Long-term storage of mouse spermatozoa after evaporative drying

To determine if mouse spermatozoa could be preserved long-term without using liquid nitrogen, mouse spermatozoa in trehalose-EGTA solution were partially evaporatively dried under nitrogen gas (5 min at flow rate10 l/min) and stored for 1 week and 5 months at 4, -20, and -80 degrees C before intracytoplasmic sperm injection. Fertilization rates were neither different with spermatozoa stored at 4, -20, or -80 degrees C for 1 week or 1, 3, and 5 months respectively, nor blastocyst formation rates with spermatozoa stored for 1 week and 1 month. However, spermatozoa stored at 4 and -20 degrees C for 3 months resulted in fewer blastocysts (35.1 and 54.3% respectively) when compared with spermatozoa stored at -80 degrees C (74.4%). Blastocyst formation rates using spermatozoa stored for 5 months at -20 degrees C (57.4%) or -80 degrees C (74.5%) were not significantly different from those stored for 3 months at the same temperatures respectively, but were significantly better than those stored for 5 months at 4 degrees C (10.2%). Blastocysts derived from spermatozoa stored for 3 and 5 months at -20 and -80 degrees C respectively, were then transferred to pseudopregnant mothers to develop into healthy liveborn offspring. No significant differences were found in embryo transfer rates (number of pups born/number of embryos transferred), weaning rates, or sex ratios of resultant pups, which were healthy and reproductively sound. These results demonstrate for the first time that partially evaporatively dried mouse spermatozoa in trehalose-EGTA solution can be preserved for long term at -20 and -80 degrees C. The possibility that the storage temperature must be less than the glass transition temperature is discussed.     

Viability of lactic acid bacteria and bifidobacteria in fermented soymilk after drying, subsequent rehydration and storage

To develop a probiotic dietary adjunct, soymilk fermented with various combinations of lactic acid bacteria (Streptococcus thermophilus and Lactobacillus acidophilus) and bifidobacteria (Bifidobacterium longum and Bifidobacterium infantis) was subjected to freeze-drying and spray-drying. Survival of the starter organisms during the drying process, subsequent rehydration at different temperatures and during a 4-month period of storage under different storage conditions was examined. After freeze-drying, lactic acid bacteria and bifidobacteria exhibited a survival percent of 46.2-75.1% and 43.2-51.9%, respectively, higher than that noted after spray-drying. Regardless of the drying condition, S. thermophilus showed a higher percentage of survival than L. acidophilus, while B. longum survived better than B. infantis. Further study with soymilk fermented with S. thermophilus and B. longum revealed that the freeze-dried and spray-dried fermented soymilk rehydrated at 35-50 degrees C and 20 degrees C, respectively, was optimum for the recovery of the starter organisms. Both S. thermophilus and B. longum survived better in the freeze-dried than the spray-dried fermented soymilk during storage. A higher percent of survival was also noted for both the starter organisms when the dried fermented soymilk was stored at 4 degrees C than 25 degrees C. Holding the dried fermented soymilk in the laminated pouch enabled S. thermophilus and B. longum to exhibit a higher percentage of survival than in the deoxidant- and desiccant-containing glass or polyester (PET) bottle. Among all the packaging materials and storage temperatures tested, starter organisms were most stable in the dried fermented soymilk held in laminated pouch and stored at 4 degrees C. Under this storage condition, S. thermophilus and B. longum showed a survival percentage of 51.1% and 68.8%, respectively, in the freeze-dried fermented soymilk after 4 months of storage. Meanwhile, S. thermophilus and B. infantis in the spray-dried fermented soymilk showed a survival percent of 29.5% and 57.7%, respectively.     

Survival of Brevibacterium linens (ATCC 9174) after Spray Drying, Freeze Drying, or Freezing

The objectives of this work were to: (1) contrast spray drying, freeze drying and freezing for large-scale preservation of B. linens, (2) determine the thermal resistance curves, and (3) measure the storage stability. When B. linens was freeze-dried and frozen in feed suspensions containing 3% (w/v) cell paste and 25% (w/w) total solids, survival was 100%. During spray drying, lethal thermal injury was the main cause of loss of viability. Accordingly, by extrapolation, 100% viability would be possible at an outlet-air temperature of 57°C. Spray-dried and freeze-dried cells were stable during storage at 4°C in the absence of oxygen and moisture.     

