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Pasting properties of different wheat flour-hydrocolloid systems
Food Hydrocolloids 13 (1999) 27±33
Pasting properties of dierent wheat ¯our-hydrocolloid systems J.A. Rojas, C.M. Rosell, C. Benedito de Barber * Instituto de AgroquõÂmica y TecnologõÂa de Alimentos (CSIC), PO Box 73, 46100-Burjassot, Valencia, Spain Received 18 March 1998; accepted 25 June 1998
Abstract The eect of several hydrocolloids on the pasting properties and gelling behaviour of wheat ¯our was investigated. The in¯uence of the selected hydrocolloids (guar gum, pectin, alginate, k-carrageenan, xanthan and hydroxypropylmethylcellulose (HPMC)) on wheat ¯our was tested by using two dierent techniques: amylograph and dierential scanning calorimetry (DSC). In order to have a general overview of their eect, hydrocolloids were chosen from dierent sources implying a broad diversity of chemical structures. Dierences among hydrocolloid-wheat ¯our suspensions were more evident from amylographic analysis than from DSC examination. The hydrocolloid addition largely modi®ed the amylograph parameters of wheat ¯ourÐeven at the low levels tested [0.5 and 1% (w/w), ¯our basis], and the extent of their eect depended upon the chemical structure of the added hydrocolloid. The greatest eect on pasting temperature was observed when 1% alginate was added, which produced a decrease of ca 3 C. This reduction is really important since it implies an earlier beginning of starch gelatinization and, in turn, an increase in the availability of starch as enzyme substrate during baking period. Xanthan and pectin increased the cooking stability while k-carrageenan and alginate did not modify it. Setback was augmented by guar gum and HPMC but alginate, xanthan and k-carrageenan showed the opposite eect. The bump area related to the formation of amylose±lipid complex, was favoured by k-carrageenan, alginate and pectin, and slightly aected by xanthan and HPMC. In summary, each tested hydrocolloid aected in a dierent way the pasting properties of wheat ¯our. The results obtained are important for the appropriate use of these hydrocolloids as ingredients in the bread making process. # 1998 Elsevier Science Ltd. All rights reserved.
1. Introduction Wheat ¯our and particularly wheat starch is widely used in food industries. Gelatinization and gelation of starch are considered basic processes in the making of starch containing foods. Starch gelatinization and gelation involve consecutive changes which play a key role in processes such as bread baking, sauce thickening, gelling of pie ®llings, etc. The conditions in which the phenomena comprised in these processes occur, determine the quality of the ®nal food products. In the scienti®c literature dierent additives and ingredients have been used to modify the gelatinization± gelation processes, namely the pasting properties of starch. Sugars were added to starch mixtures in order to increase the gelatinization temperature and the paste viscosity by decreasing the availability of water (Evans & Haisman, 1982; Spies & Hoseney, 1982). Ganz (1965) described the eect of salt addition resulting in an improvement of the integrity of the starch granule and * Corresponding author. Tel.: +34-6-390-0022; fax: +34-6-3636301; e-mail: [email protected]
an increase of the paste consistency. Salts were also added to retard the retrogradation of the starch (Chang & Liu, 1991). Other compounds that have been extensively studied include dierent surfactants and emulsi®ers, which promote a reduction of the starch swelling and the paste consistency (Roach & Hoseney, 1995; Stamp¯i & Nerste, 1995). However, the principal eect produced by the emulsi®ers is to inhibit the retrogradation of amylose by forming complexes with the amylose chains (Ghiasi, Hoseney, & Varriano-Marston, 1982). Other compounds usually added to starch containing products are gums or hydrocolloids due to their desirable eect on the acceptability of foodstus. Hydrocolloids or gums have been widely used in food technology as additives in order to: (i) improve food texture (Armero & Collar, 1996a, 1996b), (ii) slow down the retrogradation of the starch (Davidou, Le Meste, Debever, & Bekaert, 1996), (iii) increase moisture retention, (iv) extend the overall quality of the product during time, and also (v) as gluten-substitutes in the formulation of gluten-free breads since gums could act as polymeric substances that mimic the viscoelastic properties of gluten in bread doughs
0268-005X/98/$Ðsee front matter # 1998 Elsevier Science Ltd. All rights reserved PII: S0268-005X(98)00066-6
28
J.A. Rojas et al./Food Hydrocolloids 13 (1999) 27±33
(Smith, 1971; Toufeili, Dagher, Shadarevian, Noureddine, Sarakbi, & Farran, 1994). Among the hydrocolloids tested are guar gum, locust bean gum or xanthan gum but the majority of those studies were focused on clarify the exact mechanism of interactions between the hydroxyl groups from the hydrocolloid and the starch components (Alloncle & Doublier, 1991), and those analysis have been performed by using high concentrations of hydrocolloids. The aim of this research is to determine the eect of hydrocolloids addition at the levels commonly employed in food product formulations, on the pasting properties and gelling behaviour of wheat ¯our. In order to have a general overview of their eect, hydrocolloids were chosen from dierent sources (vegetal and microbial) implying a broad diversity of chemical structures. The in¯uence of the selected hydrocolloids (guar gum, pectin, alginate, k-carrageenan, xanthan and hydroxypropylmethylcellulose) on wheat ¯our were tested by using two dierent techniques: viscograph and dierential scanning calorimetry (DSC). Brabender viscograph is an equipment extensively used to describe the rheological behaviour of wheat ¯our during its progressive cooking and cooling, and DSC is an useful tool which detects the heat ¯ow associated to the order-disorder transitions in starch, giving a quantitative measurement of gelatinization (Stevens & Elton, 1971). In this study both techniques have been used to characterise the modi®cations that starch gelatinization and gelation undergone by the addition of dierent hydrocolloids. 2. Materials and methods 2.1. Materials A commercial wheat ¯our from a local market was used for this study. Hydrocolloids were generously donated by several companies. The hydrocolloids tested included guar gum (Guardan127 from Grindsted), a low methoxylated pectin (Cesapectin LM/35 from Cesap S.p.a., Bergamo, Italy), sodium alginate (Satialgine S1100 from Bio-Industries, S.A.), a k-carrageenan (Genugel type UPC from The Copenhagen Pectin Factory Ltd.), xanthan gum food grade (xanthan from Jungbunzlauer) and hydroxypropylmethylcellulose (HPMC) (Methocel K4M from Dow Chemical, USA ).
