Conventional Freezer Research Articles

THE EFFECT OF CONVENTIONAL AND SHOCK FREEZING ON DRIP LOSS AND TEXTURAL PARAMETERS OF BEEF MEAT

Abstract The effect of conventional and shock freezing on thaw drip loss and firmness of beef meat was studied. The meat samples was frozen in conventional freezer at -18 °C and shock frozen meat samples reached -50 °C temperature. Drip loss was measured by weighing the meat sample during thawing. The firmness was performed with TA-XT Plus Texture Analyzer with the volodkevich bite jaws. The firmness score and thaw drip loss differences did not been recognized between conventional and shock freezing meat excluding 7th day.

Avaliação de diferentes modelos de secagem para liofilização de mangabas maduras com diferentes diâmetros, através de indicadores de desempenho

Os modelos matemáticos de secagem são empregados com o intuito de caracterização do processo ao estimar parâmetros importantes para o mesmo. A mangaba (Hancornia speciosa Gomes) é uma fruta de clima tropical com elevada perecibilidade, este aspecto propõe o uso de técnicas alternativas para promover o aumento da vida útil, dentre está à liofilização. Diante disto, objetivou-se analisar diversos modelos matemáticos (Page, Henderson e Pabis, Lewis e Midilli) para avaliar aquele que melhor se adequa as condições do processo, por meio de índices de desempenho associados a cada modelo: fatores de precisão (Af) e de viés (Bf), raiz do erro quadrático médio (REQM) e erro padrão de predição (%SEP). As frutas foram congeladas à temperatura de -20°C em freezer convencional, seguida da liofilização, em liofilizador da marca Liotop modelo L-108, a -50°C e vácuo parcial de 38 μmHg durante 1380 min. Mediante os resultados, observa-se que o modelo de Page mostrou-se mais preciso independentemente do diâmetro, com Af: 1,9198, Bf:1,8446 , REQM: 0,0275 e %SEP: 5,6298 e Af: 1,7334 Bf: 1,6735; REQM: 0,0221 e %SEP: 3,5545 para as mangabas pequenas e grandes, respectivamente. Diante disto, nota-se que a melhor correlação entre os dados experimentais e estimados é dada pelo Modelo de Page.

Lyophilization of Avocado (Persea americana Mill.): Effect of Freezing and Lyophilization Pressure on Antioxidant Activity, Texture, and Browning of Pulp

Effects of both previous freezing (−26 and −80°C) and lyophilization (0.12, 0.37, and 1.07 mbar) conditions on drying kinetics, antioxidant activity, texture, and browning index of avocado pulp were evaluated. Vacuum pressure was found to have less effect on the lyophilization process than previous freezing temperature. Samples frozen initially at − 80°C required a longer lyophilization time. The best fittings for the drying kinetics of the avocado were obtained using the Page equation. The processing directly affected the antioxidant activity of the avocado pulp. Both the lipophilic and the hydrophilic fraction of the freeze-dried pulp decreased antioxidant activity, regardless of the applied pressure or freezing type. The hardness of the fresh avocado (0.93 N) was higher than the freeze-dried samples frozen in a conventional freezer (0.49 N) and their adhesion was greater than all of the freeze-dried samples. Freeze-dried pulps showed higher browning index than fresh avocado pulp (135.3).

Migratory Response ofEchinostoma caproni(Digenea: Echinostomatidae) to Feeding by ICR Mice

The migratory response of Echinostoma caproni to host feeding was examined in female ICR mice. Thirty-six mice were each infected with 20 metacercariae of E. caproni . Twenty-eight days post-infection, food, but not water, was withheld for 24 hr. Mice were haphazardly divided into 4 groups of 9, and each group received one of the following treatments: (1) 0.25 g glucose, (2) access to standard lab chow, (3) 0.5 ml saline, and (4) continued fasting. Three mice from each treatment group were killed 1, 2, and 4 hr post-treatment. The intestine of each mouse was removed, flash-frozen, and stored in a conventional freezer for later examination. Intestines were partially thawed, measured, and opened longitudinally, and the position of each worm, or worm cluster was measured. The intestine was divided into equal 5% segments based on the initial measurement and locations of worms, and worm clusters were recorded from the appropriate section of the intestine for analysis. There was no significant effect of treatment in the position of worms at 1 hr. There was a posterior shift in worm position in all treatment groups at 2 hr, except in the saline-treated mice; however, only worms in the glucose-fed mice were significantly posterior to the unfed controls. From 2 to 4 hr, there was a significant anterior movement of worms in both the glucose and chow-fed mice. The data strongly suggest that E. caproni responds to the initiation of gastric activity of the host by migrating anteriorly in the ileum. The specific stimulus for this migration is unknown.

