634. The determination of the coagulating power of commercial rennet extracts using an automatic tester

1956 ◽  
Vol 23 (2) ◽  
pp. 269-276 ◽  
Author(s):  
F. C. Storrs
Keyword(s):  
Experimental Error ◽  
Freeze Drying ◽  
Milk Powder ◽  
Automatic Apparatus ◽  
Instrument Error ◽  
Single Observation ◽  
Rennet Coagulation ◽  
Freeze Dried ◽  
Two Samples

1. A method for preparing rennet reference standards by freeze-drying is described.2. A substrate has also been developed using ordinary spray dried separated milk powder which will give reproducible results under specified conditions. These include:(i) A constant temperature (37° C.) for the duration of the test.(ii) The exclusion of added calcium ions until actual testing begins.(iii) The equilibration of the milk at 37° C. for 2 hr. before use.3. The construction and use of an automatic apparatus for recording rennet coagulation time is also described.4. The instrument error of a single observation is about 1·0%.5. With liquid rennet extracts, the total experimental error, based on one sample of three replicates, is 2% or less: with two samples, it is 1% or less.6. With freeze-dried rennet preparations, the experimental error with two ampoules, sampled thrice with three replicates per sample, was ±2·.0%. With three ampoules it was ±1% or less.

The effect of heat on the vitamin B6 of milk: II. A comparison of biological and microbiological tests of evaporated milk

1959 ◽  
Vol 26 (2) ◽  
pp. 215-220 ◽  
Author(s):  
Mary K. Davies ◽  
Margaret E. Gregory ◽  
Kathleen M. Henry
Keyword(s):  
Vitamin B6 ◽  
Experimental Error ◽  
Freeze Drying ◽  
Room Temperature ◽  
Raw Milk ◽  
Vitamin B ◽  
Experimental Conditions ◽  
Freeze Dried ◽  
Microbiological Research ◽  
Chick Diet

1. For chicks and rats pyridoxine, pyridoxal and pyridoxamine were equally active in terms of the free bases when given separately from the diet.2. Under our experimental conditions pyridoxine mixed with the chick diet was stable, but 20% of pyridoxamine, and a variable amount of pyridoxal was lost.3. The vitamin B6 activities measured with Saccharomyces carlsbergensis, chicks and rats respectively and expressed as μg. pyridoxine/g. freeze-dried milk were: raw milk 3·4, 3·2 and 4·9; evaporated milk 1·0, 2·1 and 2·7; stored evaporated milk 0·6, 1·4 and 2·0. For the chicks the milks were mixed with the diets; they were given separately to the rats.4. The microbiological and biological results for raw milk agreed within the limits of experimental error. For the processed milks the differences between biological and microbiological tests were statistically significant.5. All three methods of assay showed a 45–70% loss of vitamin B6 activity on processing and a further loss of 30% of the remainder after storage for 6 months at room temperature.We are indebted to Mr J. Rothwell, Department of Dairying, University of Reading, for preparing the evaporated milk and to Dr B. Record, Ministry of Supply, Microbiological Research Establishment, Porton, for freeze-drying the milk. We should like to thank Dr S. K. Kon for his interest in this work.

scholarly journals Quantitative histochemical determination of Na+ and K+ in microscopic samples using carbon furnace atomic absorption spectrometry.

1988 ◽  
Vol 36 (3) ◽  
pp. 237-244 ◽  
Author(s):  
I P Sussman ◽  
L C MacGregor ◽  
B R Masters ◽  
F M Matschinsky
Keyword(s):  
Atomic Absorption Spectrometry ◽  
Atomic Absorption ◽  
Freeze Drying ◽  
Absorption Spectrometry ◽  
Ion Diffusion ◽  
Histochemical Technique ◽  
Tissue Samples ◽  
Freeze Dried ◽  
Problem Data

Carbon furnace atomic absorption spectrometry was used to measure the Na and K content of freeze-dried microscopic tissue samples. This method was sufficiently sensitive to measure pmol amounts of Na and K from tissue weighing 10-60 ng. Within the spatial resolution of the microdissection procedure, ion diffusion that might occur during cryosectioning, freeze-drying, and dissection of the tissue did not seem to be a problem. Data obtained with this methodology were in agreement with previously reported values of the Na and K content of various tissues, thus supporting the usefulness of this quantitative histochemical technique.

