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关键词： High oxygen   Carbon monoxide packaging   Dark cutting beef   Bacterial spoilage   Total volatile basic nitrogen  

摘要： The objective was to evaluate the effect of packaging conditions on bacteriological and biochemical changes in beef steaks classified here, as normal ultimate pH (pHu;5.40-5.79), intermediate pHu (5.80-6.09) or high pHu (>= 6.10). Steaks were packaged in vacuum packaging (VP) and modified atmosphere packaging with high oxygen (HiO(2)-MAP) or carbon monoxide (CO-MAP). Headspace, bacterial counts, total volatile basic nitrogen, pH, purge loss, surface color, lipid oxidation, and sensory attributes were monitored over a 14-day storage period at 2 degrees C. HiO(2)-MAP and CO-MAP of high pHu steaks resulted in a bright red color even when observed to be spoilt. Reduced purge loss and lipid oxidation, as well as increased sensory acceptability were observed for steaks with elevated pHu. Higher pHu was also accompanied by an acceleration of microbial proliferation. Of all packaging types investigated, CO-MAP exerted the best preservation, regardless of pHu and based on its antibacterial and antioxidant properties.

关键词： Fructose  

摘要： Three commercial and three natural honeys from Zambia and Botswana were analyzed for selected physicochemical parameters using analytical methods prescribed by the International Honey Commission. The parameters were specific conductivity, moisture/ash contents, pH, acidity by titration to pH 8.3, sucrose, fructose, and glucose. Multivariate statistical evaluation of the physicochemical data using partial least squares was used to classify the honeys according to their geographical and floral origins. Sugars were analyzed using Fourier transform infrared spectroscopy (FTIR) in which validation of the methods employed gave limits of detection (LODs) that ranged between 3.4 and 8.8 g/100 honey and correlation coefficients that ranged between 0.9779 and 0.9865. The concentration ranges for the sugars were (g/100 g honey) sucrose (ND - 10.4), fructose (22.4-28.4), and glucose (29.3-49.2). Overall, none of the honeys examined showed signs of adulteration with the three sugars. These data are lacking in many African countries, which are emerging as honey production giants. Practical applications We report physicochemical properties of selected raw natural and commercial honeys from Zambia and Botswana using the International Honey Commission guidelines. This is a prelude to database creation to protect apiarists from fraud in honey trade in many African countries emerging as giant honey producers and is to the best of our knowledge the first such report in the Southern African Development Community region.

关键词： biocompatibility   electron beam irradiation   poly(methyl methacrylate)   sterilization  

摘要： Electron beam (E-beam) irradiation is an attractive and efficient method for sterilizing clinically implantable medical devices made of natural and/or synthetic materials such as poly(methyl methacrylate) (PMMA). As ionizing irradiation can affect the physicochemical properties of PMMA, understanding the consequences of E-beam sterilization on the intrinsic properties of PMMA is vital for clinical implementation. A detailed assessment of the chemical, optical, mechanical, morphological, and biological properties of medical-grade PMMA after E-beam sterilization at 25 and 50 kiloGray (kGy) is reported. Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry studies indicate that E-beam irradiation has minimal effect on the chemical properties of the PMMA at these doses. While 25 kGy irradiation does not alter the mechanical and optical properties of the PMMA, 50 kGy reduces the flexural strength and transparency by 10% and 2%, respectively. Atomic force microscopy demonstrates that E-beam irradiation reduces the surface roughness of PMMA in a dose dependent manner. Live-Dead, AlamarBlue, immunocytochemistry, and complement activation studies show that E-beam irradiation up to 50 kGy has no adverse effect on the biocompatibility of the PMMA. These findings suggest that E-beam irradiation at 25 kGy may be a safe and efficient alternative for PMMA sterilization.

