Effect of Acid-Hydrolyzed Thermoplastic Starch on the Mechanical, Thermal and Morphological Properties of Polyethylene Based Composites

The effect of the addition of hydrolyzed thermoplastic maize starch on the physico mechanical properties of low-density polyethylene (LDPE)-based composites was studied. Acid-hydrolyzed native starch was thermoplasticized using 15 and 30% glycerol in weight relative to starch, after which the LDPE/thermoplastic starch (TPS) composites were prepared at TPS concentrations of 10, 25, and 50%. According to the results of Raman spectroscopy, the appearance of a new band at 756 cm-1 was observed, and it was attributed to the hydrolysis process and associated with the C-C-O vibrational modes of the glycosidic bond. The addition of both native and polyethylene hydrolyzed TPS reduced the Young's modulus of the composites; but the reduction was greater for those containing native starch. Both the maximum stress and deformation decreased to a greater degree for the composites with hydrolyzed TPS. The composites containing TPS prepared with 15% glycerol exhibited a higher Young's modulus compared to those with LDPE, although they exhibited fragile behavior. The degree of matrix crystallinity increased with the addition of TPS and showed the largest increase when TPS 50% hydrolyzed by weight was added, showing an increase of 35%. It was observed that the size of the TPS particles, both native and hydrolyzed, increased in size as the concentration of TPS in the matrix increased. The size of the hydrolyzed TPS particles was greater than that of the native TPS particles, and in the case the of the hydrolyzed TPS particles, some exhibited an ellipsoidal and/or fibrillar morphology

Effect of Dual Modification on the Spectroscopic, Calorimetric, Viscosimetric and Morphological Characteristics of Corn Starch

The effect of dual modification of corn starch, including hydrolysis and succinylation, were evaluated through peak viscosity (PV) analysis, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. This dual modification was shown to increase the reaction efficiency (RE) and degree substitution (DS) compared with starches that were not subjected to acid hydrolysis pretreatment with a 44% and 45% increase respectively. After acid hydrolysis pretreatment, the surface of the corn starch granules exhibited exo-erosion and whitish points due to the accumulation of succinyl groups. The peak viscosity was reduced significantly with the acid hydrolysis pretreatment (between 3 and 3.5-fold decrease), which decreased the pasting temperature and peak time to 20 °C and 100 s respectively. In addition, the dual modification of corn starch altered certain thermal properties, including a reduction in the enthalpy of gelatinization (ΔH) and a higher range of gelatinization (around 6 °C), which may effectively improve industrial applications. Modifications on the FTIR spectra indicated that the dual modification affected the starch crystallinity, while the Raman spectra revealed that the dual modification disrupted the short-range molecular order in the starch. Rearrangement and molecular destabilization of the starch components promoted their granular amphiphilic properties

Optimization of 2-Phenylethanol Production from Sweet Whey Fermentation Using Kluyveromyces marxianus

The growing demand for natural products benefits the development of bioprocesses to obtain value-added compounds using residues such as sweet whey, which is rich in lactose. The yeast Kluyveromyces marxianus can ferment sweet whey to obtain 2-phenylethanol (2-PhEtOH), which is a superior alcohol with a rose aroma. Such fermentation only requires the addition of L-phenylalanine (precursor) and (NH4)2SO4 (salt). Therefore, it was sought to improve the fermentation conditions to produce 2-PhEtOH, which, in turn, would achieve the maximum decrease in the Chemical Oxygen Demand (COD) of the fermentation medium. With the use of the Response Surface Methodology and the application of a Central Composite Design for optimization, two parameters were evaluated as a function of time: salt concentration and precursor. The experimental data were adjusted to a second order polynomial, identifying that the precursor concentration presents a statistically significant effect. The best conditions were: 4.50 g/L of precursor and 0.76 g/L of salt, with a maximum production of 1.2 g/L (2-PhEtOH) at 48 h and achieving a maximum percentage of COD removal of 76% at 96 h. Finally, the optimal conditions were experimentally validated, recommending the use of the model

Nutritional Characterization of Prosopis laevigata Legume Tree (Mesquite) Seed Flour and the Effect of Extrusion Cooking on its Bioactive Components

Mesquite (Prosopis laevigata) is a legume tree widely distributed in Aridoamerica. The mature fruit of this legume is a pod, which is currently underutilized and has high nutritional potential. In the present work, mesquite seed flour is described in terms of its nutritional value, as well as the effect of extrusion cooking on its bioactive components. Mesquite seed flour is rich in fiber (7.73 g/100 g) and protein (36.51 g/100 g), with valine as the only limiting amino acid. Total phenolic compound contents in raw and extruded seed flour were 6.68 and 6.46 mg of gallic acid equivalents/g (mg GAE/g), respectively. 2-2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity values in raw and extruded seed flour were 9.11 and 9.32 mg of ascorbic acid equivalent/g (mg AAE/g), respectively. The absorbance at 290 nm, as an indicator of generation of Maillard reaction product (MRP), was the same for raw and extruded samples. Apigenin was the only flavonoid found in mesquite seed flour (41.6 mg/kg) and was stable in the extrusion process. The water absorption index (WAI) and water solubility index (WSI) were changed significantly during extrusion. The expansion of mesquite seed flour extrudates was null due to the high protein and fiber content in the sample. Extrusion cooking of mesquite seed flour is a useful form of technology for the industrialization of this underutilized and nutritionally valuable legume

