Effects of Storage Temperature and Kernel Physical Condition on Popping Qualities of Popcorn Hybrids

Effect of storage temperature before popping and kernel physical properties on popping characteristics were studied using popcorn (Zea mays L.) hybrids harvested in 1997. Popped volume (PV), unpopped kernel ratio (UPK), and popping times were measured from 250 g of moisture‐adjusted kernels stored at 30, 1, and −29°C for one month. Maximum popped volume (MPV) and minimum unpopped kernel ratio (MUPK) at the corresponding optimum moisture contents (OMC) were mathematically calculated from PV, UPK, and moisture content values. MPV was significantly affected by storage temperature before popping. Hybrid significantly affected MPV and MUPK. Moisture content, storage temperature, and hybrid significantly varied popping time of the popcorn hybrids, with moisture content being the most important. Correlation results showed that MPV was negatively correlated with unsound kernel ratio, UPK, and popping time. Moisture adjustment of intact kernels should be done at different storage conditions; high temperature storage required higher moisture than low temperature storage to give the best outcome.     

Effect of Kernel Size,Location, and Type of Damage on Popping Characteristics of Popcorn

Popping characteristics, specifically expansion volume and popping time, were studied for damaged popcorn. A single variety of commercial undamaged yellow popcorn was separated into four size fractions (D < 4.36, 4.36 < D < 5.16, 5.16 < D < 5.95, and D > 5.95 mm) by screening with round-hole sieves. Kernels were damaged using a razor knife by either slicing a 2-mm diameter piece of the endosperm or the germ or by cutting through the pericarp and seed coat into the endosperm or the germ ≈2 mm. A total of five combinations of location and damage were studied (tip cap removed, side cut, side sliced, germ cut, and germ sliced) for each kernel size. A control sample with no damage was also analyzed for each size fraction. All of the damaged kernels (regardless of type of damage) popped, but they had expansion volumes 9.1–47.5% smaller than those of undamaged kernels. The expansion volume of damaged kernels increased by 52.5–85.7%, depending on the damage, when the size of the kernel increased from <4.36 mm to >5.95 mm. Removing the tip cap and slicing through the germ caused less loss of expansion volume than did other types of damage. Damaged popcorn kernels had faster popping times (12.2–24.0 sec) than did undamaged kernels (30.9–34.6 sec). Popping times increased with increasing kernel size for all types of damage.     

Effect of Hybrid and Physical Properties of Individual Popcorn Kernels on Expansion Volume

The relationships between expansion volume and physical properties of three varieties of popcorn kernels were investigated on a single kernel basis. Physical properties studied were kernel size, kernel sphericity, and kernel density. Methods of measuring densities and popped volumes of individual popcorn kernels were developed. Popcorn kernels were separated into seven kernel sizes by screening with round‐hole sieves. Thirty kernels from each of three kernel sizes (4.76 < D < 5.16, 5.56 < D < 5.95, 6.35 < D < 6.75 mm) of three popcorn varieties were individually measured for sphericity, density, and popped volume. Density and sphericity measures of popcorn kernels showed little variability. Variety, kernel sphericity, and kernel density had minor effects on expansion volume. Kernel size had no effect. There were no strong linear relationships (R² = 0.28) among expansion volume and physical properties of the three varieties of popcorn kernels. The variety with the highest mean density and the highest mean sphericity showed a tendency of producing higher mean expansion volumes.     

Suitability of Different Starches for Production of Kuanfen (Chinese Flat Starch Noodles)

Starches from potato, corn, sweet potato, and rice were compared with mung bean starch for their suitability for producing kuanfen, Chinese flat starch noodles. Significant differences were found in the chemical composition and swelling power among starches (P < 0.05). Maximum tensile stress and maximum tensile strain was highest for kuanfen made from mung bean starch and sweet potato starch, respectively. Higher work was needed to break kuanfen made from mung bean and sweet potato starches. Kuanfen made from mung bean starch was most favored by panelists, followed by those from sweet potato starch. General acceptability of kuanfen correlated positively and significantly with chewiness, cohesiveness, and elasticity of the noodles. For predicting sensory acceptability of kuanfen using instrumental methods, correlation was performed between sensory variables and tensile parameters. Results showed that work-to-break correlated significantly with chewiness, elasticity, and general acceptability while maximum tensile strain correlated significantly with sensory cohesiveness. Therefore, both of these two tensile parameters could be useful for predicting the textural properties of kuanfen.     

