Accepted Manuscript. Pasting behaviour, textural properties and freeze thaw stability of wheat flour crude malva nut (Scaphium scaphigerum) gum system

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1 Accepted Manuscript Pasting behaviour, textural properties and freeze thaw stability of wheat flour crude malva nut (Scaphium scaphigerum) gum system Yuthana Phimolsiripol, Ubonrat Siripatrawan, C. Jeya K. Henry PII: S (11) DOI: /j.jfoodeng Reference: JFOE 6473 To appear in: Journal of Food Engineering Received Date: 5 December 2010 Revised Date: 14 March 2011 Accepted Date: 17 March 2011 Please cite this article as: Phimolsiripol, Y., Siripatrawan, U., Henry, C.J.K., Pasting behaviour, textural properties and freeze thaw stability of wheat flour crude malva nut (Scaphium scaphigerum) gum system, Journal of Food Engineering (2011), doi: /j.jfoodeng This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

2 1 2 Pasting behaviour, textural properties and freeze thaw stability of wheat flour crude malva nut (Scaphium scaphigerum) gum system 3 4 Yuthana Phimolsiripol a,*, Ubonrat Siripatrawan b, C. Jeya K. Henry c a Division of Product Development Technology, Faculty of Agro-Industry, Chiang Mai University, Chiang Mai 50100, Thailand b Department of Food Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand c Functional Food Centre, School of Life Sciences, Oxford Brookes University, Oxford, UK *Corresponding author. Tel: ; Fax: address: yphimols@chiangmai.ac.th (Y. Phimolsiripol)

3 ABSTRACT The effect of replacement of crude malva nut gum (CMG) at 0, 2.5, 5, 7.5 and 10% w/w on pasting behaviour, textural properties and freeze-thaw stability of wheat flour was investigated. Replacement of wheat flour by CMG significantly elevated (p<0.05) the peak viscosity ( RVU), hot paste viscosity ( RVU), breakdown ( RVU) and final viscosity ( RVU) of wheat flour pastes. Pasting temperature (59-85 o C) of the flour decreased with increasing CMG content. The textural parameters including hardness, springiness, cohesiveness, gumminess and chewiness of the mix gels decreased with higher level of CMG. Freeze thaw stability measurement revealed that wheat gel mixtures containing higher level (7.5 and 10%) of CMG decreased syneresis more than 80% after 3 freeze-thaw cycles, when compared to non-cmg sample. The rate of syneresis depended on CMG concentration and number of freeze-thaw cycles. The results demonstrated that higher viscosity, softer texture and lower syneresis of wheat gel could be attained using CMG Keywords: wheat flour; crude malva nut gum; pasting behaviour; textural property; freeze-thaw stability 2

4 Introduction Wheat flour is commonly used in food industries. Physicochemical properties such as gelatinization, retrogradation and textural properties of starch are affected by amylose and amylopectin molecular structures, ionic strength and the presence of other components such as sucrose, salts and non-starch polysaccharides (NSP) (Vandeputte and Delcour, 2004; Funami et al., 2005; Kowalski et al., 2008). Gelatinization, pasting and retrogradation properties are important aspects of starch functionality, which are considered as basic processes in the making of starch containing foods. These properties play a key role in food processes including bread baking or sauce thickening. The conditions under which these processes occur affect the quality of the final food products (Rojas et al., 1999; Huang et al., 2007). Generally, when starch suspensions are subjected to high temperature, the granules swell and rupture due to disruption of the amylopectin double helices (hydrogen bonds dissociation), while amylose preferentially leaches out from the swollen granules (Biliaderis, 2009). Starch retrogradation or staling, caused by re-crystallization of the polymer (dispersed amylose and amylopectin) chains, in baked foods occurs when gelatinized starch is cooled down and subsequently stored at low temperature (Jang and Pyun, 1997). Several researchers have reported that the gelatinization parameters and extent of starch retrogradation are influenced by the presence of hydrocolloids or non-starch polysaccharides. NSPs have been added to starch-based food systems to modify or control rheological and textural properties and improve the stability of food products (Rojas et al., 1999; Brennan et al., 2008; Techawipharat et al., 2008; Zhou et al., 2008). Brennan et al. (2006) found that the viscosity of wheat flour pastes increased with addition of fenugreek material. The gel texture of wheat flour incorporated with 3