A technique for evaluating reconstitution properties of milk powders

1973 ◽  
Vol 40 (2) ◽  
pp. 135-147
Author(s):  
T. C. Wyeth ◽  
G. C. Cheeseman
Keyword(s):  
Quantitative Data ◽  
Milk Powder ◽  
Skim Milk ◽  
The Other ◽  
Reproducible Technique ◽  
Freeze Dried ◽  
The Ideal

SummaryAn accurate and reproducible technique involving a continuous aqueous elution from a bed of dried-milk powder was developed to evaluate reconstitution characteristics. Quantitative data for the determination of reconstitution behaviour were obtained by analysis of the eluate for protein, lactose and Ca constituents. A reconstitution coefficient (P) was derived from the formula (W1+ΣWi)/T, where W1 was the amount reconstituted in the first eluate fraction, ΣWi the total amount reconstituted in 8 fractions, and T the time taken for 1/3 of the constituent to be reconstituted. Values obtained for P were thus related to the reconstitution properties and could be used to grade the powders. A freeze-dried skim-milk gave the ideal reconstitution behaviour with W1 values in the range 42·0–44·2, ΣWi values in the range 93·6–101·3, T values in the range 3·0–3·3 and reconstitution coefficients in the range 41·1–46·3 for the 3 constituents. All the other preparations tested gave lower values for W1 and P, although some gave ΣWi values in the same range, whilst all T values were higher than those for the freeze-dried sample.

scholarly journals Influence of k-casein genotype on heat stability and cheese making properties of milk powder

Mljekarstvo ◽  
2021 ◽  
pp. 269-280
Author(s):  
Alexandr Gennadyevich Kruchinin ◽  
Keyword(s):  
Spray Drying ◽  
Freeze Drying ◽  
Milk Powder ◽  
Heat Stability ◽  
Model Systems ◽  
Drying Method ◽  
Cheese Making ◽  
Rennet Coagulation ◽  
Ph Range ◽  
Physical And Chemical

In this study the effect of k-casein gene polymorphism on the technological characteristics of milk powder obtained by spray (AA1:BB1) and freeze drying (AA2:BB2) was investigated. Standardized and generally accepted methods were used in the field of physical and chemical control of dairy products, as well as methods for assessing the heat stability and cheese making properties of milk. The most heat-resistant were the samples with a predominance of milk obtained from cows with the AA CSN3 genotype, in the pH range from 6.4 to 7.0 (36-91 minutes for AA1:BB1 and 37-101 minutes for AA2:BB2). In systems with a fraction of 25 % to 100 % of milk from cows with the AA CSN3 genotype obtained by freeze drying, higher (by 3-10 %) stabilization qualities of protein were revealed when heated in the pH range from 6.4 to 7.0 compared to spray drying. The analysis of the results regarding the cheese making properties showed that with an increase in the proportion of milk from cows with the BB CSN3 genotype from 0 % to 100 % in model systems, the rennet coagulation time decreases for all samples, regardless of the drying method. It was also found that when using freeze drying, coagulum of all samples were assigned to the highest class of milk quality in terms of cheese making properties, while during spray drying only the samples consisting of min. 75 % or completely of milk obtained from cows with genotype BB CSN3 corresponded to this category.

Suitability of tritiated inulin for determination of glomerular filtration rate

1991 ◽  
Vol 260 (2) ◽  
pp. F283-F289 ◽  
Author(s):  
M. Shalmi ◽  
H. E. Lunau ◽  
J. S. Petersen ◽  
M. Bak ◽  
S. Christensen
Keyword(s):  
Aqueous Solution ◽  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Freeze Drying ◽  
Chromatographic Method ◽  
Freeze Dried ◽  
Chromatographic Profile ◽  
Subsequent Storage

