Fatty acid accumulation in the different fractions of the developing corn kernel

In the food industry, the use of the oil is determined by the composition of fatty acids, and this is highly dependent on its natural origin. The fatty acid composition of whole corn kernel was determined in three varieties of corn (Astro, GH2547, and Local). Linoleic acid was the predominant fatty acid in the oil of Astro and Local at all collection dates, whereas it was the major fatty acid in the oil of GH2547 only between 40 and 60 days after pollination (DAP). The fatty acid accumulation in the endosperm, pericarp and germ fractions of the corn kernel during maturation was determined. The accumulation pattern of oil content was different in these three kernel fractions. The highest levels of oil content in the endosperm (2.2%), germ (34.3%) and pericarp (10.8%) fractions were detected at 20, 40 and 30 (DAP), respectively. The fatty acid accumulation patterns were different amongst the analysed kernel parts, indicating a numerous differences between the three corn kernel parts. Throughout the sampling periods, the endosperm fraction was distinguished by the highest and the lowest levels of oleic and linoleic acids, respectively. At all stages of kernel development, the pericarp fraction had the highest levels of total polyunsaturated fatty acids, which has numerous healthy applications. These results may be useful in the understanding of the potential source of the beneficial unsaturated fatty acids amongst the different fractions of the corn kernel during maturation.     

Phytostanols and phytosterols distributions in corn kernel

Recently, industry has focused attention on plant matrices rich in phytosterols and phytostanols for their ability to reduce serum cholesterol levels. Therefore, the objective of this study was to examine the phytosterols and phytostanols contents of different fractions (endosperm, pericarp, germ) of corn kernel. The germ fraction contained more oil (24.2–30.7%) than endosperm and pericarp fractions (0.4–1.2%). Endosperm oil had the highest levels of phytostanols and 4,4-dimethylsterols, while pericarp oil had the greatest amounts of 4-desmethylsterols and 4-monomethylsterols. In the oil extracted from three corn kernel fractions sitostanol was the predominant phytostanols (77–87%), followed by campestanol (13–23%). The high percentages of 24–methylencycloartanol and cycloartenol were detected in the endosperm and pericarp parts, respectively. Citrostadienol was detected in corn germ oil as the main component of the 4-monomethylsterols fraction. In different parts of corn kernel, β-sitosterol (62–69%) was the major 4-desmethylsterol, followed by campesterol (11–18%) and stigmasterol (5–13%).     

Bioactive amines in fresh, canned and dried sweet corn, embryo and endosperm and germinated corn

The types and levels of free bioactive amines in different corn products were determined. The amines were analyzed by ion pair-HPLC, post-column derivatization with o-phthalaldehyde and fluorimetric detection. Fresh sweet corn contained mainly spermidine followed by putrescine. Spermine, cadaverine, phenylethylamine, histamine and agmatine were also present at low levels. The profile and levels of amines changed significantly in canned and dried corn. Putrescine was the prevalent amine in canned corn whereas spermine was prevalent in dried corn. Germinated corn had significantly higher spermidine, spermine and putrescine levels. The embryo of the corn contained significantly higher spermine levels compared to the endosperm. These results indicate that corn is a good source of polyamines and that the different types of corn products available can be used to provide a profile of amines according to specific dietary need.     

Mechanism of calcium uptake in corn kernels during the traditional nixtamalization process: Diffusion,accumulation and percolation

In the present work the results of the mechanism of calcium uptake in nixtamalized corn kernel were studied. The results showed that at a critical time, the calcium uptake in the pericarp suffers a drastic change; this fact cannot be associated only to the diffusive mechanism. The SEM analysis of processed corn kernels, taken at 1 h of steeping time illustrates a calcium cluster formation. It means that for short steeping times the calcium uptake in the total kernel is governed by an accumulation process in the most external layers of the pericarp and the diffusion process is not relevant. The apparition of micro-holes for critical time in dependence on the temperature indicates that another mechanism is contributing to the calcium uptake. These holes can pass thought the whole pericarp or form an interconnected lattice to develop a percolation path. The holes formations allow the entrance of water and calcium directly to the outermost layers of the endosperm and now the accumulation of calcium is not the predominant mechanism. It could be implied that, at this critical time the percolation of water and calcium thought these holes is the main mechanism to calcium uptake in the corn kernel and the diffusion process is not relevant.     

