Effects of Starch Gelatinisation on the Thermal,Dielectric and Rheological Properties of Extruded Corn Masa

The effects of processing on starch gelatinisation of corn masa prepared by extrusion were monitored by observing the changes in thermal diffusivity, starch crystallinity, peak viscosity and the differential dissipation factor (DDF). The results show that there is a threshold processing temperature (Tc), about 80 °C, above and below which different behaviour patterns for the measured properties are observed. The thermal diffusivity, starch crystallinity and the position of a peak in the DDF have a maximum at approximately Tc=80 °C. The peak viscosity decreases monotonically for Tc up to 80 °C and then remains constant. On the bases of textural characteristics of masa and tortilla, this work indicates that the degree of starch gelatinisation in the extruded masa is optimum at temperatures at approximately 80 °C where the room temperature thermal diffusivity and differential dissipation factors have maximum values. Textural analysis made in tortillas with masas prepared at various temperatures support the above conclusions.     

Effects of Soybean Fortification on Protein Quality of Tortilla-Based Diets Produced from Regular and Quality Protein Maize

The physiological development of laboratory rats fed with a typical indigenous tortilla diet was studied for two generations. The experiment compared casein control diet and five different types of diets: (1) a diet of tortillas obtained from fresh masa (FM); (2) regular tortillas produced from enriched dry masa flour containing vitamins B₁, B₂, niacin, folic acid, and the microminerals iron and zinc (REDMF); (3) tortillas produced from enriched dry masa flour fortified with 6% defatted soybean meal (FEDMF); (4) tortillas produced from enriched quality protein maize flour (EQPM); and (5) and, tortillas produced from enriched quality protein maize flour fortified with 3% defatted soybean meal (FEQPM). The growth of rats fed FEDMF and FEQPM diets was significantly higher (P<0.05) in both generations than their counterparts fed EQPM, REDMF, or FM diet. Animals fed quality protein maize (QPM) tortilla had the highest protein digestibility, but the FEQPM and FEDMF diets had the highest biological value (BV), net protein utilization (NPU), and protein-digestibility-corrected EAA scores (PDCEAAS). The difference among treatments was more evident in the second-generation rats. The pregnancy rate, number of newborns/litter, litter weight, and newborn survival rate was also higher for rats fed FEDMF, EQPM, and FEQPM diets than their counterparts fed REDMF and FM.     

Phase II-Inducing,Polyphenols Content and Antioxidant Capacity of Corn (<Emphasis Type="Italic">Zea mays</Emphasis> L.) from Phenotypes of White,Blue, Red and Purple Colors Processed into Masa and Tortillas

White, blue, red and purple corns (Zea mays L.) were lime-cooked to obtain masa for tortillas. The total phenolics and anthocyanins content, antioxidant activity expressed as total reducing power (TRP), peroxyl radical bleaching (PRAC), total antioxidant activity (TAA) and quinone reductase (QR) induction in the murine hepatoma (Hepa 1 c1c7 cell line) as a biological marker for phase II detoxification enzymes were investigated. Among the extracts prepared from raw corn varieties the highest concentration of total phenolics, anthocyanins, antioxidant index and induction of QR-inducing activity were found in the Veracruz 42 (Ver 42) genotype. The nixtamalization process (masa) reduced total phenolics, anthocyanins and antioxidant activities and the ability for QR induction when was compared to raw grain. Processing masa into tortillas also negatively affected total phenolics, anthocyanin concentration, antioxidant activities, and QR induction in the colored corn varieties. The blue variety and its corresponding masa and tortillas did not induce QR. Ver 42 genotype and their products (masa and tortilla) showed the greatest antioxidant activity and capacity to induce QR     

Effect of Lime and Wood Ash on the Nixtamalization of Maize and Tortilla Chemical and Nutritional Characteristics

The objective of the study was to obtain information on the chemical composition, functional properties, sensory quality and protein value of tortillas made from the nixtamalization of maize using either lime or wood ashes. The Ca, K, Mg, Fe, and Zn content of lime and wood ashes showed lime to be high in Ca content while wood ash contained more K and about 71% of the Ca content of lime. Both contained relatively high levels of Mg, Fe and Zn, but more so in the wood ashes. The level of reagent for nixtamalization was set at 0.8% of the maize weight. All other processing conditions were kept constant. The pH of the cooking solution was 12.0 for lime and 10.9 for wood ash. The moisture content of maize at 60 min of cooking was 45.8% for both treatments, however after 12 h of soaking, moisture level was 51.0% for the lime treatment and only 46.8% for the ash treatment. Solids (2.4%) in the lime cooking liquor were higher than in the wood ash liquor (1.0%). Chemical composition changes were similar between treatments in masa and tortilla; however, both masa and tortillas absorbed relatively high levels of all minerals including Fe and Zn from the wood ash treatment. The different treatment influenced functional properties particularly hardness and color. Tortilla characteristics were also similar. Protein quality of both alkali cooked products was lower than that of raw corn, more so the product from the wood ash treatment. Although some differences were observed in the sensory studies, human subjects did not dislike the wood ash made tortillas.     