关键词： Amylose-lipid complex   FTIR spectroscopy   Hardness   Retrograded starch   Simulated digestion   X-ray diffraction  

摘要： Spray-dried resistant starch powder (SD) containing 35% amylose-lipid complex and retrograded starch and having in vitro glycemic index (GI) of 63 was incorporated into white bread at either 20, 30 or 50% (w/w). Increased hardness and less porous structure of bread were noted as SD content increased. GI values of all bread samples containing SD were unexpectedly higher than that of the control white bread, either right after baking or after 1-4 days of storage;GI increased with increased SD content. X-ray diffraction patterns and Fourier transform infrared spectra revealed that double-helix amylopectin in SD experienced complete gelatinization at the baking temperature and hence the higher GI values of bread samples containing SD. Higher content of digestible starch in SD (similar to 65%) also contributed to the higher GI values. Native A-type starch from wheat flour, on the other hand, partially remained in the control white bread, resulting in the lower GI value.

关键词： Quantum dots   Cytotoxicity   Physicochemical properties   Risk assessment   Toxicity mechanism  

摘要： Fluorescent quantum dots (QDs) have received extensive attention because of their excellent optical properties and wide utilization in biological and biomedical areas. Nonetheless, there have been intense concerns on the cytotoxicity assessment of cadmium-containing QDs due to free cadmium ions release and nano-size effects. This paper reviews the representative synthetic strategies for preparation of cadmium-containing QDs and their applications. Then the toxicity assessments of QDs from cell studies to animal models are discussed, which can aid in improving our understanding of the cytotoxicity of QDs, and the toxicity mechanism is proposed. Several critical physicochemical properties of QDs are discussed and suggestions are provided for optimizing QDs design in view of minimal cytotoxicity. Finally, accurate detection techniques and systematic methodologies for the toxicity assessment of QDs are expected to achieve further breakthroughs in the future, especially in-situ, realtime, and rapid quantitative analysis methods.

关键词： Surfactant-modified zeolite   Didodecyldimethylammonium bromide   Adsorption   Bisphenol-A   Propranolol hydrochloride  

摘要： Wastewater pollution by organic anions is of great interest. Surfactant-modified zeolites exhibit high adsorption of both organic and inorganic toxicants. Here, bisphenol-A and propranolol hydrochloride were adsorbed on natural zeolite modified with the cationic surfactant didodecyldimethylammonium bromide with and without pretreatment of the zeolite with NaCl and HCl. Detailed physicochemical analysis shows chemisorption, electrostatic and hydrophobic interactions with the surfactant and bisphenol-A, and in the case of propranolol, also physisorption.

关键词： Arachin   Basil seed gum   Composite gels   Calcium chloride   Sodium chloride   Gel properties  

摘要： In this study, the effects of calcium chloride (CaCl2) and sodium chloride (NaCl) with different concentrations (0-20 mM) on the properties of arachin and basil seed gum composite gels were investigated. The results showed that the G', G '' and gel strength of the composite gels were enhanced by Ca2+ and Na+ at a low concentration and decreased at high concentrations. An appropriate concentration of Ca2+ or Na+ (10 mM) strengthened the electrostatic forces, hydrophobic interactions, hydrogen bonds, disulfide bonds and facilitated a conformation conversion of the secondary structures from alpha-helix to beta-sheet. These changes were responsible for the improved hydration properties including water-holding capacity, freeze-thaw stability and swelling behavior of the composite gels in the presence of 10 mM Ca2+ or Na+, which could be explained by the images of compact and uniform microstructures. High concentration of salt ions (15-20 mM) hindered the formation of regular gel network. These findings may facilitate the design of arachin-based gel products with improved texture and sensory characteristics.