5 fenugreek had greater hardness, although the gels became softer with higher levels of fenugreek material used. When starch-containing foods such as sauces, soups, ice-creams and desserts, are subjected to repeated freeze-thaw cycles (FTC), their textures and other physicochemical properties may be extensively changed. Low temperature or repeated FTC treatment of concentrated pastes gives rise to cryotropic gel formation, resulting in sponge-like textures in final products (Lozinsky et al., 2000). Repeating the FTC enforces the phase separation and ice growth (Eliasson and Kim, 1992), because the starch gel is syneresised and the water is separated from the gel. Lee et al. (2002) reported the efficacy of hydrocolloids to reduce syneresis. Muadklay and Charoenrein (2008) found that 0.5% xanthan gum was effective in reducing retrogradation of tapioca starch gel. In addition, water separation from starch gel correlated with the setback value as indicated by a rapid visco analyzer (RVA). The setback value was a good indicator for predicting water separation at any given freeze thaw cycles (Pongsawatmanit and Srijunthongsiri, 2008). Malva nut seed (Scaphium scaphigerum) contains a large amount of mucilaginous substance (Yamada et al., 2000). The seeds have been used as a traditional medicine in South-East Asia. Mucilaginous substance from malva nut seed can be extracted from the fruit by soaking it in water following ethanol extraction. Somboonpanyakul et al. (2006) reported that the major carbohydrates in the mucilage are monosacharides arabinose and galactose. The molecular weight of malva nut gum was very high, which was significantly reduced by the purification processing (dialysis and decolouring). FT-IR spectroscopy and methylation analysis showed that malva nut gum had similar structure to gum arabic. Srichamroen and Chavasit (2011) extracted the purified malva nut gum with different concentration of sodium hydroxide to discard the protein content in malva nut gum. Rheological properties of the gel from malva nut gum in different conditions of 4

6 solvent (ph, ionic strength, and co-solutes addition) showed that sodium chloride and calcium chloride had strong effects on swelling of gum. Malva nut gum is also considered as non-starch polysaccharide but this gum is not commonly used in the food industry and has not been shown to affect the nutritional property of foods. Somboonpanyakul et al. (2007) reported that crude malva nut gum (CMG) reduced cooking loss and improved textural properties of frankfurters due to its high water absorption and water holding capacity. Although some applications of malva nut gum in food products have been reported, the information on starch/flour-cmg mixture is limited, especially in starchbased food products. Understanding of the interaction phenomena between the mixtures will be useful for the development of starch-based products with better physical and sensory properties. Therefore, the objective of this research was to investigate the physicochemical properties of CMG and its effect on the pasting behaviour, textural properties and freeze-thaw stability of wheat flour system Materials and methods 2.1 Materials Commercial wheat flour (United Flour Mill Co., Ltd., Thailand), corn oil (Industrial Enterprises Co., Ltd, Thailand) and butter (United Dairy Foods Co., Ltd., Thailand) were used. Malva nut seed was purchased from Chantaburi province, Thailand Crude malva nut gum preparation Crude malva nut gum (CMG) was extracted following the method of Somboonpanyakul et al. (2007). The malva nut seed was soaked in water (1:80 w/v) at 30 o C for 2 hours to completely hydrate and swell the fruit. The excessive water was 5

