基于X射线断层扫描的小麦籽粒霉变结构研究

食品微观结构在确定其最终产品性能方面起着至关重要的作用,霉菌又是粮食储藏期危害非常严重的微生物类群,目前对粮粒感染霉菌后的研究多是间接的、破坏性的,无损的研究食品感染霉菌后内部微观结构的变化非常困难。X射线断层扫描技术提供了一个极好的工具来无损的评估食品内部的组分,本研究利用X射线断层扫描法实现了小麦籽粒发霉后内部特征的三维可视化和定量分析。利用图像滤波、阈值分割、重建算法对X射线断层扫描获取的图像进行重建和渲染,实现了感染籽粒及内部孔隙的三维可视化,除了可视化还获取了如籽粒体积、籽粒内部孔隙率等参数。X射线断层扫描是一种强有力的工具,可以用于粮食储藏期间易发霉部位如(粮仓墙壁附近、粮粒表层)以及粮食在深加工前是否霉变的区分检测,用于无损检测单颗小麦籽粒等生物材料的损伤和微观结构组织的变化。     

射线辐照对粮食微观结构及其萌发特性的影响

分别采用0～10 kGy的电子束和γ射线辐照小麦、稻谷、玉米和大豆,对其微观结构进行观察。结果发现,不同种类不同剂量射线辐照粮食后,其微观结构均受到不同程度的影响。电子束辐照后,小麦胚乳淀粉和蛋白质基质结合松散,稻谷胚乳中出现裂纹,玉米和大豆种胚细胞组织遭到破坏,细胞内含物外渗;γ射线辐照粮食后,粮粒微观结构变化趋势和电子束辐照相似。随着两种射线辐照剂量的升高,射线对粮粒内部微观结构的损伤、破坏程度增大。粮食发芽率的试验结果发现,辐照处理后粮食发芽率均降低,不同粮种随射线种类和辐照剂量不同,其发芽率降低程度有所不同。辐照剂量越大,发芽率越低,当两种射线辐照剂量达到10 kGy时,4种粮食发芽率均为0。比较发现,同剂量的γ射线辐照对粮食微观结构和发芽率的影响大于电子束辐照。     

主要粮食品种储藏期间霉菌活动特性研究

研究了稻谷、玉米和小麦在25℃,相对湿度分别为75%、85%和95%储藏,以及在高于安全水分2%的相似水活度条件下储藏期间霉菌的活动特性.结果表明,小麦最易出现霉菌生长活动,稻谷的抗霉菌生长作用最强,玉米介于小麦和稻谷之间;其中85%相对湿度下储藏至28 d,小麦的微生物活性值升高了475 u,分别是稻谷和玉米同期升高值的5.6和3.5倍.储粮中霉菌活动特性的不同表现与各粮种的吸湿性能及粮粒外皮(颖壳或种皮)的霉菌可生长性差异有关,但将相同霉菌活动强度的储粮样品作相关品质指标的检测,发现小麦的黏度、发芽率变化不明显,而玉米和稻谷的脂肪酸值和发芽率则有较大的变化.因此,对于储藏品质较稳定但易滋长霉菌的小麦应该重点关注霉菌活动的状况,仅仅监测品质指标变化难以准确判断储藏的安全性和粮食相关的食品安全性.     

图像分析技术在谷物食品研究中的新应用

介绍了近几年来图像分析技术在谷物食品结构研究中的应用新进展。其中利用磁共振成像技术对面包孔洞组织进行2D平面的非侵入性扫描研究，分辨率高，并且可以对面包生产过程中气孔动态变化进行追踪和统计；X光计算机微观断层扫描技术在计算机辅助下可以将物体不同角度X光扫描图像进行重建组合，将物体内部3D立体结构重现，并对任意平面进行非侵入性统计研究。     