Isolation and Characterization of a Soluble Branched Starch Fraction from Corn Masa Associated with Adhesiveness

A water‐soluble starch fraction isolated from corn masa and identified by HPSEC as predominantly fragmented amylopectin was highly correlated in amount to both masa adhesiveness (r = 0.890, P < 0.01) and cook time (r = 0.957, P < 0.01). The molecular weight of the component ranged from approximately 6.4 × 10⁵ to 1.2 × 10⁶, based on HPSEC column calibration with pullulan standards. Debranching with isoamylase illustrated that the structure of the soluble masa starch component was highly branched with a similar debranched profile to native amylopectin. Further analysis revealed that a minor amount of amylose was present in the second half of the broad HPSEC peak containing the fragmented amylopectin component. There was a high second‐order correlation (r = 0.998, P < 0.01) between the absorbance at the wavelength of maximum absorbance (λ_max) of the soluble fraction from masa (527–532 nm) and masa adhesiveness, indicating that a rapid assay for masa adhesiveness could easily be developed. Increasing the shear at the stone mill by reducing the gap setting between the stones, increased the amount of fragmented amylopectin. The high correlation between the amount of fragmented amylopectin and masa adhesiveness suggests that this fraction is the main determinant of masa adhesiveness. The amount of fragmented amylopectin can be controlled by cook time and gap between the stone plates of the mill.     

Structural Properties of Starch Fractions Isolated from Normal and Mutant Corn Genotypes Using Different Methods

The objectives of this research study were to isolate, evaluate, and compare the fine structures of starch fractions obtained from a wild‐type (normal) corn starch and amylose‐extender25, dull39, sugary2, and sugary1 corn mutants in the same genetic background using three different fractionation procedures based on gel‐permeation chromatography or alcohol‐precipitation methods. Starch fractions obtained from each of the three methods were enzymatically debranched and analyzed using high‐performance anion‐exchange chromatography with a postcolumn amyloglucosidase reactor and a pulsed amperometric detector. The separations were performed by fractionation on a GPC column, by precipitation with 1‐butanol, and by preferential precipitation with 1‐butanol and isoamyl alcohol. Using any of these methods, no apparent differences in the molecular weight distributions of amylopectin or of amylose among the different starches were observed. The proportions of branch chain lengths of the starch components obtained by the various fractionation methods were very similar among methods for each of the starch types analyzed, such as the predominance of long branch chains in ae25 corn and that of the short branch chains in su2 corn. Overall, the effect of the corn mutations was more important to the differences observed among the starch types than was the method of fractionation used.     

CRITICAL DEFICIENCY LEVEL OF ZINC FOR CORN ON CALCAREOUS SALT-AFFECTED SOILS IN CENTRAL IRAN

A greenhouse experiment with 11 soil series and two zinc (Zn) rates (0 and 15 mg Zn kg^?1 as zinc sulfate) was performed to determine critical deficiency level of Zn for corn (Zea mays L.) on calcareous salt-affected soils in central Iran. In addition, the most important soil properties affecting Zn phytoavailability were determined. Critical Zn deficiency levels were determined using the Cate-Nelson and Mitscherlich procedures. In most soils, application of Zn increased the dry matter yield, and Zn concentration and content in the shoot and root of corn. A positive correlation was observed between the soil electrical conductivity (EC) with Zn concentration in shoots, roots and whole plant while shoot Zn content was negatively correlated with buffer capacity of Zn in soil. Critical deficiency levels of Zn in soil for corn based on the Cate-Nelson and Mitscherlich method were 1.35 and 1.23 mg kg^?1 for diethylenetriaminepentaacetic acid (DTPA)-extracted soil Zn, respectively.     

