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| 3. |
- Gong, Shengjie, et al.
(author)
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An experimental study on the effect of liquid film thickness on bubble dynamics
- 2013
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In: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 51:1-2, s. 459-467
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Journal article (peer-reviewed)abstract
- Experiments were conducted to investigate the boiling phenomenon in various liquid layers on a silicon heater surface with an artificial cavity. Deionized water is employed as working liquid. The emphasis is placed on how the liquid layer thickness affects bubble behaviour and liquid layer integrity for nucleate boiling under the isolated bubble regime. The experimental results show that for boiling in a liquid layer of ∼7.5 mm, the bubble dynamics reproduce the typical pool boiling characteristics with the averaged maximum diameter of 3.2 mm for the isolated bubbles growing on the cavity. As the water layer thickness decreases to the level comparable with the bubble departure diameter, the bubble is found to remain on the heater surface for an extended period, with a dry spot forming under the bubble but rewetted after the bubble rupture occurs. Further reducing the liquid layer thickness, an irreversible dry spot appears, suggesting a minimum rewettable thickness ranging from 1.2 mm to 1.9 mm corresponding to heat flux of 26 kW/m2 to 52 kW/m2. The void measured in the cavity confirms that it is dry inside the artificial cavity at high heat flux.
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| 4. |
- Johansson, Monika, et al.
(author)
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Casein Breakdown in Bovine Milk by a Field Strain of Staphylococcus aureus
- 2013
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In: Journal of Food Protection. - 0362-028X. ; 76, s. 1638-1642
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Journal article (peer-reviewed)abstract
- The objectives of this study were to establish the proteolytic effects of Staphylococcus aureus during mastitis on economically important milk proteins. Concentrations of milk proteins were determined by capillary electrophoresis in an experimental model using a field strain of S. aureus. The pathogen was inoculated into bacteria-free control milk to imitate proteolysis caused by the pathogen in the mammary gland between milkings. Milk content of caseins (CN) alpha(S1), alpha(S2), kappa, beta(A1), and beta(A2) and whey proteins alpha-lactalbumin and beta-lactoglobulin were analyzed initially and after 6 h of incubation. After 6 h, the overall CN content was significantly reduced (21%) in milk inoculated with S. aureus compared with the bacteria-free control milk. S. aureus significantly lowered concentration of alpha(S1)-CN (2.5%), beta(A1)-CN (3%), and beta(A2)-CN (5%). S. aureus also hydrolyzed kappa-CN into para-kappa-CN, with significant reduction of kappa-CN (7.4%) as a consequence.
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| 5. |
- Li, Liangxing, et al.
(author)
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Experimental Study of Two-Phase Flow Regime and Pressure Drop in a Particulate Bed Packed with Multidiameter Particles
- 2012
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In: Nuclear Technology. - : American Nuclear Society. - 0029-5450 .- 1943-7471. ; 177:1, s. 107-118
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Journal article (peer-reviewed)abstract
- This paper documents an experimental study on two-phase flow regimes and frictional pressure drop characteristics in a particulate (porous) bed packed with multidiameter (1.5-, 3-, and 6-mm) glass spheres. The experimental results provide new data to validate/develop hydrodynamic models for coolability analysis of debris beds formed in fuel-coolant interactions during a postulated severe accident. The POMECO-FL test facility is employed to perform the experiment, with the spheres packed in a test section of 90 mm diameter and 635 mm height. The pressure drops are measured for air/water two-phase flow through the packed bed, and flow patterns are obtained by means of visual observations. Meanwhile, local void fraction in the center of the bed is measured by a microconductive probe.The experimental results show that the frictional pressure drop of single-phase flow through the bed can be predicted by the Ergun equation, if the area mean diameter of the particles is chosen in the calculation. Given the so-determined effective particle diameter, the estimation of the Reed model for two-phase flow pressure gradient in the bed has a good agreement with the experimental data. The characteristics of the local void fraction can be used to predict flow pattern and mean void fraction. It is observed that slug flow prevails when the mean void fraction is <0.5, whereas annular flow dominates after the mean void fraction is >0.7. If the effective particle diameter is further used as an influential parameter in flow pattern identification, the observed flow regimes of two-phase flow in porous media are well predicted by the existing flow pattern map.
