Saprophytic yeasts: effective biocontrol agents against Aspergillus flavus

Aflatoxins are carcinogenic, mutagenic and teratogenic fungal toxins predominantly produced by Aspergillus flavus (A. flavus) and Aspergillus parasiticus (A. parasiticus). Members of the Aspergillus family are wound-invading pathogens that can infect pistachio trees and nuts. The pistachio nut is a favorite tree nut worldwide, and more than half of the world's pistachio production is from Iran. Pistachio nuts can easily be infected with Aspergillus spp. due to early splitting or due to animal, insect or physical damage. Any established infection of Aspergillus under high relative humidity and temperature results in the production and rapid accumulation of aflatoxins in pistachio nuts. It is impractical to remove aflatoxins from pistachio nuts after they are produced. Some microorganisms (such as saprophytic yeasts) have been reported to have an antagonistic effect against Aspergillus spp. This study aimed to isolate saprophytic yeasts from pistachio fruits and leaves and investigate their biocontrol activities against a toxigenic strain of Aspergillus flavus (A. flavus). Saprophytic yeasts were identified based on their morphological properties and biochemical tests. In total, 24 yeast isolates were obtained from pistachio fruits and leaves, and their antagonistic effect on A. flavus (PTCC 5006) was investigated. Five saprophytic yeast isolates, displaying the highest biocontrol activities against A. flavus (PTCC 5006), were identified as Pseudozyma fusiformata, Cryptococcus albidus, Rhodotorula fragaria, Cryptococcus hungaricus and Rhodotorula hinula. The biocontrol activities of these yeast isolates were evaluated by their inhibitory effects on sporulation, colony expansion, biomass production and prevention of aflatoxin B1 (AFB1) production. Pseudozyma fusiformata was the most effective yeast isolate in terms of spore reduction (84.6%) and inhibition of AFB1 production (89.1%). Cryptococcus albidus produced the maximum reduction in fungal dry weight (77.9%). Based on these results, isolated saprophytic yeasts from pistachio fruits and leaves can be used as effective biocontrol agents against the growth of Aspergillus and aflatoxin production

A Comprehensive Review on Food Applications of Terahertz Spectroscopy and Imaging.

Food product safety is a public health concern. Most of the food safety analytical and detection methods are expensive, labor intensive, and time consuming. A safe, rapid, reliable, and nondestructive detection method is needed to assure consumers that food products are safe to consume. Terahertz (THz) radiation, which has properties of both microwave and infrared, can penetrate and interact with many commonly used materials. Owing to the technological developments in sources and detectors, THz spectroscopic imaging has transitioned from a laboratory-scale technique into a versatile imaging tool with many practical applications. In recent years, THz imaging has been shown to have great potential as an emerging nondestructive tool for food inspection. THz spectroscopy provides qualitative and quantitative information about food samples. The main applications of THz in food industries include detection of moisture, foreign bodies, inspection, and quality control. Other applications of THz technology in the food industry include detection of harmful compounds, antibiotics, and microorganisms. THz spectroscopy is a great tool for characterization of carbohydrates, amino acids, fatty acids, and vitamins. Despite its potential applications, THz technology has some limitations, such as limited penetration, scattering effect, limited sensitivity, and low limit of detection. THz technology is still expensive, and there is no available THz database library for food compounds. The scanning speed needs to be improved in the future generations of THz systems. Although many technological aspects need to be improved, THz technology has already been established in the food industry as a powerful tool with great detection and quantification ability. This paper reviews various applications of THz spectroscopy and imaging in the food industry

THE EMERGENCE OF GREEN MATERIALS AND TECHNOLOGIES IN HISTORIC BUILDING ADAPTATION CASE STUDY: TABRIZ HISTORIC BAZAAR COMPLEX

The adverse environmental condition of the 21st century can impede sustainable settlement in buildings for future use. However, historic buildings as an example of vernacular architecture have potential to provide a healthy indoor that resists the 21st-century climate change. With proper adaptation and improvements, not only such buildings provide a healthy indoor environment but also, they can control the new adverse climatic conditions. Muzaffarieh carpet market located in Tabriz Historic Bazaar Complex (THBC), as a practical example of vernacular architecture in Tabriz city, has the potential to withstand the adverse environmental conditions of the 21st century. However, lack of local action plans and guidelines is a limit in the adaptation of this market to climate change. Through a comprehensive theoretical framework, the presented study reviews the sustainable strategies for adaptation of Muzaffarieh carpet market. Data and information are collected from recent reports and articles for this location; though, to find substantial evidence of the conditions need further investigation. The aim is to supply indoor spaces with solutions concerning healthy air and water efficiency and to come up with an educational approach for informing shopkeepers. Here, the adaptation plan for the indoor environment is suggested through studying a number of historic buildings in the U.S. that are certified as green buildings with similar climates like Tabriz. The presented suggestions can ensure the sustainable presence of users in THBC for a longer time

Optimization of HPLC conditions for quantitative analysis of aflatoxins in contaminated peanut.

