Deep-freezing Process Research Articles

Application of a Cascade Refrigeration System for Storage of Hibiscus Tea (A Zobo Drink) for Human Consumption

Since hibiscus tea is inexpensive, healthful, and has many nutritional benefits, individuals from various socioeconomic backgrounds frequently drink it. The main drawback of its large-scale manufacture is its short shelf life if not adequately chilled. In order to extend the shelf life of flavor-infused Zobo tea and conserve energy for mass production, the paper assesses the sensory properties of the tea in a cascade freezer and how much energy a convectional and cascade refrigeration system used. Within 120 minutes, a prepared hibiscus tea was frozen and kept at -15 0C for four days. After evaluation, the product's sensory quality was found to be suitable for ingestion. Over 72 hours, the natural flavor, color, and taste of Zobo drinks did not change. The cascade freezer only required 3 kg of fuel for two hours of operation as opposed to 7.5 kg of gasoline for six hours of operation for the LG freezer. The quick deep-freezing process reduced fuel expenditures while preserving the product's short shelf life. The energy used by the cascade freezer was 1600 MJ at a cost of #24000 per month, as opposed to a total of 11200 MJ at a cost of #204000 per month. The cascade refrigerator saved 100.4 GJ of energy annually at a cost of #218600. The machine's effectiveness and energy efficiency were rated at 75%. The outcome has improved the cold storage supply chain for Zobo products for usage in emerging and developing nations on a commercial basis and saved energy.

The Effect of Ti-6Al-4V Alloy Surface Structure on the Adhesion and Morphology of Unidirectional Freeze-Coated Gelatin

The modification of a metal implant surface with a biomimetic coating of bone-like anisotropic and graded porosity structures to improve its biological anchorage with the surrounding bone tissue at implanting, is still a high challenge. In this paper, we present an innovative way of a gelatin (GEL) dip-coating on Ti-6Al-4V substrates of different square-net surface textures by the unidirectional deep-freezing process at simultaneous cross-linking using carbodiimide chemistry. Different concentrations of GEL solution were used to study the changes in morphology, density, and mechanical properties of the coatings. In addition, the surface free energy and polarity of Ti-6Al-4V substrate surfaces and GEL solutions have been evaluated to assess the wetting properties at the substrate interfaces, and to describe the adhesion of GEL macromolecules with their surfaces, being supported by mechanical pull-out testing. The results indicate that the coating’s morphology depends primarily on the Ti-6Al-4V substrate’s surface texture and second, on the concentration of GEL, which further influences their adhesion properties, orientation, morphological arrangement, as well as compression strength. The substrate with a 300 × 300 μm2 texture resulted in a highly adhered GEL coating with ≥80% porosity, interconnected and well-aligned pores of 75–200 μm, required to stimulate the bone ingrowth, mechanically and histologically.

Experimental investigation on a thermochemical sorption refrigeration prototype using EG/SrCl2–NH3 working pair

Heat-powered thermochemical sorption refrigeration is a promising technology due to its distinct advantage of energy-saving and the close coincidence of cooling demands with the available solar thermal energy. In this paper, an advanced heat-powered thermochemical sorption refrigeration prototype using SrCl2/NH3 working pair is developed for air-conditioning and deep-freezing process with the utilization of low-grade heat. Expanded graphite (EG) is used as porous matrix to enhance the heat and mass transfer of strontium chloride by preparing EG/SrCl2 composite sorbent. Experimental results showed that the proposed refrigeration prototype can produce the cooling capacity with a refrigeration temperature from 5 to −15 °C by effectively utilizing thermal energy with a temperature below 100 °C. The system COP varies between 0.13 and 0.22 and the SCP ranges from 115 to 185 W kg−1 at the heat sink temperature of 25 °C and the global conversion reaches about 0.42. At the constant heat source temperature, the lower heat sink temperature contributes to the higher global conversion of reactive salt. The sorption reaction platforms of SrCl2/NH3 working pair corresponding to different evaporation temperatures are analyzed during the adsorption–evaporation phase. Potential development is analyzed and proposed for further improving system COP by reducing the mass ratio of metal and reactive salt in the solid–gas reactor and enhancing the global conversion of reactive salt as much as possible with the optimization construction of the reactor and better performance of heat and mass transfer of composite sorbent.

