Application of epifluorescence light microscopy (EFLM) to study the microstructure of wheat dough: a comparison with confocal scanning laser microscopy (CSLM) technique

Microscopic Imaging to Visualize the Distribution of Dietary Nucleic Acids in Food Products of Various Origins

Dietary nucleic acids (dietNAs) are being increasingly recognized as important food components with nutritional value. However, the precise dietary recommendations for dietNAs are limited, because established methods for determining the quantity and nutritional role of dietNAs are still lacking. One of the tools to narrow this gap could be microscopic imaging, as a convenient approach to visualize the abundance and distribution of dietNAs in food products. With the aid of appropriate bioinformatic elaboration, such images may in future enable the direct semiquantitative estimation of these macromolecules in food products. In the presented study, two methods of preparing microscopic sections and staining them with DNA-specific fluorochromes were used for microscopic imaging of dietNAs in food products of plant and animal origin. Procedures for preparing formalin-fixed paraffin-embedded sections and cryosections were compared in terms of their usefulness for routine food analysis. Both methods turned out equally suitable for visualizing dietNA distribution in animal and plant products. However, the use of cryosections allowed a significantly shorter analysis time and reduced the consumption of organic solvents. Both of these advantages make the cryosection method preferable while establishing a dedicated methodology for routine assessment of dietNAs in the food industry.

Multiphoton microscopy is a nondestructive label-free approach to investigate the 3D structure of gas cell walls in bread dough

During the different steps of bread-making, changes in the microstructure of the dough, particularly in the gas cell walls (GCW), have a major influence on the final bread crumb texture. Investigation of the spatial conformation of GCWs is still a challenge because it requires both high resolutions and 3D depth imaging. The originality of the present work lies in the use of label-free non-destructive multiphoton microscopy (NLOM) to image the 3D structure of GCWs, shedding light on their behavior and organization in wheat bread dough. We demonstrated that second and third harmonic generation (SHG, THG) allow imaging, respectively, of starch granules and interfaces in bread dough, while the gluten matrix was detected via two-photon excitation fluorescence (TPEF). Last, a distinction between the gluten network and starch granules was achieved using gluten endogenous fluorescence (EF) imaging, while the position, size, and 3D orientation of starch granules in GCWs were determined from harmonic imaging, made possible by the acquisition of backward and forward SHG with linear polarization. These innovative experiments highlight the strengths of NLOM for a label-free characterization of bread dough microstructure for the first time, in order to understand the role of starch granules in dough stabilization.

Dough Rheological Behavior and Bread Quality as Affected by Addition of Soybean Flour in a Germinated Form

This study analyzes the possibility of using soybeans as an addition to the main ingredients used to make bread, with the aim of improving its quality characteristics. To maximize the nutritional profile of soybeans they were subjected to the germination and lyophilization process before being used in bread making. The addition levels of 5%, 10%, 15%, and 20% germinated soybean flour (GSF) on dough rheology and bread quality were used. From the rheology point of view, the GSF addition had the effect of decreasing the values of the creep and recovery parameters: J_Co, J_Cm, μ_Co, J_max, J_Ro, J_Rm, and J_r. At the same time, the rheological parameters λ_C and λ_R increased. The GSF addition did not affect dough homogeneity as may be seen from EFLM analysis. Regarding the quality of the bread, it may be concluded that a maximum of 15% GSF addition in wheat flour had a desirable effect on loaf volume, porosity, elasticity, and sensory properties of the bread. The bread samples with GSF additions showed a higher brightness and a less pronounced red and yellow tint. When the percentage of GSF in wheat flour increased, the value of the firmness parameter increased and the value of the gumminess, cohesiveness, and resilience parameters decreased. The addition of GSF had a desirable influence on the crumb structure of the bread samples. Thus, taking into account the results of the determinations outlined above, it can be stated that GSF addition in wheat flour leads to bread samples with good quality characteristics.