基于X射线断层扫描的小麦籽粒模型构建及离散元参数标定

为构建精准的离散元模型,标定离散元仿真参数,本文以小麦为研究对象,基于X射线断层扫描技术获取1024张不同灰度值的二维切片,采用图像滤波、图像分割等算法构建小麦籽粒的三维外轮廓模型;在EDEM中导入小麦外轮廓模型,构建了4种不同数量的填充球模型来拟合小麦籽粒的真实形状;通过休止角实际实验与EDEM仿真实验,运用Plackett-Burman实验、最陡爬坡实验、响应面优化实验标定了小麦离散元仿真参数;最后对标定的离散元参数进行仿真分析并与实际实验进行对比,发现仿真值与实际值相对误差小于1.30%,表明本文方法构建的离散元模型及标定的参数可用于仿真实验。     

粮食储藏生理性变质研究进展

粮食是人类赖以生存的物质基础,粮食储藏变质对农业生产及食品加工影响巨大。粮食生理劣变是一个复杂、渐进的物理、化学与生物学过程,与其籽粒的生理活动密切相关。研究表明,粮食籽粒酶活性降低,呼吸作用下降,生命力减弱等是其生理变质的外在表现,储粮生理活动是引发其生理劣变的本质要素。深入了解粮食籽粒在储藏过程中生理活动及其变化规律对揭示储藏生理变质机理具有重要意义。本文主要介绍了粮食籽粒储藏衰老过程中种胚微观结构、营养物质转化、线粒体呼吸作用、细胞抗氧化系统、遗传物质变异等的研究现状,并对粮食储藏保鲜原理进行讨论,以期为提出延缓和预测粮食储藏劣变的方法提供参考。     

基于计算机视觉的粮粒内部害虫检测的研究进展

计算机视觉技术检测粮粒内部害虫,具有快速、准确、可视化等优点,近10年来一直是粮虫领域的研究热点,国外学者做了大量的研究工作.为了充分利用国外的最新研究成果,该文分近红外图像、软X射线和CT成像三个方面,综述了国外在应用计算机视觉技术自动检测粮粒内部害虫中的研究进展,分析了各种方法的优缺点,并提出了需要进一步解决的问题,以供我国研究人员做同类研究时参考.     

黄曲霉毒素的去除方法

对于己被黄曲霉毒素污染的食品或怀疑含有黄曲霉毒素的发霉食物,用下列方法处理后均可收到较好的杀菌去毒效果.剔选、辗磨法:霉菌毒素的污染,往往集中于部分粮食、特别是霉坏的粮粒中,因此剔选可以部分去毒.有人试验,经人工挑选后,可使花生黄曲霉毒素     

浅析小麦面粉储藏技术

小麦面粉是直接食用的粮食,由于失去皮层的保护,营养物质暴露,氧化作用旺盛,且极易遭到害虫和霉菌感染。为了做好小麦面粉的储藏,延缓其食用品质下降,就必须了解小麦面粉的储藏特性及其在储藏期间的变化,以探索出适合本地区小麦面粉储藏的技术,确保小麦面粉安全储藏。     

浅析小麦面粉储藏技术

小麦面粉是直接食用的粮食,由于失去皮层的保护,营养物质暴露,氧化作用旺盛,且极易遭到害虫和霉菌感染。为了做好小麦面粉的储藏,延缓其食用品质下降,就必须了解小麦面粉的储藏特性及其在储藏期间的变化,以探索出适合本地区小麦面粉储藏的技术,确保小麦面粉安全储藏。     

X-ray micro-computed tomography of cellular food products

Modern food processing is increasingly concerned with the production of products with complex aerated microstructures which determine to a large extent the mechanical and aesthetic properties of these products. The development and analysis of such new materials require non-invasive techniques for visualisation and measurement of the internal microstructure. This paper describes the imaging, visualisation and analysis of the three-dimensional (3D) cellular microstructure of a number of food products (aerated chocolate, mousse, marshmallow and muffin) using X-ray micro-computed tomography. A 3D model of the foam microstructure is determined and, by combining image analysis with a stereological technique, quantitative information is obtained on a number of parameters including spatial cell size distribution, cell wall-thickness distribution, connectivity, and voidage. The work shows that X-ray micro-computed tomography is an elegant and useful tool for the study of the 3D structure of cellular food materials.     