Stabilizing RNA at Room Temperature in RNAstable®

BioTechniquesVol. 48, No. 6 Application Forum - Sponsored Paper: The RNA WorldOpen AccessStabilizing RNA at room temperature in RNAstable®Sharron Ohgi, Laurent Coulon, Rolf Muller, Judy-Muller-Cohn & Omoshile ClementSharron Ohgi*E-mail Address: sohgi@biomatrica.comBiomatrica, Inc., 5627 Oberlin Dr, #120, San Diego, CA, 92121, USASearch for more papers by this author, Laurent CoulonBiomatrica, Inc., 5627 Oberlin Dr, #120, San Diego, CA, 92121, USASearch for more papers by this author, Rolf MullerBiomatrica, Inc., 5627 Oberlin Dr, #120, San Diego, CA, 92121, USASearch for more papers by this author, Judy-Muller-CohnBiomatrica, Inc., 5627 Oberlin Dr, #120, San Diego, CA, 92121, USASearch for more papers by this author & Omoshile ClementBiomatrica, Inc., 5627 Oberlin Dr, #120, San Diego, CA, 92121, USASearch for more papers by this authorPublished Online:3 Apr 2018https://doi.org/10.2144/000113453AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinkedInReddit IntroductionRNAstable® is a novel preservation product developed to protect RNA from degradation during storage or shipment at ambient temperatures. The synthetic storage medium is based on the natural principles of anhydrobiosis (meaning “life without water”), a biological mechanism employed by some organisms that enables their survival while dry for more than 100 years. Anhydrobiotic organisms protect their DNA, RNA, proteins, membranes and cellular systems for survival in a dry state and can be revived by simple rehydration. RNAstable was designed to mimic these unique characteristics to stabilize RNA at ambient temperatures for prolonged time periods. Quantitative RT-PCR analysis demonstrates successful amplification of RNA templates that were stored dry in RNAstable for 29 months at room temperature and under accelerated aging conditions equivalent to 12 years of room temperature storage (elevated temperatures at 45°C). Samples were sealed inside a moisture-barrier bag including a desiccant pack to ensure ideal storage conditions. Rehydrated samples were used directly in reactions without further purification and exhibited no inhibition or loss of activity. This innovative technology prevents degradation of RNA at room temperature and offers tremendous cost and energy savings as an easy-to-use alternative to conventional freezer storage.ExperimentTotal RNA was extracted from frozen 293T cells using TRIzol® following the manufacturer's instructions. Aliquots (500 ng) of extracted total RNA were added to RNAstable® in a 96-well plate and allowed to dry overnight in a laminar flow hood. Dried samples were stored for 29 months both at room temperature inside a sealed moisture-barrier bag including a desiccant pack, and at 45°C.1 Reference control samples were also stored at −80°C for the identical time period (29 months). RNA samples stored in RNAstable were rehydrated in 25 µL DEPC-treated water to a final concentration of 20 ng/µL. Serial dilutions were performed to a final concentration of 2pg/µl. The unprotected samples were prepared in the same way. A 5-µL aliquot (10 pg) of each sample was used as template for expression of the 18S rRNA gene using the TaqMan® One-Step RT-PCR (ABI) kit. A final concentration of 400 nM was used for each forward and reverse primer in the reaction. A 250-nM final concentration of the 18S rRNA probe was used (5′-labeled with FAM and 3′-labeled with TAMRA). Reactions were prepared in a 25-µL final volume.Results and discussionThe gel images,2 bioanalyzer RIN scores,2 and RT-PCR results (Figure 1) obtained for RNA samples stored in RNAstable either at room temperature or at 45°C are similar to those at −80°C, indicating that RNAstable offers same level of protection as that of cold storage. We find that optimal RNA sample protection from degradation at room temperature is afforded by storing in RNAstable tubes or well plates and placed inside a heatsealed moisture barrier bag with a desiccant. RNA recovery from RNAstable is by simple hydration, and the sample is ready for use without further purification in downstream applications such as qRT-PCR, in vitro transcription, Bioanalyzer, and expression analysis. RNAstable offers researchers the ability to store and transport RNA at room temperature without loss of sample quality, and at significant cost savings on materials, labor and shipping.Figure 1. One-Step RT-PCR results of stored RNA samples in RNAstable at room temperature and 45°C, versus storage at −80°C (control) quantified using the 18S rRNA gene.Three samples were amplified for each storage condition and the results from the 9 reactions are overlaid on the graph.1Accelerated aging: 29 month storage at 45°C ≍ 12 years storage at room temperature.2See: http://www.biomatrica.com/rnastable.phpFiguresReferencesRelatedDetailsCited ByParasite-derived microRNAs as a diagnostic biomarker: potential roles, characteristics, and limitations22 April 2021 | Journal of Parasitic Diseases, Vol. 45, No. 2Short-Term Stability Study of RNA at Room TemperatureBiopreservation and Biobanking, Vol. 10, No. 6Following Nature's Lead: Generating Compounds for Stabilizing BiomoleculesBiopreservation and Biobanking, Vol. 10, No. 4 Vol. 48, No. 6 Follow us on social media for the latest updates Metrics History Published online 3 April 2018 Published in print June 2010 Information© 2010 Future Science LtdPDF download

