Physiochemical Changes of Starch During Maize Tortilla Production

The physiochemical changes of starch in maize tortillas and their intermediate products commercially processed by the traditional way have been determined. Samples of maize, nixtamal, dough or masa, tortilla and nejayote (steep liquor) were analyzed. The samples were assayed for water absorption index (WAI), resistant starch (RS), X-ray diffraction patterns, viscosity and with Differential Scanning Calorimetry (DSC). Enthalpy of fusion (ΔH), initial temperature (T_o) and transition temperature (T_p) of gelatinization were obtained from DSC curves. Resistant starch contents increased as the products advanced in the process. Significant differences (p > 0.05) in the fusion enthalpy values of maize, nixtamal and masa could not be found. X-ray diffraction patterns of maize, nixtamal and masa did not show significant changes; however, when masa was transformed into tortillas there was a large loss in crystallinity. The viscoamylograph peak viscosities increased from maize to masa and decreased drastically in tortillas. The data showed that the tortilla baking stage caused the most pronounced changes in starch.     

Enhancement of Corn Nixtamalization by Power Ultrasound

Nixtamalization, a key production step for masa flour used for tacos, corn tortillas, and chips, traditionally involves corn kernel cooking for 1 h and a lengthy process of steeping (16–18 h) in a lime solution. This study aimed at accelerating the traditional nixtamalization (TN) process using power ultrasound with acoustic energy density around 1.85 W/g for 1 h during cooking followed by brief steeping for 1 h. The cooked kernels (nixtamal) were evaluated for texture and color, while the cooking liquor (nejayote) was evaluated for solid losses. The power ultrasound-assisted nixtamalization resulted in significantly (p?≤?0.05) reduced process time and softer nixtamal with less solid losses in nejayote than control (TN). Response surface methodology established significant relationships of sonication duration and cooking temperature to texture, color of nixtamal, and dry matter loss in nejayote. This study indicates that power ultrasound ameliorated traditional nixtamalization in terms of quality and operation time.     

Characteristics of nixtamalised maize flours produced with the use of microwave heating during alkaline cooking

Whole, ground and abrasively dehulled grains from both normal (H‐34 and H‐34) and quality protein (QPM and QPMa) maize were mixed with water contents of 70, 95 and 100 g kg⁻¹ and calcium hydroxide concentrations of 0.0, 0.3, 0.5 and 2.0 g kg⁻¹ and heated (operating frequency 2.450 MHz, high‐power setting) for 10, 15 and 20 min in a commercial microwave oven. The cooked grain was then oven dried and milled to obtain nixtamalised maize flour (NMF). The protein contents and test weights of QPM were higher than for the normal hybrids. The highest yields of masa and tortillas were found for the normal hybrids, and these samples did not show significant differences, as compared with the commercial nixtamalised flour (CNMF) used as control, with respect to masa firmness and adhesiveness and tortilla tensile strength. The cutting force of tortillas from hybrid H‐30 and QPM did not show significant differences from the control. The highest values of tortilla rollability were found for the control followed by hybrid H‐34. The values of residual cooking liquor for microwave‐heated samples were lower than for the control. Ground or dehulled maize grain gave sticky masa and poor mechinical characteristics. Tortillas from whole grain showed good characteristics of texture and consistency of masa, and the tortillas were subjectively similar in colour, flavour and rollability to the tortillas prepared with CNMF. These results indicate a potential use of microwave energy to produce NMF for tortillas and derivatives. © 2000 Society of Chemical Industry     

Characteristics of Tortillas Prepared from Dry Extruded Masa Flour Added with Maize Pericarp

Corn flour produced by extrusion was used to evaluate the effect of added maize pericarp (0 to 6%, w/w) on the following parameters: water absorption capacity of dry extruded masa flour (DEMF); weight loss during cooking and dehydration rate (DR) in fresh masa (FM), as well as rollability (R), puffing degree (PD), and cutting force (CF) of tortillas. CF was evaluated after 1 and 24 h of preparation. The viscoamylogram profiles, x‐ray diffraction, and crystallinity of DEMF and powdered tortillas were also obtained. The DEMF with 3% (w/w) of pericarp produced the highest tortilla yield, improved the PD, DR, R, and CF characteristics of FM and tortillas, and developed the highest viscosity and a structure with adequate crystallinity to make tortillas with commercial quality.     