Effects of Germinated Lentil Flour on Dough Rheological Behavior and Bread Quality

The present study analyzed the effects of germinated lentil flour (LGF) addition at different levels in wheat flour (2.5%, 5%, 7.5%, and 10%), on dough rheological behavior, dough microstructure, and bread quality. Creep-recovery tests showed that the dough samples with high levels of LGF addition presented a higher resistance to flow deformability of the dough. Dough microstructure as analyzed using EFLM showed an increase in the protein area (red color) and a decrease in the starch (green color) amount with the increased level of LGF addition in the wheat flour. It was found that the LGF addition led to the improvement of the porosity, specific volume, and elasticity of the bread samples. The breads with LGF addition were darker and had a slightly reddish and yellowish tint. The bread textural parameters highlighted significant (p < 0.05) higher values for firmness and gumminess and significant (p < 0.05) lower ones for cohesiveness and resilience for the bread with LGF addition when compared with the control. The bread samples with a 2.5% and 5% addition had a more dense structure of the crumb pores. Regarding sensory evaluation, the bread samples with LGF addition in the wheat flour were well appreciated by the consumers. The addition also was desirable due to the fact that it supplemented bread with a greater amount of protein and minerals due to the composition of lentil grains. Therefore, LGF could be successfully used as an ingredient for bread making in order to obtain bread with an improved quality.

Dough Rheological Properties, Microstructure and Bread Quality of Wheat-Germinated Bean Composite Flour

Germinated bean flour (GBF) was obtained and incorporated in different levels (5%, 10%, 15%, 20% and 25%) into dough and bread made from refined wheat flour. The incorporation of GBF into wheat flour led to a decrease of the water absorption value, dough consistency, baking strength, extensibility and improved tolerance for mixing, total gas production and α-amylase activity. Tan δ increased in a frequency-dependent manner for the samples with a GBF addition, whereas the G’ and G” decreased with the increased value of the temperature. According to the microscopic structures of the dough samples, a decrease of the starch area may be clearly seen for the samples with high levels of GBF addition in wheat flour. The bread evaluation showed that the specific volume, porosity and elasticity increased, whereas the firmness, gumminess and chewiness decreased up to a level of 15% GBF addition in wheat flour. The color parameters L*, a* and b* of the bread samples indicated a darkening effect of GBF on the crumb and crust. From the sensory point of view, the bread up to a 15% GBF addition was well-appreciated by the panelists. According to the data obtained, GBF could be recommended for use as an improver, especially up to a level of 15% addition in the bread-making industry.

Novel nano-vehicle for delivery and efficiency of anticancer auraptene against colon cancer cells

The aim of this study is to devise, prepare and characterize nano encapsulated auraptene (AUR) and evaluate cytotoxic and apoptotic effects on HT-29 colon cancer cells. Herein, AUR nano formulations were prepared by triblock (PCL-PEG-PCL) and pentablock (PLA-PCL-PEG-PCL-PLA) biodegradable copolymers in order to increase AUR bioavailability as an anticancer agent. The preparation of nano particles (NPs) was done with rotor stator homogenization (RSH) and Ultrasonic homogenization (USH) methods. The physicochemical characteristics of prepared nanoparticles (NPs) were studied using HNMR, FTIR, GPC, DLS and SEM techniques. The smaller hydrodynamic size (110 nm) and polydispersity index (PDI: 0.288) as well as higher cellular uptake (89%) were observed in PB NPs rather than TB NPs. The highest cytotoxic and apoptotic effects were observed in AUR loaded PB NPs compared to AUR loaded TB NPs and free AUR obtained by MTT assay, cell cycle arrest, Annexin V-FITC, DAPI staining and RT-PCR techniques. Real time PCR results indicated that Bax /Bcl2 expression ratio as an apoptosis predicting criterion, in free AUR, AUR loaded TB and AUR loaded PB have increased 6, 9 and 13 times, respectively (p value < 0.05). In conclusion, using biodegradable nano-vehicles for sustained delivery of natural anti-cancer compounds may open new perspectives for treatment of cancer patients.