Development of Methods for Immobilization and Usages of Immobilized Recombinant Bioluminescent Strain, Pseudomonas Putida Mt-2 KG1206, Stored by Deep-Freezing

Deep-freezing process can be used practically for environmental monitoring. However, for the organism to be useful in environmental applications, the strain of bacteria exhibits a high intensity of activity following reconstitution after deep-freezing. An overall protocol for immobilization and reconstitution of recombinant bioluminescent bacteria, preserved by deep-freezing was investigated for future biomonitoring. Tested strain KG1206 has ability to produce bioluminescence in the presence of toluene analogs and those intermediates. Immobilization using glass beads with subcultured cells showed better results than other conditions, such as alginate beads or centrifuged cell pellets. Beads number, thawing time, and amount of reconstitution solution influence on bioluminescence activity. Among tested conditions, followings were appeared as optimum conditions: working volume 15 mL of serum vials, approximately 20-30 glass beads per vial, 3 h thawing time, and 2-5 mL reconstitution solution. Potassium nitrate (KNO3) greatly stimulates the low bioluminescence activity of immobilized strain, preserved by deep freezing, in the range of 2.5 to 21 times of untreated one.

Effect of post-thaw thermal resistance test on motility, membrane integrity and migration capacity of sperm in Gir bulls

Incubation test assesses the livability of spermatozoa in female reproductive tract and thereby the longevity of the sperms. Indirectly, it assesses the freezing injuries occurred to sperms during the deep freezing process. The period spent after thawing and before insemination may affect the quality and fertility of post-thaw semen. The frozen semen was thawed at 37°C for 30 sec and taken into a small sugar tube and incubated in the water-bath at 37°C for 0 h, 15 min, 30 min, 45 min and 60 h and per cent post-thaw motility (PTM%), hypo-osmotic swelling test (HOST%) and cervical mucus penetration test (CMPT – mm) were carried out. The PTM declined from 54.33±1.18% at 0 h to 53.00±1.17% – 15 min, 47.33±1.08% - 30 min, 43.33±1.05% - 45 min and 35.67±1.27% at 60 min. HOST reduced from 52.53±1.53% at 0 h to 51.07±1.45%- 15 min, 42.67±1.82%- 30 min, 33.80±2.36%- 45 min and 23.60±1.10% at 60 min. Similarly, CMPT reduced from 28.00±1.23 mm at 0 h to 8.27±0.56 mm at 60 min. The overall post-thaw motility, HOST and CMPT at 0 h and 15 min were significantly higher than 30 min, 45 min and 60 min in Gir bulls. Post-thaw motility, hypo-osmotic swelling test and cervical mucus penetration test remain unaffected up to 15 min post-thaw incubation while there is significant decline in at 30, 45 and 60 min, which indicated that increasing post-thaw incubation duration affects post-thaw motility, cell membrane permeability and cervical mucus penetration ability of spermatozoa which may affect fertility.

Thermographic analysis of leaf water and energy information of Japanese spindle and glossy privet trees in low temperature environment

Thermography has been used in many fields to perform non-invasive temperature measurements of natural objects. In this paper, thermography was used to determine the temperature of leaves, stems and branch kerfs of Japanese spindle (Euonymus japonicus Thunb.) and glossy privet (Ligustrum lucidum Ait.) in the city of Jinan in China during winter. The temperatures of the leaves, stems and branch kerfs were monitored as the temperature decreased after the sample was subjected to hand heating or after the branch was cut. Differences in the specific heats and the latent heats of the leaves, branches and stems with different water contents and transpiration capacities were confirmed. The significant temperature difference obtained after hand heating between different leaf sections with varied water contents made it easy to obtain the thermal images, which were clear and exhibited reduced systematic errors. After hand heating, a significantly higher temperature was found at the major vein system of both Japanese spindle and glossy privet. This increased temperature difference made it possible to detect the water and the thermal state of these leaves. Therefore, it was possible to detect scorched area of the leaves, the twig dieback and the sap warming phenomenon in the leaves using thermography. In addition, the leaf bending phenomenon observed in Japanese spindle leaves during the deep freezing process indicates that the leaf scorch symptoms result from water stress and a lack of sap warming.

