The aim of this study is to analyze the properties of a series of polysaccharide composite films, such as apparent density, color, the presence of functional groups, morphology, and thermal stability, as well as the correlation between them and their antimicrobial and optical properties. Natural antioxidants such as anthocyanins (from cranberry; blueberry and pomegranate); betalains (from beetroot and pitaya); resveratrol (from grape); and thymol and carvacrol (from oregano) were added to the films. Few changes in the position and intensity of the FTIR spectra bands were observed despite the low content of extract added to the films. Due to this fact, the antioxidants were extracted and identified by spectroscopic analysis; and they were also quantified using the Folin-Denis method and a gallic acid calibration curve, which confirmed the presence of natural antioxidants in the films. According to the SEM analysis, the presence of natural antioxidants has no influence on the film morphology because the stretch marks and white points that were observed were related to starch presence. On the other hand, the TGA analysis showed that the type of extract influences the total weight loss. The overall interpretation of the results suggests that the use of natural antioxidants as additives for chitosan-starch film preparation has a prominent impact on most of the critical properties that are decisive in making them suitable for food-packing applications.
Hexamethylenediammonium thiometallate (HeDaT) of molybdenum and tungsten were synthesized using the aqueous solution method. This method improved significantly the yield of the catalysts. The HeDaT precursors were in situ activated during the hydrodesulfurization (HDS) of dibenzothiophene (DBT) generating MoS 2 and WS 2 catalysts. To characterize the precursors Fourier Transform Infra Red (FTIR), Ultraviolet (UV-Vis) and Nuclear Magnetic Resonance ( 1 H NMR) spectroscopy techniques were used to determine their chemical structures. In addition, thermal analysis (TGA-DTA) were performed to study the fragmentation and decomposition behavior of their molecular structures. Catalysts were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which showed the shapes of the particles and the characteristic fringes of the layered MoS 2 and WS 2 phases, respectively. Specific surface areas were determined by the BET method with values of 5 and 19 m 2 /g with type I and IV adsorption-desorption nitrogen isotherms for both catalysts. The X-ray diffraction study showed poorly crystalline catalysts with weak (002) intensity for the MoS 2 and a better-defined (002) reflection for the WS 2 .
During cocoa beans roasting, there are physicochemical changes that develop the chocolate quality attributes. Roasting systems have a particular influence on the development of these characteristics, and the effects of operation variables for each system must be evaluated. The objective of this study was to evaluate the effect of roasting time and temperature in a rotatory system on cocoa beans physicochemical parameters of quality as moisture, water activity, pH, total acidity, color ( * , * , * ), total phenolic content (TPC), and DPPH radical capacity. Cocoa beans were roasted as a function with a central rotatable design with 2 2 + 5 central points and 4 axial points (−1.414, −1, 0, +1, and +1,414) and a response surface methodology was applied. Temperature and time levels were 110-170 ∘ C and 5-65 minutes, respectively. The effect of the variables was nonlinear and modeled with a second-order response polynomial. Roasting time and temperature presented a significative effect ( < 0.05) on the response variables except for both TPC and DPPH radical capacity in aqueous extract.
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