Development and Evaluation of a Nutritionally Enhanced Multigrain Tortilla Snack

An increased consumption of healthy foods to reduce chronic diseases risks is needed. We developed and evaluated a multigrain snack as a nutritive alternative to the highly consumed corn tortilla chips. Corn, wheat, and chickpea grains were boiled in 1 % calcium oxide solution, steeped, washed, and ground before being mixed with soy protein isolate and oat flour to prepare the multigrain masa. Multigrain tortillas were moulded, baked, dried, and fried. Proximate composition, dietary fiber, protein quality, sensorial, and textural properties were evaluated. A commercial tortilla chip was used as control. The multigrain snack contained 153 % more protein, 53 % more dietary fiber, and 43 % less fat than commercial tortilla chips. Its lysine and isoleucine contents helped to increase the corrected-net protein utilization by 10 %, while digestibility increased from 83.5 to 91.8 % as compared to commercial tortilla chips. The mean breaking force was 6,082 g for the multigrain snack and 4,780 g for the commercial tortilla chips. The mean acceptability score for the multigrain snack was 12.1 (unstructured line scale 0–15 cm), and 82 % of the panelists rated the snack as acceptable. In conclusion, a nutritionally enhanced multigrain tortilla snack was developed which provides significantly more dietary fiber and protein and less fat than traditional commercial corn tortilla chips, but with comparable appearance and high acceptability.     

The Effects of Storage Temperature on the Staling of Wheat Flour Tortillas

Wheat flour tortillas (31·9% moisture) were stored at −60, −12, 0, 4, 22, and 35 °C to evaluate textural changes during staling. Subjective rollability and two-dimensional extensibility tests revealed that tortillas stored at ≥0 °C had increasing force, work and modulus of deformation values during storage. Tortillas stored at ≤−12 °C retained their fresh attributes over 25 days. Tortillas staled more as defined by rheological changes when stored at 22 °C than at 0, 4, or 35 °C. Optimum storage temperatures of wheat flour tortillas are ≤−12 °C while optimum staling temperatures are between 4 and 35 °C.     

Corn proteins solubility changes during extrusion and traditional nixtamalization for tortilla processing: A study using size exclusion chromatography

Changes in the solubility of corn proteins occurring during traditional nixtamalization and extrusion processes used to produce tortillas were studied using size exclusion chromatography, SDS-PAGE and the Dumas method to measure 50% propanol-insoluble protein. Size exclusion chromatography (HPL-SEC) studies furthered the understanding of protein solubility changes during both processes. Extrusion caused more protein aggregation in tortilla intermediate and final products than traditional nixtamalization. Mixing during extrusion and in the intermediate step of masa production in the traditional nixtamalization process was critical in reducing protein solubility. Baking tortillas also considerably reduced the protein solubility for the traditional nixtamalization process. Baking produced aggregation that could not be disrupted with a reducing agent.     

Effect of the nixtamalization with calcium carbonate on the indigestible carbohydrate content and starch digestibility of corn tortilla

There is a growing interest for an environment-friendly nixtamalization process. Nixtamalization with calcium salts generates a minimum level of polluting residues. The effect of a nixtamalization process with calcium carbonate (NCC) on the indigestible carbohydrate content and starch digestibility of tortillas was evaluated. Traditional and NCC tortillas showed lower moisture content than commercial tortillas. Similar protein, ash, and carbohydrate content were found for the three tortillas, but NCC tortillas showed the highest lipid content. The NCC tortilla had the highest dietary fiber content, with the highest insoluble dietary fiber level. Fresh and stored (96 h) NCC and traditional tortillas showed similar resistant starch content. Fresh traditional tortilla showed the highest slowly digestible starch (SDS), but upon storage the rapidly digestible starch (RDS) content of NCC tortilla decreased. Fresh traditional and NCC tortillas had lower predicted glycemic index (pGI) than commercial tortillas, and upon storage, the three tortillas presented lower pGI values than their fresh counterparts. Consumption of tortillas produced with the NCC can produce positive effects in the human health.     

