Chemical composition and starch digestibility of tortillas prepared with ...

International Journal of Food Sciences and Nutrition, February/March 2006; 57(1/2): 143 150

Chemical composition and starch digestibility of tortillas prepared with non-conventional commercial nixtamalized maize flours

´ NDEZ-SALAZAR1, E. AGAMA-ACEVEDO2, M. HERNA ´ REZ2 ´ YAGO-AYERDI1, J. TOVAR3, & L. A. BELLO-PE S. G. SA 1

Instituto Tecnolo´gico de Acapulco, Acapulco, Guerrero, Me´xico, 2Centro de Desarrollo de Productos Bio´ticos, Instituto Politećnico Nacional, Yautepec, Morelos, Me´xico, and 3Instituto de Biologıá Experimental, Facultad de Ciencias, Universidad Central de Venezuela, Caracas, Venezuela

Abstract Non-conventional nixtamalized maize flours elaborated by a factory in Mexico were used for tortilla preparation. Tortillas were stored at 48C for up to 72 h and the total starch, available starch, resistant starch and retrograded resistant starch were assessed. The traditional white tortilla, used as a control, showed higher protein and fat contents than blue maize tortilla, whereas a maize bean mixed tortilla had the highest protein, ash and fat contents. Lower total starch was obtained in the maize bean tortilla than in white and blue maize tortillas. The available starch content in all tortillas decreased with the cold-storage, although the change was more marked for blue-maize tortillas. The maize bean mixed tortillas exhibited the lowest in vitro digestibility, which is consistent with the relatively high resistant starch levels in the bean. Differences in resistant starch content were found between the two maize tortillas, which might be related to the softer texture of blue-maize tortilla. The starch digestibility features of these new types of nixtamalized maize flours open up the possibility of producing tortillas with variable nutritional properties.

Keywords: Tortilla, blue tortilla, bean, nixtamalized maize flours, starch digestibility

Introduction The technology for masa production of nixtamalized maize is very ancient. The Aztecs used an alkaline-thermal treatment (with volcanic ash) on maize grain to produce nixtamalization; the obtained nixtamal is ground for obtaining the masa and thereafter the tortillas (Reyes 1990). The 45% of tortillas consumed in Mexico are made with masa produced with the traditional nixtamalization procedure, but each day the small factories (‘tortillerias’) have been increasing the use of nixtamalized maize flours (NMF) for making tortillas. In the same sense the NMF are exported to different countries, where the elaboration and consumption of Mexican foods have increased in the last years (Yau et al. 1994). The increase in NMF fabrication is due to: saving space, time and equipment during the processing, the long shelf-life and transportation

Correspondence: Luis Arturo Bello-Pe´rez, Km 8.5 Carretera Yautepec-Jojutla, Colonia San Isidro, Apartado Postal 24, 62731 Yautepec, Morelos, Me´xico. Fax: 5273941896. E-mail: [email protected] ISSN 0963-7486 print/ISSN 1465-3478 online # 2006 Informa UK Ltd DOI: 10.1080/09637480600659136