Acorn storage alternatives tested on Oregon white oak

We assessed various combinations of storage factors: bag type, temperature, duration, and antifungal pre-storage treatments for white oak acorn storage, using Oregon white oak ( Quercus garryana Douglas ex Hook. [Fagaceae]) acorns from 7 seed sources. Acorn viability remained high (84%), even after 2 y of refrigerated storage, but the majority of these acorns germinated between 6 and 12 mo after entering storage. Germination during storage differed significantly by seed source. The likelihood of successful storage of Oregon white oak acorns was increased by placing washed, healthy-appearing acorns in storage at a near-freezing temperature (1.6 °C [35 °F]) soon after collection. Sealed conventional freezer bags or specialized gas-permeable plastic bags were equally effective in maintaining viability. For 6-mo storage under the best treatment combination, 77% of acorns remained viable but ungerminated in storage, compared to 89% viability prior to storage.

Freeze‐Thaw Stability of Bualoy Thai Dessert Using Waxy Rice Flour

ABSTRACTFrozen food products are gaining acceptance in Thai food industry and frozen bualoy dessert is a good opportunity for marketing in domestic and for exports. One important factor affecting quality of frozen starchy foods is retrogradation of starch gels. Thus freeze‐thaw stability of a frozen bualoy made from total waxy rice flour was studied and compared among the samples modified by 20 and 30% cross‐linked tapioca starch (CTS) derivatized with phosphorylation and 0.25% propylene glycol alginate (PGA). The waxy rice flour was pregelatinized by adding boiled water before shaping as a ball, then boiled and mixed with coconut syrup. All samples were subjected to five freeze‐thaw cycles over 60 days in a conventional freezer (–18°C). Texture analysis firmness and stickiness of the nonfrozen gels substituted with 20% CTS (382 ± 43, 20.5 ± 7.1 g·f) and 30% CTS (493 ± 37, 31.1 ± 7.0 g·f) were significantly different as compared with the control (329 ± 22, 14.8 ± 3.1 g·f). Similar results were observed for the samples continuously frozen for 60 days. The effects of freeze‐thaw stability to the frozen gels of the control, CTS, and PGA substituted samples appeared after two cycles and exhibited a large increase in firmness and stickiness at the fourth cycle. The firmness values obtained from the control and the samples substituted with 20% and 30% CTS were 2,397 ± 197, 2,182 ± 203, and 2,104 ± 200 g·f, respectively. This evidence was also observed with the samples containing PGA, but the effect was slightly less. This might account for the recrystallization of amylopectin molecules induced by freeze‐thawings. With DSC, the waxy rice gels showed a significant increase in the melting enthalpy (2.39 ± 0.23 J/g) at the fifth cycle from the nonfrozen gels (0.11 ± 0.02 J/g). The sensory tests of the bualoys were correlated with textural qualities that were acceptable to the panelists when the freeze‐thawing went no further than the second cycle.

