Detecting Aspergillus parasiticus in cereals by an enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) was used for the specific detection of Aspergillus parasiticus molds in artificially contaminated corn, rice, wheat and peanut, and also to detect naturally occurring aflatoxigenic molds in the same form cereals. After inoculation of Aspergillus parasiticus in the cereals, the growth of A. parasiticus was monitored by both plate count and ELISA, and the aflatoxin content was measured. Water activity (a_w) affected the fungal growth, aflatoxin production and degradation. The higher a_w level (a_w=0.98 vs. a_w=0.92) resulted in higher fungal growth rates and fungal masses in corn, rice and wheat, and the plate count and ELISA measurements were better correlated, with correlation coefficients of 0.94, 0.93, 0.96 and 0.86, respectively for corn, rice, wheat, and peanuts. Aflatoxin was also both produced sooner and degraded more rapidly at a_w=0.98. Although standard plate counting techniques detected A. parasiticus/A. flavus in 5 out of the 40 cereal samples bought from retail stores, ELISA did not give a positive result in any of them. After moisturization and incubation of these commercial samples at 28°C for 29 days, the incident rates of aflatoxigenic molds increased to 65% and 52% by plate count and ELISA, respectively.     

酒曲中产香霉菌的筛选及其培养条件优化

通过初筛、复筛对从大曲、小曲及麸曲等酒曲中筛选得到的25株霉菌进行产香能力研究,筛选出产香能力强的菌株并对其生长条件进行优化。研究结果发现,霉菌M23产香能力最强,总酯含量达到1.765 g/L;霉菌M23的最佳生长条件为温度30℃、初始p H值6.0、耗氧量150 r/min,此条件下菌丝体干重达到6.25 g/L,其中,培养温度和耗氧量对霉菌M23的生长具有显著性影响(P<0.05),初始pH值对其生长具有极显著性影响(P<0.01)。     

应用DGGE技术研究玉米储藏过程中的霉菌群落时空分布特征

研究储粮过程中霉菌污染的发生规律,旨在减少霉菌及真菌毒素的污染,提高我国粮食安全。利用变性梯度凝胶电泳研究粮库中不同储藏时间和空间的玉米样品中霉菌群落的特点。结果表明,本研究中储藏玉米的霉菌污染以青霉、曲霉和毛霉为主,其霉菌群落的变化与储藏时间具有较强的相关性,而与其在粮库中的空间位置相关性较小。在储藏时间方面,储藏1a和3a的样品中霉菌群落具有较大的差异,而储藏2a样品的霉菌群落处于过渡期状态。本实验探究储藏玉米中霉菌群落的时空分布特征,可以为建立准确可靠的霉菌群落模型提供理论支持和数据支持。     

Culture-independent study of the diversity of microbial populations in brines during fermentation of naturally-fermented Aloreña green table olives

Aloreña table olives are naturally fermented traditional green olives with a denomination of protection (DOP). The present study focused on Aloreña table olives manufactured by small and medium enterprises (SMEs) from Valle del Guadalhorce (Southern Spain) under three different conditions (cold storage, and ambient temperature fermentations in small vats and in large fermentation tanks). The microbial load of brines during fermentation was studied by plate counting, and the microbial diversity was determined by a culture-independent approach based on PCR-DGGE analysis. The viable microbial populations (total mesophilic counts, yeasts and molds, and lactic acid bacteria — LAB) changed in cell numbers during the course of fermentation. Great differences were also observed between cold, vat and tank fermentations and also from one SME to another. Yeasts seemed to be the predominant populations in cold-fermented olives, while LAB counts increased towards the end of vat and tank fermentations at ambient temperature. According to PCR-DGGE analysis, microbial populations in cold-fermented olives were composed mostly by Gordonia sp./Pseudomonas sp. and Sphingomonas sp./Sphingobium sp./Sphingopyxis sp. together with halophilic archaea (mainly by haloarchaeon/Halosarcina pallida and uncultured archaeon/uncultured haloarchaeon/Halorubrum orientalis) and yeasts (Saccharomyces cerevisiae and Candida cf. apicola). Vat-fermented olives stored at ambient temperature included a more diverse bacterial population: Gordonia sp./Pseudomonas sp., Sphingomonas sp./Sphingobium sp./Sphingopyxis sp. and Thalassomonas agarivorans together with halophilic archaea and yeasts (mainly S. cerevisiae and C. cf. apicola, but also Pichia sp., and Pichia manshurica/Pichia galeiformis). Some LAB were detected towards the end of vat fermentations, including Lactobacillus pentosus/Lactobacillus plantarum and Lactobacillus vaccinostercus/Lactobacillus suebicus. Only the tank fermentation showed a clear predominance of LAB populations (Lactobacillus sp., Lactobacillus paracollinoides, and Pediococcus sp.) together with some halophilic archaea and a more selected yeast population (P. manshurica/P. galeiformis). The present study illustrates the complexity of the microbial populations in naturally-fermented Aloreña table olives.     

Evaluation of chitosan nanoparticles as a glazing material for cryogenically frozen shrimp

The potential of chitosan (CH) combined with sodium tripolyphosphate (TPP) nanoparticles as a glazing material for shrimp was investigated. Two CH–TPP nanoparticles glazing solutions were prepared: (1). A solution containing CH–TPP nanoparticles with 0.25 (g/100 mL) CH and 0.083 (g/100 mL) TPP (25CH–TPP) and (2). A solution containing CH–TPP nanoparticles with 0.5 (g/100 mL) CH and 0.167 (g/100 mL) TPP (50CH–TPP). Frozen shrimp samples were glazed with 25CH–TPP, 50CH–TPP, CH, TPP, acetic acid, and/or distilled water and then stored at −21 °C for 30 days. Glazed and non-glazed shrimp (NG) samples were analyzed for moisture content, glazing yield, weight loss, color, cutting force, thiobarbituric acid reactive substances (TBARS), yeasts, molds, coliforms and aerobic counts after 1, 3, 5, 20, and 30 d storage. Triplicate experiments were conducted and data statistically analyzed (α = 0.05). Glazed shrimp had higher moisture than NG after 30 d storage. Among the glazes, 25CH–TPP and 50CH–TPP were the most effective in controlling lipid oxidation and reducing aerobic counts and yeasts and molds in shrimp.     

