Microstructure of Feta Cheese Made Using Different Cultures as Determined by Confocal Scanning Laser Microscopy

ABSTRACT: The objective of this work was to observe the microstructure of feta cheese using confocal scanning laser microscopy. Low fat cheese and cheese containing capsule-producing cultures were made. The protein network was observed using the reflectance mode of the confocal microscope. Fat was stained by Nile red dye diluted with whey. More even distribution of fat with a larger number of smaller globules was observed in cheese made with noncapsule-forming culture compared to that made with the capsule-forming culture. Nonfat cheese had compact structure when made with noncapsule-forming culture which contrasted with the open structure observed in cheese made with the capsule-forming culture     

共焦激光扫描显微镜及其在造纸科学中的应用

共焦激光扫描显微镜（CLSM）是一种综合了光学，电子，机械和计算机及数字图像处理等高新技术的具有高的横向和纵向分辨率的新型表面检测设备，它具有独特的光学切片功能，可以在自然环境下对样品表面进行无损探测，本文介绍了共焦激光扫描显微镜的组成和工作原理，并讨论了其在研究纤维超微结构，纤维形态学，纸张结构和性能等造纸科学研究中的应用。     

Proso millet (Panicum miliaceum L.): An Evaluation of the Microstructural Changes in the Endosperm during the Malting Process by Using Scanning‐Electron and Confocal Laser Microscopy

Scanning electron microscopy (SEM) and confocal scanning laser microscopy (CLSM) were used to investigate the micro‐structural changes in the endosperm during the malting process. SEM was a suitable tool to characterise the microstructural constitution of starch granules in proso millet and the changes occurring during malting. An early visible degradation (after 24 h) of starch granules located in the floury endosperm, which is close to the embryo, could be observed. Due to this degradation, using confocal scanning laser microscopy, a less dense packaging of this part of the endosperm was observed. Degradation of starch granules in the vitreous endosperm was obvious at a distinct later stage of malting (78 h) and a preferred attack of small granules (>2.5 μm) was detected. Changes in protein structure could not be detected by either SEM or CLSM.     

扫描电镜法分析常见可食用淀粉颗粒的超微形貌

运用扫描电镜对多种常见可食用淀粉颗粒的超微形貌进行观察,按照淀粉颗粒形貌差别,将考察的所有种类淀粉颗粒分为：块茎形、棒形、球形、扁平形、复粒结构、棱角圆滑和棱角尖锐多面体形及肾形等类别,对每一类及每一种淀粉颗粒超微形貌的特征都分别进行分析和总结,并归纳淀粉颗粒超微形貌特征规律。在本研究成果的基础上初步形成可食用淀粉颗粒超微形貌电镜照片集锦,为从淀粉颗粒超微形貌特征上加强国内淀粉产品的质量监管提供可靠参考。     

Environmental Scanning Electron Microscopy Evaluation of Tortilla Chip Microstructure During Deep-Fat Frying

When the baked chip was immersed in the fryer, oil immediately coated and clung to the surface and began to move into the chip. As heat built up within the chip, the moisture turned to steam and exited the chip leaving behind a sponge-like network of tunnels which became filled with oil. The transformations occurred within 20 sec. As frying time increased, (1) starch granules with strong birefringence remained on the surface of the chip, (2) starch granules lost birefringence within the chip, and (3) the interior of the chip became smooth and plastic in appearance as protein, starch and lipids interacted to form a continuous phase that hardened upon dehydration.     

Retrospective Shading Correction of Confocal Laser Scanning Microscopy Beef Images for Three-Dimensional Visualization

Because of the inherent imperfections of the image formation process, confocal laser scanning microscopy (CLSM) images are often corrupted by spurious intensity variations not present in the original scene, which is usually referred to as shading or intensity inhomogeneity. In this paper, a retrospective shading correction method for CLSM beef images was developed using a hybrid of image processing algorithms. A partial-differential-equation-based diffusion technique was applied, firstly, to reduce the additive shading component. To reduce the computational burden, a thresholding segmentation method was then presented to separate the muscle tissues from the background. After that, a robust, automatic, and fast method was applied for reduction of multiplicative shading component. The corrected images were finally used to construct a three-dimensional beef image, which could provide a valuable source of knowledge about beef microstructure that cannot be obtained via traditional two-dimensional images.     

