Thermistor Cryoscopic Determination of the Freezing Point Value of Milk Produced in North America

1969 ◽  
Vol 52 (1) ◽  
pp. 142-151
Author(s):  
R W Henningson
Keyword(s):  
Standard Deviation ◽  
Freezing Point ◽  
Simple Linear Regression ◽  
Milk Samples ◽  
Statistical Procedures ◽  
Significant Relationships ◽  
Added Water ◽  
The Mean ◽  
Canadian Provinces

Abstract A survey of the freezing point value of 660 milk samples, known to contain no added water, taken from dairying areas in 22 States and 4 Canadian Provinces was conducted during late spring of 1968. The data collected were subjected to analysis of variance and simple linear regression statistical procedures and tested for significant relationships and differences at the 5 and 1% levels. The mean freezing point value for all samples was estimated as —0.5404°C with a standard error of 0.0003°C and a standard deviation of —0.00676°C. Thirty-five (5.3%) of 660 samples yielded freezing point values of —0.530°C or higher; twenty-five (3.8%) yielded a freezing point value of —0.551°C or lower. Significant differences were found among mean freezing point values for States and for breeds.

Regulatory Agency Acceptance of the Interpretation of the Freezing Point Value of Milk as Part of the Official Thermistor Cryoscopic Method

1970 ◽  
Vol 53 (3) ◽  
pp. 539-542
Author(s):  
R W Henningson
Keyword(s):  
Milk Sample ◽  
North American ◽  
Freezing Point ◽  
Sample Survey ◽  
Regulatory Agencies ◽  
A Value ◽  
Added Water ◽  
The Mean ◽  
Definition Of

Abstract A 1968 North American authentic milk sample survey determined that the mean freezing point value of milk is –0.5404°C. Statistical concepts permit the calculation of a value, –0.525°C, 2.326 standard deviations from a mean with 95% confidence that 99% of all subsequent observations will be below the value. Based on this survey, it was recommended that the Interpretation of the freezing point value of milk be made a part of the official final action thermistor cryoscopic method for the determination of the freezing point value of milk, and include the following: an upper limit for the freezing point value of milk, an official definition of an authentic milk sample, and a logical procedure for the confirmation of added water. A copy of the report and an explanatory letter were sent to approximately 100 North American regulatory agencies. Reports were received from 49 regulatory agencies with 39 favoring the recommendations, 6 opposing the recommendations, and 4 having no opinion. It is recommended that the Interpretation of the freezing point of milk be included in both the thermistor cryoscopic and the Hortvet methods.

Cryoscopy of Milk: Effect of Variations in the Method

1966 ◽  
Vol 49 (3) ◽  
pp. 511-515 ◽  
Author(s):  
R W Henningson
Keyword(s):  
Statistical Analysis ◽  
Sample Size ◽  
Freezing Point ◽  
Collaborative Study ◽  
Sample Temperature ◽  
Milk Samples ◽  
Two Samples ◽  
Temperature Rate

Abstract Bath level, sample temperature, rate of stirring, degree of supercooling, sample size, sample isolation, and refreezing of the sample were the variables in the thermistor cryoscopic method for the determination of the freezing point value of milk chosen for study. Freezing point values were determined for two samples of milk and two secondary salt standards utilizing eight combinations of the seven variables in two test patterns. The freezing point value of the salt standards ranged from –0.413 to –0.433°C and from –0.431 to –0.642°C. The freezing point values of the milk samples ranged from –0.502 to –0.544°C and from –0.518 to –0.550°C. Statistical analysis of the data showed that sample isolation was a poor procedure and that other variables produced changes in the freezing point value ranging from 0.001 to 0.011°C. It is recommended that specific directions be instituted for the thermistor cryoscopic method, 15.040–15.041, and that the method be subjected to a collaborative study.

89. Seasonal Variation of the Percentage Butterfat Content of Milk. An Examination of the Results of Certain Individual Cow Tests

1935 ◽  
Vol 6 (1) ◽  
pp. 1-5 ◽  
Author(s):  
C. D. Oxley
Keyword(s):  
Seasonal Variation ◽  
Standard Deviation ◽  
Seasonal Variability ◽  
Milk Samples ◽  
Sources Of Error ◽  
The Mean ◽  
Morning Milk

Figures showing the means and the standard deviation of butterfat percentage of milk samples, at the afternoon and morning milkings res-pectively, during the four quarters of the year are presented.The probable sources of error due to the nature of the sample are discussed and the seasonal variability of mean and of standard deviation is considered.The likelihood of the mean of afternoon or of morning milk failing to reach certain specified minima during the respective seasons is calculated.

