Influences of Superheated Steam Roasting and Water Activity Control as Oxidation Mitigation Methods on Physicochemical Properties,Lipid Oxidation,and Free Fatty Acids Compositions of Roasted Rice

The feasibility of using superheated steam roasting and wetting to control the water activity in an optimal range to mitigate oxidation of roasted rice was evaluated. Changes in the bed temperature as well as rice kernel moisture content, water activity, and color were monitored during fluidized bed roasting with superheated steam and hot air at 170, 190, and 210 °C. Air‐roasted rice was rewetted to raise its water activity to 0.30 to 0.35. All the samples were analyzed for the total oil content, peroxide value (PV), thiobarbituric acid (TBA) value, and free fatty acids (FFA) content and compositions. Higher roasting temperatures, especially at 210 °C, led to a significant increase (P ≤ 0.05) in the total oil content of the roasted rice. Wetting led to a significant (P ≤ 0.05) decrease in the TBA value of the air‐roasted rice, although the total FFA content significantly (P ≤ 0.05) increased. Rice roasted in superheated steam at 210 °C exhibited significantly (P ≤ 0.05) lower PV and TBA value; their total FFA content also tended to decrease, which is desirable for a longer shelf life.     

Catalytic partial oxidation of CH4 over bimetallic Ni‐Re/Al2O3: Kinetic determination for application in microreactor

The activity of a novel Ni‐Re/Al₂O₃ catalyst toward partial oxidation of methane was investigated in comparison with that of a precious‐metal Rh/Al₂O₃ catalyst. Reactions involving CH₄/O₂/Ar, CH₄/H₂O/Ar, CH₄/CO₂/Ar, CO/O₂/Ar, and H₂/O₂/Ar were performed to determine the kinetic expressions based on indirect partial oxidation scheme. A mathematical model comprising of Ergun equation as well as mass and energy balances with lumped indirect partial oxidation network was applied to obtain the kinetic parameters and then used to predict the reactant and product concentrations as well as temperature profiles within a fixed‐bed microreactor. H₂ and CO production as well as H₂/CO₂ and CO/CO₂ ratios from the reaction over Ni‐Re/Al₂O₃ catalyst were higher than those over Rh/Al₂O₃ catalyst. Simulation revealed that much smoother temperature profiles along the microreactor length were obtained when using Ni‐Re/Al₂O₃ catalyst. Steep hot‐spot temperature gradients, particularly at the entrance of the reactor, were, conversely, noted when using Rh/Al₂O₃ catalyst. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1691–1701, 2018     

Effects of various pretreatments and drying methods on Salmonella resistance and physical properties of cabbage

The combined effects of pretreatment and drying methods on the resistance of Salmonella attached to vegetable surfaces as well as some physical properties, in terms of color and shrinkage, were investigated. Cabbage was used as a test vegetable and Salmonella Anatum was used as a test microorganism. Cabbage leaves were pretreated either by soaking in 0.5% (v/v) acetic acid for 5 min, blanching in hot water for 4 min or blanching with saturated steam for 2 min prior to either hot air drying, vacuum drying (10 kPa) or low-pressure superheated steam drying (10 kPa) at 60 °C. Based on an initial Salmonella contamination level of approximately 6.4 log CFU/g, soaking in acetic acid, hot-water and steam blanching resulted in 1.6, 3.8 and 3.6 log CFU/g reduction in the number of Salmonella, respectively. Drying without pretreatment could not completely eliminate Salmonella attached on the cabbage surfaces, while no Salmonella was detected on the pretreated samples at the end of the drying process. Volumetric shrinkage was not affected by the pretreatment and drying methods. Dried blanched samples exhibited greener and darker color than the dried acetic acid pretreated and untreated samples.     

Plant carotenoids evolution during cultivation,postharvest storage,and food processing: A review

Carotenoids in nature are predominantly C40 hydrocarbons that may contain oxygenated functional groups. Although they are well‐recognized to exhibit key human health benefits, they cannot be synthesized in the human body and must be obtained from the diet. Fruit and vegetables are the primary dietary sources of carotenoids because plants automatically synthesize these compounds to protect cells from oxidative damage that may occur upon photosynthesis due to light. Biosynthesis and accumulation of carotenoids in plants begin during cultivation through postharvest storage. However, these compounds naturally degrade upon plant senescence and also during food processing (e.g., blanching, pasteurization, and drying). In this article, evolution of carotenoids during cultivation, postharvest storage, and food processing is comprehensively reviewed. Appropriate conditions and methods to cultivate, store, and process fruit and vegetables to help retard carotenoid degradation and enhance carotenoid biosynthesis are also reviewed and identified.     