Lactosylation of milk proteins during the manufacture and storage of skim milk powders

Extensive lactosylation of milk proteins in standard skim milk powder dried against air between 185 and 90°C (inlet and outlet temperatures of the air) was detected by capillary electrophoresis. Optimisation of the drying conditions included keeping the outlet temperature low (preferably <80°C), since this was the parameter which most affected the extent of lactosylation of milk proteins. The inlet temperature was set in order to obtain the best compromise between a low extent of lactosylation and a high drying rate (170–175°C). These conditions allowed the manufacture of low-lactosylated skim milk powder. Storage of freeze-dried and control low-lactosylated skim milk powder at different temperatures showed that both temperature and moisture content affected the progress of lactosylation during storage. Further drying to less than 2.5% moisture content (w/w) and storage at low temperatures were required to prevent the development of lactosylation in the low-lactosylated skim milk powder.     

Viability, efficacy, and storage stability of freeze-dried biocontrol agent Candida sake using different protective and rehydration media

Viability, efficacy against Penicillium expansum on Golden Delicious apples, and storage stability of freeze-dried Candida sake strain CPA-1 were studied. The effect of several protective agents and rehydration media was investigated in the freeze drying of C. sake. Skimmed milk at 10% concentration was a good rehydration medium for all protectants tested. In general, good viability results were obtained when the same solution was used as a protectant and as a rehydration medium. The best survival was obtained when C. sake cells were protected with 10% lactose + 10% skimmed milk and rehydrated with skimmed milk (85% viability). The potential for biocontrol of the best freeze-dried treatments against P. expansum on apples was compared with that of fresh cells. Freeze-dried treatments at 1 x 10(7) CFU/ml reduced the incidence of decay by 45 to 66%. The best biocontrol effect was obtained with cells that had been freeze dried using 10% lactose + 10% skimmed milk as a protectant and 1% peptone as a rehydration medium, with a 66% reduction in rot incidence. However, in all treatments, the efficacy of freeze-dried cells was significantly lower than fresh cells. The stability of freeze-dried samples decreased during storage and was influenced by storage temperature. In the best treatment, storage of C. sake cells for 60 days at 4 degrees C resulte in final concentrations of 2.5 x 10(8) CFU/ml, which was a 10-fold reduction in relation to the initial starting concentration of cells prior to freeze drying.     

Short-term storage of cane toad (Bufo marinus) gametes

The responses of cane toad (Bufo marinus) gametes, used as a model for the development of assisted reproduction techniques for rare and endangered amphibians, to short-term storage at temperatures > 0 degrees C were studied. Whole excised testes were stored at 0 degrees or 4 degrees C for 15 days, and sperm motility was measured at excision and after storage for 2, 5, 7, 10, 12 and 15 days. Spermatozoa showed > 50% motility for 7 days at 0 degrees C and for 5 days at 4 degrees C. At 15 days, only spermatozoa stored at 0 degrees C still showed some motility (3%). Sperm suspensions were prepared at 5 day intervals over 30 days in simplified amphibian ringer (SAR) at dilutions of 1:1, 1:5 and 1:10 (w/v) testes:SAR. Aliquots from each dilution were stored at 0 degrees C in Eppendorf tubes opened at 5 day intervals of storage (aerated) or kept sealed (unaerated) (treatments: aerated or unaerated; 5, 10, 15, 20, 25 and 30 days storage). After 30 days, sperm motility and fertilizing capacity were determined. The optimal protocol for sperm storage up to 10 days, as assessed by the retention of fertilizing capacity, was as a 1:5 testis:SAR (w/v) suspension, whereas the longest absolute retention of both motility and fertilizing capacity was observed in concentrated (1:1 dilution), anaerobic suspensions (up to 25-30 days). Oviductal oocytes placed in SAR at 5, 10, 15, 20 and 25 degrees C immediately after ovulation lost viability when cooled rapidly to 5 degrees C and stored for 2 h. However, oocytes retained viability for up to 8 h at the optimum storage temperature of 15 degrees C. Thus, it is concluded that during short-term storage spermatozoa retain viability for longer than oocytes, and that spermatozoa in suspensions retain viability for longer than spermatozoa stored in situ in excised testes.     

