Study of Calcium Ion Diffusion in Nixtamalized Quality Protein Maize as a Function of Cooking Temperature

In this report, the effect of temperature on the calcium content of Quality Protein Maize (QPM H-368C) during the nixtamalization process as a function of the steeping time for three cooking temperatures (72, 82, and 92°C) is presented. Also, for the first time, we report in physico-chemical terms the end of the cooking stage during the nixtamalization process that was established when the moisture content in corn kernels reached a value of 36% (w/w) with a lime concentration of 1% (w/v), independent of the cooking temperature. Atomic absorption spectroscopy was used to determine the calcium concentration in the whole kernel and in its different anatomical components (pericarp, endosperm, and germ) as well as in 10% of the outermost layers, the next 10%, and the remaining 80% of the endosperm as a function of the steeping time. It was found that if the cooking temperature increases, the calcium content increases also. For steeping times in the range of 5–7 hr, a relative maximum was found in the calcium contents of 0.24, 0.21, and 0.18% (w/w) in QPM H-368 flours at 92, 82, and 72°C, respectively. Calcium was found in the most external layers in the endosperm and minimum diffusion occurs in the internal 80%. Phosphorous was measured by using UV spectroscopy and the results showed that it remains constant at 0.24% throughout the process. Scanning electron microscopy analysis was used to explain the calcium ion diffusion in the kernel. The physical changes in the pericarp govern the calcium diffusion process.     

A Radioisotopic Study of the Entry of Calcium Ion into the Maize Kernel During Nixtamalization

The entry of calcium ions from the nixtamalization solution into maize kernels over time was followed in model experiments using radiolabeled calcium ions, with autoradiographic evaluation of the kernels after different cooking and steeping times. Calcium ions immediately entered the pericarp and were rapidly fixed at the outer boundary of the endosperm, especially at the external surface of the germ. Entry of calcium into the endosperm occurred gradually after long steeping times, except in the case of broken kernels, for which massive invasion by calcium was observed. After extended steeping times, a moderate amount of calcium‐45 was evident in the germ. Specific perforation of the outer layers of the grains provided a defined route of facilitated entry of calcium into the endosperm. No fundamental difference with respect to penetrability by calcium ion was seen in a comparison between flint‐type grains and grains containing only floury endosperm.     

Effect of processing conditions on phytic acid, calcium, iron, and zinc contents of lime-cooked maize

Tortillas are made by cooking maize in a lime solution during variable times and temperatures, steeping the grain for up to 12 h, washing and grinding it to a fine dough, and cooking portions as flat cakes for up to 6 min. The effects of the main processing steps on the chemical composition, nutritive value, and functional and physicochemical characteristics have been areas of research. The present work evaluates the effect of lime concentration (0, 1.2, 2.4, and 3.6%) and cooking times (45, 60, and 75 min) on phytic acid retention of whole maize, its endosperm, and germ, as well as on the content of calcium, iron, and zinc on the same samples. The effects of steeping time and temperature and steeping medium on the phytic acid of lime-cooked maize were also studied. Finally, phytic acid changes from raw maize to tortilla were also measured. The results indicated that lime concentration and cooking time reduce phytic acid content in whole grain (17.4%), in endosperm (45.8%), and in germ (17.0%). Statistical analyses suggested higher phytic acid loss with 1.2% lime and 75 min of cooking. Cooking with the lime solution is more effective in reducing phytic acid than cooking with water. Steeping maize in lime solution at 50 degrees C during 8 h reduced phytic acid an additional 8%. The total loss of phytic acid from maize to tortilla was 22%. Calcium content increased in whole maize, endosperm, and germ with lime concentration and cooking and steeping times. The increase was higher in the germ than in the endosperm. The level, however, can be controlled if steeping of the cooked grain is conducted in water. Iron and zinc contents were not affected by nixtamalization processing variables but were affected in steeping.     