Comparison of Methods for Amylose Screening Among Amylose‐Extender (ae) Maize Starches from Exotic Backgrounds

Breeding for high‐amylose corn requires a rapid analytical method for determining starch amylose so that generating wet chemistry values does not pose a major limitation in the volume of materials that can be screened. Two methods for determining apparent amylose content (AAC) were examined and compared with an iodine‐binding method involving the solubilization of isolated starch in a sodium hydroxide solution (method 1). These methods included one based on near‐infrared transmittance spectroscopy (NIRT) (method 2) and another iodine‐binding method involving the solubilizing of starch from ground whole corn with a DMSO‐iodine solution (method 3). These methods were chosen because, aside from initial set up costs, they are relatively rapid and inexpensive to perform. The materials evaluated consisted of various exotic corn populations including plant introductions and experimental materials generated from the Germplasm Enhancement of Maize (GEM) project. Crosses were made between these materials and a Corn Belt dent hybrid (OH43 × H99) converted with the amylose‐extender (ae) allele. Grain from F2 ears, presumed to be homozygous for the ae allele based on visual selection of mutant kernels on F1 ears from which they were planted, were then evaluated to identify possible modifiers of ae conditioning high starch AAC. From a total of 1,006 F2 ears, a core set consisting of 155 samples was established and only these were subjected to starch AAC analysis, using all three methods to compare the methods. Method 2 showed poor correlation to method 1 (r = 0.88), however, NIRT did appear to discriminate between samples converted to ae vs. those with a normal or possibly segregating endosperm type. Method 3 showed a slightly better correlation with method 1 (r = 0.92) and appeared to more fully discriminate among samples with AAC values >65% from those at ≈55%. Results from this study suggest that NIRT may be useful when a quick screening method is needed to discriminate mutant from nonmutant genotypes within grain samples of exotic germplasm especially when visual identification is difficult. In addition, method 3 could be used to replace the more time‐consuming method 1 when trying to identify high AAC levels among ae genotypes, even though some inconsistency was observed between the two methods. Finally, this study revealed that exotic germplasm may be an important source of new modifiers to the ae allele because values as high as 70% AAC were identified.     

Relationship Between Solvent Retention Capacity and Protein Molecular Weight Distribution,Quality Characteristics,and Breadmaking Functionality of Hard Red Spring Wheat Flour

This research aims to investigate the relationship between the solvent retention capacity (SRC) test and quality assessment of hard red spring (HRS) wheat flour samples obtained from 10 HRS cultivars grown at six locations in North Dakota. The SRC values were significantly (P < 0.05) correlated with flour chemical components (protein, gluten, starch, and damaged starch contents, except arabinoxylan); with farinograph parameters (stability [FST], water absorption, peak time [FPT], and quality number); and with breadmaking parameters (baking water absorption [BWA], bread loaf volume [BLV], and symmetry). Differences in locations and cultivars contributed significantly to variation in quality parameters and SRC values. Suitability of SRC parameters for discriminatory analysis of HRS wheat flour is greatly influenced by molecular weight distribution (MWD) of SDS‐unextractable proteins. SRC parameters, except for sucrose SRC, showed significant (P < 0.01) and positive correlations with high‐molecular‐weight (HMW) polymeric proteins in SDS‐unextractable fractions, whereas only lactic acid SRC exhibited significant (P < 0.01) correlations with low‐molecular‐weight polymeric proteins. HMW polymeric proteins also exhibited positive associations with FPT, FST, BWA, and BLV. The discrepant variation in association of SRC parameters with respect to MWD of SDS‐unextractable proteins could improve segregation of HRS wheat flour samples for quality.     

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.     

Comparison of root system architecture and rhizosphere microbial communities of Balsas teosinte and domesticated corn cultivars

