An integrated Monte Carlo track-structure simulation framework for modeling inter and intra-track effects on homogenous chemistry.

Objective. The TOPAS-nBio Monte Carlo track structure simulation code, a wrapper of Geant4-DNA, was extended for its use in pulsed and longtime homogeneous chemistry simulations using the Gillespie algorithm.Approach. Three different tests were used to assess the reliability of the implementation and its ability to accurately reproduce published experimental results: (1) a simple model with a known analytical solution, (2) the temporal evolution of chemical yields during the homogeneous chemistry stage, and (3) radiolysis simulations conducted in pure water with dissolved oxygen at concentrations ranging from 10µM to 1 mM with [H2O2] yields calculated for 100 MeV protons at conventional and FLASH dose rates of 0.286 Gy s-1and 500 Gy s-1, respectively. Simulated chemical yield results were compared closely with data calculated using the Kinetiscope software which also employs the Gillespie algorithm.Main results. Validation results in the third test agreed with experimental data of similar dose rates and oxygen concentrations within one standard deviation, with a maximum of 1% difference for both conventional and FLASH dose rates. In conclusion, the new implementation of TOPAS-nBio for the homogeneous long time chemistry simulation was capable of recreating the chemical evolution of the reactive intermediates that follow water radiolysis.Significance. Thus, TOPAS-nBio provides a reliable all-in-one chemistry simulation of the physical, physico-chemical, non-homogeneous, and homogeneous chemistry and could be of use for the study of FLASH dose rate effects on radiation chemistry.

Physicochemical and rheological properties of purees based on Mafafa (Xanthosoma robustum) and quinoa (Chenopodium quinoa Willd.) with the addition of cryoprotectants.

Growing interest in processed frozen products with similar characteristics to natural products has generated the study of new products in the food industry field. The characteristics of each matrix, the process of elaboration, composition, and structure of the additives and the interactions amongst these modify the food's texture, structure, physical and sensory properties and, hence, interfere directly with consumer acceptance. This research studied the effect of adding cryoprotectors during frozen storage on the rheological, physicochemical, structural, and microbiological properties in a Mafafa-quinoa-olive oil puree. To carry out the study, the rheological properties were determined through dynamic oscillatory tests and in steady state; likewise, the physicochemical properties (humidity, color, pH, and syneresis) were analyzed. Regarding physicochemical properties, the humidity content in the purees formulated varied between 57 and 74%, without important variation (p > .05) with respect to the formulation, however, in the storage during the freezing/thawing process, this parameter diminished in greater proportion in those purees containing carrageenan as cryoconservant. Both the addition of cryoconservants and the storage time affected significantly (p < .05) the puree's syneresis, with the degree of exudation being lower in the formulation containing xanthan gum at 1% w/w. During the freezing/thawing process, decreased apparent viscosity was noted. Additionally, the analysis of the viscoelastic properties of the purees evidences that already described, given that a significant effect (p < .05) was observed of the formulation of purees in the elastic component G', in contrast with a notable decrease in the viscous component G″.

Mechanical, barrier, and color properties of banana starch edible films incorporated with nanoemulsions of lemongrass ( Cymbopogon citratus) and rosemary ( Rosmarinus officinalis) essential oils.

Edible films are among the most promising fields in food science over the last decade due to their versatility (they can be made from a wide array of materials) and because they can be used as carriers of different active substances, like antioxidants, antimicrobial agents, and essential oils from plants. In the case of the essential oils, their inclusion in edible films is limited by their low water solubility. Nanoemulsions are thermodynamically stable and transparent systems that can be used as a way of incorporating essential oils into edible film matrices. In this paper, we developed lemongrass and rosemary essential oil nanoemulsions by using a low-energy method, observing the effect of the surfactant/oil ratio in their physicochemical properties. Then we studied the effect of the nanoemulsions concentration incorporated into banana starch edible films. We observed that essential oils' nanoemulsions have a plasticizing effect increasing the film's water vapor permeability, transparency, and elongation at break, while the hydrophobic nature of the essential oils lead to a decrease in their water solubility.

The influence of Aloe vera gel incorporation on the physicochemical and mechanical properties of banana starch-chitosan edible films.

BACKGROUND: Aloe vera (AV) gel is a promising material in food conservation, given its widely reported antimicrobial and antioxidant activity; however, its application in the formation of edible films and coatings has been small owing its low film-forming capability. The aim of this study was to investigate the physicochemical properties of film-forming solutions and films prepared using unripe banana starch-chitosan and AV gel at different AV gel concentrations. RESULTS: Our results showed that AV gel considerably affected the rheological and optical properties of the edible coatings, mainly due to increased amounts of solids brought by the AV gel. Film-forming capacity and physicochemical properties were also studied; most of the film properties were affected by the inclusion of AV gel, with decreased water vapor permeability, tensile strength and elongation at break. Fourier transform infrared studies showed that the inclusion of AV gel disrupts the interaction between starch and chitosan molecules; however, further studies are needed to fully understand the specific interactions between the components of AV gel and both starch and chitosan molecules. CONCLUSION: Our results suggest that the addition of AV gel creates a crosslinking effect between the phenolic compounds in AV gel and starch molecules, which disrupts the starch-chitosan interaction and greatly affects the properties of both the film-forming solution and edible films. © 2018 Society of Chemical Industry.