共查询到20条相似文献,搜索用时 31 毫秒
1.
Weston B. Johnson Wajira S. Ratnayake David S. Jackson Kyung‐Min Lee Timothy J. Herrman Scott R. Bean Stephen C. Mason 《Cereal Chemistry》2010,87(6):524-531
Dent corn (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) sample sets representative of commonly grown hybrids and diverse physical attributes were analyzed for alkaline cooking performance. The influence of kernel characteristics including hardness, density, starch properties (thermal, pasting, and crystallinity), starch content, protein content, and prolamin content on alkaline cooking performance was also determined. Corn nixtamal moisture content was lower for hard, dense kernels with high protein contents; sorghum nixtamal moisture content was lower for kernels with low moisture contents and low starch relative crystallinities. Statistically significant (P < 0.05) regression equations showed that corn nixtamal moisture content was influenced by TADD (tangential abrasive dehulling device) index, kernel moisture content, starch content, and protein content; sorghum nixtamal moisture content was influenced by starch relative crystallinity, kernel moisture content, and abrasive hardness index. Pericarp removal was not strongly correlated with kernel characterization tests. Location (environmental) and hybrid (genetic) factors influenced most kernel characteristics and nixtamalization processing variables. 相似文献
2.
Sorghum undergoes structural changes during tempering, steam cooking, and flaking at various tempering moisture levels. Physical properties of flakes, digestibility, birefringence, scanning electron microscopy (SEM), and environmental SEM (ESEM) were used to evaluate the quality of steam-flaked sorghum from grain containing 11–23% water. As moisture levels increased, the flakes became stronger (57–69% whole flakes) and less dusty (9–4% fines). The diameter of the flakes varied among moisture levels, but preflake and final flake moisture contents increased as the temper level increased. Starch birefringence remained unchanged after tempering, and decreased only slightly after steam cooking; gelatinization occurred primarily during the flaking process. The steaming process prepared the grain for flaking by heating and softening the kernels. Tempering allowed extra water to penetrate inside the kernel endosperm. More starch granules had the opportunity to reach the glass transition temperature (T g) during flaking. Based on subjective evaluation, birefringence, and SEM, poor quality flakes were opaque, chalky in appearance, and prone to high levels of breakage. The starch granules were more intact and less tightly packed into the flake. Good quality flakes were translucent, thin, and strong, with little chalkiness, and low levels of dust and fines. The dehydrated gelatinized starch continuous phase surrounding the granules reduced the amount of air spaces within the flake, increasing the translucency. ESEM inspection revealed that starch was more extensively gelatinized in the tempered samples. The starch granules were much larger in diameter, and the relative level of gelatinization, evident by the presence of starch granules with collapsed centers, was much higher. 相似文献
3.
Frederiksen AM Festersen RM Andersen ML 《Journal of agricultural and food chemistry》2008,56(18):8514-8520
An electron spin resonance (ESR)-based method was used for evaluating the levels of radical formation during mashing and in sweet wort. The method included the addition of 5% (v/v) ethanol together with the spin trap alpha-4-pyridyl(1-oxide)- N- tert-butylnitrone (POBN) to wort, followed by monitoring the rate of formation of POBN spin adducts during aerobic heating of the wort. The presence of ethanol makes the spin trapping method more selective and sensitive for the detection of highly reactive radicals such as hydroxyl and alkoxyl radicals. Samples of wort that were collected during the early stages of the mashing process gave higher rates of spin adduct formation than wort samples collected during the later stages. The lower oxidative stability of the early wort samples was confirmed by measuring the rate of oxygen consumption during heating of the wort. The addition of Fe(II) to the wort samples increased the rate of spin adduct formation, whereas the addition of Fe(II) during the mashing had no effect on the oxidative stability of the wort samples. Analysis of the iron content in the sweet wort samples demonstrated that iron added during the mashing had no effect on the iron level in the wort. The moderate temperatures during the early steps of mashing allow the endogenous malt enzymes to be active. The potential antioxidative effects of different redox-active enzymes during mashing were tested by measuring the rate of spin adduct formation in samples of wort. Surprisingly, a high catalase dosage caused a significant, 20% reduction of the initial rate of radical formation, whereas superoxide dismutase had no effect on the oxidation rates. This suggests that hydrogen peroxide and superoxide are not the only intermediates that play a role in the oxidative reactions occurring during aerobic oxidation of sweet wort. 相似文献
4.