Dough Rheological Behavior and Microstructure Characterization of Composite Dough with Wheat and Tomato Seed Flours

The rheological and microstructural aspects of the dough samples prepared from wheat flour and different levels of tomato seed flour (TSF) were investigated by rheology methods through the Mixolab device, dynamic rheology and epifluorescence light microscopy (EFLM). The Mixolab results indicated that replacing wheat flour with TSF increased dough development time, stability, and viscosity during the initial heating-cooling cycle and decreased alpha amylase activity. The dynamic rheological data showed that the storage modulus G’ and loss modulus G” increased with the level of TSF addition. Creep-recovery tests of the samples indicated that dough elastic recovery was in a high percentage after stress removal for all the samples in which TSF was incorporated in wheat flour. Using EFLM all the samples seemed homogeneous showing a compact dough matrix structure. The parameters measured with Mixolab during mixing were in agreement with the dynamic rheological data and in accordance with the EFLM structure images. These results are useful for bakery producers in order to develop new products in which tomato seed flour may be incorporated especially for wheat flours of a good quality for bread making and high wet gluten content. The addition of TSF may have a strength effect on the dough system and will increase the nutritional value of the bakery products.

Quantitative analysis of the phase volume of agarose-canola oil gels in comparison to blending law predictions using 3D imaging based on confocal laser scanning microscopy

Studying the phase behaviour of composite gels facilitates understanding of their structural and textural properties at low and intermediate levels of solids. In this work, the phase behaviour of a model system of agarose including various concentrations of canola oil was studied. This was pursued using a variety of techniques including SEM, FTIR, microDSC and dynamic oscillation in-shear. The structural studies recorded strong, continuous agarose networks supporting soft, discontinuous canola oil inclusions, with increasing levels of canola oil strengthening the composite system. A novel confocal laser scanning microscopy (CLSM) method for quantitative in situ examination of the oil phase volume was developed using three-dimensional (3D) imaging and image analysis software - FIJI and Imaris. Microscopic observations were assessed in relation to theoretical predictions from rheology-based blending-law analysis. Quantitative outcomes from the combined 3D imaging and image analysis are in close agreement with the volume predictions for the oil phase obtained from the isostrain blending law indicating the suitability of this approach in quantifying the phase behaviour of composite materials. The results of this work indicate that the developed microscopic method shows promise and could be used in the determination of phase volume in more complex and industrially relevant systems.

Definition of network types - Prediction of dough mechanical behaviour under shear by gluten microstructure

This study defines network types of wheat gluten to describe spatial arrangements of gluten networks in relation to dough mechanical behaviour. To achieve a high variety in gluten arrangements, ten specific and unspecific gluten-modifying agents in increasing concentrations were added to wheat dough. Gluten microstructure was visualized by confocal laser scanning microscopy and quantified by protein network analysis. Dough rheological behaviour was determined by both oscillatory and creep-recovery tests. Based on correlation matrices and principal component analysis, six different network types were identified and associated to their rheological characteristics: a cleaved (low viscous), rigid (highly viscous), spread (viscoelastic), strengthened (viscoelastic), particulate and dense (highly viscous) or particulate and loose (low viscous) network. Furthermore, rheological dough properties of specifically gluten-modified samples were predicted with five microstructural gluten attributes (lacunarity, branching rate, end-point rate, protein width, average protein length) and assigned properly by the obtained partial least square model with an accuracy up to 90% (e.g., R2Y = 0.84 for G*, 0.85 for tanδ, 0.90 for Jmax). As a result, rheological properties of wheat doughs were predicted from microstructural investigations. This novel, quantitative definition of the relation between structure and mechanical behaviour can be used for developments of new wheat products with targeted properties.

