Héctor Eduardo Martínez-Flores

Effect of incorporating prebiotics in coating materials for the microencapsulation of Sacharomyces boulardii

The objective of this study was to microencapsulate Saccharomyces boulardii using the emulsion technique. To microencapsulate the yeast, alginate sodium blended with inulin and mucilage from Opuntiaficus-indica was used as a coating material. The textural properties of the gels formed by the encapsulating materials and the in vitro viability of the yeast strain in the simulated conditions were studied. Textural profile analyses of the gels revealed differences (p < 0.05) in hardness because alginate produced stronger gels, whereas the incorporation of other hydrocolloids with alginate decreased gel strength and resulted in a more uniform, cohesive gel matrix. When alginate was blended with mucilage and inulin, encapsulated yeast presented higher counts and more viable cells, as compared to free yeast following 30 days of storage at 4°C. Encapsulated and free yeast had 76.1% and 63.3%, respectively, of cell viability after 35 days of storage.

Caracterización fisicoquímica, funcional y química de harinas nixtamalizadas de maíz obtenidas por calentamiento óhmico y proceso tradicional

Se caracterizaron harinas de maíz nixtamalizadas (HMN) obtenidas por calentamiento óhmico (HCO), proceso tradicional (HPT) y harina comercial (HC) en su composición química, capacidad e índice de absorción de agua (CAA, IAA), índice de solubilidad (ISA), viscosidad, rendimiento, humedad y textura de las masas y tortillas. Las HCO presentaron diferentes grados de gelatinización de acuerdo a los resultados de IAA, CAA, ISA y viscosidad. Las masas y tortillas obtenidas de las HCO, presentaron mayor humedad (58,25 a 53,62 g/100 g) que la HPT (52,67 g/100 g), resultando en un mayor rendimiento de tortilla, con buena textura. El contenido de proteína de las HCO fue de 8,51 a 8,23%, superior a la HPT (7,95%). El contenido de fibra fue mayor en las HCO comparado con las HPT y HC (P < 0,05). El calentamiento óhmico es una alternativa en la elaboración deHMN.

Nixtamalization Process Affects Resistant Starch Formation and Glycemic Index of Tamales

Tamales were prepared with 3 nixtamalization processes (traditional, ecological, and classic) and evaluated for chemical composition, starch properties, and glycemic index. Resistant starch (RS) in tamales increased 1.6 to 3.7 times compared to raw maize. This increment was due to the starch retrogradation (RS3) and amylose-lipid complexes (RS5) formation. Tamales elaborated with classic and ecological nixtamalization processes exhibited the highest total, soluble and insoluble dietary fiber content, and the highest RS content and lower in vivo glycemic index compared to tamales elaborated with traditional nixtamalization process. Thermal properties of tamales showed 3 endotherms: amylopectin retrogradation (42.7 to 66.6 °C), melting of amylose lipid complex type I (78.8 to 105.4), and melting of amylose-lipid complex type II (110.7 to 129.7). Raw maize exhibited X-ray diffraction pattern type A, after nixtamalization and cooking of tamales it changed to V-type polymorph structure, due to amylose-lipid complexes formation. Tamales from ecological nixtamalization processes could represent potential health benefits associated with the reduction on blood glucose response after consumption.

Electrochemical Study and Characterization of an Amperometric Biosensor Based on the Immobilization of Laccase in a Nanostructure of TiO2 Synthesized by the Sol-Gel Method

Laccase amperometric biosensors were developed to detect the catechol compound. The laccase enzyme (LAC) immobilization was performed on nanostructures of (a) titania (TiO2); (b) titania/Nafion (TiO2/NAF) (both immobilized by the sol-gel method) and a third nanostructure, which consisted of a single biosensor composite of Nafion and laccase enzyme denoted as NAF/LAC. The Nafion was deposited on a graphite electrode and used to avoid “cracking” on the matrix. The TiO2 particle size was an average of 66 nm. FTIR spectroscopy vibration modes of different composites were determined. The electrochemical behavior of the biosensor was studied using electrochemical spectroscopy (EIS) and cyclic voltammetry (CV). The biosensor based on TiO2/NAF/LAC presented the best electro-chemical properties with regard to sensitivity, stability and detection limit after a period of 22 days.