广东地区浅圆仓玉米粮堆温度分布规律研究

为了解浅圆仓玉米储藏全年的粮堆温度变化规律,采用实仓调查的方法分析了广东地区一浅圆仓玉米入仓后第一年粮温在垂直方向和水平剖面上的变化,并通过温差和露点评估了粮堆表层的结露风险。结果表明：在垂直方向上,粮面下5 m范围内粮食受夏秋季太阳热辐射影响,温度超过20℃的时间在2个月以上,空调控温工艺能将仓温和表层粮温有效降低至25℃及以下,但在秋季空调关闭后,粮面下9 m范围的粮温有不同程度反弹升高;在水平剖面上,内外圈温差明显,温差大小受粮层深度和季节影响,同时受仓体周围遮挡物影响,阳光直射多的方向粮温高于其他方向;粮堆表层内圈范围在空调控温前结露风险较高。     

Effect of two different lipid sources on glass transition temperatures and tensile properties of corn semolina

The effect of adding corn oil (CO) and corn germ (CG) on the thermal and mechanical properties of corn semolina (CS) was investigated. The lipids concentration employed were 2% and 3% of CO or CG. The thermal transitions were studied in a moisture content range of 3–27% (d.b.), by means of dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) techniques. Wide angle X-ray scattering (WAXS) experiments showed that type-V amylose–lipid complexes were formed with the native lipids within the corn semolina during thermo-moulding and that re-crystallization to a type-A structure, favored by the added lipids, occurred upon storage in high relative humidity (RH) environments. Two thermal events were observed during the first DSC scan and tan δ DMTA curves. The first one appearing at around 55–60 °C was attributed to a possible phase separation or ageing phenomenon taking place during storage of the samples, while the second was ascribed to the glass transition temperature of CS. It was found that addition of both, CO and CG, reduced the moisture content required for these transitions to appear. The expected decrease in the glass transition temperatures with moisture content was well described by the Gordon–Taylor equation. The addition of CO and CG also causes plasticization of CS. Hence, corn germ meal can be used as a lipid source that is more convenient to handle than liquid fats. However, the CS T_g values were independent of the lipids content. Tensile properties of CS and CS-lipid systems were found to be influenced by the moisture content, the physical state of the samples, and their composition.     

Pre-harvest accumulation of deoxynivalenol in sweet corn ears inoculated with Fusarium graminearum

Three types of commercial sweet corn hybrids [sugary (su1), shrunken or 'supersweet' (sh2) and sugary enhancer (se1)] were silk channel inoculated in 1996 and 1997 with a macroconidial suspension of Fusarium graminearum to determine how early the mycotoxin deoxynivalenol accumulates in kernels. Disease symptoms rapidly developed on all hybrids and were apparent 4 days after inoculation. Symptoms stabilized by 28 days after inoculation. Toxin levels were greater than 1 μg/g in kernels as early as 2 weeks after silk emergence and rapidly increased to extremely high levels. Susceptibility in all hybrids decreased as the silk dried out. Deoxynivalenol concentrations were correlated to disease severity. There was some indication that the sh2 genotype was more susceptible than the su1 or se1 genotypes. These results suggest that improvement needs to be made in sweet corn with respect to resistance to gibberella ear rot.     

Occurrence and distribution of Fusarium graminearum and deoxynivalenol in sweet corn ears

Unusual wet and cool weather conditions during the 1994 growing season in Maryland and Delaware resulted in a severe outbreak of Fusarium graminearum on sweet corn ears ('Moore' variety) prior to harvesting and canning. The number of ears visibly infected with Fusarium spp. ranged from less than 5% to 25% in some fields. Infection typically occurred at the tassel end of the ears. Fusarium graminearum was isolated from surface disinfected kernels, both those which were visibly infected and those kernels which appeared disease-free in an area up to 5cm from the edge of the visibly moulded areas. Infected ears were cut into four sections and the kernels only were analysed for deoxynivalenol (DON) using liquid chromatography (LC)and mass spectrometry/gas chromatography (GC/MS). Kernels from the visibly mouldy area of the ears contained DON at levels of approximately 446mg/g DON on average; whereas in the nonvisibly infected portion of the ears adjacent to the mouldy tips, DON levels averaged approximately 10mg/g. Sections of ears closest to the base contained no detectable DON or less than 1 μg/g. This is the first reported natural occurrence of the mycotoxin DON in sweet corn prior to harvest and canning.     

