Grain morphology and structure in relation to milled product quality in maize (Zea mays L.)

In studies of the effect of shape and size of 10 varieties maize ( Zea mays L.) grains on fat and fibre of its grits, the fat content of the whole grain (3.2–5.7%) was not related to either the shape or size. The fat of germ was positively but weakly related to that of whole grain (r = 0.447*). Removal of around 30% bran by milling reduced both fat and fibre of the grits to about 1% in all varieties except in Shakti opaque-2 which needed 50% bran removal to achieve the same result. Irrespective of size, flat grains yielded more grits (64–66%), whole germ (0.6–0.9%), bran (28.4–30.0%) and less unmilled grains (3.0–5.1%), than round grains for which the figures were: grits, 52–59%; germ, 0.5%; bran, 25.2–25.6%; and unmilled grains 15–22%. The percentages of fat and fibre in grits freed of germ were 1.2 and 0.90 in large flat, 1.82 and 0.92 in large round, 1.5 and 2.0 in small flat and 2.1 and 2.7 in small round grains respectively. Flat grains yielded more grits of low fat and low fibre than round ones, and large grains than small ones.     

Near‐Infrared Spectroscopy for Proficient Quality Evaluation of the Malt and Maize Used for Beer Production

Moisture and total nitrogen content are considered very important factors that influence barley malt quality, as well as moisture and lipid content for maize quality. In the present study, the feasibility of using Near‐Infrared (NIR) spectroscopy to measure the moisture, total nitrogen and lipid content of the whole malt grains and maize grits was examined. The NIR spectra of the following samples were examined: 295 malt whole grains for moisture, 281 malt whole grains for total nitrogen, 128 maize grits for moisture and 102 maize grits for total lipids. Validation was carried out both by means of cross‐validation and test set validation. Coefficients of determination (R²) were higher than 93% for both malt and maize moisture and higher than 71 and 80 for malt total nitrogen and maize total lipids, respectively. The Root Mean Square Error (RMSE) values (both in Cross Validation (RMSECV) and in Prediction through external validation (RMSEP)) ranged from 0.127 to 0.165% for both malt and maize moisture, whereas they ranged from 0.043 to 0.053% for malt total nitrogen and from 0.065 to 0.079% for maize total lipids. Repeatability (r₉₅) ranged from 0.105 to 0.222% and from 0.012 to 0.155% for malt moisture and total nitrogen content, respectively, and from 0.086 to 0.192% and from 0.020 to 0.171% for maize moisture and total lipid content, respectively. The findings showed that NIR spectroscopy has potential for the rapid prediction of quality of whole malt grains and maize grits for brewing.     

Grinding characteristics of carrots (Daucus carota L.)

The grinding characteristics of carrots (Daucus carota L.) in the form of grits were studied in a hammer mill. The grits were first dried to different moisture contents, before being ground to a powder; the energy required for grinding was noted. Kick's law, Rittenger's law, and Bond's law were applied to the grinding process, and the constants of these various laws were found. The moisture content of the dried grits had a significant effect on the grinding energy, which increased as moisture content increased from 10 to 15% decreased as moisture content rose to 18% and, again, increased as moisture content rose to higher values. A moisture content of 18%, therefore, could be recommended for grinding operations as it requires the least grinding energy.     

不同来源和不同方法提取玉米胚的品质对比研究

从不同玉米深加工企业采集不同提胚工艺生产的玉米胚样品,同时在实验室以优质玉米为原料采用不同工艺提取玉米胚,对玉米胚的主要组分含量、真菌毒素含量、挥发性风味成分及其中油脂品质进行检测分析,对比研究不同来源和不同方法提取玉米胚的品质。结果显示：从玉米淀粉厂所采集玉米胚的纯胚率(60.29%~88.92%)高于从玉米酒精厂所采集玉米胚(42.29%~57.25%),通过风选和筛分可将玉米胚的纯胚率提高至84.11%~97.85%。半干法玉米胚水分含量(9.09%~14.48%)高于湿法玉米胚(3.51%~5.51%),粗脂肪含量(23.63%-26.94%)明显低于湿法玉米胚(53.42%-54.77%),粗蛋白含量(13.75%-18.46%)高于湿法玉米胚(10.10%-12.35%),总氨基酸含量和必须氨基酸含量均高于湿法玉米胚。不同玉米胚毛油的脂肪酸组成和甾醇含量无明显差别,但干法玉米胚毛油中维生素E含量更高。半干法玉米胚中挥发性风味成分(38~46种)明显多于湿法玉米胚(11~36种),感官呈青草味和甜香味,颜色浅且有色泽,湿法玉米胚有哈喇味和刺激味,色泽偏黄且较为暗淡,但湿法玉米胚中玉米赤霉烯酮和呕吐毒素含量更低。以优质玉米为原料采用半干法提取的玉米胚适合做为食用玉米胚的产品开发。     

