-3016R, Daihan Lab Tech Co., Ltd., Namyangju, Kyonggi, Korea) and then centrifuged at 12,000 g for 10 min. The protein content of the supernatant was determined by the Lowry method (Lowry, Rosebrough, Farr, & Randall, 1951) using bovine serum albumin (BSA) as standard. 2.8.2. Water and oil absorption capacity To determine water and oil absorption capacity 1 g (db) of sample was weighed into 25 ml pre-weighed centrifuge tubes and then stirred into 10 mL of double distilled water or refined soyabean oil (Amrit Banaspati Co. Ltd., Rajpura, Punjab, India) for 1 min. The samples were allowed to stand for 30 min and then centrifuged at 2200 g for 30 min. The water or oil released on centrifugation was drained. Water or oil absorption capacity was expressed as kg of water or oil held per kg of flour sample. 2.8.3. Foaming capacity and stability Aqueous dispersions (2% w/v db) of the flour at pH 2, 4, 6, 8 and 10 were homogenized in a high speed homogenizer (Remi Instruments Division, Vasai, India) at 10,000 rpm for 1 min. Foaming capacity was calculated as the percent increase in volume of the flour dispersion. The foam stability was determined by measuring the foam volume with time and computing half-life. 2.8.4. Emulsifying properties Emulsifying activity index (EAI) and emulsifying stability index (ESI) were determined by turbidimetric method described by Pearce and Kinsella (1978).
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2.9. Statistical analysis The data reported are averages of triplicate observations. An analysis of variance with a significance level of 5% was done, and Duncan’s test was applied to determine the differences between means using the commercial statistical package (SPSS Inc, Chicago, IL, USA). 3. Results and discussion 3.1. Physico-chemical properties The composition of kidney bean flours is presented in Table 1. The moisture content of kidney bean flours was in the range of 99e 104 g/kg. Ash and protein contents varied from 30e35 g/kg and 223e267 g/kg respectively. Fat and crude fibre contents varied from 16e20 g/kg and 14e20 g/kg respectively. Significant (p 0.05) differences were observed in ash, protein, fat, and crude fibre contents among the four bean cultivar. Dzudie and Hardy (1996) reported similar results for the composition of kidney bean flour. Bulk density of kidney bean flours (Table 1) ranged from 0.84 to 0.94 kg/L. Ghavidel and Prakash (2006) reported bulk density value of 0.86 kg/L for lentil flour. However, results obtained in present study were higher than those reported by Dzudie and Hardy (1996) and Siddiq et al.. (2010) for bulk density of kidney beans flours, which might be due to difference in particle size and packing behaviour. Swelling index of kidney bean flour varied from 6.6 to 8.2 kg/kg (Table 1). It was the highest for French Yellow and the lowest for Master Bean flour. Adebooye and Singh (2008) reported swelling index of cowpea flour in the range of 8.0e11.0 kg/kg. Swelling index of flour is related to gelatinisation of starch reflecting breaking of intramolecular hydrogen bonds in the crystalline regions and uptake of water by hydrogen bonding; water absorption by nonstarch polysaccharides and proteins. Solubility index of kidney beans flours was in the range of 320e363 g/L. Shimelis, Meaza, and Rakshit (2006) reported similar results for solubility index (335e 378 g/L). Solubility index is related to the presence of soluble molecules like amylose and albumins in the flour. Significant (p 0.05) differences were observed in swelling and solubility indices of kidney bean flour cultivars. Synaeresis increased from 134 to 197 g/kg among the cultivars during 120 h of storage at 4 C (Table 1). Synaeresis might be Table 1 Physico-chemical properties of some kidney bean flour (n ¼ 3). Parameter
Cultivars French Yellow Contendor
Moisture, g/kg Protein, g/kg Fat, g/kg Ash, g/kg Crude fibre g/kg Bulk density, kg/L Swelling index, g/L Solubility index, g/L Synaeresis, g/kg 24 h. 48 h. 120 h. Colour values L a b DE
99 231 20 30 17 0.85 8.2 320
1.2a 8.5a 1.1b 0.1a 0.5b 0.01a 0.18d 0.1a
153 0.1a 157 2.5b 187 2.8bc 81.1 1.8 9.6 85.6
0.24a 0.02d 0.06c 0.21a
102 223 19 35 21 0.84 7.0 333
3.4a 4.4a 0.9ab 0.4b 0.1c 0.01a 0.01b 0.5b
165 0.6c 175 0.2c 197 5.5c 82.0 1.3 9.5 86.3
0.28a 0.06a 0.11c 0.22a
Master Bean 100 267 18 34 14 0.94 6.6 363
151 6.6b 160 3.2b 168.1 0.4a 81.5 1.4 9.3 85.9
Local Red
3.3a 104 4.4a 4.4b 267 4.4b 1.1ab 16 2.5a 1.7b 35 0.4b 0.8a 16 1.5b 0.01c 0.88 0.01b 0.15a 7.4 0.06c 3.0c 322 6.0a 134 2.6a 138 0.4a 180 8.3b
1.05a 81.6 0.27a 0.03c 1.3 0.01b 0.10b 7.9 0.06a 0.87a 85.7 0.22a
Values expressed are mean standard deviation. Means in the rows with different superscript are significantly different at p 0.05.
attributed to the interaction between leached out amylose and amylopectin chains leading to gel shrinkage, degree of polymerisation of amylose, amylopectin chain length, proportion of short chains or shrink back of partially disintegrated granules to their original size during cooling (Hermansson & Svegmark, 1996). Moreover, starches separated from kidney bean cultivars were found to have high amylose content (Wani et al., 2010). Hunter colour values (L, a, b and DE) of kidney bean flours are shown in Table 1. ‘L’ (lightness) values of flours varied insignificantly (p > 0.05) from 81.1 to 82.0 among the cultivars. Colour scale value of ‘a’ varied significantly (p 0.05) from 1.3 to 1.8 among the cultivars. Flours had ‘b’ value of 7.9e9.6, which was the highest in French Yellow and the lowest in Local Red. DE (total colour difference) varied from 85.6 to 86.3 for various kidney bean flours. Similar results for colour values of kidney bean flours were reported by Shimelis et al. (2006). 3.2. Scanning electron microscopy Shape of the Starch granules varied from ovoid to spherical, with heterogeneous sizes ranging from 10.0 to 35.0 mm in length and from 6.7 to 24.0 mm in width (Fig.1). The globular or irregular particles attached to or located between the starch granules were the protein bodies or fragments of protein matrix disrupted during milling. Particles might also have included mineral and fibre components, as reported by other workers (Aguilera, Esteban, Benitez, Mollá, & Martín-Cabrejas, 2009; Sotomayor et al., 1999). 3.3. Pasting properties Pasting properties of kidney bean flours are presented in Table 2. Peak viscosity of kidney bean flours was in the range of 591.0e 1030.3 cP. The highest peak viscosity was observed for the flour of French Yellow and the lowest for Master Bean cultivars. Values were in agreement with the highest and the lowest swelling index displayed by these cultivars (Table 1). Significantly (p 0.05) higher peak viscosity of French Yellow than rest of the cultivars could be attributed to its higher starch content. The yield of isolated starch from French Yellow was 30.2% compared to 27.2e28.7% in other cultivars on dry weight basis (data not reported). Trough or holding viscosity varied from 494.7 to 1009.3 cP, the highest value was observed for French Yellow and the lowest for Master Bean. Trough viscosity is influenced by the rate of amylose exudation, granule swelling and amyloseelipid complex formation (Wani, Singh, Shah, Weisz, Gul, Wani., 2012). Breakdown viscosity which is a measure of the ease with which the swollen starch granules can be disintegrated was in the range of 21.3e93.3 cP. The highest breakdown viscosity was observed in Master Bean and the lowest in French Yellow flours. Significant (p 0.05) differences were observed in trough and breakdown viscosities of kidney bean flours. Final viscosity varied significantly (p 0.05) among the cultivars and was in the range of 952.0e1611.7 cP. French Yellow had the highest final viscosity and Local Red had the lowest. This could be attributed to the highest and the lowest amylose content found in the starch of these cultivars as reported by the authors in their previous study (Wani et al., 2010). All the flours showed a gradual increase in viscosity with increase in temperature. The increase in viscosity with temperature may be attributed to the binding of water to exuded amylose from the granules during swelling and further uptake of water by the granules due to increase porosity or channel from water migration (Ghiasi, Varriano-Marston, & Hoseney, 1982). Setback viscosity, a measure of retrogradation tendency of flours gels on cooling varied significantly (p 0.05) from 338.7e750.0 cP. Retrogradation is the result of hydrogen bonding between starch molecules that have both hydroxyl and hydrogen acceptor sites
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281
Fig. 1. Scanning electron micrographs of kidney bean flours of (a) French Yellow, (b) Contendor, (c) Master Bean, (d) Local Red.