to wheat starch suspension, as indicated elsewhere. The amylographic procedure was in accordance with ICC Method 126/1 (1992), using a heating-cooling cycle. Brie¯y, the suspension (with the pH previously adjusted to 5.5) was heated from 30 to 95 C increasing the temperature at 1.5 C/min, then it was held at 95 C for 20 min, afterwards the paste was cooled to 50 C and ®nally was kept at 50 C for 20 min. Fig. 1 shows the cycle previously described and the shape of the amylogram describing their characteristics. They included pasting temperature, maximum viscosity, viscosity of the paste on attaining 95 C, viscosity after the ®rst holding period, viscosity of the cooked paste after cooling to 50 C and ®nal viscosity at the end of the second holding period (Marzurs, Schoch, & Kite, 1957). The following parameters were de®ned: hot or cooking stability (expressed as the inverse of the dierence between viscosity at 95 C after the ®rst holding period and that at the beginning of this period), stability at 50 C or cooling stability (expressed as the inverse of the dierence between the end viscosity and the initial one of the second holding period), setback (the dierence between the viscosity at 50 C and the viscosity after the ®rst holding period) (Olkku & Rha, 1978). The bump area was measured by connecting the baseline of the bump from the starting point to the ending point of the bump peak (Xu, Chung, & Ponte, 1992). Two replicates were carried out in all cases. 2.3. Dierential scanning calorimetry Starch gelatinization was analysed by dierential scanning calorimetry (DSC). Experiments were carried out on a Perking±Elmer DSC-7. Samples of 20±30 mg taken from the ¯our-hydrocolloid suspensions prepared for the viscograph were hold in stainless steel capsules (PE 0319-0218) and heated from 30C to 95 C at 10 C/ min. An empty capsule was used as a reference. The starch gelatinization parameters in the DSC thermogram
2.2. Determination of the amylogram parameters The pasting properties of wheat ¯our were investigated with a Brabender Viscograph A/RH. When the addition of hydrocolloids were studied two dierent concentrations of each hydrocolloid [0.5 and 1.% (w/w) in a ¯our basis] were added to wheat ¯our suspension or
Fig. 1. A typical amylogram with a heating-cooling cycle. Some amylogram characteristics are included in the graph.
J.A. Rojas et al./Food Hydrocolloids 13 (1999) 27±33
29
All the hydrocolloids added to the wheat ¯our promoted a modi®cation of the pasting properties at the two levels tested. Each hydrocolloid aected in a particular way the amylograph parameters of the wheat ¯our, as can be seen in Table 1. This was expected because of the evident dierences in their chemical structures.
lower than the control at both tested concentrations. The decrease in pasting temperature caused by xanthan, k-carrageenan and alginate seems to be due to some kind of interaction between wheat starch and the hydroxyl groups of the hydrocolloids as pointed out Christianson, Hodge, Osborne, & Detroy (1981). In fact, the results obtained in some experiments carried out with wheat starch instead of wheat ¯our suspensions con®rm this supposition. In those analyses the decrease in the pasting temperature of starch promoted by alginate addition was even higher than the one observed in ¯our suspensions (3.3 C in starch versus 2.4 C in ¯our). This is very important because it may imply an earlier beginning of the gelatinization process, which would be traduced in a greater availability of starch as enzyme substrate during the baking period.
3.1. Eect of the hydrocolloid addition on the pasting temperature
3.2. Viscosity of the wheat ¯our-hydrocolloid suspensions
HPMC slightly increased the pasting temperature at both concentrations added. The same result was obtained with the addition of pectin although at 0.5% level only a slight increase was observed. The eect of the guar gum on the pasting temperature was dependant upon its concentration, an increase was produced by adding guar gum at 0.5% but the opposite eect was obtained at 1%. A decrease of the pasting temperature was observed when the very eective gelifying agents (k-carrageenan, alginate, and xanthan) were included. Xanthan caused a decrease at both concentrations, being more pronounced when adding 1% of this gum. k-Carrageenan promoted also a decrease at both concentrations being of almost 2 C at 1%. The highest modi®cation was observed with the addition of alginate, in this case the pasting temperature was 2.5 C
Regarding the maximum viscosity, it was reached in the range of 84±85 C. All the hydrocolloids aected the maximum viscosity of the wheat ¯our suspension (Table 1). Pectin and HPMC decreased the maximum viscosity and this reduction augmented with the hydrocolloid concentration. The rest of the hydrocolloids incremented the maximum viscosity. Again, the greatest eect was observed with alginate, followed by k-carrageenan and xanthan. Guar gum also increased the maximum viscosity but only when employed at the 1% level. The same trend of the maximum viscosity was observed when the hydrocolloids were added to wheat starch suspensions. The increments promoted on this parameter by the addition of alginate or k-carrageenan to starch were more pronounced than the previous, observed with ¯our. The maximum viscosity reached by starch increased from 320 to 370 BU when adding 0.5% (w/w) k-carrageenan and reached up to 540 BU in the case of alginate. From the above results it seems that the changes in maximum viscosity of the wheat ¯our paste due to the presence of hydrocolloids are caused mostly by the existence of interactions between the hydrocolloid and the starch granules. Maximum viscosity re¯ects the ability of the starch granules to swell freely before their physical breakdown. Starch with a high swelling power also yields a high maximum viscosity (Tipples, D'Appolonia, Dirks, Hert, Kite, Matsuo, Patton, Ranum, Shuey, & Webb, 1980). Therefore, from the above results it seems that the presence of alginate, k-carrageenan or xanthan promote an increment of the capacity of the starch granules to swell. Increments of the maximum viscosity has been previously observed with the addition of xanthan (Evans & Haisman, 1982; Christianson et al., 1981), i-carrageenan (Tye, 1988), and galactomannans like guar gum (Christianson et al., 1981; Alloncle, Lefebvre, Llamas, &
are the onset temperature (To), the conclusion temperature (Tc), the peak temperature or maximum temperature (Tp), and the gelatinization temperature range (the dierence between Tc and To). The amount of energy necessary for gelatinization (enthalpy) was automatically registered. 3. Results and discussion
Table 1 The eect of the hydrocolloid addition on the pasting properties of wheat ¯our. The experimental conditions are described in Section 2. Hydrocolloid
None Guar gum Pectin Alginate k-Carrageenan Xanthan HPMC
Maximum Viscosity at Concentration Pasting 95 C (%) temperature viscosity (BU) (BU) ( C) 0.5 1.0 0.5 1.0 0.5 1.0 0.5 1.0 0.5 1.0 0.5 1.0
66.8 67.5 66.0 66.9 67.6 64.4 64.3 66.4 65.0 66.4 66.0 67.3 67.4