Study of Structural and Thermal Changes in Endosperm of Quality Protein Maize During Traditional Nixtamalization Process

This work presents the study of the structural changes of the endosperm of Quality Protein Maize (QPM H-368C), modified by alkaline cooking at two different temperatures (72 and 92°C) and steeping time of 0–7 hr. Structural changes in the outermost 10% layers, the subsequent 10%, and the remaining 80% of the endosperm as a function of the steeping time were studied using scanning electron microscopy (SEM), X-ray diffraction, and differential scanning calorimetry (DSC) techniques. SEM images revealed that soft and hard endosperm have different shapes and packing factors. The X-ray diffraction patterns of the hard and soft endosperm from raw corn suggest that the hard endosperm consists mainly of amylopectin and has a bigger relative crystallinity quality than the soft endosperm. Samples cooked at 72 and 92°C with and without the (Ca(OH)₂ and steeped for 0, 3, and 7 hr, showed structural changes, X-ray diffraction patterns from the outermost 10% layers and subsequent 10% of the endosperm were completely amorphous. This fact is related to the total or partial gelatinization of the starch. The crystallinity in the internal layers of endosperm (remaining 80%) did not have significant changes after the treatments and exhibited the characteristic patterns of crystalline amylose and amylopectin. DSC measurements in the outermost layers of the endosperm did not exhibit the characteristic endothermic peak of starch (from 64 to 81°C) compared with the raw sample, while the endotherm peak for 80% of the endosperm internal layers appears in all cases (72 and 92°C). According to these results, a new definition of the nixtamalization process can be developed as follows. During the nixtamalization process there is a total gelatinization of the starch granules from the most external layers, and a partial gelatinization of the innermost internal layers of the endosperm.     

Revising the role of pH and thermal treatments in aflatoxin content reduction during the tortilla and deep frying processes.

Naturally aflatoxin-contaminated corn (Zea mays L.) was made into tortillas, tortilla chips, and corn chips by the traditional and commercial alkaline cooking processes. The traditional nixtamalization (alkaline-cooking) process involved cooking and steeping the corn, whereas the commercial nixtamalization process only steeps the corn in a hot alkaline solution (initially boiling). A pilot plant that includes the cooker, stone grinder, celorio cutter, and oven was used for the experiments. The traditional process eliminated 51.7, 84.5, and 78.8% of the aflatoxins content in tortilla, tortilla chips, and corn chips, respectively. The commercial process was less effective: it removed 29.5, 71.2, and 71.2 of the aflatoxin in the same products. Intermediate and final products did not reach a high enough pH to allow permanent aflatoxin reduction during thermal processing. The cooking or steeping liquor (nejayote) is the only component of the system with a sufficiently high pH (10.2-10.7) to allow modification and detoxification of aflatoxins present in the corn grain. The importance of removal of tip, pericarp, and germ during nixtamalization for aflatoxin reduction in tortilla is evident.     

Effect of Temperature and Steeping Time on Calcium and Phosphorus Content in Nixtamalized Corn Flours Obtained by Traditional Nixtamalization Process