The progenitor of maize is Balsas teosinte (Zea mays subsp. parviglumis) which grows as a wild plant in the valley of the Balsas river in Mexico. Domestication, primarily targeting above-ground traits, has led to substantial changes in the plant's morphology and modern maize cultivars poorly resemble their wild ancestor. We examined the hypotheses that Balsas teosinte (accession PI 384071) has a) a different root system architecture and b) a structurally and functionally different rhizosphere microbial community than domesticated cultivars sweet corn (Zea mays subsp. mays accession PI 494083) and popping corn (Zea mays subsp. mays accession PI 542713). In a greenhouse experiment, five plants from each corn variety were grown in individual pots containing a Maury silt loam – perlite (2:1) mixture and grown to the V8 growth stage at which rhizosphere bacterial and fungal community structure was assessed using terminal restriction fragment length polymorphism and fatty acid methyl ester analysis. Functional characteristics of the rhizosphere were assayed by examining the potential activity of seven extracellular enzymes involved in carbon, nitrogen and phosphorus cycling. Root system architecture was characterized by root scans of sand grown plants at the V5 growth stage. Compared to the control the sweet corn rhizosphere had different bacterial and fungal community structure, decreased fungal diversity and increased bacterial abundance. Teosinte caused a significant change in the rhizosphere bacterial and fungal community structure and increased bacterial abundance, but no significant decrease in bacterial or fungal diversity where the former was found to be significantly greater than in the sweet corn rhizosphere. Popping corn did not trigger significant changes in the bacterial or fungal diversity and bacterial abundance in the soil. The individual popping corn plants changed the bacterial and fungal communities in different directions and the overall effect on community structure was significant, but small. Of the enzymes analyzed, potential N-acetylglucosaminidase (NAG) activity was found to contributed most to the differentiation of teosinte rhizosphere samples from the other corn varieties. The teosinte root system had proportionally more very fine (diameter < 0.03 mm) roots than popping corn and sweet corn and it developed the highest root to shoot dry weight ratio, followed by popping corn. Sweet corn had significantly lower average root diameter than popping corn and teosinte and grew proportionally the least below-ground dry mass. The results allude to functional and structural differences in the rhizosphere microbial communities of the corn varieties that, with additional research, could lead to useful discoveries on how corn domestication has altered rhizosphere processes and how plant genotype influences nutrient cycling.     

Molecular Characterization of Corn Starch Using an Aqueous HPSEC‐MALLS‐RI System Under Various Dissolution and Analytical Conditions

Molecular characteristics based on absolute weight‐average molecular weight (M_w) and z‐average radius of gyration (R_g) of normal corn starch were analyzed by high‐performance size‐exclusion chromatography (HPSEC) attached to multiangle laser‐light scattering (MALLS) and refractive index (RI) detectors under different starch dissolution and analytical conditions. Autoclaving (121°C, 20 min) or microwave heating (35 sec) provided better HPSEC recovery and higher M_w for starch molecules than simple dissolution in hot water. The M_w for the autoclaved corn amylopectin and amylose fractions separated with a TSK G5,000 column at 60°C were 201 × 10⁶ and 3.3 × 10⁶, respectively. The specific volume for gyration (SV_g) calculated from M_w and R_g could be used for the comparison of molecular compactness which was inversely related to the degree of branching. The SV_g values of amylopectin and amylose fractions in the chromatogram (TSK G5,000, autoclaved for 20 min) were 0.092 and 0.529, respectively. But a portion (20–30%) of large amylopectin molecules did not pass the injection membrane filter (3.0 μm) and the SEC column, resulting in incomplete recovery. The unfiltered portion varied according to the dissolution treatment. Homogenization (7,000 rpm, 5 or 10 min) of the starch solution improved the recovery of the amylopectin fraction, but significantly increased the M_w of the amylose fraction (17 × 10⁶). Sonication for 5 min degraded starch molecules. For accurate analysis of a native starch using an aqueous SEC, the starch should be fully dissolved with proper treatment such as autoclaving or microwaving, and the column should be improved for full recovery of large amylopectin molecules.     

Thermal Expansion of Flour-Water Dough Measured with a Dynamic Mechanical Analyzer

Thermal expansion of a wheat flour-water dough was measured with a dynamic mechanical analyzer (DMA) at a temperature scan range of 25 to 160°C, in 5°C/min increments. Dough water-absorption levels were increased from 50 to 70% (14% mb) in 4% increments. A standard breadbaking method was used, and loaf volume was measured for regression analysis. The thermal expansion pattern of flour-water dough during heating included four stages with changes in the thermal expansion coefficient: gas thermal expansion (GTE) (25–60°C), starch gelatinization-gluten matrix formation (GMF) (60–100°C), vapor pressure expansion (VPE) (100–120°C), and structure fixation-crust formation (SCF) (>120°C). The onset temperature (T_o) between each stage and the thermal expansion coefficient (C_e) of each stage were affected significantly by dough water content. The onset temperature () from GTE to GMF (the starting temperature of gelatinization of starch in dough) decreased from 68 to 55°C as water absorption increased from 50 to 70%. The thermal expansion coefficient () of flour-water dough during GMF was highly correlated (r² = 0.886) to bread loaf volume. The ratio () of thermal expansion coefficient during the GMF stage to the coefficient during the GTE stage also was significantly correlated (r² = 0.882) to baking volume. Thus, DMA measurement of dough thermal expansion has the potential to be a powerful method of predicting baking quality in cultivar screenings, baking simulations, and scale-up studies.     