7 removed by filtering through a 60-mesh silk screen. The crude mucilage was precipitated with 3 volumes of 95% absolute ethanol and dried at 40 o C for 12 hours. Dried CMG was milled using an ultra centrifugal mill (ZM 200, Retsch, Germany) and then sieved through a 80-mesh screen. Yield of dried CMG was about 19.4%. The CMG samples were vacuum packed in laminated foil bags until further analyzed Colour and chemical composition of CMG Colorimetric CIE (L*, a* and b*) measurements of CMG samples were conducted in triplicate using a Minolta Chromameter (CR-410, Konica-Minolta, Japan). CMG samples were estimated for their moisture, ash, fat, fibre and protein contents by the method of AOAC (2000) Water and oil absorption capacities of CMG Water and oil absorption capacities of CMG were determined by the modified method of Mbougueng et al. (2009). One gram (dry basis, db) of the CMG sample was weighed into a pre-weighed centrifuge tube and 20 ml of distilled water or corn oil or butter were added. Corn oil and butter were used to compare the different types of oil. Corn oil represented higher polyunsaturated fatty acid (Kamal and Klein, 2007) and butter represented higher saturated fatty acid (Bobe et al., 2007). The dispersions were stirred occasionally and allowed to stand for 30 min before being centrifuged at 2000g for 25 min. The supernatant was decanted, and sample was reweighed. The water and oil absorption capacities were expressed as grams of water or oil bound per gram of sample on a dry basis. The experiment was done in triplicate

8 Pasting properties of wheat flour-cmg mixture Wheat flour-cmg mixtures were prepared by replacing wheat flour with CMG at concentrations of 0%, 2.5%, 5%, 7.5% and 10% w/w. The ratios of wheat and CMG corresponded to 100:0, 97.5:2.5, 95:5, 92.5:7.5 and 90:10 w/w. Pasting characteristics of wheat flour-cmg mixtures were examined using a Rapid Visco Analyzer (RVA-4D, Newport Scientific Pty. Ltd., Warriewood, Australia). For all measurements, total solid concentrations were 10% suspension in de-ionized water (db, w/v) from different wheat flour-cmg mixtures. The suspension was heated from 50 to 95 C at a uniform rate of 12 C/min with constant stirring at 160 rpm. The sample was held at 95 C for 2.5 min, then cooled to 50 C at a rate of 13 C/min, and held for 2 min. Total cycle time was 13 min using the standard profile (Jangchud et al., 2003). Pasting temperature (PT), peak viscosity (PV), breakdown (BD), hot paste viscosity (HPV), final viscosity (FV) and setback from peak (SB) were recorded. The viscosity values were reported in term of RVA units (RVU). All measurements were performed in triplicate Textural properties of wheat flour-cmg gel Warm pastes obtained from the RVA determination above were used for gel texture analysis following the method of Brennan et al. (2008) with minor modification. The pastes were poured into cylindrical stainless moulds (20 mm inner diameter by 10 mm height). The mixed gels wrapped with plastic film to avoid moisture loss were held at 25 o C for 24 h to equilibrate before measurement. Three batches of each composition were prepared. Texture profile analysis (TPA) tests were performed with a Texture Analyzer (TA-XTplus, Stable Micro Systems, Surrey, UK) fitted with a P35 probe (35 mm probe), which covered the whole surface of the gel sample. The deformation level was 50% of original gel sample height. A crosshead speed was 50 mm/min for avoiding a total 7

9 destruction of the gel structure in the first compression and the values highly correlating with the sensory responses. The textural parameters calculated were hardness (g.force), adhesiveness (g.force), chewiness (g.force), cohesiveness (dimensionless) and springiness (dimensionless). Six samples were measured for each batch Syneresis by freeze thaw cycles Syneresis of wheat flour-cmg gel mixtures was investigated by the modified method of Muadklay and Charoenrein (2008). The gelatinized gel mixtures were prepared using a RVA as described above. Gel samples of 0.5 ml were placed in 2 ml polycarbonate centrifuge tubes with closed screw caps. The tubes were frozen in a freezer chest at -20 o C for 24 h and then thawed in storage chamber at 25 o C for 1 h. The freeze thaw cycle was repeated for up to three cycles with a 3 day interval. Four samples from each condition were centrifuged at 8000g in a refrigerated centrifuge (Universal 320R, Hettich, Germany) for 15 min. The supernatant was decanted and the residue was weighed. The percentage of syneresis was quantified as the ratio of the weight of the supernatant decanted to the total weight of the gel before centrifugation and multiplied by Statistical analysis One-way analysis of variance (ANOVA) of the experimental data was performed to find out if the effect of different concentrations of CMG on quality characteristics of wheat flour mixtures were significant (p<0.05). Duncan s multiple range test (DMRT) was performed for post hoc multiple comparisons