144

M. Hernańdez-Salazar et al.

of the dry product (Bedolla and Rooney 1984). However, NMF production at the industrial level does not exactly follow the traditional nixtamalization conditions, resulting in tortillas that exhibit different sensorial and textural characteristics and stability during storage, as compared with traditionally made tortillas. The advantages NMF have been producing are that the companies diversify the products with the objective that people have a higher spectrum for food preparation using NMF. The process for NMF fabrication by alkaline extrusion starts with humectation of the maize grain using a solution of calcium hydroxide (0.3%). The extrusion cooking is carried out in an extruder with a screw inside a channel with control of the temperature. The screw transports the mixture through the channel to determine the time for maize grain cooking, and finally the masa obtained is dried and sieved (Almeida-Domıńguez et al. 1996; Paredes-Lo´pez et al. 2000). During cooking of the maize grain, several chemical and biochemical reactions are carried out, and cross-linking and molecular interactions also occur. These processes modify the physicochemical, structural and rheological characteristics of the masa and thereafter the functional and sensorial attributes of tortillas. A high percentage of these changes are due to modifications in starch structure, the major component of maize grain (70% dry basis). Starch is a polysaccharide of glucose units and is formed by two polymers of different structure: amylose is the essential lineal component, in which glucose units are join by linkages a(1 4); and amylopectin is the branching component, in which the glucose units are join by two kinds of linkages, a(1 4) and a(1 6), in the branch points (Whistler and Daniels 1984). In general, the consumption of tortillas in Mexico occurs together with beans; for this reason, the companies that produce NMF are fabricating a flour based on the mixture of both grains, with the objective of improving the nutritional supply, without affecting the relation of the grains. Garcıá-Osorio and Va´zquez-Carrillo (1997) obtained a nixtamalized mixture of maize bean and evaluated the quality of the masa, with the masa-prepared tortillas, and tested the chemical, sensorial and shelf-life characteristics of them. Recently, our research group reported starch digestibility tests in mixture of tortillas and cooked beans; the results showed that the glycemic index decreases when tortillas are consumed in combination with beans (Saýago-Ayerdi et al. 2005). On the other hand, the use of pigmented maize to produce nixtamalized products is increased due to the amount of anthocyanins and the antioxidant effect of these compounds, which is related to cancer prevention (Zazueta-Morales et al. 2000; Corte´s-Go´mez et al. 2005). Otherwise, the food producers develop new products based on pigmented maizes with the idea of obtaining a functional food and new products with better visual characteristics supplied by the color of the anthocyanins in snacks and breakfast cereals. The objective of this study was to evaluate the starch digestibility in tortillas elaborated with non-conventional commercial NMF. Materials and methods Sample preparation Three non-conventional flours were acquired from a local supermarket in Acapulco, Mexico: white maize flour (Maseca S.A. de C.V., Leoń, Mexico), blue maize flour (Minsa, S.A. de C.V., Toluca, Mexico) and a composite maize bean flour (Maseca

Chemical composition and starch digestibility of tortillas

145

S.A. de C.V.) were used to make tortillas according to Rendoń-Villalobos et al. (2002). After cooling, tortillas were packed in poly-ethylene bags (20 /30 cm2; Pla´sticos de Me´xico, S.A. de C.V., Mexico) and stored for 24, 48 and 72 h at 48C. After storage, the samples were oven-reheated for 30 sec each side, at an approximate temperature of 2508C, cooled down to 308C and analyzed ‘as eaten’, simulating cooking and storage conditions applied in Mexican households. A control sample (without storage) was also analyzed. Three replicates from each preparation were prepared. Chemical composition The moisture content was determined by gravimetric heating (1309/28C for 2 h) using a 2 3 g sample. Ash, protein and fat were analyzed according to AACC methods 08-01, 46-13, and 30-25, respectively (AACC 2000). In vitro digestibility tests Total starch (TS) was determined by the method of Gon˜i et al. (1997). The potentially available starch content was assessed following the multienzymatic protocol of Holm et al. (1986) using Termamyl† (Novo A/S, Copenhagen, Denmark) and amyloglucosidase (Boehringer, Mannheim, Germany). Resistant starch was measured by two different protocols: the retrograded resistant starch (RRS or RS3) content was measured as starch remnants in dietary fiber residues, according to the so-called ‘Lund method’ as modified by Saura-Calixto et al. (1993); and the method proposed by Gon˜i et al. (1996) was employed to estimate the total amount of indigestible starch (comprising the RS2, RS3 and part of RS1 fractions). In all these measurements a part of the cooked bean preparation was weighed into a test tube or a beaker and homogenized with the appropriate solution for each technique, under controlled conditions *first step (speed level 2, 1 min) and second step (speed level 2.5, 1 min) *using a Polytron homogenizer (Polytron PT 1200; Kinematica AG, Lucerne, Switzerland). Statistical analysis A randomized complete design with three replications was used to analyse changes during samples storage. Data were analysed using one-way analysis of variance procedures. Where analysis showed significant differences (P B/ 0.05), means were compared using Tukey’s tests. Statistical analyses were run using the computer SPSS V. 6.0 software (SPSS Institute Inc., Cary, NC, USA). Results and discussion Chemical composition of tortillas The moisture contents of the different samples varied markedly; values of 19.15%, 13.40% and 15.35% were recorded for the white maize tortilla, the blue maize tortilla and the mixed (maize bean) tortilla, respectively (Table I). The moisture content of the maize bean tortilla relates to the moisture content of each grain ingredient, as raw bean flours have shown values between 8.87 and 9.65% (Vargas-Torres et al. 2004;

146

M. Hernańdez-Salazar et al. Table I. Chemical composition of white, blue and maize bean mixture tortillas (%).

Sample White tortilla Blue tortilla Maize bean tortilla

Moisture

Protein (NX 5.85)

Ash

Fat

19.159/0.33A 13.409/0.42B 15.359/0.44C

9.319/0.05A 8.319/0.13B 10.539/0.10C

1.889/0.01A 1.959/0.00A 2.959/0.00B

3.019/0.01A 2.189/ 0.03B 3.609/0.09C

Values presented as means of three replicates9/standard error, dry basis. Values followed by the same uppercase letter in the same column are not significantly different (P B/0.05).

