Showing papers in "Cereal Chemistry in 1993"

Fine structure of amylopectin in relation to gelatinization and retrogradation behavior of maize starches from three wx-containing genotypes in two inbred lines

Abstract: had A:B chain ratios within the range of 0.9-1.1. The A:B chain ratio of 1.5, together with the high proportion of longer chains in that sample, is consistent with the interpretation that the population of A chains in this sample contains some unusually long chains. In both lines, the starch granules from the ae wx genotype had the highest AH and Tmax for both gelatinization and retrogradation. The high AHfor the ae wx starches might be attributed to greater amounts of longer chains in these amylopectins. Except the starches from the wx genotype at 10% concentration, all of the gelatinized starch samples showed a differential scanning calorimetry endothermic peak after being stored at 4°C for seven days. Retrogradation AH was highest for the ae wx starches, both in absolute terms and as the proportion of gelatinization AH. In most cases retrogradation AH was higher (on dry weight basis) for 30% than for 10% starch; for the du wx starches, the AH at 30% starch was approximately twice that at 10%. and maltotriose to other linear fractions of debranched 3-limit dextrin (Peat et al 1956). The maltose and maltotriose represent the A chains of the native amylopectin. Alternatively, Hizukuri (1986) estimated the A:B chain ratios for several starches from

Swelling and gelatinization of cereal starches. IV. Some effects of lipid-complexed amylose and free amylose in waxy and normal barley starches

Abstract: Cereal Chem. 70:385-391. Amylose (AM) and lysophospholipid (LPL) contents were directly correlated in barley starches, but the linear regressions that described the relationships in waxy and nonwaxy starches were quite different. The data indicated that AM exists partially as lipid-complexed amylose (L.AM), with an LPL-to-L.AM ratio of 1:7 and partially as lipid-free amylose (F.AM). The [13]C-cross polarization/magic angle spinning-nuclear magnetic resonance (CP/MAS-NMR) spectra of the nonwaxy starches had a broad resonance with a chemical shift of 31.2 +/- 0.4 ppm, which is characteristic of midchain methylene carbons of fatty acids in the solid state or in V-amylose (V-AM) complexes. The extracted lipid was a viscous liquid that, when mixed with seven parts AM, did not give a discernible peak under the conditions used to acquire the solid- state spectra. However, when the lipid was complexed with AM, it gave a typical V-AM spectrum and a broad resonance at 31.8 ppm. This proves lipid complexed with L.AM existed in the native starches and was not an artifact formed subsequently from free LPL and F.AM. The intensity of the resonance was consistent with the LPL content of the starches. Independent supporting evidence was obtained by differential scanning calorimetry that showed a constant enthalpy for disordering of amylopectin, DeltaH(AP), for all waxy and nonwaxy starches, regardless of L.AM content and, hence, no exothermic formation of L.AM during starch gelatinization. Twelve waxy barley starches used in this study contained 0.8-4.0% L.AM and 0.9-6.4% F.AM; six nonwaxy starches contained 6.1-7.2% L.AM and 23.1-25.0% F.AM. All starches had essentially identical AP structures, as show by the chain lengths of debranched starches fractionated by gel-permeation chromatography and high-performance liquid chromatography. L.AM and F.AM appeared to have quite different effects on starch gelatinization behavior. Peak gelatinization temperature (Tp) of the waxy starches was p ositively correlated with L.AM content; because the Tp of the nonwaxy starches was much lower than predicted from the regression equation for the waxy starches, we concluded that F.AM lowered Tp. Swelling of starches at 80 C is essentially a property of AP content that is inhibited by LPL, but the relationship is not strictly linear. An improved equation to describe swelling properties assumed that 80% of the F.AM swelled with the AP fraction, although swelling was inhibited by L.AM0.485.

