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.     

Study of Calcium Ion Diffusion in Components of Maize Kernels During Traditional Nixtamalization Process

Our report shows the calcium ion diffusion process through the different parts of maize kernels (pericarp, endosperm, and germ) during the traditional nixtamalization process as a function of steeping time (t) 0–24 hr. The cooking step of the nixtamalization process used 3 kg of maize kernels in 6L of water and 2% calcium hydroxide (w/w). The cooking temperature was 92°C for 40 min. The calcium content of the samples was measured using atomic absorption spectroscopy. We found that the whole instant corn flour, pericarp, endosperm, and germ, had a nonlinear relationship to steeping time, showing a local maximum at 9 hr. Analysis of the different parts of the nixtamalized kernels showed that in short steeping times (0–5 hr) calcium diffusion took place mainly in the pericarp. Calcium diffusion in the endosperm and germ occurred gradually over longer steeping times. However, the physical state of the kernels (broken kernels) accelerated the diffusion process. Calcium diffusion occurred first in the pericarp, followed by the endosperm and germ. Immediately after cooking (t = 0 hr), we found a 1.148% calcium content in the pericarp, 0.007% in the germ, and 0.028% in the endosperm. After 24 hr of steeping, the calcium contents were 2.714% in the pericarp, 0.776% in the germ, and 0.181% in the endosperm. In another study, the calcium content in the endosperm was measured by first separating the 10% from the outermost, followed by another 10% from the next endosperm tissue, and concluding with the remaining 80%. Calcium ions were present mainly in the outermost layers of the endosperm. The damaged kernels steeped for more than 5 hr showed greater calcium concentrations than the undamaged counterparts.     

Assessing Degree of Cook During Corn Nixtamalization: Impact of Processing Variables

Nixtamalization involves cooking and steeping corn in a lime solution, washing the corn (nixtamal), and stone grinding nixtamal to form a corn dough or masa. Masa is used to produce nixtamalized products (corn tortillas, tortilla chips, corn chips, taco shells, etc.) by forming and baking or deepfat frying. The degree of corn kernel cook determines the quality and texture of masa. Response surface methodology (RSM) was used as an experimental design to study the impact of process variables (cook temperature, cook time, initial steep temperature, and steep time) on the degree of cook measured using a Rapid Visco Analyser (RVA) and differential scanning calorimetry (DSC). RSM data exhibited significant (P < 0.005), although not predictive, linear models for RVA peak viscosity (r² = 0.63), setback (r² = 0.61), final viscosity (r² = 0.61), and peak time (r² = 0.57), indicating a dependence of these parameters on nixtamalization conditions. Peak viscosity, setback, and final viscosity increased linearly with steep time. DSC enthalpy (r² = 0.83) and peak temperature (r² = 0.89) of freezedried masa also exhibited significant (P < 0.0001) linear regression models with processing variables. DSC enthalpy increased with an increase in steep time, suggesting that starch is annealed during steeping. This study demonstrated that fundamental starch properties were altered on extended steeping during nixtamalization.     

Technological and Nutritional Properties of Flours and Tortillas from Nixtamalized and Extruded Quality Protein Maize (Zea mays L.)

Nixtamalized and extruded flours from quality protein maize (QPM, V‐537C) and tortillas made from them were evaluated for some technological and nutritional properties and compared with the commercial brand MASECA. Both QPM flours showed higher (P < 0.05) protein content, total color difference, pH, available lysine, and lower (P < 0.05) total starch content, Hunter L value, water absorption index, gelatinization enthalpy, resistant starch, and retrograded resistant starch than nixtamalized MASECA flour. Tortillas from nixtamalized and extruded QPM flours had higher contents of essential amino acids than tortillas from MASECA flour, except for leucine. Tortillas from processed QPM flours also showed higher (P < 0.05) values of the nutritional indicators calculated protein efficiency ratio (C‐PER 1.80–1.85 vs. 1.04), apparent and true in vivo protein digestibility (78.4‐79.1 vs. 75.6% and 76.4–77.4 vs. 74.2%, respectively), PER (2.30–2.43 vs. 1.31), net protein retention (NPR; 2.88–2.89 vs. 2.11), and protein digestibility corrected amino acid score (PDCAAS; 54–55 vs. 29% based on preschool children and 100 vs. 85% based on adults) than MASECA flour. The use of QPM for flour and tortilla preparation may have a positive effect on the nutritional status of people from countries where these products are widely consumed.     

