Specific enzymes have been used to improve flour quality for bread but enzyme action in tortilla flour has not been investigated. Two different wheat flours were prepared into tortillas using laboratory-scale, commercial equipment with fixed processing parameters. Dough and tortilla properties were evaluated using subjective and objective methods. Tortillas were stored in plastic bags at 22°C for evaluation. The effects of nine enzymes (amyloglucosidase 1, amyloglucosidase 2, bacterial 1, bacterial 2, fungal, maltogenic 1, maltogenic 2, malted barley and xylanase) on quality of wheat flour tortillas were evaluated. Dough absorption was adjusted to attain uniform dough for tortillas. Enzyme addition to tortilla flour did not significantly affect tortilla weight, moisture and pH. Bacterial 2 amylase extended shelf stability while maltogenic 1 and xylanase exhibited smaller improvements in shelf stability and other tortilla properties. Addition of 0.05 activity unit bacterial 2 amylase improved tortilla diameter and improved tortilla shelf life from 12 to 28 days. Maltogenic 1 at 280 ppm improved tortilla diameter, opacity and shelf life. Addition of 100 ppm of xylanase effectively improved tortilla diameter and shelf life. Bacterial 1 amylase at 60 ppm improved tortilla diameter but did not improve shelf stability. Amyloglucosidase 2, maltogenic 2 and malted barley amylase did not improve tortilla quality at any of the evaluated levels. Amyloglucosidase 1 and fungal amylase reduced overall tortilla quality at all the evaluated levels. Bread-making quality of wheat flour is correlated with the damaged starch present in the flour. Damage was induced by grinding the samples for 0, 1, 4 and 8 hr to determine the effects of starch damage on tortilla quality. Processing increased starch damage of control tortilla flour from 5.4% to 12.6%. Damage starch increased dough water absorption, toughness and press rating and reduced diameter and opacity of tortillas. Damage starch improved tortilla rollability at higher levels but did not improve tortilla properties in combination with bacterial 2 amylase. Overall tortilla quality was not improved due to additional starch damage. Improved tortilla quality using bacterial 2 amylase at very low levels could be commercialized.

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 99-106).

Antistaling properties of enzymes (xylanase, bacterial maltogenic and conventional a-amylases), CMC and vital wheat gluten on corn tortillas were evaluated during storage for up to 21 days. Effect of storage time (0-21 days) and temperature (-40, -20, 3, 10 and 21 oC) on tortilla staling was evaluated with or without additives. Addition of 275-1650 AU of ICS maltogenic amylase effectively reduced amylopectin retrogradation without reducing tortilla yields, but did not improve tortilla flexibility. The combination of 825 AU of ICS amylase (to interfere with intra-granular amylopectin re-crystallization) and 0.25% CMC (to create a more flexible inter-granular matrix than retrograded amylose) produced less stiff, equally flexible and less chewy tortillas than 0.5% CMC. Corn tortilla staling followed the basic laws that control aging in starch-based semi-crystalline systems such as starch gels, bread and other baked products. Amylopectin re-crystallization was the driving force behind the staling of corn tortillas. Increasing levels of re-crystallized amylopectin measured by DSC correlated significantly with increased tortilla stiffness and reduction in tortilla rollability, pliability and rupture distance during storage. Re-crystallization of amylopectin in fresh tortillas was not detected. It increased rapidly during the first 24 hr reaching a plateau after 7 days storage. The level of amylopectin re-crystallization on tortillas showed a bell-shaped trend along the evaluated storage temperature range with a maximum around 7 oC. However, a negative linear relationship of peak pasting viscosity with storage temperature of tortilla extracts without additives after 21 days suggests other compounds besides amylopectin affect tortilla staling. Thus, interfering with amylopectin re-crystallization is not the only way to retard staling. Further research is required to optimize the addition of maltogenic amylases in continuous processing lines that use fresh masa instead of nixtamalized corn flour, to determine how these amylases interfere with amylopectin re-crystallization and to elucidate if amylose retrogradation continues during storage and plays a role in tortilla staling.