Physicochemical and sensory characterization of an extruded product from blue maize meal and orange bagasse using the response surface methodology

The mixtures of blue cornmeal and orange bagasse were processed in a single screw laboratory extruder. We used an experimental design, central composite rotatable, where the factors were as follows: extruder die temperature (153–187°C), feed moisture (146.4–213.6 g/kg), and orange bagasse concentration (32.7–167.3 g/kg). The results were analyzed by surface methodology response to evaluate the effect of these variables on the expansion index, bulk density, penetration force, specific mechanical energy, water absorption, and water solubility index. All independent variables had an effect on the evaluated responses (p ≤ 0.05). The highest expansion index was obtained at a feed moisture content of 146.4 g/kg, orange bagasse (100 g/kg), and 170°C at the exit die. The use of blue maize and orange bagasse can be an alternative to increase the added value of these two raw materials, and to improve the nutritional quality of extruded products ready to eat

Optimization of 2-Phenylethanol Production from Sweet Whey Fermentation Using <i>Kluyveromyces marxianus</i>

The growing demand for natural products benefits the development of bioprocesses to obtain value-added compounds using residues such as sweet whey, which is rich in lactose. The yeast Kluyveromyces marxianus can ferment sweet whey to obtain 2-phenylethanol (2-PhEtOH), which is a superior alcohol with a rose aroma. Such fermentation only requires the addition of L-phenylalanine (precursor) and (NH4)2SO4 (salt). Therefore, it was sought to improve the fermentation conditions to produce 2-PhEtOH, which, in turn, would achieve the maximum decrease in the Chemical Oxygen Demand (COD) of the fermentation medium. With the use of the Response Surface Methodology and the application of a Central Composite Design for optimization, two parameters were evaluated as a function of time: salt concentration and precursor. The experimental data were adjusted to a second order polynomial, identifying that the precursor concentration presents a statistically significant effect. The best conditions were: 4.50 g/L of precursor and 0.76 g/L of salt, with a maximum production of 1.2 g/L (2-PhEtOH) at 48 h and achieving a maximum percentage of COD removal of 76% at 96 h. Finally, the optimal conditions were experimentally validated, recommending the use of the model

Chemical and nutritional characterization of raw and thermal-treated flours of Mesquite (Prosopis laevigata) pods and their residual brans

Species of the genus Prosopis were a major staple food in Aridoamerica before the arrival of Europeans. In the present work, chemical and nutritional properties of Prosopis laevigata pods were described. The composition in weight of pods of P. laevigata was 44% mesocarp, 35% endocarp, and 21% exocarp. Sugars, including sucrose, glucose, fructose, and xylose, were important components of pods, reaching a total sugars content of 447 g/kg in mesocarp flour. Considering the FAO-recommended amino-acid scoring patterns for humans older than 3 years, high values of Lys and sulfur-containing amino acids were found in flours. Thermal treatment of flours increases significantly the phenolic compounds content and free-radical scavenging capacity, an effect associated with the generation of Maillard reaction products. Flours of mesquite pods are a good source of phenolic compounds, with significantly higher free-radical scavenging capacity than soybean and common bean

Isolation and Molecular Identification of <i>Serratia</i> Strains Producing Chitinases, Glucanases, Cellulases, and Prodigiosin and Determination of Their Antifungal Effect against <i>Colletotrichum siamense</i> and <i>Alternaria alternata</i> In Vitro and on Mango Fruit

Microorganisms represent a viable option for the control of phytopathogens. From the surface of healthy mangoes, different bacteria were isolated. For all isolated bacterial strains, we determined their antimicrobial activity against a fungal strain that caused anthracnose in mangoes and against Alternaria alternata, both in the culture medium and directly on mangoes. The bacterial strains with the highest antifungal activity were identified by sequencing the 16s rRNA gene. Two species of Serratia were identified: marcescens and nematodiphila. Finally, the chitinolytic, glucanolytic, and cellulolytic activity and prodigiosin production of bacteria with antifungal activity was determined. Five fungal strains were isolated from mangoes with anthracnose. Only one strain was responsible for anthracnose in mangoes. This fungal strain was identified as Colletotrichum siamense. Against C. siamense and A. alternata in vitro and in mango selected strains of Serratia showed antifungal activity. Finally, the Serratia strains produced chitinases, glucanases, cellulases and prodigiosin, and the two S. marcescens strains did not produce hemolysins. The three Serratia strains isolated in this study can potentially be used in the biological control of anthracnose caused by C. siamense and A. alternata on mango