Whole-grain corn tortilla prepared using an ecological nixtamalisation process and its impact on the nutritional value

Corn tortillas are produced using the traditional nixtamalisation process (TP). Nevertheless, one of the greatest problems that the tortilla industry faces is the high level of losses of solids. The aim of this research was to evaluate the nutritional value of a whole-grain tortilla, produced using an ecological process (EP). In the EP corn was cooked at 90 °C with 1.8% (w/w) calcium sulphate. The grains were steeped, washed and grounded to obtain the masa, which was baked to produce tortillas. Also, tortillas were prepared using the TP and following the same steps as those used in the EP, except that 1.0% (w/w) of calcium hydroxide was used. The tortillas from EP retained 14.05, 6.03, and 54.02% more fat, protein and fibre than tortillas produced by the TP. The PER value of rats fed whole-grain tortillas (1.81) was not different from that of rats fed the traditional tortillas (1.85).     

Corn Masa and Tortillas from Extruded Instant Corn Flour Containing Hydrocolloids and Lime

Extruded instant corn flour (EICF) samples with hydrocolloids (gums), such as gum arabic, carboxymethylcellulose (CMC), guar and xanthan and with different concentrations of lime (0.1, 0.2 and 0.3% w/w) were prepared by extrusion. The gums were added before or after thermal processing. The dehydration process followed through the weight loss (WL) in masa, the physicochemical (water absorption capacity (WAC) and WL during cooking) characteristics of masa were optimized to give longer dehydration times and tortillas with good textural (rollability, tensile strength and cutting force) properties. The lowest effective moisture diffusion coefficient (D*) was found in masa samples containing 0.2% (w/w) of lime and 0.5% (w/w) of the xanthan gum added before extrusion. These masas produce tortillas with optimum textural characteristics and highest yields.     

Prevention of the development of polluting characteristics in cooking water residue from nixtamalisation of corn by removing solid lime particles

Removing solid lime particles (SLP) may help to prevent polluting characteristics of corn cooking wastewater (nejayote). The objective of this study was to evaluate the polluting characteristics of nejayote and characteristics of nixtamal, masa and tortilla using SLP-free solutions (SLPF) for the nixtamalisation process. Two SLPF treatments: calcium hydroxide (CHYDROX) and calcium oxide (COXIDE) were compared against traditional nixtamalisation (TRADNIX). Polluting characteristics including pH, settleable solids, total hardness, alkalinity and chemical oxygen demand (COD) reduced by 29.5% and 24.3%, 61.9% and 63.3%, 46.3% and 54.7%, 43.3% and 55.1%, 41.1% and 67.7% in CHYDROX and COXIDE, respectively, compared to TRADNIX. Masas and tortillas from SLPF treatments were whiter than those from TRADNIX. Moisture in SLPF tortillas was lower by 4.3–6.3% compared to TRADNIX. Tortillas from SLPF treatments had higher maximum tensile strength (0.04–0.08 N mm⁻²) than TRADNIX. Removing SLP is a viable strategy for preventing pollution from the nixtamalisation process.     