《Cereal Chemistry》2017,94(4):705-711
Infrared (IR) heating of corn followed by tempering treatments has potential to decontaminate corn of microbes without adverse effects on the overall corn quality. However, it is vital to determine the optimal processing parameters that maximize throughput and microbial load reduction and minimize drying energy without affecting overall corn quality. This study investigated effects of IR heating and tempering treatments on mold load reduction, corn color change, and drying energy requirements. Freshly harvested corn samples with initial moisture contents (IMCs) of 20, 24, and 28% wet basis were dried with a laboratory‐scale IR batch dryer in one and two drying passes. The dried samples were then tempered for 2, 4, and 6 h at 50, 70, and 90°C. Results showed that mold load reduction ranged from 1 to 3.8 log colony forming units per gram of corn (log CFU/g) for one‐pass treatments and from 0.8 to 4.4 log CFU/g for two‐pass treatments as tempering temperature and tempering duration increased. Compared with the control, treatments resulted in reduction of the corn color parameter (ΔE ) (P < 0.05). Energy expended to dry the corn varied between 1.7 and 2.5 MJ/kg for one‐pass treatments and between 4.1 and 6.1 MJ/kg for two‐pass treatments. This work showed that IR heating of corn has the potential to significantly decontaminate microbes on corn. The IR process may help producers combat mycotoxin issues in corn that result from mold contamination. 相似文献
5.
High‐intensity ultrasound (sonication) was investigated as a method to rapidly purify starch from sorghum and other cereal grains. To improve the process, buffers were optimized to solubilize sorghum proteins in combination with the sonication. Protein content and starch color were determined to evaluate the efficiency of the extraction process. Sonication times, SDS concentration, different types and concentrations of reducing agents (sodium metabisulfite, dithiothreitol, and β‐mercaptoethanol), and centrifugation speeds of the starch washing procedure were tested. Protein content of isolated sorghum starch was reduced to 0–0.14% (db) after 2 min of sonication (using any of the reducing agents tested). Sodium metabisulfite was chosen as the preferred reducing agent because of its lower toxicity and odor compared with other reducing agents tested. The optimum conditions for producing high‐purity sorghum starches (0.06% protein) were obtained using the following conditions: 2 min of sonication time with 12.5 mM sodium borate buffer, pH 10, containing 0.5% SDS (w/v) and 0.5% sodium metabisulfite (w/v) using 1,500 rpm centrifugation speed during starch washing. Starches separated by this method showed significantly less protein content and b values (yellowness) compared with starches separated by enzymatic methods or methods using NaCl solutions and protein extraction buffers with multiple washing steps, both of which take several hours to complete. Differential scanning calorimetry thermogram values for starches isolated by three different methods showed similar patterns, except that starches obtained with the enzymatic method had slightly higher values of To, Tp, and ΔH. Other cereal starches from whole wheat meal, wheat flour, corn, rice, and barley were also obtained rapidly using sonication. 相似文献
6.
A high‐tannin sorghum cultivar with 3.96% tannin content was used to study the effects of germination on its ethanol fermentation performance in a laboratory dry‐grind process. High‐tannin sorghum sample was germinated for 3 and 4 days. Original and germinated samples were analyzed for tannin, starch, protein, free amino nitrogen (FAN), and glucose content. Endosperm structures and flour pasting properties of germinated and nongerminated sorghum samples were examined using a scanning electron microscope (SEM) and rapid visco analyzer (RVA). Germination reduced tannin content from 3.96% to negligible levels. The free fermentable sugars (glucose, maltose, and maltotriose) in the germinated samples were significantly higher than those in the nongerminated control. Judged by the starch (starch plus dextrin) and free amino nitrogen contents in the mashed samples, germination improved degree of hydrolysis for starch by 13–20% and for protein by 5‐ to 10‐fold during mashing. Germination significantly shortened the required fermentation time for ethanol production by 24–36 hr, increased ethanol fermentation efficiency by 2.6–4.0%, and reduced the residual starch content in the distillers dried grain with solubles (DDGS) compared to the nongerminated control. Ethanol yield for the 3‐day germinated samples was 2.75 gallons/bushel, which was 3.1% higher than the 2.67 gallons for the nongerminated control. Ethanol yield for the 4‐day germinated sorghum was 2.63 gallons/bushel due to excessive loss of starch during germination. 相似文献
7.