646 650 720 600 560 728 790 670 700 678 660 645 620
408 390 380 380 335 495 540 385 380 480 445 430 420
30
J.A. Rojas et al./Food Hydrocolloids 13 (1999) 27±33
Doublier, 1989). Christianson (1982) assumed that the eect of hydrocolloids on maximum viscosity was a result from at least two phenomena, ®rst their interaction with solubilised starch and amylose, and second, this interaction cause an increase of the forces exerted onto the granules, as a consequence, the granule breakdown and the amount of solubilised starch is aected. Alloncle et al. (1989), viewing starch pastes as suspensions of swollen granules dispersed in a continuous macromolecular medium, stated that the hydrocolloid is present only in the continuous phase of the medium and as longer the starch granules swell the concentration of the hydrocolloid within the continuous phase increases leading to a substantial increase in viscosity of this phase. Alloncle and Doublier (1991) indicated that the modi®cations which result from the addition of hydrocolloids to a starch system are complex, and these can be ascribed to phase separation processes in relation to incompatibility phenomena between unlike polymers. Synergistic interactions between starch and hydrocolloids were previously observed by Bahnassey and Breene (1994), and these were dependent on the hydrocolloid structure so structural and rheological properties of the hydrocolloid are very relevant. In opposition, Appelqvist and Debet (1997) did not observe this synergistic eect. The addition of hydrocolloids also aected the viscosity attained at 95 C. The greatest increase was produced by alginate followed by xanthan and HPMC, although only in the case of alginate this increment augmented with the gum concentration. The other hydrocolloids had no eect on the viscosity at 95 C. The dierence of viscosity at 95 C and maximum viscosity has been related to the easiness of cooking the starch by several authors (Olkku & Rha, 1978; Tipples et al., 1980; Moros, 1997). The wheat ¯our paste exhibited a high viscosity drop when k-carrageenan or guar gum were included. This means that the interaction between these hydrocolloids and the ¯our aected the swollen granules making them more fragile and therefore, their addition favours the cooking. In opposition, greater stability than the control was observed when xanthan or HPMC were added to the ¯our, and in consequence longer cooking time should be necessary. Christianson et al. (1981) observed dierent behaviour of starch/xanthan and starch/guar gum mixtures in the viscosity drop after reaching the maximum. Nevertheless the analysis performed with starch suspension did not show any viscosity drop when adding hydrocolloid, the viscosities at 95 C were identical as the maximal viscosities. These results suggest that the interaction hydrocolloid±starch explains the viscosity decline observed with hydrocolloid-¯our mixtures. Moreover, they suggest the implication of the other ¯our components (lipids, proteins, carbohydrates nonstarch,..) in the viscosity decrease.
3.3. Eect of the hydrocolloid addition on the paste stability of wheat ¯our The next stage in the amylogram is the ®rst holding period, in which the temperature was kept at 95 C for 20 min. This period simulates the cooking time and only small changes in viscosity are produced. The parameter that de®nes this phase is the cooking or hot stability, thus high value means high stability of the already broken starch granules at the cooking temperature. The addition of some hydrocolloids modi®ed the cooking stability (Fig. 2). Guar gum and HPMC increased slightly this parameter, while the greatest stabilisation was promoted by pectin and xanthan (17 and 27-fold, respectively). The parameter used to de®ne the second holding period was the cooling stability and it indicates the paste behaviour in a form usually adopted for practical purposes. The cooling stability was slightly modi®ed by the hydrocolloids (Fig. 3), regardless of alginate which increase the stability by 4.7-fold respect to the control. 3.4. In¯uence of the hydrocolloids on the setback and the formation of the amylose-lipid complex The presence of 0.5% hydrocolloid concentration on a wheat ¯our suspension also produced modi®cations of the setback and the bump area. Regarding the setback, pectin did not modify it, guar gum and HPMC caused
Fig. 2. Eect of the hydrocolloid addition on the cooking or hot stability of the paste. This parameter is de®ned in Section 2. The hydrocolloid concentration in these analysis was 0.5% (w/w) (¯our basis).
J.A. Rojas et al./Food Hydrocolloids 13 (1999) 27±33
an increase, while alginate, k-carrageenan and xanthan provoked a decrease of this parameter (Fig. 4). During the cooling stage the amylose chains diused outside the starch granules during cooking, retrograde. This phenomenon is responsible of the ®rming of bread crumb
Fig. 3. Cooling stability of dierent hydrocolloid-wheat ¯our pastes. Cooling stability is de®ned in Section 2. The hydrocolloid concentration was 0.5% (w/w) (¯our basis).
Fig. 4. Eect of the hydrocolloid addition on the setback or starch retrogradation. Hydrocolloid concentrations were 0.5% (w/w) ¯our basis.
31
during the ®rst hours after baking. Thus, it is convenient to have the addition of additives and/or ingredients that promote a reduction of the setback, and in consequence, a delay of the ®rming crumb. Therefore, the addition of alginate, k-carrageenan or xanthan to wheat ¯our could be considered useful antistaling additives in the bread making process. A commonly known as bump area appears in the amylograms during the cooling stage. Measured values for the bump areas are shown in Fig. 5 for samples at 0.5% hydrocolloid level. Addition of guar gum, xanthan or HPMC did not change signi®cantly the size of the bump area while samples with the rest of hydrocolloids presented larger areas. The largest bump area was present with k-carrageenan. The bump area has been related with the extent of the formation of amylose-lipid complex during the cooling phase (Xu, Ponte, & Chung, 1992), in fact, when the study was done only with starch no eect was observed in the bump area (results not shown), due to the absence of the lipid fraction. High bump areas are associated to high concentration of amylose-lipid complex, and it is connected to a softened eect of the bread crumb (Xu, Chung et al., 1992). Hence, k-carrageenan added to wheat ¯our dough will produced the softest bread crumb; this eect together with the retardation of the setback convert this hydrocolloid in the best candidate as antistaling additive in bread formulation.
Fig. 5. Eect of the addition of hydrocolloid to the wheat ¯our paste on the bump area. The hydrocolloid concentration was 0.5% (w/w) (¯our basis).
32
J.A. Rojas et al./Food Hydrocolloids 13 (1999) 27±33
Table 2 The eect of the hydrocolloid addition on DSC parameters of wheat ¯our. Hydrocolloid concentration in the mixtures was 1% (w/w) ¯our basis. The procedure is described in Section 2. Hydrocolloid
To ( C)
Tp ( C)
Tc ( C)
Range ( C)
Enthalpy (J/g d.b.)