Preparation and pasting properties of wheat and corn starch phosphates

Abstract: Cereal Chem. 70(2):137-144 Wheat and corn starches were phosphorylated in a semidry state at P from phospholipids), and its pasting properties showed optimum 1300C with 5% (based on dry starch) sodium tripolyphosphate (STPP) thickening power with shear stability when cooked at 950C. The best and/or 2% sodium trimetaphosphate (STMP). All phosphorylation corn starch phosphate, judging from its paste properties, was obtained reactions were done using 5% sodium sulfate and adjusting the initial at an initial pH of 11 with STPP and contained 0.16% P (including reaction pH by adding aqueous sodium hydroxide or hydrochloric acid 0.02% from lipid). When corn or wheat starch was heated with a mixture to the prereaction slurries. As reaction pH was increased from 6 to 11, of 5% STPP and 2% STMP, the best product when pasted at 950C the degree of phosphorylation decreased 40-50% with STPP, whereas was obtained at the initial reaction pH of 9.5. Paste clarity of the it increased 100% with STMP. At an initial reaction pH of 10 with STPP, phosphorylated starches indicated that cross-linking accelerated rapidly a wheat starch phosphate was obtained with 0.22% P (including 0.05% above pH 8 with STMP but above pH 10 with STPP. Native starches generally contain small amounts (<0.1%) of phosphorus (P). In root and tuber starches, P is covalently linked to the starch (Hodge et al 1948, Posternak 1951, Hizukuri et al 1970), whereas in cereal starches it occurs mostly as contaminating phospholipids (Schoch 1942, Tabata et al 1975, Meredith et al 1978, Morrison 1978). Starch phosphates, which are prepared by chemical methods, have been reported to give clear pastes of high consistency, with good freeze-thaw stability and emulsifying properties (Kerr and Cleveland 1959, 1962; Klostermann 1963; Nierle 1969; Lloyd 1970). The preparation, properties, and uses of phosphorylated starches were reviewed by Solarek (1986). Starch phosphates may be grouped into two classes: monostarch phosphates and distarch phosphates (cross-linked starches). In general, monoesters are introduced at a much higher level of substitution on starch than are diesters because even a very few cross-links can drastically alter paste and gel properties of starch. Formation of distarch phosphates is generally considered the most important reaction used to prepare modified food starches. In the United States, phosphorous oxychloride and three inorganic phosphate salts (sodium orthophosphate, sodium tripolyphosphate [STPP], and sodium trimetaphosphate [STMP]) may be used to prepare food starch phosphates (CFR 1991). During phosphorylation, pH plays a major role in determining the ratio of monoester bonds to diester bonds. The phosphorylation of starch with phosphate salts has been investigated by several authors (Kerr and Cleveland 1959, 1960, 1962; Paschall 1964; Nierle 1969; Lloyd 1970; Wurzburg et al 1979, 1980). The objectives of this study were 1) to compare the reaction of semidry wheat and corn starches with STPP and STMP and 2) to use STPP or a combination of STPP and STMP to prepare wheat and corn starch phosphates having nearly the maximum P (0.4%) allowed by regulation (CFR 1991), as well as white color, high paste consistency, short paste texture, and good shear stability upon cooking at atmospheric pressure. MATERIALS AND METHODS Materials Prime wheat starch was donated by Midwest Grain Products, Inc. (Atchison, KS) and corn starch by A. E. Staley Manufacturing Co. (Decatur, IL). Potato starch was purchased from Sigma Chemical Co. (St. Louis, MO). The wheat, corn, and potato starches contained 0.05, 0.02, and 0.06% P, respectively. Penta'Contribution 92-354-J, from the Kansas Agricultural Experiment Station, Manhattan 66502. 2 Research associate, Department of Food Science and Human Nutrition, Iowa State University, Ames 50011. 3 Professor, Department of Grain Science and Industry, Kansas State University, Manhattan 66506. © 1993 American Association of Cereal Chemists, Inc. sodium tripolyphosphate (STPP) was purchased from Fisher Scientific Company, Pittsburgh, PA, and trisodium trimetaphosphate (STMP) and blue dextran 2000 were from Sigma Chemical Co. All other chemicals were reagent grade unless specified. Preparation of Starch Phosphates Starch was phosphorylated by the procedure described by Kerr and Cleveland (1959), with two modifications. Sodium sulfate was used in all reactions, and starch that had been impregnated with an aqueous solution of sodium sulfate and phosphate salt(s) was not filtered or centrifuged to remove excess salt solution. Instead, the entire slurry was dried to less than 15% moisture content before reaction at high temperature. Fifteen grams of STPP and 6 g of STMP, separately or together, were dissolved in 300 ml of water containing 15 g of sodium sulfate. The pH of the solution was adjusted between 6 and 11 by adding 10% aqueous HCO or NaOH. Starch (300 g, db) was dispersed in the solution. Then the pH of the dispersion was readjusted with 5% aqueous HCl or NaOH, and the total weight was brought to 667 g by adding water. The starch solids in the flowable dispersion amounted to 45%. The slurry was stirred for 1 hr at room temperature and dried to 10-15% moisture at 40°C in a forced-air oven. To effect phosphorylation, the dried starch cake in the dish was heated for 2 hr at 130° C in a forced-convection oven. After being cooled to room temperature, the reaction mixture was dispersed in distilled water (350 ml), and the pH of the dispersion was recorded. The starch was recovered by centrifugation (1,500 X g, 10 min) and redispersed in 600 ml of distilled water. The dispersion was adjusted to pH 6.5 with aqueous 5% HCl or 5% NaOH solution, and after three washings with water (3 X 600 ml), the product was dried at 400 C. Duplicate runs of the phosphorylation procedure gave good reproducibility as judged by P incorporated into the starches and by the pasting properties. Determination of Phosphorus in Starch Phosphorus in starch was determined by the procedure of Smith and Caruso (1964). Unless otherwise stated, P levels are the sum of endogenous P in a starch plus that incorporated by chemical treatment. Water Uptake by Starch The amount of water imbibed by starch was measured by the procedure of BeMiller and Pratt (1981). Paste Consistency The pasting of starch samples was examined in a Brabender Viscograph-E (C. W. Brabender Instruments Inc., Hackensack, NJ) using 75 rpm and a torque of 700 cm-g equivalent to 1,000 BU. The starch slurry (400 ml at 7.5% starch solids) was adjusted to pH 6.5 with a few drops of 5% HCl or 5% NaOH solution, pasted at a heating rate of 1.5°C/min from 30 to 95°C, held Vol. 70, No. 2,1993 137 at 95C for 30 min, cooled at 1.5 C/min from 95 to 50'C, and finally held at 500 C for 30 min. To permit examination of the effects of sodium ions on paste consistency, aliquots (0.2-1.0 ml) of aqueous NaCl solution (4M) were added to aqueous suspensions of a wheat starch phosphate (degree of substitution [DS] = 0.01) prepared at pH 10 using STPP. The resulting sodium ion concentrations in the suspensions were 0.002-0.01 M. Light Transmittance of Starch Pastes The transmittance of a starch paste was measured by the procedure of Kerr and Cleveland (1959). A 1% aqueous suspension of starch near neutral pH was heated in a boiling water bath for 30 min with intermittent shaking. After the suspension was cooled for 1 hr at 250 C, transmittance was read at 650 nm. Freeze-Thaw Stability Freeze-thaw stability was determined as described by Takahashi et al (1989). RESULTS AND DISCUSSION Phosphorylation with STPP Unmodified wheat and corn starches used in this work contained 0.05 and 0.02% P (dwb), respectively, almost all of which occurred as lysophospholipids (Meredith et al 1978, Morrison 1978). Reaction of semidry wheat or corn starch with 5% STPP in the presence of 5% sodium sulfate at pH 6-11 and 1300C for 2 hr gave starch phosphates that contained 0.1-0.3% P (Fig. 1). In STPP phosphorylation, as the initial reaction pH was raised from 6 to 10, the P level in the product decreased gradually, but between pH 10 and 11, phosphorylation decreased rapidly (Fig. 1). At pH 11, corn and wheat starches showed the lowest incorporation of P (0.16 and 0.12%, respectively), which was roughly one half the incorporation at pH 6. Phosphorylation of starch with STPP would be expected to increase further below pH 6.0. However, low pH was not examined because acids catalyze hydrolysis and browning of starch (Kerr and Cleveland 1959). Our data are in conflict with those of Nierle (1969), who found that the degree of phosphorylation of corn starch increased from 0.12% P at pH 7.5 to 0.36% P at pH 9.5 upon reaction with STPP at 1200C for 1 hr. The highest degree of phosphorylation of starch using STPP was obtained at pH 6, where P levels of 0.31 and 0.28% for corn and wheat starch, respectively, were found. After subtraction of the P contributed by lipids (0.02 and 0.05% for corn and wheat, respectively), the corn and wheat starch phosphates prepared at pH 6 contained 0.29 and 0.23% P, respectively, which are equiva-

Characterization of Starch Structures of 17 Maize Endosperm Mutant Genotypes with Oh43 Inbred Line Background.