Zhao R Bean SR Ioerger BP Wang D Boyle DL 《Journal of agricultural and food chemistry》2008,56(3):946-953
Nine grain sorghum cultivars with a broad range of ethanol fermentation efficiencies were selected to characterize the changes in sorghum protein in digestibility, solubility, and microstructure during mashing and to relate those changes to ethanol fermentation quality of sorghum. Mashing reduced in vitro protein digestibility considerably, and a large amount of polymers cross-linked by disulfide bonds were developed during mashing. As a marker of cross-linking, protein digestibility of the original samples was highly related to conversion efficiency. gamma-Kafirin (%) neither correlated to ethanol yield nor conversion efficiency significantly. Solubility of proteins in an alkaline borate buffer in conjunction with SDS decreased substantially after mashing. Solubility and the SE-HPLC area of proteins extracted from mashed samples were highly correlated with ethanol fermentation. Ethanol yield increased and conversion efficiency improved notably with the increase of extracted proteins from mashed samples. SE-HPLC total area could be used as an indicator to predict ethanol fermentation. CFLSM images proved that sorghum proteins tended to form highly extended, strong web-like microstructures during mashing. The degree of protein cross-linking differed among samples, and more open microstructures were observed in samples with higher conversion efficiencies. The web-like protein matrix was found to hold not only starch granules but also some oligosaccharides or polysaccharides inside. The formation of web-like microstructures because of cross-linking reduced conversion efficiency. 相似文献
8.
The Rapid Visco‐Analyzer (RVA) was used to characterize the pasting properties of 68 sorghum grains with a standard 23‐min temperature profile. The results showed a strong linear relationship between ethanol yield and final viscosity as well as setback. Ethanol yield increased as final viscosity decreased. A modified RVA procedure (10 min) with an application of α‐amylase was developed to simulate the liquefaction step in dry‐grind ethanol production. There was a remarkable difference in mashing properties among the sorghum samples with the normal dosage of α‐amylase. The sorghum samples which were difficult to liquefy in the mashing step had much higher peak viscosities than the samples that were easily liquefied. The results also showed that the relationship between conversion efficiency and mashing property was significant. Tannins cause high mash viscosities. There was a strong linear relationship between tannin content and final viscosity as well as peak viscosity. The modified RVA procedure is applicable not only for characterization of mashing properties but also for optimization of α‐amylase doses for starch liquefaction. 相似文献
9.
The effect of lactic acid on starch yields of different corn hybrids was determined by wet-milling 18 commercial corn hybrids at three levels of lactic acid. All 18 hybrid samples tested had higher starch yields when lactic acid was added to the steep solution, although the magnitude of the increased starch yields varied between 2.9 and 12.0%. The optimal lactic acid concentration for maximum starch recovery was found to be between 0.55 and 1.67% lactic acid, by wet-milling nine of the same 18 corn hybrids with seven levels of added lactic acid. Between 0.83 and 1.67% lactic acid, the starch yields of eight of the nine hybrids were constant (within ±0.5%). Results showed that the average starch yield across all hybrids decreased with a lactic acid concentration <0.55% and a lactic acid concentration >1.67%. 相似文献
10.