玉米株型对套作大豆氮素积累、转运和籽粒蛋白质产量的影响

以＂玉/豆＂套作模式为背景,三个不同株型的玉米和三个不同熟期的大豆材料,采用两因素裂区设计,研究了大豆地上部氮素积累和转运,以及籽粒蛋白质含量的差异。结果表明,各大豆品种中,以晚熟大豆在不同时期、不同器官的氮素积累量为最高,分别高出中、早熟品种121.09%和165.33%,其氮素积累速率、有效荚数、籽粒产量和蛋白质含量平均分别为3.78kg/hm2.d、60.27荚、3 840.22kg/hm2和48.71%,均显著高于中、早熟品种;大豆地上部氮素积累总量、积累速率、转运量和单株有效荚数均随着玉米株型的变化（从紧凑型到平展型）而减少,紧凑型玉米下的大豆籽粒产量和蛋白质产量分别为2 609.10kg/hm2和1 203.83kg/hm2,显著高于其他玉米株型处理;交互作用分析表明,玉米株型与大豆熟性在单株荚数、单荚粒数、籽粒产量和蛋白质产量上互作显著;相关性分析表明蛋白质产量与籽粒产量极显著相关。因此,选择紧凑型玉米与晚熟大豆品种搭配有利于提高套作大豆的产量,从而提高籽粒蛋白质产量。     

Influence of drying temperature on the wet-milling performance and the proteins solubility indexes of corn kernels

The effects of air drying temperature on the wet-milling performance and the proteins solubility indexes were investigated for corn kernels dried between 54 °C and 130 °C. It was observed that when the drying temperature increases, the starch yield drops significantly. The gluten recovered increased abruptly for drying temperatures up to 80 °C. The albumin, globulin and zein solubility indexes decreased continuously when corn drying temperatures increased. According to the temperatures used, the starch yield, the gluten recovered and the salt-soluble proteins solubility indexes were adjusted satisfactorily by using a two asymptotic logistic model. This model has the advantage of supplying information on the dynamic of the variation of described parameters. The solubility index of total salt-soluble proteins was shown to be a suitable indicator of the severity of the drying treatment in regard to the corn wet-milling performance.     

不同顶端调控措施对烟株内钾素积累和分配规律的影响

通过田间试验 ,研究了烤烟生长后期烟株内钾素的积累和分配。结果表明 ,烟株内的钾素积累在打顶后有一上升的过程 ,进入烟叶成熟期后则表现出下降的趋势。留顶和施加外源生长素可以使成熟期烟株内的钾素积累维持在较高的水平 ,同时钾素向叶中的分配以外源生长素处理 2次的最多。成熟叶片中的含钾量也以留顶和外源生长素处理 2次的较高。     

薄壳山核桃仁的蛋白质组成及其内源性蛋白酶活性

为了对薄壳山核桃仁中的主要蛋白质,特别是相对丰度较低的功能活性蛋白进行系统研究,以新鲜的薄壳山核桃仁为原料,利用电泳、液相串联质谱和氨基酸分析等方法,考察了薄壳山核桃仁的主要蛋白质和功能活性蛋白(抗氧化酶、内源性蛋白酶),并对内源性蛋白酶的最适pH和温度进行了研究。结果显示:薄壳山核桃仁的主要蛋白质包括11S球蛋白(58%)、7S球蛋白(17%)和9 kDa蛋白(15%),还含有0.239%超氧化物歧化酶、0.190%过氧化氢酶和0.282%内源性蛋白酶;只检测到1种蛋白酶抑制剂,并且其相对丰度极低;内源性蛋白酶在pH 3.5~5.5和40~60℃时可发挥水解活性,并在pH 4.5和50℃时活性最强;在氨基酸组成方面,薄壳山核桃仁蛋白的赖氨酸含量低(3.74%),但谷氨酸+谷氨酰胺含量(19.51%)和精氨酸含量(14.12%)高。说明国产薄壳山核桃适宜鲜食,对促进人体健康有益。     

