Collaborative Study of a Spiral Vessel Count Method for Estimating Shell in the Chocolate Component of Cocoa and Related Products

1968 ◽  
Vol 51 (3) ◽  
pp. 725-735
Author(s):  
Manion M Jackson
Keyword(s):  
Standard Deviation ◽  
Collaborative Study ◽  
Pectic Acid ◽  
Counting Procedure ◽  
Count Method ◽  
Cocoa Products ◽  
Two Samples ◽  
Borax Solution ◽  
Vessel Count ◽  
Microscopic Counting

Abstract Part-I: The spiral vessel count method for estimating pectic acid in cocoa has been modified to replace the saturated borax solution by 4% NaOH, which gives a clearer product to count, and to include a method for preparing the sample dry fat-free and 250 mesh before analyzing, by hand grinding or grinding by two different grinders. Counts have been made on known shell in the chocolate component mixtures. A formula usable in a 1—15% range and standard curves have been prepared for the estimation of shell in the chocolate component. Counts have been taken at 100X and 200x on a 0.2 g/100 ml concentration, and at 200X on a 0.35 g/50 ml concentration; 200X counting of the higher concentration is preferred for 1—15% shell. Cocoas of known pectic acid content were analyzed by the method and per cent shell found by spiral vessel counts compared with per cent pectic acid. These cocoas were also analyzed before being made 250 mesh for comparative purposes. An intralaboratory study was made on two samples. Part-II: A collaborative study for determining per cent shell by the spiral vessel count method was made on four samples of cocoa products by six collaborators; two samples were defatted and ground to 250 mesh, the other two samples were hand-ground. Five collaborators varied less than 1 standard deviation unit from the average on the four subdivisions; one collaborator was just outside the standard deviation on one sample. The precision of the results was within a reasonable range for a microscopic counting procedure, and the method has been recommended for adoption as official, first action.

Stone Cell Count Method and Stone Cell Group Method for Estimating Shell in Chocolate Products

1970 ◽  
Vol 53 (3) ◽  
pp. 476-489
Author(s):  
Manion M Jackson
Keyword(s):  
Standard Deviation ◽  
Cell Count ◽  
Press Cake ◽  
Cell Group ◽  
Group Method ◽  
Pectic Acid ◽  
Cell Content ◽  
Stone Cell ◽  
Count Method ◽  
Vessel Count

Abstract Per cent shell in the chocolate component of cocoa and similar products is determined on the basis of an average stone cell content of 9340 stone cells/mg dry fat-free 250 mesh shell. The sample is weighed and diluted to a weighed suspension in 60% (v/v) glycerine. The total number of stone cells in a weighed drop on a slide are counted microscopically at 100–200X. The per cent shell chocolate component is then calculated. Seven cocoa samples were analyzed and their results were compared to previous results obtained by the spiral vessel count and pectic acid methods. Average results for shell in the chocolate component were 6.5% for the stone cell count method, 6.6% for the spiral vessel count method, and 6.4% for the pectic acid method. Six collaborators studied 4 cocoa samples and compared 3 methods: the stone cell count method, the calculation procedure of Van Brederode and Reeskamp, and the stone cell group method. Five varied less than 1 standard deviation from the average for 3 samples and 4 collaborators were within 1 standard deviation in the stone cell count method for the remaining sample. The stone cell count method is recommended for adoption as official first action for the analysis of shell for cocoa, cocoa press cake, chocolate liquor, and expeller cake; the group method is recommended for other chocolate products.

Collaborative Study of the Coulter Counter-Chemical Method for Counting Somatic Cells in Raw Milk1

1977 ◽  
Vol 40 (7) ◽  
pp. 456-458 ◽  
Author(s):  
R. E. GINN ◽  
D. R. THOMPSON ◽  
V. S. PACKARD
Keyword(s):  
Standard Deviation ◽  
Somatic Cell ◽  
Somatic Cell Count ◽  
Chemical Method ◽  
Collaborative Study ◽  
Somatic Cells ◽  
Cell Counting ◽  
Milk Samples ◽  
Counting Procedure ◽  
Electronic Counting

Variation between laboratories for Electronic Somatic Cell Counting by the chemical method (ESCC) was evaluated by a collaborative study. Eight laboratories counted somatic cells in 12 milk samples (six replicated samples) by the ESCC method. The somatic cell count for the same milk samples was also evaluated by the Direct Microscopic Somatic Cell Counting procedure (DMSCC) as a comparison for the level of error. The standard deviation of the variation of logarithms of ESCC counts between laboratories was 0.04368. The standard deviation for the variation of logarithms of DMSCC counts between technicians was 0.08617. The corresponding value for the DMSCC analysis of the last set of federal split milk samples was 0.141. An earlier study of electronic counting by the centrifuge method showed a standard deviation of 0.0711.

Improved Automated Optical Somatic Cell Counting Method for Raw Milk: Collaborative Study

1978 ◽  
Vol 61 (6) ◽  
pp. 1328-1334
Author(s):  
Wesley N Kelley
Keyword(s):  
Standard Deviation ◽  
Somatic Cell ◽  
Collaborative Study ◽  
Sampling Rate ◽  
Raw Milk ◽  
Cell Counting ◽  
Counting Method ◽  
Milk Samples ◽  
Counting Procedure ◽  
Statistical Results

Abstract A collaborative study was conducted to compare the improved automated optical somatic cell counting procedure (OSCC II) with the direct microscopic somatic cell counting method (DMSCC) in raw milk. Samples were prefixed with formaldehyde and introduced into an Auto- Analyzer system. Dilution, clarification, and cell counting were performed automatically. Five collaborators participated in the study; they analyzed 48 samples in duplicate, using 2 different sampling rates. The results were compared with DMSCC counts reported by 3 different analysts. Statistical results show that the standard deviation for the DMSCC method is 0.0825 and for the OSCC II, at a sampling rate of 80/hr, 0.0434. When results are compared, the OSCC II procedure is as accurate as, and is significantly more precise than, the DMSCC method. The faster sampling rate of the OSCC II at 120/hr has some effect on precision but little effect on accuracy. The method has been adopted as official first action.