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.     

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.     

Alkaline Processing (Nixtamalization) of White Mexican Corn Hybrids for Tortilla Production: Significance of Corn Physicochemical Characteristics and Process Conditions

Five white corn hybrids were processed (nixtamalized) using 10 different processing conditions; tortillas were prepared to establish relationships between corn composition, physical characteristics, and nixtamalization process or product properties. Corn hybrids were characterized by proximate analysis and by measuring Stenvert hardness, Wisconsin breakage, percent floaters, TADD overs, thousand‐kernel weight, and test weight. Corn characteristics were correlated with process and product variables (effluent dry matter loss and pH; nixtamal moisture and color; masa moisture, color, and texture; and tortilla moisture, color, and rollability). Process and product variables such as corn solid loss, nixtamal moisture, masa texture, and tortilla color were influenced not only by processing parameters (cook temperature, cook time, and steep time) but also depended on corn characteristics. Significant regression equations were developed for nixtamalization dry matter loss (P < 0.05, r² = 0.79), nixtamal moisture (P < 0.05, r² = 0.78), masa gumminess (P < 0.05, r² = 0.78), tortilla texture (P < 0.05, r² = 0.77), tortilla moisture (P < 0.05, r² = 0.80), tortilla calcium (P < 0.05, r² = 0.93), and tortilla color a value (P < 0.05, r² = 0.87).     

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.     

Functional and Digestive Characteristics of Extruded Rice Flour

Waxy (short grain), long grain, and parboiled (long grain) rice flours were extruded using three different temperatures and five different water feed rates. The water absorption and water solubility index of the extrudates was 0.67–5.86 and 86.45–10.03%, respectively. The fat absorption index was similar to that of unextruded flours with an average value of 0.96 g/g ± 0.12. Bulk density decreased with an increase in moisture, except waxy rice, which had a quadratic relationship. The viscosity profiles for long grain and parboiled rice were similar. Both initially increased in viscosity (>130 RVU), then decreased to ≈40 RVU. The final viscosity was ≈60 RVU. Waxy rice viscosity remained low (<20 RVU), then doubled upon cooling. The main difference in the digestion profiles was due to temperature. The flours extruded at 100°C digested significantly slower than those extruded at 125 and 150°C. Significant differences were not detected for a given temperature and moisture (P > 0.05) except for long grain and parboiled rice extruded at 100°C and 15% added moisture (F = 4.48, P = 0.03) and 150°C and 20% added moisture (F = 3.72, P = 0.05). Moisture appeared to have little effect for a given temperature, except when parboiled rice was extruded at 150°C. The digestion rate for 11 and 25% added moisture was significantly less than that for 20% (P ≤ 0.05).     

Effect of Corn Milling Practices on Aleurone Layer Cells and Their Unique Phytosterols

Coarse and fine fiber fractions obtained from the corn wet‐milling processes, with and without steeping chemicals (SO₂ and lactic acid), were evaluated microscopically for structure and analytically for recovery of phytosterol compounds from the fiber oil. Microscopic results showed that wet milling, with and without chemicals during steeping, changed the line of fracture between pericarp and endosperm and therefore affected the recovery of the aleurone layer in coarse (pericarp) and fine (endosperm cellular structure) fiber. Analytical results showed that most of the phytosterols and mainly phytostanols in corn fiber are contributed by the aleurone layer. Hand‐dissection studies were performed to separate the two layers that comprise the wet‐milled coarse fiber, the aleurone, and pericarp layer. Analyses revealed that the aleurone contained 8× more phytosterols than the pericarp.     

Effects of Inorganic Fertilizer Inputs on Grain Yields and Soil Properties in a Long‐Term Wheat–Corn Cropping System in South China