Chemical composition and physicochemical properties of shiitake mushroom and high fiber products Composición química y propiedades físico-químicas del hongo shiitake y de productos con alto contenido de fibra

Increasing dietary fiber (DF) intake may help to decrease risk of chronic diseases such as diabetes, cardiovascular disease and colon cancer. The objective of this work was to study and compare the chemical composition and physicochemical properties of some products used as DF sources. The DF source products evaluated were Metamucil, Kania, Tarasca, Nopalinaza, Xotzil and dried shiitake mushroom (Lentinus edodes). Metamucil showed the highest content of DF (52.72%), followed by Kania (50.57%) and DS (49.09%). Also, Metamucil, Kania and DS showed the highest water absorption values 15.9, 8.5, and 5.7 g water/g sample respectively, while DS showed the highest oil absorption capacity (3.1 g oil/g sample). Best values delaying diffusion of glucose were obtained in Metamucil, Nopalinaza, Kania and DS samples. Multiple correlation analysis indicated that soluble fiber contents positively correlated with water absorption capacity, viscosity and minor particle size.

Effect of thermal-alkaline processing conditions on the quality level of corn oil

The objective of this study was to determine the best combination of process variables to produce nixtamalized corn flour (NCF) with the lowest level of lipid deterioration. The nixtamalization conditions used were calcium concentrations from 0.4 to 2.56 g Ca(OH)2/L in water and steeping times of 6.34 to 17.65 h. The cooking time was 40 min at 94°C. The cooked and steeped grains were washed and milled to obtain masa which was then dehydrated and milled until the NCF was obtained. Oil was extracted by means of hexane from each sample of processed corn. The level of least oil deterioration of nixtamalized samples was based on the following response variables: saponification, acidity, peroxides, iodine values and extinction coefficient measured at 270 nm (K270). The best nixtamalization conditions for obtaining the highest oil stability were found at Ca(OH)2 lower than 0.75% and steeping times less than 12 h.

Extruded snacks from whole wheat supplemented with textured soy flour: Effect on instrumental and sensory textural characteristics

The quality of extruded snacks can be affected not only by processing conditions, but also by some factors like the concentration and type of ingredients incorporated in their formulation and the working conditions used. Although the process conditions have been established with measurable textural properties, sensory qualities have not been correlated with these responses in expanded extruded snacks made with added functional ingredients. Therefore, in this study the effect of adding textured soy flour (TSF) and whole wheat flour (WWF) to refined wheat flour in the production of extruded snacks and expanded with hot air was evaluated. A response surface design using two levels with five central points was applied to obtain the best combinations of functional ingredients added, holding the parameters of the extrusion process and moisture of treatments. Some texture characteristics and sensory analysis were used as response variables, such as, hardness, fracturability, toughness, crispness, granularity, and chewiness. Likewise, the rate of expansion was evaluated. The results showed that the level of substitution of WWF, especially levels of 15%, had a significant effect on the hardness perceived by the panelist during sensory evaluation. The TSF at concentrations of ≥15%, favored the fracturability and crispness of the samples. It was found that the best expansion index was with the combination of 5% TSF and 15% WWF. Although a correlation between instrumental and sensory tests carried out on the extruded snacks expanded was not found. PRACTICAL APPLICATIONS The physical characteristics of the extruded snacks such as expansion, hardness, and density are important parameters in terms of consumer acceptability of the final product as well as their functional properties. In other words, the appearance and texture are two of the most important attributes that can be seen in snack foods. In particular, the texture can be measured by intrinsic tests: objective (instrumental) and subjective (sensory). That is because the instrumental analysis provides parameters such as firmness, brittleness, consistency, chewiness, among others, when subjected to different stress, strain, and strain rates at the snacks. Similarly, sensory analysis, allows us to see features that include mechanical attributes (concerning the reaction to the applied force), geometric attributes (concerning the shape, size, and orientation of the particles within the food), and attributes related to the perception of moisture or fat content.