None Guar gum Pectin Alginate k-Carrageenan Xanthan HPMC
54.7 55.6 57.4 56.1 56.3 56.8 57.7
63.5 63.4 64.3 62.8 63.4 63.7 63.9
74.9 76.0 73.3 73.2 75.9 74.5 72.4
20.2 20.4 15.9 17.1 19.6 17.7 14.7
10.4 7.9 7.7 7.7 8.2 9.0 7.7
3.5. Eect of the hydrocolloid addition on the DSC parameters Despite the evident dierences observed on starch pasting properties when adding dierent hydrocolloids, no signi®cant dierences were detected by using dierential scanning calorimetry, as was previously reported by Biliaderis, Arvanitoyannis, Izydorcik, and Prokopowich (1997). DSC parameters are shown in Table 2. The interactions between starch and hydrocolloid promoted a delay of the starch gelatinization (a slight increase of the onset temperature (To). The peak temperature (Tp) of the hydrocolloid±¯our mixtures was similar to that of the control except for the alginate±¯our sample at 1% hydrocolloid level which was slightly lower. The hydrocolloids may interact with the starch to produce an increase or decrease of the temperature gelatinization ranges (Tc±To), depending on the hydrocolloids. The greatest eect on the transition ranges was observed with HPMC and pectin; in addition these two hydrocolloids besides to alginate gave the lowest values of enthalpy. The overall eect of hydrocolloids was a decrease in the enthalpy of gelatinization in the range of 1±2.7 J/g ¯our d.b. No correlation was observed between the DSC parameters and those obtained with the amylograph. 4. Conclusions The addition of dierent hydrocolloids to wheat ¯our promotes a great eect on the pasting properties of the resulting hydrocolloid-¯our mixture and the extent of this variation is highly dependent of the chemical structure of the hydrocolloid added. Modi®cations on the gelatinization and gelation processes of wheat ¯our by the addition of hydrocolloids are detected by the amylograph even at the low concentrations employed [0.5% (w/w) ¯our basis]. In general, the highest eect on pasting properties of wheat ¯our was promoted by alginate, k-carrageenan or xanthan. These hydrocolloids decrease
the pasting temperature, increase the maximum viscosity, decrease the tendency to retrograde and increase the size of the bump area. Regarding the in¯uence on the paste stability during the holding periods, it is useful to remark the increase on the cooking stability produced by pectin and mainly by xanthan; and the large increment on the cooling stability promoted by alginate. The analysis performed with starch suspensions revealed that these results could be attributed to the hydrocolloid-starch interactions during the heating stage while to explain the further behaviour the rest of the ¯our components have to be considered. The interaction between hydrocolloids and starch produces a slight modi®cation of the DSC parameters, being the most aected parameter the gelatinization temperature ranges, which are decreased. Finally, the above results indicate that the selection of the right hydrocolloid depends on the speci®c paste property to be modi®ed. For instance when looking for the reduction of the staling, k-carrageenan is the best additive due to both its softening and retarding the ®rming of the bread crumb eects. Acknowledgements The authors gratefully acknowledge the ®nancial support of the ComisioÂn Interministerial de Ciencia y Tecnologia (CICYT) and Consejo Superior de Investigaciones Cienti®cas (CSIC). J.A.R would like to thank the predoctoral grant from Consejo Nacional de Ciencia y Tecnologia (Mexico). References Alloncle, M., & Doublier, J. L. (1991). Food Hydrocolloids, 5, 455± 467. Alloncle, M., Lefebvre, J., Llamas, G., & Doublier, J. L. (1989). Cereal Chemistry, 66, 90±93. Appelqvist,I. A. & Debet, M. R. (1997) Food Rev. Int, 13, 163±224. Armero, E., & Collar, C. (1996a). Food Sci. and Technol. Int., 2, 323± 333. Armero, E., & Collar, C. (1996b). Journal of Food Science, 61, 299± 303. Bahnassey, Y. A., & Breene, W. M. (1994). Starch, 46, 134±141. Biliaderis, C. G., Arvanitoyannis, I., Izydorcik, M. S., & Prokopowich, D. J. (1997). Starch, 49, 278±283. Chang, S., & Liu, L. (1991). Journal of Food Science, 56, 564±570. Christianson, D. D. (1982). In D. R. Lineback, & G. E. Inglett (Eds.), Food carbohydrates (pp. 399±419). IFT Basic symposium series. Wesport, Connecticut: AVI Publishing Company Inc. Christianson, D. D., Hodge, J. E., Osborne, D., & Detroy, R. W. (1981). Cereal Chemistry, 58, 513±517. Davidou, S., Le Meste, M., Debever, E., & Bekaert, D. (1996). Food Hydrocolloids, 10, 375±383. Evans, I. D., & Haisman, D. R. (1982). Starch, 34, 224±231. Ganz, A. J. (1965). Cereal Chemistry, 42, 429±431. Ghiasi, K., Hoseney, R. C., & Varriano-Marston, E. (1982). Cereal Chemistry, 60, 58±61.
J.A. Rojas et al./Food Hydrocolloids 13 (1999) 27±33 Marzurs, E. G., Schoch, T. J., & Kite, F. E. (1957). Cereal Chemistry, 34, 141±145. Moros, M. C. (1997). Molineria y Panaderia, 1053, 48±53. Olkku, J., & Rha, CH. (1978). Food Chemistry, 3, 293±317. Roach, R. R., & Hoseney, R. C. (1995). Cereal Chemistry, 72, 571± 577. Smith, E. B. (1971). Am. Diet. Assoc., 59, 572±574. Spies,R. D., & Hoseney, R. C. (1982). Cereal Chemistry, 59, 128±131. Stamp¯i, L., & Nerste, B. (1995). Food Chemistry, 52, 353±360. Stevens, D. J., & Elton, G. A. (1971). Starke, 23, 8±11.
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Tipples, K., D'Appolonia, B., Dirks, B., Hert, R., Kite, F., Matsuo, R., Patton, J., Ranum, P., Shuey, W., & Webb, B. (1980). In C. Shuey & K. Tipples (Eds.), The amylograph handbook (pp. 12±24). USA: The American Association of Cereal Chemists. Toufeili, I., Dagher, S., Shadarevian, S., Noureddine, A., Sarakbi, M., & Farran, M. T. (1994). Cereal Chemistry, 71, 594±601. Tye, R. (1988). Food Hydrocolloids, 2, 259±266. Xu, A., Chung, O. K., & Ponte, J. G. (1992). Cereal Chemistry, 69, 495±501. Xu, A., Ponte, J. G., & Chung, K. (1992). Cereal Chemistry, 92, 502±507.
