Collaborative Study of Rapid Methods for Alkaline Phosphatase in Milk and Cream

1979 ◽  
Vol 42 (10) ◽  
pp. 800-803 ◽  
Author(s):  
G. K. MURTHY ◽  
J. T. PEELER
Keyword(s):  
Alkaline Phosphatase ◽  
Limit Of Detection ◽  
Collaborative Study ◽  
Colorimetric Method ◽  
Skim Milk ◽  
Rapid Test ◽  
Raw Milk ◽  
Colorimetric Test ◽  
Photoelectric Colorimeter

Determination of alkaline phosphatase activity in milk and cream by the modified Scharer rapid test with use of photoelectric colorimeter for measuring absorbance was collaboratively studied. Milk samples (skim milk. milk and cream) with and without added raw milk were sent to 12 collaborators to be tested by (a) the modified Scharer rapid test using commercial standards and phenol standards for comparing colors, (b) the rapid colorimetric test and (c) the Rutgers method. The latter method was used for comparison only. In the modified Scharer rapid test, based on the category of standards, 73.3% of the samples using the commercial standards and 71.6% of the samples using phenol standards were correctly diagnosed. When the scoring was based on positive or negative, 98.4 and 92.6% of the samples were correctly diagnosed. Results with the phenol standards were significantly lower than those observed with the commercial standards. There were no false-positive results, as all incorrect readings were below limit of detection. Most of the errors occurred when the expected value was 1.0 μg phenol/ml. Results were 100% correct for the Rutgers method, but there are only two choices for this method, and they correspond to positive or negative. Compared to the theoretical values, data obtained by the colorimetric method ranged from 1.5 to 18.1% high, with a coefficient of variation of 4.4 to 13.4%. These variations were assumed satisfactory considering the levels at which phosphatase was tested.

Fluorometric Determination of Alkaline Phosphatase in Fluid Dairy Products: Collaborative Study

1990 ◽  
Vol 73 (6) ◽  
pp. 842-849 ◽  
Author(s):  
Richard M Rocco
Keyword(s):  
Alkaline Phosphatase ◽  
Dairy Products ◽  
Collaborative Study ◽  
Skim Milk ◽  
Raw Milk ◽  
Chocolate Milk ◽  
Phenyl Phosphate ◽  
Whole Milk ◽  
Standard Deviations

Abstract Official methods for the measurement of alkaline phosphatase (ALP) in dairy products use either phenyl phosphate or phenolphthaleln monophosphate as substrate. Quantitation of results requires butanol extraction of the Indophenol (Scharer) or 3-h dialysis of the liberated phenolphthaleln (Rutgers). The Advanced Fluorophos® assay Is based on a self-indicating substrate which, when acted upon by ALP, loses a phosphate radical and becomes a highly fluorescent compound. The rate of fluorophore formation Is monitored for 3 mln In a fluorometer and the enzyme activity In mU/L Is calculated. Eight laboratories participated in a collaborative study to evaluate the Fluorophos® assay for determining ALP activity In whole milk, skim milk, chocolate milk, and cream (half and half). The comparative method was the AOAC quantitative phenyl phosphate method, 16.121-16.122 (14th Ed.). Mixed herd raw milk was added to pasteurized samples at 0.05, 0.1, and 0.2% (v/v). Method performance at 0.1% (v/v) added raw milk as measured by repeatability and reproducibility standard deviations (sr and sR) and relative standard deviations (RSDr and RSDR), respectively, were: whole milk, sr = 21.7%, sR = 34.6%, RSDr = 4.4%, RSDR = 7.0%; skim milk, sr = 19.2%, sR = 31.4%, RSDr = 3.8%, RSDR = 6.2%; chocolate milk, sr = 27.6%, sR = 45.8%, RSDr = 5.3%, RSDR = 8.8%. The method has been adopted official first action by AOAC for determination of alkaline phosphatase in whole milk, skim milk, and chocolate milk.

