Heat pump use in milk pasteurization: an energy analysis

This study investigates the applicability of heat pumps to milk pasteurization for cheese production and to compare the results with classical pasteurization systems. The experiments are conducted in a liquid‐to‐liquid vapour compression heat pump system and a milk‐to‐milk plate heat exchanger is used as an economizer. The experiments are also conducted in a double jacket boiler system and a plate pasteurization system, which are classical milk pasteurization systems. The results for the three systems are compared and the advantages/disadvantages of using heat pump for milk pasteurization instead of classical systems are determined. It is found that the heat pump consumes less energy than the other two classical systems. Copyright © 2004 John Wiley & Sons, Ltd.     

Chemical and sensory quality changes of fish fingers,made from mirror carp (Cyprinus carpio L., 1758), during frozen storage (−18 °C)

The effects of frozen storage at −18 °C on the chemical and sensory qualities of fish fingers produced from unwashed and washed mirror carp (Cyprinus carpio) mince were investigated. The amounts of moisture, crude protein, lipid, crude ash, ω3 polyunsaturated fatty acids (PUFA ω3), and ω6 polyunsaturated fatty acids (PUFA ω6) in fish fingers produced from unwashed mince (UWF) were found to be 68.50%, 15.5%, 6.00%, 2.20% 2.31%, and 55.2%, respectively, while they were found to be 70.23%, 10.8%, 2.14%, 1.80%, 2.28%, and 54.6%, respectively, in carp fingers produced from washed mince (WF). The thiobarbituric acid value (TBA, mg malonaldehyde/kg) was found to be significantly higher in mince of WF than in mince of UWF and increased significantly during frozen storage in both the mince of UWF and WF (p < 0.05). A significant decrease in pH was obtained throughout the washing treatment (p < 0.05). There were no significant differences of pH in either the mince of UWF or WF between the beginning and end of the storage periods (p > 0.05), whereas a sharp increase was observed in the fourth month in both groups. The protein solubilities of the mince of both UWF and WF decreased significantly throughout the storage periods (p < 0.05). Sensory parameters of colour, odour, flavour, and general acceptability for both groups decreased during the frozen storage period (p < 0.05) but were still within acceptable limits. It was also concluded that mirror carp was a good source for fish fingers and that product could be stored for five months in a frozen state without undesirable changes of sensory and chemical qualities.     

Profiles of the fatty acids in the plasma membrane of human brain tumors

The ionic channels and signal transduction pathways underlying the 5-hydroxytryptamine (5-HT)-induced hyperpolarization in neurons of the rat dorsolateral septal nucleus (DLSN) were examined by using intracellular and voltage-clamp recording techniques. Application of 5-HT (1-50 microM) caused a hyperpolarizing response associated with a decreased membrane resistance in DLSN neurons. The hyperpolarization induced by 5-HT was blocked by Ba2+ (1 mM) but not by tetraethylammonium (TEA, 3 mM), glibenclamide (100 microM) and extracellular Cs+ (2 mM). 8-Hydroxy-di-n-propylamino tetralin (8-OH-DPAT; 3 microM), a selective agonist for the 5-HT1A receptor, mimicked 5-HT in producing the hyperpolarization. The 5-HT hyperpolarization was blocked by NAN-190 (5 microM), a 5-HT1A receptor antagonist. CP93129 (100 microM), a 5-HT1B receptor agonist, and L-694-247 (100 microM), a 5-HT1B/1D receptor agonist, also produced hyperpolarizing responses. The order of agonist potency was 8-OH-DPAT > CP93129 > or = L-694-247. (+/-)-2,5-Dimethoxy-4-iodoamphetamine hydrochloride (DOI, 100 microM), a 5-HT2 receptor agonist, and RS67333 (100 microM), a 5-HT4 receptor agonist, caused no hyperpolarizing response. The voltage-clamp study showed that 5-HT caused an outward current (I5-HT) in a concentration-dependent manner. I5-HT was associated with an increased membrane conductance. I5-HT reversed the polarity at the equilibrium potential for K+ calculated by the Nernst equation. I5-HT showed inward rectification at membrane potentials more negative than-70 mV. Ba2+ (100 microM) blocked the inward rectifier K+ current induced by 5-HT. I5-HT was irreversibly depressed by intracellular application of guanosine 5'-O-(3-thiotriphosphate)(GTP-gamma S) but not by guanosine 5'-O-(2-thiodiphosphate) (GDP beta S). These results suggest that in rat DLSN neurons activation of 5-HT1A receptors causes a hyperpolarizing response by activating mainly the inward rectifier K+ channels through a GTP-binding protein.     

The capability of rosemary extract in preventing oxidation of fish lipid

The effects of rosemary extract at different levels (%1, R1, and %2, R2) on the quality of vacuum‐packed sardine in terms of sensory, biochemical (thiobarbituric acid, total volatile basic nitrogen, peroxide value and free fatty acids) and microbiological analyses (total viable counts) were investigated. Fish were filleted and divided into three groups. First group was used as the control (C) without rosemary extract, second group was treated with 1% rosemary extracts (10 g L^?1) for 2 min (R1), and the third was treated with 2% rosemary extracts (20 g L^?1) for 2 min (R2). Thirty fillets per litre were used. After that, all groups were vacuum‐packed in polyethylene bags. The samples were stored in the refrigerator condition (4 ± 1 °C) over the storage period of 20 days. The results showed that the use of rosemary extract improved the sensory quality of both raw and cooked sardine, most preferably sardine treated with 1% of rosemary. Biochemical analysis showed that the use of 2% of rosemary extract were found to be most effective (P < 0.05) in controlling the rate of lipid oxidation.     