Pasting properties of dierent wheat ¯our-hydrocolloid systems J.A. Rojas, C.M. Rosell, C. Benedito de Barber * Instituto de AgroquõÂmica y TecnologõÂa de Alimentos (CSIC), PO Box 73, 46100-Burjassot, Valencia, Spain Received 18 March 1998; accepted 25 June 1998
Abstract The eect of several hydrocolloids on the pasting properties and gelling behaviour of wheat ¯our was investigated. The in¯uence of the selected hydrocolloids (guar gum, pectin, alginate, k-carrageenan, xanthan and hydroxypropylmethylcellulose (HPMC)) on wheat ¯our was tested by using two dierent techniques: amylograph and dierential scanning calorimetry (DSC). In order to have a general overview of their eect, hydrocolloids were chosen from dierent sources implying a broad diversity of chemical structures. Dierences among hydrocolloid-wheat ¯our suspensions were more evident from amylographic analysis than from DSC examination. The hydrocolloid addition largely modi®ed the amylograph parameters of wheat ¯ourÐeven at the low levels tested [0.5 and 1% (w/w), ¯our basis], and the extent of their eect depended upon the chemical structure of the added hydrocolloid. The greatest eect on pasting temperature was observed when 1% alginate was added, which produced a decrease of ca 3 C. This reduction is really important since it implies an earlier beginning of starch gelatinization and, in turn, an increase in the availability of starch as enzyme substrate during baking period. Xanthan and pectin increased the cooking stability while k-carrageenan and alginate did not modify it. Setback was augmented by guar gum and HPMC but alginate, xanthan and k-carrageenan showed the opposite eect. The bump area related to the formation of amylose±lipid complex, was favoured by k-carrageenan, alginate and pectin, and slightly aected by xanthan and HPMC. In summary, each tested hydrocolloid aected in a dierent way the pasting properties of wheat ¯our. The results obtained are important for the appropriate use of these hydrocolloids as ingredients in the bread making process. # 1998 Elsevier Science Ltd. All rights reserved.
1. Introduction Wheat ¯our and particularly wheat starch is widely used in food industries. Gelatinization and gelation of starch are considered basic processes in the making of starch containing foods. Starch gelatinization and gelation involve consecutive changes which play a key role in processes such as bread baking, sauce thickening, gelling of pie ®llings, etc. The conditions in which the phenomena comprised in these processes occur, determine the quality of the ®nal food products. In the scienti®c literature dierent additives and ingredients have been used to modify the gelatinization± gelation processes, namely the pasting properties of starch. Sugars were added to starch mixtures in order to increase the gelatinization temperature and the paste viscosity by decreasing the availability of water (Evans & Haisman, 1982; Spies & Hoseney, 1982). Ganz (1965) described the eect of salt addition resulting in an improvement of the integrity of the starch granule and * Corresponding author. Tel.: +34-6-390-0022; fax: +34-6-3636301; e-mail: [email protected]
an increase of the paste consistency. Salts were also added to retard the retrogradation of the starch (Chang & Liu, 1991). Other compounds that have been extensively studied include dierent surfactants and emulsi®ers, which promote a reduction of the starch swelling and the paste consistency (Roach & Hoseney, 1995; Stamp¯i & Nerste, 1995). However, the principal eect produced by the emulsi®ers is to inhibit the retrogradation of amylose by forming complexes with the amylose chains (Ghiasi, Hoseney, & Varriano-Marston, 1982). Other compounds usually added to starch containing products are gums or hydrocolloids due to their desirable eect on the acceptability of foodstus. Hydrocolloids or gums have been widely used in food technology as additives in order to: (i) improve food texture (Armero & Collar, 1996a, 1996b), (ii) slow down the retrogradation of the starch (Davidou, Le Meste, Debever, & Bekaert, 1996), (iii) increase moisture retention, (iv) extend the overall quality of the product during time, and also (v) as gluten-substitutes in the formulation of gluten-free breads since gums could act as polymeric substances that mimic the viscoelastic properties of gluten in bread doughs
0268-005X/98/$Ðsee front matter # 1998 Elsevier Science Ltd. All rights reserved PII: S0268-005X(98)00066-6
28
J.A. Rojas et al./Food Hydrocolloids 13 (1999) 27±33
(Smith, 1971; Toufeili, Dagher, Shadarevian, Noureddine, Sarakbi, & Farran, 1994). Among the hydrocolloids tested are guar gum, locust bean gum or xanthan gum but the majority of those studies were focused on clarify the exact mechanism of interactions between the hydroxyl groups from the hydrocolloid and the starch components (Alloncle & Doublier, 1991), and those analysis have been performed by using high concentrations of hydrocolloids. The aim of this research is to determine the eect of hydrocolloids addition at the levels commonly employed in food product formulations, on the pasting properties and gelling behaviour of wheat ¯our. In order to have a general overview of their eect, hydrocolloids were chosen from dierent sources (vegetal and microbial) implying a broad diversity of chemical structures. The in¯uence of the selected hydrocolloids (guar gum, pectin, alginate, k-carrageenan, xanthan and hydroxypropylmethylcellulose) on wheat ¯our were tested by using two dierent techniques: viscograph and dierential scanning calorimetry (DSC). Brabender viscograph is an equipment extensively used to describe the rheological behaviour of wheat ¯our during its progressive cooking and cooling, and DSC is an useful tool which detects the heat ¯ow associated to the order-disorder transitions in starch, giving a quantitative measurement of gelatinization (Stevens & Elton, 1971). In this study both techniques have been used to characterise the modi®cations that starch gelatinization and gelation undergone by the addition of dierent hydrocolloids. 2. Materials and methods 2.1. Materials A commercial wheat ¯our from a local market was used for this study. Hydrocolloids were generously donated by several companies. The hydrocolloids tested included guar gum (Guardan127 from Grindsted), a low methoxylated pectin (Cesapectin LM/35 from Cesap S.p.a., Bergamo, Italy), sodium alginate (Satialgine S1100 from Bio-Industries, S.A.), a k-carrageenan (Genugel type UPC from The Copenhagen Pectin Factory Ltd.), xanthan gum food grade (xanthan from Jungbunzlauer) and hydroxypropylmethylcellulose (HPMC) (Methocel K4M from Dow Chemical, USA ).
