Frozen Storage Methods Research Articles

Effects of sequential combination of cryogenic immersion freezing and ultra-cold frozen storage on the quality of Korean white kimchi

This study aimed to assess the effects of three different freezing techniques — cold room freezing (CRF; −20 °C), air-blast freezing (ABF; −70 °C), and cryogenic immersion freezing (CIF; −70 °C) — on the microstructure and physicochemical properties of Korean white kimchi (KWK) during frozen storage at −20 °C and − 45 °C for 8 weeks. CIF-treated KWK exhibited a higher freezing rate and after ultra-cold (UC; −45 °C) frozen storage, it showed a greater number and smaller diameter and area of ice crystals than CRF- and ABF-treated KWK. Drip loss was reduced and CIE color changes were delayed in KWK under UC frozen storage. The pH, titratable acidity, and reducing sugar content of frozen KWK remained unaffected by the freezing method, storage temperature, or duration. Thus, CIF combined with UC frozen storage preserves the physicochemical quality of KWK with minimal histological damage during long-term storage. Industrial relevanceIn the kimchi industry, where the shelf life of commercial products is often constrained by successive fermentation under low-temperature storage and distribution conditions, introducing frozen kimchi is a promising solution to reduce waste of overripe kimchi in the supply chain. This study highlights the effectiveness of combining CIF and UC frozen storage methods to minimize the damage caused by freezing in kimchi. This innovative technology provides a practical means for streamlining freezing processes, saving operational time, and ensuring kimchi quality during long-term storage and distribution.

A Study on the Prediction of Electrical Energy in Food Storage Using Machine Learning

This study discusses methods for the sustainability of freezers used in frozen storage methods known as long-term food storage methods. Freezing preserves the quality of food for a long time. However, it is inevitable to use a freezer that uses a large amount of electricity to store food with this method. To maintain the quality of food, lower temperatures are required, and therefore more electrical energy must be used. In this study, machine learning was performed using data obtained through a freezer test, and an optimal inference model was obtained with this data. If the inference model is applied to the selection of freezer control parameters, it turns out that optimal food storage is possible using less electrical energy. In this paper, a method for obtaining a dataset for machine learning in a deep freezer and the process of performing SLP and MLP machine learning through the obtained dataset are described. In addition, a method for finding the optimal efficiency is presented by comparing the performances of the inference models obtained in each method. The application of such a development method can reduce electrical energy in the food manufacturing equipment related industry, and accordingly it will be possible to achieve carbon emission reductions.

Effects of storage temperature and time on the contents of different nitrogen forms in fresh soil samples.

Soil nitrogen forms and contents are of great importance in ecological studies. The storage methods of soil samples have great effects on the accuracy of determination of nitrogen contents. We aimed to select a reasonable storage method for soil samples with forest soil of Castanopsis faberi fore-st at Wanmulin Nature Reserve in Jian'ou City as an example. The contents of soil ammonium, nitrate, total nitrogen, soluble organic nitrogen, amino acid nitrogen and microbial biomass nitrogen were measured in soil samples under the storage conditions of different temperature (at 25, 4 and -20 ℃) and different times (0, 7 and 30 days). The nitrogen contents during the process of cultivating under the room temperature after being frozen were also measured. The results showed that the contents of all nitrogen forms except for amino acid nitrogen were increased in the soil samples that stored at the room temperature for seven days. There were no significant differences between the contents of all the tested nitrogen forms in the refrigerated or frozen samples and the fresh soil samples. The changes of nitrogen content in soil samples at refrigerated and frozen storage were more stable than those at room temperature storage. The low temperature storage could stimulate soil mineralization. Hence, after stored for 30 days, contents of all the tested nitrogen forms in the refri-gerated and frozen storage soil samples were significantly higher than those in the fresh samples except for the soluble organic nitrogen, whereas there was no significant difference between the refrigerated and frozen storage methods. Therefore, fresh samples should be promptly processed when taken back to the laboratory. If the samples needed to storage, it should not be stored more than half a month. If the samples need a longer storage time, it must be placed in lower temperature (at -40 or -80 ℃). Pre-incubation treatment was required when the low temperature storage soil sample was subjected to an experiment. In the process of pre-incubation, the contents of all the tested nitrogen form in soil samples gradually approached the level of fresh soil sample with the increases of incubation time except for that of nitrate which decreased firstly and then increased rapidly. After incubation for about one week, the nitrogen content of soil sample returned to the level that was close to that of the fresh soil. In combination with studies previously reported, soil samples collected from field and air dried samples needed a pre-incubation for 5-14 days, and the pre-incubation time for the cold storage sample should not be less than one week.