Effects of particle size and moisture content of maize grits on physical properties of expanded snacks

The main aim of this research was to investigate the effects of simultaneous changing of maize grits particle size and moisture content on some physical properties and microstructure of the expanded snacks produced by an industrial single screw extruder. Maize grits with different particle sizes of 212–299, 300–474, 475–680, 681–870, 871–1,016, and 1,017–1,070 μm and various moisture contents of 15, 16, 17, and 18% were used to manufacture puffed products. The samples produced with larger particle sizes and higher moisture content exhibited lower water absorption and water solubility indices and less expansion and crispiness than other samples. As microstructure results revealed, these samples showed more uneven surface and thicker cross‐section. Overall, controlling both moisture content and particle size of maize grits had significant effects on the quality of the snacks. However, the impact of changing particle size on the snack properties was greater than changing the moisture content. This research has implications in food industry in production of puffed snacks using extrusion process. The results provide practical and green methods of improving the quality of the snacks by choosing the appropriate feed particle size and moisture content. The approach introduced in this paper is easy to impediment in the food industry without the need to change extruder configuration or adding to the list of ingredients and additives.     

Effect of Harvest Moisture Content and Ambient Air Drying on Maize Fiber Oil Yield and its Phytosterol Composition

Effect of harvest moisture content and ambient air drying on maize fiber yield, fiber oil content and the phytosterol composition of maize fiber oil were evaluated. Maize was harvested at approximately five different harvest moisture contents (28.0, 23.0, 20.0, 18.0 and 15.0%). Effect of air drying was studied by ambient drying the maize harvested at 28.0% moisture content to 20.0 and 13.0% moisture content. Effect of both harvest moisture content and ambient air drying were significant on all the dependent variables, however, no clear trends were observed. The results suggest that as harvest moisture content goes down the amount of oil extracted from the maize fiber decreases but the concentration of the phytosterols in the maize fiber oil increases proportionally.     

Effect of Pre-Treatments on Mechanical Oil Expression of Soybean Using a Commercial Oil Expeller

The effect of expeller screw press and pre-treatments on the quality and quantity of soybean oil and cake was studied using a commercial oil expeller. The pretreatments included whole soybean crushing, soy grits crushing, and crushing of soy grits extruded at 135°C. The screw speeds were 28, 35, and 45 rpm. The moisture content of soybean used in the experiment was 10% wet basis. The average capacity of the oil expeller was found to be 145 kg/h, 110 kg/h, and 120 kg/h for whole, grits, and extrudate, respectively at 45 rpm. The average capacity of oil expression from whole soybean did not vary significantly from 28 to 45 rpm. In the case of soy grits, however, the capacity was higher when the expeller speed was lowest, i.e., 28 rpm. In the case of extrudate, even in a single pass, the recovery was higher, i.e., to 71% at both 45 and 35 rpm. The color of oil from soy grits was lighter followed by extrudate, and the color of oil obtained from whole soybean was dark. The FFA in oil from all the samples was below 1%, however the lowest percentage was for oil obtained from extrudate at 0.5%. The urease activity of the extruded cake was 0.15 pH units, and the protein and oil content were about 48% and 5%, respectively. The optimum process variables for mechanical expelling of soybean were found to be extrusion as a pretreatment and speed of expeller screw at 45 rpm, which yielded throughput capacity 103 kg/h, oil recovery of 70.5%, and urease activity of the cake at 0.15.     

