scholarly journals Thermal conductivity factor for beef of NOR and DFD grades at the subcryoscopic temperatures

2021 ◽  
Vol 6 (3) ◽  
pp. 285-290
Author(s):  
Yu. M. Berezovsky ◽  
I. A. Korolev ◽  
T. A. Sarantsev
Keyword(s):  
Thermal Conductivity ◽  
Food Products ◽  
Conveyor Belt ◽  
Calculation Error ◽  
Freezing And Thawing ◽  
Empirical Relationships ◽  
Food Freezing ◽  
Time Calculation ◽  
Ph Level ◽  
Water Holding

Thermal conductivity factor and specific isobaric heat capacity of food products are currently the most important parameters in the development of mathematical models for food freezing and thawing and in improving production technology. There is significant variance among the existing experimental data for the thermal conductivity factor in meat. Most of the modern calculated relationships are based on the nutritional approach, which favorably differs by the ability to calculate the thermophysical characteristics of any food products. However, the calculation error at the subcryoscopic temperatures may be 15% to 20%. The development of superchilling as a way of storing meat requires high accuracy of freezing time calculation, including vacuumpacked boneless meat. In the presented article, the authors investigated hydrogen index, cryoscopic temperature, frozen moisture proportion and thermal conductivity factor for beef M. longissimus dorsi samples of NOR and DFD grades. It was found that DFD beef is characterized by 10% to 12% higher values of thermal conductivity factor in comparison with NOR grade. Using the method of regression analysis, the authors developed empirical relationships for calculating the thermal conductivity factor of meat depending on its temperature and pH level. Unlike cryoscopic temperature and frozen moisture proportion, pH is easy to measure and may be easily used on a conveyor belt for more accurate assessment of meat thermophysical properties. With an increase in pH from 5.3 to 7, an increase in cryoscopic temperature is observed from minus 0.94 °C to minus 0.72 °C. It has been shown that one of the factors for the higher cryoscopic temperature and higher pH level of DFD beef is higher water-holding capacity with less strongly bound moisture.

scholarly journals EFEK PEMBEKUAN-PELELEHAN BERULANG TERHADAP MUTU SENSORI IKAN CAKALANG (Katsuwonus pelamis L)

2019 ◽  
Vol 7 (2) ◽  
pp. 32
Author(s):  
Sandra Jenspiten Tatontos ◽  
Silvana Dinaintang Harikedua ◽  
Eunike Louisje Mongi ◽  
Djuhria Wonggo ◽  
Lita ADY Montolalu ◽  
...  
Keyword(s):  
Sensory Quality ◽  
Protein Denaturation ◽  
Freezing And Thawing ◽  
Katsuwonus Pelamis ◽  
Fish Meat ◽  
Food Freezing ◽  
Thaw Cycle ◽  
Refrigerator Temperature ◽  
Water Holding

Fish is one of the perishable food, freezing technique is an effective method in storage fishery products. The process of freezing and thawing can also cause damage to fish meat such as the occurrence of protein denaturation which results in the loss of water holding capacity and influence the decrease in sensory quality (odor, texture, color). This study aims to determine the effect of the freez-thaw cycle on Skipjack sensory quality. Freezing for 24 hours at -24.2ºC freezer temperature and thawing for 24 hours at refrigerator temperature ± 2,4ºC. Freez-thaw is done repeatedly, 1 time, 2 times, 3 times and 4 times. The results of the study showed that the more freezing-thawing processes carried out, the more affected the sensory quality. The results of this study indicate that after 4 times the freez-thaw cycle treatment affects the sensory quality of skipjackKeyword: Freez-thaw cycle, sensory quality. Ikan adalah produk pangan yang mudah mengalami kemunduran mutu (perishable food), teknik pembekuan adalah metode pengolahan dan penyimpanan yang efektif untuk produk hasil perikanan. Proses pembekuan juga dapat menyebabkan kerusakan pada daging ikan seperti terjadinya denaturasi protein, penurunan mutu sensori (aroma, tekstur, warna). Penelitian ini bertujuan untuk mengetahui efek dari pembekuan dan pelelehan secara berulang terhadap kualitas sensori ikan cakalang. Pembekuan dilakukan selama 24 jam pada suhu freezer -24,2ºC dan pelelehan dilakukan selama 24 jam pada suhu lemari es ± 2,4ºC. alur pembekuan-pelelehan dilakukan secara berulang, 1 kali, 2 kali, 3 kali dan 4 kali. Hasil penelitian memperlihatkan bahwa semakin banyak proses pembekuan-pelelehan yang dilakukan maka nilai mutu sensori. Penelitian ini menunjukkan bahwa setelah 4 kali perlakuan pembekuan-pelelehan terhadap ikan cakalang terjadi penurunan pada penampakkan sensori.Kata kunci: Pembekuan-pelelehan berulang, mutu sensori.