This report shows the effect of temperature (72, 82, and 92°C) during the cooking stage and steeping time (0, 1, 3, 5, 7, 9, 11, 13, and 15 hr) on calcium and phosphorus contents in nixtamalized corn flours obtained by the traditional nixtamalization process (NCF). In addition, calcium and phosphorus contents in industrial nixtamalized corn flours were analyzed for comparative purposes. Atomic absorption spectroscopy and UV‐vis spectroscopy methods were used to study the calcium and phosphorus contents as well as the Ca²⁺/P ratio in NCF and industrial nixtamalized corn flours. Additionally, deposition and identification of calcium compounds in the nixtamalized corn pericarp were analyzed by low‐vacuum scanning electron microscopy, energy dispersive spectrometry, and X‐ray diffraction techniques. Dry matter loss in NCF is also reported. As the temperature increased, Ca²⁺ content was enhanced, while the phosphorus content decreased with statistical differences (P ≤ 0.05) between thermal treatments. Ca²⁺ content in industrial nixtamalized corn flours was significantly lower (P ≤ 0.05) than that of NCF. On the other hand, no statistical differences (P ≤ 0.05) were found between phosphorus content in commercial nixtamalized corn flours and NCF. Calcium compounds, identified as calcite, were detected in corn pericarp. Statistical differences (P ≤ 0.05) were observed in phosphorous content in NCF obtained at different cooking temperatures. In addition, a decrease in phosphorus levels significantly correlated with the steeping time at 92°C (r = –0.91). At 72, 82, and 92°C, the average Ca²⁺/P ratio in NCF was 0.45 ± 0.03, 0.61 ± 0.05, and 0.82 ± 0.05, respectively, indicating a correlation between this parameter and the cooking temperature. However, no correlation was found between the Ca²⁺/P ratio and the steeping time. This behavior is attributed to calcium attached to corn kernel. In commercial nixtamalized corn flours, the Ca²⁺/P ratio was significantly lower (P ≤ 0.05) than that of NCF. There was a significant correlation (P ≤ 0.01) between dry matter loss and steeping time (r = 0.99) in NCF, this fact influenced the Ca²⁺/P ratio due to the calcium attached to pericarp. At 82 and 92°C, maximum values of Ca²⁺/P ratio were detected in NCF at 7 hr of steeping time and at 9 hr at 72°C. These results can be used with industrial purposes to assess a maximum calcium‐to‐phosphorus ratio, and at the same time, to avoid the loss of pericarp to increase the functional properties of NCF.     

Changes in Nixtamalized Corn Flour Dependent on Postcooking Steeping Time

We studied the effect of steeping time on various physical and chemical properties of maize flour prepared by the traditional nixtamalization process as well as in oversaturated calcium ion conditions. The calcium content of the corn flour was measured by atomic absorption spectroscopy and was correlated with X‐ray diffraction, viscosity, and pH measurements. Calcium content of the flour showed a nonlinear dependence on steeping time, with a local calcium maximum occurring at ≈7 hr. The pH level of the corn flour increased with steeping time, thus roughly following the time trend shown by the steeping time dependence of the calcium content. Flour crystallinity and peak viscosity of water suspensions of the flour reached maximal values at ≈7–9 hr of steeping, in agreement with manufacturing experience showing that these are appropriate steeping times to prepare tortillas with the desirable rheological and organoleptic properties.     

Dry Matter Loss During Nixtamalization of a White Corn Hybrid: Impact of Processing Parameters

Nixtamalization is the primary step in the production of products such as corn chips, tortilla chips, tacos, and corn tortillas. The process involves cooking and steeping of corn in lime and excess water to produce nixtamal. Commercial nixtamalization results in 5–14% corn solids loss in the liquid generated during cooking‐steeping and washing. Loss of corn solids not only causes economic loss to corn processors but also creates costly waste and wastewater disposal problems. Empirical results show that, besides corn kernel characteristics, processing parameters are critical variables influencing corn solids loss and effluent pH during nixtamalization. This work was designed to systematically study the impact of processing parameters on corn dry matter loss and effluent pH generated during nixtamalization by using response surface methodology. Corn cooking temperature and lime concentration were more critical factors influencing corn solid loss than were cooking and steeping time. In the ranges studied, total dry matter loss increased only up to ≈8 hr of steeping and then leveled off. By optimizing the nixtamalization protocol, effluent dry matter loss can be minimized.     