10 Results and discussion 3.1 Physicochemical properties of crude malva nut gum The moisture content of the crude malva nut gum (CMG) was 12.5%. Chemical composition of CMG including protein, fat, ash, fibre and carbohydrate contents are presented in Table 1. Moisture and protein content of CMG are consistent with the results of Srichamroen and Chavasit (2011). Colour of CMG was dark brown. The CIE L*, a* and b* values, and water activity are given in Table 1. Water absorption capacity (WAC) represents the ability of a substance to associate with water under a limited water condition (Singh, 2001). The WAC of CMG was 81.1 g/g dry sample (Table 1). The major chemical components that enhance the WAC of CMG are proteins and carbohydrates since these constituents contain hydrophilic parts, such as polar or charged side chains (Pomeranz, 1985). Oil absorption capacity (OAC) is another important functional property of a hydrocolloid. The CMG absorbed oil for up to 19 g/g dry sample depending on types of oil as shown in Table 1. This may be caused by protein and carbohydrate components, which are composed of both hydrophilic and hydrophobic parts. Non-polar amino acid side chains can form hydrophobic interactions with hydrocarbon chains of lipid and strongly adsorb on to the surface of oil droplets (Elmanan et al., 2008). The major constituent monosaccharides of the CMG were 31.9% arabinose, 29.2% galactose and 29.5% rhamnose. The CMG also contained 6.4% uronic acid and small amounts of glucose, xylose and mannose (Somboonpanyakul et al., 2006). The polysaccharide chains are hydrophilic and extend out into the solution, preventing droplet flocculation and coalescence through electrostatic and stearic repulsion forces (Elmanan et al., 2008). It is suggested that CMG has the potential to reduce fat in bakery products

11 Effect of CMG on pasting behaviour of wheat flour The pasting behaviour measured using a RVA for wheat flour pasted with 0, 2.5, 5, 7.5 and 10% (w/w) of CMG replacement is presented in Fig. 1. The viscosities of pastes were strongly affected by replacing wheat flour with CMG. Results obtained from the pasting profile of wheat flour suggested that below an onset temperature of gelatinization (usually below 50 o C), starch granules are insoluble in water. Thus, the viscosity of an aqueous dispersion remains low. When starch granules are heated above the gelatinization temperature in the presence of water, the granules absorb a large amount of water and swell, resulting in high viscosity. The gelatinization of starch involves random entanglements of starch molecules and the interaction of starch with water (Wang et al., 2008). The temperature at the onset of this rise in viscosity can be considered as the starting point of gelatinization and is defined as the pasting temperature (PT), according to the RVA test. The PT of wheat flour was about 85.5 o C. Ragaee and Abdel-Aal (2006) also found that the PT of wheat flour varied from o C depending on the types of flour and flour mixture. The PT of wheat flour significantly decreased (p<0.05) with all levels (2.5-10%) of CMG ( o C) as shown in Table 2. A reduction of PT by about 3 o C of PT was previously reported when 1% alginate was added to wheat flour implying an earlier beginning of starch gelatinization (Rojas et al., 1999). Peak viscosity (PV) is related to the degree of swelling of granule during heating, as starch with higher swelling capacity causes the higher PV (Ragaee and Abdel-Aal, 2006). The PV represents the equilibrium point between swelling and the rupture of starch granules. Replacement of wheat flour with all levels of CMG resulted in a significant increase (p<0.05) in the PV (Table 2). The increase in viscosity with temperature is probably due to the removal of water from the CMG. The PV of wheat flour with 10% CMG increased by about 5.2 times when compared with non-cmg 10