Effect of Moisture Content on Pitting and Milling Efficiency of Pigeon Pea Grain

Pitting is a premilling operation in which pigeon pea grain is passed through a dehulling machine quickly to crack the hull or partly dehull the grain. A study was conducted to investigate the effect of grain moisture content on pigeon pea hull during pitting. Pitting of the grain was done at 6%, 8%, 10%, 12%, and 14% moisture contents using dhal mill developed by Central Institute of Agricultural Engineering, Bhopal (India). Grains having a cracked hull or partly dehulled during pitting varied from 35.3% to 85.3% with maximum value at 10% moisture content and reduced with an increase in moisture content. Maximum finished product in the form of dehulled whole (gota) and dehulled splits (dhal) was also obtained at 10% moisture content. Pitted grains of pigeon pea were treated with 0.28% cottonseed oil to study the effect of moisture content and pitting on dehulling efficiency, which was maximum (86.7%) at 10% moisture content.     

Small-scale production and storage quality of dry-milled degermed maize products for tropical countries

Summary A small‐scale, single operation, dry degerminator, originating from Brazil was tested on six maize samples (from France and Mali) at two moisture contents (10 and 15% wb). The yield of brewery maize grits (<1% lipids) was higher for extensively dry (10% mc) and hard grains. It ranged from 50 to 70% for four cultivars, which was equivalent or higher than for industrial plants. The rancidity of the products was controlled by the fat acidity level, which was 40–60 mg KOH 100 g^?1db, after 4 months storage of degermed flour. This indicates that degermed products can be stored at 35 °C for up to 6 months without developing significant rancid off‐flavour. Thus the Brazilian dry degerminator appears suitable for the treatment of maize in the tropical zone of Africa.     

微波处理降低小麦胚芽油中非水化磷脂含量的工艺优化

目的:获得最低非水化磷脂(nonhydratable phospholipids,NHP)含量的小麦胚芽油。方法:采用微波法处理小麦胚芽,以初始水分含量、微波时间、微波功率为影响因素,以小麦胚芽油中NHP含量为考察指标,通过L_9(3~4)正交试验优化获得最佳微波处理工艺。结果:最佳微波处理工艺为小麦胚芽初始水分含量26.0%、微波时间3 min、微波功率480 W。在此工艺条件下,微波处理小麦胚芽的小麦胚芽油提取率为9.22%,较对照和传统烘烤处理分别提高6.21%、1.09%,微波处理、对照、传统烘焙处理NHP含量分别为0.087、15.22、8.04 mg/g。结论:微波处理小麦胚芽能显著降低小麦胚芽油中的NHP含量并提高小麦胚芽油提取率。     

臭氧熏蒸对玉米胚中真菌毒素的降解消除作用

为探究臭氧熏蒸对玉米胚中真菌毒素消除效果,固定臭氧质量浓度为150 mg/L,以蒸馏水调节玉米胚水分至不同质量分数(5％、10％、15％、20％、25％、30％),并熏蒸不同时间(20、30、40、50、60、80min),分析熏蒸处理后玉米胚中真菌毒素含量以及玉米胚和玉米油品质的变化.结果表明:玉米胚水分质量分数为2...     

Nixtamalisation of maize (Zea mays L) using a single screw cook-extrusion process on lime-treated grits

The tortilla flour market is expanding but present industrial production is lagging behind in the use of modern technologies to increase production and cut costs due to the maize steeping and drying operations. A process using a single-screw cook-extruder which eliminates the traditional steeping and drying operations was therefore explored. Lime (Ca(OH)₂) suspension was absorbed onto commercial maize grits (2 g lime kg^?1 maize) and the resulting meal conditioned to various moisture contents. These samples and one which had not been lime-treated were cook-extruded through a Brabender Do-corder extrusion cooker (Type 825602). The dry extrudate was milled through a 150 μm sieve and tortillas made from each sample. The tortillas prepared from the lime-treated grits conditioned to 472 g kg^?1 moisture compared favourably with that prepared from traditionally prepared masa flour when organoleptically assessed. Flour pasting properties (viscosity) and water absorption index were not significantly different (P < 0.05) from the traditionally prepared products. Enzyme susceptible starch index did not correlate well with dough quality.     