Supplementing white maize masa with anthocyanins: Effects on masa rheology and on the in vitro digestibility and hardness of tortillas

The aim of this work was to supplement masa made from nixtamalized white maize flour (NWMF) with anthocyanins (0.0, 0.03, 0.06 and 0.12 g/100 g of masa), and to evaluate the effects on the rheological properties of the masa and on color, staling, in vitro digestibility, and hardness of tortillas. Tortilla baking reduced the content of anthocyanins by about 10%. The color parameters of the tortillas added with anthocyanins was similar to that of tortillas made with blue maize. Attenuated total reflection ATR-FTIR spectra showed that the 1022/1047 peak ratio increased, indicative that retrogradation increased with storage time, but the ratio was significantly lower for tortillas with added anthocyanins than without them, and lower for higher anthocyanins concentration. Freshly made tortillas added with anthocyanins exhibited lower ready digestible (about 35%) and slowly digestible (about 20%), but higher resistant (about 45%) starch fractions. Tortillas with 0.12 g of anthocyanins showed significantly lower hardness than the control tortillas (without added anthocyanins). Both previous mentioned effects can be associated with retrogradation, which on turn could be linked to anthocyanins-starch complexes and inhibition of amylolytic enzymes.     

Effects of storage on the physico-chemical properties of corn tortillas prepared with glycerol and salt

Corn tortillas have a short shelf life due to increased firmness and microbial spoilage. Commercial corn tortillas use carboxymethyl cellulose (CMC) to delay staling; however this gum is expensive when compared to the rest of the tortilla ingredients. Glycerol has been added to bread and wheat tortillas to increase pliability and salt has been shown to mask the flavor of glycerol in corn tortillas. The possibility to reduce staling in corn tortillas by adding glycerol/salt as an alternative to CMC was investigated by monitoring changes in physico-chemical properties during 2 weeks of storage at 25 °C. Molecular and macroscopic changes were followed using thermal and mechanical analysis. During storage an increase in amylopectin recrystallization was observed in all samples. The “freezable” water content of all tortillas decreased over the first 3–5 days of storage with an increase after 7 days, while moisture content and water activity remained constant. Glycerol/salt tortillas exhibited a sharper transition region in the DMA temperature scan suggesting a more homogenous sample. CMC tortillas were significantly stiffer than glycerol tortillas after 14 days of storage. Glycerol/salt combinations may offer at least a partial replacement for CMC since it helped control the stiffness, water homogeneity and distribution during storage.     

<Emphasis Type="Italic">Pulque</Emphasis>, An Alcoholic Drink from Rural Mexico,Contains Phytase. Its <Emphasis Type="Italic">in vitro</Emphasis> Effects on Corn Tortilla

Pulque is made by fermenting the agave sap or aguamiel of Agave atrovirens with a whole array of microorganisms present in the environment including several lactic acid bacteria and yeasts such as Saccharomyces cerevisiae. Ascorbic acid was determined in pulque and aguamiel, respectively. Phytase activity in lees, liquid and freeze-dried pulque was assayed by measuring the appearance of phosphate from phytate by a colorimetric method likewise phosphate from phytate present in fresh corn tortilla was measured after in vitro incubation with pulque. Iron, zinc, calcium, magnesium and selenium contents were measured in pulque and corn tortilla as well as in nixtamalized corn flour (NCF), the latter is used to make instant tortilla, since corn provides most of the energy as well as most of the phytate in the Mexican rural diet. Pulque showed phytase activity but much less ascorbic acid and iron than previously reported; additionally, phytase in pulque hydrolyzed most of phytate’s corn tortilla. Lees, which is mostly made of pulque’s microbiota, significantly accumulated iron and zinc but no selenium. NCF was fortified with iron by the manufacturers but poorly blended. There were significant differences on selenium content between tortillas samples, apparently some soils in central Mexico are selenium deficient. Moderate pulque intake appears to increase the bioavailability of iron and zinc bound by phytate in corn.     