Abstract

A long‐term double cropping wheat (Triticum aestivum L.) and corn (Zea mays L.) experiment was conducted at Qiyang, Hunan, China, to study the effects of inorganic fertilizers on grain yields and soil properties and to identify the possible causes of yield trends. Six treatments of unfertilized control, N, NP, NK, PK, and NPK were included. The treatments (N, NP, NK, and NPK) where inorganic nitrogen (N) was added showed significant (P<0.05) yield declines of 76 to 114 kg ha^?1 yr^?1 for wheat and 94 to 260 kg ha^?1 yr^?1 for corn, respectively, except for corn yield in the NPK treatment in which the decline was not significant during a 15‐yr (1990–2005) period. Comparatively, the decline amounts in corn were much higher than in wheat. The yields of wheat and corn remained unchanged in the PK treatment. The total organic carbon (C), total N, phosphorus (P), and available P, potassium (K), copper (Cu), and zinc (Zn) contents of soil were either increased or decreased during the study period. Both the decreases of exchangeable calcium (Ca²⁺) and magnesium (Mg²⁺) and increases of exchangeable hydrogen (H⁺) and Al³⁺ contents of soil in the treatments where inorganic N was applied were significant (P<0.05). The same four treatments showed significant pH declines ranging from 0.07 to 0.12 yr^?1. Several lines of evidence point to decline of soil pH due to inorganic N fertilizer added as leading to the overall yield decline of wheat and corn. However, the yields of both crops increased significantly after lime application. In the long term, the farmers should be encouraged to use adequate lime based on a balanced approach to ensure sustainable productivity.     

Phenolic Compounds and Antioxidant Activity of Extruded Nixtamalized Corn Flour and Tortillas Enriched with Sorghum Bran

Sorghum bran (SB) is a good source of phenolic compounds with high antioxidant capacity that increases the antioxidant activity (AOX) of tortillas prepared with extruded nixtamalized corn flour. The objective of this research was to study the effects of bran addition (0, 5, or 10%) before (ENBESB) or after (ENAFSB) extrusion, in the features and composition of baked tortillas in terms of total phenolic compounds (TPC), AOX, color (L , a , b, hue, chroma, and E value), and tortilla firmness. It was possible to retain more than 81.8 and 89.9% of TPC and AOX, respectively, in ENBESB‐10% flour. Tortillas prepared with ENAFSB‐10% flour retained more than 92 and 76% of TPC and AOX, respectively, compared with ENBESB. However, tortillas elaborated with ENAFSB flour showed a higher firmness and lower flexibility than counterparts produced from ENBESB. The use of extrusion to produce nixtamalized corn flours and the strategy of adding the SB to the corn meal before extrusion were essential to retain TPC and AOX and, additionally, to enhance texture of tortillas.     

Frequency of defoliation and nitrogen and phosphorus fertilization on Andropogon gayanus Kunth. I. Yield,crude protein content,and in vitro digestibility

Abstract

An experiment was conducted in a semi‐arid region located in the State of Zulia, western part of Venezuela (10°32'N and 71°42'W, 600 mm average annual rainfall), to evaluate dry matter (DM) yield and in vitro organic matter digestibility (IVOMD), and crude protein (CP) content of Andropogon gayanus Kunth as affected by three frequencies of defoliation (every 42, 63, and 84 days) and fertilization with three levels of nitrogen (N) (0, 100, and 200 kg N ha^‐1‐year^‐1) and two levels of phosphorus (P) (0 and 75 kg P₂O₅ ha^‐1.year^‐1) in a factorial array using a split‐split‐plot experimental design with frequencies in the main plots, N in the sub‐plots, and P in the sub‐subplots with three replications. Soil was a sandy loam Aridisol with a pH of 5.5. Average soil calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), and P contents were 0.6, 0.3, 0.1 and 0.17 meq‐100g^‐1 soil, and 6 ppm, respectively. Data from six, four, and three cuttings for the frequencies of 42, 63, and 84 days were analyzed over the total duration of the study (252 days) as well as separately for periods with high (168 days, 384 mm) and low rainfall (84 days, 69 mm). Frequency of defoliation was the only factor that influenced (P≤0.05) the variables studied. In the overall analyses, the highest (P≤0.05) DM yield (3,656 kg#lbha^‐1.cutting^‐1) was obtained with harvests every 63 days. Mean IVOMD decreased (P≤0.05) from 54.2 to 51.7% with increasing harvest interval from 63 to 84 days, respectively. The average CP content was 7.9%. With low rainfall, mean DM yield was 2,209 kg#lbha^‐1, CP content declined (P≤0.05) from 7.5 to 3.9% as the cutting interval increased, and IVOMD decreased (P≤0.05) between 42 and 63 days. With high rainfall, the highest (P≤0.05) DM yield (4,872 kg#lbha^‐1) and IVOMD (56.5%) were found at 63 days of age. Mean CP content was 9.3%. These results confirm that A. gayanus is a highly productive forage grass. Lack of response to N and P fertilizers may be attributed partly to relatively low rainfall during the experiment, adaptation of the grass to low fertility soils, and long intervals between N applications and the next harvest.     