This could be attributed to its lowest amylose content as reported in our previous results (Wani et al., 2010). The extent of amylose gel network and deformability of swollen granules are reported as the main factors contributing to gel strength (Luyten, van Vliet, & Walstra, 1992). Cohesiveness, gumminess, springiness and chewiness did not show any significant (p 0.05) differences among the cultivars. Adhesiveness ranged from 27.7 to 87.7 gs. Master Bean and Local Red cultivars showed significantly (p 0.05) lower adhesiveness than French Yellow and Contendor flours.
(Del Rosario & Pontiveros, 1983). The amylose fraction of starch is believed to be responsible for retrogradation, since amylose molecules are free to orient themselves together than are the amylopectin molecules. Retrogradation rate is affected by amylose and amylopectin concentrations, molecular size, temperature and pH. Pasting temperature, the temperature at the onset of rise in viscosity varied from 80.6 to 84.5 C, the highest value was observed for Local Red and the lowest for Contendor flours. Significantly (p 0.05) higher protein content of Local Red than French Yellow and Contendor flours could induce increased proteinestarch interaction and consequently tends to retard swelling leading to increase in pasting temperature.
3.5. Thermal properties The thermal properties of kidney bean flours are shown in Table 4. Thermo grams of kidney bean flour displayed two endothermic peaks. The first peak at lower temperature was due to starch gelatinization, and the second peak at a higher temperature is due to amyloseelipid complexation. Starch gelatinization parameters varied from 63.0e69.2 C; 67.2e73.3 C; 70.5e77.4 C and 4.9e6.7 J g1, respectively for To, Tp, Tc and DH. The gelatinization transition temperatures are reported to be influenced by amylose
3.4. Flour gel texture The textural properties like hardness, cohesiveness, gumminess, springiness, chewiness and adhesiveness of kidney bean flour gels were determined on a texture analyzer (Table 3). Gel hardness varied from 14.9 to 19.5 g for kidney bean cultivars. Local Red flour showed significantly (p 0.05) lower hardness than other cultivars.
Table 2 Pasting properties of flours from different kidney bean cultivars (n ¼ 3). Cultivars
Peak viscosity (cP)
French Yellow Contendor Master Bean Local Red
1030.3 673.0 591.0 603.7
21.7b 43.6a 37.0a 47.5a
Trough viscosity (cP) 1009.3 604.3 494.7 568.3
20.9c 39.1b 14.2a 53.1ab
Breakdown viscosity (cP) 21.3 68.7 93.3 35.3
2.1a 4.5bc 40.7c 6.7ab
Values expressed are mean standard deviation. Means in the column with different superscript were significantly different at p 0.05.
Final viscosity (cP) 1611.7 1308.0 1244.7 952.0
61.6c 66.8b 25.2b 48.0a
Setback viscosity (cP) 602.7 703.7 750.0 383.7
43.5b 38.7bc 11.5c 6.4a
Pasting temperature ( C) 81.7 80.6 84.0 84.5
0.9a 0.8a 0.8b 1.7b
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Table 3 Texture analysis of kidney bean flour gels after 24 h of storage at 4 C (n ¼ 3). Cultivars
Hardness (g)
French Yellow Contender Master Bean Local Red
17.8 19.5 18.7 14.9
Cohesiveness
2.5b 0.9b 0.6b 0.3a
0.3 0.3 0.3 0.3
Gumminess (g)
0.1a 0.1a 0.0a 0.0a
5.7 5.9 5.7 3.9
Springiness
1.6a 1.3a 0.1a 0.8a
0.9 0.7 1.1 1.1
Chewiness (g)
0.4a 0.1a 0.3a 0.0a
5.6 4.2 6.3 4.4
Adhesiveness (gs)
3.3a 1.6a 1.5a 0.8a
81.3 87.7 27.7 31.5
19.1b 14.3b 8.3a 10.3a
Values expressed are mean standard deviation. Means in the column with different superscript are significantly different at p 0.05.
3.6.2. Water and oil absorption capacity Water absorption capacity (WAC) of kidney bean flour varied insignificantly (p > 0.05) from 2.6 to 2.7 kg/kg of flour (Fig. 2). Water absorption capacity is important for certain product characteristics, such as the moistness of the product, starch retrogradation, and the subsequent product staling. Siddiq et al. (2010) and Aguilera, Estrella, Benitez, Esteban, and Martín-Cabrejas (2011) reported WAC of kidney bean flour from 2.2 to 2.7 kg/kg and
a 100 90 Protein solubility (%)
content, distribution of amylopectin branch chains, lipid complexed amylose chains, and protein content (Jayakody et al., 2007). The second endothermic peak around 104e130 C represented the amyloseelipid complexation. Significantly (p 0.05) higher melting temperature (To and Tp) was observed for Local Red cultivar. However, there was no significant difference in Tc among the cultivars. The melting enthalpy (DH) of second endothermic transition did not show significant differences among the cultivars. The second endothermic peak may be due to high amylose content (364e417 g/kg starch) of the flour samples which interacts with available lipids (16e20 g/kg flour) to delay gelatinization as also reported by (Wani et al., 2010). Previous reports on kidney bean protein denaturation further suggest that the second endothermic peak should be arising from starchelipid complexation (Rui, Boye, Ribereau, Simpson, & Prasher, 2011). It was reported that the peak denaturation temperature was 82.14e91.14 C for kidney bean proteins extracted from nine cultivars. However, similar findings on amyloseelipid complexation have been reported recently by Chung, Liu, Pauls, Fan, and Yada (2008) and Ahmadi-Abhari, Woortman, Hamer, Oudhuis, and Loos (in press). The amylosee lipid complexation influences the pasting, swelling and hydration properties of legume flours.
80 70 60
50 40 30 20 10 0 1
2
3
3.6. Functional properties
b
6
7
8
9
3.0
To ( C)
Tp ( C)
Tc ( C)
DH
69.2a
73.3a
77.4a
63.0a 60.9a
69.1a 67.2a
68.0a
69.3a
DH
To ( C)
Tp ( C)
Tc ( C)
6.8a
103.6a
111.0a
118.5a
5.9a
75.1a 75.2a
6.2a 7.0a
105.0a 104.3a
112.1a 112.3a
119.1a 120.2a
4.9a 5.4a
70.5a
6.9a
117.1b
123.3b
129.6a
6.7a
1
(Jg
1
(Jg
)
)
To, onset temperature; Tp, peak temperature; Tc, conclusion temperature: DH, enthalpy (db). Means in the same column with different superscript were significantly different at p 0.05.
a
a
WAC (g/g)
1.8 1.4 1.0 French Yellow
c
OAC (g/g)
Peak II
a
2.2
Contendor Master Bean Cultivar
Local Red
3.0 2.6
Peak I
a
2.6
Table 4 Thermal properties of flours from different kidney bean cultivars (n ¼ 2).
French Yellow Contender Master Bean Local Red
5
pH
3.6.1. Protein solubility Protein solubility is the most critical factor influencing the functional properties such as emulsification, foaming and gelation (Kinsella, 1976). The protein solubility profiles of kidney bean flours as a function of pH are presented in Fig. 2. The data indicated minimum solubility (6.8e7.8%) occurred at pH 4.0 with an average value of 7.1%. This is because solubility markedly decreases near the isoelectric point, generally between pH 4 and pH 6 for most pulses. A dramatic increase in protein solubility was observed on either side of pH 4 and 5. At pH 2 about 73.3e80.3% of protein was soluble, and about 95.3e97.8% of proteins was soluble at pH 10. Generally, the protein solubility profiles against pH of all four flours were similar to each other and in agreement with previously reported legume fours (Chau & Cheung, 1998; Dzudie & Hardy, 1996).