A comparison of the quality of whole corn tortillas made from instant corn flours by traditional or extrusion processing

Summary The nutritional quality (chemical and biological assays) was evaluated for tortillas made with two samples of instant corn flour prepared with 0.15 and 0.25% calcium hydroxide and processed either by extrusion or by the traditional process (nixtamalization). Both raw corn and the tortillas made from instant whole corn flours prepared by extrusion (TEP) had higher Protein Efficiency Ratio (PER), and Net Protein Utilization (NPU) values ( p < 0.05) than tortillas prepared from traditional nixtamalization process. The Ca assimilation in the femurs bones of rats fed with raw corn, TEP (with 0.25% lime), and tortillas prepared from the nixtamal process, yielded lower values ( p < 0.05) as compared with those shown by the rats fed with the other treatments of TEP (with 0.15% lime). The Ca, Mg, and P contents and protein quality of the treatments used in the feed affected some physical characteristics rat femurs (length, diameter, weight, breaking force, volume and density). The force required to break the femurs of rats fed diets of raw corn, tortillas prepared using the traditional process and without added protein, was measured and compared with the force required to break the femurs of rats fed with diets contain casein and TEP with either 0.15 and 0 0.25% lime. Those animals assimilating the lowest content of lime had the weakest femurs.     

Nixtamalisation of maize (Zea mays L) using a single screw cook-extrusion process on lime-treated grits

The tortilla flour market is expanding but present industrial production is lagging behind in the use of modern technologies to increase production and cut costs due to the maize steeping and drying operations. A process using a single-screw cook-extruder which eliminates the traditional steeping and drying operations was therefore explored. Lime (Ca(OH)₂) suspension was absorbed onto commercial maize grits (2 g lime kg^?1 maize) and the resulting meal conditioned to various moisture contents. These samples and one which had not been lime-treated were cook-extruded through a Brabender Do-corder extrusion cooker (Type 825602). The dry extrudate was milled through a 150 μm sieve and tortillas made from each sample. The tortillas prepared from the lime-treated grits conditioned to 472 g kg^?1 moisture compared favourably with that prepared from traditionally prepared masa flour when organoleptically assessed. Flour pasting properties (viscosity) and water absorption index were not significantly different (P < 0.05) from the traditionally prepared products. Enzyme susceptible starch index did not correlate well with dough quality.     

Studies and Biological Assays in Corn Tortillas Made From Fresh Masa Prepared by Extrusion and Nixtamalization Processes

ABSTRACT: :
The nutritional composition and protein efficiency ratio (PER) of raw corn meal and of tortillas prepared by extrusion and nixtamalization processes were determined. Rats were fed with diets containing unprocessed raw corn meal (RCM), tortillas prepared from extruded fresh masa without lime (ET), tortillas made from extruded fresh masa with 0.25% lime content (ETWL), and tortillas made with the traditional nixtamalization method (NT). The ETWL had higher protein (8.50%) and dietary fiber (14.52%) contents than did the NT (8.15% protein and 7.39% dietary fiber). The PER value of the ETWL diet was 14.65% higher (P ≤ 0.05) than that of the RCM diet and equivalent to that of the NT diet.     

Aflatoxin‐detoxification achieved with Mexican traditional nixtamalization process (MTNP) is reversible

To evaluate the effectiveness of maize detoxification achieved with the Mexican traditional nixtamalization process (MTNP), grain contaminated with 678.3 µg/kg of total aflatoxins was processed into tortillas. The MTNP caused an apparent 93.2% decrease in aflatoxin content in tortillas. However, extracts acidification prior to mycotoxin quantification caused in maize dough (masa) a 57.2% reformation of the original aflatoxin and 33.9% in tortillas. According to these results, the MTNP seems not to be safe for total detoxification, since a high percentage of the original aflatoxin content can be reverted to the original fluorescent form by the acidic medium. Acidification of the aflatoxin extracts, as occurs during digestion, would lead to a rebuilding of the aflatoxin molecule. Copyright © 2004 Society of Chemical Industry     

Tortillas from Extruded Masa as Related to Corn Genotype and Milling Process

The effect of mill type (Knife and Hammer mill) and screen size (500 and 800μ) on properties of masa and tortillas from two types of corn (dent and floury endosperm) were evaluated. The traditional process was a control. Particle size and starch damage were highest for knife mill with screen opening 500μ. Tortillas from dent corn had better quality than those from floury corn. Cutting force, tensile strength, and rollability of tortillas from extruded masa from dent corn hammer milled with 800μ screen, and those made with floury corn knife milled with 500μ screen, compared favorably with traditional tortillas. Overall quality score correlated with starch damage, adhesiveness and peak viscosity.     