Abstract: The objectives were to characterise the structure and morphology of starch from 17 maize endosperm mutant genotypes in a common Oh43 inbred background to help in understanding the influences of recessive mutant genes on the maize starches

Modification of Physical and Barrier Properties of Edible Wheat Gluten-Based Films

Abstract: Cereal Chem. 70(4):426-429 Edible films were produced from wheat gluten-based film-forming solutions. One film was produced as a control. Other types came from subjecting control films to three different soaking treatments. Three additional films were also produced by modifying the control film-forming solution. For all films, selected physical properties and permeability to water vapor and oxygen were measured. Comparisons indicated possible ways to improve the control film. All films were good oxygen barriers but limited water vapor barriers. Films containing hydrolyzed keratin had lower oxygen permeability (83%) and lower water vapor permeability (23%). Films containing mineral oil had lower water vapor permeability (25%). Films soaked in calcium chloride solution and in buffer solution at the isoelectric point of wheat gluten had higher tensile strength (47 and 9%, respectively) and lower water vapor permeability (14% and 13%, respectively). Addition of areducing agent increased tensile strength (14%). Soaking in lactic acid solution did not improve the standard film properties. Edible films and coatings formulated from protein, polysaccharide, and lipid substances have been suggested as a means of food protection and preservation. A few examples have already found commercial use: meat casings from collagen (Hood 1987), waxes for fruits and vegetables (Kaplan 1986), and corn zeinbased coatings for nutmeats and candies (Alikonis 1979). Research in the field is active, and the concept is promising for new applications. Kester and Fennema (1986) and Guilbert (1986, 1988) have written technical reviews on edible films and coatings, summarizing past research and offering insights on the film-forming mechanisms. Reviews concentrating on film-forming abilities of wheat, corn, and soy proteins have been published by Gennadios and Weller (1990, 1991). Daniels (1973) reports a number of U.S. patents related to edible films and coatings. Proteins from several plant sources, such as corn, wheat, soybeans. veanuts. and cottonseed. have been studied because of , . their film-forming capabilities. Poor water vapor barrier ability of protein films due to their hydrophilic nature constitutes their main limitation. Film production from wheat gluten, a mixture of proteins accounting for about 80-85% of wheat flour proteins, has also been studied. Wall and Beckwith (1969) and Okamoto (1978) reported important information on the chemistry of the phenomenon, but the resulting films were weak and brittle. Stronger but readily water-soluble films were produced from gluten hydrolysates (Krull and Inglett 1971, Gutfreund and Yamauchi 1974). Anker et a1 (1972) developed a method to produce strong and flexible films by casting heated gluten dispersions. Using this method, Aydt et a1 (1991) and Park and Chinnan (1990) produced wheat gluten films and evaluated several properties. Gennadios et al (1990) adapted the procedure of Aydt et a1 (1991) with minor changes to produce a control wheat gluten film and characterized it by measuring a number of mechanical and barrier properties. The effect on these properties of modifying the film-forming solution was subsequently studied. In the present study, the control wheat gluten film was prepared following the procedure of Gennadios et a1 (1990). Six alternative films were obtained: three by modifying the film-forming solution and three by applying treatments to the control film. A comparative study of all seven types of film was then carried out to measure physical properties (thickness, surface density, tensile strength, h his research was supported by a South Carolina Agricultural Experiment Station Enhancement in Packaging Research Competitive Grant. Technical Contribution 3189 of the South Carolina Agricultural Experiment Station, Clernson University, SC. 'Graduate research assistant and assistant professor, respectively, Department of Biological Systems Engineering, University of Nebraska-Lincoln. Formerly with the Department of Agricultural and Biological Engineering at Clemson University, SC. 'Associate professor, Department of Food Science, Clemson University, SC. @ 1993 American Association of Cereal Chemists, Inc. 426 CEREAL CHEMISTRY and percentage elongation at break) and barrier properties (water vapor and oxygen permeability). MATERIALS AND METHODS Reagents Wheat gluten (DO-PEP) was donated by ADM Arkady, Olathe, KS. Hydrolyzed keratin (CRODA K) was donated by Croda Inc., New York, NY. Glycerol, sodium sulfite, calcium chloride, and calcium nitrate, all of ACS grade, were purchased from Fisher Scientific, Pittsburgh, PA. Buffer solution (pH 7.5) was prepared by using preset pH crystals (TRIZMA, Sigma Chemical Co., St. Louis, MO.). Mineral oil (heavy, USP), lactic acid (USP), lithium chloride (purified), ammonium hydroxide, and ethanol were also purchased from Fisher Scientific. Preparation of Control Film-Forming Solution Film-forming solutions for the control film were prepared using the formula of Gennadios et a1 (1990). The mixture consisted of 15 g of wheat gluten, 72 ml of 95% ethanol, and 6 g of glycerol. The latter was added as a plasticizer. Gluten was dispersed in the solution by heating and stirring for 10 min on a magnetic stirrer-hot plate and slowly adding 48 ml of distilled water and 12 ml of 6N ammonium hydroxide. Heating rate was adjusted so that temperature of the solutions was 75-77OC at the end of preparation time. Preparation of Modified Film-Forming Solutions Film 1 . Heavy mineral oil (3.5 g) was added to the control solution at the beginning of the heating period. Use of mineral oil as a component of food coatings is permitted by the Food and Drug Administration (CFR 1980). Film 2. Sodium sulfite (0.2 g) was added to the control solution at the beginning of the heating period to facilitate dispersion of gluten. Sodium sulfite is a reducing agent with the ability to cleave intramolecular and intermolecular disulfide bonds developed between wheat gluten protein chains (Krull and Wall 1969). Film 3. Of the 15 g of gluten used in the control solution, 2 g (about 13.33%) was replaced by hydrolyzed keratin protein. Treatments on the Control Film Film 4. Control films were soaked in 15% (wlw) lactic acid solutions for 20 sec to introduce a tanning effect on the films. Film 5. Control films were soaked in 1 M aqueous calcium chloride (CaC12) solution for 20 sec and then immediately submerged in distilled water for 10 sec to remove excess solution. This bonded the divalent calcium cations with pairs of negatively charged sites on polypeptide chains, promoting crosslinking in the film structure. Film 6. Control films were soaked for 20 sec in a buffer solution with a pH of 7.5, a value corresponding to the isoelectric point of wheat gluten (Wu and Dimler 1963). Insolubilization of the wheat gluten protein at its isoelectric point was the reason for applying this treatment. Casting of Film-Forming Solutions Upon removal from the hot plate, mixtures were kept at room conditions for 2-3 min to allow bubbling to cease before casting on flat glass plates. Spreading of mixture on the plates was performed with a thin-layer chromatography spreader bar (Brinkman Co., New York, NY). Thick layers of masking tape were attached to the glass plates parallel to the spreader-moving direction, leaving an available casting area of 40 cm X 30 cm. The tape layers restrained movement of cast solutions perpendicular to the casting direction, contributing to efforts for even film-forming solution distribution and control over film thickness. Filmforming solutions for films 1 and 3 were passed through a hand homogenizer (Chase-Logeman, Hicksville, NY) before casting to ensure incorporation of the added substances. Drying of Cast Film-Forming Solutions Glass plates with cast solutions were placed in an air-circulating oven (Isotemp, model 338F, Fisher Scientific) maintained at 32f 2°C. After 15 hr, the plates were removed from the oven, films were peeled off the glass surface, and testing specimens were cut. Drying of Soaked Films Immediately after soaking, specimens from films 4, 5, and 6 were hung by metal clips in the air-circulating oven and left to dry for about 5 hr at 32+2"C. Conditioning Before Tests Before measurements of thickness, surface density, tensile strength, and percentage elongation at break were made, the film was conditioned in a desiccator maintained at 50 f 5% rh and 23f 2OC. The rh was controlled at that level by using a saturated solution of calcium nitrate. Another desiccator, maintained at l l f 5% rh and 23+2OC, was used for film conditioning before measuring water vapor and oxygen gas transmission rates. The rh was controlled by using a saturated solution of lithium chloride. Thickness and Surface Density A hand-held micrometer (B. C. Ames Co., Waltham, MA) was used for measuring film thickness to the nearest 2.54 pm (0.1 mil) from 5-cm X 5-cm samples. For each type of film, four samples were taken from each of four separately cast films. Five micrometer readings were taken from each of these samples, one at the center and four around the perimeter. Therefore, a total of 80 thickness measurements were collected for each film type. These 5-cm X 5-cm samples were also weighed on a balance to the nearest 1 mg. Balance readings were divided by the area of the samples (25 cm2) to calculate surface density. For each type of film, 16 surface density values were obtained. Tensile Strength and Percentage Elongation at Break Film tensile strength and percentage elongation at break were determined using an Instron Universal Testing instrument (model 4201, Instron Engineering, Canton, MA) operated according to the ASTM standard method D 882-88 (ASTM 1989). Initial grip separation and crosshead speed were set at 50 mm and 500 mm/ min, respectively. Peak loads and extension at break point were recorded for tested film specimens (100 mm long and 25.4 mm wide). Tensile strengt