Purity of different batches of [3H]inulin delivered from leading manufacturers was elevated with a chromatographic method (Sephadex G-25 column) that allowed simultaneous analysis of cold inulin, [3H]inulin, and [14C]inulin in the same run. Among four batches of [3H]inulin received within 5 mo, two were found relatively pure, whereas two were partly decomposed to lower-molecular-weight fragments. The chromatographic profile of pure isotopes was not significantly affected by redistribution and freeze drying, nor by subsequent storage in the freeze-dried state at -20 degrees C for up to 5 mo, nor by incubation in aqueous solution at 37 degrees C for 24 h. Three batches of [3H]inulin with different grades of decomposition (noninulin percentages 13%, 38%, and 61%, respectively) were selected for clearance experiments and infused simultaneously with cold and undecomposed [14C]inulin to conscious rats. [14C]inulin had a significantly higher clearance than cold inulin (+7.6 +/- 0.6%) and relatively pure [3H]inulin (+12.4 +/- 0.4%). Decomposed [3H]inulin isotopes progressively underestimated clearance of cold inulin to an extent related to the degree of decomposition. Thus at the end of the 5-h clearance experiment, ratios between clearance of tracer and of cold inulin were 0.92, 0.71, and 0.60 for the three 3H isotopes, respectively. This study indicates that [3H]inulin delivered from leading manufacturers may be decomposed to an extent that invalidates its use as a marker for glomerular filtration rate (GFR). It is thus necessary to check the purity routinely before use. Within the same rat, clearance of undecomposed [3H]inulin and [14C]inulin may differ by 12%, and for this reason they should not be used interchangeably as GFR markers.

Method for the Determination of Aflatoxin M1 in Fluid Milk and Milk Products

1973 ◽  
Vol 56 (6) ◽  
pp. 1431-1436 ◽  
Author(s):  
Walter A Pons ◽  
Alva F Cucullu ◽  
Louise S Lee
Keyword(s):  
Neutral Lipids ◽  
Milk Powder ◽  
Aflatoxin M1 ◽  
Reliable Determination ◽  
Milk Products ◽  
Average Recovery ◽  
Acetone Water ◽  
Freeze Dried ◽  
Fluid Milk

Abstract The method described utilizes acetone-water (77+23) for extraction of M1 from milk and milk products in a 3 min blender extraction. Phospholipids and soluble proteins in the primary extract are removed by treatment with lead acetate, and residual neutral lipids in the treated extract are removed by partition into hexane. Aflatoxin M1 is partitioned into chloroform, which is then washed with salt solution, and the chloroform is evaporated. The residue is dissolved in chloroform, and M1 is resolved on silica gel-coated plates developed in chloroform-acetone-2-propanol (850+100+50). This basic procedure is applicable to fluid milk and reconstituted freeze-dried milk powder at levels as low as 0.1 μg M1/L. Extracts of nonfat dry milk, evaporated and condensed milk, and cheeses, which require further cleanup before TLC, are purified on a cellulose-aqueous methanol partition column to allow reliable determination of M1 at levels as low as 0.2 Mg/L or kg. Average recovery of M1 added to fluid milk at levels of 0.1–1.0 μg/L was 106% without the use of the cleanup column and 90% when the column was used to purify the extracts. Average recovery of M1 added to other milk products at a level of 0.2 Mg/L or kg was 88%. The precision of the method (coefficient of variation) was estimated to be ±16% at 0.2 Mg/L in fluid milk, and ±4% at a 34 Mg/kg level in contaminated freeze-dried milk.

Scanning Electron Microscopy-cuticular Lesions on the Roundworm Ascaris Suum

1970 ◽  
Vol 28 ◽  
pp. 114-115
Author(s):  
P. A. Madden ◽  
W. R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Freeze Drying ◽  
Room Temperature ◽  
Secondary Electron ◽  
Distilled Water ◽  
Freeze Dried ◽  
Silver Paint ◽  
To Come ◽  
Scanning Electron

The intestinal roundworm of swine is pinkish in color and about the diameter of a lead pencil. Adult worms, taken from parasitized swine, frequently were observed with macroscopic lesions on their cuticule. Those possessing such lesions were rinsed in distilled water, and cylindrical segments of the affected areas were removed. Some of the segments were fixed in buffered formalin before freeze-drying; others were freeze-dried immediately. Initially, specimens were quenched in liquid freon followed by immersion in liquid nitrogen. They were then placed in ampuoles in a freezer at −45C and sublimated by vacuum until dry. After the specimens appeared dry, the freezer was allowed to come to room temperature slowly while the vacuum was maintained. The dried specimens were attached to metal pegs with conductive silver paint and placed in a vacuum evaporator on a rotating tilting stage. They were then coated by evaporating an alloy of 20% palladium and 80% gold to a thickness of approximately 300 A°. The specimens were examined by secondary electron emmission in a scanning electron microscope.