S. R. Bean O. K. Chung M. R. Tuinstra J. F. Pedersen J. Erpelding 《Cereal Chemistry》2006,83(1):108-113
The single kernel characterization system (SKCS) has been widely used in the wheat industry, and SKCS parameters have been linked to end‐use quality in wheat. The SKCS has promise as a tool for evaluating sorghum grain quality. However, the SKCS was designed to analyze wheat, which has a different kernel structure from sorghum. To gain a better understanding of the meaning of SKCS predictions for grain sorghum, individual sorghum grains were measured for length, width, thickness (diameter), and weight by laboratory methods and by the SKCS. SKCS predictions for kernel weight and thickness were highly correlated to laboratory measurements. However, SKCS predictions for kernel thickness were underestimated by ≈20%. The SKCS moisture prediction for sorghum was evaluated by tempering seven samples with varying hardness values to four moisture levels. The moisture contents predicted by SKCS were compared with a standard oven method and, while correlated, SKCS moisture predictions were less than moisture measured by air oven, especially at low moisture content. Finally, SKCS hardness values were compared with hardness measured by abrasive decortication. A moderate (r = 0.67, P < 0.001) correlation was observed between the hardness measurements. The SKCS predictions of kernel weight and diameter were highly correlated with laboratory measurement. Moisture prediction, however, was substantially lower by the SKCS than as measured by an air oven method. The SKCS should be suitable for measuring sorghum grain attributes. Further research is needed to determine how SKCS hardness predictions are correlated to milling properties of sorghum grain. 相似文献
11.
Red and white sorghum were tempered using two methods (direct and indirect) to adjust moisture content (MC) to 12, 14, and 17% and popped using a hot‐air popper. Kernel size, pericarp thickness, bulk density, popped kernel expansion volume and ratio, popped volume, and surface color were recorded. Forty‐six untrained panelists evaluated popped sorghum using a 9‐point hedonic scale and expressed preference using a paired comparison test. Sorghum with thicker pericarp (red) had higher percent popped, expansion ratio, and popped volume. In white sorghum, indirect tempering increased percent popped and tempering to 17% MC increased popped volume. Panelists significantly preferred popcorn in appearance (8.0 ± 1.0) and size (7.9 ± 1.0) to sorghum (6.6 ± 1.7 appearance and 5.6 ± 2.2 size for 12 and 17% MC tempering). Panelists equally preferred the taste of popcorn (7.1 ± 1.5) and popped sorghum tempered to 12% MC (6.4 ± 1.8) and 17% MC (6.9 ± 1.4). Sorghum pops were brighter, vividly whiter, and 5× smaller than popcorn. 相似文献
12.
Initial uniform distribution of moisture in the corn kernel is transformed into nonuniform distribution through tempering to facilitate easy fractionation of corn components. Proper temper duration is essential for effectiveness of the tempering process: a short temper time is insufficient to cause necessary nonuniformity; a long temper duration may allow moisture to redistribute uniformly. Untempered corn suffers from lack of beneficial swelling stress and therefore produces lower yields of flaking grits, coarse grits, and germ. For tempered corn, the system throughput exponentially decreases with temper duration and then stabilizes; the period of stabilization is dependent on weight distance. Throughput values are lower at longer weight distances. At a temper duration of 0.066 m, throughput was ≈33–50% at 0.053 m weight distance. Tail stock fraction rapidly and nonlinearly decreases with increase in temper duration; the rate of decrease is higher at longer weight distance. The peak values of flaking grits can exceed 50% at some combinations of weight distance and temper duration. Coarse grit yields were 9–19% and 16–24% for the shorter and longer weight distances, respectively. Germ recovery improved due to tempering, and differed only by ≈0.5% at the two weight distances. Tempering lowered the oil content of flaking grit, but the temper duration did not have much influence on moisture content of various fractions. 相似文献
13.
R. S. Bhatty 《Cereal Chemistry》1997,74(6):693-699
Five registered cultivars of hull-less barley (HB) with regular or waxy starch were milled in a Quadrumat Jr. mill to obtain whole grain flour; pearled in a Satake mill (cultivar Condor only), and the pearled fractions examined by microscopy to determine true HB bran. The samples were milled after tempering and drying in a Buhler mill to obtain bran and flour yields. Flour color and composition of HB were unaltered on milling in the Quadrumat Jr. mill. Microscopic evidence showed that a 70% pearl yield was devoid of the grain's outer coverings, including the aleurone and subaleurone layers. Therefore, the balance of 30% constitutes true bran in HB. Dry milling (as-is grain moisture) of regular starch HB in the Buhler mill gave 59% total flour and 41% bran (bran + shorts) yields, the comparative values for the waxy starch HB were 42 and 58%. On tempering HB from 9 to 16% grain moisture, the total flour yield decreased in both types of HB but to a lesser extent in the waxy starch HB due to decreases in reduction flour. On drying HB to 5 or 7% moisture, total flour yields increased due to contamination with bran and shorts. The milling study led to the conclusion that HB, at best, be dry-milled and a bran finisher be used to obtain commercial flour extraction rates. Lower total flour yields in the waxy starch HB than in the regular starch HB milled at the same grain moisture levels seemed due to higher β-glucan rather than grain hardness. Waxy starch HB flour had higher mixograph water absorption and water-holding capacity than regular starch HB or soft white wheat flour milled under identical conditions. Roller-milled HB products offer the best potential for entry into the food market. 相似文献
14.
