Microstructure of Buckwheat and Barley During Malting Observed by Confocal Scanning Laser Microscopy and Scanning Electron Microscopy

The structures of buckwheat and barley were observed by Scanning Electron Microscopy (SEM) and Confocal Scanning Laser Microscopy (CSLM) throughout the malting process. SEM and CSLM have different merits when studying grains and seeds. SEM can be used to study the detailed structure (high magnifications can be achieved) and CSLM to study the overall change in structure during processing. SEM proved that buckwheat starch is degraded by both pitting and surface erosion. A concentric sphere structure was visible when buckwheat starch granules were partly broken down. With CSLM, the organization of protein and starch of buckwheat and barley could be examined independently in projections and images visualizing the 3D structure. CSLM proved that buckwheat starch is surrounded by a protein matrix. Buckwheat protein was structured and surrounded starch granules, while barley protein was present in an amorphous mass through the endosperm. The differences in overall structure between unmalted and malted seeds were evident, as the starch and protein in both the barley and buckwheat were degraded. CSLM may be used in the future to couple processing characteristics to the structure of grains and seeds.     

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.     

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。     

Confocal scanning laser microscopy and quantitative image analysis: application to cream cheese microstructure investigation

The naked eye observation of cream cheese confocal scanning laser microscopy images only provides qualitative information about its microstructure. Because those products are dense dairy gels, confocal scanning laser microscopy images of 2 different cream cheeses may appear close. Quantitative image analysis is then necessary to compensate for human eye deficiency (e.g., lack of precision, subjectivity). Two kinds of quantitative image analysis were performed in this study: high-order statistical methods and grayscale mathematical morphology. They were applied to study the microstructure of 3 different cream cheeses (same manufacturing process, same dry matter content, but different fat and protein contents). Advantages and drawbacks of both methods are reviewed. The way they may be used to describe cream cheese microstructure is also presented.     

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.     

Texture of Cheddar Cheese as Influenced by Fat Reduction

Cheddar cheeses with five different fat levels (34, 32, 27, 21, and 13 %) were manufactured in a randomized block design experiment and replicated four times. Cheeses were ripened for 4 months at 7°C. Microstructure was studied using Scanning Electron Microscopy (SEM). Texture characteristics (adhesiveness, cohesiveness, hardness, and springiness) were determined by Texture Profile Analysis (TPA) using the Instron Universal Testing Machine and a trained sensory panel. Scanning electron micrographs showed that the open-intricate microstructure of the cheeses was lost with a decrease in fat content. Hardness and springiness increased while adhesiveness and cohesiveness of the cheeses decreased with decreasing fat content. Texture attributes were influenced by the nature of the protein matrix that resulted due to fat removal.     

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.     

Effect of calcium on microstructure and meltability of part skim mozzarella cheese

The role of calcium in the microstructure of part skim Mozzarella cheese was evaluated using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Part skim Mozzarella cheeses with 4 calcium levels (control 0.65%, T1 0.48%, T2, 0.42%, and T3 0.35%) were manufactured and stored at 4 degrees C. Microstructure and meltability of cheeses were studied on d 1 and 30. The micrographs were analyzed for numbers, area, perimeter, roundness, and size of the fat particles. Reduced calcium cheeses had greater meltability and more hydrated protein matrix with greater number of fat particles (control=125, T1=193, T2=184, and T3=215 with SEM and control = 86, T1=87, T2= 125, and T3= 140 with CLSM). Further, area and perimeter of these fat particles were also greater in reduced calcium cheeses. Area, perimeter, and size of fat particles increased and their roundness decreased upon storage of 30 d. Decrease in free serum in the protein matrix of all cheeses upon refrigerated storage was evident from the CLSM. Hydrated protein network and better emulsified fat in low calcium cheeses might have improved melt properties of Mozzarella cheese.     

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.     

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.     

稻米油对涂抹再制干酪微观结构的影响

研究稻米油替代乳脂肪对涂抹再制干酪微观结构的影响。以切达干酪为原料,添加不同比例稻米油制备涂抹再制干酪,测定不同稻米油比例样品的微观结构和脂肪酸含量。结果表明,稻米油替代乳脂肪可以增加再制干酪产品长链脂肪酸,减少其短链脂肪酸、中链脂肪酸比例。稻米油替代对涂抹再制干酪的脂肪酸饱和度和链长的影响,导致再制干酪体系中脂肪球大小和分布的差异。对照组脂肪球小而分布均匀,植物油替代比例增加导致更大的脂肪球,通过微观结构观察,稻米油替代比例增大至50%时,开始出现较大直径且分布不均匀的脂肪球。因此,稻米油替代比例应控制在50%以下较为适宜。     

不同加工方法对快速成熟切达干酪流变和微观结构的影响

通过添加成熟干酪、成熟干酪与微胶囊酶共用和微胶囊复合酶单作用三种促熟方法制备切达干酪样2、样3和样4,非促熟对照为样1,利用流变仪、扫描电镜分析促熟技术对干酪质地的影响。结果表明,随扫描频率增加,四种样品的复数粘度(η*)极显著降低,其G′值和G″值极显著增加(P0.01);相同扫描频率时,四种样品的复数粘度值:样1样3样2样4。所有样品的G′值和G″值都随着温度的升高而显著降低,tanδ值先增加后减小,说明动态扫描时温度变化对快速成熟干酪G′值和G″影响极显著(P0.01)。样1、样2、样3和样4的转变温度分别为37.5℃、32.5℃、35℃和32.5℃。SEM测到样品的结构中"机械孔洞"数量和大小明显不同,对照样1和样3中机械孔洞数量多且较大,样2次之,样4几乎没有机械孔洞,说明样4的促熟后的质地相对最好。     

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.     