Changes in the Solubility of Corn Proteins through Interaction with the Arabinoxylans in Extruded Nixtamalized Corn Flour Treated with Xylanase

The extrusion process allows the production of nixtamalized corn flour rich in arabinoxylans, which help to prevent cardiovascular and intestinal diseases. During extrusion, physiochemical properties of nixtamalized corn flour are negatively modified. The use of enzymes such as xylanase in order to obtain nixtamalized corn flour using extrusion has been studied as an alternative to reduce these changes in corn flour tortilla. The aim of this research was to evaluate changes in protein solubility of extruded nixtamalized corn flour with and without different concentrations of xylanase enzyme (0.05, 0.075, and 0.1 %, w/w). Soluble proteins of each corn flour were extracted and analyzed by SE-HPLC, while insoluble proteins were determined by the combustion method. In addition, each corn flour was analyzed by scanning electron microscopy (SEM). Results showed that the extruded nixtamalized corn flour, with and without xylanase, increased the protein solubility, and this effect was lower in extruded nixtamalized corn flour with xylanase. Insoluble protein diminished in corn flours either with or without xylanase enzyme. The addition of xylanase reduces the effect that the extrusion process has on the solubility proteins of extruded nixtamalized corn flour.     

Changes in Textural,Pasting and Thermal Properties of Wheat Buns and Tortillas During Storage

The texture, pasting and thermal properties of two common baked products made from wheat flour, buns and tortillas, were characterised periodically over 8 days of storage. Firmness of buns and tortillas increased throughout storage as measured using a texture analyser. Pasting viscosities of crumb-water slurries were measured with a Rapid Visco Analyser. Pasting viscosities at 74 °C, 95 °C of fresh products (one min after baking) were significantly lower than their respective dough pasting viscosities. No particular trend was observed in the pasting properties of bun and tortilla samples upon further storage up to 8 days. Amylose solubility decreased significantly immediately after baking in both buns and tortillas and continued to decrease throughout the storage period. Thermal analysis with a differential scanning calorimeter detected amylopectin recrystallisation almost immediately after baking (1 min) in tortillas, whereas amylopectin recrystallisation in buns was evident only after storage for 1 day. Amylopectin recrystallisation in tortillas continued to increase during storage. Overall, the harsher processing of buns, i.e. higher temperature, longer time and higher moisture environment, resulted in greater dispersion of amylose and amylopectin, and retrogradation of amylose in buns than in tortillas. Further, amylopectin crystallisation by itself did not contribute to staling, because more amylopectin crystallisation was observed in tortillas than in buns, even though the shelf life of tortillas is longer than buns.     

Blue Corn Tortillas: Effects on Learning and Spatial Memory in Rats

Consumption of pigmented corn has been associated with health benefits due to its flavonoid contents (mainly anthocyanins) and antioxidant ability. Therefore, the objective of this study was to determine the effect of blue corn tortilla (BM) consumption on memory and learning ability adult rats. Eighteen adult female rats were divided into three groups and fed for 38 consecutive days with commercial food (Control group) or the commercial food plus 6 g/day of either blue corn (BM) or white corn (WM) tortillas. Memory and learning capabilities were assessed using Barnes’s labyrinth at the end of the feeding period. Short-and long-term memory was improved in the BM group, showing that consumption of blue maize tortillas improves learning and memory capabilities in adult rats.     

Grain and Tortilla Quality in Landraces and Improved Maize Grown in the Highlands of Mexico

The maize produced in the highlands of Mexico (>2,400 masl) is generally not accepted by the flour and masa and tortilla industry. The objective of this work was to evaluate the grain quality and tortilla properties of maize landraces commonly grown in the highlands of Mexico and compare them with improved germplasm (hybrids). Germplasm analysis included 11 landraces, 32 white hybrids, and six yellow hybrids. Grain quality was analyzed for a range of physical and chemical factors, as well as for alkaline cooking quality. Landrace grains tended to be heterogeneous in terms of size, hardness and color. All landraces had soft-intermediate grains with an average flotation index (FI) of 61%. In contrast, hybrid grains were homogenous in size and color, and harder than landrace grains, with a FI of 38%. Protein, free sugars, oil and phenolic content in landraces were higher than in the hybrids. Significant correlations were found between phenolic content and tortilla color (r = −0.60; p < 0.001). Three landraces were identified as appropriate for the masa and tortilla industry, while all the hybrids evaluated fulfilled the requirements of this industry.     

