Typescript. / Digitized by Kansas Correctional Industries

The synthesis of high molecular weight (HMW) glutenin, low molecular weight glutenin and gliadin proteins are controlled by nine major loci present in wheat chromosomes. The loci Glu A1, Glu B1, Glu D1 and Gli A1, Gli B1, Gli D1 and Gli 2 and their allelic variants play important roles in determining the functional properties of wheat flour. This study focused on understanding the functionality of these protein subunits with respect to tortilla quality for use in developing varieties with ideal tortilla baking quality. Near-isogenic wheat lines in which one or more of these loci were absent or deleted were used in the study. These lines were analyzed using SSR primers to verify the chromosome deletions. A standard SDS PAGE gel and a Lab on Chip Capillary Electrophoresis method were used to confirm the protein composition of the deletion lines. Tortillas were prepared from each deletion line and the parent lines used to derive the deletion lines, and tortilla quality evaluations were analyzed. The analysis has revealed that elimination of certain HMW glutenins results in gain of function both for tortilla diameters and overall tortilla quality. The deletion line possessing 17+18 at Glu B1 and deletions in Glu A1 and Glu D1 had a gain of function in tortilla diameter, yet tortilla stability was compromised. The deletion line possessing Glu A1, Glu D1 (1,5+10) and a deletion in Glu B1 improved both the diameters and stability of the tortillas. Presence of subunits 5+10 is important for maintaining tortilla stability. Deletions in gliadin monomeric proteins also affected the tortilla diameters and stability.

The synthesis of high molecular weight (HMW) glutenin, low molecular weight glutenin and gliadin proteins are controlled by nine major loci present in wheat chromosomes. The loci Glu A1, Glu B1, Glu D1 and Gli A1, Gli B1, Gli D1 and Gli 2 and their allelic variants play important roles in determining the functional properties of wheat flour. This study focused on understanding the functionality of these protein subunits with respect to tortilla quality for use in developing varieties with ideal tortilla baking quality. Near-isogenic wheat lines in which one or more of these loci were absent or deleted were used in the study. These lines were analyzed using SSR primers to verify the chromosome deletions. A standard SDS PAGE gel and a Lab on Chip Capillary Electrophoresis method were used to confirm the protein composition of the deletion lines. Tortillas were prepared from each deletion line and the parent lines used to derive the deletion lines, and tortilla quality evaluations were analyzed. The analysis has revealed that elimination of certain HMW glutenins results in gain of function both for tortilla diameters and overall tortilla quality. The deletion line possessing 17+18 at Glu B1 and deletions in Glu A1 and Glu D1 had a gain of function in tortilla diameter, yet tortilla stability was compromised. The deletion line possessing Glu A1, Glu D1 (1,5+10) and a deletion in Glu B1 improved both the diameters and stability of the tortillas. Presence of subunits 5+10 is important for maintaining tortilla stability. Deletions in gliadin monomeric proteins also affected the tortilla diameters and stability.

The effects of sorghum bran addition on table tortillas and tortilla chip properties were evaluated. Texture, phenol content, antioxidant activity, and sensory characteristics were evaluated. Texture was measured by objective and subjective tests. Products were analyzed for phenols following the Folin-Ciocalteu procedure and for antioxidant potential following the ABTS (2,2'-azinobis (3- ethylbenzothiazoline-6-sulfonic acid) method. Sensory properties were evaluated using a nine point hedonic scale. Bran from two specialty sorghums: sumac (high tannin) and black (high anthocyanins) was added at 0, 5, and 10% to table tortillas and tortilla chips. For table tortillas the interaction of sorghum bran with an antistaling formula containing guar gum, carboxymethylcellulose and maltogenic alpha-amylase was assessed. Tortillas containing sorghum bran had a more friable structure than the control. This detrimental effect was overcome by the antistaling formula. Additives made fluffier tortillas with improved texture and appearance. Tortillas containing sorghum bran and the antistaling formula were acceptable to panelists. At 5% sorghum bran inclusion, there was no significant difference in sensory attributes from the control aside from appearance. Tortillas containing sorghum bran had a dark natural color comparable to that of blue corn tortillas. Tortilla chip texture was not significantly affected by addition of bran to the formula. As in table tortillas, addition of sorghum bran produced minor changes in the texture and flavor of the product, but a significant change in appearance acceptability. Tortilla chips had a dark color, comparable to the one of blue corn tortilla chips. Sumac bran yielded larger amounts of phenols and antioxidant activity than black bran. Levels of phenols and antioxidant potential increased with increased bran. Although processing caused a measurable loss of sorghum bran antioxidants, table tortilla and tortilla chips were still a significant source of phenols and antioxidant activity. The addition of sorghum bran produced tortillas and tortilla chips with increased levels of dietary fiber and antioxidants, without adversely affecting other sensory properties.

Thesis (M.S.)--Rutgers University, 2008. / "Graduate Program in Food Science." Includes bibliographical references (p. 134-136).