Cultivar
4
b
a
a
French Yellow
Contendor
Master Bean
a
2.2 1.8 1.4 1.0 Local Red
Cultivar Fig. 2. (a) Protein solubility profile of kidney bean flours of French yellow (A); Contendor (-); Master Bean (:); Local Red (╳) at different pH values: (b) Water absorption capacity of kidney bean flours: (c) Oil absorption capacity of kidney bean flours.
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3.6.3. Foaming capacity and stability Flours are capable of producing foams due to surface active proteins (Adebowale & Lawal, 2003). Foaming capacity of kidney bean flour has been presented in Table 5. Foaming capacity of kidney bean flours at pH 2, 4, 6, 8 and 10 varied from 82.1e122.2, 92.5e105.8, 134.6e143, 100.0e109.5 and 103.8e132.0%, respectively. Change in pH significantly (p 0.05) influenced the foaming capacities of flours. Chau and Cheung (1998) reported foaming capacity of different legume flours from 64.4 to 140% under different pH conditions. Foam stability of 2% (w/v) flour suspensions at various pH was studied over a period of 12 h. The foam volume decreased with increase in time as shown in Fig. 3 for cultivar Contendor. Half-life values of foam for different cultivars showed similar results. Maximum foam stability was observed at pH 4e6. The half-life values were low when pH was below or higher than this range. It indicated that kidney bean flour will not be suitable for its foaming properties in highly acidic product. The foam stability of Master bean and Local red was higher than Contendor followed by Frenck Yellow. Statistical analysis revealed a significant (p < 0.05) difference in foam stability as the pH varied from 2 to 10. The higher foam stability at pH 4 and 6 compared to those in the other pH conditions might be due to the more stable protein conformations at their isoelectric points (Yatsumatsu et al., 1972). 3.6.4. Emulsifying properties Emulsifying properties including EAI and ESI of kidney bean flours at different pH are presented in Table 5. EAI varied Table 5 Foaming and emulsifying properties of kidney bean flour (n ¼ 3). Property
pH Cultivars French Yellow Contendor
2 82.1 3.6a 4 92.5 3.6a 6 134.6 3.8a 8 109.5 1.8b 10 132.0 3.5c Half life of 2 1.77 0.1a foam (Hours) 4 8.53 0.9a 6 9.53 0.8a 8 0.32 0.0a 10 1.38 0.1b 3 25.2 1.5c Emulsifying activity 5 6.0 1.3a index (m2/g) 7 17.0 1.5b 3 15.5 0.2a Emulsifying stability 5 23.7 2.3a index (min.) 7 26.4 1.9c
Foaming capacity (%)
92.3 109.8 132.7 109.5 103.8 6.70 10.68 8.60 0.47 1.51 13.2 6.3 14.6 32.3 25.6 22.7
0.3b 1.8b 1.9a 2.1b 3.8a 0.2b 0.4b 0.8a 0.1b 0.2b 0.2a 1.1a 1.6a 2.3c 2.8a 2.3ab
MasterBean 118.8 104.0 136.0 118.0 142.0 6.59 12.00 11.68 0.58 0.68 17.2 7.3 17.9 19.1 73.9 19.4
3.4c 4.0b 4.0a 2.0c 4.0d 0.1b 0.0c 0.4b 0.1b 0.0a 1.6b 0.3ab 0.3b 1.6b 2.3c 1.2a
Local Red 122.2 105.8 143.0 100.0 118.8 1.83 7.77 12.00 0.52 1.77 16.6 8.9 18.9 33.6 46.0 24.6
0.4c 1.9b 3.0b 3.8a 3.4b 0.1a 0.8a 0.0c 0.1b 0.1c 1.7b 0.6b 0.7b 1.6c 2.1b 1.7bc
Values expressed are mean standard deviation. Means in the rows with different superscript are significantly different at p 0.05.
120 100 80 Foam (%)
2.2e2.7 L/kg, respectively. The major chemical compositions that enhance the WAC of flours are proteins and carbohydrates, since these constituents contain hydrophilic parts, such as polar or charged side chains. Oil absorption capacity (OAC) of flour varied from 2.2 to 2.3 kg/kg (Fig. 2). OAC of French Yellow flour was significantly (p 0.05) higher than other flours. However, these results are lower than those reported by Aguilera et al. (2011) and Siddiq et al. (2010) for kidney bean flour. OAC is another important functional property of flours, since it plays an important role in enhancing the mouth feel and retaining the flavour (Kinsella, 1976). The major chemical component affecting OAC is protein, which is composed of both hydrophilic and hydrophobic parts. Non-polar amino acid side chains can form hydrophobic interactions with hydrocarbon chains of lipid. Non-polar amino acid side chains can form hydrophobic interactions with hydrocarbon chains of lipids.
283
60 40 20 0 0
1
2
3
4
5
6 7 8 Time (h)
9
10 11 12 13
Fig. 3. Foam stability of kidney bean cv Contendor flour at pH 2 (A), pH 4 (-); pH 6 (:); pH 8 (╳); pH 10 ( ).
significantly (p 0.05) among the cultivars at different pH. At pH 3 EAI varied from 13.2 to 25.2 m2/g, cultivar French Yellow showed the highest value and Contendor showed the lowest value. At pH 5 EAI varied from 6.0 to 8.9 m2/g, while the highest value was shown by Local Red flour. At pH 7 EAI was in the range of 14.6e18.9 m2/g, Contendor showed significantly (p 0.05) lower value than other cultivars. Lower EAI at pH 5 than other pH’s may be due to the isoelectric point of legume proteins. The difference in total protein composition and non-proteins (possibly carbohydrates), may contribute substantially to the emulsification properties of proteincontaining products like legume flours (McWatters & Cherry, 1977). Protein can emulsify and stabilise the emulsion by decreasing surface tension of the oil droplet and providing electrostatic repulsion on the surface of the oil droplet (Sikorski, 2002), while some types of polysaccharides can help stabilise the emulsion by increasing the viscosity of the system (Dickinson, 1994). ESI at different pH varied significantly (p 0.05) among the cultivars. At pH 3 it varied between 15.5 and 33.6, while as it was in the range of 23.7e73.9 and 19.4e26.4 for pH 5 and 7 respectively. Sanjeewa, Wanasundara, Pietrasik, and Shand (2010) reported ESI of 15.95e28.55 for different chickpea flours. 4. Conclusions The study showed significant differences in composition and physicochemical properties among the kidney bean flours. Flours have high setback viscosity and synaeresis suggesting that they cannot be used in products requiring refrigerated storage. WAC and OAC of flours were very good making them potentially useful in flavour retention, improvement of palatability and extension of shelf life in meat products. Flours also displayed very good foaming capacity. Foam stability was higher at pH 4 and 6. The highest EAI was observed at pH 7 while the highest ESI was observed at pH 5. Thus flours can be used in food formulations requiring foaming and emulsifying properties. References Adebooye, O. C., & Singh, V. (2008). Physico-chemical properties of the flours and starches of two cowpea varieties (Vigna unguiculata L. Walp). Innovative Food Science and Emerging Technologies, 9, 92e100. Adebowale, K. O., & Lawal, O. S. (2003). Foaming, gelation and electrophoretic concentrate. Food Chemistry, 83, 237e246. Adebowale, K. O., & Lawal, O. S. (2004). Comparative study of the functional properties of bambarra groundnut (Voandzeia subterranean), jack bean