Four pearl millet genotypes were tested for their potential as raw material for fuel ethanol production in this study. Ethanol fermentation was performed both in flasks on a rotary shaker and in a 5‐L bioreactor using Saccharomyces cerevisiae (ATCC 24860). For rotary‐shaker fermentation, the final ethanol yields were 8.7–16.8% (v/v) at dry mass concentrations of 20–35%, and the ethanol fermentation efficiencies were 90.0–95.6%. Ethanol fermentation efficiency at 30% dry mass on a 5‐L bioreactor reached 94.2%, which was greater than that from fermentation in the rotary shaker (92.9%). Results showed that the fermentation efficiencies of pearl millets, on a starch basis, were comparable to those of corn and grain sorghum. Because pearl millets have greater protein and lipid contents, distillers dried grains with solubles (DDGS) from pearl millets also had greater protein content and energy levels than did DDGS from corn and grain sorghum. Therefore, pearl millets could be a potential feedstock for fuel ethanol production in areas too dry to grow corn and grain sorghum. 相似文献
15.
Ai Y Medic J Jiang H Wang D Jane JL 《Journal of agricultural and food chemistry》2011,59(13):7385-7392
This study aimed to characterize and compare the chemical structures, physical properties, and enzymatic hydrolysis rates of five sorghum starches (6B73, 6C21, 6C69, 7R34, and X789) with that of corn starch (B73). Sorghum kernels consisted of 68.7-70.6% starch, more than the B73 corn (67.4%). Sorghum starches displayed higher gelatinization temperatures (66.6-67.4 °C), greater gelatinization enthalpy changes (13.0-14.0 J/g), and greater percentages of retrogradation (60.7-69.1%), but slower enzymatic hydrolysis rates (83.8-87.8% at 48 h) than the B73 corn starch (61.7 °C, 10.1 J/g, 51.5%, and 88.5%, respectively). These differences could result from the sorghum amylopectins consisting of fewer short branch chains (DP 6-12) (12.8-14.0%) than the corn amylopectin (15.0%). The sorghum starches showed greater peak and breakdown viscosities but lower setback viscosities than the B73 corn starch, resulting from the lower amylose content of the sorghum starches. After 96 h of fermentation, most ground sorghums exhibited lower ethanol yields (30.5-31.8%) than the ground B73 corn (31.8%). 相似文献
16.
The effects of addition of hexamethylenetetramine (HMT) or sulfite during mashing on the polyphenol content and oxidative stability of wort and beer have been evaluated in a series of laboratory mashings and pilot brews. HMT reduced the concentration of catechin, prodelphinidin B-3, and procyanidin B-3 in wort and beer, whereas the concentration of ferulic acid was unaffected. Sulfite had only a minor effect on the concentration of phenolics in wort and beer. Addition of HMT or sulfite during mashing increased the oxidative stability of the beer slightly as judged by the tendency of formation of radicals (ESR spin trapping technique), although sensory analysis gave identical flavor acceptance scores to beers produced from untreated and HMT-treated wort and lower scores to beer from sulfite-treated wort. No difference in the oxidative stability of the differently treated sweet worts could be detected as judged by the rate of formation of radicals. HMT addition during mashing has thus been demonstrated to be a valuable experimental tool to control the level of polyphenols in wort and for producing brews with various levels of polyphenols from a single malt. 相似文献
17.
Evidence is presented that corn (maize) and sorghum starch granules have channels that connect a central cavity to the external environment. A mutant sorghum starch with numerous, large surface pores was treated with a methanolic solution of merbromin and sectioned. Light, fluorescence, and compositional backscattering electron microscopy revealed channels connecting an internal cavity to the external surface in most granules. Cavities and channels could also be seen in whole corn and sorghum starch granules treated with merbromin in methanol and viewed by fluorescence microscopy. Treatment of sorghum starch granules with an aqueous solution of merbromin revealed that the molecule penetrated the granule matrix under even slightly swelling conditions. Light microscopy showed cavities in unstained, whole, dry corn and sorghum starch granules mounted in immersion oil. 相似文献
18.