STUDY ON ACCURACY OF ADVANCED COMPOSITE TOOLS

Many high precision composite parts, fabricated by means of either hand lay-up or resin transfer molding, are now formed on advanced composite tools (ACTs). Trial and error methods for making accurate ACTs are time consuming and expensive. This paper investigates the effects of processing on the accuracy of ACTs for flat plates. Plate-shaped tools made of woven fabric graphite/epoxy were tested. The accuracy increased considerably as the laminate thickness increased, and it was found that 16 plies, at least, should be adopted in an ACT. Curing of ACTs at a lower temperature and then postcuring at a high temperature resulted in reduced curvature. The metallography revealed a volume-fraction gradient through the laminate thickness. This volume-fraction gradient always resulted in convex upward curvature. In addition, the accuracy of angle composite components with various radii was tested. The results showed that the accuracy of angle composite components was independent of the tool radius.     

Design and analysis of a reconfigurable discrete pin tooling system for molding of three-dimensional free-form objects

This paper presents the design and analysis of a new reconfigurable tooling for the fabrication of three-dimensional (3D) free-form objects. The proposed reconfigurable tooling system comprises a set of matrices of a closely stacked discrete elements (i.e., pins) arranged to form a cavity in which a free-form object can be molded. By reconfiguring the pins, a single tool can be used in the place of multiple tools to produce different parts with the involvement of much lesser time and cost. The structural behavior of a reconfigurable mold tool under process conditions of thermoplastic molding is studied using a finite element method (FEM) based methodology. Various factors that would affect the tool behavior are identified and their effects are analyzed to optimally design a reconfigurable mold tool for a given set of process conditions. A prototype, open reconfigurable mold tool is developed to present the feasibility of the proposed tooling system. Several case studies and sample parts are also presented in this paper.     

Microbial volatile organic compounds in the air of moldy and mold-free indoor environments

A single-blinded study was performed to analyze whether indoor environments with and without mold infestation differ significantly in microbial volatile organic compounds (MVOC) concentrations. Air sampling for MVOC was performed in 40 dwellings with evident mold damage and in 44 dwellings, where mold damage was excluded after a thorough investigation. The characteristics of the dwellings, climatic parameters, airborne particles and air exchange rates (AER) were recorded. The parameters mold status, characteristics of the interiors and measured climatic parameters were included in the multiple regression model. The results show no significant association between most of the analyzed MVOC and the mold status. Only the compounds 2-methyl-1-butanol and 1-octen-3-ol indicated a statistically significant, but weak association with the mold status. However, the concentrations of the so-called MVOC were mainly influenced by other indoor factors. 2-Methylfuran and 3-methylfuran, often used as main indicators for mold damage, had a highly significant correlation with the smoking status. These compounds were also significantly correlated with the humidity and the AER. The compounds 3-methyl-1-butanol, 2-hexanone, 3-heptanone and dimethyl disulfide were weakly correlated with the recorded parameters, the humidity being the strongest influencing factor. Only 2-methyl-1-butanol and 1-octen-3-ol showed a statistically significant association with the mold status; however, only a small portion (10% in this case) of the total variability could be explained by the predictor mold status; they do not qualify as indicator compounds, because such minor correlations lead to a too excessive part of incorrect classifications, meaning that the diagnostic sensitivity and specificity of these compounds are too low. PRACTICAL IMPLICATIONS: The assumption that mold infestations might be detected by microbial VOC emissions must be considered with great reservation. The major part of the total variability of the measured MVOC concentrations originates from not known influencing factors and/or from factors not directly associated with the mold status of the dwellings (confounders). More specific and sensitive markers for the assessment of the mold status should be found, if the screening for mold infestations should be performed by volatile organic compounds.     

Physical modeling of gas-liquid interfacial fluctuation in a thick slab continuous casting mold with argon blowing

Combining with the physical model of level fluctuation in a thick slab continuous casting mold with the cross-section of 1500 mm×280 mm and argon blowing, the rationalities of estimating the level fluctuation by three traditional quantitative approaches were discussed, and the effects of gas flowrate, casting speed, and the immersion depth of submerged entry nozzle (SEN) on the level fluctuation were also investigated. As a result, it seems that three traditional quantitative approaches are not very suitabl...     

Porosity,Microstructure and Thermal Stability of Microwave-cured Polymeric Denture Molds

Abstract

The relevance of controlling the chemical structure, thermal stability, composition and the porosity, of microwave-cured polymeric denture-molds is a key parameter if some degree of control of the corresponding adhesion among components is to be achieved. Different microwave-cured only polymer blends (Epoxy resin + Hardener) for producing denture molds were characterized by different techniques and compared to microwave-cured composites, also used for producing denture molds (Epoxy resin + Hardener + Alumina). In both cases the porosity was characterized by SEM, and the best material (in terms of porosity) was then subjected also to thermal and structural characterization. The results show the lowest porosity for the 90% Epoxy resin + 10% Hardener blend. The morphology shows a homogeneous surface with irregular particles smaller than five microns and voids-free. Also, the optimum temperature 100.8[ddot]C for microwave-cured denture molds was achieved with only a 0.64% loss of the original mass.