Selective Nixtamalization of Fractions of Maize Grain (Zea mays L.) and Their Use in the Preparation of Instant Tortilla Flours Analyzed Using Response Surface Methodology

Using a continuous decorticating machine, white dent corn was efficiently separated, after brief steeping in water, into two fractions: the first (12.5%) consisting mainly of pericarp, germ, and tip cap (PGT); the second (87.5%) consisting of endosperm. Nixtamalization of the maize fractions in the presence of 0.6% (w/w) lime caused an increase in the hot‐paste viscosity at 90°C, while nixtamalization of PGT at lime inputs <0.6% (w/w) resulted in decreased viscosity. Three domains were found for the viscosity of nixtamalized endosperm at 90°C: lower concentrations of lime (< 0.15%, w/w) resulted in lower viscosity values; increased lime (0.15% – <0.3%, w/w) increased the viscosity values; and a lime concentration of 0.3% (w/w) resulted in a lower viscosity value. The response variables (water absorption index, water solubility index, initial viscosity, and viscosity at 90°C for nixtamalized PGT, and compression force and compression area of tortillas) indicated that the mathematical models fit the experimental data and the variance of the models was highly significant. Tortillas of good functional characteristics similar to tortillas produced by the traditional process were obtained when 5% nixtamalized fractions of PGT were blended with 95% nixtamalized endosperm.     

Development of Laboratory Techniques to Mimic Industrial‐Scale Nixtamalization

A laboratory nixtamalization process was developed to imitate larger scale cooking/steeping conditions. Corn (45 kg) was cooked in a pilot plant gas‐fired cook/steep tank and temperature was monitored every 30 sec. Cooling and heating rates were mimicked in the laboratory using a digital temperature programmable hot plate that adjusted grain‐water‐lime temperature changes at a specified rate. A Response Surface Central Composite Design was used to model pasting and thermal properties of nixtamal and masa as a function of cooking temperature (86–96°C), cooking time (20–40 min), and steeping time (3–11.77 hr). Nixtamal and masa moisture, dry matter loss, nixtamal and masa RVA peak temperature, shear thinning, nixtamal peak viscosity, masa final viscosity, nixtamal and masa DSC enthalpy peak and end temperatures, and nixtamal onset temperature were explained by the same regression terms for results obtained using both processes conditions. The intercept and slopes of the fitted models for the pilot plant and laboratory responses were not significantly different (P < 0.05). The laboratory method can be used to mimic larger scale processing over a wide range of nixtamalization conditions.     

Fate of Maize DNA During Steeping,Wet-Milling,and Processing

The fate of DNA during steeping, wet-milling, and subsequent processing of maize was examined using a sensitive polymerase chain reaction (PCR-based) detection system. The system used specific amplification of maize DNA sequences by primers generated toward plant nuclear- and chloroplast-encoded genes. The PCR method facilitated analysis of DNA content in food products, which is an important issue in use of genetically modified organisms. In a conventional laboratory wet-milling countercurrent steep system, DNA was detected in maize kernels throughout the process but was not found in steepwater. After kernels were wet-milled, DNA was detected in the starch, germ, coarse fiber, and wet gluten fractions but not in the fine fiber fraction. When dried by heating at 135°C for 2 hr, DNA was degraded to undetectable levels in the wet-milled gluten fraction and hydrated kernels. DNA was not detected in feed pellets, starch, dextrose, sorbitol, or high-fructose maize syrup made from industrial wet-milled samples. Although DNA could be detected in laboratory wet-milled fractions, some degree of degradation occurred after extended exposure to steepwater. Countercurrent steepwater samples from the later stages of the steeping process were able to degrade DNA. The level of DNA degradation appeared to correspond to the presence of sulfur dioxide and may represent a physiochemical rather than an enzyme-mediated process. Our results indicate that some steps in the steeping and wet-milling process can degrade maize genomic and plastid DNA.     