EFFECT OF PRESERVATION METHODS ON QUALITIES OF GIANT FRESHWATER PRAWNS (MACROBRACHIUM ROSENBERGII)

The effects of three common commercially-practiced preservation methods, i.e., individual quick freezing (IQF), freeze drying and canning, on the quality of giant freshwater prawns (Macrobrachium rosenbergii) were studied. Physical and chemical quality parameters of IQF prawns stored at ?25 ± 1C changed slightly during 6 months' storage. The freeze-dried and the canned prawns stored at 24 ± 0.5 C could maintain their physical, chemical and sensory qualities during 6 months of storage very well.     

Crystallization and X-ray Diffraction of Crystals Formed in Water-Plasticized Amorphous Spray-dried and Freeze-dried Lactose/Protein Mixtures

ABSTRACT: Effects of proteins (whey protein isolate [WPI], Na-caseinate, and gelatin), drying method, storage relative vapor pressure (RVP), and time on lactose crystallization and crystals formed were investigated using x-ray diffraction (XRD). Crystallization was observed from increasing peak intensities of XRD patterns. Lactose in lactose/protein (5:1,3:1) mixtures crystallized in samples stored at RVP of 44.1% and above in both spray-dried and freeze-dried materials, except in freeze-dried lactose/Na-caseinate and lactose/gelatin mixtures, which showed lactose crystallization at 54.5% RVP and above. The rate of crystallization increased with increasing RVP and storage time. The rate of crystallization in spray-dried materials was higher than in freeze-dried materials, and the crystallization rate decreased with increasing protein content. Lactose crystallized mainly as α-lactose monohydrate in spray-dried lactose/WPI and lactose/gelatin mixtures. Crystals formed in freeze-dried lactose/WPI and lactose/gelatin mixtures were anhydrous β-lactose and α-lactose monohydrate crystals. Lactose crystallized as a-lactose monohydrate in both spray-dried and freeze-dried lactose/Na-caseinate mixtures. Trace amounts of anhydrous β-lactose were present in spray-dried lactose/WPI (5:1) and lactose/gelatin (5:1) mixtures. Peak intensities of XRD patterns for anhydrous β-lactose decreased with increasing protein content and storage time. The crystallization data were successfully modeled using Avrami equation at an RVP of 65.6% and above. These data are important in understanding and predicting storage stability of lactose- and protein-containing food and pharmaceutical materials.     

Mutant mice derived by ICSI of evaporatively dried spermatozoa exhibit expected phenotype

Apolipoprotein E (Apoe)-deficient knockout mice were used to test the hypothesis that mutant mice preserved as evaporatively dried (ED) spermatozoa, stored at -80?°C for 6 months, and then recovered by ICSI will exhibit the same phenotype as before preservation. The birth rate of mice recovered by ICSI of evaporatively dried spermatozoa was lower than that of fresh spermatozoa (17.5 vs 38.0%). Progeny of mice preserved using evaporatively dried spermatozoa were reproductively sound. From these, the second generation of mice produced by natural mating showed lesions typical of APOE deficiency, including severe hypercholesterolemia, hypertriglyceridemia, markedly increased plasma low-density lipoprotein level, and extensive and severe atherosclerotic lesions in the aorta. We conclude that the expected phenotype caused by an induced genetic mutation can be faithfully recapitulated and sustained in subsequent generations of mice preserved and stored as ED spermatozoa and recovered using ICSI. Because it is simpler, faster, and cheaper than conventional (cryopreservation) and nonconventional (freeze-drying) preservation procedures, evaporative drying is a viable, cost-effective, and efficient method for preserving and storing valuable mutant mouse strains.     

Quantitative determination of the protein content of milk by ultraviolet spectrophotometry. 3. Determination of proteins in preserved milk samples

It is reported upon the results of the quantitative estimation of protein content from preserved milk by means of ultraviolet spectrophotometry. In addition to the preservation by boric acid, bronopol, copper sulphate, potassium dichromate and ammonium peroxodisulphate storage at temperatures below 0 degrees C and freeze drying were tested. Besides bronopol and copper sulphate especially physical preservation methods proves fit for the protein estimation by measurements of absorbance at 210 nm, 235 and 280 nm or 210 and 220 nm. It is recommended to use solutions and filters of quartz with evaluated absorbance in daily calibrating of the spectrophotometer.     