Application of stimulating agents on the immobilized bioluminescence strain Pseudomonas putida mt-2 KG1206, preserved by deep-freezing, for the convenient biomonitoring

Abstract This study was conducted to develop methods for the application of an immobilized bioluminescence strain (KG1206), preserved by deep-freezing (DF), for the monitoring of contaminated environments. The immobilized cells, preserved by DF, required approximately 2 hr for reconstitution of their activity. A large reduction in bioluminescence was observed due to the DF process; 0.07-0.58 times that of the non deep-frozen (NDF) immobilized strain. The decreased bioluminescence activity induced by the DF process was enhanced by the stimulants, sodium lactate (SL) and KNO 3. However, regardless of the inducer chemical tested, the immobilized strain modified with KNO 3 consistently produced greater bioluminescence than that treated with SL, in the range of 3.0-10.7 (avg. 6.7 ± 3.69) and 1.2-4.2 (avg. 2.4 ± 1.47) times that of control, respectively. All KNO 3 treatments of contaminated groundwater samples also resulted in an increase in bioluminescence activity, but the rate of stimulation varied for each sample. Also, no strong linear correlation was observed between the bioluminescence and the total concentration of an inducer, which may related to the complex characteristics of the environmental samples. Overall, the results demonstrated the ability of immobilized genetically engineered bacteria, preserved by DF, to measure a specific group of environmental contaminants using a stimulating agent (KNO 3), suggesting the potential for its preliminary application in a field-ready bioassay.

Application of the SAFES (systematic approach to food engineering systems) methodology to strawberry freezing process

SAFES methodology has been applied in strawberry freezing process using data from references. Three cases of freezing have been studied. All of them start from the refrigerated temperature ( T c) and there is a first stage of cooling until the initial freezing temperature ( T m) is reached. However, the changes of components depend on the temperature reached and the rate of freezing. Case 1 studies the decrease of temperature from T m until the first layers of cells reach −18 °C, since this is the typical storage temperature in consumer’s freezer. In case 2, strawberries are frozen at the maximally cryoconcentrated temperature ( T m ′ ) of the matrix and then down to −100 °C. In case 3, a deep freezing process decreases the temperature of strawberries down to −196 °C. The last two cases are below the temperature of glass transition of strawberry (−51.3 °C) and therefore they have higher stability than in case 1. By means of this methodology it is possible to follow and predict the critical points (appearance or disappearance of components or phases) of the process to prevent quality loss. Components, phases and aggregation systems can also be analysed. Moreover, transport phenomena, chemical reaction and transition can actually be described. It has been demonstrated that SAFES methodology can describe the behaviour of strawberry freezing by using composition data, state diagrams and thermodynamic parameters. Nevertheless, to get better results more information about kinetic data related to freezing process would be required.

Design of a thermochemical process for deep freezing using solar low-grade heat

A deep-freezing process has been designed and experimented to cool a cold box down to about −30 °C using only low-grade heat produced by simple flat plate solar collectors operating at 70 °C. The original process involves two cascaded thermochemical systems using BaCl 2 salt reacting with ammonia. It works discontinuously, with one day phase of regeneration at high pressure and one night phase of cold production at low pressure. A global dynamic model allows the simulation of the different system components functioning depending on the hourly weather conditions. It takes into account the transient periods and shows the temperature changes of the components, the chemical reactions in the system and its performances. This system will cover the cooling needs of a 560 L cold box at −20 °C during the 3 sunniest months of the year and provide more than 60% of the total yearly cooling needs of this box for the weather conditions of Perpignan (South of France). The prototype is expected to show a system coefficient of performance (COP) of about 0.07 over the 10 sunniest months of the year, and a net solar COP of 0.05, taking into account the collectors efficiencies.