Absorption of iron from foods has been reported to be inhibited by various factors including some diet components. Fiber from different sources has been observed to bind ferrous iron. This may be the reason for iron deficiencies observed in populations that consume diets high in non-digestible materials. The effect of different levels of fiber from corn tortillas and cooked beans on iron availability in the rat was studied. Iron-depleted rats were fed test diets containing different levels of iron and fiber and the diets were tested for their hemoglobin repletion ability. Estimation of the neutral detergent fiber (NDF) in corn tortillas and cooked beans and the soluble and ionizable iron in the test foods and diets were also determined. Corn tortillas contained 6.53% NDF. Raw beans contained 5.80% NDF and increase to 15.75% upon cooking. In cooked beans, 60.16% of the total iron is in the insoluble form while only 20.3% of the total iron in corn tortillas is insoluble. The mean relative biological value (RBV) for the test diets was 55.0 ± 19.0% with values ranging,from 40.41 ± 12.50% to 64.34 ± 11.10% compared to that of ferrous sulfate (100% available). Fiber or iron level had no significant effect on iron availability, however, a ratio of 1.78 of corn tortilla to cooked beans showed the highest degree of iron availability. Percent efficiency of the test diets to incorporate iron into hemoglobin ranged from 11.70 ± 1.4% for a diet containing 25 ppm iron and 15% NDF to 25.61 ± 6.10% for 35 ppm iron, 10% NDF diet. The control diet containing 30 ppm ferrous sulfate had a 43.0 ± 8.7% efficiency. Percent efficiency seems to show less variability in the determination of iron availability from foods than RBV. A significant correlation (p < 0.01) between soluble iron at pH 1.35 in vitro and percent efficiency was observed. This method could be used to predict iron availability for different foods. / Graduation date: 1982

The texture of tortillas was improved by the addition of maltogenic amylase and carboxymethylcellulose (CMC) and guar gum to fresh masa from ground nixtamal (FNM) and nixtamalized corn flour (NCF) masa. Differences in the performance of additives in tortillas held under refrigeration or ambient storage were documented. For NCF tortillas, significant improvements were obtained in objective and subjective texture measurements by two treatments. Tortilla texture was improved by a treatment with a high enzyme level (170 mg/kg of maltogenic α-amylase, 0.14% CMC, 0.85% guar) as measured by objective tests and by a treatment with low enzyme level (60 mg/kg of maltogenic α-amylase, 0.43% CMC, 0.57% guar) as measured by subjective tests. The addition of maltogenic α-amylase (70 mg/kg) and CMC (0.35%) to FNM tortillas at levels similar to the low enzyme NCF treatment but with lower guar level (0.12%) improved tortilla texture. The maltogenic α-amylase softened tortillas by trimming the starch structure. This allowed the guar to interfere with amylopectin re-crystallization inside gelatinized starch granules. The CMC created a more flexible intergranular matrix that helped maintain the disrupted tortilla structure. Guar was ineffective in refrigerated tortillas, whereas, maltodextrins effectively improved refrigerated tortillas. The sequence of partial starch hydrolysis, warm holding condition, and time for guar to associate with starch and CMC was necessary to improve tortilla texture. Thus, different additives may be required for cold versus room temperature storage. Sugars increased in enzyme-treated tortillas during storage. This suggests that maltogenic α-amylase was only partially inactivated during baking of corn tortillas. Tortillas with more enzyme had lower and later pasting viscosity as measured by a Rapid Viscoanalyzer. Tortillas prepared from FNM also had lower and later pasting viscosity compared to NCF tortillas. Pasting viscosity of tortillas revealed intrinsic starch polymer characteristics and interactions. Results of this study provide commercially applicable information about desired levels for the extent of starch hydrolysis, the type and amount of gums and starches, and product microstructure to delay staling of corn tortillas.

A cost-effective, faster and efficient way of screening wheat samples suitable for tortilla production is needed. Hence, we developed prediction models for tortilla quality (diameter, specific volume, color and texture parameters) using grain, flour and dough properties of 16 wheat flours. The prediction models were developed using stepwise multiple regression. Dough rheological tests had higher correlations with tortilla quality than grain and flour chemical tests. Dough resistance to extension was correlated best with tortilla quality, particularly tortilla diameter (r= -0.87, P<0.01). Gluten index was significantly correlated with tortilla diameter (r = -0.67, P less than 0.01) and specific volume (r = -0.73, P less than 0.01). Tortilla diameter was the parameter best predicted. An r2 of 0.87 was obtained when mix-time and dough resistance to extension were entered into the model. This model was validated using another sample set, and an r^2 of 0.91 was obtained. Refined and whole wheat flours, dough and tortillas were compared using five wheat samples. Refined flour doughs were more extensible and softer than whole wheat flour doughs. Whole wheat flour tortillas were larger, thinner and less opaque than refined flour tortillas. Refined wheat flour had much smaller particle size and less fiber than whole wheat flour. These are the major factors that contributed to the observed differences. In general, refined wheat tortillas were more shelf-stable than whole wheat tortillas. However, whole wheat tortillas from strong flours had excellent shelf-stability which must be considered when whole wheat tortillas are processed. . Different objective rheological techniques were used to characterize the texture of refined and whole flour tortillas during storage. Differences in texture between 0, 1 and 4 day-old tortillas were detected by rupture distance from one and two-dimension extensibility techniques. In general, the deformation modulus was not a good parameter to differentiate tortilla texture at the beginning of storage. It detected textural changes of 8 and 14 day-old tortillas. The subjective rollability method detected textural changes after 4 days storage.