12 sample (0% CMG replacement). An increase in peak viscosity of starch paste in the presence of a hydrocolloid has been previously reported (Liu et al., 2003; Huang et al., 2010). The viscosity of starch pastes increased with increasing molecular weight of hydrocolloids, causing water deficiency in the granule environment (Sikora et al., 2008). The increase in peak viscosity could be accounted by a thickening gum that enhances the forces being exerted on the starch granules in the shear field. Yoshimura et al. (1996) indicated that addition of hydrocolloids increased the paste concentration by immobilizing water molecules. The hydrocolloids could also form a strong entanglement with the amylose released from starch granules (Liu et al., 2003). Chaudemanche and Budtova (2008) reported that the addition of polysaccharide gums such as xanthan gum to starch pastes increased the viscosity and elasticity and restricted retrogradation and syneresis of starch based systems. Pongsawatmanit and Srijunthongsiri (2008) also found that peak viscosities of tapioca starch pastes increased with increasing xanthan gum concentration. Furthermore, protein and fibre present in CMG could affect pasting viscosity and properties of starch (Jangchud et al., 2003). The PV was lower by the presence of the protein and fibre in starch mixtures, which could inhibit swelling of starch granules. Swelling of granules accompanied by leaching of amylose increases the viscosity while granules may rupture during further shearing which results in a decrease in viscosity. The hot paste viscosity (HPV) of the wheat flour was about 77.3 RVU that increased significantly (p<0.05) with an increase in replacement by all levels of CMG. Leached amylose is more or less aligned in the direction of flow that contributes to the breakdown (BD). BD is correlated with the stability of starch granule under high shear condition (Ragaee and Abdel-Aal, 2006). It is shown that increasing CMG levels gave greater BD. Replacement with 10% CMG had the highest BD value (306.3 RVU). As the 11

13 mixture cools, there is a decrease in kinetic energy, which allows the starch molecules to re-associate and form network. This short-term re-association results in textural changes of cooked paste. Longer storage induces reversible re-crystallization of amylopectin, which increases the rigidity of the swollen granules embedded in the continuous amylose network (Miles et al., 1985). When the sample is subsequently cooled down to 50 o C, the starch reaches a final viscosity (FV), which is attributed to the retrogradation or re-association of amylose molecules as can be considered from setback (SB) (Ragaee and Abdel-Aal, 2006). Due to high viscosity of wheat flour-cmg mixture, the SB from peak (calculated from FV-PV) seems to be more useful than SB from HPV (calculated from FV-HPV) for indicating starch retrogradation. Reduction in SB from peak with increasing CMG levels was observed. The SB from peak values of the pastes at 0 and 2.5% concentration were not significantly different from each other (p 0.05) but were significantly greater (p<0.05) than that of the pastes at 5, 7.5 and 10% (Table 2). The setback values were used to indicate the extent of short-term retrogradation (Pongsawatmanit and Srijunthongsiri, 2008). Therefore, the inclusion of CMG in wheat flour at higher levels (5-10%) could reduce the rate of starch retrogradation Effect of CMG on gel textural properties of wheat flour RVA gels stored for 24 hours underwent aging. Replacement of wheat flour by CMG gave significant difference (p<0.05) in several textural parameters, including hardness, springiness, cohesiveness, gumminess and chewiness but had no significant effect (p 0.05) on adhesiveness as presented in Table 3. Replacement of wheat flour by CMG significantly reduced (p<0.05) the hardness, springiness, gumminess and chewiness of gel, resulting in more viscous gels. However, there was no difference between 0 and 12

14 % CMG replacement. Brennan et al. (2008) also found that the addition of hydrocolloids such as gum arabic to wheat flour lowered hardness. The hardness of gel decreased with increasing replacement levels of gum arabic. However, guar gum and locust bean gum gave opposite effect on hardness. They increased the hardness of gels at lower level (2.5%) of gums but decreased at 5% level. It is suggested that high concentration of CMG could be used when soft gel texture is desired. Adhesiveness depends on a combined effect of adhesive and cohesive forces. It is an important attribute that could have either positive or negative ramifications depending on the applications (Meiron and Saguy 2007). Although the CMG provided high viscosity of paste, the adhesiveness of the gel with increased CMG concentration was not different (Table 3). Huang et al. (2007) found that addition of konjac-glucomannan to rice starch did not change adhesiveness of the mixed gel. Springiness indicates the elasticity of the food sample. If the sample returns to its original height, the elasticity will be 100% (Hoseney and Smewing, 1999). Springiness is high when the gel structure is broken into a few large pieces during the first TPA compression, whereas low springiness results from the gel breaking into many small pieces. Less springy gels break down more easily during mastication than a firm and spring gel (Marshall and Vaisey, 1972). The 10% replacement of CMG reduced the springiness of wheat gel by about 4.5% when compared to non-cmg gel sample. Effect of different concentrations of CMG on springiness of wheat flour CMG gel is presented in Table 3. Cohesiveness is more of an internal property, involving a combined effect of adhesive and cohesive forces, as well as viscosity and elasticity. It indicates how well the product withstands a second deformation relative to how it behaved under the first deformation (Adhikari et al., 2001). In relation to sensory evaluation, it is suggested that the product will be perceived as tough and difficult to break up in the mouth 13