Quality of fresh and stored foam mat dried Mandarin powder

Foam mat drying is a lucrative process of mandarin (kinnow) pulp preservation in the form of powder. Foam mat drying of mandarin pulp experiments were carried out at 65, 75 and 85 °C drying air temperatures using carboxy methyl cellulose, milk and egg white as foaming agents at different concentrations levels to get dried mandarin powder. Quality of the reconstituted dried Mandarin pulp‐powder was evaluated for 6 month storage studies at an interval of 2 months for total sugars (%), ascorbic acid (mg 100 mL^?1), total acid (%), pH and microbial load (fungal and bacterial) using standard procedures. It was observed that total sugars, ascorbic acid and total acid were decreased whereas pH was slightly higher than the fresh pulp. There was minor bacterial growth noticed in all the treatments, which is within the permissible limit, furthermore no fungal growth was noticed during storage period.     

贮藏温度对真空冻干发酵剂发酵乳杆菌grx07活性的影响

以真空冻干的发酵剂grx07为研究对象,通过测定该发酵剂在20、4、-20℃三种温度下贮藏的存活率、活菌数、水分活度、发酵活力及影响乳酸菌代谢活力的关键酶活(乳酸脱氢酶、β-半乳糖苷酶、ATP酶的酶活),来探讨不同的贮藏温度对发酵乳杆菌grx07菌粉活力的影响。结果表明,发酵剂grx07在20℃贮藏3个月时存活率低于1%;在4和-20℃保藏12个月时菌粉存活率分别为4.45%和51.05%。在-20℃贮藏12个月的活菌数仍能达到3.78×1011 cfu/g,菌粉水分活度为0.210;活化后发酵pH达到4.30,乳酸脱氢酶、β-半乳糖苷酶、ATP酶的活力分别为贮藏前酶活力的80.24%、74.60%、87.10%。因此,真空冻干发酵剂grx07长期贮藏的适宜温度为-20℃。     

Mathematical modeling of Escherichia coli inactivation under high-pressure carbon dioxide

Inactivation curves of Escherichia coli under high carbon dioxide pressures (2.5, 5.1, 7.6 and 10.1 MPa) at different temperatures (20, 30, 40 and 45 degrees C) were analyzed using the modified Gompertz model. The phase disappearance (time for complete inactivation of all cells, lambda) and the inactivation rate (mu) of E. coli were inversely related. Inactivation rates (mu) of E. coli were higher at 45 degrees C under 10.1 MPa CO2 pressure than at 25, 30 and 40 degrees C under 2.5, 5.1 and 7.6 MPa CO2 pressure. Increased pressure and temperature had significant effects on the survival of E. coli. The temperature dependence of the inactivation rate constant was analyzed based on the Arrhenius, linear and square-root models. The temperature sensitivity (high E(mu)) determined based on the Arrhenius model was higher at high temperatures. E(mu) (activation energy) value was -186.56 Kjoule/mol at 10.1 Mpa, and -137.24, -167.25 and -183.80 Kjoule/mol at 2.5, 5.1 and 7.6 MPa, respectively. Results of this study enable the prediction of microbial inactivation exposed to different CO2 pressures and temperatures.     

Effect of temperature and/or pressure on lactoperoxidase activity in bovine milk and acid whey

At atmospheric pressure, inactivation of lactoperoxidase (LPO) in milk and whey was studied in a temperature range of 69-73 degrees C and followed first order kinetics. Temperature dependence of the first order inactivation rate constants could be accurately described by the Arrhenius equation, with an activation energy of 635.3 +/- 70.7 kJ/mol for raw bovine milk and 736.9 +/- 40.9 kJ/mol for diluted whey, indicating a very high temperature sensitivity. On the other hand, LPO is very pressure resistant and not or only slightly affected by treatment at pressure up to 700 MPa combined with temperatures between 20 and 65 degrees C. Both for thermal and pressure treatment, stability of LPO was higher in milk than in diluted whey. Besides, a very pronounced antagonistic effect between high temperature and pressure was observed, i.e. at 73 degrees C, a temperature where thermal inactivation at atmospheric pressure occurs rapidly, application of pressure up to 700 MPa exerted a protective effect. At atmospheric pressure, LPO in diluted whey was optimally active at a temperature of about 50 degrees C. At all temperatures studied (20-60 degrees C), LPO remained active during pressure treatment up to 300 MPa, although the activity was significantly reduced at pressures higher than 100 MPa. The optimal temperature was found to shift to lower values (30-40 degrees C) with increasing pressure.     