茶多酚对面团中面筋蛋白结构的影响

本研究通过对面团面筋中自由氨基和二硫键含量的检测,并采用拉曼光谱和扫描电镜对面团结构的分析,探究茶多酚对面筋蛋白结构的影响。结果表明,茶多酚在面团中添加量为0.5%、1.0%、2.0%时,面团中湿面筋的含量分别降低了17.8%、66.3%和93.3%;游离氨基含量分别增加了57%、151%和313%;自由巯基含量分别增加了48%、69%、111%。拉曼光谱分析表明茶多酚的添加使得面团中的氢键作用有所增强;蛋白质二级结构的分析表明,2.0%的茶多酚降低了α-螺旋的相对含量(21.9%),而β-折叠和无规则卷曲结构则分别增加了17.2%和5.1%;随着茶多酚添加量的增加,色氨酸残基I₇₅₇相对强度逐渐降低,并且二硫键的扭-扭-反结构分别增加了3.0%、6.0%、13.4%。综上所述,茶多酚的添加破坏了面筋蛋白网络结构,与扫描电镜和激光共聚焦显微镜的结果一致。因此,防止茶多酚与面筋蛋白的相互作用是开发含有多酚类功能性面制品的基础。     

The Effect of Milk Processing on the Microstructure of the Milk Fat Globule and Rennet Induced Gel Observed Using Confocal Laser Scanning Microscopy

ABSTRACT: Confocal laser scanning microscopy (CLSM) was successfully used to observe the effect of milk processing on the size and the morphology of the milk fat globule in raw milk, raw ultrafiltered milk, and standardized and pasteurized milk prepared for cheese manufacture (cheese-milk) and commercial pasteurized and homogenized milk. Fat globule size distributions for the milk preparations were analyzed using both image analysis and light scattering and both measurements produced similar data trends. Changes to the native milk fat globule membrane (MFGM) were tracked using a MFGM specific fluorescent stain that allowed MFGM proteins and adsorbed proteins to be differentiated on the fat globule surface. Sodium dodecyl sulfate polyacrylamide gel electrophoresis confirmed the identity of native MFGM proteins isolated from the surface of fat globules within raw, UF retentate, and cheese-milk preparations, whereas only casein was detected on the surface of fat globules in homogenized milk. The microstructure, porosity, and gel strength of the rennet induced gel made from raw milk and cheese-milk was also found to be comparable and significantly different to that made from homogenized milk. Our results highlight the potential use of CLSM as a tool to observe the structural details of the fat globule and associated membrane close to its native environment.     

Comparison of Size Characterization of Barley Starch Granules Determined by Electron and Optical Microscopy,Low Angle Laser Light Scattering and Gravitational Field-Flow Fractionation

Several methods were used for the characterization of starch granules isolated from barley kernels. A procedure based on a combination of alkaline digestion, toluene treatment and filtration over sieves with pore diameters of 70 and 40 μm was used for isolation and purification of starch granules from kernels. The released starch granules were characterized by various methods: scanning electron microscopy (SEM), image analysis of optical microscopy data (IAOM), low angle laser light scattering (LALLS), and gravitational field-flow fractionation (GFFF). All methods showed the bimodal size distribution of the isolated starch granules, however, they differed in the ratio of large and small starch granules. LALLS and GFFF were also used for determination of the ratio of large and small starch granules (ratio A/B) isolated from two malting barley cultivars Kompakt and Akcent. Both techniques determined the higher ratio A/B for the cultivar Akcent. SEM was also used to examine the extent of digestion. The micrographs indicate that a significant proportion mainly of small granules are still embedded into residues of endosperm and a more extensive digestion must be performed to release all starch granules from barley kernels.     