Stability of zearalenone during extrusion of corn grits

The effects of extrusion cooking on the stability of zearalenone (ZEN) in spiked (4.4 microg/g) food-grade corn grits were investigated using a twin screw extruder. A ground rice culture material containing a high level of ZEN was used to spike the corn grits. The extrusion variables were screw type (mixing and nonmixing), temperature (120, 140, and 160 degrees C), and moisture content (18, 22, and 26%). Both unextruded and extruded samples were analyzed for ZEN by high-performance liquid chromatography. Extrusion cooking of the corn grits resulted in significant reductions of ZEN in grits extruded with either mixing screws or nonmixing screws, but use of mixing screws was somewhat more effective (66 to 83%) overall than nonmixing screws (65 to 77%). Greater reduction of ZEN was observed at either 120 or 140 degrees C than at 160 degrees C. The moisture content of corn grits was not a significant factor affecting reduction of ZEN during extrusion with either mixing or nonmixing screws.     

Evaluation of size reduction on the yield and quality of celery seed oil

The effect of grinding/flaking with and without pre-cooling of celery seeds on the yield and physical and chemical characteristics of volatile oil was evaluated. For smaller batches (200 g) with pre chilling and flaking, yields of oil were marginally but consistently higher (2.20%), compared to grinding celery at ambient temperature using a mini plate mill (1.9%) and with waring blender (1.8%). With flaking at room temperature the yield of oil was 2.0%. However, in large batches (10 kg), with steam distillation the yield of steam distilled oil was significantly higher for flaking (1.76%) as compared to the hammer mill powdering (1.4%), both at room temperature. Extraction of volatile oil from celery powder or flakes follows first order kinetics with an variance value of 0.04. Gas chromatograph (GC) and gas chromatograph–mass spectra (MS) analysis showed that in case of flaking, the volatile oil had higher levels of limonene, the major volatile compound and sedanenolide, the major character impact compound being present in almost equal quantities in both the cases of flakes and powder. Selective collection of volatile oil at different intervals of time of distillation gave products of different flavour profiles. Flaking had the advantage of higher yields of the volatile oil with better flavour quality. It was also observed that flaking of celery helped in overcoming the problem of clogging and choking which is associated with the conventional grinding.     

Effects of High Pressure Disintegration of Steeped Maize Grits on the Release of Starch Granules from the Protein Matrix

The horny endosperm of maize gives the greatest resistance to the mechanical disintegration of the protein matrix during starch extraction. Thus attempts were made to release the starch by wet-milling of maize grits in the valve of a high-pressure homogenizer. At the same time, information was gathered on the principles involved in the structural breakdown of the endosperm components. For this purpose the influence of the valve geometry as well as the concentration and flow rate of the suspension on the particle size reduction and disintegration was examined. Using a valve specially constructed for the photographic documentation of this process step, it could be shown that the slit height of the valve predominantly determined the particle size of the wet milled product. Already after a single passage through the valve, set at slit heights between 200 and 600 μm, 70% of the grits were reduced to particles <40 μm. The grits were initially between 250 and 1000 μm in size. Scanning electron microscope photographs showed that a large fraction of the mass existed as free starch granules alongside partly intact particles of the protein matrix. Since the starch granules were of higher purity after raffination, it is assumed that the extent to which disintegration of the endosperm particles results in starch granules and protein particles as separate entities, depends not only on the particle size reduction step, but also on the different visco-elastic behaviour of the protein matrix and the starch granules under the influence of the large shear forces occuring in the valve.     

响应面试验优化阿魏酰基脂肪酰基结构酯合成工艺及产物稳定性

利用响应面试验对在溶剂体系中脂肪酶Lipozyme RM IM催化玉米胚芽油与阿魏酸酸解制备阿魏酰基脂肪酰基结构酯的反应条件进行优化。在摇床转速为220 r/min的条件下,选取投料比（阿魏酸与玉米胚芽油质量比）、反应温度、反应时间3 个因素作为考察对象,以阿魏酸转化生成阿魏酰基脂肪酰基结构酯的得率为考察指标,运用Design-Expert软件的星点设计功能进行试验设计并对结果进行分析。结果表明,3 个因素均为影响阿魏酸酯化的显著因素;经响应面分析可确定最优值为投料比8.9∶1（g/g）、反应温度76.0 ℃、反应时间28.1 h。该条件下的平均得率达59.1%,与响应面拟合方程的得率预测值58.8%吻合良好。在煎炸过程中新制备的结构酯产生较低的聚合物,同时其具有较高的贮藏稳定性。     

Apparent coefficient of diffusion of carbon dioxide through samples of cereals and rapeseed