Quantifying submarine groundwater discharge in the coastal zone via multiple methods

Submarine groundwater discharge (SGD) is now recognized as an important pathway between land and sea. As such, this flow may contribute to the biogeochemical and other marine budgets of near-shore waters. These discharges typically display significant spatial and temporal variability making assessments difficult. Groundwater seepage is patchy, diffuse, temporally variable, and may involve multiple aquifers. Thus, the measurement of its magnitude and associated chemical fluxes is a challenging enterprise. A joint project of UNESCO and the International Atomic Energy Agency (IAEA) has examined several methods of SGD assessment and carried out a series of five intercomparison experiments in different hydrogeologic environments (coastal plain, karst, glacial till, fractured crystalline rock, and volcanic terrains). This report reviews the scientific and management significance of SGD, measurement approaches, and the results of the intercomparison experiments. We conclude that while the process is essentially ubiquitous in coastal areas, the assessment of its magnitude at any one location is subject to enough variability that measurements should be made by a variety of techniques and over large enough spatial and temporal scales to capture the majority of these changing conditions. We feel that all the measurement techniques described here are valid although they each have their own advantages and disadvantages. It is recommended that multiple approaches be applied whenever possible. In addition, a continuing effort is required in order to capture long-period tidal fluctuations, storm effects, and seasonal variations.     

Non-destructive monitoring of fiber orientation using AC-IS: An industrial-scale application

A comprehensive study has been undertaken to investigate the ability of AC-impedance spectroscopy (AC-IS) to non-destructively monitor the fiber dispersion of conductive fiber-reinforced cement-based materials. Previous work showed that AC-IS effectively monitors various fiber dispersion issues in lab-scale steel fiber-reinforced specimens. In this part of the study, AC-IS was used to study fiber orientation in an industrial-scale pre-cast concrete beam. A conventional method-image analysis (IA)-was used to verify the results of AC-IS measurements. The results of AC-IS and IA were found to match very well in experimental uncertainty. Splitting tensile tests and bending tests were conducted on the parts of the beam to study the effects of fiber orientation on the mechanical performance. The results of the mechanical tests also confirmed the results of AC-IS with splitting tensile strengths increasing as the alignment of fibers increased.     

Zeolite-filled regenerated cellulose membranes for pervaporative dehydration of glycerol

Regenerated cellulosic membranes were prepared by dissolving linter pulp in N-methylmorpholine-N-oxide (NMMO) solution with four different cellulose concentrations (3, 5, 8 and 10 wt. % cellulose) at three different coagulation temperatures (5, 25 and 50 °C). Zeolite 13 X with an average particle size of 310 nm and Zeolite 4A with an average particle size of 270 nm were added during dissolution. The resulting composite membranes were characterized by Fourier Transform Infrared (FTIR), Thermogravimetric Analyzer (TGA), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). Pervaporation performances of the zeolite filled and unfilled regenerated cellulose membranes were tested for glycerol/water mixture.Chemically and thermally stable regenerated cellulose membranes could be prepared by using submicron sized zeolite loading maximum of 50%. The SEM pictures showed that the zeolite particles in polymer phase were uniformly distributed. It was concluded that the zeolite filled regenerated cellulose membranes have minimum degradation during membrane preparation obtained from NMMO and could be used as pervaporation membranes. At 30 °C and with the addition of 20 wt. % Zeolite 13 X to the cellulose membrane, the flux and selectivity was obtained 65 gm⁻²h⁻¹ and 1681 for 90 wt% glycerol aqueous solution, respectively.     

Theoretical and experimental examination of air conditioner heat exchangers

Heat and mass transfer characteristics of finned-tube heat exchangers under dehumidifying and dry conditions are examined both theoretically and experimentally in the present study. Six types of heat exchangers were tested on an experimental facility. It was determined that there is less than 1 °C of outlet air temperature difference between computer program results and literature for water and R22 as a refrigerant. The outlet air specific humidity difference between them is less than 6.44% for water and 9% for R22. According to the experimental results, louvers on fin cause an increase of airside heat transfer coefficient of about 50% or 100%.     

Frost formation on fin-and-tube heat exchangers. Part I—Modeling of frost formation on fin-and-tube heat exchangers

In this study, the heat and mass transfer characteristics of heat exchangers during frost formation process are analyzed numerically. Unsteady heat and mass transfer coefficients of the air side, heat transfer coefficient of the refrigerant side, air-frost layer interface temperature, the surface efficiency of the heat exchanger and the mass flow rate of the frost accumulated on the heat exchanger surface are calculated. The total conductivity (UA) and pressure drop of the heat exchanger are reported for different air inlet temperature, relative humidity, air mass flow rate and the refrigerant temperature.