15 (Hoseney and Smewing, 1999). Replacement of wheat flour with 10% CMG had the highest cohesiveness (0.66) of gel as reported in Table 3. Higher values of cohesiveness indicate a very cohesive starch gel, leading to tougher texture. Chewiness is the quantity to simulate the energy required for masticating a semisolid sample to a steady state of swallowing. Chewiness and gumminess values were parallel in their variations with hardness value due to the high relative weight of hardness in the calculation of chewiness (Table 3). The chewiness and gumminess of wheat flour- CMG gels showed the similar trend as springiness. These values significantly decreased (p<0.05) with higher CMG levels (5-10%). The textural properties of the wheat flour- CMG mixed gels were dependent on the concentration of CMG. This is consistent with the results of Huang et al. (2007) who reported that lower than 0.2% of carrageenan and more than 0.3% of gellan could increase the hardness and adhesiveness of rice starch gels. It is suggested that non-suitable polysaccharides or inappropriate concentration would change gel quality Effect of CMG on freeze-thaw stability of gel Syneresis or loss of water is an important parameter critical to the stability of a gel system. No syneresis indicates good water-holding capacity of the gel (Hoover et al., 1997). When a starch gel is frozen, starch-rich regions are created in the matrix, where water remains partially unfrozen. High solid concentration in the regions facilitates the starch chains to associate forming thick filaments, whereas water molecules coagulate into ice crystals forming a separated phase. These effects contribute to spongy structure and released liquid or syneresis (Lee et al., 2002). In our work, the freezing and thawing was performed for up to 3 cycles. The syneresis from the gelatinized wheat flour pastes increased with increasing numbers of FTC (Fig. 2). Higher water separation on thawing 14

16 indicates the retrograded starch network or structure was easily disrupted by ice crystal formation (Pongsawatmanit and Srijunthongsri, 2008). Average syneresis of non-cmg gel sample was about 16.4% after the first FTC. After second and third FTC, syneresis of gel increased to 23.5% and 27.5%, respectively, as shown in Fig. 2. Lower syneresis is probably due to high intracellular and intermolecular hydrogen bonding. Ability of the gel to hold moisture or gel gelation in aqueous gum solution is dependent on the conformation and composition of biopolymer systems. Water availability in the gelation of gums and starch granules depends on the ability of particular gums to hold water molecules and the conformational changes and inhibition of gelation, resulting in reduced syneresis (Lo et al., 2003; Baranowska et al., 2008). When compared to non-cmg sample, a decrease in the syneresis of gel by about 49.1% after the first FTC was observed in the sample with 2.5% CMG replacement. No syneresis was detected in gel samples with 5%, 7.5% and 10% of CMG replacement after the first FTC, indicating strong and stable water-holding capacity in gel systems. Higher concentration of CMG reduced the syneresis of wheat gels. The rates of syneresis after 3 FTC increased slightly with 10% CMG replacement (slope = 0.75) whereas relatively large increase in the value (slope = 5.58) was observed for non-cmg sample. The slopes obtained from each linear curve decreased with increasing CMG concentration, confirming that hydrogen bonding between water and CMG polymer was pronounced. The linear regression analysis for predicting % syneresis at different concentrations of CMG is also presented in Fig. 2. This pattern is consistent with the results of Muadklay and Charoenrein (2008) who reported that improvement of freeze-thaw stability was observed when hydrocolloids were added. The addition of 0.5% xanthan gum stabilized the tapioca starch gel with no syneresis until the third cycle. In addition, the retarding of hydrocolloids starch gel retrogradation is depended on different polymers phase 15