Effect of fibers and whole grain content on quality attributes of extruded cereals

Incorporation of fiber in cereals may lead to quality issues, thus decreasing consumer acceptance. This is partially due to deterioration of the microstructure, one of the primary quality attributes of cereals. The objective of this study was to better understand the mechanisms by which dietary fibers affect the quality of cereal products during extrusioncooking. The study quantified the effect of amount and type of fiber and whole grain on (i) texture, (ii) structure, and (iii) rehydration properties of extruded cereals. New innovative methods were applied and combined with traditional techniques to characterize both the structure and the rehydration properties. Extruded cereals were produced using a starch-based recipe (whole and wheat flours) and two sources of fibers (oat bran concentrate and wheat bran). The oat and wheat bran levels used in this study were 0, 10, and 20%. The different mixtures were extruded in a pilot twinscrew extruder BC21 (Clextral) and then sugar coated after drying. Mechanical properties of extruded cereals were investigated by compression test. The cellular structure was observed by X-ray tomography. The quality of coating (thickness, homogeneity) was analyzed by optical coherence tomography. The rehydration properties of such cereals in milk were evaluated by magnetic resonance imaging and optical coherence tomography. This work revealed that structure assessment of extruded cereals may lead to a better understanding of the effect of fiber addition on texture and rehydration properties. The application of innovative methods, such as optical coherence tomography and magnetic resonance imaging, was found to be useful to quantify the structural properties.     

层-层正交角联锁机织物及其复合材料的结构及其层切破坏机制研究

采用无损高分辨率X射线成像(显微X-CT)技术对层-层正交角联锁机织物以及复合材料内部结构进行分析,并研究了层间剪切强度与结构之间的关系;通过三维重构展现了机织物的层-层正交角联锁的微观结构,观察到机织物内部的单丝扭转、挤压现象;依据机织复合材料中孔隙和高密度杂质在三维空间的分布,计算了其相应的占比。结果表明：层间剪切实验后的机织复合材料虽然宏观形貌保持了良好的完整性,但内部存在孔隙变形、分层、纤维弯曲、片层断裂等现象;层-层正交角联锁机织结构有效提高了复合材料的层间力学性能,内部的缺陷对复合材料的力学性能有较大的影响;无损高分辨X射线成像技术是研究纤维增强复合材料内部复杂结构特性的有利手段。     

Novel implementation of laser ablation tomography as an alternative technique to assess grain quality and internal insect development in stored products

In the last century, there have been important advances in peering inside the internal grain environment. This has included electrical conductance mills, acoustical tools, near-infrared spectroscopy, and soft X-ray imaging. Each technique has their own advantages and limitations. In this current study, we describe a novel process for assessing grain quality and internal insect development in grain using laser ablation tomography (LATscan) and compare it to soft X-ray imaging for three life stages (larva, pupa, adult) of Sitophilus zeamais and Rhyzopertha dominica. Our results suggest that X-rays overestimated grain volume loss by about a quarter compared to LATscan. Moreover, LATscan produces a rich digital dataset on the level of microns that can be explored to ask biologically-relevant questions. We discuss the current limitations of LATscan in context with other techniques. Ultimately, the results highlight LATscan as a useful additional tool to further our understanding pest-commodity interactions in the postharvest supply chain.     

一种快速粮情检测仪应用试验

基于真菌代谢的基本原理,开发了一种快速粮情检测仪.采用该仪器对不同水分的实验室小麦样品和实仓小麦中CO2、湿度变化进行了研究.结果表明,小麦储藏过程中CO2浓度和湿度的变化与危害真菌的生长有明显的相关性,通过检测储藏小麦中CO2和湿度的变化可对小麦储藏真菌危害进行早期的检测.     