Zein composition in hard and soft endosperm of maize

Abstract: Maize protein composition and distribution may directly influence endosperm texture and physical properties. To test this hypothesis, we compared compositions of alcohol-soluble proteins in maize endosperm from the hard and soft fractions of eight normal genotypes. Kernels were hand-dissected to obtain fractions differing in texture. Endosperm fractions were extracted with a solution containing alcohol, reducing agent, and sodium acetate and were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by reversed-phase high-performance liquid chromatography. We found more (an average of 3.3 times more) alpha-zeins (19 and 22 kDa) in hard endosperm fractions than in soft endosperm fractions, In contrast, soft endosperm fractions contained nearly twice as much 27-kDa gamma-zein (based on percent) than did hard endosperm fractions. Thus, distribution of the various types of zeins was not uniform throughout the maize endosperm. Our results suggest that the zein composition of protein bodies in normal maize kernels may be correlated with texture of the endosperm from which the sample was obtained.

Genotype and environment effects on tocols of Barley and oats

Abstract: Cereal Chem. 70(2):157-162 Grain of 12 oat and 30 barley genotypes, each from three locations, and location. a-Tocotrienol and a-tocopherol were the predominant tocol was analyzed for tocols (tocopherols and tocotrienols) by high- isomers in both species; /3- and y-tocotrienol were also present in sigperformance liquid chromatography with fluorescence detection. The nificant amounts in barley. The major isomers of barley, but not of oats, objective was to assess the variation in levels of tocols among genotypes were generally positively correlated with each other. The data indicate and locations. Significant genotype differences existed for most tocols the feasibility of attempting to increase tocol concentration in these crops in both species. Total tocol concentrations for genotypes ranged from by hybridization and selection. That could lead to food products that 19 to 30 mg kg-' for oats and from 42 to 80 mg kg-' for barley. Location might lower serum low-density-lipoprotein cholesterol, a risk factor for differences were significant for oats but not for barley. Only a small cardiovascular disease. percentage of the variance was associated with the interaction of genotype Vitamin E activity results from the complex of tocols found in various foodstuffs. Tocols include tocopherols and tocotrienols, the difference being a saturated side-chain in tocopherols and a triunsaturated side-chain in tocotrienols. Each class of tocols consists of at least four isomers, differing in the number and position of methyl substituents on the benzene ring (Pennock et al 1964). Many biological activities of vitamin E are believed to result from its antioxidant action, specifically the inhibition of lipid peroxidation in biological membranes (Burton and Traber 1990). Although a-tocopherol is considered to have the greatest biological activity (Taylor and Barnes 1981), recent evidence suggests that a-tocotrienol may have 40-60 times higher antioxidant

Direct colorimetric assay of free thiol groups and disulfide bonds in suspensions of solubilized and particulate cereal proteins

Abstract: A direct colorimetric method that simultaneously combines measurement of solubilized and insoluble thiol groups and disulfide bonds in corn meal-based materials is described. Ellman's reagent, 5,5'-dithiobis (2-nitrobenzoic acid), which reacts specifically with thiol groups, or disodium 2-nitro-5-thiosulfobenzoate, which reacts with cysteine and thiol groups formed after reduction of disulfide bonds with sodium sulfite, were reacted directly with corn meal in the presence of surfactants (urea and/or sodium dodecyl sulfate), releasing the soluble chromophore 2-nitro-5-thiobenzoate. After a clarification step to remove suspended material, absorbance at 412 nm was read. This assay was highly reproducible, and measurements agreed with direct amino acid analysis. Twin-screw extrusion of corn meal at 150 degrees C at moisture levels of 16 and 18% had no significant effect on cysteine or disulfide bond levels. Other possible changes such as disulfide bond rearrangements could not be determined by the mixed-phase assay. This method provides a rapid and convenient means for screening thiol and disulfide levels in insoluble proteinaceous materials

Distribution of Polyphenol Oxidase in Flour Millstreams of Canadian Common Wheat Classes Milled to Three Extraction Rates