Determination of Maleic Hydrazide Residues in Tobacco and Vegetables

1973 ◽  
Vol 56 (5) ◽  
pp. 1164-1172
Author(s):  
Milan Ihnat ◽  
Robert J Westerby ◽  
Israel Hoffman
Keyword(s):  
Standard Deviation ◽  
Present Method ◽  
Maleic Hydrazide ◽  
Collaborative Study ◽  
Official Method ◽  
Sample Weight ◽  
Relative Standard ◽  
The Mean ◽  
Pipe Tobacco

Abstract The distillation-spectrophotometric method of Hoffman for determining maleic hydrazide has been modified to include a double distillation and was applied to the determination of 1–30 ppm maleic hydrazide residues in tobacco and vegetables. Recoveries of 1–23 μg added maleic hydrazide were independent of weight of maleic hydrazide, but did depend on sample and sample weight. The following recoveries were obtained from 0.5 g sample: pipe tobacco, 84%; commercially dehydrated potato, 83%; cigar tobacco, 81%; dried potato, 76%; fluecured tobacco, 73%; dried carrot, 71%. In the absence of sample, the recovery was 82%. When appropriate standard curves were used, maleic hydrazide levels determined in tobacco samples were essentially independent of sample weight in the range 0.1–3 g. The mean relative standard deviation for a variety of field-treated and fortified tobacco samples containing 1–28 ppm maleic hydrazide was 3%. The precision and sensitivity of this procedure seem to be substantial improvements over official method 29.111–29.117. It is recommended that the present method be subjected to a collaborative study.

Determination of the Freezing Point of Milk by Thermistor Cryoscopy

1967 ◽  
Vol 50 (3) ◽  
pp. 533-537
Author(s):  
R W Henningson
Keyword(s):  
Freezing Point ◽  
Official Method ◽  
Milk Samples ◽  
Present Official Method ◽  
Proper Condition

Abstract Specific directions for the thermistor cryoscopic method, including uniformity in cooling, degree of supercooling, seeding, and reading procedures, are proposed for the present official method. It is emphasized that the instrument must be in the proper condition for use, must be properly calibrated, and must be properly utilized by the analyst. Each analyst should individually calibrate with standards by the same uniform procedure for standards and milk samples. The precautions necessary in the determination are part of the method and must be observed if the same sample is to yield the same freezing point value for different analysts, in different laboratories, at different times

Fluorometric Determination of Selenium in Foods

1974 ◽  
Vol 57 (2) ◽  
pp. 368-372 ◽  
Author(s):  
Milan Ihnat
Keyword(s):  
Standard Deviation ◽  
Milk Powder ◽  
Skim Milk ◽  
Skim Milk Powder ◽  
Food Samples ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Relative Standard ◽  
The Mean

Abstract A fluorometric method using 2,3-diaminonaphthalene for estimating selenium has been evaluated with regard to its applicability to food samples. Charring of the sample during digestion appeared to result in losses of native and added selenium from some samples, so a modified wet digestion procedure was introduced. Digestion first in nitric acid followed by a mixture of nitric-perchloric-sulfuric acids substantially reduced the incidence of sample charring for a variety of foods. The mean apparent recovery of selenium added as selenite or selenate at 100 and 500 ng levels to 0.1 and 1.0 g corn cereal, skim milk powder, and meat and 0.1 g fish was 101.0%; the actual recovery of the same levels of selenium from standard solutions was 96.6%. For a variety of samples containing 5—750 ng native or added selenium, the standard deviation as 4.7 + 1.95 X 10-2W ng, where W = ng selenium in the sample taken for analysis. The relative standard deviation (RSD) as a function of selenium weight (ng) was 50% (10), 6.7% (100), 4.3% (200), 3.1% (400), 2.7% (600), and 2.5% (800). The detection limit (weight of selenium at which RSD = 50%) was 10 ng at a mean blank level of 25 ng.