Microstructure and rheology of yogurt made with cultures differing only in their ability to produce exopolysaccharides

Yogurt was made using an exopolysaccharide-producing strain of Streptococcus thermophilus and its genetic variant that only differed from the mother strain in its inability to produce exopolysaccharides. The microstructure was investigated using confocal scanning laser microscopy, allowing observation of fully hydrated yogurt and the distribution of exopolysaccharide within the protein network. Yogurt made with the exopolysaccharide-producing culture exhibited increased consistency coefficients, but lower flow behavior index, yield stress, viscoelastic moduli and phase angle values than did yogurt made with the culture unable to produce exopolysaccharide. The exopolysaccharides, when present, were found in pores in the gel network separate from the aggregated protein. These effects could be explained by the incompatibility of the exopolysaccharides with the protein aggregates in the milk. Stirring affected the yogurt made with exopolysaccharide differently from yogurt without exopolysaccharide, as it did not exhibit immediate syneresis, although the structural breakdown was increased. The shear-induced microstructure in a yogurt made with exopolysaccharide-producing culture was shown to consist of compartmentalized protein aggregates between channels containing exopolysaccharide, hindering syneresis as well as the buildup of structure after stirring.     

不同烟草品种花粉粒形态的激光共聚焦扫描显微镜观察

对野生烟、烤烟、晒烟花粉进行了激光共聚焦扫描显微镜观察,发现不同品种烟草花粉的形态、大小存在明显的差异,可以做为烟草分类、进化研究的重要依据。      

Determining the gelation temperature of β-lactoglobulin using in situ microscopic imaging

Evolution of microstructure during heat-induced gelation of β-lactoglobulin (β-LG) was investigated in situ using confocal laser scanning microscopy at various gel-preparation conditions: pH = 2, 5, and 7; protein content = 5, 10, and 15%; and salt (NaCl) content = 0, 0.1, and 0.3 M. The number and area of evolving β-LG clusters were observed as a function of time and temperature and the data were fitted to a log-normal model and sigmoid model, respectively. The gelation temperature (T_gel) of the β-LG system was determined from both the number (T_gel/N) and total area (T_gel/A) of β-LG clusters versus temperature data. The range of T_gel/N and T_gel/A values for all the cases was 68 to 87°C. The effect of pH was the most dominant on T_gel/N and T_gel/A, whereas the effects of β-LG and salt contents were also statistically significant. Therefore, the combined effect of protein concentration, pH, and salt content is critical to determine the overall gel microstructure and T_gel. The T_gel/N and T_gel/A generally agreed well with T_gel determined by dynamic rheometry (T_gel/R). The correlations between T_gel/N and T_gel/A versus T_gel/R were 0.85 and 0.72, respectively. In addition, T_gel/N and T_gel/A values compared well with T_gel/R values reported in the literature. Based on these results, T_gel/N determined via in situ microscopy appears to be a fairly good representative of the traditionally measured gelation temperature, T_gel/R.     

Microstructure of fat globules in whole milk after thermosonication treatment

The structure of fat globules in whole milk was studied after heat and thermosonication treatments to observe what happens during these processes at the microscopic level using scanning electron microscopy. Raw whole milk was thermosonicated in an ultrasonic processor-Hielscher UP400S (400 W, 24 kHz, 120 microm amplitude), using a 22-mm probe at 63 degrees C for 30 min. Heat treatment involved heating the milk at 63 degrees C for 30 min. Color and fat content were measured to correlate the images with analytical measurements. The results showed that the surface of the fat globule was completely roughened after thermosonication. Ultrasound waves were responsible for disintegrating the milk fat globule membrane (MFGM) by releasing the triacylglycerols. Furthermore, the overall structure of milk after sonication showed smaller fat globules (smaller than 1 microm) and a granular surface. This was due to the interaction between the disrupted MFGM and some casein micelles. Minor changes in the aspect of the globules between thermal and raw milks were detected. Color measurements showed higher L* values for sonicated samples. Sonicated milk was whiter (92.37 +/- 0.20) and generally showed a better degree of luminosity and homogenization compared to thermal treated milk (88.25 +/- 0.67) and raw milk (87.82 +/- 0.18). Fat content analysis yielded a higher value after sonication (4.24%) compared to untreated raw milk (4.04%) because fat extraction is more efficient after sonication. The advantages of thermosonicated milk are that it can be pasteurized and homogenized in just 1 step, it can be produced with important cost savings, and it has better characteristics, making thermosonication a potential processing method for milk and most other dairy products.     

多糖分子质量对大豆蛋白聚集体/葡聚糖混合体系微观结构的影响

采用共聚焦激光扫描显微镜观察了室温下、pH 7.0时不同尺寸大小的大豆蛋白热聚集体和不同分子质量的葡聚糖混合体系的微观结构,并以天然大豆蛋白和葡聚糖混合体系的微观结构作对照。结果表明:葡聚糖分子链的排空相互作用使得蛋白质聚集体间产生了有效而不均匀的交联;蛋白质聚集体的尺寸增加和/或葡聚糖分子质量的增加促进了蛋白质富集区域的交联。对其共聚焦激光扫描图像进行灰度水平变化方差分析和灰度直方图分析表明,不同混合物间微观结构上具有显著性差异。     

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。