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| 6. |
- Li, Shengjie, et al.
(author)
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Determination of biogenic amines in aerobically stored beef using high-performance thin-layer chromatography densitometry
- 2016
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In: Acta Agriculturae Scandinavica, Section A - Animal Science. - : Informa UK Limited. - 0906-4702 .- 1651-1972. ; 66, s. 199-205
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Journal article (peer-reviewed)abstract
- The aim of this study was to develop a high-performance thin-layer chromatography densitometry method to simultaneously evaluate levels of different biogenic amines (BAs) in beef stored aerobically at 4 degrees C. Steaks from M. longissimus thoracis et lumborum muscles were overwrapped with polyvinyl chloride film and stored for 0, 4, 7, and 10 days. For this purpose, the solvent system and pH for the derivatization of BAs with dansyl chloride were optimized. Moreover, this method was also validated for linearity, limits of detection and quantification, precision, and recovery. As found using this method in beef samples, spermine content decreased significantly after 7 days of storage, and tyramine and cadaverine were not detected until day 10.
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| 7. |
- Li, Shengjie, et al.
(author)
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Feeding steam-pelleted rapeseed affects expression of genes involved in hepatic lipid metabolism and fatty acid composition of chicken meat
- 2017
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In: Poultry Science. - : Elsevier BV. - 0032-5791 .- 1525-3171. ; 96, s. 2965-2974
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Journal article (peer-reviewed)abstract
- This study investigated the dietary effect of steam-pelleted rapeseed (RS) diets with different inclusion levels on the fatty acid composition of chicken meat and the expression of lipid metabolism-related genes in the liver. Experimental diets included 6 different wheat-soybean meal based diets either in nonpelleted or steam-pelleted form supplemented with 80, 160, and 240 g RS/kg feed and one nonpelleted wheat-soybean meal based diet without RS supplementation as the control. These diets were fed to newly hatched broiler chickens (Ross 308) for 34 days. Compared to the control diet, steam-pelleted diets containing 160 or 240 g/kg RS significantly increased the content of omega-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA) in the breast and drumstick, while their meat yields were not affected. Moreover, the mRNA levels of fatty acid desaturase 1 (FADS1) and acyl-coenzyme A oxidase 1 (ACOX1) in their livers increased. Therefore, steam-pelleted diets with 160 or 240 g/kg RS can be used to increase the n-3 LC-PUFA content in chicken meat without compromising meat yield.
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| 8. |
- Li, Shengjie, et al.
(author)
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Inter-relationships between the metrics of instrumental meat color and microbial growth during aerobic storage of beef at 4°C
- 2015
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In: Acta agriculturae Scandinavica. Section A, Animal science. - : Informa UK Limited. - 0906-4702 .- 1651-1972. ; 65:2, s. 97-106
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Journal article (peer-reviewed)abstract
- The objective of this study was to investigate the inter-relationships between changes in beef color and microbial growth when steaks from longissimus thoracis et lumborum muscles were overwrapped with polyvinyl chloride film and stored at 4°C. At day 0, 4, 7 and 10 instrumental color (CIE L*, a*, b* and spectral scans) and microbial counts were measured. Bacterial communities were characterized through Terminal Restriction Fragment Length Polymorphism analysis. Both meat discoloration and microbial spoilage occurred at day 10. Total viable count, Enterobacteriaceae count and the relative abundance of Pseudomonas spp. and Acinetobacter spp. were significantly correlated with color metrics associated with discoloration. These findings indicate that meat discoloration and microbial growth may not be totally independent effects and changes in a*, Chroma and hue angle may be an indicator of meat spoilage under this specific storage condition. Meanwhile, Enterobacteriaceae and aerobic bacteria might play important roles in meat discoloration.