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(Canavalia ensiformis) and mucuna bean (Mucuna pruriens) flours. Food Research International, 37, 355e365. Aguilera, Y., Esteban, R. M., Benitez, V., Mollá, E., & Martín-Cabrejas, M. A. (2009). Starch, functional properties, and microstructural characteristics in chickpea and lentil as affected by thermal processing. Journal of Agricultural and Food Chemistry, 57, 10682e10688. Aguilera, Y., Estrella, I., Benitez, V., Esteban, R. M., & Martín-Cabrejas, M. A. (2011). Bioactive phenolic compounds and functional properties of dehydrated bean flours. Food Research International, 44, 774e780. Ahmadi-Abhari, S., Woortman, A. A. J., Hamer, R. J., Oudhuis, A. A. C. M. & Loos, K. Influence of lysophosphatidylcholine on the gelation of diluted wheat starch suspensions. Carbohydrate Polymers, in press. Anton, A. A., Ross, K. A., Lukow, O. M., Fulcher, R. G., & Arntfield, S. D. (2008). Influence of added bean flour (Phaseolus vulgaris L.) on some physical and nutritional properties of wheat flour tortillas. Food Chemistry, 109(1), 33e41. AOAC. (1990). Official methods of analysis (15th ed.). Washington, DC: Association of Official Analytical Chemists. Chau, C. F., & Cheung, P. C. K. (1998). Functional properties of flours prepared from three Chinese indigenous legume seeds. Food Chemistry, 61(4), 429e433. Chung, H. J., Liu, Q., Pauls, K. P., Fan, M., & Yada, R. (2008). In vitro starch digestibility, expected glycemic index and some physicochemical properties of starch and flour from common bean (Phaseolus vulgaris L.) varieties grown in Canada. Food Research International, 41(9), 869e875. Del Rosario, R. R., & Pontiveros, C. R. (1983). Retrogradation of some starch mixtures. Starch Starke, 35, 86e92. Dickinson, E. (1994). Protein-stabilized emulsions. Journal of Food Engineering, 22, 59e74. Dzudie, T., & Hardy, J. (1996). Physicochemical and functional properties of flours prepared from common beans and green beans. Journal of Agriculture and Food Chemistry, 44, 3029e3032. Ghavidel, R. A., & Prakash, J. (2006). Effect of germination and dehulling on functional properties of legume flours. Journal of the Science of Food and Agriculture, 86, 1189e1195. Ghiasi, K., Varriano-Marston, K., & Hoseney, R. C. (1982). Gelatinization of wheat starch. II. Starch-surfactant interaction. Cereal Chemistry, 59, 86. Han, J., Janz, J. A. M., & Gerlat, M. (2010). Development of gluten free cracker snacks using pulse flours and fractions. Food Research International, 43, 627e633. Hermansson, A. M., & Svegmark, K. (1996). Developments in the understanding of starch functionality. Trends in Food Science & Technology, 7, 345e353. http://faostat.fao.org/site/567/DesktopDefault.aspx?PageID¼567#ancor. Hung, T. V., Papalois, M., Nithianandan, V., Jiang, H. H., & Versteeg, K. (1990). Utilisation of lupin seeds for human consumptionIn ‘‘Food Pacific’’ convention. Gold Coast: AIFST/NZIFST, Bond University. Jayakody, L., Lan, H., Hoover, R., Chang, P., Liu, Q., & Donner, E. (2007). Composition, molecular structure, and physicochemical properties of starches from two grass pea (Lathyrus sativus L.) cultivars grown in Canada. Food Chemistry, 105, 116e125. Kinsella, J. E. (1976). Functional properties of proteins in foods: a survey. Critical Reviews in Food Science and Nutrition, 7, 219e232. Leach, H. W., Mc Cown, L. D., & Schoch, T. J. (1959). Structure of the starch granule I. Swelling and solubility patterns of various starches and flours. Cereal Chemistry, 36, 535e545. Lowry, O. H., Rosebrough, N. J., Farr, A. L., & Randall, R. J. (1951). Protein measurement with the Folin phenol reagent. Journal of Biological Chemistry, 193, 265e275.
Luyten, H., van Vliet, T., & Walstra, P. (1992). Comparison of various methods to evaluate fracture phenomena in food materials. Journal of Texture Studies, 23(3), 245e266. McWatters, K. H. (1983). Physical and sensory characteristics of Akara processed from cowpea paste and Nigerian cowpea flour. Cereal Chemistry, 60, 333e336. McWatters, K. H., & Cherry, J. P. (1977). Emulsification, foaming and protein solubility properties of defatted soybean, peanut, fieldpea and pecan flours. Journal of Food Science, 42, 1444e1450. Njintang, Y. N., Mbofung, C. M. F., & Waldron, K. W. (2001). In vitro protein digestibility and physico-chemical properties of dry red bean (Phaseolus vulgaris) flour: effect of processing and incorporation of soybean and cowpea flour. Journal of Agricultural and Food Chemistry, 49, 2465e2471. Osorio-Diaz, P., Bello-Perez, L. A., Sayago-Ayerdi, S. G., Benitez-Reyes, M. D., Tovar, J., & Paredes-Lopez, O. (2003). Effect of processing and storage timenon in vitro digestibility and resistant starch content of two bean (Phaseolus vulgaris) varieties. Journal of Science of Food and Agriculture, 83, 1283e1288. Pearce, K. N., & Kinsella, J. E. (1978). Emulsifying properties of proteins: evaluation of a turbidimetric technique. Journal of Agricultural and Food Chemistry, 26, 716e723. Rui, X., Boye, J. I., Ribereau, S., Simpson, B. K., & Prasher, S. O. (2011). Comparative study of the composition and thermal properties of protein isolates prepared from nine Phaseolus vulgaris legume varieties. Food Research International, 44(8), 2497e2504. Sanjeewa, W. G. T., Wanasundara, P. D. J., Pietrasik, Z., & Shand, J. P. (2010). Characterization of chickpea (Cicer arietinum L.) flours and application in low-fat pork bologna as a model system. Food Research International, 43, 617e626. Shimelis, E., Meaza, M., & Rakshit, S. (2006). Physico-chemical properties, pasting behavior and functional characteristics of flours and starches from improved bean (Phaseolus vulgaris L.) varieties grown in East Africa. Agricultural Engineering International: CIGR Ejournal, VIII, Manuscript FP 05 015. Siddiq, M., Ravi, R., Harte, J. B., & Dolan, K. D. (2010). Physical and functional characteristics of selected dry bean (Phaseolus vulgaris L.) flours. LWT e Food Science and Technology, 43, 232e237. Sikorski, Z. E. (2002). Proteins. In Z. E. Sikorski (Ed.), Chemical and functional properties of food components (pp. 133e178). Florida: CRC Press, Inc. Singh, J., Mc-Carthy, O. J., & Singh, H. (2006). Physico-chemical and morphological characteristics of New Zealand Taewa (Maori potato) starches. Carbohydrate Polymers, 64, 569e581. Singh, G. D., Wani, A. A., Kaur, D., & Sogi, D. S. (2008). Characterisation and functional properties of protein of some chickpeas (Cicer arietinum) cultivars. Journal of Science of Food and Agriculture, 88(5), 778e786. Sotomayor, C., Frias, J., Fornal, J., Sadowska, J., Urbano, G., & Vidal-Valverde, C. (1999). Lentil starch content and its microscopical structure as influenced by natural fermentation. Starch/Starke, 51(5), 152e156. Wani, A. A., Singh, P., Shah, M. A., Weisz, U. S., Gul, K., & Wani, I. A. (2012). Rice starch diversity: effects on structural, morphological, thermal, and physicochemical properties e a review. Comprehensive Reviews in Food Science & Safety, 11(5), 417e436. Wani, I. A., Sogi, D. S., Wani, A. A., Gill, B. S., & Shivhare, U. S. (2010). Physicochemical properties of starches from Indian kidney bean (Phaseolus vulgaris) cultivars. International Journal of Food Science and Technology, 45, 2176e2185. Yatsumatsu, K., Sawada, K., Moritaka, S., Misaki, M., Toda, J., Wada, T., et al. (1972). Whipping and emulsifying properties of soybean products. Agricultural and Biological Chemistry, 36, 719e727.