New ecological nixtamalisation process for tortilla production and its impact on the chemical properties of whole corn flour and wastewater effluents

An ecological nixtamalisation process (EP) for making whole corn flour for tortillas was compared with the traditional nixtamalisation process (TP). One of the problems of TP is high level of solid losses. The aim was to evaluate the composition of these losses. In EP, dry matter losses of nejayote were from 1.2% to 1.4%, while in TP 3.2%. Nejayote from TP showed a pH of 11.9, whereas EP showed a pH close to neutral. The pericarp was retained in EP with the use of calcium salts, whereas in TP lime destroyed it almost completely. Losses of total dietary fibre in nejayote solids were about 41.2% for TP compared to an average of 17.4% for EP. Most of nejayote losses in TP were soluble fibre (30.4%), compared with EP that ranged from 6.2% to 7.9%. All compounds retained by nixtamal from EP are important sources of nutrients and dietary fibre.     

Physicochemical and rheological characteristics of commercial nixtamalised Mexican maize flours for tortillas

Three commercial nixtamalised Mexican maize flours (CNMFs) designated HI‐A, HI‐B and HI‐C were evaluated in this work. For each brand, four samples corresponding to four consecutive months of production were evaluated. Tortillas prepared by the traditional process of nixtamalisation were used as the control. The maize flours and their respective tortillas showed variations between samples in their physical, chemical and rheological parameters. The three commercial maize flours incorporated additives and preservatives. The moisture content, colour, pH, subjective water absorption capacity, water solubility index, water absorption index and swelling capacity of flours showed strong differences between the three CNMFs with respect to the chemical analysis. Important differences in the protein, calcium and amylose contents were observed. Tortillas from CNMFs had a blander maize flavour, less desirable texture and staled more rapidly than traditional tortillas. Some modifications are required in the current Official Mexican Quality Standard, principally in the appropriate selection of additives and levels used in the preparation of CNMFs. © 2000 Society of Chemical Industry     

Scanning electronmicroscopy studies of limed corn kernels for tortilla making

Scanning elecronmicroscopy (SEM) was used to study changes in corn kernel structure during the lime treatment of the tortilla making process. The outside surface of the alkali-treated kernels (nixtamal) showed substantial structural alteration, which facilitate its separation.The aleurone and some pericarp layers are retained in nixtamal. Most of the germ remains attached to the starchy endosperm, and greatly contributes to the nutritional quality of the product.The cell walls of the horny and floury endosperm appeared noticeably affected in the preparation of nixtamal. The functional and nutritional properties acquired by nixtamal might be related to the structural modification as shown by SEM.     

Shelf-life of tortilla extended with fungal amylases

Corn (maize), the main source of starch and calories in the Mexican diet, is consumed mainly as tortillas , which have a short shelf-life. A fungal α-amylase blend (10μU g⁻¹) was added during hydration of maize flour to produce masa , and modified the starch during tortilla cooking up to the denaturating temperature. Control and treated tortillas , fresh and staled by storage at −12°C and by freeze-thaw cycles, were compared for amounts of retrograded starch, flexibility, rheological properties and by preference ranking by a panel of 75 judges. Results showed significant improvements in delayed staling and, by implication, extended shelf-life. The process was regarded as financially viable on a commercial scale.     