Selection of reference genes for quantitative real‐time PCR in postharvest tomatoes (Lycopersicon esculentum) treated by continuous low‐voltage direct current electricity to increase secondary metabolites

Quantitative real‐time PCR (RT‐qPCR) is often used for gene expression analysis to reveal molecular mechanism of how stresses can enhance the secondary metabolites production. For RT‐qPCR to be valid, robust reference genes are required. This study validated nine candidate genes as reference genes using BestKeeper, NormFinder and geNorm methods in RT‐qPCR analysis of postharvest tomatoes subjected to electricity‐induced stress. The most stable genes as indicated by each method were EF‐1α by BestKeeper; CAC by NormFinder; and PP2Acs/TIP41 by geNorm. Due to the inconsistency in the ranking of the candidate genes by the three methods, the pairwise variation from geNorm analysis was used to calculate the minimum numbers of reference genes for an accurate normalisation and revealed that a combination of PP2Acs and TIP41 was an optimum. This reference gene combination was further validated for their stability in RT‐qPCR analysis of four carotenoid‐related genes, and more reliable expression levels were obtained.     

Comparative Evaluation of Physical Properties of Edible Chitosan Films Prepared by Different Drying Methods

Edible films are alternative packaging, which have recently received much attention due mainly to environmental reasons. Edible films may be formed from edible biomaterials such as polysaccharides, proteins, or lipids. Among these biopolymers, chitosan is of interest because it has a good film-forming property and is biodegradable, biocompatible, and nontoxic. Several techniques have been used to prepare edible chitosan films with various degrees of success. However, it is always interesting to find an alternative technique to produce films of superior quality at shorter processing (drying) time. In this study, the influences of different drying methods and conditions on the drying kinetics and various properties of chitosan films were investigated. Drying at control conditions (ambient air drying and hot air drying at 40°C) as well as vacuum drying and low-pressure superheated steam drying (LPSSD) at an absolute pressure of 10 kPa were carried out at different drying temperatures (70, 80, and 90°C). The properties of chitosan films, in terms of color, tensile strength, percent elongation, water vapor permeability (WVP), glass transition temperature (T_g), and crystallinity, were also determined. Based on the results of both the drying behavior and film properties, LPSSD at 70°C was proposed as the most favorable conditions for drying chitosan films.     

EVALUATION OF SOME TRANSPORT AND THERMODYNAMIC PROPERTIES OF SUPERHEATED STEAM: EFFECTS OF STEAM TEMPERATURE AND PRESSURE

ABSTRACT

For machine computation of drying, humidification and dehumidification processes it is necessary to have reliable correlations to predict transport and thermodynamic properties of the drying medium as functions of temperature and pressure. In this paper empirical correlations for specific volume, dynamic viscosity, thermal conductivity as well as specific isobaric heat capacity of superheated steam over the temperature range of 160-500^° C and the pressure range of 100-500 kPa are presented. The Prandtl numbers at various temperatures and pressures are also presented. Comments on the properties and the use of these correlations are given.     

Artificial neural network modeling of physicochemical changes of shrimp during boiling

Frozen boiled shrimp and dried shrimp are among the high-value fishery products of Thailand. During the production of these products boiling is one of the most important steps that affects significantly the product physicochemical properties, especially the quantity and quality of proteins, which in turn affect other apparent properties perceived by consumers. The protein changes are, however, difficult to evaluate comparing to other typical physical properties of shrimp. The objective of this study was therefore to develop an artificial neural network (ANN) model to predict the protein changes of shrimp in terms of protein loss and protein denaturation as a function of the boiling conditions, namely, concentration of salt solution and boiling time, as well as a rather easily determined change of shrimp, that is, cooking loss. Other apparent physical changes of shrimp viz. shrinkage and hardness were also predicted. The optimized ANN structure for the prediction of protein changes consists of two hidden layers and twelve neurons per layer, while the optimized ANN structure for the prediction of physical changes consisted of two hidden layers and eight neurons per layer. The predicted protein and physical changes agreed very well with the experimental data with R² > 0.994 and 0.972, respectively.