Osorio-Dıáz et al. 2005), which are lower than those determined in raw flours (9.0 11.0%) of different maize varieties (Meńdez-Montealvo et al. 2005). However, the observed differences might be a consequence of the variable water retention capacities of the starch ingredients, which depends largely on morphological characteristics of the granules and on the molecular structure of the starch components (amylose and amylopectin) (He´rnańdez-Lauzardo et al. 2004; Manek et al. 2005). The lowest protein content was found in blue maize tortilla, and the mixed maize bean tortilla showed the highest value. This pattern is due to the protein contribution of beans to the final content, since beans are characterized by high protein levels (20 30% dry basis) (Reyes-Moreno and Paredes-Lo´pez, 1993). Agama-Acevedo et al. (2004) reported protein values ranging between 7.51 and 8.63% for tortillas prepared form commercial NMF, and suggested that protein content depends on the maize variety used in the preparation of the NMF (MeńdezMontealvo et al. 2005). The lipid contents of white and mixed maize bean tortillas were slightly different, a pattern that may also depend on the maize variety used in the preparation of the NMF, since beans are characterized by low lipid contents (1.3 2.8%) (Vargas-Torres et al. 2004; Osorio-Dıáz et al. 2005). Such a dependence of fat content on maize variety was evident by the relatively low lipid value recorded for blue maize tortillas. In relation to ash content, again the mixed bean-maize tortilla showed the highest value, which must be associated with the higher ash content in beans; in fact, values between 3.6 and 5.2% have been reported in beans and other legumes (Bravo et al. 1999; Vargas-Torres et al. 2004; Osorio-Dıáz et al. 2005), whereas lower ash values (1.1 1.7%) were determined in Mexican maize varieties (MeńdezMontealvo et al. 2005). The ash content of tortillas prepared with commercial flour presented values between 1.28 and 1.54% (Agama-Acevedo et al. 2004), similar to those determined here in white and blue maize tortillas. Starch digestibility The TS in white and blue tortillas was similar and slightly higher than in the combined bean-maize tortillas (Table II). A similar pattern was shown in a previous study with NMF tortillas, where TS values ranged between 76 and 80% (AgamaAcevedo et al. 2004). Variations in TS among the different maize tortilla samples may be explained by the maize variety used for the flour preparation. TS in maize bean tortilla was lower than in maize tortillas, which is due to the lower starch content in beans (Tovar and Melito 1996; Vargas-Torres et al. 2004; Meńdez-Montealvo et al. 2005) as compared with maize. TS levels remained invariable throughout the storage period, regardless of the tortilla type (Table II). The influence of the legume on overall properties of mixed tortillas was more evident when available starch (AS) was tested. Maizebean tortilla had lower AS than


147

Table II. Total starch, available starch, resistant starch, and retrograded resistant starch contents in freshly prepared and cold-stored tortillas. Total starch (%)a

Available starch (%)b

Resistant starchc

Retrograded resistant starchd

White tortilla 0h 24 h 48 h 72 h

67.249/1.01A 65.039/1.42A 65.619/0.45A 65.289/0.65A

63.499/0.36A 62.809/0.50A 61.109/0.16B 60.599/0.23B

2.559/0.40A 2.869/0.07B 3.269/0.17C 3.439/0.10C

1.929/0.10A 2.839/0.12B 2.469/0.15C,B 2.599/0.19C

Blue tortilla 0h 24 h 48 h 72 h

68.579/1.10B 68.549/1.14B 68.389/0.85B 68.579/0.38B

67.479/0.40C 64.489/0.40D 63.969/0.30A 61.669/0.13B

1.989/0.09D 2.429/0.13E 2.889/0.16F 3.079/0.07G

1.799/0.07D 2.059/0.07E 2.279/0.13F 2.389/0.17G

Maize bean tortilla 0h 24 h 48 h 72 h

65.649/2.32C 65.449/2.27C 65.699/1.94C 64.449/1.12C

60.269/0.66G 59.609/0.35G 58.589/0.50G 57.019/0.22H

2.999/0.08H 3.439/0.19I,H 3.849/0.66I 4.359/0.43I

2.639/0.42H 2.829/0.23I,H 3.179/0.45I 3.359/0.40I

Storage time

Values presented as mean9/standard error of three replicates, dry matter basis. Values followed by the same uppercase letter in the same column are not significantly different (P B/0.05). a Using the method of Gon˜i et al. (1997). b Using the method of Holm et al. (1986). c Using the method of Gon˜i et al. (1996). d Using the method of Saura-Calixto et al. (1993).