Modeling of the effect of freezer conditions on the hardness of ice cream using response surface methodology

The effect of conventional continuous freezer parameters [mix flow (L/h), overrun (%), drawing temperature (°C), cylinder pressure (kPa), and dasher speed (rpm)] on the hardness of ice cream under varying measured temperatures (−5, −10, and −15°C) was investigated systematically using response surface methodology (central composite face-centered design), and the relationships were expressed as statistical models. The range (maximum and minimum values) of each freezer parameter was set according to the actual capability of the conventional freezer and applicability to the manufacturing process. Hardness was measured using a penetrometer. These models showed that overrun and drawing temperature had significant effects on hardness. The models can be used to optimize freezer conditions to make ice cream of the least possible hardness under the highest overrun (120%) and a drawing temperature of approximately −5.5°C (slightly warmer than the lowest drawing temperature of −6.5°C) within the range of this study. With reference to the structural elements of the ice cream, we suggest that the volume of overrun and ice crystal content, ice crystal size, and fat globule destabilization affect the hardness of ice cream. In addition, the combination of a simple instrumental parameter and response surface methodology allows us to show the relation between freezer conditions and one of the most important properties—hardness—visually and quantitatively on the practical level.

Production of bovine cloned embryos with donor cells frozen at a slow cooling rate in a conventional freezer (−20 °C)

SummaryUsually, fibroblasts are frozen in dimethyl sulphoxide (DMSO, 10% v/v) at a cooling rate of 1 degrees C/min in a low-temperature (-80 degrees C) freezer (LTF) before storage in liquid nitrogen (LN2); however, a LTF is not always available. The purpose of the present study was to evaluate apoptosis and viability of bovine fibroblasts frozen in a LTF or conventional freezer (CF; -20 degrees C) and their subsequent ability for development to blastocyst stage after fusion with enucleated bovine oocytes. Percentages of live cells frozen in LTF (49.5%) and CF (50.6%) were similar, but significantly less than non-frozen control (88%). In both CF and LTF, percentages of live apoptotic cells exposed to LN2 after freezing were lower (4% and 5%, respectively) as compared with unexposed cells (10% and 18%, respectively). Cells frozen in a CF had fewer cell doublings/24 h (0.45) and required more days (9.1) to reach 100% confluence at the first passage (P) after thawing and plating as compared with cells frozen in a LTF (0.96 and 4.0 days, respectively). Hypoploidy at P12 was higher than at P4 in cells frozen in either a CF (37.5% vs. 19.2%) or in a LTF (30.0% vs. 15.4%). A second-generation cryo-solution reduced the incidence of necrosis (29.4%) at 0 h after thawing as compared with that of a first generation cryo-solution (DMEM + DMSO, 60.2%). The percentage of apoptosis in live cells was affected by cooling rate (CF = 1.9% vs. LFT = 0.7%). Development of bovine cloned embryos to the blastocyst stage was not affected by cooling rate or freezer type.

Experimental investigation of an innovative low electricity consumption air cooling system for small building application

This paper investigates the development of a low cost air cooling system used for small scale applications. Its operation is based on the rational and efficient use of energy available in conventional freezers, used for other purposes than air conditioning, to cool small areas. In this paper, the proposed air cooling system is applied to small kiosk prototype (called “periptero”), found very often in the streets of Greek cities and villages, used to sell goods to people. The proposed air cooling system is using the low temperature air inside the freezers to cool the air inside the kiosk and provide a better living environment for the owner, particularly during summer period. The basic principle of the system operation and the experimental installation will be described and the experimental results will be presented and discussed.