Assessment of Corn Quality for Nixtamalization: Development of a Convenient Bench‐Top Cooking Method

A convenient small‐scale laboratory method that can be used to simultaneously analyze multiple samples was developed to rapidly assess suitability of corn for nixtamalization. This new 100 g method was developed based on a previously reported 500 g laboratory process that has been shown to mimic the industrial nixtamalization process. The two methods were compared for nixtamal moisture, dry matter loss, degree of pericarp removal, and gelatinization properties of the cooked corn. The heating and cooling profiles of the 100 g method were developed using the 500 g method, by monitoring temperature every 30 s during cooking and steeping. Nixtamalization was conducted with a 1:4 corn/water ratio, with 1% lime. A response surface central composite design was used to model a wide range of processing conditions for the two methods: cook temperature (80–95°C), cook time (3–40 min), and steep time (2–12 h). Parameter estimates and response surfaces were compared, and predictive models were fitted. The response surface models for the two methods were not significantly different for nixtamal moisture, dry matter loss, and gelatinization enthalpy; there was an overlap of the 90% Bonferroni confidence intervals (P < 0.05, r ² > 0.7). The bench‐top 100 g nixtamalization process can successfully mimic the 500 g method over a wide range of processing conditions.     

Nixtamalized Instant Flour from Corn (Zea mays L.) Meal: Optimization of Nixtamalization Conditions

The present investigation provides a new method for the nixtamalization process wherein corn endosperm fractions (corn meal) are treated in an alkaline solution that yields quality masa or instant masa flour like traditional nixtamalization process (alkaline cooking of corn with lime). The objective of this work was to determine the best combination of nixtamalization process variables for producing nixtamalized instant flour (NIF) from corn meal. Nixtamalization conditions were selected from factorial combinations of process variables including nixtamalization time (NT 8–22 min) and cooking temperature (CT 78–88°C). A central composite rotable experimental design was chosen. Lime concentration was 1% (10 g of Ca(OH)₂/L of water) and ratio of corn meal to cooking medium was 1:4. At the end of each cooking, each treatment was steeped for 5 hr at room temperature (25°C). Nixtamalized corn meal was dried (55°C/12 hr) and milled to pass through 80 U.S. mesh to obtain NIF. Response surface methodology (RSM) was applied as an optimization technique over four response variables: masa firmness (MF), masa adhesiveness (MA), tortilla cutting force (CF), and tortilla tensile strength (TS). Predictive models for response variables were developed as a function of process variables. Conventional graphic methods were applied to obtain response variable values similar to the control (MASECA). Contour plots of each response variable applied superposition surface methodology to obtain a contour plot for observation and for selecting the best combination of nixtamalization time (NT 15 min) and cooking temperature (CT 83°C) for producing an optimized NIF from corn meal. Values of MF, MA, CF, and TS obtained from the predictive models were compared with those derived from experimental tests; a close agreement (coefficient of variance < 10%) between both values was observed.     

Relationships Between the Microstructure,Physical Features,and Chemical Composition of Different Maize Accessions from Latin America

Chemical composition (moisture, total lipids, protein, and apparent amylose) and some physical features (1,000 kernel weight, hardness, and anatomical composition) were determined in 71 accessions representing races of maize from Latin America. Their microstructural characteristics (size and compaction of endosperm cell bodies, pericarp thickness, horny‐floury endosperm ratio, and morphology and size of starch granules) were also evaluated using environmental scanning electron microscopy (ESEM). Compaction was the most important microstructural feature of the maize kernels, representing kernel hardness. Highly compact kernels tended to be hard, with high protein, pericarp, and hard‐endosperm content and high pericarp thickness, but with low moisture, amylose content, and kernel weight and size. The opposite was observed in the least compact kernels. Highly compact kernels tended to have small, polygonal starch granules (<10 μm), while the least compact kernels contained large, spherical granules (>10 μm). These results suggest that microstructure is responsible for the physical features of maize kernels and that microstructure is related to chemical composition.     