A COMPARATIVE STUDY OF STAINS PROPOSED FOR THE DIRECT MICROSCOPIC EXAMINATION OF MILK

1951 ◽  
Vol 14 (2) ◽  
pp. 49-64 ◽  
Author(s):  
Joseph C. Olson ◽  
Luther A. Black
Keyword(s):  
Methylene Blue ◽  
Potassium Dichromate ◽  
Collaborative Study ◽  
Laboratory Procedure ◽  
Standard Methods ◽  
Weighted Averages ◽  
Counting Procedure ◽  
Direct Microscopic Examination ◽  
Blue Stain ◽  
Microscopic Counting

Five stains which have been proposed as substitutes for stains now specified in Standard Methods were compared by means of a collaborative study involving nine different laboratories. Stain I was the present Standard Methods alcohol-containing methylene blue stain; Stain II was a potassium - dichromate - sulfuric acid polychrome methylene blue stain; Stain III was an acid- and water-free methylene blue stain; Stain IV was a modification of Stain III containing hydrogen peroxide; Stain V was a methylene blue stain, the use of which was accompanied by a modification in fixation of the milk film; and Stain VI was a modified two color stain, details of which were not supplied. Examination of weighted averages of all samples from all laboratories showed that Stain III yielded the highest average count. Unfavorable comments pertaining to all stains except Stain III were received. Great variation in the results between laboratories was evident. One stain might show superior results in one laboratory and give inferior results in another laboratory. In general, Stain III showed the least variation in results among the collaborating laboratories, although it obtained the highest score in only one laboratory. The study pointed up the need for uniformity in laboratory procedure among different laboratories, particularly as regards the direct microscopic counting procedure.

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.

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.

Convection Oven Determination of Loss of Mass on Drying of Quick Frozen French Fried Potatoes: Collaborative Study

1984 ◽  
Vol 67 (3) ◽  
pp. 635-636 ◽  
Author(s):  
David O Biltcliffe ◽  
Hillary J Judd ◽  
Roger Wood ◽  
◽  
A C Bushnell ◽  
...  
Keyword(s):  
Collaborative Study ◽  
Frozen Foods ◽  
Codex Alimentarius Commission ◽  
Convection Oven ◽  
Economic Commission ◽  
Two Samples ◽  
Repeatability And Reproducibility ◽  
Loss Of Mass ◽  
Fried Potatoes

Abstract A collaborative study was carried out on one of the methods submitted to the Joint Economic Commission for Europe (ECE)/Codex Alimentarius Commission Group of Experts on the Standardization of Quick Frozen Foods for the determination of moisture in quick frozen french (fried potatoes. The method was based on the determination of loss of mass of the sample on drying in a convection oven 16 h at 103±2°C. Two samples of uncooked quick frozen french fried potatoes and 2 samples of oven quick frozen french fried potatoes were analyzed by 14 and 13 laboratories, respectively. The method is simple and was found to be analytically satisfactory with repeatability and reproducibility values of 0.21 and 2.00 g/100 g french fried potatoes, and 0.29 and 3.00 g/100 g oven french fried potatoes, respectively. The method was adopted by the Group of Experts in preference to other proposed procedures for this determination. The method has been adopted official first action by AOAC.

scholarly journals Assurance Polyclonal Enzyme Immunoassay for Detection of Listeria monocytogenes and Related Listeria Species in Selected Foods: Collaborative Study

1997 ◽  
Vol 80 (4) ◽  
pp. 775-790 ◽  
Author(s):  
Philip T Feldsine ◽  
Andrew H Lienau ◽  
Robin L Forgey ◽  
Roger D Calhoon ◽  
S Al-Hasani ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Enzyme Immunoassay ◽  
Collaborative Study ◽  
Culture Method ◽  
The United States ◽  
Food Type ◽  
Green Beans ◽  
Private Industry ◽  
Listeria Species ◽  
Two Samples

Abstract Six foods representing a variety of food products were analyzed by the Assurance Listeria polyclonal enzyme immunoassay (EIA) and by either the Bacteriological Analytical Manual or the U.S. Department of Agriculture culture method for detecting Listeria monocytogenes and related Listeria species. Samples of each food type, at each inoculation level, were analyzed simultaneously by both methods. A total of 19 laboratories representing federal government agencies and private industry in the United States and Canada participated. Food types were inoculated with Listeria species including L. monocytogenes, with the exception of 3 lots of green beans, which were naturally contaminated. During this study, 1764 samples and controls were analyzed and confirmed, of which 492 were positive and 947 were negative by both methods. There were 159 samples that were positive by culture method but negative by the EIA and 188 that were negative by culture method but positive by EIA. Twenty-two samples were negative by EIA and by culture method but confirmed positive when Assurance selective enrichment broths were subcultured to selective agar. The Assurance polyclonal EIA for detecting L. monocytogenes and related Listeria species in foods has been adopted first action by AOAC INTERNATIONAL.

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.

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