Examination of Exopolysaccharide Produced by Lactobacillus delbrueckii subsp. bulgaricus Using Confocal Laser Scanning and Scanning Electron Microscopy Techniques

ABSTRACT: Exopolysaccharide (EPS) produced by Lactobacillus delbrueckii subsp. bulgaricus NCFB 2483 (2483) was examined using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) techniques. These microscopy techniques were used to probe the location and distribution of EPS in milk permeate-based media. In CLSM, lectin (SBA) (from Glycine max ) Alexa Fluor 488 conjugate was used to stain the EPS. The EPS appeared randomly distributed as aggregates in the culture media. The CLSM technique was simple to perform with minimal sample preparation, was nonintrusive, and allowed in-situ examination of EPS. At high magnifications using SEM, the EPS aggregates appeared as web-like structures distributed through the interstices of the protein matrix. The web-like structures were apparent, especially in the sample treated with Flavourzyme, which hydrolyzed the milk proteins. The formation of the intricate web-like structures could be attributed to the dehydration of the EPS during the critical point drying process of the SEM specimens. The present investigation also found that the 2483 EPS network remained intact at neutral or low pH (approximately 3.9). However, the 2483 EPS was highly susceptible under alkaline pH conditions. Increasing the pH from 8 to 10 appeared to destroy EPS structure as indicated by a loss of its "ropy" characteristics as well as the EPS levels.     

Evaluation of Fat Uptake of Polysaccharide Coatings on Deep-Fat Fried Potato Chips by Confocal Laser Scanning Microscopy

In the present investigation, potato slices of 3 cm diameter and 1.5 mm thickness with edible coating (1% Okra and 1% Okra + Carrageen polysaccharide coating solutions) and without any coating treatment (control samples) were fried in sunflower oil at temperatures from 170–180°C for 5 min. Confocal laser scanning microscopy of fried chips was recorded using fluorescence mode of the microscope. We observed gas cells and fat globules in the confocal laser scanning microscopy micrographs of fried chips. The results indicated that both 1% Okra and 1% Okra + Carrageen polysaccharide were effective in reducing the moisture loss and decreasing oil uptake (p ≤ 0.05), but we found the highest effect in those samples treated with 1% Okra + Carrageen polysaccharide coating. These results substantiate the application of edible coating with 1% Okra and 1% Okra + Carrageen polysaccharide to the potato chips resulting in better moisture retention capacity, eventually leading to chips with lower fat content.     

Scanning Electron Microscopy, Rheological Characteristics, and Bread-Baking Performance of Wheat-Flour Dough as Affected by Enzymes

ABSTRACT The rheological and scanning electron microscopic studies of bread doughs treated with fungal α-amylase (FA), glucose oxidase (GO), protease (PRO), and xylanase (XY) showed that addition of FA or PRO decreased, whereas XY or GO increased the dough stability, resistance to extension, and area, respectively. A micrograph of bread with FA showed some slight deformation in starch granules. In bread dough with GO and PRO, protein matrix could be seen as aggregates and broken segments. Thinning of the protein matrix was observed in XY-treated dough. The quality of bread was best with XY, as it produced the highest improvement in specific loaf volume and overall quality score.     

淀粉颗粒形貌表征研究进展

淀粉是一种非常重要的营养物质,同时也是重要的工业原料。在淀粉应用研究中,淀粉的加工及改性一直是研究的热点。近些年,人们对淀粉改性后结构及性能进行了深入的研究,发现淀粉改性对其颗粒形貌有明显影响,导致其性能有一定程度改变。因此,对淀粉改性前后颗粒形貌的表征尤为关键。本文概述了目前淀粉颗粒形貌的表征方法,并对其进行了比较,有助于大家正确选择合适的表征方法。     

Investigation of Microfibril Angle of Flax Fibers Using X-Ray Diffraction and Scanning Electron Microscopy

ABSTRACT

Microfibril angle (MFA) of secondary cell wall has an important effect on the mechanical properties of flax fibers. It is therefore essential to study the relationships between MFA and mechanical properties. This paper investigated MFA of seven flax fibers by using X-ray diffraction (0.6T method) and scanning electron microscopy (SEM; direct observation). The results showed that there is no significant difference between MFA obtained by X-ray diffraction (6.2–7.2°) and SEM (5.8–7.3°). Correlation analysis results showed a good linear correlation (>0.9) between two methods.     