Intermittent Milling and Dynamic Steeping Process for Corn Starch Recovery

A procedure that reduces diffusional limitations by periodically milling the corn to reduce particle size and stirring the ground mash in the presence of sulfur dioxide (SO₂) and lactic acid was developed. The process, called intermittent milling and dynamic steeping (IMDS), includes three main stages: initial soaking (a short-time immersion in water) of whole kernels, initial cracking of the partially hydrated kernels, and dynamic steeping with interspersed milling. This study evaluated the three stages of the process separately, evaluating the effect of variables on each stage of the process. Corn fractions yield (germ, fiber, gluten, starch) were used to decide the best conditions for the soaking and steeping stages, and germ damage was used to determine the best kernel cracking method. Starch, gluten, and germ yields were not affected by soak temperatures (52–68°C) or soak time (1–3 hr). A temperature of 60°C was chosen for soaking because it increased the rate of kernel hydration without gelatinizing starch, which happens at higher temperatures. A 2-hr soak time was preferred because there was less fiber in the germ fraction and less germ damage was observed. Although there were no advantage to using SO₂ or lactic acid in the soak water, the presence of these compounds during dynamic steeping enhanced starch yield. The starch yield for 3 hr of dynamic steeping was not statistically different from the starch yield for a 7.5-hr dynamic steep. The Bauer mill was preferred over the use of a roller mill or a commercial grade Waring blender for kernel cracking. The IMDS process produced, on an average, 1 percentage point more starch than the conventional 36-hr steeping process. Total steep or kernel preparation time was reduced from 24–40 hr for conventional wet-milling to 5 hr for the IMDS process.     

Effects of Alkali Debranning,Roller Mill Cracking and Gap Setting,and Alkali Steeping Conditions on Milling Yields from a Dent Corn Hybrid

Starch yield was significantly affected by all three main unit operations in alkali wet‐milling (debranning, roller milling, and steeping). The conditions for the three unit operations were studied using a single hybrid. Studies on debranning showed that optimal separation between pericarp and corn endosperm was obtained when corn was soaked in a 1.5–2% NaOH solution at 85°C for 5 min. Passing debranned corn through smooth roller mill once or twice did not affect the product yields, but passing the corn through the roller mill three times decreased the germ yield because of a large amount of broken germ. A 62% higher processing rate could be achieved when passing corn through the mill twice than by passing it through the mill once. The gap should be set at 2.0 mm when passing corn through the mill once, and it should be set at 3.5 mm for the first pass and 2.0 mm for the second pass when passing corn through the mill twice. Starch yield was more sensitive to NaOH concentration and steep temperature than to steep time. The highest starch yield was obtained when steeping corn in 0.5% NaOH for 1 hr at 45°C.     

Analysis of Quality Protein Changes in Nixtamalized QPM Flours as a Function of the Steeping Time

This study showed the protein changes in Quality Protein Maize (QPM H‐368C) during the traditional nixtamalization process as a function of the steeping time from 0 to 15 hr. Protein content (N × 6.25), pH, protein fractionation, reactive lysine, essential amino acids, and protein digestibility were analyzed to explain the protein quality modifications in nixtamalized corn flours (NQF). The thermoalkaline process increased significantly (P ≤ 0.05) the protein content (5.57 ± 0.86%) in NQF obtained at 3, 5, 7, 9, 11, 13, and 15 hr of steeping time compared with native corn or corn without treatment (NC). The pH values of NQF were not proportional to the steeping time and significantly different (P ≤ 0.05) between them. At 5 hr critical steeping time, the total lysine and reactive lysine content decreased severely (36 and 32%, respectively) with statistical differences (P ≤ 0.05) compared with NC. On the other hand, the tryptophan content decreased significantly (P ≤ 0.05) at steeping times of 5–15 hr (38.70 ± 6.7%) compared with NC. The changes in the lysine and tryptophan content were not proportional to the steeping time. The protein recovery in the albumin and globulin fraction diminished (P ≤ 0.05) with respect to raw corn. The protein recovery for γ‐zeins, glutelin‐like proteins, glutelins, and residue increased. A significant (P ≤ 0.05) decrease was found in the essential amino acids in NQF with 3–7 hr of steeping time compared with NC. Equally important was the reduction in protein digestibility observed in NQF steeped at long steeping times (11–15 hr) with significant (P ≤ 0.05) differences compared with NC. The protein solubility distribution along the steeping step and the essential amino acids location, specifically lysine in corn kernel, could explain partially the protein quality changes observed in this research. Finally, these results contribute to reconciling discrepancies associated with the protein quality modifications in nixtamalized corn reported previously in literature.     