scholarly journals Influence of Airflow Field on Food Freezing and Energy Consumption in Cold Storage

2018 ◽  
Vol 53 ◽  
pp. 01038
Author(s):  
Guiqiang Wang ◽  
Xiaohang Cheng ◽  
Zhiqiangè Kang ◽  
Guohui Feng
Keyword(s):  
Energy Consumption ◽  
Field Distribution ◽  
Cold Storage ◽  
Food Products ◽  
Lumped Parameter Model ◽  
Freezing Process ◽  
Load Factor ◽  
Freezing Time ◽  
Food Freezing ◽  
Airflow Field

Currently most food products are cooled and frozen in air-blast cold storage to prolong storage time. The airflow field distribution in storage has a great impact on the process of food freezing and energy cost by that. In this paper, a transient model of food freezing considering airflow field was developed to simulation the temperature profile of air and food products during freezing process. A lumped parameter model was used to predict the temperature and moisture profile of air, which connected all other components together, such as air coolers, food products, envelop enclosure and refrigeration system. A finite difference method was employed to model the heat transfer inside food products during freezing, where the mass transfer was neglected as the food products were wrapped with polystyrene films. Unit load factor method was applied to calculate the sensible heat refrigeration capacity and thus the total capacity of air coolers. The simulation was conducted on a large cold storage filled with large quantities of packaged food products. Results show that there are great differences in airflow field distribution at different locations in cold storage, which lead to spacial differences in freezing time required. Inappropriate set point of freezing time prolongs freezing process unnecessarily and leads to extra energy consumption. Operational mode of air coolers has a great impact on the total energy consumption, as they consume energy themselves and release equivalent heat into storage simultaneously.

Determination of Thermal Conductivity of Soils: A Need for Computing Heat Loss Through Buried Submarine Pipelines

1982 ◽  
Vol 22 (04) ◽  
pp. 558-562 ◽  
Author(s):  
P.C. Rawat ◽  
S.L. Agarwal
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Crude Oil ◽  
Rheological Properties ◽  
Heat Loss ◽  
Experimental Results ◽  
Dry Density ◽  
Empirical Relationships ◽  
Thermal Conductivities