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LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt
Physico-chemical and functional properties of flours from Indian kidney bean (Phaseolus vulgaris L.) cultivars Idrees Ahmed Wani a, b, Dalbir Singh Sogi a, *, Ali Abas Wani c, Balmeet Singh Gill a a
Department of Food Science and Technology, Guru Nanak Dev University, Amritsar 143 005, India Department of Food Science and Technology, University of Kashmir, Hazratbal, Srinagar 190 006, India c Department of Food Technology, Islamic University of Science and Technology, Awantipora, Kashmir 190 221, India b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 10 May 2012 Received in revised form 25 January 2013 Accepted 5 February 2013
Flours of four kidney bean (Phaseolus vulgaris L.) cultivars (French Yellow, Contendor, Master Bean and Local Red) were studied. The moisture, ash, protein, fat and crude fibre contents of kidney bean flours varied from 99e104, 30e35, 223e267, 16e20 and 14e21 g/kg, respectively. Synaeresis of flour gels increased from 141 g/kg after 24 h to 194 g/kg after 120 h of storage at 4 C. Scanning electron microscopy of flours revealed starch granules of varied shapes associated with protein and non-protein components. Peak, breakdown and setback viscosity varied significantly (p 0.05) from 591.0e1030.3 cP, 21.3e93.3 cP and 383.7e750.0 cP, respectively. Kidney bean flours displayed two endothermic transitions corresponding to starch gelatinization (60.9e75.2 C) and disruption of the amyloseelipid complex (103.6e129.6 C). Hardness and adhesiveness of flour gels varied significantly from 14.9e19.5 g and 31.5 e81.3 g, respectively. Foaming capacity and foaming stability at different pH showed significant differences. Emulsion activity index at different pH varied from 6.03 to 25.21 m2/g while emulsion stability index was in the range of 15.51e76.21 min. Protein solubility of 8.1e97.8% was observed in the pH range of 2e10. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Kidney bean Flour Pasting properties Emulsifying Foaming Gel texture
1. Introduction Common dry bean (Phaseolus vulgaris L.) is one of the most important crops of the world with different physical, biochemical and sensory properties. The global production of the dry beans in 2010 was 22.9 million metric tonnes and five leading producers were India, Brazil, Myanmar, United States and Mexico (FAO, 2012). The different classes of common dry bean include black bean, cranberry bean, great northern bean, kidney bean, navy bean, pinto bean and small red bean. Kidney bean is one of the most important legume crops of northern India. Kidney beans are good source of protein, starch and dietary fibres (Osorio-Diaz et al., 2003). Physico-chemical properties of kidney beans change with postharvest handling and storage conditions resulting in a reduction in their cooking, eating and nutritional quality as well as consumer acceptance (Njintang, Mbofung, & Waldron, 2001). Consumption of kidney beans could be improved by processing them into flour (Dzudie & Hardy, 1996). It can satisfy the nutritional requirements of consumers especially in developing countries because of growing urbanization (Njintang et al., 2001). * Corresponding author. Tel.: D91 183 2258802x3217; fax: þ91 183 2258820. E-mail address: [email protected] (D.S. Sogi). 0023-6438/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.lwt.2013.02.006
Interest in the utilization of flours from different types of legumes is growing (Chau & Cheung, 1998; Siddiq, Ravi, Harte, & Dolan, 2010) which depend on their functional properties (Hung, Papalois, Nithianandan, Jiang, & Versteeg, 1990; Singh, Wani, Kaur, & Sogi, 2008). These include foaming, emulsification, texture, gelation, water/oil absorption capacities and viscosity (Adebowale & Lawal, 2004). The functional properties of legume flours mainly depend on proteins, carbohydrates and other components. Hydration properties, binding, swelling, dispersibility and viscosity are known to directly influence the characteristics of a food system (McWatters, 1983). The application of legume flours as functional ingredients in some foods such as breads, cakes, biscuits, doughnuts, tortillas, pasta, and snacks has been reported by several authors (Anton, Ross, Lukow, Fulcher, & Arntfield, 2008; Han, Janz, & Gerlat, 2010). The objectives of the present study were to assess the physico-chemical and functional properties of kidney bean flours from locally available cultivars. 2. Materials and methods 2.1. Materials The seeds of three kidney bean (Phaseolus vulgaris L) cultivars e French Yellow, Contendor, and Master Bean were procured from
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Sher-e-Kashmir University of Agricultural Sciences and Technology, Shalimar, Srinagar, J&K, India, whereas, Local Red cultivar was procured from the local market of Srinagar, J&K, India. Seeds were cleaned manually from the dirt, foreign material etc. and stored until further use at 20 C. All the reagents used in the study were of analytical grade.
279
Warriewood, Australia). An aqueous dispersion of flour e 14% moisture basis (12.28%, w/w; 28.5 g total weight) was equilibrated at 50 C for 1 min, heated at the rate of 12.2 C/min to 95 C, held for 2.5 min, cooled to 50 C at the rate of 11.8 C/min and again held at 50 C for 2 min. A constant paddle rotational speed (160 rpm) was used throughout the entire analysis, except for rapid stirring at 960 rpm for the first 10 s to disperse the sample.
2.2. Flour preparation Seeds were ground in a laboratory mill (Newport Supermill1500, Newport Scientific Pvt. Ltd, Warriewood, Australia), sieved through 60-mesh screen and stored in airtight containers at refrigerated temperature until used. 2.3. Physico-chemical properties 2.3.1. Composition Moisture (925.10), protein (920.87), fat (920.85), crude fibre (978.10) and ash (923.03) contents were determined according to standard methods of AOAC (1990). 2.3.2. Bulk density Bulk density was measured as a ratio of mass to volume. A graduated cylinder, previously tarred, was gently filled upto 10 ml mark with flour. The sample was then packed by gently tapping the cylinder on the bench top from a height of five cm until there was no further diminution of the sample level and noted the volume. The weight of the filled cylinder was taken and the bulk density was calculated as the weight of sample per unit volume (kg/L). 2.3.3. Swelling & solubility index Swelling power and solubility of the flour were determined using 2% w/v (db) aqueous suspension of flour at 90 C (Leach, Mc Cown, & Schoch, 1959). 2.3.4. Synaeresis Synaeresis was measured as percentage of water released from 2% w/w (db) flour gel stored at 4 C for 1, 2 and 5 days after centrifugation at 3000 g for 10 min (C-24 BL, Remi, Mumbai, India). 2.3.5. Colour The surface colour of flours was measured using Hunter Colour Lab (Hunter Associates Laboratory Inc., Reston, VA, USA). A glass cell containing uniformly sized flour was placed against the light source, covered with a black cover and L (Lightness), a (red-green), and b (yelloweblue) values were recorded. The instrument was calibrated with black and white tile before colour measurement. Total colour difference (DE) was calculated as:
h
DE ¼ ðDLÞ2 þ ðDaÞ2 þ ðDbÞ2
i1=2
2.4. Scanning electron microscopy The flour was placed on an adhesive tape attached to a circular aluminium specimen stub and then coated vertically with golde palladium. The samples were photographed at an accelerator potential of 10 kV using a scanning electron microscope (JSM-6100, JEOL Ltd, Tokyo, Japan). 2.5. Pasting properties The pasting properties of the flours were measured using a Rapid Visco Analyzer (RVA-4, Newport Scientific Pty Ltd,
2.6. Flour gel texture Textural properties of the gels were evaluated with slight modifications to the methods of Singh, Mc-Carthy, and Singh (2006) as described by Wani, Sogi, Wani, Gill, and Shivhare (2010). 2.7. Thermal properties Thermal properties of kidney bean flours were analysed using DSC (200 PC-Phox Phoenix, Netzsch, Burlington, Germany) equipped with a thermal analysis data station. A 10 mg sample was weighed into a 40 ml capacity aluminium pan and 20 ml distilled water was added with the help of Hamilton micro syringe. Pans were hermetically sealed and allowed to stand for 1 h at room temperature before heating in DSC. The DSC was calibrated using indium and an empty aluminium pan was used as reference. Sample pans were heated at a rate of 10 oC/min from 20 to 180 C and thermal parameters viz. onset (To), peak (Tp), conclusion (Tc) temperature and enthalpy (DH) were calculated from the DSC curves. 2.8. Functional properties 2.8.1. Protein solubility Protein solubility was determined in the pH range 2e10 using 0.1% w/v flour aqueous dispersion. The suspensions were adjusted to the desired pH, solubilised by shaking at 210 rpm at 25 C for 60 min in a shaking incubator (LSI-3016R, Daihan Lab Tech Co., Ltd., Namyangju, Kyonggi, Korea) and then centrifuged at 12,000 g for 10 min. The protein content of the supernatant was determined by the Lowry method (Lowry, Rosebrough, Farr, & Randall, 1951) using bovine serum albumin (BSA) as standard. 2.8.2. Water and oil absorption capacity To determine water and oil absorption capacity 1 g (db) of sample was weighed into 25 ml pre-weighed centrifuge tubes and then stirred into 10 mL of double distilled water or refined soyabean oil (Amrit Banaspati Co. Ltd., Rajpura, Punjab, India) for 1 min. The samples were allowed to stand for 30 min and then centrifuged at 2200 g for 30 min. The water or oil released on centrifugation was drained. Water or oil absorption capacity was expressed as kg of water or oil held per kg of flour sample. 2.8.3. Foaming capacity and stability Aqueous dispersions (2% w/v db) of the flour at pH 2, 4, 6, 8 and 10 were homogenized in a high speed homogenizer (Remi Instruments Division, Vasai, India) at 10,000 rpm for 1 min. Foaming capacity was calculated as the percent increase in volume of the flour dispersion. The foam stability was determined by measuring the foam volume with time and computing half-life. 2.8.4. Emulsifying properties Emulsifying activity index (EAI) and emulsifying stability index (ESI) were determined by turbidimetric method described by Pearce and Kinsella (1978).