Abstract: CONCLUSIONS The availability of an assay kit for the determination of starch damage in flour offers a convenient and simple alternative to the current standard methods. Starch damage determinations with the assay kit are highly correlated to those of the standard methods, but the kit procedure is standardized and more rapid. With the kit procedure, 40 samples can be analyzed in 2 hr. The kit is therefore applicable for use in situations where there are large sample numbers, such as in the monitoring of millstream runs and in wheat breeding programs. The starch damage assay kit is now available commercially from MegaZyme (Aust) Pty Ltd. ACKNOWLEDGMENTS We thank all of the laboratories that participated in the collaborative evaluation of the starch damage assay kit. We also thank J. R. Donelson of the U.S. Department of Agriculture Agricultural Research Station Soft Wheat Quality Laboratory, Wooster, for the provision of starch damage results by the AACC and Wooster methods and A. Evers of the Flour Millers and Bakers Research Association, Charleywood, for distributing the assay kits to collaborators in the UK. We also thank Malcolm Glennie-Holmes, Bill Barnes, David Mugford, and Arthur Gilmour for their comments on the manuscript. This research was funded in part by the Grains Research Development Corporation of Australia.

Location of phosphate esters in a wheat starch phosphate by 31 P-nuclear magnetic resonance spectroscopy.

Abstract: Cereal Chem. 70(2):145-152 Phosphate esters of D-glucose, methyl c-D-glucopyranoside, and on potato starch were confirmed to be the 6and 3-esters. The wheat maltose, as well as the a,,y-limit phosphodextrins from native potato starch phosphate, prepared by heating starch with sodium tripolystarch (degree of substitution [DS] 0.0033) and phosphorylated amylose phosphate under semidry conditions at an initial pH of 6, contained mainly (DS 0.016) served as model compounds in 3 P-nuclear magnetic resonance 6-monophosphate esters along with lower levels of 3and probably experiments to locate the phosphate groups on a phosphorylated wheat 2-monophosphates. The wheat starch phosphate contained orthophosstarch (DS 0.012). The a,,y-limit phosphodextrins were isolated by ionphate groups at the nonreducing ends of starch molecules, whereas exchange chromatography after exhaustive digestion of amylose or starch endogenous phosphate esters in potato starch occur on inner anhydrophosphates with Bacillus amyloliquifaciens a-amylase followed by glucose units. Aspergillus niger glucoamylase. The endogenous orthophosphate groups The phosphate ester groups on potato starch contribute to its high clarity and viscosity when it is cooked to a paste. Phosphorylation of wheat and corn starches increased paste clarity and consistency, but potato starch remained superior in those properties in spite of the fourfold higher level of phosphate esters on the modified wheat and corn starches and their low level of cross-linking (Lim and Seib, 1993). The location of endogenous phosphate esters on potato starch apparently differs from that on chemically phosphorylated starches. Gramera et al (1966) prepared corn starch phosphate with a degree of substitution (DS) of 0.016 (0.3% phosphorus [P]) by reacting corn starch at 150° C with sodium tripolyphosphate under unspecified conditions. The starch phosphate was subjected to Smith degradation followed by mild acid hydrolysis and anionexchange chromatography to give three main fractions. The components in the main fractions were investigated using paper chromatography, periodate analysis, and optical rotation. The results indicated that 6-, 2-, and 3-phosphates made up 63, 28, and 9% of the fractions, respectively. The location of phosphate esters on native potato starch has been examined extensively over the past 20 years by Hizukuri and his colleagues. Of the total P on potato starch (0.036-0.092%, or 1 atom of P per 209-532 anhydroglucose units [AGUs]), practically all was found on the amylopectin fraction (Abe et al 1982), with two thirds occurring as 6-phosphate, one third as 3-phosphate, and a trace as 2-phosphate (Hizukuri et al 1970, Tabata and Hizukuri 1971). The phosphate esters were not found on the nonreducing terminus of the a-1,4-linked unit chains in potato amylopectin (Tabata et al 1978), and 88% or more were on Bchains (Takeda and Hizukuri 1982). The phosphate esters were located a minimum of 9 AGUs inward from a branch point (Takeda and Hizukuri 1982). Glucoamylase that was free of both a-amylase and phosphatase was unable to bypass phosphorylated AGUs in potato starch (Abe et al 1982). Exhaustive digestion of a potato starch, which contained 1 P per 209 AGU, with glucoamylase gave 17% y-limit dextrin with 1 P per 36 AGU and an average unit-chain length of 14. The 'y-limit dextrin was of high molecular weight, as indicated by its high viscosity in water. Since the P in potato starch was concentrated in the 17% -y-limit dextrin, Abe et al (1982) concluded that either a few amylopectin molecules are highly phosphorylated or that phosphate groups are concentrated locally as a structural feature of the potato starch granule. 'Contribution 92-355-J from the Kansas Agricultural Experiment Station, Manhattan 66502. 2 Research associate, Department of Food Science and Human Nutrition, Iowa State University, Ames 50011. 