Georgina Calderón-Domínguez

Evaluation of the mechanical damage on wheat starch granules by SEM, ESEM, AFM and texture image analysis.

The effect of mechanical damage on wheat starch granules surface, at a microstructural level, was investigated by scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), atomic force microscopy (AFM), and image textural analysis. The SEM and ESEM images of the native sample showed that the starch granules had smooth, flat surfaces and smooth edges. The samples with higher damaged starch content exhibited granular distortion, irregularity and less uniformity. The fractal dimension of contour parameter increased with mechanical damage, indicating that the surface irregularities quantitatively increased due to the damage. The surfaces of damaged granules showed depressions of different shapes and sizes. The roughness parameters and fractal dimension of the surface increased as a result of the mechanical damage. The surface of damaged granules showed higher entropy and lower homogeneity values when damaged starch increased. The results indicated that the mechanical process caused structural modifications at nano level.

Fractal and Image Analysis of Mexican Sweet Bread Bubble Distribution: Influence of Fermentation and Mixing Time

Abstract The effects of mixing and fermentation on the crumb characteristics of Mexican yeast sweet bread were analyzed by means of image and fractal analysis. Extensigraphic dough resistance to extension ( R max ) and bread volume were also evaluated. Dough images were captured using Scanning Electron Microscopy (SEM), while bread images were obtained by flatbed-scanning cross sections of the loaf. Image analysis was carried out using ImageJ software. Crumb cell size was mainly affected by fermentation time. Mixing and fermentation increased maximum resistance to extension, provided dough was not collapsed. SEM images showed that dough changed from a compact to an open structure with mixing. Using image analysis, it was observed that changes in fractal dimension of cells could be related to dough rheological properties. Cell distribution of materials may be produced by coalescence, which is associated with the fractal structures formed.

Effect of Soybean 7S Protein Fractions, Obtained from Germinated and Nongerminated Seeds, on Dough Rheological Properties and Bread Quality

Germinated soybean flour has been proposed for use in bread making as a product to improve bread quality when small amounts are added to wheat flour. However, it is not clear which soybean components promote this action, and how these components may influence bread quality. The aim of this work was to evaluate the effect of the addition of soybean 7S protein fraction obtained from germinated and nongerminated seeds in dough rheological properties (farinographic and extensographic) and bread quality, including loaf volume, texture (firmness, compression force, resilience), colour (L*, a*, b*), crumb grain structure (cell density, mean cell area, shape factor), and consumer acceptance (sensory analysis). Results showed that this protein fraction just slightly affects bread quality, since no significant changes (P > 0.05) on bread volume and texture were obtained. Only crust and crumb colour were affected in a small amount, and a coarser crumb structure was also observed when adding 7S protein obtained from germinated soybean at its highest concentration. As the proportion of protein increased in the flour, both kinds of 7S fraction (germinated and nongerminated) were related to the increment in water absorption, as well as to the increment in extensographic maximum resistance to extension, specifically when adding 7S protein obtained from nongerminated soybean seeds. These results showed that the 7S soybean protein, as obtained in this work, is not related to the reported loaf bread quality improving effect of this legume when it is added in small quantities.

Characterization of Functionalized Multiwalled Carbon Nanotubes for Use in an Enzymatic Sensor

Carbon nanotubes (CNT) have proven to be materials with great potential for the construction of biosensors. Development of fast, simple, and low cost biosensors to follow reactions in bioprocesses, or to detect food contaminants such as toxins, chemical compounds, and microorganisms, is presently an important research topic. This report includes microscopy and spectroscopy to characterize raw and chemically modified multiwall carbon nanotubes (MWCNTs) synthesized by chemical vapor deposition with the intention of using them as the active transducer in bioprocessing sensors. MWCNT were simultaneously purified and functionalized by an acid mixture involving HNO3-H2SO4 and amyloglucosidase attached onto the chemically modified MWCNT surface. A 49.0% decrease in its enzymatic activity was observed. Raw, purified, and enzyme-modified MWCNTs were analyzed by scanning and transmission electron microscopy and Raman and X-ray photoelectron spectroscopy. These studies confirmed purification and functionalization of the CNTs. Finally, cyclic voltammetry electrochemistry was used for electrical characterization of CNTs, which showed promising results that can be useful for construction of electrochemical biosensors applied to biological areas.

Determination of Trichinella spiralis in pig muscles using Mid-Fourier Transform Infrared Spectroscopy (MID-FTIR) with Attenuated Total Reflectance (ATR) and Soft Independent Modeling of Class Analogy (SIMCA).

The aim of this work was to study the feasibility of detection of Trichinella spiralis in swine meat using Middle Infrared Spectroscopy Fourier Transform with Attenuated Total Reflectance (ATR) and Soft Independent Modeling of Class Analogy (MID-FTIR-ATR-SIMCA). Five male Pigs were orally infected at different larvae concentrations (13,000, 6500, 3500, 1625, 812 larvae/pig) and after 24 weeks the animals were euthanized. Five types of muscles were studied (leg, loin, rib, masseter, and diaphragm). Results showed that MID-FTIR-ATR-SIMCA was useful to determine the presence of T. spiralis in the samples, as the interclass distance between infected and non infected muscles varied from 13.5 to 36.8. This technique was also useful to discriminate among pig muscles, where masseter showed the largest interclass distance, while rib presented the smallest one. In all cases the recognition and rejection rates were 100%, which means that the methodology is capable of accurately separating T. spiralis infected from non infected swine meat.

Evaluation of agave fiber delignification by means of microscopy techniques and image analysis.