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2.9. Statistical analysis The data reported are averages of triplicate observations. An analysis of variance with a significance level of 5% was done, and Duncan’s test was applied to determine the differences between means using the commercial statistical package (SPSS Inc, Chicago, IL, USA). 3. Results and discussion 3.1. Physico-chemical properties The composition of kidney bean flours is presented in Table 1. The moisture content of kidney bean flours was in the range of 99e 104 g/kg. Ash and protein contents varied from 30e35 g/kg and 223e267 g/kg respectively. Fat and crude fibre contents varied from 16e20 g/kg and 14e20 g/kg respectively. Significant (p 0.05) differences were observed in ash, protein, fat, and crude fibre contents among the four bean cultivar. Dzudie and Hardy (1996) reported similar results for the composition of kidney bean flour. Bulk density of kidney bean flours (Table 1) ranged from 0.84 to 0.94 kg/L. Ghavidel and Prakash (2006) reported bulk density value of 0.86 kg/L for lentil flour. However, results obtained in present study were higher than those reported by Dzudie and Hardy (1996) and Siddiq et al.. (2010) for bulk density of kidney beans flours, which might be due to difference in particle size and packing behaviour. Swelling index of kidney bean flour varied from 6.6 to 8.2 kg/kg (Table 1). It was the highest for French Yellow and the lowest for Master Bean flour. Adebooye and Singh (2008) reported swelling index of cowpea flour in the range of 8.0e11.0 kg/kg. Swelling index of flour is related to gelatinisation of starch reflecting breaking of intramolecular hydrogen bonds in the crystalline regions and uptake of water by hydrogen bonding; water absorption by nonstarch polysaccharides and proteins. Solubility index of kidney beans flours was in the range of 320e363 g/L. Shimelis, Meaza, and Rakshit (2006) reported similar results for solubility index (335e 378 g/L). Solubility index is related to the presence of soluble molecules like amylose and albumins in the flour. Significant (p 0.05) differences were observed in swelling and solubility indices of kidney bean flour cultivars. Synaeresis increased from 134 to 197 g/kg among the cultivars during 120 h of storage at 4 C (Table 1). Synaeresis might be Table 1 Physico-chemical properties of some kidney bean flour (n ¼ 3). Parameter
Cultivars French Yellow Contendor
Moisture, g/kg Protein, g/kg Fat, g/kg Ash, g/kg Crude fibre g/kg Bulk density, kg/L Swelling index, g/L Solubility index, g/L Synaeresis, g/kg 24 h. 48 h. 120 h. Colour values L a b DE
99 231 20 30 17 0.85 8.2 320
1.2a 8.5a 1.1b 0.1a 0.5b 0.01a 0.18d 0.1a
153 0.1a 157 2.5b 187 2.8bc 81.1 1.8 9.6 85.6
0.24a 0.02d 0.06c 0.21a
102 223 19 35 21 0.84 7.0 333
3.4a 4.4a 0.9ab 0.4b 0.1c 0.01a 0.01b 0.5b
165 0.6c 175 0.2c 197 5.5c 82.0 1.3 9.5 86.3
0.28a 0.06a 0.11c 0.22a
Master Bean 100 267 18 34 14 0.94 6.6 363
151 6.6b 160 3.2b 168.1 0.4a 81.5 1.4 9.3 85.9
Local Red
3.3a 104 4.4a 4.4b 267 4.4b 1.1ab 16 2.5a 1.7b 35 0.4b 0.8a 16 1.5b 0.01c 0.88 0.01b 0.15a 7.4 0.06c 3.0c 322 6.0a 134 2.6a 138 0.4a 180 8.3b
1.05a 81.6 0.27a 0.03c 1.3 0.01b 0.10b 7.9 0.06a 0.87a 85.7 0.22a
Values expressed are mean standard deviation. Means in the rows with different superscript are significantly different at p 0.05.
attributed to the interaction between leached out amylose and amylopectin chains leading to gel shrinkage, degree of polymerisation of amylose, amylopectin chain length, proportion of short chains or shrink back of partially disintegrated granules to their original size during cooling (Hermansson & Svegmark, 1996). Moreover, starches separated from kidney bean cultivars were found to have high amylose content (Wani et al., 2010). Hunter colour values (L, a, b and DE) of kidney bean flours are shown in Table 1. ‘L’ (lightness) values of flours varied insignificantly (p > 0.05) from 81.1 to 82.0 among the cultivars. Colour scale value of ‘a’ varied significantly (p 0.05) from 1.3 to 1.8 among the cultivars. Flours had ‘b’ value of 7.9e9.6, which was the highest in French Yellow and the lowest in Local Red. DE (total colour difference) varied from 85.6 to 86.3 for various kidney bean flours. Similar results for colour values of kidney bean flours were reported by Shimelis et al. (2006). 3.2. Scanning electron microscopy Shape of the Starch granules varied from ovoid to spherical, with heterogeneous sizes ranging from 10.0 to 35.0 mm in length and from 6.7 to 24.0 mm in width (Fig.1). The globular or irregular particles attached to or located between the starch granules were the protein bodies or fragments of protein matrix disrupted during milling. Particles might also have included mineral and fibre components, as reported by other workers (Aguilera, Esteban, Benitez, Mollá, & Martín-Cabrejas, 2009; Sotomayor et al., 1999). 3.3. Pasting properties Pasting properties of kidney bean flours are presented in Table 2. Peak viscosity of kidney bean flours was in the range of 591.0e 1030.3 cP. The highest peak viscosity was observed for the flour of French Yellow and the lowest for Master Bean cultivars. Values were in agreement with the highest and the lowest swelling index displayed by these cultivars (Table 1). Significantly (p 0.05) higher peak viscosity of French Yellow than rest of the cultivars could be attributed to its higher starch content. The yield of isolated starch from French Yellow was 30.2% compared to 27.2e28.7% in other cultivars on dry weight basis (data not reported). Trough or holding viscosity varied from 494.7 to 1009.3 cP, the highest value was observed for French Yellow and the lowest for Master Bean. Trough viscosity is influenced by the rate of amylose exudation, granule swelling and amyloseelipid complex formation (Wani, Singh, Shah, Weisz, Gul, Wani., 2012). Breakdown viscosity which is a measure of the ease with which the swollen starch granules can be disintegrated was in the range of 21.3e93.3 cP. The highest breakdown viscosity was observed in Master Bean and the lowest in French Yellow flours. Significant (p 0.05) differences were observed in trough and breakdown viscosities of kidney bean flours. Final viscosity varied significantly (p 0.05) among the cultivars and was in the range of 952.0e1611.7 cP. French Yellow had the highest final viscosity and Local Red had the lowest. This could be attributed to the highest and the lowest amylose content found in the starch of these cultivars as reported by the authors in their previous study (Wani et al., 2010). All the flours showed a gradual increase in viscosity with increase in temperature. The increase in viscosity with temperature may be attributed to the binding of water to exuded amylose from the granules during swelling and further uptake of water by the granules due to increase porosity or channel from water migration (Ghiasi, Varriano-Marston, & Hoseney, 1982). Setback viscosity, a measure of retrogradation tendency of flours gels on cooling varied significantly (p 0.05) from 338.7e750.0 cP. Retrogradation is the result of hydrogen bonding between starch molecules that have both hydroxyl and hydrogen acceptor sites
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Fig. 1. Scanning electron micrographs of kidney bean flours of (a) French Yellow, (b) Contendor, (c) Master Bean, (d) Local Red.