The main objective of present study was to investigate the effect of HPLC conditions namely mobile phase composition (X1), flow rate (X2) and temperature (X3) on peak area of four target aflatoxins (i.e. B1 (Y1), B2 (Y2), G1 (Y3) and G2 (Y4)) from the spiked peanut. The significant nonlinear response surface models with high coefficient of determinations (R2) ranging from 0.958 to 0.995 were fitted to evaluate the detection value of target aflatoxins as a function of HPLC variables. Flow rate had the most significant (p < 0.05) effect on quantification value of target aflatoxins. The highest quantification value for target aflatoxins could be obtained under the following HPLC conditions: the mobile phase composition of ACN/H2O/MeOH: 8/54/38, temperature of 24 °C and flow rate of 0.4 mL/min. The recommended optimum HPLC conditions provided higher peak area for all target aflatoxins by 1-2.5 fold compared to two other conditions (A: mobile phase (ACN/H2O/MeOH: 23/54/23), ambient temperature (28-32 °C), flow rate 1 mL/min; B: mobile phase (ACN/H2O/MeOH: 17/54/29), temperature 30 °C, flow rate 1 mL/min)

A review on mycotoxins in food and feed: Malaysia case study

Fungi are distributed worldwide and can be found in various foods and feedstuffs from almost every part of the world. Mycotoxins are secondary metabolites produced by some fungal species and may impose food safety risks to human health. Among all mycotoxins, aflatoxins (AFs), ochratoxin A (OTA), trichothecenes, deoxynivalenol (DON and T-2 toxin), zearalenone (ZEN), and fumonisins (FMN) have received much attention due to high frequency and severe health effects in humans and animals. Malaysia has heavy rainfall throughout the year, high temperatures (28 to 31 °C), and high relative humidity (70% to 80% during wet seasons). Stored crops under such conditions can easily be contaminated by mycotoxin-producing fungi. The most important mycotoxins in Malaysian foods are AFs, OTA, DON, ZEN, and FMN that can be found in peanuts, cereal grains, cocoa beans, and spices. AFs have been reported to occur in several cereal grains, feeds, nuts, and nut products consumed in Malaysia. Spices, oilseeds, milk, eggs, and herbal medicines have been reported to be contaminated with AFs (lower than the Malaysian acceptable level of 35 ng/g for total AFs). OTA, a possible human carcinogen, was reported in cereal grains, nuts, and spices in Malaysian market. ZEN was detected in Malaysian rice, oat, barley, maize meal, and wheat at different levels. DON contamination, although at low levels, was reported in rice, maize, barley, oat, wheat, and wheat-based products in Malaysia. FMN was reported in feed and some cereal grains consumed in Malaysia. Since some food commodities are more susceptible than others to fungal growth and mycotoxin contamination, more stringent prevention and control methods are required

Assessing biofilm formation by Listeria monocytogenes

Listeria monocytogenes(L. monocytogenes) is a serious food-borne pathogen for immunocompromised individuals. L. monocytogenes is capable of producing biofilm on the surface of food processing lines and instruments. The biofilm transfers contamination to food products and impose risk to public health. Transfers contamination to food products, and impose risk hazard to public health. The aim of this study was to investigate biofilm producing ability of L. monocytogenes isolates. Microtitre assay was used to measure the amount of biofilm production by ten L. monocytogenes isolates from minced chicken / meat, sausages and burgers. Results showed that all 10 L. monocytogenes isolates were able to form biofilm after 24 h at 20 ̊C on polystyrene surface (the common surface in food industries). Some strains were capable of forming biofilm more than the others. All strains showed a slight raise in the quantities of attached cells over 48 and 72 h. L. monocytogenes strains isolated from minced chicken, minced meat and burgers were better biofilm-producers comparing to the strains isolated from sausages

Efficiency of four Malaysian commercial disinfectants on removing Listeria monocytogenes biofilm