3 Professor, Department of Grain Science and Industry, Kansas State University, Manhattan 66506. © 1993 American Association of Cereal Chemists, Inc. Recently, Muhrbeck and Tellier (1991) measured the 3 Pnuclear magnetic resonance (NMR) spectra of eight samples of potato starch dissolved in methyl sulfoxide. As the total-P level increased from 0.0153 to 0.0221% of amylopectin, the level of 3-P remained relatively constant (from 0.0044 to 0.0063%), whereas the 6-P level increased (from 0.0 104 to 0.0 165%). Furthermore, the crystallinity and enthalpy of gelatinization decreased with the level of 6-phosphorylation, but not with the level of 3-phosphorylation (Muhrbeck et al 1991). In this work, we used P-NMR spectroscopy on model P compounds to explore the position of phosphorylation on a wheat starch phosphate. MATERIALS AND METHODS Materials All chemicals were reagent grade unless otherwise stated. Potato starch (0.063% P), potato amylopectin, methyl a-D-glucopyranoside (MG), D-glucose, and D-glucose 6-phosphate were purchased from Sigma Chemical Co. (St. Louis, MO). Potato amylose, diphenyl phosphorochloridate, and platinum oxide were from Aldrich Chemical Company, Inc. (Milwaukee, WI). Wheat starch was Midsol 50 provided by Midwest Grain Products Co. (Atchison, KS). Crystalline Bacillus amyloliquifaciens a-amylase (Type IIA), a solution of Aspergillus niger glucoamylase with glucose and preservative, and bovine intestinal alkaline phosphatase (Type I-S) were from Sigma Chemical Co. The enzyme activity was 930 units [U]/mg for a-amylase, 6,100 U/ml for glucoamylase, and 6.8 U/mg for phosphatase. One unit of a-amylase liberated 1 mg of maltose from starch in 3 min (1.0 ,umol/min) at pH 6.9 and 200C; 1 U of glucoamylase released 1 mg of glucose from starch in 3 min (1.9 ,umol/min) at pH 4.5 and 55°C; and 1 U of phosphatase hydrolyzed 1 ,umol/min of p-nitrophenol phosphate at pH 10.4 and 370C. The a-amylase and glucoamylase were found to have no phosphatase activity according to the following methods. D-Glucose 6-phosphate (0.1 g) was mixed with 0.01M acetate buffer (pH 4.5, 6 ml) and glucoamylase (0.1 ml). After 1 hr at 400C, the mixture was adjusted to pH 8, and its P-NMR spectrum was examined. No increase was observed in the intensity of the signal for orthophosphate. It was estimated that 5% hydrolysis of D-glucose 6-phosphate would increase the orthophosphate concentration by 3 mM so that the orthophosphate would be readily detectable. a-Amylase (1 mg) was added to a solution of D-glucose 6-phosphate in water at pH 6-7. After digestion for 1 hr at 700C, the mixture was adjusted to pH 8.0, and its 3 1 P-NMR spectrum was examined. The spectrum showed no increase in the intensity of the orthophosphate signal. The commercial glucoamylase solution was found to contain a trace of inorganic phosphate. Vol. 70, No. 2,1993 145 General Methods Total carbohydrate was measured by the phenol-sulfuric acid method (Dubois et al 1956) and reducing end groups by the modified Park-Johnson method (Hizukuri et al 1981), using D-glucose as the reference standard. Phosphorus in starch and dextrins was measured by the method of Smith and Caruso (1964). NMR spectra were recorded on a Bruker WM400 NMR spectrometer (Bruker Instruments, Inc., Billerica, MA). 3 P-NMR spectra were measured at 162 MHz on aqueous solutions at pH 8.0 ±0.1; the solutions contained 0.02M ethylenediaminetetraacetate to sharpen the signals. Chemical shifts are reported in parts per million from orthophosphate (sodium salt) as internal reference standard. ' C and H-NMR spectra were recorded at 100.6 and 400 MHz, respectively, in CDC13 or D20 solution, and chemical shifts (6) are reported (in ppm) from tetramethylsilane (6 0.0 ppm). Methanol (49.6 ppm) was used as the internal reference for 'C-NMR spectra. Phosphorylation of Amylose and Wheat Starch Wheat starch was phosphorylated at an initial pH of 6 using 5% sodium tripolyphosphate (STPP) in the presence of 5% sodium sulfate as described by Lim and Seib (1993). The P content of the modified wheat starch (0.28%) was corrected for endogenous P in its associated lipids (0.05%). The net 0.23% phosphorus was equivalent to DS 0.012. Potato amylose was phosphorylated as follows. Amylose (5 g) was dissolved in 0.3M sodium hydroxide (200 ml), and STPP (0.5 g) was added, followed by 2M hydrochloric acid to bring the mixture to pH 7. Ethanol (1,200 ml) was added slowly with stirring, and the mixture was kept at 4 C overnight. The precipitate was collected by centrifugation and vacuum-dried at room temperature over calcium sulfate until its moisture level was below 10%. The amylose-STPP mixture was heated at 130'C for 3 hr; then the phosphorylated amylose was separated from contaminating salts by dialysis. The retained material was isolated by precipitation with ethanol and dried in a vacuum desiccator. The yield of amylose phosphate, which contained 0.30% P (DS 0.016), was 3.1 g. D-Glucose 2and 3-Phosphates and Methyl a-D-Glucopyranoside 2and 6-Phosphates D-Glucose 2and 3-phosphates were prepared according to Farrar (1949) and Brown et al (1957), respectively. The esters were converted to their cyclohexylammonium salts using a strongly acidic cation-exchange resin in the cyclohexylammonium form. The cyclohexylammonium salt of a-D-gluCopyranose 3-phosphate (mp 1310C) crystallized from ethanol, whereas the 2-phosphate remained a syrup. Methyl 4,6-O-benzylidene-a-D-glucopyranoside (1 g, mp 168-170'C) (Fletcher 1963) was reacted at 0 C with diphenyl phosphorochloridate (1.2 equivalents) in dry pyridine (2 ml) (Ballou and MacDonald 1963). After 2 hr, water (0.05 ml) was added, and the mixture was evaporated to a syrup. The syrup was dissolved in chloroform (50 ml), and the organic layer was washed repeatedly with water. Vacuum evaporation of the chloroform solution gave syrupy diphenylphosphate ester, from which the last traces of pyridine were removed by high vacuum at 250 C. The phenyl and 4,6-acetal blocking groups were removed by hydrogenation over platinum oxide (0.05 g) at 1 atm