This could be attributed to its lowest amylose content as reported in our previous results (Wani et al., 2010). The extent of amylose gel network and deformability of swollen granules are reported as the main factors contributing to gel strength (Luyten, van Vliet, & Walstra, 1992). Cohesiveness, gumminess, springiness and chewiness did not show any significant (p 0.05) differences among the cultivars. Adhesiveness ranged from 27.7 to 87.7 gs. Master Bean and Local Red cultivars showed significantly (p 0.05) lower adhesiveness than French Yellow and Contendor flours.
(Del Rosario & Pontiveros, 1983). The amylose fraction of starch is believed to be responsible for retrogradation, since amylose molecules are free to orient themselves together than are the amylopectin molecules. Retrogradation rate is affected by amylose and amylopectin concentrations, molecular size, temperature and pH. Pasting temperature, the temperature at the onset of rise in viscosity varied from 80.6 to 84.5 C, the highest value was observed for Local Red and the lowest for Contendor flours. Significantly (p 0.05) higher protein content of Local Red than French Yellow and Contendor flours could induce increased proteinestarch interaction and consequently tends to retard swelling leading to increase in pasting temperature.
3.5. Thermal properties The thermal properties of kidney bean flours are shown in Table 4. Thermo grams of kidney bean flour displayed two endothermic peaks. The first peak at lower temperature was due to starch gelatinization, and the second peak at a higher temperature is due to amyloseelipid complexation. Starch gelatinization parameters varied from 63.0e69.2 C; 67.2e73.3 C; 70.5e77.4 C and 4.9e6.7 J g1, respectively for To, Tp, Tc and DH. The gelatinization transition temperatures are reported to be influenced by amylose
3.4. Flour gel texture The textural properties like hardness, cohesiveness, gumminess, springiness, chewiness and adhesiveness of kidney bean flour gels were determined on a texture analyzer (Table 3). Gel hardness varied from 14.9 to 19.5 g for kidney bean cultivars. Local Red flour showed significantly (p 0.05) lower hardness than other cultivars.
Table 2 Pasting properties of flours from different kidney bean cultivars (n ¼ 3). Cultivars
Peak viscosity (cP)
French Yellow Contendor Master Bean Local Red
1030.3 673.0 591.0 603.7
21.7b 43.6a 37.0a 47.5a
Trough viscosity (cP) 1009.3 604.3 494.7 568.3
20.9c 39.1b 14.2a 53.1ab
Breakdown viscosity (cP) 21.3 68.7 93.3 35.3
2.1a 4.5bc 40.7c 6.7ab
Values expressed are mean standard deviation. Means in the column with different superscript were significantly different at p 0.05.
Final viscosity (cP) 1611.7 1308.0 1244.7 952.0
61.6c 66.8b 25.2b 48.0a
Setback viscosity (cP) 602.7 703.7 750.0 383.7
43.5b 38.7bc 11.5c 6.4a
Pasting temperature ( C) 81.7 80.6 84.0 84.5
0.9a 0.8a 0.8b 1.7b
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Table 3 Texture analysis of kidney bean flour gels after 24 h of storage at 4 C (n ¼ 3). Cultivars
Hardness (g)
French Yellow Contender Master Bean Local Red
17.8 19.5 18.7 14.9
Cohesiveness
2.5b 0.9b 0.6b 0.3a
0.3 0.3 0.3 0.3
Gumminess (g)
0.1a 0.1a 0.0a 0.0a
5.7 5.9 5.7 3.9
Springiness
1.6a 1.3a 0.1a 0.8a
0.9 0.7 1.1 1.1
Chewiness (g)
0.4a 0.1a 0.3a 0.0a
5.6 4.2 6.3 4.4
Adhesiveness (gs)
3.3a 1.6a 1.5a 0.8a
81.3 87.7 27.7 31.5
19.1b 14.3b 8.3a 10.3a
Values expressed are mean standard deviation. Means in the column with different superscript are significantly different at p 0.05.
3.6.2. Water and oil absorption capacity Water absorption capacity (WAC) of kidney bean flour varied insignificantly (p > 0.05) from 2.6 to 2.7 kg/kg of flour (Fig. 2). Water absorption capacity is important for certain product characteristics, such as the moistness of the product, starch retrogradation, and the subsequent product staling. Siddiq et al. (2010) and Aguilera, Estrella, Benitez, Esteban, and Martín-Cabrejas (2011) reported WAC of kidney bean flour from 2.2 to 2.7 kg/kg and
a 100 90 Protein solubility (%)
content, distribution of amylopectin branch chains, lipid complexed amylose chains, and protein content (Jayakody et al., 2007). The second endothermic peak around 104e130 C represented the amyloseelipid complexation. Significantly (p 0.05) higher melting temperature (To and Tp) was observed for Local Red cultivar. However, there was no significant difference in Tc among the cultivars. The melting enthalpy (DH) of second endothermic transition did not show significant differences among the cultivars. The second endothermic peak may be due to high amylose content (364e417 g/kg starch) of the flour samples which interacts with available lipids (16e20 g/kg flour) to delay gelatinization as also reported by (Wani et al., 2010). Previous reports on kidney bean protein denaturation further suggest that the second endothermic peak should be arising from starchelipid complexation (Rui, Boye, Ribereau, Simpson, & Prasher, 2011). It was reported that the peak denaturation temperature was 82.14e91.14 C for kidney bean proteins extracted from nine cultivars. However, similar findings on amyloseelipid complexation have been reported recently by Chung, Liu, Pauls, Fan, and Yada (2008) and Ahmadi-Abhari, Woortman, Hamer, Oudhuis, and Loos (in press). The amylosee lipid complexation influences the pasting, swelling and hydration properties of legume flours.
80 70 60
50 40 30 20 10 0 1
2
3
3.6. Functional properties
b
6
7
8
9
3.0
To ( C)
Tp ( C)
Tc ( C)
DH
69.2a
73.3a
77.4a
63.0a 60.9a
69.1a 67.2a
68.0a
69.3a
DH
To ( C)
Tp ( C)
Tc ( C)
6.8a
103.6a
111.0a
118.5a
5.9a
75.1a 75.2a
6.2a 7.0a
105.0a 104.3a
112.1a 112.3a
119.1a 120.2a
4.9a 5.4a
70.5a
6.9a
117.1b
123.3b
129.6a
6.7a
1
(Jg
1
(Jg
)
)
To, onset temperature; Tp, peak temperature; Tc, conclusion temperature: DH, enthalpy (db). Means in the same column with different superscript were significantly different at p 0.05.
a
a
WAC (g/g)
1.8 1.4 1.0 French Yellow
c
OAC (g/g)
Peak II
a
2.2
Contendor Master Bean Cultivar
Local Red
3.0 2.6
Peak I
a
2.6
Table 4 Thermal properties of flours from different kidney bean cultivars (n ¼ 2).