Listeria monocytogenes(L. monocytogenes) is a gram positive food-borne pathogen that is able to form biofilm on food factory surfaces. Formation of biofilm makes the bacteria much more resistance to environmental stresses such as disinfectant. The extracellular polymeric matrix (biofilm structure) which is mostly comprised of sticky extracellular polysaccharides (EPS) and proteins can protect bacteria in a harsh condition. The efficiency of four disinfectants on removing L. monocytogenes biofilm was investigated. Five concentration levels (100, 50,25, 12.5, and 6.25%) of disinfectants were tested. In the microtitre assay, the optical density at 595 nm CV-OD 595 value, was used to measure the amount of remained biofilm after 24 h. Results showed that disinfectants did not have significant effect on removing L. monocytogenes biofilm. Formation of L. monocytogenes biofilm significantly decreased the efficiency of disinfectants. Biofilm produced by strain number 9 showed higher resistance to disinfectant. Low concentrations (<50%) of disinfectants did not show significant effect on removing L. monocytogenes biofilm

Influence of different mobile phase compositions on detection of Ochratoxin A.

Ochratoxin A (OTA) is a possible human carcinogen that can be found in a variety of foodstuffs. High performance liquid chromatography (HPLC) is the chosen method for the quantification of OTA in food for human and animal consumption. The aim of the present study was to investigate the influence of different mobile phase compositions on the quantification (as measured by the peak area) of OTA. Different mobile phases were designed to study the effects of the mobile phase composition, pH, type and molarity of salt, the addition of acid and the chosen excitation wavelength on the detection of OTA. Results from thirteen mobile phase compositions showed that the mobile phase composition of ACN/NaAcetate (5 mM)/MeOH/Acetic acid (pH 3); (30:40:30; v/v/v) resulted in the highest quantification value for OTA. The designed mobile phase provided a significantly (p < 0.05) greater OTA peak area compared to other mobile phase compositions used as references. Results showed that for a mobile phase without salt, the best quantification value for OTA was achieved at low pH (∼3). When comparing two mobile phases with equal pH, the mobile phase with the lower salt molarity resulted in a greater peak area. For two mobile phases with equal salt molarity, the mobile phase with the lower pH provided a greater peak area. OTA showed two different excitation maxima (333 nm and 226 nm) depending on the mobile phase composition

Numerical simulation of nanofluids flow and heat transfer through isosceles triangular channels

Nanofluids are stable suspensions of nanoparticles in conventional heat transfer fluids (base fluids) that exhibit better thermal characteristics compared to those of the base fluids. It is important to clarify various aspects of nanofluids behavior. In order to identify the thermal and hydrodynamic behavior of nanofluids flowing through non-circular ducts, in the present study the laminar flow forced convective heat transfer of Al2O3/water nanofluid thorough channels with isosceles triangle cross section with constant wall heat flux was studied numerically. The effects of nanoparticle concentration, nanofluid flow rate and geometry of channels on the thermal and hydrodynamic behavior of nanofluids were studied. The single-phase model was used in simulations under steady state conditions. Results reveal that the local and average heat transfer coefficients of nanofluids are greater than those of the base fluid. Heat transfer coefficient enhancement of nanofluids increases with increase in nanoparticle concentration and Reynolds number. The local heat transfer coefficient of the base fluid and that of the nanofluids decrease with the axial distance from the channel inlet. Results also indicate that an increase in the apex angle of the channel, decreases the Nusselt number and heat transfer coefficient. The wall friction coefficient decreases with increasing axial distance from the channel inlet and approaches a constant value in the developed region. Friction coefficient and pressure drop decrease by increasing the apex angle of the channels

Sensorless Commutation Method for Low-Voltage BLDC Motors Based on Unfiltered Line Voltage

This study presents a filterless and sensorless commutation method for low-voltage brushless DC motors. The proposed method utilizes controlled DC-link inverter instead of the Pulse-Width Modulation (PWM) scheme. Therefore, motor voltages and currents become free from the high-frequency noise of PWM switching, thereby decreasing motor losses. Consequently, the method does not require any Low-Pass Filter (LPF) and it does not involve speed-dependent phase delay caused by the LPF. However, current commutation deteriorates waveform of line voltages. Thus, specific functions are defined to compensate for the current commutation spikes and remove false zero-crossing points of line voltages. Furthermore, the use of unfiltered line voltages eliminates the requirement of any phase shifter. Hence, the main superiority of the proposed method over preceding sensorless commutation methods is the simultaneous elimination of the phase shifter and LPF, which makes the method simple and cost-effective. The simulation and experimental results show the effectiveness and validity of the method