Rapid Colorimetric Test for Alkaline Phosphatase in Dairy Products

1979 ◽  
Vol 42 (10) ◽  
pp. 794-799 ◽  
Author(s):  
G. K. MURTHY ◽  
R. MARTIN ◽  
U. S. RHEA ◽  
J. T. PEELER
Keyword(s):  
Alkaline Phosphatase ◽  
Dairy Products ◽  
Rapid Test ◽  
Raw Milk ◽  
Visual Observation ◽  
Visual Methods ◽  
Visual Examination ◽  
Colorimetric Test ◽  
Photoelectric Colorimeter ◽  
Hydrolysis Of

The Scharer rapid test for measuring alkaline phosphatase activity in milk and milk products was modified to include a photoelectric colorimeter in place of visual observation of color. Dairy products containing various amounts of added enzyme (3–15 μg phenol/ml or g) were prepared for analysis as per standard methods and analyzed by the rapid colorimetric test. A linear relationship was found between the percent of raw milk added and the enzyme activity with a correlation coefficient (r) range of 0.963 to 1.000. Hydrolysis of the substrate (disodium phenyl phosphate) by the surviving enzyme in different dairy products was similar. Recovery of the added enzyme varied, depending on the nature of the product. The method is quantitative, reproducible, and can be used as a rapid confirmatory procedure. Similarly, this method was applied to differentiating residual and reactivated enzyme in milk, cream and buttermilk. Compared to the Scharer rapid and the Rutgers visual methods, this test was more reliable in borderline cases because it eliminated the bias encountered in visual examination. A method was developed to analyze alkaline phosphatase in casein.

Collaborative Study of Alkaline Phosphatase Activity in Filter Paper Disks Impregnated with Skim Milk: Positive Control Sample

1982 ◽  
Vol 45 (2) ◽  
pp. 112-114 ◽  
Author(s):  
G. K. MURTHY ◽  
J. T. PEELER
Keyword(s):  
Alkaline Phosphatase ◽  
Phosphatase Activity ◽  
Alkaline Phosphatase Activity ◽  
Filter Paper ◽  
Room Temperature ◽  
Collaborative Study ◽  
Control Sample ◽  
Skim Milk ◽  
Positive Control ◽  
Colorimetric Test

The rapid colorimetric test was used in a collaborative study to determine alkaline phosphatase activity in filter paper disks impregnated with skim milk then dried and stored for several months at room temperature. Five samples of filter paper disks (0 to 6 μg phenol/disk) in duplicate were sent to six collaborators for analysis. Computations of analytical and analyst errors showed variations of 22.2 to 48.8%. Most of the variations were due to differences among analysts, but some were partly due to differences in the slopes of the calibration curves (a = 0.05 level) they prepared at the time of analysis. Collaborator's performance was evaluated by comparing % correct results that were positive (negative) with the expected results. About 95% of the samples were correctly analyzed.

Determination of Alkaline Phosphatase in Casein: Collaborative Study

1981 ◽  
Vol 64 (3) ◽  
pp. 623-627
Author(s):  
Gopala K Murthy ◽  
James T Peeler ◽  
◽  
E E Bone ◽  
B Dickerson ◽  
...  
Keyword(s):  
Alkaline Phosphatase ◽  
Phosphatase Activity ◽  
Collaborative Study ◽  
Magnesium Acetate ◽  
Colorimetric Test

Abstract A collaborative study was made to determine alkaline phosphatase in casein samples by the rapid colorimetric test. Six to eight collaborators tested 10 unknown casein samples containing various amounts of residual phosphatase with and without the addition of magnesium acetate. Results indicated that magnesium acetate significantly increased phosphatase activity. The collaborators correctly analyzed 95% of the samples with the added magnesium acetate. The method has been adopted official first action.