French Yellow Contender Master Bean Local Red
5
pH
3.6.1. Protein solubility Protein solubility is the most critical factor influencing the functional properties such as emulsification, foaming and gelation (Kinsella, 1976). The protein solubility profiles of kidney bean flours as a function of pH are presented in Fig. 2. The data indicated minimum solubility (6.8e7.8%) occurred at pH 4.0 with an average value of 7.1%. This is because solubility markedly decreases near the isoelectric point, generally between pH 4 and pH 6 for most pulses. A dramatic increase in protein solubility was observed on either side of pH 4 and 5. At pH 2 about 73.3e80.3% of protein was soluble, and about 95.3e97.8% of proteins was soluble at pH 10. Generally, the protein solubility profiles against pH of all four flours were similar to each other and in agreement with previously reported legume fours (Chau & Cheung, 1998; Dzudie & Hardy, 1996).
Cultivar
4
b
a
a
French Yellow
Contendor
Master Bean
a
2.2 1.8 1.4 1.0 Local Red
Cultivar Fig. 2. (a) Protein solubility profile of kidney bean flours of French yellow (A); Contendor (-); Master Bean (:); Local Red (╳) at different pH values: (b) Water absorption capacity of kidney bean flours: (c) Oil absorption capacity of kidney bean flours.
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3.6.3. Foaming capacity and stability Flours are capable of producing foams due to surface active proteins (Adebowale & Lawal, 2003). Foaming capacity of kidney bean flour has been presented in Table 5. Foaming capacity of kidney bean flours at pH 2, 4, 6, 8 and 10 varied from 82.1e122.2, 92.5e105.8, 134.6e143, 100.0e109.5 and 103.8e132.0%, respectively. Change in pH significantly (p 0.05) influenced the foaming capacities of flours. Chau and Cheung (1998) reported foaming capacity of different legume flours from 64.4 to 140% under different pH conditions. Foam stability of 2% (w/v) flour suspensions at various pH was studied over a period of 12 h. The foam volume decreased with increase in time as shown in Fig. 3 for cultivar Contendor. Half-life values of foam for different cultivars showed similar results. Maximum foam stability was observed at pH 4e6. The half-life values were low when pH was below or higher than this range. It indicated that kidney bean flour will not be suitable for its foaming properties in highly acidic product. The foam stability of Master bean and Local red was higher than Contendor followed by Frenck Yellow. Statistical analysis revealed a significant (p < 0.05) difference in foam stability as the pH varied from 2 to 10. The higher foam stability at pH 4 and 6 compared to those in the other pH conditions might be due to the more stable protein conformations at their isoelectric points (Yatsumatsu et al., 1972). 3.6.4. Emulsifying properties Emulsifying properties including EAI and ESI of kidney bean flours at different pH are presented in Table 5. EAI varied Table 5 Foaming and emulsifying properties of kidney bean flour (n ¼ 3). Property
pH Cultivars French Yellow Contendor
2 82.1 3.6a 4 92.5 3.6a 6 134.6 3.8a 8 109.5 1.8b 10 132.0 3.5c Half life of 2 1.77 0.1a foam (Hours) 4 8.53 0.9a 6 9.53 0.8a 8 0.32 0.0a 10 1.38 0.1b 3 25.2 1.5c Emulsifying activity 5 6.0 1.3a index (m2/g) 7 17.0 1.5b 3 15.5 0.2a Emulsifying stability 5 23.7 2.3a index (min.) 7 26.4 1.9c
Foaming capacity (%)
92.3 109.8 132.7 109.5 103.8 6.70 10.68 8.60 0.47 1.51 13.2 6.3 14.6 32.3 25.6 22.7
0.3b 1.8b 1.9a 2.1b 3.8a 0.2b 0.4b 0.8a 0.1b 0.2b 0.2a 1.1a 1.6a 2.3c 2.8a 2.3ab
MasterBean 118.8 104.0 136.0 118.0 142.0 6.59 12.00 11.68 0.58 0.68 17.2 7.3 17.9 19.1 73.9 19.4
3.4c 4.0b 4.0a 2.0c 4.0d 0.1b 0.0c 0.4b 0.1b 0.0a 1.6b 0.3ab 0.3b 1.6b 2.3c 1.2a
Local Red 122.2 105.8 143.0 100.0 118.8 1.83 7.77 12.00 0.52 1.77 16.6 8.9 18.9 33.6 46.0 24.6
0.4c 1.9b 3.0b 3.8a 3.4b 0.1a 0.8a 0.0c 0.1b 0.1c 1.7b 0.6b 0.7b 1.6c 2.1b 1.7bc
Values expressed are mean standard deviation. Means in the rows with different superscript are significantly different at p 0.05.
120 100 80 Foam (%)
2.2e2.7 L/kg, respectively. The major chemical compositions that enhance the WAC of flours are proteins and carbohydrates, since these constituents contain hydrophilic parts, such as polar or charged side chains. Oil absorption capacity (OAC) of flour varied from 2.2 to 2.3 kg/kg (Fig. 2). OAC of French Yellow flour was significantly (p 0.05) higher than other flours. However, these results are lower than those reported by Aguilera et al. (2011) and Siddiq et al. (2010) for kidney bean flour. OAC is another important functional property of flours, since it plays an important role in enhancing the mouth feel and retaining the flavour (Kinsella, 1976). The major chemical component affecting OAC is protein, which is composed of both hydrophilic and hydrophobic parts. Non-polar amino acid side chains can form hydrophobic interactions with hydrocarbon chains of lipid. Non-polar amino acid side chains can form hydrophobic interactions with hydrocarbon chains of lipids.
283
60 40 20 0 0
1
2
3
4
5
6 7 8 Time (h)
9
10 11 12 13
Fig. 3. Foam stability of kidney bean cv Contendor flour at pH 2 (A), pH 4 (-); pH 6 (:); pH 8 (╳); pH 10 ( ).
significantly (p 0.05) among the cultivars at different pH. At pH 3 EAI varied from 13.2 to 25.2 m2/g, cultivar French Yellow showed the highest value and Contendor showed the lowest value. At pH 5 EAI varied from 6.0 to 8.9 m2/g, while the highest value was shown by Local Red flour. At pH 7 EAI was in the range of 14.6e18.9 m2/g, Contendor showed significantly (p 0.05) lower value than other cultivars. Lower EAI at pH 5 than other pH’s may be due to the isoelectric point of legume proteins. The difference in total protein composition and non-proteins (possibly carbohydrates), may contribute substantially to the emulsification properties of proteincontaining products like legume flours (McWatters & Cherry, 1977). Protein can emulsify and stabilise the emulsion by decreasing surface tension of the oil droplet and providing electrostatic repulsion on the surface of the oil droplet (Sikorski, 2002), while some types of polysaccharides can help stabilise the emulsion by increasing the viscosity of the system (Dickinson, 1994). ESI at different pH varied significantly (p 0.05) among the cultivars. At pH 3 it varied between 15.5 and 33.6, while as it was in the range of 23.7e73.9 and 19.4e26.4 for pH 5 and 7 respectively. Sanjeewa, Wanasundara, Pietrasik, and Shand (2010) reported ESI of 15.95e28.55 for different chickpea flours. 4. Conclusions The study showed significant differences in composition and physicochemical properties among the kidney bean flours. Flours have high setback viscosity and synaeresis suggesting that they cannot be used in products requiring refrigerated storage. WAC and OAC of flours were very good making them potentially useful in flavour retention, improvement of palatability and extension of shelf life in meat products. Flours also displayed very good foaming capacity. Foam stability was higher at pH 4 and 6. The highest EAI was observed at pH 7 while the highest ESI was observed at pH 5. Thus flours can be used in food formulations requiring foaming and emulsifying properties. References Adebooye, O. C., & Singh, V. (2008). Physico-chemical properties of the flours and starches of two cowpea varieties (Vigna unguiculata L. Walp). Innovative Food Science and Emerging Technologies, 9, 92e100. Adebowale, K. O., & Lawal, O. S. (2003). Foaming, gelation and electrophoretic concentrate. Food Chemistry, 83, 237e246. Adebowale, K. O., & Lawal, O. S. (2004). Comparative study of the functional properties of bambarra groundnut (Voandzeia subterranean), jack bean
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