New deep-freezing process using renewable low-grade heat: From the conceptual design to experimental results

An exergy-based analysis applied to ideal thermochemical dipoles allowed to design an original process that could use low-grade energy, produced from a thermal solar collector at around 70 °C, to provide low-temperature cold, below −23 °C, in order to store deep-frozen food. The ideal coefficient of performance (COP) of this system is 0.5 and the exergetic yield is 1. Taking into account the process enthalpies and the sensible heat of the reactants, the COPthermo is 0.17. The process functioning is described in this paper. It alternates between a regeneration mode during daytime and cold production mode during night-time. An experimental prototype was designed and built. It proved the feasibility of the concept and showed an experimental COP of about 0.06, which is similar to the up-to-date solar cooling systems, but at higher cold temperatures. The mean annual exergetic yield of the process is about 0.06.

Modelling and performances of a deep-freezing process using low-grade solar heat

A solar deep-freezing process has been designed. It aims at cooling down a cold box to about −20 °C, using simple flat plate solar collectors operating at 70 °C. This original process involves two cascaded thermochemical systems based on the BaCl 2/ammonia reaction. Its working mode is discontinuous as it alternates between a regeneration mode during daytime and a cold production mode during nighttime. A global dynamic model involving the various system components allows the simulation of the process; it predicts the evolution of the components temperatures and the rates of chemical reactions of the system. It also allows the dimensioning of the system components to maintain a 500 l cold box at −20 °C during the 6 sunniest months of the year under typical Mediterranean weather conditions and provide over 80% of the total yearly cooling needs of this box. This requires a solar collector area of 5.8 m 2 and 39 kg of reactive salt. The predicted coefficient of performance (COP) is about 0.1 over the year, and the net solar COP, taking into account the collector efficiencies, is 0.05.

Cryopreservation of human platelets with dimethyl sulfoxide: changes in biochemistry and cell function.

The shelf life of liquid-stored platelet concentrates is limited to 5 days. Therefore, much work has been carried out in an attempt to establish the optimum method for cryopreservation. Among the various cryoprotectants, dimethyl sulfoxide (DMSO) has been shown to be the most effective. However, DMSO-frozen platelets are characterized by a number of cell lesions. This report describes metabolic and functional changes that should give rise to some concern about the functional integrity of these cells. Single-donor platelet concentrates were frozen in liquid nitrogen by use of DMSO (5%). After thawing, the cells were washed and resuspended in autologous plasma. Before, during, and after the freezing process, samples for analysis of metabolic measures (e.g., pH; calcium, potassium, and lactate dehydrogenase concentrations; plasma complement factors) and functional measures (e.g., aggregometry, in vitro bleeding time, alpha-granule membrane protein-140 expression) were taken. Mean platelet volume increases during the deep-freezing process. Potassium, calcium, and lactate dehydrogenase are released from the intracellular space to the extracellular space. A strong activation of complement, which is mainly due to the addition of DMSO, is observed. Platelets become activated as indicated by the expression of alpha-granule membrane protein-140. Accordingly, decreased platelet function can be observed. DMSO-frozen platelets are characterized by several metabolic and functional changes. Although these cells have been shown to exert hemostatic effects in vivo, it is conceivable that those effects could be improved by further development of platelet-freezing techniques.

The treatment of infectional asthma in children with filtrates of cultures of upper respiratory pathogenic bacteria: Stevens, F. A.: J. Pediat. 14: 307, 1939

Thermography has been used in many fields to perform non-invasive temperature measurements of natural objects. In this paper, thermography was used to determine the temperature of leaves, stems and branch kerfs of Japanese spindle (Euonymus japonicus Thunb.) and glossy privet (Ligustrum lucidum Ait.) in the city of Jinan in China during winter. The temperatures of the leaves, stems and branch kerfs were monitored as the temperature decreased after the sample was subjected to hand heating or after the branch was cut. Differences in the specific heats and the latent heats of the leaves, branches and stems with different water contents and transpiration capacities were confirmed. The significant temperature difference obtained after hand heating between different leaf sections with varied water contents made it easy to obtain the thermal images, which were clear and exhibited reduced systematic errors. After hand heating, a significantly higher temperature was found at the major vein system of both Japanese spindle and glossy privet. This increased temperature difference made it possible to detect the water and the thermal state of these leaves. Therefore, it was possible to detect scorched area of the leaves, the twig dieback and the sap warming phenomenon in the leaves using thermography. In addition, the leaf bending phenomenon observed in Japanese spindle leaves during the deep freezing process indicates that the leaf scorch symptoms result from water stress and a lack of sap warming.