Revealing gross three-dimensional structure in the SEM

1987 ◽  
Vol 45 ◽  
pp. 656-657
Author(s):  
Sterling P. Newberry
Keyword(s):  
Freeze Drying ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Small Object ◽  
Final Solution ◽  
Dimensional Representation ◽  
X Ray ◽  
Three Dimensional Representation ◽  
Freeze Dried ◽  
Critical Point Drying

The beautiful three dimensional representation of small object surfaces by the SEM leads one to search for ways to open up the sample and look inside. Could this be the answer to a better microscopy for gross biological 3-D structure? We know from X-Ray microscope images that Freeze Drying and Critical Point Drying give promise of adequately preserving gross structure. Can we slice such preparations open for SEM inspection? In general these preparations crush more readily than they slice. Russell and Dagihlian got around the problem by “deembedding” a section before imaging. This some what defeats the advantages of direct dry preparation, thus we are reluctant to accept it as the final solution to our problem. Alternatively, consider fig 1 wherein a freeze dried onion root has a window cut in its surface by a micromanipulator during observation in the SEM.

Reduction of Potassium in Kidney Proximal Tubules to Aid in Electron Probe X-Ray Microanalysis of Calcium

1985 ◽  
Vol 43 ◽  
pp. 474-475
Author(s):  
A. LeFurgey ◽  
P. Ingram ◽  
L.J. Mandel
Keyword(s):  
Smooth Muscle ◽  
Proximal Tubule ◽  
Electron Probe ◽  
Clinical Applications ◽  
Proximal Tubules ◽  
Rabbit Kidney ◽  
Target Cells ◽  
X Ray ◽  
Freeze Dried

For quantitative determination of subcellular Ca distribution by electron probe x-ray microanalysis, decreasing (and/or eliminating) the K content of the cell maximizes the ability to accurately separate the overlapping K Kß and Ca Kα peaks in the x-ray spectra. For example, rubidium has been effectively substituted for potassium in smooth muscle cells, thus giving an improvement in calcium measurements. Ouabain, a cardiac glycoside widely used in experimental and clinical applications, inhibits Na-K ATPase at the cell membrane and thus alters the cytoplasmic ion (Na,K) content of target cells. In epithelial cells primarily involved in active transport, such as the proximal tubule of the rabbit kidney, ouabain rapidly (t1/2= 2 mins) causes a decrease2 in intracellular K, but does not change intracellular total or free Ca for up to 30 mins. In the present study we have taken advantage of this effect of ouabain to determine the mitochondrial and cytoplasmic Ca content in freeze-dried cryosections of kidney proximal tubule by electron probe x-ray microanalysis.

Stoichiometric Determination of Graphite Intercalation Compounds Using Rutherford Backscatiering Spectrometry

1983 ◽  
Vol 27 ◽  
Author(s):  
L. Salamanca-Riba ◽  
B.S. Elman ◽  
M.S. Dresselhaus ◽  
T. Venkatesan
Keyword(s):  
Experimental Error ◽  
Rutherford Backscattering Spectrometry ◽  
Rutherford Backscattering ◽  
Intercalation Compounds ◽  
Graphite Intercalation Compounds ◽  
X Ray ◽  
Donor And Acceptor ◽  
Graphite Intercalation ◽  
Non Destructive

ABSTRACTRutherford backscattering spectrometry (RBS) is used to characterize the stoichiometry of graphite intercalation compounds (GIC). Specific application is made to several stages of different donor and acceptor compounds and to commensurate and incommensurate intercalants. A deviation from the theoretical stoichiometry is measured for most of the compounds using this non-destructive method. Within experimental error, the RBS results agree with those obtained from analysis of the (00ℓ) x-ray diffractograms and weight uptake measurements on the same samples.

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