Rapid Methods for Differentiating Reactivated from Residual Phosphatase in Milk and Cream: Collaborative Study

1979 ◽  
Vol 62 (4) ◽  
pp. 822-827
Author(s):  
Gopala K Murthy ◽  
James T Peeler
Keyword(s):  
Magnesium Chloride ◽  
Collaborative Study ◽  
Control Sample ◽  
Rapid Test ◽  
Magnesium Acetate ◽  
Visual Methods ◽  
Test Results ◽  
Milk Samples ◽  
Colorimetric Test ◽  
Photoelectric Colorimeter

Abstract Three methods for differentiating reactivated from residual phosphatase in milk and cream were collaboratively tested using both magnesium acetate and magnesium chloride for reactivating phosphatase. The methods evaluated were the modified Scharer rapid test, the rapid colorimetric test, and the Rutgers method. Nine collaborators tested 6 unknown milk samples containing reactivated and/or residual phosphatase, and 16 collaborators tested 6 unknown cream samples containing reactivated and/or residual phosphatase. Results indicated that use of magnesium acetate in place of magnesium chloride for reactivating phosphatase improved test results. Visual tests (modified Scharer rapid and Rutgers) predicted correct results when the samples contained high levels of reactivated or residual phosphatase. In borderline cases where the reactivated phosphatase contents of the undiluted control sample and the diluted sample containing Mg were very close, the test results of the visual methods were significantly different from 100% correct results at the α = 0.05 level. Use of a photoelectric colorimeter or its equivalent for measuring the absorbance in conjunction with the modified Scharer rapid test improved results considerably. The modified Scharer rapid test was adopted official first action.

Colorimetric Determination of Hydroxyproline as Measure of Collagen Content in Meat and Meat Products: NMKL Collaborative Study

1990 ◽  
Vol 73 (1) ◽  
pp. 54-57 ◽  
Author(s):  
Kurt Kolar
Keyword(s):  
Collaborative Study ◽  
Colorimetric Method ◽  
Meat Products ◽  
Acid Oxidation ◽  
Colorimetric Determination ◽  
Mean Values ◽  
Collaborative Studies ◽  
Freeze Dried ◽  
Analytical Result

Abstract A colorimetric method for the determination of hydroxyproline as a measure of collagen in meat and meat products has been collaboratively studied in 18 laboratories. The method includes hydrolysis with sulfuric acid, oxidation with chloramine- T, and formation of a reddish purple complex with 4- dimethylaminobenzaldehyde. Five frozen and 3 freeze-dried samples were tested, ranging in content from 0.11 to 0.88% and from 0.39 to 4.0% hydroxyproline, respectively. The mean values of 2 identical samples were 0.245 and 0.251 %. The average recovery from a spiked sample was 96.1 %. The hydroxyproline content of a known sample (a mixture of 2 samples in the ratio 5:2) was calculated to 1.42%, which agrees well with the analytical result, 1.40%. In comparison with other collaborative studies, based on the ISO analytical method, the repeatability and reproducibility of this method agree well with the other results. This method was accepted as an official NMKL method by all national Committees, and has been adopted official first action by AOAC as an NMKLAOAC method.

scholarly journals Indirect and Direct Determination of the Casein Content of Milk by Kjeldahl Nitrogen Analysis: Collaborative Study

1998 ◽  
Vol 81 (4) ◽  
pp. 763-774 ◽  
Author(s):  
Joanna M Lynch ◽  
David M Barbano ◽  
J Richard Fleming
Keyword(s):  
Standard Deviation ◽  
Nitrogen Content ◽  
Relative Standard Deviation ◽  
Collaborative Study ◽  
Direct Determination ◽  
Raw Milk ◽  
Method Performance ◽  
Relative Standard ◽  
Milk Casein

Abstract The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42- 3.05℅ by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen ⨯ 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, SR = 0.016, repeatability relative standard deviation (RSDr) = 1.287℅, reproducibility relative standard deviation (RSDR) = 2.146%; indirect casein method (wt℅), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560℅, RSDR = 0.841; direct casein method (wt℅), mean = 2.575, sr = 0.015, sR = 0.025, RSDr = 0.597℅, RSDR = 0.988℅. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21,991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC INTERNATIONAL.