关键词： broccoli juice   spray drying   antioxidant activity   conservation of antioxidants   physicochemical characterization  

摘要： This research presents the microencapsulation and conservation of antioxidants of broccoli juice processed by spray drying, and proposes the use of a by-product as a technological application. Broccoli juice (BJ) extracted from two sources, stalks and florets, was spray-dried employing maltodextrin (MX) as a carrier agent at concentrations of 5, 7.5, and 10%, and inlet temperatures of 150 and 220 degrees C. The total phenolic content (TPC), and antioxidant activity (AA) of the BJ-MX powders were determined together with the physicochemical characteristics, including particle morphology, microstructure, and thermal properties. Based on the TPC and AA, the optimal processing conditions found were 5% of MX and a drying temperature of 220 degrees C. However, the florets showed higher TPC, while stalks presented higher AA under those processing conditions. The particles exhibited micrometric sizes and a mixture of spherical-shape particles and pseudo-spherical particles. The diffractograms indicated an amorphous microstructure in all samples. The glass transition temperature (Tg) was determined in the range of 50 degrees C for the samples dried at 150 degrees C and 55 degrees C for those dried at 220 degrees C. This suggested that powders might be stored at temperatures below the Tg without presenting any loss of antioxidants.

关键词： Agavins   Fat-reduced yogurt   Fat mimetic   Texture  

摘要： In this work, agavins (agave plant fructans) potential as fat replacer in dairy products was evaluated. Yogurt nonfat and fat reduced samples were prepared, agavins from Agave angustifolia and A. potatorum species were added to fat reduced products to evaluate their effect on the physicochemical, rheological, and sensory properties in the final products. Significant differences in the viscosity, syneresis and water retention capacity were observed among samples. All yogurts exhibited characteristics typical of a weak viscoelastic gel (G'>G") and strainthinning behavior. Physicochemical and rheological differences were strongly related to the agavins amount in yogurt fat-reduced samples. Agavins did not impact sensory attributes such color, smell, and taste in fact;they improved mouth feel and texture. HPAEC-PAD profiles demonstrated that agavins remain unaffected along the yogurt elaboration process. FTIR spectra showed remarkable differences on all final products composition, been more evident on fatty acids and carbohydrates regions. FTIR-PCA models allowed samples classification among treatments and samples discrimination according to the agavins content. Agavins addition to dairy products has a great potential as functional ingredient in the manufacture of low-fat, prebiotics and symbiotic products. Finally, compiled information increases our knowledge on the broad technological functionality that agavins may have in other food industry niches.

关键词： Rice bran oil   Chemical composition   Bioactive constituents   In vitro antioxidant activities  

摘要： The main aim of this study is to evaluate and compare the physicochemical properties, chemical composition, and in vitro antioxidant activities of rice bran oil (RBO) from five most popular japonica rice (Oryza sativa L.) varieties planted in China. It was found that the AV and PV of RBOs were 0.45-1.18 mg KOH/g and 0.72-1.73 mmol/kg, individually. The L*, a*, and b* values of RBOs were 24.18-26.70, 1.84-2.54, and 6.35-9.01, respectively. RBOs were rich in linoleic acid (38.63-43.50%), oleic acid (34.23-41.20%), and palmitic acid (16.26-18.93%). POL + SLL (17.44-19.29%), OLL (16.06-17.67%), OOL (13.79-17.79%), and PLL (11.70-14.79%) were the predominant triacylglycerols of RBOs. RBO from different rice varieties contained abundant bioactive constituents such as tocopherols and tocotrienols (948.59-1461.90 mg/kg), squalene (2055.65-4456.79 mg/kg), gamma-oryzanol (19391.15-30024.09 mg/kg), phytosterols (10632.74-13948.17 mg/kg), and polyphenols (127.55-358.84 mg/kg). Pigments such as carotenoids and chlorophylls varied from 6.47 to 14.29 mg/kg and 0.79 to 12.96 mg/kg. The DPPH, ABTS, FRAP, and ORAC value were 837.41-1055.64, 1592.38-2106.47, 244.27-557.13, and 170.16-1776.41 mu mol TE/100 g, respectively. This work could provide useful information to consumers for choosing suitable vegetable oils based on their health needs.