Research on the Threshold of Aluminum Toxicity and the Alleviation Effects of Exogenous Calcium,Phosphorus, and Nitrogen on the Growth of Chinese Fir Seedlings under Aluminum Stress

Chinese fir (Cunninghamia Lanceolata Lamb, Hook) is generally considered a superior timber in southern China and other areas in the world. In the past few decades, aluminum (Al) toxicity has become one of biggest stress factors in the production and growth of Chinese fir, although this species prefers an acidic environment. To date, the selection of indicator species for Al toxicity remains critical in the field, and Al toxicity has not been successfully treated by artificially controlling Chinese fir plantations. To assess the Al toxicity risk, the height of the dominant tree, the concentration of calcium (Ca²⁺)/Al³⁺ in soil solution, and the concentration of Ca²⁺?/?[Ca²⁺ + iron (Fe³⁺) + Al³⁺] in litter leached organic acids were introduced. The results indicated that eight plots had suffered Al toxicity. The threshold of Al toxicity was 37.53 mg kg^?1 in soil or 1.39 mmol L^?1 in soil solution, a pH of 4.15, a Ca²⁺?/?(Ca²⁺ + Fe³⁺ + Al³⁺) molar ratio of 0.487, and a Ca²⁺/Al³⁺ molar ratio of 1.599. The positive effects of exogenous nutrition (Ca, phosphorus [P], and nitrogen [N]) on the growth of Cunninghamia lanceolata seedlings was also studied in pot experiments based on results in the field. The cation nutrition can lead to detoxification, and the exogenous nutrition thresholds were Ca²⁺/?Al³⁺ ≥ 2.8, phosphorus (P)/?Al³⁺ ≥ 4.4, ammonium (NH₄ ^?)–nitrogen (N)?/?Al³⁺ ≥ 4.5. The data presented in this study are very helpful for the understanding of the degree of Al toxicity and have notable significance for the management of Chinese fir plantations.     

Effects of Steeping Temperatures and Periods of Waxy Rice on Expansion Properties of Gangjung (a traditional Korean oil‐puffed rice snack)

This study was conducted to investigate the effect of steeping conditions of waxy rice, temperatures (15, 25, and 35°C) and time periods (1, 11, and 21 days) on the expansion ratio of gangjung (a traditional Korean oil‐puffed rice snack). Physicochemical properties of waxy rice flour steeped under various conditions and expansion properties of gangjung made of the steeped waxy rice flour were investigated, and multiple regression analyses were applied between those properties to identify major physicochemical factors that optimally predict the expansion ratio of gangjung. As steeping temperature and time periods of waxy rice changed from the lowest to the highest, the expansion ratio of gangjung markedly increased (from 1,022 to 2,533%). Yet, the expansion ratio of the waxy rice sample steeped for 11–21 days at 35°C was not significantly different from the sample steeped for 21 days at 25°C, indicating that the lengthy steeping process for gangjung making can be shortened by increasing the steeping temperature. Physicochemical properties include moisture (γ = 0.85), protein (γ = –0.91), ash (γ = –0.84), potassium (γ = –0.89), magnesium (γ = –0.88), phosphorous (γ = –0.91), peak viscosity (γ = 0.77), and breakdown (γ = 0.94) of steeped waxy rice flour. These properties were highly correlated with expansion ratio (P < 0.01). Multiple regression analysis showed that the expansion ratio of gangjung was predicted successfully by the phosphorous content and breakdown value of steeped waxy rice flour.     

Effect of Foliar Application of Calcium on the Quality of Blueberry Fruits

Effect of foliar application of calcium (0.78 g, 4.68 g, and 7.8 g Ca^{2 +}) in pre-harvest, at three different growing conditions (tunnel, mesh, and ambient), on texture and pectin in blueberries (Vaccinium corymbosum) was studied. Calcium contents in leaves as well in fruits were different (P ≤ 0.05), affected by growing conditions and time. Differences (P ≤ 0.05) in calcium content were found in tunnel cultivar fruit, during the period to cell expansion toward harvest, at calcium foliar level of 5 mL per L (7.8 g). Fruit texture was significantly higher at the beginning of the cell expansion period in the tunnel cultivar fruit, and a linear correlation between calcium concentration and texture was established. Increment in low methoxyl pectin (LMP) was influenced by growing conditions, and was different (P ≤ 0.05) for tunnel cultivar fruit. A good correlation between LMP and calcium content was obtained with the high dose of calcium (5 mL per L).     