112 VIABILITY AND APOPTOSIS OF BOVINE FIBROBLASTS FROZEN IN A CONVENTIONAL ( - 20°C) OR LOW-TEMPERATURE ( - 80°C) FREEZER

Fibroblasts are commonly frozen in dimethyl sulfoxide (DMSO, 10% v/v) at a cooling rate of 1°C min−1 in cryo-containers placed in a low-temperature (−80°C) freezer (LTF) overnight before storage in liquid nitrogen (LN2). LTFs are not always available and cell viability may be altered by freezing at different cooling rates. Therefore, the purpose of the present study was to evaluate apoptosis and viability of bovine fibroblasts frozen at different cooling rates in a −80°C freezer or conventional −20°C freezer. Fibroblasts were generated from skin tissue collected from an adult female cow. Tissue was cut and cultured in DMEM for 7 to 10 days and passaged 2 or 3 times before being cryopreserved. Cells were frozen by one of 6 procedures; cells that were not frozen served as a control. To be frozen, cells were resuspended in DMEM + 10% FBS and 10% DMSO in 2-mL cryo-vials before being placed into freezing containers (Mr. Frosty, Nalgene). For groups 1 and 2, the container was placed in a −20°C freezer and cooled at ≈0.6°C min−1 to −7°C; ice formation was induced by seeding, after which cooling was continued at ≈0.6°C min−1 to −20°C. Vials in groups 1 and 2 were placed in LN2 after 1 h and 16 to 18 h, respectively. Group 3 and 4 vials were also cooled to −20°C at 0.6°C min, except that these samples were not seeded. After being held at −20°C for 16 to 18 h, group 3 vials were thawed; group 4 vials were stored in LN2. Vials in groups 5 and 6 were placed into a Mr. Frosty container and cooled at ≈1°C min−1 in a −80°C freezer. After being held at −80°C for 16 to 18 h, group 5 vials were thawed, and group 6 vials were placed into LN2. Group 1, 2, 3, and 4 vials were thawed in a 37°C water bath; group 5 and 6 vials were thawed in a 40°C water bath. Cell viabilities were quantified by using TB exclusion (TB) with microscopy. At least 20 000 cells from each group were thawed, and caspase 3, a key enzyme involved in apoptotic processes, was detected using a Caspase 3-FLICA apoptosis detection kit; propidium iodide-stained nuclei were assessed with cytometry (FCM) to determine viability (Table 1). Data were analyzed by ANOVA (P < 0.05). Although there were viability differences among groups, freezer type, seeding, holding time, and LN2 had no significant impact, as assessed by TB or FCM; however, no LN2 significantly increased the percentage of viable cells displaying apoptosis. In summary, bovine fibroblasts were successfully frozen in a conventional (−20°C) freezer before storage in LN2. Table 1. Viability and apoptosis of bovine fibroblasts frozen at −20°C or −80°C

The Design and Operation of a Passive Humidity-Controlled Cold Storage Vault Using Conventional Freezer Technology and Moisture-Sealed Cabinets

The Design and Operation of a Passive Humidity-Controlled Cold Storage Vault Using Conventional Freezer Technology and Moisture-Sealed Cabinets

Effect of preparation method on composition and NIR spectra of forage samples

To evaluate the effects of freezing and drying methods on chemical composition and NIR spectral features of pasture samples, 20 samples of different swards were frozen by liquid nitrogen (LN) or conventional freezer and subsequently dehydrated by freeze drying or by forced-air oven under different conditions of time and temperature explaining seven experimental treatments. Near infrared spectra were taken and principal components (PC) computed to plot samples according to scores and visualise potential segregating effects of treatments. Several chemical constituents relevant to nutritional quality of forages were determined and effects of treatments were evaluated by one-way ANOVA. Two-way ANOVA was applied to evaluate effects of freezing (LN or freezer) and drying method (freeze drying, minimum 72 h, or oven drying at 60 °C, 48 h). One-way ANOVA detected significant effects of treatments ( P<0.05) for soluble protein (SCP), neutral detergent fibre (NDF) and insoluble nitrogen in the NDF (NDFIN), but no significant effects were apparent ( P>0.05) for dry matter (DM), crude protein (CP), crude fibre (CF), acid detergent fibre (ADF) and in vitro digestible organic matter content (DOMD). Two-way ANOVA showed that in comparison with freeze drying, oven drying at 60 °C for 48 h significantly reduced (relative change) SCP and DOMD, by 27 and 2%, respectively, while there was a significantly relative increase in NDF and NDFIN, by 10 and 247%, respectively. No significant effects of freezing methods were apparent. Plotting spectra according to the first two principal components showed a clear separation of freeze dried samples with respect to oven dried samples, indicating relevant spectral differences and suggesting that sample manipulation in the laboratory prior to spectral collection should be consistent to avoid errors that could reduce prediction accuracy in the NIRS analysis. It is concluded that drying method and conditions (temperature and time) can lead to changes in composition, particularly with reference to the protein fraction and digestible organic matter content. Although freeze drying could be considered the best method, cost and time will probably preclude its massive application, except for research purposes or eventually in the reference method for the development of NIR calibrations for predicting composition of undried samples.