Made available in DSpace on 2014-06-12T18:33:59Z (GMT). No. of bitstreams: 2 arquivo7877_1.pdf: 1597504 bytes, checksum: 48a982f8ba17650f3ce3a485aca1ec5a (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2006 / Investigo, por meio deste trabalho, aspectos da situação de Tortilla Flat (de John STEINBECK) e de Esteiros (de Soeiro Pereira GOMES) na História do romance. Para alcançar meu propósito, trilho um percurso que revê leituras que a crítica operou dos referidos livros sempre as inquirindo , problematiza os conceitos de ficção, realidade e História em suas implicações com a linguagem e, por fim, estuda as marcas do gênero romance e, particularmente, o papel da personagem de ficção (como individualidade ou como grupo) nessa esfera. Ainda que os dois textos literários sejam postos frente a frente em mais de um momento, não é aos referenciais da Literatura Comparada que eu me volto com maior constância; antes, às propostas de ISER (2002; 1997) para o estudo da ficcionalidade e de LUKÁCS (2000) e de BAKHTIN (1978) para o romance. Desprezando a eleição de fundamentos homogêneos para a discussão levada a cabo, recorro a vários teóricos e comentadores para embasar a minha própria visão das questões que abordo. Também fugindo à convencionalidade, analiso os romances pari passu às reflexões teóricas, o que, calculo, oferece maior organicidade à tese. Ao termo de minha investigação, foi possível perceber que (a) sendo o romance um gênero caracteristicamente multifacetado, é um instrumental de diversa cepa que fornece bases mais pertinentes ao seu inquérito, sempre com ênfase na inscrição histórica dos discursos; (b) os comentários que os autores literários emitem sobre as respectivas composições podem ser tomados como ponto de partida para a análise dos textos, mas, jamais, como referência inelutável; (c) tanto em Tortilla Flat como em Esteiros e por motivações distintas , a presença de um suposto protagonista coletivo não é capaz de lenificar o papel desempenhado pelos indivíduos ficcionais

No description available.

Master of Science / Food Science Institute / J. Scott Smith / The tortilla segment of the Mexican food market in the United States is rapidly growing. Tortillas are being used in many different mainstream applications, including wraps, lasagna, pizza, and appetizers. In 2000, the tortilla market was a $4 billion industry and with more than 85 billion tortillas consumed in the United States alone. As Mexican food becomes more common in the American diet, consumers start to branch out into a more authentic presentation of Mexican food. This causes a shift in consumption from flour to corn tortillas. As the consumer demand for corn tortillas increases, food manufacturing companies are challenged with producing a tortilla that will retain its softness, pliability, foldability, and flavor while remaining safe for consumption over several months. Since tortillas have two modes of deterioration, mold and staling, there are several factors that need to be considered. Hurdle technology is employed to prevent mold growth. By adjusting water activity, pH, storage temperature, and addition of preservatives mold growth can be prevented for a period of several months. Retaining tortilla texture over time is much more complicated. Tortillas stale through a complicated process of starch retrogradation. During cooking, the starch granules gelatinize and amylose and amylopectin leech out of the granules. After the tortillas are baked, the starch immediately begins to retrograde. The amylose and amylopectin complex together form a matrix that stiffens the tortilla. Based on current research, the shelf life of a corn tortilla can be extended through a combination of CMC (0.5%), maltogenic amylase (1650 Activity Units), sorbitol (3%), glycerol (4%).

No description available.