Frequency of defoliation and nitrogen and phosphorus fertilization on Andropogon gayanus Kunth. II. Macroelement concentrations

Abstract

An experiment was conducted in a semi‐arid region located in the State of Zulia, western part of Venezuela (10°32'N and 71°42'W, and 600 mm average annual rainfall), to evaluate ash and macroelement concentrations of Andropogon gayanus Kunth as affected by two frequencies of defoliation (every 42 and 63 days) and fertilization with three levels of nitrogen (N) (0, 100, and 200 kg N ha^‐1‐year^‐1) and two levels of phosphorus (P) (0 and 75 kg P₂O₅ ha^‐1#lbyear^‐1) in a factorial array using a split‐split‐plot experimental design with frequencies in the main plots, N in the sub‐plots, P in the sub‐sub‐plots, and two replications. Soil was a sandy‐loam Andisol with pH 5.5. Average soil calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), and P contents were 0.6, 0.3, 0.1, and 0.17 meq#lb100 g^‐1 soil and 6 ppm, respectively. Data from six and four cuttings for the frequencies of 42 and 63 days were analyzed over the total duration of the study (252 days) as well as separately for periods with “high”; (168 days, 384 mm) and “low”; rainfall (84 days, 69 mm). In the overall analysis, forage ash content was increased (P≤0.05) by increasing the cutting interval, whereas macroelement concentrations were not affected (P>0.05). Mean Ca, P, Mg, and Na were: 0.20, 0.11, 0.10, and 0.029 with over 90% of the samples inadequate for grazing ruminants. Only mean K content (1.2%) was considered adequate. Nitrogen fertilization did not influence (P>0.05) macromineral composition. Applied P fertilizer increased (P<0.05) forage P concentration from 0.09 to 0.12% and reduced (P≤0.05) the Ca:P ratio, but within the normal range. Most macroelement concentrations in A. gayamts are extremely low, indicating the need for mineral supplementation to prevent deficiencies in ruminants consuming this species.     

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.     

Comparison of Wet-Digestion and Dry-Ashing Methods for Total Elemental Analysis of Biochar

Total elemental analyses of biochars presents challenges during digestion because of biochars' high chemical recalcitrance and widely varied composition. Three biochars were chosen with contrasting properties: corn stover pyrolyzed at 300 °C, oak wood at 600 °C, and poultry manure with sawdust at 600 °C. Recovery of phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), and zinc (Zn) from poultry manure biochar was 10 to 100 times less with published wet- or dry-digestion methods than when using improved methods. The published dry-digestion method returned significantly (P < 0.05) more sodium (Na), suggesting contamination from borosilicate glassware. A modified dry-ashing (MDA) method was the most precise method, demonstrating a relative standard deviation within 3.7% of the most precise method for recovery of P, K, S, Ca, Mg, and Zn from both corn and oak biochars. The MDA method is comparatively safe and effective for preparing biochar for elemental analysis.     

Effect of calcium nitrate foliar spray on the calcium content,growth and freezing tolerance of Forsythia × Intermedia cultivars

Abstract

In many northern regions frost hardiness of new cultivars of woody plants and perennials is fundamental for nursery production and the greenery industry. This study was conducted to determine the effect of calcium fertilization on frost resistance of Forsythia sp. cultivars. Plants were sprayed five times at four week intervals with calcium nitrate 1?g of (Ca(NO₃)₂). 100?ml H₂O^?1 per shrub. Shoots were frozen at three temperatures: –20, –25, and –30?°C. In all cases the chlorophyll content index in the leaves, and the calcium (Ca²⁺) content in leaves and stems of forsythia cultivars were significantly higher when calcium nitrate supplementation was provided. The Ca²⁺content in the roots was not affected. The freezing temperature had a great effect on the stem frost damage of tested forsythia cultivars. The greatest damage was observed after freezing at –30?°C. However, tissue damage of plants that were sprayed with calcium nitrate was considerably less evident, and cross sections of stems looked significantly better. At the lowest temperatures (–25 and –30?°C) a positive effect of calcium fertilization on lower electrolyte leakage was observed in all tested cultivars. Fertilization with finely ground calcium nitrate increased stem freezing tolerance of forsythia tested cultivars, especially new ones which have stems that are more susceptible to frost damage.