Production of nixtamalized flour and tortillas from amarantin transgenic maize lime-cooked in a thermoplastic extruder

The potential use of quality protein transgenic maize (genetically modified maize with the cDNA of amarantin) for preparation of flour and tortillas through an extrusion lime cooking process was investigated. Tortillas from extruded transgenic maize flour had similar physicochemical and sensory properties than those from the commercial brand MASECA™; however, the former had the highest (P < 0.05) protein content (12.91 vs 8.93%, db), essential amino acids content, calculated protein efficiency ratio (C-PER; 2.27 vs 0.90) and protein digestibility corrected amino acid score (PDCAAS; 55.54 vs 30.18%) and therefore they were nutritionally better. The use of transgenic maize for flour and tortilla preparation through an extrusion lime cooking process may have a positive impact on the nutritional status of people from countries where maize is the basic staple food. It also represents an alternative process to nixtamalization that requires little energy and water, it does not generate wastewater, and all components of the maize kernel are retained.     

Phytochemical analysis of wastewater (nejayote) obtained after lime-cooking of different types of maize kernels processed into masa for tortillas

In order to generate value-added products from the wastewater (nejayote) of lime-cooked maize for tortilla production, we analyzed the phytochemical composition of six different types of kernels that were optimally cooked. Kernels, masas and nejayote solids were analyzed in terms of free and bound phenolics, ferulic acid and antioxidant (AOX) capacity. The germplasm analyzed included white (NWH), yellow (NYE), white quality protein (QPM), red (RED), high-carotenoid (HCA) and blue (BLU). Approximately 87, 82 and 91% of the phenolics associated to raw kernels, masa and nejayote were bound. Total phenolics of nejayote were about twice as much compared to kernels and masa. Lime-cooking reduced around 1/3 of bound ferulic in masa but enhanced at least 10 times the liberation of free moieties. The nejayote solids contained approximately 125 and 10 times as much free ferulic and 15 and 53 times more bound ferulic compared to kernels and masa. The nejayote solids contained approximately 40 and 8 times higher free and 191 and 61 times higher bound AOX capacities compared to those exerted by raw kernels and masa, respectively. Therefore, the nejayote solids are promising as a source of antioxidants which are known to promote health benefits and combat oxidative stress.     

Phytochemical analysis of wastewater (nejayote) obtained after lime-cooking of different types of maize kernels processed into masa for tortillas

In order to generate value-added products from the wastewater (nejayote) of lime-cooked maize for tortilla production, we analyzed the phytochemical composition of six different types of kernels that were optimally cooked. Kernels, masas and nejayote solids were analyzed in terms of free and bound phenolics, ferulic acid and antioxidant (AOX) capacity. The germplasm analyzed included white (NWH), yellow (NYE), white quality protein (QPM), red (RED), high-carotenoid (HCA) and blue (BLU). Approximately 87, 82 and 91% of the phenolics associated to raw kernels, masa and nejayote were bound. Total phenolics of nejayote were about twice as much compared to kernels and masa. Lime-cooking reduced around 1/3 of bound ferulic in masa but enhanced at least 10 times the liberation of free moieties. The nejayote solids contained approximately 125 and 10 times as much free ferulic and 15 and 53 times more bound ferulic compared to kernels and masa. The nejayote solids contained approximately 40 and 8 times higher free and 191 and 61 times higher bound AOX capacities compared to those exerted by raw kernels and masa, respectively. Therefore, the nejayote solids are promising as a source of antioxidants which are known to promote health benefits and combat oxidative stress.     

Phenolic Acids Profiles and Cellular Antioxidant Activity in Tortillas Produced from Mexican Maize Landrace Processed by Nixtamalization and Lime Extrusion Cooking

Phenolic acids profiles, chemical antioxidant activities (ABTS and ORAC), as well as cellular antioxidant activity (CAA) of tortilla of Mexican native maize landraces elaborated from nixtamalization and lime cooking extrusion processes were studied. Both cooking procedures decreased total phenolics, chemicals antioxidant activity when compared to raw grains. Extruded tortillas retained 79.6–83.5%, 74.1–77.6% and 79.8–80.5% of total phenolics, ABTS and ORAC values, respectively, compared to 47.8–49.8%, 41.3–42.3% and 43.7–44.4% assayed in traditional tortillas, respectively. Approximately 72.5–88.2% of ferulic acid in raw grains and their tortillas were in the bound form. Regarding of the CAA initially found in raw grains, the retained percentage for traditional and extruded tortillas ranged from 47.4 to 48.7% and 72.8 to 77.5%, respectively. These results suggest that Mexican maize landrace used in this study could be considered for the elaboration of nixtamalized and extruded food products with nutraceutical potential.