CHARACTERIZATION OF MASA AND LOW-MOISTURE CORN TORTILLA USING STRESS RELAXATION METHODS

The stress relaxation technique successfully detected changes in masa due to differences in initial moisture content and resting conditions (time and packaging). Changes in softness of corn tortillas was evaluated (fresh to stale) using the stress relaxation technique in uniaxial tension, and bending-tension. Stiffness and energy dissipated were the best tortilla texture indicators. High correlation was observed between the total energy dissipated for fresh corn masa and the stiffness of fresh corn tortilla tested under tension mode. A mathematical model was built to estimate the stiffness of fresh corn tortilla using fresh masa characteristics. Stress relaxation under uniaxial tension showed good correlation with the scores from the subjective rollability method.     

Fumonisin B1 and hydrolyzed fumonisin B1 (AP1) in tortillas and nixtamalized corn (Zea mays L.) from two different geographic locations in Guatemala.

Fumonisin B1 (FB1) is a common contaminant of corn worldwide and is responsible for several diseases of animals. In the preparation of tortillas, corn is treated with lime (producing nixtamal) that when heated hydrolyzes at least a portion of the FB1 to the aminopentol backbone (AP1), another known toxin. This study analyzed the amounts of FB1 and AP1 in tortillas and nixtamal from two communities in the central highlands of Guatemala where corn is a major dietary staple (Santa Maria de Jesus, Sacatepequez, and Patzicia, Chimaltenango). The amounts of FB1 and AP1 in tortillas from Santa Maria de Jesus were, respectively, 0.85 +/- 2.0 and 26.1 +/- 38.5 microg/g dry weight (mean +/- SD), and from Patzicia were 2.2 +/- 3.6 and 5.7 +/- 9.4 microg/g dry weight. Less than 6% of the tortillas from both locations contained > or = 10 microg FB1/g dry weight; whereas, 66% of the samples from Santa Maria de Jesus and 29% from Patzicia contained > or = 10 microg AP1/g dry weight. The highest amount of AP1 (185 microg/g dry weight) was found in tortillas from Santa Maria de Jesus. The highest amounts of FB1 were 6.5 and 11.6 microg/g dry weight in tortillas from Santa Maria de Jesus and Patzicia, respectively. The mean concentration of FB1 in nixtamal was significantly higher in Santa Maria de Jesus compared to Patzicia. Surprisingly, AP1 was not detected in any of the nixtamal samples. The human impact of exposure to these amounts of fumonisins is not known. However, based on findings with other animals, where corn is a dietary staple, long-term consumption of FB1 and AP1 (especially at > or = 10 microg/g of the diet) may pose a risk to human health.     

Amylose lipid complexes formation as an alternative to reduce amylopectin retrogradation and staling of stored tortillas

The impact of addition of palmitic acid (PA) on the amylose-lipid complexes formation and their influence on amylopectin retrogradation were studied. Tortillas prepared with 0.0%, 1.0% and 1.5% (w/w) of PA were stored for 0, 7, and 14 days at 4 °C. Tortillas with 1.0% and 1.5% of PA were softer than tortillas without PA during storage time; this change can be associated with reduction in starch retrogradation. Texture evaluation suggests that retrogradation reduction, influences directly tortilla texture (r = 0.82; P < 0.007). Thermal analysis revealed that tortillas had three endotherms corresponding to melting of (i) retrograded amylopectin, (ii) type I amylose-lipid complexes and (iii) type II amylose-lipid complexes. Addition of palmitic acid to masa during tortilla-making process may be an alternative strategy to reduce starch retrogradation and tortilla staling.     

Changes in Corn and Sorghum During Nixtamalization and Tortilla Baking

Structural changes occurred in corn and sorghum during the alkaline-cooking process as it progressed from the raw kernel to the tortilla. The alkali weakened the cell walls, facilitating the removal of the pericarp, solubilized cell walls in the peripheral endosperm, caused swelling and partial destruction of starch granules, and modified the physical appearance of the protein bodies. Masa (ground nixtamal) consisted of small pieces of germ, pericarp, aleurone and endosperm, and free starch granules, cell fragments, and dissolved or dispersed solids and lipids in water. During tortilla baking, an additional degradation of cell walls, further loss of starch crystallinity, and partial destruction of protein bodies occurred.