Co-occurrence of Fusarium mycotoxins in mouldy and healthy corn from Korea

A total of 71 samples consisting of 36 mouldy and 35 visibly healthy corn were collected from Kangwon province of Korea and analysed for 8-ketotrichothecenes, zearalenone (ZEA), and fumonisins, including fumonisin B1 (FB1), fumonisin B2 (FB2), and fumonisin B3 (FB3). Five 8-ketotrichothecenes, namely deoxynivalenol (DON), 15-acetyldeoxynivalenol (15-ADON), 3-acetyldeoxynivalenol (3-ADON), nivalenol (NIV), and 4-acetylnivalenol (4-ANIV), ZEA, FB1, FB2, and FB3 were detected in corn samples. DON, 15-ADON, 3-ADON, NIV, 4-ANIV, ZEA, FB1, FB2, and FB3 were detected in mouldy corn with mean values of 4.0, 0.9, 0.2, 1.7, 0.4, 0.6, 23.2, 7.5, and 6.3mug/g, respectively. Visibly healthy corn samples were contaminated with lower levels of 8-ketotrichothecenes, ZEA, and fumonisins than mouldy corn samples. However, 5 of 35 healthy corn samples analysed were contaminated with fumonisins at high levels up to 12.5mug/g for FB1, 5.4mug/g for FB2, and 0.5mug/g for FB3. This is the first report on the simultaneous occurrence of trichothecenes, ZEA, and fumonisins in corn from Korea.     

谷蠹蛀食对玉米中淀粉及油脂品质的影响

探讨谷蠹不同虫口密度和为害时间对玉米加工品质的影响,为谷蠹蛀食玉米的有效利用和谷蠹的科学防控提供参考。以河南玉米为试材,以谷蠹为试虫,设置不同虫口密度进行为害,测定不同为害期玉米粗淀粉含量、破损淀粉含量、淀粉颗粒形貌、淀粉糊化特性、粗脂肪含量、脂肪酸值、过氧化值、品尝评分值等品质指标。结果表明：随着虫口密度和为害时间的增加,玉米品质指标变化幅度增加;谷蠹为害65 d时,各处理组玉米中粗淀粉减少幅度和破碎淀粉增加幅度都不超过8%,而在为害25 d时脂肪酸值和过氧化值上升幅度都已超过10%。初始虫口密度为15、25头/kg和5头/kg的玉米中淀粉的糊化特性分别在谷蠹为害25 d和45 d时出现明显变化,尤其是衰减值下降超过10%。另外,谷蠹为害会造成玉米淀粉颗粒形态改变,制成窝头颜色加深,表面粗糙,品尝评分值降低。因此,在玉米储藏过程中,应密切监测谷蠹虫口密度,并适时安排出库,合理进行加工,以降低损失。     

Pilot-scale production of low molecular weight peptides from corn wet milling byproducts and the antihypertensive effects in vivo and in vitro

A pilot-scale production was developed to enhance the value of proteins from corn gluten meal (CGM). Corn protein isolate (CPI) with high protein content (90.68%) was obtained through heat treatment of CGM (150 kg) in aqueous alkaline solution. Two-step enzymatic hydrolysis and multistage separation were applied to enrich corn oligopeptides (COP) with low molecular weights, 96.77% of which were less than 1000 Da. The greatest antihypertensive effect of COP treatment in spontaneously hypertensive rats (SHR) was observed at a dose of 0.45 g/kg. One major ACE-inhibitory peptide, Ala-Tyr, was identified and quantified (9.16 ± 0.08 mg/g) from COP. The ACE inhibitory activity of Ala-Tyr (IC₅₀ = 0.037 mg/ml) was over 27 times higher than that of COP (IC₅₀ = 1.020 mg/ml). The results indicate that COP may be a source of natural antihypertensive compounds that could be used for drugs or functional food ingredients.     

Localization of phenolic acids and antioxidant activity in sorghum kernels

White and red of sorghum grains were sequentially pearled into 11 pearling fines and the corresponding 11 pearled kernels to study the localization of phenolic acids within sorghum grains. All fractions were analyzed for phenolic acids content by HPLC and antioxidant capacity by FRAP assays. Four phenolic acids identified in all fractions were caffeic, p-coumaric, ferulic, and sinapic acids. Data showed that the distribution of phenolic acids and antioxidant capacity in two sorghum genotypes was heterogeneous. Around 60% of the phenolic acids and the antioxidant capacity were recovered in the initial three pearling fine fractions that constituted about 20% surface removal. The concentrations of the phenolic acids decreased significantly with sequential pearling. Significant correlation between total phenolic acids and antioxidant capacity was observed with all fractions except for the first pearling fines from the red sorghum.     