Antioxidant Properties of Polyphenolic Extracts from Quercus Laurina, Quercus Crassifolia, and Quercus Scytophylla Bark

The objective of this work was to determine the concentration of total phenols, total flavonoids, hydroxycinnamic acids, and proanthocyanidins present in crude extracts of Quercus laurina, Q. crassifolia, and Q. scytophylla bark. They were extracted by ethanol (90%) maceration and hot water. The antioxidant capacity was determined by the ability to capture OH•, O2•−, ROO•, H2O2, NO•, and HClO. The hot water crude extract of Q. crassifolia was chosen to be concentrated and purified due to its higher extraction yield (20.04%), concentration of phenol compounds (747 mg gallic acid equivalent (GAE)/g, 25.4 mg quercetin equivalent (QE)/g, 235 mg ChAE/g, 25.7 mg chlorogenic acid equivalents (ChAE)/g), and antioxidant capacity (expressed as half maximal effective concentration (EC50, µg/mL): OH• = 918, O2•− = 80.5, ROO• = 577, H2O2 = 597, NO• ≥ 4000, HClO = 740). In a second stage, Q. crassifolia extracted with hot water was treated with ethyl acetate, concentrating the phenol compounds (860 mg GAE/g, 43.6 mg QE/g, 362 ChAE/g, 9.4 cyanidin chloride equivalents (CChE)/g) and improving the scavenging capacity (OH• = 467, O2•− = 58.1, ROO• = 716, H2O2 = 22.0, NO• ≥ 4000, HClO = 108). Q. crassifolia had the highest polyphenolic concentration and the better capacity for scavenging reactive species, being a favorable candidate to be considered in the development of new products.

Quantification of Phenolic Compounds and In Vitro Radical Scavenging Abilities with Leaf Extracts from Two Varieties of Psidium guajava L.

Guava leaf (Psidium guajava L.) extracts are used in both traditional medicine and the pharmaceutical industry. The antioxidant compounds in P. guajava leaves can have positive effects including anti-inflammatory, anti-hyperglycemic, hepatoprotective, analgesic, anti-cancer effects, as well as protecting against cardiovascular diseases. In the present study, phenolic compounds and in vitro antioxidant capacity were measured in extracts obtained with polar and non-polar solvents from leaves of two varieties of guava, Calvillo Siglo XXI and Hidrozac. The quantity of total phenolics and total flavonoids were expressed as equivalents of gallic acid and quercetin, respectively. Hydroxyl radical, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and Oxygen Radical Absorbance Capacity using fluorescein (ORAC-FL) in vitro tests were used to assess the radical scavenging abilities of the extracts. The total phenolics were higher in the aqueous fraction of the variety Calvillo Siglo XXI, while in the Hidrozac variety total phenolics were higher in the acetone and chloroform fractions. Total flavonoids were higher in all fractions in the variety Calvillo Siglo XXI. Total phenolics showed a highly positive correlation for ORAC-FL, and a moderately positive correlation with hydroxyl radicals. Finally, total flavonoids showed a slightly positive correlation for ORAC-FL and hydroxyl radicals. Both varieties of guava leaf extract showed excellent antioxidant properties.

Optical temperature behavior of a starch-water mixture

An optical set-up was developed to measure transmitted and scattered light in real time using a photodiode array as a detector and tested during starch heating. Statistical parameters calculated were Partial Integrated Scattering (PIS) and variance. Understanding behavior of starch under heat treatment in the presence of water is very important in food industry. The structure of heated starch granule changes depending on different factors like pH, solvent type and amount, enzime presence, amylose/amylopectin relation, etc., such changes has been attempted by using several techniques. In this work, solutions in distilled water of amylopectin, were evaluated. Calcium hydroxide solution was also tested and mixed with previous amylopectin samples to evaluate any interaction in a two-phase system. A close relationship was found between the observed optical signals with literature reported structure changes in starch, demonstrating that the system developed has potential to be used in a real industrial process for monitoring and control.