17 separation in-system or interaction between hydrocolloids and amylose molecules (Shi and BeMiller, 2002). Similarly, the systems of hydrogel complex containing curdlan gum were different in gel texture stability (Williams et al, 2009) with the most stable gel strength achieved by curdlan combined with guar or xanthan at 2% (w/v) total concentrations. These systems provided texture stabilization over multiple freeze-thaw cycles and enhanced the product quality Conclusions Crude malva nut gum (CMG) is a novel source of gum. The replacement of wheat flour by graded amount of CMG altered the pasting behaviour, textural properties and freeze-thaw stability of wheat pastes and gels. The inclusion of CMG in flour significantly increased the pasting properties of flour mixes and thereby altered the textural properties of mixed gels. For freeze thaw stability, higher level of CMG in wheat gel mixtures could decrease syneresis. It is revealed that higher viscosity, softer texture and lower syneresis of gels could be attained using CMG. Therefore, CMG could be considered as a thickening agent in starch-based products in order to retard staling and improve gel stability Acknowledgement We gratefully acknowledge the financial support of the Thailand Research Fund (TRF) and the Commission of Higher Education (CHE) under funding number MRG References Adhikari, B., Howes, T., Bhandari, B. R., & Truong, V. (2001). Stickiness in foods: 16

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23 501 Caption of Figures Fig. 1. Pasting behaviour of wheat flour replaced by different levels of CMG Fig. 2. Syneresis of wheat flour gels replaced by different levels of CMG for up to 3 freeze-thaw cycles. 22

24 Fig. 1 Pasting behaviour of wheat flour replaced by different levels of CMG (Authors: Y. Phimolsiripol, U. Siripatrawan and C.J.K. Henry)

25 % 2.5% 5% 7.5% 10% y = x R 2 = y = x R 2 = 0.75 % Syneresis y = x R 2 = y = x R 2 = y = 0.75x R 2 = Number of freeze-thaw cycles Fig. 2 Syneresis of wheat flour gels replaced by different levels of CMG for up to 3 freeze-thaw cycles (Authors: Y. Phimolsiripol, U. Siripatrawan and C.J.K. Henry) 24

26 521 Table 1 Physicochemical properties of crude malva nut gum 522 Properties Values Chemical Composition Moisture (% wb) Protein (% wb) 6.72 Fat (% wb) 0.36 Fiber (% wb) 3.83 Ash (% wb) 4.99 Carbohydrate (% wb) Color CIE L* a* 6.60 b* Water activity Oil absorption (g/g dry sample) Butter Corn oil 4.60 Water absorption (g/g dry sample) (Authors: Y. Phimolsiripol, U. Siripatrawan and C.J.K. Henry)

27 Table 2 Pasting profile of wheat flour pasted with different levels of CMG determined by RVA. 530 RVA parameters CMG concentration (% w/w) PT ( o C) a b b b b PV (RVU) e d c b a HPV (RVU) d d c b a BD * (RVU) d c b b a FV (RVU) e d c b a SB ** (RVU) a a b c d Values are the mean and standard deviation of three samples. Mean values with different letters in the same row are significantly different (p<0.05). *, ** calculated from (PV HPV) and from (FV PV), respectively (Authors: Y. Phimolsiripol, U. Siripatrawan and C.J.K. Henry)

28 537 Table 3 Textural properties of wheat flour gel with different levels of CMG. 538 Textural parameters Hardness CMG concentration (% w/w) a a b bc c (g.force) Adhesiveness a a a a a (g.sec) Springiness a a b b b Cohesiveness c b b b a Gumminess a a b b b (g.force) Chewiness a a b b b (g.force) Values are the mean and standard deviation of three samples. Mean values with different letters in the same row are significantly different (p<0.05). ns indicates no significantly different (p 0.05) (Authors: Y. Phimolsiripol, U. Siripatrawan and C.J.K. Henry) 27