Cooked pasta texture : comparison of dynamic viscoelastic properties to instrumental assessment of firmness

Abstract: Cereal Chem. 70(2):122-126 Extruded noodles were prepared from durum wheat semolina of variable ness. The Instron peak force measurement was found to be a more precise protein content to provide a series of samples with a range of cooking indicator of noodle firmness than was peak energy. The rheometer was quality. Firmness of cooked extruded noodles was measured using an able to differentiate between samples and to rank the noodle samples Instron Universal Testing Machine and compared with the storage in the same order as the Instron did. Although moisture content was modulus and dynamic viscosity obtained by dynamic rheometry. A strong shown to have a major influence on the texture of cooked noodles, the correlation (r at least 0.87) was found between the Instron values and differences in moisture between samples were not sufficient to produce the rheometer measurements at both optimum and overcooking times, the differences measured by either the Instron or by dynamic rheometry. indicating the sensitivity of dynamic rheometry to changes in pasta firmIt is generally accepted that texture is the main criterion for assessing overall quality of cooked pasta. Proper evaluation of pasta cooking quality requires consideration of a number of factors including elasticity, firmness, surface stickiness, cooking tolerance, water absorption, and loss of solids to cooking water (Manser 1981). Taste panels can be used to estimate pasta cooking quality (Menger 1979), but they are time-consuming and impractical when sample size is limited or large numbers of samples are to be evaluated. In response to these constraints, a number of instrumental methods have been developed that successfully estimate cooked pasta texture parameters (Matsuo and Irvine 1969, 1971; Walsh 1971; Voisey and Larmond 1973; Feillet et al 1977; Voisey et al 1978). Furthermore, a chemical test was developed by D'Egidio and co-workers (1982) that related sensory evaluation of spaghetti glueyness, bulkiness, and firmness to the amount of total organic matter rinsed from the surface of cooked spaghetti. The use of the Instron Universal Testing Machine (Instron, Canton, MA) is well established for the measurement of pasta firmness (Walsh 1971, Oh et al 1983). It is the instrument recommended by AACC (1983) in approved method 16-50. Like most instrumental tests used to evaluate pasta quality, it involves large deformation measurements on the samples tested. There has been growing interest in the use of dynamic mechanical tests employing controlled strain and stress to study the fundamental rheological properties of dough (Navickis et al 1982, Abdelrahman and Spies 1986, Dreese et al 1988). These methods are applicable to polymeric materials, such as cooked pasta, displaying viscoelastic behavior. Therefore, it seemed reasonable to use dynamic rheometry to study the viscoelastic properties of cooked pasta and to determine the relationship with Instron firmness values. MATERIALS AND METHODS Samples Samples of No. 1 Canada Western Amber Durum (CWAD) and No. 2 CWAD collected for the 1989 Grain Research Laboratory harvest survey were composited according to protein content to give eight composites with a 11.2-18.5% range in protein content. 'Contribution No. 690 of Canadian Grain Commission, Grain Research Laboratory, Winnipeg, MB. 2 University of Manitoba, Food Science Department, Winnipeg, Canada. Milling Wheats were cleaned and tempered overnight to 16.5% moisture and milled in single 3-kg lots with a four-stand Allis-Chalmers laboratory mill (Allis-Chalmers, Milwaukee, WI) in conjunction with a laboratory purifier (Black 1966) using the procedure of Dexter et al (1990). The millroom is controlled for temperature (21 C) and rh (60%). Semolina yield range was 61.2-64.5% of clean wheat on a constant moisture basis. Pasta Processing Noodles were processed using a Demaco semicommercial laboratory press (De Francisi Machine Co., Brooklyn, NY) under extrusion conditions previously described (Matsuo et al 1978). The extruded rectangular pasta products, referred to as noodles throughout this article, presented a flat, even upper and lower surface to the plate geometry of the dynamic rheometer. When placed side by side, spaghetti or other round pasta products have \"valleys\" between the strands that can trap water, affecting the rheometry results. Thick and thin noodles were made using dies (Maldari and Sons, Brooklyn, NY) with 1.5 X 20-mm and 0.8 X 20-mm apertures, respectively. Noodles were dried in the 390 C cycle described by Dexter et al (1981). Noodle Firmness Cooked noodle firmness was determined as peak force and peak energy with an Instron Universal Testing Machine (model 4201, Instron Corp., Canton, MA) equipped with a 10-kg load cell. Samples were tested in triplicate in completely randomized design. The method used was a modification of AACC (1983) method 16-50. Noodles were cooked to optimum time, defined as when the white core in the center of the noodle disappeared (7 min for the thin and 25 min for the thick noodles), or were overcooked (19 min for the thin and 45 min for the thick noodles). Ten noodle strands, each about 5 cm long, were cooked in 800 ml of boiling tap water for the prescribed time and were immediately drained over a U.S. no. 14 wire sieve. Once drained, the strands were transferred to cold water for 1 min to arrest the cooking process. The samples were drained again over the wire sieve and transferred to a covered container to prevent drying. Two strands were removed from the container for testing. Excess moisture was removed from the surface by lightly patting the strands between layers of paper towel. They were then placed side by side on an aluminum base plate perpendicular to and centered under a cutting blade similar to that described by Oh et al (1983). The crosshead speed was set at 50 mm/min. The lower limit was 0.5 mm from the base for the thick noodles and 0.1 mm for the thin noodles. For each cooking, four pairs of noodles were sheared in two places, giving a total of eight measurements per replicate. Cooked Noodle Weight, Cooking Loss, and Moisture Content Noodle cooked weights and cooking losses were determined This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. American Association of Cereal Chemists, Inc., 1993. 122 CEREAL CHEMISTRY in duplicate at each cooking time. Ten grams of noodles (12% mb) were cooked for the desired time in 250 ml of boiling tap water. The noodles were drained, cooled in water, drained again, patted dry as described earlier, and weighed immediately. Cooking water was retained and cooking loss determined as described by Dexter and Matsuo (1979). The cooked weight and cooking loss (to account for the lost dry matter) were used to calculate the moisture content of the cooked noodles. Dynamic Rheometry The dynamic viscoelastic properties of the cooked noodles were measured in triplicate in a completely randomized design using a Bohlin VOR rheometer (Bohlin Reologi, Edison, NJ) operated with a parallel-plate geometry of 15 mm diameter and a torque element of 93.2 g-cm. Measurements were taken at 250C in a 0.1to 10.0-Hz frequency range and below 1.0% strain. Noodles were prepared as described for firmness testing. Once the noodles were patted dry, a 15-mm disk was cut to fit the plate geometry of the rheometer. Three strands were used per cooking, with one disk removed from each strand. The disks were slightly compressed to approximately 1% of sample thickness and allowed to relax for 40 sec before measurements were taken. The dynamic rheological parameters were storage modulus (G'), loss modulus (G\"), loss tangent (tan 6 = G\"/ G), and dynamic viscosity (n'). These parameters were obtained using the software analysis program of the rheometer. The rheometer analysis program takes into account the thickness of the sample disk in calculating the various parameters, offsetting differences due to varying degrees of swelling during cooking. A 1-Hz frequency was used for all statistical comparisons. G' provides a measure of the energy stored and recovered in the sample upon sinusoidal deformation. It is generally taken as an indicator of the elastic character of the sample. Energy dissipated or lost as heat per deformation cycle, or G\", is a measure of the sample viscosity; tan 6 indicates the relative contribution of the viscous and elastic components; n' normalizes the G\" for the changes in oscillation frequency and is calculated as G\"/27rf, wherefis frequency. Faubion et al (1985) provide a good description of the instrumentation and the principles involved in dynamic rheometry of doughs. Application of dynamic rheometry to starch gel network characterization has recently been reviewed by Biliaderis (1992). al 1986, D'Egidio et al 1990). Therefore, in preliminary experiments, the three durum wheat semolina samples representing the lowest, intermediate, and highest protein content were processed into thick (1.5 mm) noodles to verify that intrinsic differences in cooking quality were present among samples. The cooking quality range was extended further by measuring the texture of each sample at two cooking times. Analysis of variance of Instron results confirmed highly significant differences (P < 0.01) attributable to samples and cooking times (Table I) whether firmness was measured by peak force or by peak energy. Peak force, however, was the more precise of the two measurements as reflected by a coefficient of variation of 5.7% compared with 9.9% for peak energy. The Bohlin rheometer was used to determine whether the G' and n' of cooked noodles were related to Instron firmness results. The samples were first tested over a range of strains to determine appropriate conditions for rheological testing. Below 1.0% strain, the samples exhibited linear or nearly linear viscoelastic response (Fig. 1). Typical mechanical spectra of optimally