不同类型玉米籽粒淀粉积累、相关酶活及基因表达差异分析

为探究不同类型玉米淀粉形成机理,对普通玉米、甜玉米、糯玉米淀粉积累、相关酶活及基因表达进行测定,分析不同类型玉米淀粉积累、相关酶活及基因表达之间的差异及相互关系。结果表明,不同类型玉米总淀粉和直链淀粉百分含量为:普通玉米>糯玉米>甜玉米,支链淀粉百分含量为:糯玉米>普通玉米>甜玉米,灌浆期间总淀粉和直链淀粉含量3个玉米类型间差异显著;灌浆期间,普通玉米各淀粉合成相关酶活性最高,甜玉米淀粉合成相关酶活性最低,糯玉米则介于普通玉米和甜玉米之间,但其GBSS酶活性很小。灌浆期间3个类型玉米除GBSS酶活性差异不显著外,其他淀粉合成相关酶活性差异显著;普通玉米淀粉合成相关基因表达量总体均高于甜玉米和糯玉米,甜玉米和糯玉米相关突变基因仍存在表达。表明不同类型玉米淀粉含量和组成上差异明显;普通玉米淀粉的形成需要淀粉合成相关酶相互作用,淀粉合成相关酶活性的缺失会改变淀粉组成;不同类型玉米淀粉合成相关基因表达差异显著,但都存在转录活性。对普通玉米进行相关性分析同时发现,淀粉的合成不仅受到转录调控,还受到转录后调控,淀粉的合成是淀粉合成各酶之间相互协调的结果。     

Thermal Properties of Corn Starch Extraction Intermediates by Differential Scanning Calorimetry

Thermal properties of corn starch extraction intermediates from four types of corn were studied using differential scanning calorimetry. Starch at four different stages of extraction, including a standard single-kernel starch isolation procedure and three starch extraction intermediates, was isolated from mature corn kernels of B73 and Oh43 inbreds and the mutants of waxy (wx) and amylose extender (ae) in an Oh43 background. Differences in thermal properties and moisture and protein contents of starch from the extraction stages were statistically analyzed. Most thermal properties (gelatinization and retrogradation onset temperatures, gelatinization and retrogradation ranges, gelatinization and retrogradation peak temperatures, gelatinization and retrogradation enthalpies, peak height index, and percentage of retrogradation) of starches extracted at stage 3 intermediate (a procedure that did not include a final washing step) were similar to those of starch extracted by the standard single-kernel isolation procedure. Values for gelatinization peak temperature, gelatinization enthalpy, and peak height index were different between the standard and the stage 3 intermediate. The values obtained from starches extracted at stage 3, however, were consistent and predictable, suggesting that this extraction intermediate might be used in screening programs in which many starch samples are evaluated. By using the stage 3 extraction, samples could be evaluated in three rather than four days and the procedure saved ≈0.5 hr of labor time. The other two starch extraction intermediates, which excluded filtering and washing or filtering, washing, and steeping, produced starch with thermal properties generally significantly different from starch extracted by the standard single-kernel isolation procedure.     

Laboratory Wet Milling of Corn: Milling Fraction Correlations and Variations Among Crop Years

Several coproducts result from fractionating corn in the wet‐milling process. Because small changes in product composition and milling characteristics can have a major impact on coproduct yields and values, testing is done to anticipate final product yields. Using small sample size and controlled conditions, a laboratory wet‐milling method proved to be a useful tool for wet milling and genetics industries. A wet‐milling process (100‐g batches) was used for data collection. Data collected during 11 years (1994–2004) were observed for samples used as benchmarks to verify process precision and accuracy and determine correlations among wet‐milling yields. More than 400 milling tests were performed on benchmark samples. Data from benchmark samples also were pooled. Coefficients of variation were low (<6%) for mean yields; year‐to‐year standard deviations of benchmark sample yield means were homogenous and implied precision of the procedure. Some differences were detected in mean yields among years (P ≤ 0.05) for benchmark data due to combined effects of hybrid and environment. A negative correlation (r = –0.58) was observed between starch and gluten yield for pooled benchmark data. Four years (2002–2005) of milling data from commercially available hybrids were analyzed using the milling procedure. For pooled commercial data, the correlation between starch and fiber yield was (r = –0.80); correlation between starch and gluten was (r = –0.76).     