基于图像处理和神经网络的小麦不完善粒识别方法研究

为了实现图像处理技术对小麦不完善粒的准确快速识别,研究了一种基于小麦不完善粒图像特征和BP神经网络的不完善粒识别方法。采集小麦不完善粒图像,对图像进行中值滤波、形态学运算、图像分割等处理后,针对每个小麦籽粒,提取其形态、颜色和纹理共3大类54个特征参数,采用主成分分析法提取8个主成分得分向量作为模式识别的输入,建立BP神经网络模型,实现对小麦不完善粒的检测识别。结果表明,该模型对完善粒、破损粒、病斑粒、生芽粒和虫蚀粒的判别正确率分别为93%、98%、100%、90%和85%,平均判别正确率达到93%,可有效对小麦不完善粒进行检测识别。     

Occurrence of certain mycotoxins in corn and corn‐based products and thermostability of fumonisin B1 during processing

A total of 57 samples of corn and corn‐based products collected from various districts of Egypt were analyzed for Fusarium mycotoxins (T‐2, diacetoxyscripenol (DAS( deoxynivalenol (DON) and fumonisin B₁ (FB₁) and aflatoxins. FB₁ was detected in about 80%, 53.85%, 33.3%, and 28.57% of yellow corn, corn meal, white corn, and popcorn samples, respectively. The levels of FB₁ ranged from 10 to 780 μg/kg. T‐2 and DAS were detected in 5% and 10% of yellow corn samples, respectively, and DON was detected in white corn and popcorn samples at levels of 28.8 and 10.1 μg/kg, respectively. Starch samples were found to be free from Fusarium mycotoxins. Baking balady bread at 450°C/min reduced FB₁ to 72.4% while baking Franco bread at 250°C/20 min reduced FB₁ to 57.4%. Boiling of macaroni and corn in water completely removed FB₁ from contaminated samples. On the other side, corn flakes samples were found to be contaminated with aflatoxins B₁ and G₁ at levels ranging from 6 to 10 ppm, whereas 2.9% of samples were contaminated with aflatoxin B₁ > 35 ppm and G1 > 16 ppm.     

Evaluation of palm kernel meal and corn distillers grains in corn silage-based diets for lactating dairy cows

The effects of increasing levels of solvent-extracted palm kernel meal (SPKM) and corn distillers dried grains (CDG) in corn silage-based diets on feed intake and milk production were examined in 2 experiments. In Experiment 1, 20 Holstein cows averaging 100 d in milk (DIM) (SD = 61.5) at the start of the experiment were utilized in an 11-wk randomized complete block design with 4 treatments in 5 blocks to study effects of increasing levels of SPKM in the diet. During a 3-wk preliminary period, cows were fed a standard diet. At the end of the preliminary period, cows were blocked by 4% fat-corrected milk yield, parity number (primiparous and multiparous), and DIM, and were assigned randomly to 1 of 4 experimental diets. The total mixed ration (TMR) consisted of (dry matter basis) 40% corn silage, 5% coarsely chopped wheat straw, and 55% concentrate. The increasing dietary levels of SPKM were achieved by replacing protein sources and citrus pulp with SPKM and urea (0, 5, 10, and 15% SPKM and 0.06, 0.22, 0.38, and 0.55% urea for SPKM0, SPKM5, SPKM10, and SPKM15, respectively). In Experiment 2, 18 Holstein cows averaging 93 DIM (SD = 49.1) at the start of the experiment were utilized in an 11-wk randomized complete block design with 3 treatments in 6 blocks to study effects of increasing levels of CDG in the diet. The preliminary period lasted for 2 wk. Assignment of cows to treatments was the same as in Experiment 1. The TMR consisted of (dry matter basis) 40% corn silage, 5% coarsely chopped wheat straw, and 55% concentrate. The increasing dietary levels of CDG were achieved by replacing soybean meal and citrus pulp with CDG and urea (0, 7, and 14% CDG and 0, 0.22, and 0.49% urea for CDG0, CDG7, and CDG14, respectively). There were no significant treatment effects on dry matter intake, milk yield, or milk composition in Experiment 1. Inclusion of SPKM tended to increase protein and lactose contents of milk. The SPKM0 diet promoted body weight loss. There were no treatment effects in Experiment 2, except for milk protein content, which was decreased by CDG. Plasma Lys concentration tended to be affected by SPKM and CDG inclusions. Plasma concentrations of 3-methylhistidine and Leu seemed to be related to body protein degradation/synthesis. The feeding of SPKM up to 15% in the diet decreased feed costs without detrimental effects on productive responses and tended to increase milk protein content. The inclusion of CDG in diets based on corn silage and corn byproducts might decrease milk protein content due to an unbalanced supply of AA, particularly Lys.