Effects of enzymatic modification of starch, proteins and pentosans on dough and tortilla properties were determined to establish the role of these wheat components in tortilla staling. Starch, protein and pentosans were respectively modified with a-amylase, protease and transglutaminase (TG), and xylanase. Tortillas were stored at 22oC and evaluated for at least three weeks. Amylase improved shelf-stability of tortillas, produced a significant amount of dextrins and sugars, retarded decrease in amylose solubility, and weakened starch granules. However, control and treated tortillas had similar degrees of amylopectin crystallinity. Staling of tortillas appears to involve starch that reassociates into an amorphous structure. Micrographs of control dough had thin protein strands forming a continuous matrix. Protease-treated dough had pieces of proteins in place of the continuous matrix, while TG-treated dough had thicker protein strands that were heterogeneously distributed. Both treatments resulted in shorter shelf-stability of tortillas. The organization of protein in dough is important for dough structure and appears to impact tortilla flexibility. Protein solubility and SDS-PAGE results did not differentiate control and treated dough or tortillas. The fractions or molecular weight distribution are not significant determinants of protein functionality. Tertiary and quaternary protein structures of gluten may be more related to tortilla shelf-stability. The 75 ppm xylanase treatment resulted in weaker tortilla structure and significantly higher amounts of low molecular weight saccharides and sugars. Control and the 25 ppm treatment sample had a similar shelf-stability and texture profile. Pentosans may affect staling indirectly through the effect on gluten development. Fresh tortillas have amylopectin in an amorphous state, while amylose is mostly retrograded. The gluten matrix provides additional structure and flexibility to the tortilla. Pentosans may or may not be attached to the gluten network. Upon storage, amylopectin retrogrades and recrystallizes, firming the starch granules, resulting in firmer tortillas. Starch hydrolysis decreased the rigid structure and plasticized polymers during storage. It also reduced the restriction imposed by retrograded starch on gluten and allowed it more flexibility. Thus, the flexibility of tortillas results from the combined functionalities of amylose gel, amylopectin solidifying the starch granules during storage, and the changed functionality of gluten after baking.

The effects of the fortification of tortilla chips with mechanically expelled soy flour as well as baking and frying processes on the properties of tortilla chips were evaluated. Sensory characteristics, texture, thickness, color, protein and oil content were evaluated. Texture was measured by objective and subjective tests. Sensory properties were evaluated using a nine point hedonic scale. Soybeans (food grade Hartz) were mechanically expelled to obtain partially defatted soy flour of 6.7% final oil content. Dry masa flour (DMF) was replaced with 0, 10, 20 and 30% mechanically-expelled soy flour (MESF). The equilibrated tortilla was either fried in oil or baked in an air-impingement oven followed by convection oven drying. Overall, fried tortilla chips were harder and thicker than baked tortilla chips. Fried tortilla chips with 20 and 30% soy flour substitution required less force to break. In fried tortilla chips, as MESF increased, force and work levels decreased, where 20% MESF had the lowest force values. Thickness measurements of tortilla chips showed that as the thickness increased, the force and work also increased. Protein increased linearly in baked and fried tortilla chips where 30% resulted in the highest protein level. In fried tortilla chips, MESF fortification increased oil levels linearly as well. Baked tortilla chips were lighter than fried tortilla chips. In a consumer sensory evaluation, fried tortilla chips were preferred more than the baked ones. In fried tortilla chips, 20% had the highest sensory scores overall. Ten and 20% MESF fortification in fried tortilla chips were the most acceptable of all. In all treatments, regardless of type of processing, panelists could not detect any “beany” flavors in any of the samples. Therefore, dry extrusion followed by mechanical expelling proved successful in creating a suitable soy flour for tortilla chip production. MESF can be added at 10-30% levels in tortilla chips. Up to 20% would be recommended. Frying results in higher acceptability consumer scores over baking.

This dissertation is an ethnographic work describing how foodways have become central to identity negotiation in a Maya village that has recently been impacted by evangelical conversion and tourism. This village is in the region of Quintana Roo, Mexico best known for its involvement in the Caste Wars of Yucatán and historic resistance to assimilation to Mexican identity. However, in recent years, the demand for inexpensive labor in the hotel zone of the Caribbean coast of Quintana Roo has led to improved infrastructure and transportation to these villages. With this improved infrastructure has come increased outside interaction including the establishment of evangelical churches and day labor buses. These combined influences of religion and labor changes have led to new ways of negotiating identity that had not previously existed in village life here. Because life in this village had always centered on subsistence farming and its associated food getting and food making tasks, the option for wage labor and evangelical religion have provided a support system for those unable or unwilling to participate in traditional forms of subsistence. The new social structures are often negotiated using food and foodways as a declaration of belonging or resistance. My work provides vignettes describing these processes of identity negotiation at the national, regional and familial levels. / text