Photodegradation of cassava and corn starches

The baking expansion properties of sour cassava starch (Polvilho azedo) are attributable to photochemical starch degradation induced by heterolactic fermentation after sun-drying. This study investigated the effects of UV irradiation on the different structural levels of cassava starch as compared to those of corn starch and dextrins. Photosensitive compounds excited at 360 and 290 nm in cassava starch were photodegraded when starch was exposed to sunlight or 360 nm irradiation. UV irradiation depolymerized cassava and corn starches, inducing modifications due, at least in part, to a mechanism involving free radicals. Lactic acid was also photodegraded. Photodegradation induced by UV absorption could have been due to fluorescent chromophores found in starches and nonfluorescent chromophores present in glucosidic units.     

Solvent Retention Capacity Values in Relation to Hard Winter Wheat and Flour Properties and Straight‐Dough Breadmaking Quality

Solvent retention capacity (SRC) was investigated in assessing the end use quality of hard winter wheat (HWW). The four SRC values of 116 HWW flours were determined using 5% lactic acid, 50% sucrose, 5% sodium carbonate, and distilled water. The SRC values were greatly affected by wheat and flour protein contents, and showed significant linear correlations with 1,000‐kernel weight and single kernel weight, size, and hardness. The 5% lactic acid SRC value showed the highest correlation (r = 0.83, P < 0.0001) with straight‐dough bread volume, followed by 50% sucrose, and least by distilled water. We found that the 5% lactic acid SRC value differentiated the quality of protein relating to loaf volume. When we selected a set of flours that had a narrow range of protein content of 12–13% (n = 37) from the 116 flours, flour protein content was not significantly correlated with loaf volume. The 5% lactic acid SRC value, however, showed a significant correlation (r = 0.84, P < 0.0001) with loaf volume. The 5% lactic acid SRC value was significantly correlated with SDS‐sedimentation volume (r = 0.83, P < 0.0001). The SDS‐sedimentation test showed a similar capability to 5% lactic acid SRC, correlating significantly with loaf volume for flours with similar protein content (r = 0.72, P < 0.0001). Prediction models for loaf volume were derived from a series of wheat and flour quality parameters. The inclusion of 5% lactic acid SRC values in the prediction model improved R² = 0.778 and root mean square error (RMSE) of 57.2 from R² = 0.609 and RMSE = 75.6, respectively, from the prediction model developed with the single kernel characterization system (SKCS) and near‐infrared reflectance (NIR) spectroscopy data. The prediction models were tested with three validation sets with different protein ranges and confirmed that the 5% lactic acid SRC test is valuable in predicting the loaf volume of bread from a HWW flour, especially for flours with similar protein contents.     

Batch Steeping of Corn: Effects of Adding Lactic Acid and Sulfur Dioxide at Different Times on Starch Yields,Protein Contents,and Starch Pasting Properties

The effect of adding lactic acid and sulfur dioxide at different times from the start of batch steeping on corn starch yields was studied. Five commercial hybrids were steeped with 0.5% lactic acid or 0.2% sulfur dioxide added over the first 15 hr of steeping and wet-milled following a 100-g corn wet-milling procedure. No significant differences were observed in starch yields when lactic acid was added to the steep solution (SO₂ and water) from 0 hr (start of steeping) to 15 hr. Addition of SO₂ to the steep solution (lactic acid and water) resulted in significantly higher average starch yields when SO₂ was added between 5 and 15 hr compared with addition at 0 hr (SO₂ and lactic acid for full 24 hr of steeping). Based on the results of the first experiment, a second experiment was done in which one of five original hybrids was steeped for 24 hr, during which lactic acid or SO₂ was added until 23.9 hr (i.e., 5 min before milling) after the start of steeping. Similar results were found in the second experiment. Residual protein in starch samples did not exceed 0.85%. Steepwater protein content decreased with delays (16–20 hr) in adding either chemical to the steep solution. A significant effect on starch pasting properties of chemicals and duration of chemicals in steep-water was observed. Testing these findings using a larger scale (1,000 g) corn wet-milling procedure produced results similar to those obtained with the 100-g corn wet-milling procedure.