Recently, the use of different types of natural fibers to produce paper and textiles from agave plants has been proposed. Agave atrovirens can be a good source of cellulose and lignin; nevertheless, the microstructural changes that happen during delignification have scarcely been studied. The aim of this work was to study the microstructural changes that occur during the delignification of agave fibers by means of microscopy techniques and image analysis. The fibers of A. atrovirens were obtained from leaves using convective drying, milling, and sieving. Fibers were processed using the Acetosolv pulping method at different concentrations of acetic acid; increasing acid concentration promoted higher levels of delignification, structural damage, and the breakdown of fiber clumps. Delignification followed by spectrometric analysis and microstructural studies were carried out by light, confocal laser scanning and scanning electron microscopy and showed that the delignification process follows three stages: initial, bulk, and residual. Microscopy techniques and image analysis were efficient tools for microstructural characterization during delignification of agave fibers, allowing quantitative evaluation of the process and the development of linear prediction models. The data obtained integrated numerical and microstructural information that could be valuable for the study of pulping of lignocellulosic materials.

Physical, Structural, Barrier, and Antifungal Characterization of Chitosan–Zein Edible Films with Added Essential Oils

Edible films (EFs) have gained great interest due to their ability to keep foods safe, maintaining their physical and organoleptic properties for a longer time. The aim of this work was to develop EFs based on a chitosan–zein mixture with three different essential oils (EOs) added: anise, orange, and cinnamon, and to characterize them to establish the relationship between their structural and physical properties. The addition of an EO into an EF significantly affected (p < 0.05) the a* (redness/greenness) and b* (yellowness/blueness) values of the film surface. The EFs presented a refractive index between 1.35 and 1.55, and thus are classified as transparent. The physical properties of EFs with an added EO were improved, and films that incorporated the anise EO showed significantly lower water vapor permeability (1.2 ± 0.1 g mm h−1 m−2 kPa−1) and high hardness (104.3 ± 3.22 MPa). EFs with an added EO were able to inhibit the growth of Penicillium sp. and Rhizopus sp. to a larger extent than without an EO. Films’ structural changes were the result of chemical interactions among amino acid side chains from zein, glucosamine from chitosan, and cinnamaldehyde, anethole, or limonene from the EOs as detected by a Raman analysis. The incorporation of an EO in the EFs’ formulation could represent an alternative use as coatings to enhance the shelf life of food products.

Germinated Soybean Products as Nutraceutical Compounds in Breadmaking

Epidemiological studies have shown a positive relation between diet and good health. Seeds, like soybeans, considered in the past as detrimental to health due to some anti-nutritional factors, are studied now with a new perspective. Since the last decade, many studies have been published relating some soy components such as isoflavones, saponines, trypsin inhibitors, used for the prevention of specific illnesses. The same effect has been attributed to some proteins. Soy proteins present higher nutritional values as compared to cereals and other legumes, but they do not produce as good results as casein when subject to biological analysis. Germination has been proposed to increase this relation, as well as to promote the generation of some bioactive peptides, that could be associated to a decrease of some malign tumour cells. These nutraceutical properties have increased the interest in adding soybean proteins to food, but the effect that these materials have in the product establishes the level of addition. Bread has been one of the products where this kind of proteins has been tested. This review deals with the different kinds of soy compounds added to bread products and their effect on technological properties, looking for obtaining of a nutraceutical product.

Structural and Physicochemical Characterization of Spirulina (Arthrospira maxima) Nanoparticles by High-Resolution Electron Microscopic Techniques.

The objective of this work was to obtain Spirulina (Arthrospira maxima) nanoparticles (SNPs) by using high-impact mechanical milling and to characterize them by electron microscopy and spectroscopy techniques. The milling products were analyzed after various processing times (1-4 h), and particle size distribution and number mean size (NMS) were determined by analysis of high-resolution scanning electron microscopic images. The smallest particles are synthesized after 3 h of milling, had an NMS of 55.6±3.6 nm, with 95% of the particles being smaller than 100 nm. High-resolution transmission electron microscopy showed lattice spacing of ~0.27±0.015 nm for SNPs. The corresponding chemical composition was obtained by energy-dispersive X-ray spectroscopy, and showed the presence of Ca, Fe, K, Mg, Na, and Zn. The powder flow properties showed that the powder density was higher when the average nanoparticle size is smaller. They showed free flowability and an increase in their specific surface area (6.89±0.23 m2/g) up to 12-14 times larger than the original material (0.45±0.02 m2/g). Fourier transform infrared spectroscopy suggested that chemical damage related to the milling is not significant.

Nanobiosensors in Food Science and Technology

Nanotechnology has already been applied in several fields, up to now, most of the research on nanotechnology focused on electronics such as communication, energy production, and pharmaceutical and the food industry. The knowledge gained from these sectors could be adapted for the improvement of food products, such as for applications in food safety and quality (e.g., detecting pesticides and microorganism identification), encapsulation, improving the efficiency of delivery of nutraceutical and bioactive compounds, and packing systems and food storage. The nanoscale devices are often manufactured with the view to imitate the nanodevices found in nature; one way to get these results is by means of the biosensors to detect, among others, proteins, DNA, enzymes, cells, membranes, and other natural biomolecules used as bioreceptors and selecting the right transduction method (electrochemical, mechanical, or optical) in order to get more sensitive, specific, and real-time results. This chapter provides an introduction to the nanosensor field including specific consideration of three main application areas (food, environmental, and pharmaceutical); it also describes the typical biosensor assay format used and is subsequently structured according to the biorecognition elements used (i.e., enzymes, cellular structures/cells, antibody/antigen, nucleic acids/DNA, bacteriophages). In addition, information about lab on a chip based on microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) technology is also provided.