Safety of Oxygreen, an ozone treatment on wheat grains. Part 2. Is there a substantial equivalence between Oxygreen-treated wheat grains and untreated wheat grains?

The Oxygreen process is a new process based on wheat grain treatment by ozone (produced in situ), in a closed sequential batch reactor. The Oxygreen process offers a close, homogeneous, and controlled contact between the gas and the grain. It is proposed for use for wheat grain decontamination (insects, fungi, bacteria, mycotoxins, pesticides). It takes place in classical milling diagram, and occurs after grain cleaning and before milling. The aim of the study reported here was to determine if Oxygreen treatment could induce in the grain the formation of processing-related compounds, and if these compounds are specific or could be recognized as classical modifications already used in the cereal industry (milling, baking). Studies were performed in order to evaluate any effect of Oxygreen treatment on vitamins, ferulic acid, phytates, proteins, carbohydrates, and lipids. It was concluded that there was no detectable substantial difference between ozone-treated grains and the untreated ones, although some quantitative differences can occur. The more detectable differences concern concentration of free sugars, and inhibition of some oxidative enzymes. These quantitative differences are very slight compared to the modifications that occur in dough, after addition of oxidative products directly in flour, or during kneading and dough fermentation.     

Zinc bioavailability in wheat grain in relation to phosphorus fertiliser,crop sequence and mycorrhizal fungi

BACKGROUND: While human diets are often deficient in zinc (Zn), the impacts of crop management on Zn in cereal grains are rarely examined. In this study the effect of phosphorus (P) fertiliser and crop sequence (wheat following canola, linola, fallow or pasture) on wheat grain Zn concentration and bioavailability for humans was investigated. RESULTS: The Zn concentration of wheat grain decreased by 33–39% in response to P fertiliser. It was also 30–40% lower for crops following canola and fallow than for those following linola and pasture. P fertiliser decreased the colonisation of arbuscular mycorrhizal fungi (AMF) in wheat roots, and canola and fallow led to lower colonisation than linola and pasture. Since AMF are known to assist in soil uptake of immobile nutrients such as Zn, it is hypothesised that P fertiliser and crop sequence affected grain Zn concentration through AMF. P fertiliser also increased the concentrations of grain P by 17% and grain phytic acid (PA) by 19%, but had little effect on the concentrations of calcium (Ca), iron (Fe) and polyphenols. Other impacts of crop sequence were slightly higher concentrations in grain of P after pasture and Fe after canola. The bioavailability of grain Zn, as shown by the PA:Zn and Ca × PA:Zn molar ratios, mostly reflected Zn concentration and was low in all treatments. After milling, the PA:Zn molar ratio suggested low Zn bioavailability for flour from wheat grown with P fertiliser after canola or fallow. CONCLUSION: Crop management can affect the bioavailability of Zn in wheat grain, with practices leading to high yields potentially leading to low Zn bioavailability. Copyright © 2008 Society of Chemical Industry     

Penetration of ozone into columns of stored grains and effects on chemical composition and processing performance

Previous investigations have indicated the effectiveness of ozonation to control insects and fungi in stored grain. To further evaluate the efficacy of ozone for pest control, the current study investigated the flow characteristics of ozone through a less porous grain than maize such as wheat, and the effects of long exposure to a high ozone concentration (50 ppm) on grain quality for end-users of the grain. The flow of ozone through a 3-m column of wheat was similar to that previously observed for maize, having a Phase 1 in which the ozone rapidly degraded as the ozone front moved through the grain and a Phase 2 in which the ozone moved freely through the grain with little degradation. Increasing the velocity of ozone flow from 0.02 to 0.04 m/s facilitated deeper penetration of wheat in a Phase 1 state. Treatment of grains with 50 ppm ozone for 30 d had no detrimental effect on popping volume of popcorn, fatty acid and amino acid composition of soybean, wheat, and maize, milling characteristics of wheat and maize, baking characteristics of wheat, and stickiness of rice. These data indicate that, if repeated ozone treatments are needed, such treatment should not decrease the quality of grain for end-users.