maize tortillas when they are compared at the same storage time. White tortilla presented the lowest difference between the AS values at 0 and 72 h of storage, while blue tortilla exhibited the highest difference in those values. Such a reduction in AS content during storage at 48C may be explained by the formation of resistant starch due to the retrogradation phenomenon that takes place when a starchy product is cold-stored (Englyst et al. 1992). As a general rule, the lower the temperature the faster the retrogradation, because nucleation and crystal growing is favored (Biliaderis 1991); hence retrogradation occurs with marked dependence on the storage temperature (Farhat et al. 2001). Tortillas elaborated with commercial NMF ranged between 64.5 and 74.9% (Agama-Acevedo et al. 2004), although Rendon-Villalobos et al. (2002) showed AS values between 72.92 and 70.97% for laboratory-made tortillas; interestingly, both studies showed a time-related AS decrease. Such observations do not differ much from here-reported data. The maize bean mixed tortilla showed the lowest AS values, which is a consequence of the reduced starch content of pulses as compared with maize and most other cereals (Tovar and Melito 1996; Bravo et al. 1999; Rosin et al. 2002, Vargas-Torres et al. 2004). In a maize tortilla bean combination an AS value of 52.5% was recorded recently (Saýago-Ayerdi et al. 2005), which was lower than that found in this study in the maize bean tortilla at the same storage time (65.64%). The difference might be due to the process carried out for obtaining both samples. Both white and blue maize tortillas assessed in this study underwent lower RS increases with cold-storage than maize bean mixed tortilla, values that agree with the AS values recorded. The higher RS values determined in the maize bean tortilla may

148


be explained by the crystallite structure, physical inaccessibility (Wu¨rsch et al. 1986; Tovar 1994) and marked susceptibility to retrograde (Tovar et al. 2002) exhibited by starch in legume seeds *factors that result in a restricted overall enzymatic hydrolysis. Differences in RS contents were found among maize tortillas, with lower values for blue tortillas, which might be related to an apparently softer tactile texture shown by this sample. In a previous study, tortillas elaborated with commercial DMFs (drymasaflour) from white maize showed RS levels ranging between 1.20 and 3.79, contents that depended on the process followed for the NMF production (AgamaAcevedo et al. 2004). RS values in white tortilla were similar to those determined in laboratory-made tortillas (3.12 3.87%) (Reńdon-Villalobos et al. 2002) and in white maize commercial tortilla (2.14 3.78%; Saýago-Ayerdi et al. 2005). To the best of the authors’ knowledge, there are no published data on RS content in tortillas elaborated with pigmented maizes. RS values recorded here for the maize bean tortilla resemble those determined in a 60:40 (w/w) mixture of commercial maize tortilla and bean, cooked separately (Saýago-Ayerdi et al. 2005). Differences between RS and RRS levels were registered for all tortillas analyzed, which indicates that RS2, and perhaps some RS1, are also present in these materials. The RRS values for freshly prepared white and blue tortillas were 1.92 and 1.79%, respectively, values that were lower than in tortillas prepared from fresh masa and immediately analysed 2.5% (Campus-Baypoli et al. 1999). It has been mentioned that heat applied during baking promotes the interaction of starch with other maize components, making it less accessible to enzyme hydrolysis (Campas-Baypoli et al. 2002). RRS contents may also be affected by both maize variety and processing conditions during flour production (Agama-Acevedo et al. 2004). RRS values in maize tortillas stored for 24, 48 and 72 h ranged between 2.05 and 2.59%, with a slight tendency to increase with storage length. These values were similar to those determined in tortillas stored for 2, 24, 48 and 72 h (2.2 2.9%), either at room or refrigeration temperature (Campas-Baypoli et al. 2002). Rendoń-Villalobos et al. (2002) determined RRS values between 1.06 and 1.84% for stored tortillas prepared from fresh masa; such contents were lower than both those found here and in older studies (2.2 2.9%) by Campas-Baypoli et al. (1999, 2002). Recently, RRS levels ranging between 1.29 and 2.84% were determined in tortillas prepared with commercial NMF (Agama-Acevedo et al. 2004), samples that were prepared similarly to those analyzed here. The mixed maize bean tortilla had similar RRS values (2.63 3.35%) to those reported in the tortilla-bean combination studied by Saýago-Ayerdi et al. (2005), stored for equivalent times. Thus, it seems that RRS pattern of NMF prepared with the maize bean mixture resembles that observed when both food items are prepared separately and put together before consumption. Conclusions The contribution of the bean in the NMF was noticeable in protein, ash and fat contents, since the highest contents of these parameters corresponded to mixed maize bean tortillas. White tortilla showed higher protein and fat contents than blue tortilla, indicating that the cereal variety affects these parameters in an important manner. AS was different in the various maize tortillas (white and blue), and the lowest value was recorded for the maize bean mixed tortilla. Blue tortilla exhibited the lowest RS content whereas maize bean mixed tortilla showed the highest level.