Use of response surface methodology to investigate the effects of brown and golden flaxseed on wheat flour dough microstructure and rheological properties

The aim of this study was to assess the effects of brown flaxseed and golden flaxseed on the water absorption and the rheological parameters of wheat flour. The rheological properties were evaluated by the Mixolab. The optimum parameters were identified for high quality flaxseed-wheat composite flour bread. Each predictor variable was tested at five levels. The microstructure of dough was assessed by epifluorescence light microscopy. The substitution of 4.81/100 g for brown flaxseed and 5.07/100 g for golden flaxseed was found optimal. At the optimum level of brown and golden flaxseed, the water absorption of 55.07/100 g, dough development time of 1.28 min and dough stability of 10.04 min was observed. In terms of protein quality the optimum values were 0.41 N m for C2 and 0.69 for C1-2, and in terms of starch characteristics they were 1.56 N m for C3, 1.14 for C3-2, 1.33 N m for C4, 0.20 for C3-4, 1.97 N m for C5 and 0.60 for C5-4.

Wheat dough microstructure: the relation between visual structure and mechanical behavior

The microstructure of food matrixes, and specifically that of wheat-flour dough, determines mechanical behavior. Consequently, the analysis of such microstructure is both necessary and useful for understanding the physico-chemical and mechanical alterations during the production of cereal-based products such as breads. Confocal laser scanning microscopy (CLSM) is an established tool for the investigation of these matrix properties due to its methodical advantages such as easy preparation and handling, and the high depth resolution due to the optical sectioning of probes. This review focuses on the microstructure of wheat-flour dough from a mechanical and visual point of view. It provides an overview of the dependencies between the visibly detectable microstructural elements achieved by CLSM and the physical determined rheological properties. Current findings in this field, especially on numerical microstructure features, are described and discussed, and possibilities for enhancing the analytical methodology are presented.

Structural and Nutritional Properties of Pasta from Triticum monococcum and Triticum durum Species. A Combined ¹H NMR, MRI, and Digestibility Study

The aim of the present study was to characterize the structure of two different types of pasta, namely Triticum turgidum ssp. durum (cv. Saragolla) and Triticum monococcum ssp. monococcum (cv. Monlis), under different processing conditions. MRI analysis and NMR spectroscopy (i.e., T1 and T2 NMR relaxation times and diffusion parameters) were conducted on pasta, and (1)H NMR spectroscopic analysis of the chemical compounds released by pasta samples during the cooking process was performed. In addition, starch digestibility (enzimatically determined) was also investigated. The NMR results indicated that Saragolla pasta has a more compact structure, ascribed to pasta network and in particular to different technological gluten properties, that mainly determine the lower ability of Monlis pasta in binding water. These results correlate well with the lower rate of starch hydrolysis measured for Monlis pasta compared to Saragolla when both are dried at high temperature.

The development of pistillate and perfect florets in Xeranthemum squarrosum (Asteraceae)

The formation of capitulum inflorescence with two different types of floret is an interesting issue in floral biology and evolution. Here we studied the inflorescence, floral ontogeny and development of the everlasting herb, Xeranthemum squarrosum, using epi-illumination microscopy. The small vegetative apex enlarged and produced involucral bracts with helical phyllotaxy, which subtended floret primordia in the innermost whorl. Initiation of floret primordia was followed by an acropetal sequence, except for pistillate peripheral florets. The origin of receptacular bracts was unusual, as they derived from the floral primordia rather than the receptacular surface. The order of whorl initiation in both disc and pistillate flowers included corolla, androecium and finally calyx, together with the gynoecium. The inception of sepals and stamens occurred in unidirectional order starting from the abaxial side, whereas petals incepted unidirectionally from the adaxial or abaxial side. Substantial differences were observed in flower structure and the development between pistillate and perfect florets. Pistillate florets presented a zygomorphic floral primordium, tetramerous corolla and androecium and two sepal lobes. In these florets, two sepal lobes and four stamen primordia stopped growing, and the ovary developed neither an ovule nor a typical stigma. The results suggest that peripheral pistillate florets in X. squarrosum, which has a bilabiate corolla, could be considered as an intermediate state between ancestral bilabiate florets and the derived ray florets.