Improvement of gelation properties of myofibrillar proteins from porcine longissimus dorsi muscle through microwave combined with air convection thawing treatment

The effects of the microwave combined with air convection thawing(MAT)on the gelling properties of pork myofibrillar proteins(MPs)were further studied and compared with those of fresh meat(FM),and single thawing methods(microwave thawing(MT)and air convection thawing(AT)).Results revealed that the thawing methods,excluding MAT,induced deterioration in the gelling properties of MPs.There was no significant difference(p>0.05)in the water holding capacity(WHC),cooking loss,whiteness,and strength of gel samples subjected to MAT and those of FM samples,demonstrating that the gelling properties were retained after MAT.As well,protein aggregation was limited,since MAT reduced the change in zeta potential and turbidity compared to that observed with MT or AT.The dynamic rheology and scanning electron microscopic results were relatively consistent,revealing that among the different thawing techniques,MAT had the least negative impact on the microstructure of MPs gel,leading to the generation of a more elastic and uniform gel structure than that of the MT or AT gels.Moreover,MAT resulted in higher water retention in the gels than that achieved with MT or AT.These findings indicated that MAT improved the gelling properties of MPs,thereby confirming the suitability of this treatment for use in the meat processing industry.

In-situ testing study on convection and temperature characteristics of a new crushed-rock slope embankment design in a permafrost region

For the purpose of enhancing air convection and controlling solar radiation, a new crushed-rock slope embankment design combined with a sun-shade measure is proposed. A newly designed embankment was constructed in the Tuotuohe section of the Qinghai-Tibet Railway and a field-testing experiment was carried out to determine its convection and temperature characteristics. The results show that distinct air convection occurred in the crushed-rock layer of the new embankment, especially in cold seasons, which was enhanced when it flowed upwards along the slope. This preliminarily indicated that the new design of the embankment slope was good for reinforcing air convection in the crushed-rock layer. The frequent fluctuations of the convection speed and the environmental wind speed were in good agreement, suggesting that the convection in the crushed rock primarily came from the ambient wind. It was also preliminarily determined that the new embankment had a better cooling effect and sun-shade effect for decreasing the temperature of the embankment slope compared with a traditional crushed-rock slope embankment, and the mean temperature difference between them was up to 1.7 °C. The mean annual temperature at the bottom boundary of the crushed-rock layer was obviously lower than that at the top boundary, and heat flux calculation showed that the shallow soil beneath the embankment slope was weakly releasing heat, all of which indicated that the new embankment slope design was beneficial to the thermal stability of the embankment. This study is helpful in providing some references for improved engineering design and maintenance of roadbeds in permafrost regions.

PIV MEASUREMENTS FOR GAS FLOW UNDER GRADIENT MAGNETIC FIELDS

Particle Image Velocimetry(PIV)techniques were developed to measure the convec- tive N_2-air flow under gradient magnetic fields.The velocity fields were calculated by the Minimum Quadratic Difference(MQD)algorithm and spurious vectors were eliminated by Delaunay Tessellation. The N_2-air flow was measured as the magnetic flux density varying from 0～1.5 T.A strengthened vortex flow of air was observed under the condition that the magnetic field was applied,and the ve- locity of N_2 jet rose with the increase of the magnetic density.The experimental results show that the magnetic force will induce a vortex flow and cause a convection flow of the air mixture when both gradients of the O_2 concentration and the magnetic field intensity exist.

Performance improvement of air-breathing proton exchange membrane fuel cell(PEMFC) with a condensing-tower-like curved flow field

Air-breathing proton exchange membrane fuel cells(PEMFCs) are very promising portable energy with many advantages. However, its power density is low and many additional supporting parts affect its specific power. In this paper, we aim to improve the air diffusion and fuel cell performance by employing a novel condensing-tower-like curved flow field rather than an additional fan, making the fuel cell more compact and has less internal power consumption. Polarization curve test and galvanostatic discharge test are carried out and proved that curved flow field can strengthen the air diffusion into the PEMFC and improve its performance. With appropriate curved flow field, the fuel cell peak power can be 55.2%higher than that of planar flow field in our study. A four-layer stack with curved cathode flow field is fabricated and has a peak power of 2.35 W(120 W/kg).

Performance of a collector-storage solar air heating system for building mechanical ventilation preheating in the cold area

The application of solar thermal energy to preheat cold fresh air for mechanical ventilation could save a lot of energy and ensure the stable operation of the ventilation system.In this paper,a kind of collector-storage solar air heating system(CSSAHS),in which the thermal storage unit(TSU)is characterized by a dual S-channel for heat transfer,is proposed and the mathematical model for the integrated system was established.The model including the TSU,solar air collector,heat recovery device,and the fan was verified by an experimental study set up in a typical cold city in China.The model has been verified by experiments.The simulation results demonstrate that fresh air is the most important factor affecting storage/release efficiency.The increasing rate of heat release efficiency in the range of fresh air temperature-6-18°C is about 1.58%/°C.The solar heat collector area and the size of the TSU suitable for representative cities in cold regions are optimized based on multi-condition simulation analysis.The CSSAHS can preheat fresh air for 5 h after heat storage and the release efficiency is between 52 and 74%.Compared with other systems,the energy-saving rate of the CSSAHS is 26.5-33.3%in cold winter,and the heat supply ratio of the TSU is 24.4-35.1%.

ANFIS and ANNs model for prediction of moisture diffusivity and specific energy consumption potato,garlic and cantaloupe drying under convective hot air dryer

The main purpose of this study was to develop and apply an adaptive neuro-fuzzy inference system(ANFIS)and Artificial Neural Networks(ANNs)model for predicting the drying characteristics of potato,garlic and cantaloupe at convective hot air dryer.Drying experiments were conducted at the air temperatures of 40,50,60 and 70
C and the air speeds of 0.5,1 and l.5 m/s.Drying properties were including kinetic drying,effective moisture diffusivity(Deff)and specific energy consumption(SEC).The highest value of Deff obtained 9.76×10^-9,0.13×10^-9 and 9.97×10^-10 m^2/s for potato,garlic,and cantaloupe,respectively.The lowest value of SEC for potato,garlic,and cantaloupe were calculated 1.94
105,4.52
105 and 2.12
105 kJ/kg,respectively.Results revealed that the ANFIS model had the high ability to predict the Deff(R^2=0.9900),SEC(R^2=0.9917),moisture ratio(R^2=0.9974)and drying rate(R^2=0.9901)during drying.So ANFIS method had the high ability to evaluate all output as compared to ANNs method.