Influence of emulsifiers on ice cream produced by conventional freezing and low-temperature extrusion processing

Ice cream at six different levels of emulsification was produced by freezing in a conventional scraped surface freezer and with a serial configuration of a conventional freezer followed by a low-temperature extruder. The aim was to examine the influence of emulsifiers on the process, since both emulsifier addition and low-temperature extrusion may have similar effects on promotion of colloidal structure in ice cream. Ice cream samples from both processes were analyzed for stiffness at draw, fat destabilization indices, melting performance, and microstructure. Low-temperature extrusion generally promoted enhanced fat destabilization, however, fat particle size and solvent extractable fat showed different dependencies on emulsification level from the two processing systems. Although solvent extractable fat reached high levels with increasing emulsification, fat particle size data suggested that fat agglomerate size was controlled by mechanical shearing. Significant difference between the two systems was seen also in the meltdown test, where melting rates for unemulsified and slightly emulsified mixes led to a very low melting rate and high shape retention in extruded ice cream. Scanning electron microscopy detected generally smaller air bubbles for extruded ice creams. Enhanced fat structuring around the air bubble and into the serum phase was also shown for unemulsified extruded samples.

Effects of freezing rate on astringency reduction in persimmon during and after thawing

Abstract We compared the reduction of astringency in the flesh of persimmon fruit ( Diospyros kaki Thunb. cv. `Hiratanenashi') either slowly frozen in a conventional freezer or rapidly frozen with liquid nitrogen, during and after thawing. Astringency and concentration of soluble tannins in flesh frozen by either method had decreased little by the start of thawing. In slowly frozen flesh, soluble tannins decreased greatly during thawing, and the thawed flesh was almost non-astringent. However, rapidly frozen flesh was still astringent after being thawed. Astringency reduction in frozen and thawed persimmon flesh is probably not related to changes in pectic substances, which changed little during and after thawing, whatever the mode of freezing. Microscopic observations suggested that these differences may be related to the degree of damage that occurred in flesh cell walls and plasma membranes during freezing. Soluble tannins, released from tannin cells during thawing, became insoluble on contact with fragments of cell walls and plasma membranes. The process of tannin insolubilization was greatest for slowly frozen flesh. Such adhesion of soluble tannins to fragments of cell walls and plasma membranes may be a factor that reduce astringency in persimmon fruit frozen slowly during and after thawing.

Parasitization performance of Trichogramma spp. (Hym., Trichogrammatidae) reared on eggs of Sitotroga cerealella Oliver (Lep., Gelechiidae), stored at freezing and subfreezing conditions

Abstract: To study the influence of freezing and subfreezing storage conditions of eggs of Sitotroga cerealella on the parasitization performance of Trichogramma pretiosum Riley three different storage conditions were tested: 8°C (refrigerator), – 20°C (freezer) and — 196°C (liquid nitrogen). During the parasitization step, for the eggs stored 30 and 130 days in liquid N2, two further variables were considered: (a) two parasitization temperatures (21°C and 26°C) and (b) addition of ‘kairomones’. An alternative thawing method was tested (water bath at 50°C during 30 min) for eggs stored during 130 days. Storage in a conventional freezer proved to be completely unsuccessful. In the refrigerator, 80% to 90% of the eggs kept in storage for 10 to 13 days, exposed to parasitoids, turned black (eggs with a Trichogramma pupa inside). This percentage declined to 60% for eggs stored during 20 to 25 days and after 35 days the percentage was lower than 30%. The percentage of emergence and the sex ratio were not significantly different among eggs stored during 5 to 25 days but the emergence decreased for eggs stored longer than 25 days. For the sex ratio the only difference was found between the stored and non‐stored eggs. Liquid nitrogen proved to be a good storing method provided that a high amount of parasitoids is not immediately required. The percentage of parasitised eggs (strictly pupation of the paraisitoid) was not significantly different among the treatments (20, 30 or 130 days). Thawing the eggs in a warm water bath plus a raise in temperature during the parasitization increased significantly the yield of parasitoids. Two hypotheses are put forth to explain the probable reasons of the outcomes of the experiments. All in all, if a high performance of the host eggs is required no more than 10 days at approximately 8°C are recommended but if a long term storage is needed, conservation in N2l accompanied by an appropriate thawing method and a good parasitization temperature, proved to be satisfactory.