to wheat starch suspension, as indicated elsewhere. The amylographic procedure was in accordance with ICC Method 126/1 (1992), using a heating-cooling cycle. Brie¯y, the suspension (with the pH previously adjusted to 5.5) was heated from 30 to 95 C increasing the temperature at 1.5 C/min, then it was held at 95 C for 20 min, afterwards the paste was cooled to 50 C and ®nally was kept at 50 C for 20 min. Fig. 1 shows the cycle previously described and the shape of the amylogram describing their characteristics. They included pasting temperature, maximum viscosity, viscosity of the paste on attaining 95 C, viscosity after the ®rst holding period, viscosity of the cooked paste after cooling to 50 C and ®nal viscosity at the end of the second holding period (Marzurs, Schoch, & Kite, 1957). The following parameters were de®ned: hot or cooking stability (expressed as the inverse of the dierence between viscosity at 95 C after the ®rst holding period and that at the beginning of this period), stability at 50 C or cooling stability (expressed as the inverse of the dierence between the end viscosity and the initial one of the second holding period), setback (the dierence between the viscosity at 50 C and the viscosity after the ®rst holding period) (Olkku & Rha, 1978). The bump area was measured by connecting the baseline of the bump from the starting point to the ending point of the bump peak (Xu, Chung, & Ponte, 1992). Two replicates were carried out in all cases. 2.3. Dierential scanning calorimetry Starch gelatinization was analysed by dierential scanning calorimetry (DSC). Experiments were carried out on a Perking±Elmer DSC-7. Samples of 20±30 mg taken from the ¯our-hydrocolloid suspensions prepared for the viscograph were hold in stainless steel capsules (PE 0319-0218) and heated from 30C to 95 C at 10 C/ min. An empty capsule was used as a reference. The starch gelatinization parameters in the DSC thermogram
2.2. Determination of the amylogram parameters The pasting properties of wheat ¯our were investigated with a Brabender Viscograph A/RH. When the addition of hydrocolloids were studied two dierent concentrations of each hydrocolloid [0.5 and 1.% (w/w) in a ¯our basis] were added to wheat ¯our suspension or
Fig. 1. A typical amylogram with a heating-cooling cycle. Some amylogram characteristics are included in the graph.
J.A. Rojas et al./Food Hydrocolloids 13 (1999) 27±33
29
All the hydrocolloids added to the wheat ¯our promoted a modi®cation of the pasting properties at the two levels tested. Each hydrocolloid aected in a particular way the amylograph parameters of the wheat ¯our, as can be seen in Table 1. This was expected because of the evident dierences in their chemical structures.
lower than the control at both tested concentrations. The decrease in pasting temperature caused by xanthan, k-carrageenan and alginate seems to be due to some kind of interaction between wheat starch and the hydroxyl groups of the hydrocolloids as pointed out Christianson, Hodge, Osborne, & Detroy (1981). In fact, the results obtained in some experiments carried out with wheat starch instead of wheat ¯our suspensions con®rm this supposition. In those analyses the decrease in the pasting temperature of starch promoted by alginate addition was even higher than the one observed in ¯our suspensions (3.3 C in starch versus 2.4 C in ¯our). This is very important because it may imply an earlier beginning of the gelatinization process, which would be traduced in a greater availability of starch as enzyme substrate during the baking period.
3.1. Eect of the hydrocolloid addition on the pasting temperature
3.2. Viscosity of the wheat ¯our-hydrocolloid suspensions
HPMC slightly increased the pasting temperature at both concentrations added. The same result was obtained with the addition of pectin although at 0.5% level only a slight increase was observed. The eect of the guar gum on the pasting temperature was dependant upon its concentration, an increase was produced by adding guar gum at 0.5% but the opposite eect was obtained at 1%. A decrease of the pasting temperature was observed when the very eective gelifying agents (k-carrageenan, alginate, and xanthan) were included. Xanthan caused a decrease at both concentrations, being more pronounced when adding 1% of this gum. k-Carrageenan promoted also a decrease at both concentrations being of almost 2 C at 1%. The highest modi®cation was observed with the addition of alginate, in this case the pasting temperature was 2.5 C
Regarding the maximum viscosity, it was reached in the range of 84±85 C. All the hydrocolloids aected the maximum viscosity of the wheat ¯our suspension (Table 1). Pectin and HPMC decreased the maximum viscosity and this reduction augmented with the hydrocolloid concentration. The rest of the hydrocolloids incremented the maximum viscosity. Again, the greatest eect was observed with alginate, followed by k-carrageenan and xanthan. Guar gum also increased the maximum viscosity but only when employed at the 1% level. The same trend of the maximum viscosity was observed when the hydrocolloids were added to wheat starch suspensions. The increments promoted on this parameter by the addition of alginate or k-carrageenan to starch were more pronounced than the previous, observed with ¯our. The maximum viscosity reached by starch increased from 320 to 370 BU when adding 0.5% (w/w) k-carrageenan and reached up to 540 BU in the case of alginate. From the above results it seems that the changes in maximum viscosity of the wheat ¯our paste due to the presence of hydrocolloids are caused mostly by the existence of interactions between the hydrocolloid and the starch granules. Maximum viscosity re¯ects the ability of the starch granules to swell freely before their physical breakdown. Starch with a high swelling power also yields a high maximum viscosity (Tipples, D'Appolonia, Dirks, Hert, Kite, Matsuo, Patton, Ranum, Shuey, & Webb, 1980). Therefore, from the above results it seems that the presence of alginate, k-carrageenan or xanthan promote an increment of the capacity of the starch granules to swell. Increments of the maximum viscosity has been previously observed with the addition of xanthan (Evans & Haisman, 1982; Christianson et al., 1981), i-carrageenan (Tye, 1988), and galactomannans like guar gum (Christianson et al., 1981; Alloncle, Lefebvre, Llamas, &
are the onset temperature (To), the conclusion temperature (Tc), the peak temperature or maximum temperature (Tp), and the gelatinization temperature range (the dierence between Tc and To). The amount of energy necessary for gelatinization (enthalpy) was automatically registered. 3. Results and discussion
Table 1 The eect of the hydrocolloid addition on the pasting properties of wheat ¯our. The experimental conditions are described in Section 2. Hydrocolloid
None Guar gum Pectin Alginate k-Carrageenan Xanthan HPMC
Maximum Viscosity at Concentration Pasting 95 C (%) temperature viscosity (BU) (BU) ( C) 0.5 1.0 0.5 1.0 0.5 1.0 0.5 1.0 0.5 1.0 0.5 1.0
66.8 67.5 66.0 66.9 67.6 64.4 64.3 66.4 65.0 66.4 66.0 67.3 67.4