149

The in vitro starch digestibility of tortillas studied here depended largely on the maize source, although the maize bean blend appeared to decrease starch digestibility as compared with regular maize-based tortillas. The starch digestibility features of these new types of nixtamalized maize flours open the possibility of producing tortillas with variable nutritional properties.

Acknowledgements The authors acknowledge economic support from CGPI-IPN, EDI-IPN. COFAAIPN, Tecnolo´gico de Acapulco and COSNET. References AACC. 2000. Approved methods of the AACC. 10th ed. St Paul, MN: The Association. Agama-Acevedo E, Rendoń-Villalobos R, Tovar J, Paredes-Lo´pez O, Islas-Hernańdez JJ, Bello-Pe´rez LA. 2004. In vitro starch digestibility changes during storage of maize flour tortillas. Nahrung/Food 48:38 42. Almeida-Domıńguez HD, Cepeda M, Rooney L. 1996. Propierties of commercial nixtamalized corn flours. Cereal Foods World 41:624 630. Bedolla S, Rooney LW. 1984. Characteristics of U.S. and Mexican instant maize flours for tortilla and snack preparation. Cereal Foods World 29:732 735. Biliaderis CG. 1991. The structure and interactions of starch with food constituents. Can J of Physiol Pharm 69:60 78. Bravo L, Siddhuraju P, Saura-Calixto F. 1999. Composition of underexploited Indian pulses. Comparasion with common legumes. Food Chem 64:185 192. Campus-Baypoli ON, Rosas-Burgos EC, Torres-Cha´vez P, Ramirez-Wong B, Serna-Saldı´var SO. 1999. Physicochemical changes of starch during maize tortilla production. Starch/Sta¨rke 51:173 177. Campas-Baypoli ON, Rosas-Burgos EC, Torres-Chave´z PI, Ramirez-Wong B, Serna-Saldivar SO. 2002. Physicochemical changes of starch in maize tortillas during storage at room and refrigeration temperatures. Starch/Sta¨rke 54:358 363. Corte´s-Go´mez A, San Martıń-Martıńez E, Martıńez-Bustos F, Va´zquez-Carrillo GM. 2005. Tortillas de blue maı´z (Zea mays L.) prepared by a fractionated process of nixtamalization: analysis using response surface methodology. J Food Eng 66:273 281. Englyst HN, Kingman SM, Cummings JH. 1992. Classification and measurement of nutritionally important starch fractions. Eur J Clin Nutr 46(Suppl 2):S33 S50. Farhat IA, Protzmann J, Becker A, Valles-Pamies B, Neale R, Hill SE. 2001. Effect of the extent of conversion and retrogradation on the digestibility of potato starch. Starch/Sta¨rke 53:431 436. Garcıá-Osorio C, Va´zquez-Carrillo MG. 1997. Evaluacioń de la calidad nixtamalera-tortillera de mezclas maı´z-frijol endurecido (Zea mays-Phaseolus vulgaris ). Arch Latin Nutri 47:377 381. Gon˜i I, Garcia-Diaz L, Manãs E, Saura-Calixto F. 1996. Analysis of resistant starch: A method for foods and food products. Food Chem 56:445 449. Gon˜i I, Garcıá-Alonso A, Saura-Calixto F. 1997. A starch hydrolysis procedure to estimate glycemic index. Nutr Res 17:427 437. Hernańdez-Lauzardo AN, Meńdez-Montealvo G, Vela´zquez del Valle MG, Solorza-Feria J, Bello-Pe´rez LA. 2004. Isolation and partial characterization of mexican Oxalis tuberosa starch. Starch/Sta¨rke 56:357 363. Holm J, Bjo¨rck I, Drews A, Asp NG. 1986. A rapid method for the analysis of starch. Starch/Sta¨rke 38:224 229. Manek RV, Kunle OO, Emeje MO, Builders P, Rao GVR, Lo´pez GP, Kolling WM. 2005. Physical, thermal and sorption profile of starch obtained from Tacca leontopetaloides . Starch/Sta¨rke 57:55 61. Meńdez-Montealvo G, Solorza-Feria J, Vela´zquez del Valle M, Go´mez-Montiel N, Paredes-Lo´pez O, BelloPe´rez LA. 2005. Composicioń quı´mica y caracterizacioń calorime´trica de hı´beidos y variedades de maı´z cultivadas en Me´xico. Agrociencia 39:267 274. Osorio-Dıáz P, Tovar J, Paredes-Lo´pez O, Acosta-Gallegos JA, Bello-Pe´rez LA. 2005. Chemical composition and in vitro starch bioavailabity of Phaseolus vulgaris (L) cv Mayocoba. J Sci Food Agric 85:499 504.