Texture and Histological Structure of Carrots Frozen at a Programmed Rate and thawed in an Electrostatic Field

ABSTRACTTo investigate the most suitable rate of freezing and method for thawing, raw and blanched carrots were frozen with LN2 (freezing rate: –5°or ‐2°C/min, final temp: ‐30°C) using a program freezer (PF), or were frozen using conventional freezers (F: ‐80°C, ‐30°and ‐20°C). Then, they were thawed in five different ways: electrostatic thawing (ET, ‐3°C, 17 hr); ‐3°C, 17 hr; 5°C, 17 hr; 20°C, 30 min; 100°C, 3 min. Firmness of thawed carrots and amount of undamaged tissues by LM and TEM observations were greatest to least: PF ‐5°C/min &lt; PF‐2°C/ min &lt;‐80°C CF&lt;‐30°CF&lt;‐20°CF, and ET ≧‐3°&lt; 5°&lt; 20°&lt; 100°C, respectively. Results suggest the optimum rate of freezing was ‐5°C/ min. The frozen disks were defrosted comparatively fast even at ‐3°by ET. Drip, cell damage and softening of disks were prevented by ET.

Comparison of conventional and automated refrigerated storage systems

High rise warehouses with automated storage and retrieval systems (AS/RS) can frequently be justified as a viable alternative to conventional freezer storage. To determine viability, a design year data base must be developed and both conventional and automated system/facility options tested against this operational standard. To determine which alternative best suits design year requirements, a justification analysis must be completed. This analysis must address investment costs and total operational costs. Operational factors such as expandability, flexibility and maintainability must be considered. This Paper outlines a basic approach to the justification analysis required when considering high rise automated and conventional alternatives for refrigerated warehousing applications.

Capsule‐Packed Freezing of Cooked Rice and Glutinous Rice Cakes

ABSTRACTCooked rice and commercial glutinous rice cakes were frozen by a capsule‐packed freezing method we developed, then stored. Characteristics of samples frozen by this new method were compared with those of samples frozen in deep freezers (–20°C and –50°C), or chilled in an ordinary (5°C) or Cold Fog refrigerator (0°C). Texturometer measurements, glucoamylase digestion, and X‐ray diffraction analysis of specimens thawed to room temperature indicated that the samples prepared by our new method were superior to those frozen in conventional freezers or chilled in refrigerators. Simulation experiments in a program freezer showed that rapid freezing and adequate tempering were characteristic of our capsule‐packed method.

The effects of freezing and thawing on lactate dehydrogenase and esterase isozyme patterns of the goldfish Carassius auratus, demonstrated by isoelectric focusing

AbstractCurrent literature suggests that the reliability of results obtained from electrophoretic studies using material which has been frozen is in doubt. Banding patterns of lactate dehydrogenase and non‐specific esterase produced by isoelectric focusing (IEF) of fresh tissues from the goldfish, Carassius auratus, are presented. Changes which occur in these patterns due to repeated freezing and thawing involve a reduction in both the intensity and the number of bands. Differences in the IEF profiles are extensive and consistent. Changes also occur in material which has been frozen for a ten‐week period and thawed once. Storage in liquid nitrogen, ‐180°C, as distinct from a conventional freezer at ‐20°C, produes no significant improvement. Interpretation of results from material that has been frozen must therefore be undertaken with extreme care, especially when sensitive separation techniques like IEF are used.