Abstract An important parameter required for computing heat loss through buried submarine pipelines transporting crude oil is the thermal conductivity of soils. This paper describes an apparatus designed for determination of the thermal conductivity of soils at the desired moisture/ density condition in the laboratory under steady-state conditions. Experimental results on the three soils studied show that thermal conductivity increases as dry density increases at a constant moisture content and that it increases as water content increases at constant dry density. These results confirm the trends isolated earlier by Kersten. The experimental results are compared with the available empirical relationships. Kersten's relation is observed to predict the thermal conductivity of these soils reasonably. The predictions from Makowski and Mochlinski's relation (quoted by Szilas) are not good but improve if the sum of silt and clay fractions is treated as a clay fraction in the computation. Introduction Submarine pipelines are used extensively for transporting crude oil from offshore to other pipelines offshore or onshore. These pipelines usually are steel pipes covered with a coating of concrete. They often are buried some depth below the mudline. The rheological properties of different crude oils vary, and their viscosities increase with a decrease in temperature. Below some temperature, the liquid oil tends to gel. Therefore, for efficient transportation, the crude must be at a relatively high temperature so that it has a low viscosity. The temperature of the soil/water system surrounding a submarine pipeline is usually lower than that of oil. This temperature difference induces heat to flow from the oil to the environment, and the temperature of the oil decreases as it travels along the length of the pipeline. One must ensure that this temperature reduction does not exceed desirable limits dictated by the rheological properties of oil and by the imperatives of efficient economic properties of oil and by the imperatives of efficient economic transportation. Thus the analytical problem is to predict the temperature of crude in the pipeline some distance away from the input station. To do so, knowledge of the overall heat transfer coefficient for the pipeline is required, for which, in turn, it is necessary to know the thermal conductivities of the oil, the pipeline materials and its coating, and the soil. This paper presents thermal conductivities of soils determined in the laboratory under steady-state conditions and also presents a comparison of the test results of three soils with values determined from existing empirical relationships. Literature Review Heat moves spontaneously from higher to lower temperatures. In a completely dry porous body, transmission of heat can take place not only by conduction through the solid framework of the body and the air in the pores but also by convection and radiation between the walls of a pore and by macro- and microdistillation. In soils, however, it can be ascribed essentially to conduction, a molecular phenomenon that can be expressed in terms of experimentally determined coefficients of conductivity or resistivity, although these actually may include microdistillation and other mechanisms. SPEJ p. 558

scholarly journals WATER VAPOR PERMEABILITY OF POROUS MEDIA

1959 ◽  
Vol 37 (4) ◽  
pp. 413-416 ◽  
Author(s):  
William Woodside
Keyword(s):  
Thermal Conductivity ◽  
Porous Media ◽  
Water Vapor ◽  
Permeability Coefficient ◽  
Lightweight Concrete ◽  
Water Vapor Permeability ◽  
Vapor Permeability ◽  
Empirical Relationships ◽  
Glass Spheres ◽  
Cellular Concrete

Following the analogy between the laws of heat conduction and vapor diffusion, two theoretical expressions for the thermal conductivity of a composite medium are applied to the water vapor permeability coefficient of certain porous media. It is shown that both expressions reduce to a form very similar to the empirical relationships found by Penman and Edenholm for soils, glass spheres, charcoal, and cellular concrete. The calculation of the variation of water vapor permeability with density for a cellular lightweight concrete is illustrated.

scholarly journals Sensitivity of the results of modeling of seasonal ground freezing to selection of parameterization of the snow cover thermal conductivity

2019 ◽  
Vol 59 (1) ◽  
pp. 67-80 ◽  
Author(s):  
S. P. Pozdniakov ◽  
S. O. Grinevskyi ◽  
E. A. Dedulina ◽  
E. S. Koreko
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Snow Cover ◽  
Soil Profile ◽  
Average Density ◽  
Temperature Correction ◽  
Freezing And Thawing ◽  
Coupled Models ◽  
Seasonal Freezing ◽  
Effective Medium Model

The relationship between the results of calculations of the dynamics of the temperature regime of the in freezing and thawing soil profile with the heating effect of the snow cover is considered. To analyze this connection, two coupled models are used: the model of formation and degradation of snow cover in winter and the model of heat transfer and soil moisture transport in underlying vadoze zone profile. Parametrization of the influence of the snow cover, which at each calculated moment of time has the current average density and depth, on the dynamics of the temperatures of the soil profile is due to the use of its specific thermal resistance, which depends on its current depth and the thermal conductivity coefficient. The coefficient of thermal conductivity of the snow cover is related with its density using six different published empirical relationships. Modeling of heat transfer in freezing and thawing soil is carried out on the example of the field site for monitoring the thermal regime located on the territory of the Zvenigorod Biological Station of Moscow State University. It is shown that the well-known relationships give similar curves for the dynamics of the depth of seasonal freezing, including the degradation of the seasonal freezing layer in the spring period, with the same dynamics of the snow cover. However, the maximum penetration depth of the zero isotherm differs significantly for different snow conductivity-snow density relationships. The tested six relationships were divided into three groups. Minimal freezing is provided by the Sturm model and the effective medium model. The average and rather poorly differentiating freezing from each other is given by the Pavlov, Osokin et al. and Jordan relationships. The greatest value of the freezing depth is obtained with using Pavlov’s relationship with a temperature correction. 