Fluidised bed drying of soybeans

The fluidised bed drying characteristics of soybeans at high temperatures (110-140 degrees C) and moisture contents, 31-49% dry basis, were modelled using drying equations from the literature. Air speeds of 2.4-4.1 m/s and bed depths from 10 to 15 cm were used. The minimum fluidised bed velocity was 1.9 m/s. From a quality point of view, fluidised bed drying was found to reduce the level of urease activity which is an indirect measure of trypsin inhibitor, with 120 degrees C being the minimum required to reduce the urease activity to an acceptable level. Increased air temperatures caused increased cracking and breakage, with temperatures below 140 degrees C giving an acceptable level for the animal feed industry in Thailand. The protein level was not significantly reduced in this temperature range. The drying rate equations and quality models were then combined to develop optimum strategies for fluidised bed drying, based on quality criteria, drying capacity, energy consumption and drying cost. The results showed that from 33.3% dry basis, soybean should not be dried below 23.5% dry basis in the fluidised bed dryer, to avoid excessive grain cracking. The optimum conditions for minimum cost, minimum energy and maximum capacity coincided at a drying temperature of 140 degrees C, bed depth of 18 cm, air velocity of 2.9 m/s and fraction of air recirculated of 0.9. These conditions resulted in 27% cracking, 1.7% breakage and an energy consumption of 6.8 MJ/kg water evaporated.     

Inactivation of hepatitis A virus by high-pressure processing: the role of temperature and pressure oscillation

Inactivation of hepatitis A virus (HAV) in Dulbecco's modified Eagle medium with 10% fetal bovine serum was studied at pressures of 300, 350, and 400 MPa and initial sample temperatures of -10, 0, 5, 10, 20, 30, 40, and 50 degrees C. Sample temperature during pressure application strongly influenced the efficiency of HAV inactivation. Elevated temperature (> 30 degrees C) enhanced pressure inactivation of HAV, while lower temperatures resulted in less inactivation. For example, 1-min treatments of 400 MPa at -10, 20, and 50 degrees C reduced titers of HAV by 1.0, 2.5, and 4.7 log PFU/ml, respectively. Pressure inactivation curves of HAV were obtained at 400 MPa and three temperatures (-10, 20, and 50 degrees C). With increasing treatment time, all three temperatures showed a rapid initial drop in virus titer with a diminishing inactivation rate (or tailing effect). Analysis of inactivation data indicated that the Weibull model more adequately fitted the inactivation curves than the linear model. Oscillatory high-pressure processing for 2, 4, 6, and 8 cycles at 400 MPa and temperatures of 20 and 50 degrees C did not considerably enhance pressure inactivation of HAV as compared with continuous high-pressure application. These results indicate that HAV exhibits, unlike other viruses examined to date, a reduced sensitivity to high pressure observed at cooler treatment temperatures. This work suggested that slightly elevated temperatures are advantageous for pressure inactivation of HAV within foods.     

Effect of acid adaptation on inactivation of Salmonella during drying and storage of beef jerky treated with marinades

This study evaluated the influence of pre-drying marinade treatments on inactivation of acid-adapted or nonadapted Salmonella on beef jerky during preparation, drying and storage. The inoculated (five-strain composite, 6.0 log CFU/cm2) slices were subjected to the following marinades (24 h, 4 degrees C) prior to drying at 60 degrees C for 10 h and aerobic storage at 25 degrees C for 60 days: (1) no marinade, control (C), (2) traditional marinade (TM), (3) double amount of TM modified with added 1.2% sodium lactate, 9% acetic acid, and 68% soy sauce with 5% ethanol (MM), (4) dipping into 5% acetic acid and then TM (AATM), and (5) dipping into 1% Tween 20 and then into 5% acetic acid, followed by TM (TWTM). Bacterial survivors were determined on tryptic soy agar with 0.1% pyruvate and xylose-lysine-tergitol 4 (XLT4) agar. Results indicated that drying reduced bacterial populations in the order of pre-drying treatments TWTM (4.8-6.0 log CFU/cm2)> or =AATM> or =MM>TM> or =C (2.6-5.0 log CFU/cm2). Nonadapted Salmonella were significantly (P<0.05) more resistant to inactivation during drying than acid-adapted Salmonella in all treatments. Bacterial populations decreased below the detection limit (-0.4 log CFU/cm2) as early as 7 h during drying or remained detectable even after 60 days of storage, depending on acid adaptation, pre-drying treatment, and agar media. The results indicated that acid adaptation may not cause increased resistance of Salmonella to the microbial hurdles involved in jerky processing and that use of modified marinades in manufacturing jerky may improve the effectiveness of drying in inactivating Salmonella.     