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| 9. |
- Li, Shengjie
(author)
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Quality of muscle foods : effects of feed and storage time
- 2016
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Doctoral thesis (other academic/artistic)abstract
- The overall aim of this thesis was to investigate the effects of feed and storage time on meat quality. To study the effect of feed, chicken were fed seven steam-pelleted or nonpelleted rapeseed (RS) diets with different RS inclusion levels (0, 80, 160, and 240 g/kg) for 34 days, and the dietary effects on meat yield, fatty acid composition in meat, and the expression of lipid metabolism-related genes in liver were determined. Feeding with steam-pelleted diets with high inclusion of RS (160 or 240 g/kg) significantly increased the content of n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA) in meat, without compromising the meat yield and total fatty acid content. The increased intake of α-linolenic acid enabled higher conversion into n-3 LC-PUFA. Therefore, feeding broiler chicken steam-pelleted diet with high RS inclusion can be a feasible strategy to increase human intake of n-3 LC-PUFA without compromising meat yield. The effect of storage time on meat color, microbial growth, and lipid oxidation was studied on beef steaks from Longissimus thoracis et lumborum muscles overwrapped with polyvinyl chloride (PVC) film and stored at 4°C for 0, 4, 7, and 10 days. Microbial spoilage of beef occurred at day 10 as indicated by the total viable count exceeding the threshold of 7 log10 CFU/cm². Pseudomonas spp. and Brochothrix spp. were the prevailing bacteria species when meat was spoiled. Moreover, Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis showed the successive changes in the incidences of different bacteria over time. At day 10, the a* and Chroma decreased and hue angle increased significantly, indicating meat discoloration. Concentrations of spermine, tyramine, and cadaverine were found to be potential spoilage indicators of meat freshness. Lipid oxidation occurred only slightly, which could be attributed to the high content of α-tocopherol in meat. In contrast, the degree of lipid lipolysis increased with storage time as reflected by the increase in the relative content of free fatty acids and decrease in relative content of triacylglycerols.
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| 10. |
- Vidanarachchi, Janak, et al.
(author)
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Short communication: Lipolytic activity on milk fat by Staphylococcus aureus and Streptococcus agalactiae strains commonly isolated in Swedish dairy herds
- 2015
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In: Journal of Dairy Science. - : American Dairy Science Association. - 0022-0302 .- 1525-3198. ; 98, s. 8560-8564
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Journal article (peer-reviewed)abstract
- The objective of this study was to determine the lipolytic activity on milk fat of 2 bovine mastitis pathogens; that is, Staphylococcus aureus and Streptococcus agalactiae. The lipolytic activity was determined by 2 different techniques, that is, thin-layer chromatography and an extraction-titration method, in an experimental model using the most commonly occurring field strains of the 2 mastitic bacteria isolated from Swedish dairy farms. The microorganisms were inoculated into bacteria-free control milk and incubated at 37 degrees C to reflect physiological temperatures in the mammary gland. Levels of free fatty acids (FFA) were analyzed at time of inoculation (t = 0) and after 2 and 6 h of incubation, showing significant increase in FFA levels. After 2 h the FFA content had increased by approximately 40% in milk samples inoculated with Staph. aureus and Strep. agalactiae, and at 6 h the pathogens had increased FFA levels by 47% compared with the bacteria-free control milk. Changes in lipid composition compared with the bacteria-free control were investigated at 2 and 6 h of incubation. Diacylglycerols, triacylglycerols, and phospholipids increased significantly after 6 h incubation with the mastitis bacteria, whereas cholesterol and sterol esters decreased. Our results suggest that during mammary infections with Staph. aureus and Strep. agalactiae, the action of lipases originating from the mastitis pathogens will contribute significantly to milk fat lipolysis and thus to raw milk deterioration.
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