The texture of tortillas was improved by the addition of maltogenic amylase and carboxymethylcellulose (CMC) and guar gum to fresh masa from ground nixtamal (FNM) and nixtamalized corn flour (NCF) masa. Differences in the performance of additives in tortillas held under refrigeration or ambient storage were documented. For NCF tortillas, significant improvements were obtained in objective and subjective texture measurements by two treatments. Tortilla texture was improved by a treatment with a high enzyme level (170 mg/kg of maltogenic α-amylase, 0.14% CMC, 0.85% guar) as measured by objective tests and by a treatment with low enzyme level (60 mg/kg of maltogenic α-amylase, 0.43% CMC, 0.57% guar) as measured by subjective tests. The addition of maltogenic α-amylase (70 mg/kg) and CMC (0.35%) to FNM tortillas at levels similar to the low enzyme NCF treatment but with lower guar level (0.12%) improved tortilla texture. The maltogenic α-amylase softened tortillas by trimming the starch structure. This allowed the guar to interfere with amylopectin re-crystallization inside gelatinized starch granules. The CMC created a more flexible intergranular matrix that helped maintain the disrupted tortilla structure. Guar was ineffective in refrigerated tortillas, whereas, maltodextrins effectively improved refrigerated tortillas. The sequence of partial starch hydrolysis, warm holding condition, and time for guar to associate with starch and CMC was necessary to improve tortilla texture. Thus, different additives may be required for cold versus room temperature storage. Sugars increased in enzyme-treated tortillas during storage. This suggests that maltogenic α-amylase was only partially inactivated during baking of corn tortillas. Tortillas with more enzyme had lower and later pasting viscosity as measured by a Rapid Viscoanalyzer. Tortillas prepared from FNM also had lower and later pasting viscosity compared to NCF tortillas. Pasting viscosity of tortillas revealed intrinsic starch polymer characteristics and interactions. Results of this study provide commercially applicable information about desired levels for the extent of starch hydrolysis, the type and amount of gums and starches, and product microstructure to delay staling of corn tortillas.

In wheat (Triticum aestivum L), high molecular weight glutenin subunits (HMW -GS) are synthesized by the loci Glu-A1, Glu-B1, and Glu-D1 on the long arm of group 1 chromosome, and their variants play a significant role in the functional properties of flour; hence dough properties and tortilla quality. This study was conducted to understand the effects of HMW-GS on dough properties and tortilla quality using 40 different wheat lines from two different locations; Texas Agrilife Experiment Station at McGregor, and at Castroville, Texas, in 2010. Wheat lines in which one or more of these loci were absent (deletion lines) and non-deletion lines were used. Flours were evaluated for insoluble polymeric protein (IPP) content and mixograph properties. Dough properties; compression force, stress relaxation test, and dough extensibility, were determined using a texture analyzer. Tortillas were produced by hot-pressed method and evaluated for physical properties and textural change during 16 days of storage. Flour from deletion lines had lower average IPP content (38.4%) than non-deletion lines (41.9%). Dough from deletion lines were more extensible (44.8 mm) and required lower equilibrium force from stress relaxation test (4.91 N) compared to non-deletion lines (34.2 mm, and 6.56 N, respectively). Deletion lines produced larger diameter tortillas (177 mm) than non-deletion lines (165 mm) and had lighter color (L* = 82.3) than tortillas from non-deletion lines (L* = 81.0). Most of the deletion lines interestingly produced tortillas with acceptable flexibility scores on day 16 of storage (>= 3.0). Flour IPP content (r = -0.57) and equilibrium force (r = -0.80) were negatively correlated with tortilla diameter, but positively correlated with 16 day flexibility scores (r = 0.72, and r = 0.68, respectively). In general, deletion at Glu-A1 or Glu-D1 or presence of 2+12 instead of 5+10 allelic pair at Glu-D1 locus produced large diameter tortillas, but with poor day 16 flexibility. However, combination of 7+9 at Glu-B1 locus with deletions at Glu-A1 or Glu-D1 or 2+12 at Glu-D1 consistently produced tortillas that had large diameter and retained good flexibility scores during 16 days of storage. The results indicate the presence of 7+9 at Glu-B1 may play a crucial role in selection of wheat varieties for tortilla making.