Effect of the Nixtamalization Process on the Dietary Fiber Content,Starch Digestibility,and Antioxidant Capacity of Blue Maize Tortilla

Nixtamalization is an ancient process developed by the Mesoamerican cultures. Initially, volcanic ashes were used and then calcium hydroxide in commercial production, and more recently nixtamalization with calcium salts (NCS) has been proposed. The aim of this study was to evaluate the effect of NCS on carbohydrate digestibility and antioxidant capacity in the elaboration of blue maize tortillas. NCS in blue tortillas showed a high amount of total dietary fiber (14.27 g/100 g), the main fraction being insoluble dietary fiber. The contents of resistant starch and slowly digestible starch did not change with the nixtamalization process. The predicted glycemic index value was lower in blue tortillas with the NCS process (58) than with the traditional nixtamalization process (71). In general, NCS in blue tortillas presented a higher antioxidant capacity than traditional tortillas (ferric reducing antioxidant power method), indicating that phenolics present in blue maize maintain their activity after cooking. It can be concluded that the nutraceutical features (high dietary fiber content and antioxidant capacity) of blue maize tortillas are enhanced when they are elaborated with the NCS process.     

Effect of nixtamalization (Alkaline cooking) on fumonisin-contaminated corn for production of masa and tortillas

Studies were undertaken to determine the fate of the mycotoxins, fumonisins, during the process of alkaline cooking (nixtamalization), using normal-appearing corn that was naturally contaminated with fumonisin B(1) (FB(1)) at 8.79 ppm. Corn was processed into tortillas, starting with raw corn that was cooked with lime and allowed to steep overnight; the steeped corn (nixtamal) was washed and ground into masa, which was used to make tortillas. Calculations to determine how much of the original fumonisin remained in the finished products took into consideration that FB(1) will be converted to hydrolyzed fumonisin B(1) (HFB(1)) by the process of alkaline cooking. All fractions, including steeping and washing water, were weighed, and percent moisture and fumonisin content were determined. Tortillas contained approximately 0.50 ppm of FB(1), plus 0.36 ppm of HFB(1), which represented 18.5% of the initial FB(1) concentration. Three-fourths of the original amount of fumonisin was present in the liquid fractions, primarily as HFB(1). Nixtamalization significantly reduced the amount of fumonisin in maize.     

Effect of Broken Corn Levels on Water Absorption and Steepwater Characteristics

Broken corn created by grounding sound corn kernels was added back at levels of 0, 4, 8, 12, or 16%, by weight, to whole kernels of three corresponding hybrids: FR27 × FRMo17 (a soft endosperm corn), FR618 × FR600 (amedium‐hard endosperm corn), and FR618 × LH123 (a hard endosperm corn). The samples had been dried from 28% moisture content to 15% moisture content either by using ambient air at ≈25°C or at 110°C. Samples were steeped for 36 hr at 52°C in 0.15% sulfur dioxide and 0.5% lactic acid steeping solution. The steepwater characteristics, such as water absorption, solids and protein content in the steepwater, and steepwater pH, were measured by periodic sampling and analyzed. Broken corn level has a significant effect on the amount of solids released during steeping and steepwater protein content for all samples. Both steepwater solids and protein content increased linearly as broken corn content increased. Corn drying temperature, kernel hardness, and interactions between drying temperature and kernel hardness has a significant effect on steepwater solids and protein content and steepwater pH in both broken and unbroken corn. Corn dried at low temperature released more soluble solids and protein into the steepwater than corn dried at high temperature. Soft endosperm and medium‐hard endosperm corn released more soluble solids and protein into the steepwater than hard endosperm corn. Soft endosperm corn resulted in a higher steepwater pH than medium‐hard and hard endosperm corn. No significant effect of broken corn content on final moisture content of steeped corn and steepwater pH was observed.