Effect of thaw rates on survival of buffalo spermatozoa frozen straws

Eighteen ejaculates from three buffalo bulls of Nili-Ravi breed were tested in a 3 X 6 X 3 factorial experiment. Semen was extended in lactose-fructose-egg yolk-glycerol extender containing penicillin (1000 IU/ml) and streptomycin (1000 micrograms/ml). Semen was frozen in .5-ml polyvinyl chloride straws in liquid nitrogen vapor and stored in liquid nitrogen for 24 h. Straws were thawed at water bath temperatures of 0, 37, or 75 degrees C for 2 min, 15 s, and 9 s, respectively. At thawing bath temperature of 0, 37, or 75 degrees C, percentage of motile spermatozoa averaged 30, 40, and 50%. Differences were significant between thaw rates for initial postthaw motility, postthaw sperm survival at 37 degrees C, and absolute index of survival of spermatozoa. Bulls were also different for initial postthaw motility, postthaw sperm survival at 37 degrees C, and absolute index of survival of spermatozoa. Thaw rate of 75 degrees C for 9 s was superior to other rates.     

Reduction of Warmed-Over Flavor Volatiles from Freeze-Dried Lean by Supercritical CO2 Extraction

Supercritical carbon dioxide (SC-CO₂) was used to extract warmed-over flavor (WOF) volatiles from cooked, freeze-dried beef at 40°C and pressures of 10.3 MPa or 30 MPa after 2 days storage. WOF markers, hexanal, heptanal, octanal, nonanal, and 2,3-octanedione, were identified in the volatiles profile of precooked beef by dynamic headspace extraction and gas chromatography-mass spectrometry before and after CO₂ extraction. TBARS and levels of WOF markers increased over 2 days storage. There was a reduction in WOF markers at both extraction pressures. The higher pressure led to greater reduction of WOF markers (e.g., hexanal: 73.5%) than the lower pressure (e.g., hexanal: 60.3%), notably for heptanal and nonanal. SC-CO₂ may be applicable for reducing WOF volatiles from precooked meats.     

Pressure-shift freezing and its influence on texture,colour, microstructure and rehydration behaviour of potato cubes

Temperature changes during pressure-shift freezing (400 MPa) of potato cubes and its effects on the drip loss (weight and conductivity), texture (shear and compression tests), colour (L, a, b values), drying behaviour, rehydration properties (water uptake, texture after rehydration) and visible cell damage after thawing (micrographs) were investigated and compared with conventional freezing (0.1 MPa, -30 °C), subsequent frozen storage (-18 °C) or pressure treatment (400 MPa) at +15 :C. Pressure-shift freezing resulted in increased crystallization rates compared to conventional freezing at -30 °C. Crystallization and cooling to ?8 =C took 2.5 min during and after pressure release versus 17 min at atmospheric pressure. Drip loss was reduced from 12.0 to 10.8g/100g. Water uptake during 10 min of rehydration (93.9g/100g compared to 77.4g/100g and incomplete rehydration) and texture values were improved. Browning after thawing or after fluidized bed drying was reduced (increased a value, lower L value), suggesting partial enzyme inactivation during pressure treatment. Differences in colour and texture to the untreated controls were smaller after pressure-shift freezing than after conventional freezing. Cooling to ?30 °C after pressure-shift freezing did not significantly affect the results, whereas subsequent frozen storage at ?18 °C resulted in quality deterioration, as observed after frozen storage of conventionally frozen samples. The improved preservation of cell structure was demonstrated using scanning electron microscopy.