150


Paredes-Lo´pez O, Serna-Saldı´var S, Guzmań-Maldonado S. 2000. In: El Colegio de Sinaloa, editor. Los alimentos ma´gicos de las culturas Indı´genas de Me´xico *El caso de la tortilla. Me´xico: Culiacań Sin. Rendoń-Villalobos R, Bello-Pe´rez LA, Osorio-Dıáz P, Tovar J, Paredes-Lo´pez O. 2002. Effect of storage time on in vitro digestibility and resistant starch content of nixtamal, masa and tortilla. Cereal Chem 79:340 344. Reyes CP. 1990. El maı´z y su cultivo. 1st ed. Me´xico DF: AGT Editor SA. Reyes-Moreno C, Paredes-Lo´pez O. 1993. Hard to cook phenomenon in common beans: a review. Crit Rev Food Sci Nutr 33:227 286. Rosin MP, Lajolo MF, Menezes WE. 2002. Measurement and characterization of dietary starches. J Food Comp Anal 15:367 377. Saura-Calixto F, Gon˜i I, Bravo L, Manãs E. 1993. Resistant starch in foods: modified method for dietary fiber residues. J Food Sci 58:642 645. Saýago-Ayerdi SG, Tovar J, Osorio-Dıáz P, Paredes-Lo´pez O, Bello-Pe´rez LA. 2005. In vitro starch digestibility and predicted glycemic index of corn tortilla, blank beans and tortilla-bean mixture: effect of cold storage. J Agric Food Chem 53:1281 1285. Tovar J. 1994. Bioavailability of carbohydrates on legumes: digestible and indigestible fractions. Arch Latin Nutr 44:36 40. Tovar J, Melito C. 1996. Steam-cooking and dry heating produce resistant starch in legumes. J Agric Food Chem 44:2642 2645. Tovar J, Melito C, Herrera E, Rascoń A, Pe´rez E. 2002. Resistant starch formation does not parallel syneresis tendency in different starch gels. Food Chem 76:455 459. Vargas-Torres A, Osorio-Dıáz P, Islas-Hernańdez JJ, Tovar J, Paredes-Lo´pez O, Bello-Pe´rez LA. 2004. Starch bioavaility of five cooked black bean (Phaseolus vulgaris L) varieties. J Food Comp Anal 17:605 612. Whistler RL, Daniels JR. 1984. Molecular structure of starch. In: Whistler RL, Bemiller JN, Paschall EF, (editors). Starch, chemistry and technology. New York: Academic Press Inc. pp 154 180. Wu¨rsch P, Del Vedovo S, Koellreuter B. 1986. Cell structure and starch nature as key determinants of the digestion rate of starch in legumes. Am J Clin Nutr 43:25 29. Yau JC, Waniska RD, Rooney LW. 1994. Effects of food additives on storage stability of corn tortillas. Cereal Foods World 39:396 402. Zazueta-Morales JJ, Martıńez-Bustos F, Jacobo-Valenzuela N, Ordorica-Falomir C, Paredes-Lo´pez O. 2000. Effect of the addition of calcium hydroxide on some characteristics of extruded products from blue maize (Zea mays L.) using response surface methodology. J Sci Food Agric 81:1379 1386.