The apparent diffusion coefficients of carbon dioxide (CO₂) through rapeseed, wheat, maize and oats were determined in the laboratory using a specially designed cylindrical diffusion apparatus. The diffusion coefficient was not affected significantly (P > 0.05) by the direction of CO₂ flow in relation to force of gravity. The effect of compaction of wheat (38–42% porosity) on diffusion coefficient was not significant (P > 0.05). Coefficient of diffusion, however, decreased with increasing moisture content of wheat. At 10°C the mean diffusion coefficients of CO₂ through stored seeds were: rapeseed at 8% moisture content, 2.8; wheat at 13% moisture content, 3.5; maize at 14% moisture content, 3.0; and oats at 14.5% moisture content, 3.9 mm²/s.     

Use of a microwave-attenuation sensor for moisture measurement inside an extrusion cooker

A microwave strip line sensor has been inserted in the barrel of a pilot scale extrusion cooker immediately before the die. Experiments with maize grits have shown that the microwave attenuation is sensitive to the moisture content of the feed. Preliminary experiments with finer particulate feedstock indicate that the microwave attenuation also depends on the distribution of water within the viscous material at this point. A microwave sensor is shown to have potential for probing the material within an extrusion cooker for use in controlling product properties.     

Fusarium mycotoxins in milling streams from the commercial milling of maize imported to the UK,and relevance to current legislation

A study in three large commercial UK maize mills showed that Fusarium mycotoxins, such as deoxynivalenol, zearalenone and fumonisins present at mill intake, are distributed in milling streams approximately according to their occurrence in the maize seed structure. Fractions derived from the endosperm tended to contain the lowest levels of mycotoxins. Concentrations of mycotoxins within the endosperm are also related to the particle size. However, the products derived from the embryo or outer seed layers contained the highest mycotoxin levels being concentrated up to five times or more, although these components are normally used for animal feed or industrial use. The general pattern of mycotoxin distribution found when milling French and Argentinean maize was similar, although very variable, and it is concluded that this variability stems from different milling strategies used at each mill and from the nature and condition of each consignment of maize. Mycotoxins in maize grits (particle sizes >500 µm) were usually reduced by the greatest amount when compared with the whole maize, while flour (≤500 µm) could be both reduced or increased depending on the mill and consignment. Thus, in most situations mycotoxin concentrations in whole maize that meet European Commission legislation on intake should give rise to levels in milled ingredients that should also do so. However, this was not always true in some ingredients, especially for fumonisins in those fractions with particle size ≤500 µm.     

Impact of moisture content and maize weevils on maize quality during hermetic and non-hermetic storage

The objective of this study was to determine the impact of moisture content and Sitophilus zeamais Motschulsky on maize quality during hermetic and non-hermetic storage conditions. Commercial Channel 211-97 hybrid maize kernels were conditioned to 14, 16, 18, and 20% moisture content (wet basis), and then three replications of 300 g of maize grain were stored in glass jars or triple Ziploc^® slider 66-μm(2.6-mil) polyethylene bags at four conditions: hermetic with weevils, hermetic no-weevils, non-hermetic with weevils, non-hermetic no-weevils. All jars and bags were stored in an environmental chamber at 27 °C and 70% relative humidity for either 30 or 60 d. At the end of each storage period, jars and bags were assessed for visual mold growth, mycotoxin levels, gas concentrations, pH level, the numbers of live and dead S. zeamais, and maize moisture content. The maize stored in non-hermetic conditions with weevils at 18 and 20% exhibited high levels of mold growth and aflatoxin contamination (>150 ppb). Conversely, very little mold growth was observed in maize stored in hermetic, and no aflatoxins were detected in any moisture level. CO₂ increased and O₂ gradually decreased as storage time increased for maize stored in hermetic conditions (with or without weevils) in all moisture level. No significant difference in pH was observed in any storage conditions (P < 0.05). Total mortality (100%) of S. zeamais was observed in all hermetically stored samples at the end of 60 days storage. Moisture content for hermetically stored maize was relatively constant. A positive correlation between moisture content and storage time was observed for maize stored in non-hermetic with weevils (r = 0.96, P < 0.05). The results indicate that moisture content and the number of S. zeamais weevils plays a significant role in maize storage, both under hermetic and non-hermetic conditions.