Three sorghum hybrids were tempered and decorticated with an abrasive‐type mill (scarifier) to produce low‐ash and low‐fat grits. The effects of tempering time and temperature were investigated, and the optimum tempering conditions for obtaining low‐ash and low‐fat grits were found for each sorghum hybrid. The conditions were 3 min at 30°C for bronze sorghum with heteroyellow endosperm, 40 min at 40°C for white sorghum with white endosperm, and 10 min at 20°C for red sorghum with white endosperm. The grits yields were low using the scarifier, hence, another abrasive‐type mill was investigated for improving grits yields. A modified experimental corn decorticator‐degerminator was used to dry‐mill the three sorghum hybrids tempered to the optimum conditions found with the scarifier. The yields were 45.3% grits with 0.23% ash and 0.18% fat for the bronze/heteroyellow hybrid, 49.1% grits with 0.22% ash and 0.36% fat for white/white hybrid, and 44.2% grits with 0.20% ash and 0.22% fat for red/white hybrid. This study showed that grits yields were higher and ash and fat contents were lower when sorghum was processed with the decorticator‐degerminator than with the scarifier under the same optimum conditioning. 相似文献
19.
调质大米半干法磨粉制备鲜米粉及其品质测定 总被引:4,自引:1,他引:3
为考察半干法磨粉对鲜米粉品质的影响,该研究选用旋风磨和布勒磨对调质后含水率为28%和30%的大米进行磨粉,分析大米粉的白度、凝胶特性及糊化特性,对加工鲜米粉的质构特性、蒸煮特性和感官品质进行了分析。结果显示:调质大米可以减小磨粉仪器机械力和热能对大米粉品质的破坏,其中调质大米经布勒磨粉碎后的白度显著高于湿磨粉白度(P0.05);旋风磨含水率为30%调质粉的凝胶硬度最大为3.45 N/cm2,与湿磨粉的无显著差异(P0.05);2种调质粉相比于湿磨粉其崩解值较小,其中布勒磨含水率为30%调质粉回生程度较低,与湿磨粉无显著差异(P0.05)。对于鲜米粉的品质,筛选得到的旋风磨含水率为30%鲜米粉的硬度为35.10 N/cm2,弹性为0.97,较湿磨米粉更柔软弹滑,感官评价总分和蒸煮特性与湿磨米粉无显著差异。以上结果表明,含水率为30%的大米经旋风磨粉碎后能够制得与湿法磨浆相媲美的鲜米粉,可为解决湿磨法废水量大、产品得率低等问题提供参考。 相似文献
20.
Tempering conditions of wheat grain change the quality of the flour, yet most experimental milling systems use a standard tempering without optimization. The effect of tempering condition on milling performance and flour functionality for soft red winter (SRW) wheat grain was tested by measuring flour yield, ash, polyphenol oxidase (PPO), and solvent retention capacity (SRC) in grain samples from three SRW cultivars (Roane, Cyrus, and Severn). Tempering was conducted with a full factorial design of initial wheat moisture, tempered wheat moisture, tempering temperature, and tempering time at two levels. Tempered wheat moisture had the largest effect on milling performance and flour functionality. Flour yield was more reduced for all samples tempered at 15% moisture than for samples tempered to 12% moisture. Flour quality of the 15% tempered sample was better than the 12% tempered samples due to less bran contamination as measured by flour ash and PPO. Increasing the tempering moisture increased flour sucrose SRC and lactic acid SRC but reduced sodium carbonate SRC for samples. Changing tempered wheat moisture changed flour yield and quality much more than did changing the length of time for tempering, the temperature at wheat is tempered, or differences in the initial moisture of the wheat before tempering. The last three effects could be used to improve flour yield in both the 12 and 15% tempered wheat treatment but the detrimental effects of these treatments on flour quality were minimal when combined with the 15% tempered wheat moisture treatment. 相似文献