646 650 720 600 560 728 790 670 700 678 660 645 620
408 390 380 380 335 495 540 385 380 480 445 430 420
30
J.A. Rojas et al./Food Hydrocolloids 13 (1999) 27±33
Doublier, 1989). Christianson (1982) assumed that the eect of hydrocolloids on maximum viscosity was a result from at least two phenomena, ®rst their interaction with solubilised starch and amylose, and second, this interaction cause an increase of the forces exerted onto the granules, as a consequence, the granule breakdown and the amount of solubilised starch is aected. Alloncle et al. (1989), viewing starch pastes as suspensions of swollen granules dispersed in a continuous macromolecular medium, stated that the hydrocolloid is present only in the continuous phase of the medium and as longer the starch granules swell the concentration of the hydrocolloid within the continuous phase increases leading to a substantial increase in viscosity of this phase. Alloncle and Doublier (1991) indicated that the modi®cations which result from the addition of hydrocolloids to a starch system are complex, and these can be ascribed to phase separation processes in relation to incompatibility phenomena between unlike polymers. Synergistic interactions between starch and hydrocolloids were previously observed by Bahnassey and Breene (1994), and these were dependent on the hydrocolloid structure so structural and rheological properties of the hydrocolloid are very relevant. In opposition, Appelqvist and Debet (1997) did not observe this synergistic eect. The addition of hydrocolloids also aected the viscosity attained at 95 C. The greatest increase was produced by alginate followed by xanthan and HPMC, although only in the case of alginate this increment augmented with the gum concentration. The other hydrocolloids had no eect on the viscosity at 95 C. The dierence of viscosity at 95 C and maximum viscosity has been related to the easiness of cooking the starch by several authors (Olkku & Rha, 1978; Tipples et al., 1980; Moros, 1997). The wheat ¯our paste exhibited a high viscosity drop when k-carrageenan or guar gum were included. This means that the interaction between these hydrocolloids and the ¯our aected the swollen granules making them more fragile and therefore, their addition favours the cooking. In opposition, greater stability than the control was observed when xanthan or HPMC were added to the ¯our, and in consequence longer cooking time should be necessary. Christianson et al. (1981) observed dierent behaviour of starch/xanthan and starch/guar gum mixtures in the viscosity drop after reaching the maximum. Nevertheless the analysis performed with starch suspension did not show any viscosity drop when adding hydrocolloid, the viscosities at 95 C were identical as the maximal viscosities. These results suggest that the interaction hydrocolloid±starch explains the viscosity decline observed with hydrocolloid-¯our mixtures. Moreover, they suggest the implication of the other ¯our components (lipids, proteins, carbohydrates nonstarch,..) in the viscosity decrease.
3.3. Eect of the hydrocolloid addition on the paste stability of wheat ¯our The next stage in the amylogram is the ®rst holding period, in which the temperature was kept at 95 C for 20 min. This period simulates the cooking time and only small changes in viscosity are produced. The parameter that de®nes this phase is the cooking or hot stability, thus high value means high stability of the already broken starch granules at the cooking temperature. The addition of some hydrocolloids modi®ed the cooking stability (Fig. 2). Guar gum and HPMC increased slightly this parameter, while the greatest stabilisation was promoted by pectin and xanthan (17 and 27-fold, respectively). The parameter used to de®ne the second holding period was the cooling stability and it indicates the paste behaviour in a form usually adopted for practical purposes. The cooling stability was slightly modi®ed by the hydrocolloids (Fig. 3), regardless of alginate which increase the stability by 4.7-fold respect to the control. 3.4. In¯uence of the hydrocolloids on the setback and the formation of the amylose-lipid complex The presence of 0.5% hydrocolloid concentration on a wheat ¯our suspension also produced modi®cations of the setback and the bump area. Regarding the setback, pectin did not modify it, guar gum and HPMC caused
Fig. 2. Eect of the hydrocolloid addition on the cooking or hot stability of the paste. This parameter is de®ned in Section 2. The hydrocolloid concentration in these analysis was 0.5% (w/w) (¯our basis).
J.A. Rojas et al./Food Hydrocolloids 13 (1999) 27±33
an increase, while alginate, k-carrageenan and xanthan provoked a decrease of this parameter (Fig. 4). During the cooling stage the amylose chains diused outside the starch granules during cooking, retrograde. This phenomenon is responsible of the ®rming of bread crumb
Fig. 3. Cooling stability of dierent hydrocolloid-wheat ¯our pastes. Cooling stability is de®ned in Section 2. The hydrocolloid concentration was 0.5% (w/w) (¯our basis).
Fig. 4. Eect of the hydrocolloid addition on the setback or starch retrogradation. Hydrocolloid concentrations were 0.5% (w/w) ¯our basis.
31
during the ®rst hours after baking. Thus, it is convenient to have the addition of additives and/or ingredients that promote a reduction of the setback, and in consequence, a delay of the ®rming crumb. Therefore, the addition of alginate, k-carrageenan or xanthan to wheat ¯our could be considered useful antistaling additives in the bread making process. A commonly known as bump area appears in the amylograms during the cooling stage. Measured values for the bump areas are shown in Fig. 5 for samples at 0.5% hydrocolloid level. Addition of guar gum, xanthan or HPMC did not change signi®cantly the size of the bump area while samples with the rest of hydrocolloids presented larger areas. The largest bump area was present with k-carrageenan. The bump area has been related with the extent of the formation of amylose-lipid complex during the cooling phase (Xu, Ponte, & Chung, 1992), in fact, when the study was done only with starch no eect was observed in the bump area (results not shown), due to the absence of the lipid fraction. High bump areas are associated to high concentration of amylose-lipid complex, and it is connected to a softened eect of the bread crumb (Xu, Chung et al., 1992). Hence, k-carrageenan added to wheat ¯our dough will produced the softest bread crumb; this eect together with the retardation of the setback convert this hydrocolloid in the best candidate as antistaling additive in bread formulation.
Fig. 5. Eect of the addition of hydrocolloid to the wheat ¯our paste on the bump area. The hydrocolloid concentration was 0.5% (w/w) (¯our basis).
32
J.A. Rojas et al./Food Hydrocolloids 13 (1999) 27±33
Table 2 The eect of the hydrocolloid addition on DSC parameters of wheat ¯our. Hydrocolloid concentration in the mixtures was 1% (w/w) ¯our basis. The procedure is described in Section 2. Hydrocolloid
To ( C)
Tp ( C)
Tc ( C)
Range ( C)
Enthalpy (J/g d.b.)