Radioisotope Dilution Technique for Determination of Vitamin B12 in Foods

1982 ◽  
Vol 65 (1) ◽  
pp. 85-88 ◽  
Author(s):  
Patrick J Casey ◽  
Keevin R Speckman ◽  
Frank J Ebert ◽  
William E Hobbs
Keyword(s):  
Standard Deviation ◽  
Vitamin B12 ◽  
Relative Standard Deviation ◽  
Extraction Procedure ◽  
Dilution Technique ◽  
Microbiological Method ◽  
Relative Standard ◽  
Wide Range ◽  
The Mean

Abstract A radioisotope dilution (RID) method for the determination of vitamin B12 is presented. The method combines a standard extraction procedure (AOAC 43.108,12th ed.) with a commercially available RID assay kit. The method was evaluated on a wide range of fortified and unfortified food products. Recovery studies on both groups yielded average recoveries of 98.1 and 95.8%, respectively. Reproducibility data generated from replicate analyses on both groups gave a relative standard deviation of 6.9% for the fortified group and 9.2% for the unfortified group. For the samples studied, the mean vitamin B12 content determined by the RID method was 8.01 μg/100 g vs imean of 7.54 μg/100 g by the AOAC microbiological method; the correlation coefficient was r = 0.983.

FREEZING POINT VALUES AND MILK SOLIDS-NOT-FAT CONTENT OF RETAIL MILK1

1961 ◽  
Vol 24 (2) ◽  
pp. 48-52 ◽  
Author(s):  
R. W. Henningson
Keyword(s):  
Freezing Point ◽  
Fat Content ◽  
Freezing Point Depression ◽  
Processing Plants ◽  
Added Water ◽  
Milk Solids ◽  
Area Data

Observed freezing point and milk solids-not-fat values were determined for approximately 400 retail samples. Most of these samples were systematically collected at monthly intervals over a calendar year from designated processing plants. The average observed freezing point value found was −0.529°C. The average MSNF value found was 8.88%. No relationship was expected, or found, between the observed freezing point value and the MSNF value of milks. The MSNF value did not assist in explaining high freezing point values or in confirming the presence of added water. It did prevent suspicion which could not be easily confirmed. A minimum freezing point depression standard, based on area data and administered in a manner similar to a minimum butterfat standard, appears to be the most feasible way of utilizing the cryoscopic method for the determination of added water in milk.

The use of single or composite milk samples for the determination of fat

1968 ◽  
Vol 35 (2) ◽  
pp. 291-294 ◽  
Author(s):  
M. G. O'Keeffe
Keyword(s):  
Analysis Of Variance ◽  
Fat Percentage ◽  
Milk Samples ◽  
Bulk Milk ◽  
Testing Accuracy ◽  
The Mean ◽  
Composite Samples

SummarySamples were tested for fat percentage from every consignment of herd bulk milk from 10 herds over a period of 12 months. The mean monthly within-herd variance was 0·043. Also, triplicate samples were taken from 8 herd bulk supplies for 8 days and tested in duplicate and an analysis of variance was applied to the within-herd fat percentage in order to find the contribution sampling, testing and biological variances. It is shown that when dealing with tanker-collected milk where composite samples are not used the testing accuracy is secondary to frequency of sampling. By combining the variances in the formulae given, the accuracy of different systems may be obtained and compared using either single tested or composite samples.

A simple spectroturbidimetric method for the determination of the fat content of homogenized ice-cream mixes

1962 ◽  
Vol 29 (1) ◽  
pp. 47-53 ◽  
Author(s):  
J. D. S. Goulden ◽  
P. Sherman
Keyword(s):  
Standard Deviation ◽  
Ice Cream ◽  
Fat Content ◽  
Fat Globule ◽  
The Mean ◽  
Simple Filter

SummaryA rapid spectroturbidimetric method for the determination of the fat content of homogenized ice-cream mixes using a simple filter absorptiometer has been devised. Turbidities are measured at two different wavelengths to allow for changes in the degree of homogenization. The standard deviation of the differences from the values obtained by the Werner-Schmid method was found to be 2·5% of the mean fat content value. The method also enables the mean fat globule diameter to be determined.

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