scholarly journals Production of Denatured Whey Protein Concentrate at Various pHfrom Wastewater of Cheese Industry

2021 ◽  
Vol 41 (2) ◽  
pp. 161
Author(s):  
Robi Andoyo ◽  
Anindya Rahmana Fitri ◽  
Ratih Siswanina Putri ◽  
Efri Mardawati ◽  
Bambang Nurhadi ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Whey Protein ◽  
Functional Properties ◽  
Heat Treatment Condition ◽  
Whey Protein Concentrate ◽  
Protein Concentrate ◽  
Cheese Industry ◽  
Ph Level ◽  
Water Holding ◽  
Physicochemical And Functional Properties

Wastewater produced from cheese industry is rich in biological component such as whey protein, fat and lactose. Whey protein is the residual liquid of cheese making process with a high protein efficiency ratio. The wastewater source used in this study was whey liquid from cheese processing industry located at West Java, Indonesia. Conversion of soluble whey protein into whey protein microparticle is required to produce food with nutritional value that can be adjusted to the needs of the specific target with high digestibility and palatability. Whey protein was collected by separation technique through heat treatment at specific condition. This was done by changing the heat treatment condition and pH of the samples. Changing the pH of the samples before heat treatment affect the ionic strength of the whey protein hence, altering the properties of the concentrate. This study aims to produce whey protein concentrate heated at various pH level and to observe physicochemical and functional properties of the concentrates. The method used in this research was a descriptive method conducted on three treatments and two replications namely whey protein concentrate production in a pH condition 6.4; 6.65; and 7.0. The parameters observed were physicochemical and functional properties. Furthermore, the result showed that there were decrease in protein content, along with the increasing pH before heat treatment. Microstructure image (SEM) showed a finer particles with the increasing pH. Meanwhile, solubility of the rehydrated samples tends to increase along with the increasing pH. The measurement of functional properties of the samples showed that denatured whey protein produced at different pH before heat treatment have different water holding capacity and a tendency to form bonds between protein particles thereby increasing the viscosity value. These physicochemical and functional properties were suitable for denatured whey protein to be used as a texture controller in whey protein based-food production.

Weather resistance of CaSO4 ⋅ 1/2H2O-based sand-fixation material

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744084 ◽  
Author(s):  
Xin Liu ◽  
Shengnian Tie
Keyword(s):  
Compressive Strength ◽  
Wind Erosion ◽  
Water Resistance ◽  
Erosion Resistance ◽  
Field Tests ◽  
Northwest China ◽  
Freezing And Thawing ◽  
Weather Resistance ◽  
Freezing And Thawing Cycles ◽  
Water Holding

Searching for an economical and effective sand-fixing material and technology is of great importance in Northwest China. This paper described the use of a semihydrated gypsum-(CaSO4 ⋅ 1/2H2O-)based composite as a sand-fixing material. Its morphology and composition were characterized by SEM, and its water resistance, freezing–thawing resistance and wind erosion resistance were tested in the field. The results indicated that semihydrated gypsum-(CaSO4 ⋅ 1/2H2O-)based sand-fixing composite has good water resistance and water-holding capacity. Its strength is maintained at 1.42 MPa after 50 freezing and thawing cycles, and its wind erosion increases with increasing wind speed and slope. Its compressive strength starts to decrease after nine months of field tests with no change in appearance, but it still satisfies the requirements of fixation technology. This sand-fixing material should have wide application owing to its good weather resistance.

scholarly journals THE EFFECT OF CRYSTALLINITY ON THE THERMAL CONDUCTIVITY OF POLYMERS

2021 ◽  
Vol 25 (Special) ◽  
pp. 2-25-2-32
Author(s):  
Noor S. Zaki ◽  
◽  
Tawfeeq W. Salih ◽  
Keyword(s):  
Thermal Conductivity ◽  
High Density Polyethylene ◽  
Theoretical Work ◽  
Degree Of Crystallinity ◽  
Mathematical Function ◽  
Low Density ◽  
Empirical Relationships ◽  
Coefficient Of Thermal Conductivity ◽  
The Degree Of Crystallinity ◽  
Cooling Procedure