Extraction and enrichment of (1→3), (1→4)-β-D-glucan from barley and oat brans

Abstract: Cereal Chem. 70(l):77-80 Soft white wheat flours from varied growing conditions were analyzed However, when the correction for protein content was not taken into for selected variables of gluten and components of flour lipid to identify account, total protein was shown to be negatively correlated with cookie those that are associated with baking quality as measured by cookie diameter. Among the components of flour lipid, polar lipid had the highest diameter and cake volume. Statistical analysis indicated that among the correlation with cake volume. These variables, therefore, appear to be gluten variables, yield of gluten and pentosan in gluten were the variables important in the end-use quality of soft white wheat. most associated with cookie diameter corrected for protein content. Soft wheat flours with low protein content are used for pastry products rather than for breadmaking, where hard wheat flour with higher protein content is used (Hoseney et al 1988). However, the protein content is not the only factor determining end-use properties. Protein quality can influence the baking properties of both hard wheat flour (Orth and Bushuk 1972) and soft white wheat flour (Kaldy and Rubenthaler 1987). An important factor in protein quality is the gluten characteristics of a dough. Gluten is formed by the interactions of the proteins, glutenin and gliadin, which also associate with lipid and pentosans during dough formation (D'Appolonia and Kim 1976, Hoseney 1986). A strong dough with an extensive gluten network is suitable for breadmaking (Pomeranz 1988). In contrast, a weak dough, without an extensive gluten network, is best for cookies and cakes (Gaines 1990). Consequently, flour quality is influenced by the nature of the gluten and its various components. However, very little is known about gluten and its components in soft white wheat flour, especially with reference to baking quality. Pentosans also have an influence on flour quality and dough formation (Yamazaki 1955, Shogren et al 1987). Native flour pentosans were found to have a negative effect on both cookie diameter and cake volume (Kaldy et al 1991). Some pentosans are part of the gluten matrix, but the exact nature of the association with the matrix is unknown. Also, the influence of the glutenassociated pentosans on baking quality of soft white wheat flour has not been established. Flour lipids also influence the baking quality of soft white wheat flour. Cookies baked from flours with the lipids removed had smaller diameters than those baked from unextracted flours (Cole 'Contribution 3879067 of the Lethbridge Research Station. 2 Agriculture Canada, Research Station, Lethbridge, Alberta T I J 4B 1. 3 Retired. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. American Association of Cereal Chemists, Inc., 1993. et al 1960). Studies on cake quality have also indicated that removal of lipids reduces cake volume (Seguchi and Matsuki 1977). As far as lipid fractions are concerned, nonpolar and polar lipids in spring wheat flour have been shown to have an influence on loaf volume (Bekes et al 1986). Both nonpolar and polar lipids were found to be necessary for the restoration of cookie spread in defatted flour from a cultivar of eastern soft white wheat (Kissell et al 1971). The purpose of this study was to examine gluten and lipid components in flours from soft white wheat grown under a broad range of conditions and to identify the gluten and lipid variables most associated with baking quality. MATERIALS AND METHODS Soft white wheat samples were collected from a broad range of growing environments in Alberta and Ontario, Canada, and in Washington State. Fifteen samples of soft white spring wheat were from a 500-km-wide region of Alberta. Ten samples were cv. Fielder, one was cv. Owens, one was cv. Dirkwin, and the remaining three samples were mixed (commercial) spring wheat cultivars, mainly Fielder and Owens. All were grown in 1984 except one Fielder sample, which was grown in 1983. Of khe five samples from Washington State, four were Fielder. One was grown in 1981, another in 1982, and two samples in 1983. The other sample was Owens, grown in 1984. Three of the five winter wheat samples from Ontario were the cultivar Fredrick, grown in 1982, 1983, and 1984. The two other samples were mixed (commercial) cultivars grown in 1984. All samples were milled on a Buhler pneumatic laboratory mill at the USDA Western Wheat Quality Laboratory, Pullman, WA, as described previously (Kaldy and Rubenthaler 1987). Cookie and cake baking, as well as some of the other tests, were also done at the Western Wheat Quality Laboratory as described previously (Kaldy and Rubenthaler 1987). The samples were stored under refrigeration. Some of the carbohydrates in flour were analyzed as previously described (Kaldy et al 1991). As reported previously (Kaldy and Rubenthaler 1987, Kaldy Vol. 70, No. 1, 1993 77

Effects of hydrocolloids on processing and qualities of wheat tortillas

Abstract: Effects of hydrocolloids were evaluated in hot-press wheat tortillas. Natural (arabic, guar, and xanthan), modified cellulose (carboxymethylcellulose [CMC], hydroxypropyl methylcellulose, and methylcellulose), and commercial blends (mixtures of natural and modified cellulose gums) were utilized. Farinograph values, mixing characteristics, dough machinability, tortilla characteristics (diameter, weight, moisture content, and appearance), rollability over time, and freeze-thaw stability were determined. Increased levels of gums resulted in doughs that were more sticky and less cohesive throughout mixing. Doughs prepared with commercial blends containing cellulose gum exhibited characteristics similar to CMC, such as lower initial dough viscosity and longer dough development times compared with those of the control. Hot-press wheat tortillas containing natural gums, modified cellulose gums, or commercial blends were consistently round, puffed, slightly browned, and of good quality. Tortilla diameters (159 mm), weights (41.4 g), and moisture content (30.8%) were similar for all tortillas. Water absorption of dough increased when more gums were added. The rollability of tortillas was retained longer with CMC and cellulose-based commercial blends. Rollability of all tortillas decreased during freezing and thawing, and tortillas containing CMC were significantly more rollable than control tortillas after five freeze-thaw cycles. Proper gluten development appears to be essential for good dough machinability, tortilla qualities, and tortilla shelf stability