Effects of three frozen storage methods on wet weight of fish

Wet weight is one of the most common biological descriptors collected for fisheries research. Freezing is frequently used to preserve fish prior to processing in a lab, and wet weights are often collected for thawed fish. Freezing may affect the wet weight of fish and result in biased values for weight based metrics. Our objectives were to determine the effects of three frozen storage methods, size class of fish, and duration of storage on the changes in wet weight of emerald shiner (Notropis atherinoides) and rudd (Scardinius erythrophthalmus), and how failure to account for changes in wet weight affects percent dry weight estimates. Two size classes of emerald shiner and three size classes of rudd were collected from the upper Niagara River, New York. Fish were weighed immediately after being euthanized and then glazed with water, frozen in water, or vacuum-sealed and stored at −25°C for 3 or 6 months. After measuring post-thaw wet weight, fish were dried to a constant weight and percent dry weight was calculated based on prestorage wet weight and post-thaw wet weight. Then, we compared species specific prestorage wet weights to post-thaw wet weights for each storage method. Analysis of variance was used to investigate the effects of storage method, size class, and duration stored on wet weights of each species. Prestorage and post-thaw percent dry weights were compared to illustrate the effects of frozen storage on a commonly used weight-based metric. Emerald shiner and rudd wet weights differed from initial weights for all storage methods. Percent change in wet weight of emerald shiner was affected by interactions among storage method, size class, and duration stored, while percent change in wet weight of rudd was affected by the interaction between fish size class and storage method. Overall, storage method and size class had the greatest effects on changes in wet weight following frozen storage. Post-thaw wet weight increased from initial wet weight for fish frozen in water and decreased for vacuum-sealed and glazed fish, and smaller fish generally experienced greater changes than larger fish of the same species. Percent dry weight estimates based on post-thaw wet weights differed proportionally by −10.6–29.8% from estimates based on prestorage wet weights. Frozen storage can substantially affect weight based metrics such as percent dry weight and should be accounted for if weight is not measured prior to freezing.

Effect of storage methods on indentation-based material properties of abdominal organs

To investigate the possible changes in material properties of cadaveric abdominal organs due to the preservation methods, the indentation data obtained from porcine abdominal organs (kidney, liver, and spleen) preserved by cooling and freezing are analyzed statistically in this study. Indentation tests were first conducted on fresh specimens. One half of the specimens of each organ were then frozen (preserved at - 12 degrees C), and the other half of the specimens were cooled (preserved at 4 degrees C). All preserved specimens were retested after 20 days. Force and displacement data recorded during indentation were analyzed using a quasi-linear viscoelastic model. The results show that both cooling and freezing storage increased the kidney stiffness. In contrast, both storage methods decreased the stiffness of the spleen specimens. While cooling increased the liver stiffness, no significant changes of the instantaneous elastic response were observed in the liver specimens preserved by freezing. The liver and spleen's reduced relaxation responses and the liver's instantaneous elastic response were significantly different when comparing between cooling and freezing effects after 20 days of preservation. This study showed that both cooling and freezing storage methods significantly changed the material properties of abdominal organs, especially the instantaneous elastic response. More research is needed in investigating the effect of preservation on failure properties and mechanical properties under large deformation.

Cryopreserved Tracheal Grafts: A Review of the Literature

Cryopreserved tracheal grafts have been used in several experimental models of long segment replacement. The clinical application of the procedure has been limited due to the fact that contradictory results have been reported. The purpose of this article is to present a review of the literature on tracheal cryopreservation. Despite the fact that most authors indicate that cryopreserved tracheal allografts retain viability and have a low immunological response, though they continue to function after transplantation with good epithelialization and patency, cryopreservation leads to significant damage to cartilage, the degree of which is based on the freezing–storage methods that affect the function and durability of a graft. The long-term storage of cartilage must therefore be investigated in more detail in basic research models of cartilage viability: the evaluation of chondrocyte apoptosis, and the use of different solutions for tracheal cryopreservation other than RPMI-1640, Dulbecco's modified Eagle's, Eurocollins, and TC-199. Furthermore, problems that involve improving the blood supply to the graft after extensive resection and immunosuppression must be resolved before tracheal cryopreservation can become a clinically established method for tracheal grafts.