运用免疫亲和柱和高效液相色谱(HPLC)检测啤酒大麦中的脱氧雪腐镰刀菌烯醇

采用免疫亲和柱净化、高效液相色谱定量等方法对啤酒大麦中的脱氧雪腐镰刀菌烯醇(DON)进行检测。向啤酒大麦中加入标准品,加标的范围在0.10～2.00μg/g,加标回收率为92.04%～97.29%,相对标准偏差是0.92%～2.67%。检出限是0.01μg/g。所测样品中DON的含量范围在0.0123～0.0926μg/g,其中江浙、云南和东北产区的啤酒大麦中DON含量较高。     

荞麦蜂花粉破壁扫描电子显微镜分析及黄酮模拟消化释放

以扫描电子显微镜法研究荞麦蜂花粉低温聚能超声破壁过程,发现在外加聚能超声作用下,蜂花粉破壁是沿3个萌发沟裂开,接着破裂,最后破碎的过程,据此提出电子显微镜视野中更加精准的破壁率计算方法。在扫描电子显微镜观测指导下,获得最佳的破壁条件为初始温度0℃、超声功率400 W、脉冲通断比1∶2、超声时间30 min、料液比1∶30(g/mL),在此条件下,破壁率达98.33%。进一步研究发现,破壁率与蜂花粉细胞内黄酮在模拟肠胃液中的总释放率呈线性增加关系,线性方程为y=0.363 8x+27.172,R²=0.999 7。     

扫描电镜和稳定碳同位素比质谱法鉴别马铃薯淀粉中的掺假玉米淀粉

为有效辨别食用淀粉掺假,运用扫描电镜和稳定碳同位素比质谱技术对马铃薯淀粉中掺假玉米淀粉行为进行定性和半定量鉴别。根据马铃薯淀粉与玉米淀粉在颗粒超微形貌上的明显差别,运用扫描电镜清晰辨别出马铃薯淀粉中掺假的玉米淀粉颗粒。当玉米淀粉的掺假量大于10% 时,根据二者在稳定碳同位素比上的自然显著差异,稳定碳同位素比法不仅能够定性鉴别马铃薯淀粉中的玉米淀粉掺假行为,而且依照给出的公式可以估算出掺假玉米淀粉的含量。本法可作为国内淀粉市场上产品质量监督的检测方法。     

大豆球蛋白-花青素Pickering乳液性质

制备大豆分离蛋白(soybean protein isolate,SPI)与花青素(anthocyanin,ACN)共价复合Pickering乳液。研究不同ACN体积分数下,共价复合颗粒的表面疏水性,Pickering乳液的乳化性与乳化稳定性、流变性质和微观结构。结果显示,当ACN体积分数由0%增加到0.15%时,共价复合颗粒的表面疏水性由18 174降低到8 945;Pickering乳液的乳化性增加了127 m2/g,乳化稳定性增加了近1倍;同时乳液脂滴状态得到了明显的改善。实验结果证明,乳液呈现类固体特性,表现出典型非牛顿假塑性行为。本研究还发现,随着ACN的添加,SPI-ACN共价复合Pickering乳液呈现出桥接乳液形态,这将为食品行业中开发新型Pickering乳液提供理论参考。     

Studies of Microstructure of Kernels of Macadamia integrifolia and Its Hybrids through MRI, X-Ray Tomography and Confocal Microscopy

The aim of this study was to apply the existing techniques that enable examination ofmacadamia kernels to provide a better understanding of physico-chemical properties of kernels during postharvest processing. These techniques, such as X-ray tomography, could be applied for quality monitoring in the macadamia industry. The objectives of this study were to investigate the browning centre symptoms that usually occur in macadamia nuts-in-shell. The applied techniques included confocal microscopy, X-ray tomography and magnetic resonance imaging （MRI）. Five different varieties of macadamia nuts （A38, 246, 816, 842 and Daddow） were selected to include distinct characteristics, such as drop pattern and growing location. Analysis of the microstructure of kernels by confocal microscopy showed the distribution of possible brown pigment compounds as well as the distribution of lipids, carbohydrates and proteins inside macadamia cells. Physical properties data, including shell density and seed to volume ratio, were obtained by X-ray tomography. Magnetic resonance diffusion tensor imaging used in this study showed marked differences in microstructure which indicate that different varieties exhibit different microstructures expressed as fraction ofanisotropy and apparent diffusion coefficient that appear to be related to the occurrence of the brown centre. Hence, the findings of this study have potential to improve the existing postharvest techniques used in the macadamia processing industry. They will be of benefit to the industry in terms of improved quality control and cost reduction.