None Guar gum Pectin Alginate k-Carrageenan Xanthan HPMC
54.7 55.6 57.4 56.1 56.3 56.8 57.7
63.5 63.4 64.3 62.8 63.4 63.7 63.9
74.9 76.0 73.3 73.2 75.9 74.5 72.4
20.2 20.4 15.9 17.1 19.6 17.7 14.7
10.4 7.9 7.7 7.7 8.2 9.0 7.7
3.5. Eect of the hydrocolloid addition on the DSC parameters Despite the evident dierences observed on starch pasting properties when adding dierent hydrocolloids, no signi®cant dierences were detected by using dierential scanning calorimetry, as was previously reported by Biliaderis, Arvanitoyannis, Izydorcik, and Prokopowich (1997). DSC parameters are shown in Table 2. The interactions between starch and hydrocolloid promoted a delay of the starch gelatinization (a slight increase of the onset temperature (To). The peak temperature (Tp) of the hydrocolloid±¯our mixtures was similar to that of the control except for the alginate±¯our sample at 1% hydrocolloid level which was slightly lower. The hydrocolloids may interact with the starch to produce an increase or decrease of the temperature gelatinization ranges (Tc±To), depending on the hydrocolloids. The greatest eect on the transition ranges was observed with HPMC and pectin; in addition these two hydrocolloids besides to alginate gave the lowest values of enthalpy. The overall eect of hydrocolloids was a decrease in the enthalpy of gelatinization in the range of 1±2.7 J/g ¯our d.b. No correlation was observed between the DSC parameters and those obtained with the amylograph. 4. Conclusions The addition of dierent hydrocolloids to wheat ¯our promotes a great eect on the pasting properties of the resulting hydrocolloid-¯our mixture and the extent of this variation is highly dependent of the chemical structure of the hydrocolloid added. Modi®cations on the gelatinization and gelation processes of wheat ¯our by the addition of hydrocolloids are detected by the amylograph even at the low concentrations employed [0.5% (w/w) ¯our basis]. In general, the highest eect on pasting properties of wheat ¯our was promoted by alginate, k-carrageenan or xanthan. These hydrocolloids decrease
the pasting temperature, increase the maximum viscosity, decrease the tendency to retrograde and increase the size of the bump area. Regarding the in¯uence on the paste stability during the holding periods, it is useful to remark the increase on the cooking stability produced by pectin and mainly by xanthan; and the large increment on the cooling stability promoted by alginate. The analysis performed with starch suspensions revealed that these results could be attributed to the hydrocolloid-starch interactions during the heating stage while to explain the further behaviour the rest of the ¯our components have to be considered. The interaction between hydrocolloids and starch produces a slight modi®cation of the DSC parameters, being the most aected parameter the gelatinization temperature ranges, which are decreased. Finally, the above results indicate that the selection of the right hydrocolloid depends on the speci®c paste property to be modi®ed. For instance when looking for the reduction of the staling, k-carrageenan is the best additive due to both its softening and retarding the ®rming of the bread crumb eects. Acknowledgements The authors gratefully acknowledge the ®nancial support of the ComisioÂn Interministerial de Ciencia y Tecnologia (CICYT) and Consejo Superior de Investigaciones Cienti®cas (CSIC). J.A.R would like to thank the predoctoral grant from Consejo Nacional de Ciencia y Tecnologia (Mexico). References Alloncle, M., & Doublier, J. L. (1991). Food Hydrocolloids, 5, 455± 467. Alloncle, M., Lefebvre, J., Llamas, G., & Doublier, J. L. (1989). Cereal Chemistry, 66, 90±93. Appelqvist,I. A. & Debet, M. R. (1997) Food Rev. Int, 13, 163±224. Armero, E., & Collar, C. (1996a). Food Sci. and Technol. Int., 2, 323± 333. Armero, E., & Collar, C. (1996b). Journal of Food Science, 61, 299± 303. Bahnassey, Y. A., & Breene, W. M. (1994). Starch, 46, 134±141. Biliaderis, C. G., Arvanitoyannis, I., Izydorcik, M. S., & Prokopowich, D. J. (1997). Starch, 49, 278±283. Chang, S., & Liu, L. (1991). Journal of Food Science, 56, 564±570. Christianson, D. D. (1982). In D. R. Lineback, & G. E. Inglett (Eds.), Food carbohydrates (pp. 399±419). IFT Basic symposium series. Wesport, Connecticut: AVI Publishing Company Inc. Christianson, D. D., Hodge, J. E., Osborne, D., & Detroy, R. W. (1981). Cereal Chemistry, 58, 513±517. Davidou, S., Le Meste, M., Debever, E., & Bekaert, D. (1996). Food Hydrocolloids, 10, 375±383. Evans, I. D., & Haisman, D. R. (1982). Starch, 34, 224±231. Ganz, A. J. (1965). Cereal Chemistry, 42, 429±431. Ghiasi, K., Hoseney, R. C., & Varriano-Marston, E. (1982). Cereal Chemistry, 60, 58±61.
J.A. Rojas et al./Food Hydrocolloids 13 (1999) 27±33 Marzurs, E. G., Schoch, T. J., & Kite, F. E. (1957). Cereal Chemistry, 34, 141±145. Moros, M. C. (1997). Molineria y Panaderia, 1053, 48±53. Olkku, J., & Rha, CH. (1978). Food Chemistry, 3, 293±317. Roach, R. R., & Hoseney, R. C. (1995). Cereal Chemistry, 72, 571± 577. Smith, E. B. (1971). Am. Diet. Assoc., 59, 572±574. Spies,R. D., & Hoseney, R. C. (1982). Cereal Chemistry, 59, 128±131. Stamp¯i, L., & Nerste, B. (1995). Food Chemistry, 52, 353±360. Stevens, D. J., & Elton, G. A. (1971). Starke, 23, 8±11.
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Tipples, K., D'Appolonia, B., Dirks, B., Hert, R., Kite, F., Matsuo, R., Patton, J., Ranum, P., Shuey, W., & Webb, B. (1980). In C. Shuey & K. Tipples (Eds.), The amylograph handbook (pp. 12±24). USA: The American Association of Cereal Chemists. Toufeili, I., Dagher, S., Shadarevian, S., Noureddine, A., Sarakbi, M., & Farran, M. T. (1994). Cereal Chemistry, 71, 594±601. Tye, R. (1988). Food Hydrocolloids, 2, 259±266. Xu, A., Chung, O. K., & Ponte, J. G. (1992). Cereal Chemistry, 69, 495±501. Xu, A., Ponte, J. G., & Chung, K. (1992). Cereal Chemistry, 92, 502±507.