Collaborative Study Using a ZDBT Colorimetric Method for the Determination of Copper in Alcoholic Products

1967 ◽  
Vol 50 (2) ◽  
pp. 334-338
Author(s):  
Duane H Strunk ◽  
A A Andreasen
Keyword(s):  
Sulfuric Acid ◽  
Carbon Tetrachloride ◽  
Collaborative Study ◽  
Colorimetric Method ◽  
Good Precision ◽  
Determination Of Copper

Abstract Results are given on a collaborative study in which a zinc dibenzyldithiocarbamate (ZDBT) colorimetric method is used to measure copper in alcoholic products such as high wine, spirits, gin, whisky, brandy, rum, and wine. In this method, the sample is made ca 0.SN with sulfuric acid, and carbon tetrachloride containing 0.2% ZDBT is added. The colored copper-ZDBT complex is extracted in the carbon tetrachloride and measured at 438 mμ against a similar carbon tetrachloride extract of a blank. Data show good precision, and it is recommended that the ZDBT method be adopted as official, first action.

Sensitive Colorimetric Determination of Cholesterol in Dairy Products

1976 ◽  
Vol 59 (5) ◽  
pp. 1146-1149 ◽  
Author(s):  
Kermit C Bachman ◽  
Jan-Hai Lin ◽  
Charles J Wilcox
Keyword(s):  
Dairy Products ◽  
Skim Milk ◽  
Raw Milk ◽  
Colorimetric Determination ◽  
Hexane Extraction ◽  
Color Development ◽  
Fat Extraction ◽  
Chromatographic Procedure ◽  
Liquid Chromatographic

Abstract Cholesterol can be determined colorimetrically in dairy products at levels of ≥10 μg (coefficient of variation = 5.3%) with an o-phthalaldehyde reagent when non-cholesterol lipids arc eliminated prior to color development. Absorbance for 2 mg tripalmitin was found to be equivalent to about 20 μg cholesterol. Saponification followed by hexane extraction removed interfering lipids. Using the described procedure, 238 individual raw milk samples were found to contain 144.4±37.9 μg cholesterol/ml, while their skim milk portions had 26.5±6.4 μg cholesterol/ml (mean ± standard deviation). The o-phthalaldehyde cholesterol estimates agreed with those obtained by a gas-liquid chromatographic procedure when cheese and ice cream were analyzed by the colorimetric procedure with and without prior fat extraction.

Determination of Aflatoxins in Peanut Butter, Using Two Liquid Chromatographic Methods: Collaborative Study

1984 ◽  
Vol 67 (2) ◽  
pp. 312-316
Author(s):  
Alfred D Campbell ◽  
Octave J Francis ◽  
Roberta A Beebe ◽  
Leonard Stoloff ◽  
◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Peanut Butter ◽  
Collaborative Study ◽  
Normal Phase ◽  
Phase Method ◽  
Reverse Phase ◽  
Phase Liquid ◽  
Liquid Chromatographic ◽  
Packed Flow Cell

Abstract Two methods for determining aflatoxins in peanut butter, one using normal phase and the other reverse phase liquid chromatography (LC), were studied by 8 and 10 collaborators, respectively. Fluorescence detection was used for the determinative step in both methods. For reverse phase LC, aflatoxins B1 and G1 were converted to B2a and G2a; for normal phase LC, a silica gel-packed flow cell was placed in the irradiating light path of the detector. The samples included spiked and naturally contaminated peanut butter with total aflatoxin levels from about 5 to 20 ng/g and controls in a balanced pair design. For the normal phase LC method, recoveries of B1, B2, G1, and G2 from spiked samples averaged 79, 92, 74, and 88%, respectively; for the reverse phase method, the recoveries were 103, 104, 89, and 163%. For the normal phase LC method, pooled repeatabilities were 20, 23, 28, and 17% for B1, B2, G1, and G2, respectively; for the reverse phase method, the repeatabilities were 19, 22, 38, and 31%. For the normal phase method, pooled reproducibilities were 34, 33, 39, and 34% for B1, B2, G1, and G2, respectively; for the reverse phase method, the reproducibilities were 32, 46, 51, and 52%. Both methods show an improved limit of detection and better within-laboratory precision over current AOAC methods; however, between-laboratory precision is no better, and the reverse phase method shows evidence of interferences being measured. For these reasons and because of no benefits of present value, neither method was submitted for adoption as official first action.

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