The aim of this research is investigating the direct effect of crystallinity of thermoplastic polymers on their thermal conductivity values. The study has included many materials, namely: polyoxymethylene (POM), high-density polyethylene (HDPE), low-density polypropylene (LDPE), polypropylene (PP), polyamide (PA) and polyethylene terephthalate (PET). The degrees of crystallinity ranged from high-values (60-70%), mid-values (30-40%) and low-values (10-20%). The work has done theoretically and experimentally. Theoretical work has used mathematical function extracted from reliable empirical relationships. The experimental work has included: manufacturing the specimens; specifying the cooling procedure in order to get the required degree of crystallinity; measuring the coefficient of thermal conductivity for different polymers at various conditions; and finally analyze the data and introduce the experiences obtained from the investigation. In general, theoretical values as well as experimental data were both behave similarly with respect to the variation of thermal conductivity with the degree of crystallinity. The results show that by increasing the degree of crystallinity the thermal conductivity of the polymer has increased by 10-20%.

scholarly journals THERMAL ANALYSIS OF FOOD PRODUCTS USING DIFFERENTIAL SCANNING CALORIMETRY (DSC)

2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Radoslav Grujić ◽  
Danica Savanović
Keyword(s):  
Differential Scanning Calorimetry ◽  
Thermal Properties ◽  
Food Products ◽  
Freezing And Thawing ◽  
Frozen Foods ◽  
Scanning Calorimetry ◽  
Scanning Rate ◽  
Heat Treated ◽  
Treated Apple ◽  
Freezing Storage

Intensity of changes during the freezing storage of frozen foods, depends on several factors. Changes of foods during freezing and thawing can be rapidly determined by scanning calorimetry (DSC). The aim of this study was to test the influence of scanning rate on the thermal properties of previously heat-treated food products (boiled apple), using the differential scanning calorimetry method. By increasing the scanning rate, significant changes (p0.05) Tcon from -14,20 °C (rate 5 °C/min) to -15.57 °C (rate 15 °C/min) and Tcend (from -17.53 °C to -22.90 °C) were determined, and ΔTc increased from 3.33 °C to 7.33 °C. At the same time, the width of the melting temperature interval (ΔTm) increased from 7.80 °C to 12.87 °C. The glass transition temperature (Tgmid) ranged from -7.15 °C (rate 5 °C/min) to -6.60 °C (rate 15 °C/min). Based on the obtained results, it was found that the scanning rate during the DSC determination statistically significantly (p0.05) influenced the measured values of the thermal properties of the tested heat-treated apple samples.

scholarly journals Brief communication: Evaluation of multiple empirical, density-dependent snow conductivity relationships at East Antarctica

2021 ◽  
Author(s):  
Minghu Ding ◽  
Tong Zhang ◽  
Diyi Yang ◽  
Ian Allison ◽  
Tingfeng Dou ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Estimation Method ◽  
East Antarctica ◽  
Empirical Relationships ◽  
One Dimensional ◽  
Density Dependent ◽  
Empirical Density ◽  
The Mean ◽  
Weather Stations ◽  
Communication Evaluation

Abstract. Nine density-dependent empirical thermal conductivity relationships for firn were compared against data from three Automatic Weather Stations at climatically-different East Antarctica sites (Dome A, Eagle and LGB69). The empirical relationships were validated using a vertical, one-dimensional thermal diffusion model and a phase-change based firn diffusivity estimation method. The best relationships for these East Antarctica sites were identified by comparing the modeled and observed firn temperature at the depth of 1 m and 3 m, and from the mean heat conductivities over two depth intervals (1–3 m and 3–10 m). Among the nine relationships, that proposed by Calonne et al. (2011) appears to have the best performance. This study provides useful reference for firn thermal conductivity parameterizations in land modeling or snow-air interaction studies on the Antarctica Ice Sheet.

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