Determination of total dietary fiber in foods and food products by using a single-enzyme, enzymatic-gravimetric method: interlaboratory study

A simplified enzymatic-gravimetric method for total dietary fiber (TDF) determination has been published and used in the Food Composition Laboratory of the U.S. Department of Agriculture since 1988. THis method gives comparable results to AOAC Official Methods 985.29 and 991.43 but the AOAC methods use 100 degrees C (water bath) to gelatinize the sample and a combination of alpha-amylase and an amyloglucosidase to hydrolyze starches, whereas the simplified method incorporates an autoclaving step (121 degrees C) for gelatinization followed by incubation with only amyloglucosidase. The simplified method omits protease hydrolysis and does not require any pH adjustment. Overall, the simplified method cuts cost and is less labor intensive. An interlaboratory study was conducted to validate this method. Blind duplicates of six sample (baked beans, corn bran, roasted peanuts, cooked potatoes, white bread with reduced calories, and cooked white rice) were sent to 11 laboratories. The reproducibility relative standard deviations of the TDF values (without outliers) ranged from 3.46 to 27.6%. The repeatability standard deviations ranged from 0.91 to 14.6%.     

Physiochemical methods for pharmacokinetic and residue analysis of chloramphenicol and degradation products in dairy cows

The disposition of chloramphenicol after intramammary and intravenous administration was followed through determinations of chloramphenicol in blood and milk by means of high-performance differential pulse polarography. The concentration-time curves obtained reflected the different modes of administration, and allowed calculation of some pharmacokinetic parameters. The results of the polarographic determination in blood agreed fairly well with those of the microbiological assay in serum. Several body fluids and tissues of the cows were examined for residues of chloramphenicol and degradation products, both by the microbiological method and by high-performance liquid chromatography with ultraviolet detection. In urine, chloramphenicol and chloramphenicol glucuronide were found; in the other fluids and tissues only now and then a trace of chloramphenicol or a degradation product was detected. From these results it appears that chloramphenicol and degradation products are eliminated rapidly and completely after intravenous or intramammary application. No accumulation of degradation products occurred.     

Assessment of the quality of dairy products by capillary electrophoresis of milk proteins

This paper presents an overview of existing capillary electrophoretic methods for the study of milk proteins. The main methods of analysis of caseins, whey proteins and peptides are examined with particular attention to their application to the evaluation of the quality of dairy products. Aspects such as the study of protein polymorphism, evaluation of heat treatments, detection of adulteration and assessment of proteolysis are considered in detail.     

Indirect and direct determination of the casein content of milk by Kjeldahl nitrogen analysis: collaborative study

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 x 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.     

Clinical analysis of human urinary proteins using high resolution electrophoretic methods

The application of isoelectric focusing (IEF), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional electrophoresis (2-DE) and capillary electrophoresis (CE) for high resolution electrophoretic analysis of human urinary proteins is reviewed. In each case, the information is tabulated chronologically with details of sample preparation, electrophoretic system, detection method and clinical application. The text includes an historical perspective of the use of each method for urinalysis and a detailed review of the application of the methods to the investigation of renal disease, renal transplantation, Bence Jones proteinuria (BJP), diabetes mellitus, cadmium toxicity, nephrolithiasis and cancers of the urogenital tract.     

Detection of Salmonella in dry foods using refrigerated pre-enrichment and enrichment broth cultures: interlaboratory study

An interlaboratory study was performed in 11 laboratories to validate the use of pre-enrichment and tetrathionate brilliant green (TBG35) and selenite cystine (SC35) enrichment cultures refrigerated 72 h at 2-5 degrees C for greater analytical flexibility in the detection of Salmonella in dry foods. Productivities of refrigerated pre-enrichment and enrichment cultures were compared with that of the AOAC/Bacteriological Analytical Manual (BAM) procedure using 4 food types: whole egg powder, milk chocolate, animal feed, and instantized skim milk powder. Uninoculated and inoculated samples were included in each food group. There was complete agreement between the results obtained by the standard AOAC/BAM procedure and the 2 refrigeration procedures. Of 660 samples tested, the AOAC/BAM procedure identified 393 contaminated samples that were readily detected from the corresponding refrigerated pre-enrichment cultures and from the combined productivity of homologous refrigerated TBG35 and SC35 cultures. Refrigeration (72 h) of pre-enrichment or enrichment cultures for greater analytical flexibility and laboratory productivity in the examination of dry foods is under review for adoption by AOAC International.     

Molecular identification and cluster analysis of homofermentative thermophilic lactobacilli isolated from dairy products

Twenty-five strains of thermophilic lactobacilli isolated from yoghurt and from semi-hard and hard cheeses (in parallel with nine type or reference strains) were identified and grouped according to their genetic relatedness. Strains were identified by sugar fermentation patterns using the "API 50 CHL" galleries, by species-specific DNA probes in dot-blot hybridization experiments, by amplification and restriction analysis of the 16S rRNA gene (ARDRA) and by polymerase chain reaction (PCR) using species-specific oligonucleotide primers. Strains were classified as Lactobacillus delbrueckii subsp. lactis and subsp. bulgaricus, L. helveticus, and L. acidophilus. Strains which were atypical by sugar fermentation patterns were also identified. Most of the strains could not be grouped using carbohydrate fermentation profiles. PCR fingerprinting was used to identify DNA profiles for the 25 lactobacilli. Experimentally obtained PCR profiles enabled discrimination of all strains, which were grouped according to the similarities in their combined patterns. In general, the clustering of the strains corresponded well with species delineation obtained by molecular identification. The dendrogram of genetic relatedness enabled the unambiguous identification of most of the strains which were shown to be atypical by the sugar fermentation profile, except for a discrepancy in one L. delbrueckii subsp. lactis strain and one atypical Lactobacillus sp. strain.     

Predicting body cell mass with bioimpedance by using theoretical methods: a technological review

The body cell mass (BCM), defined as intracellular water (ICW), was estimated in 73 healthy men and women by total body potassium (TBK) and by bioimpedance spectroscopy (BIS). In 14 other subjects, extracellular water (ECW) and total body water (TBW) were measured by bromide dilution and deuterium oxide dilution, respectively. For all subjects, impedance spectral data were fit to the Cole model, and ECW and ICW volumes were predicted by using model electrical resistance terms RE and Rt in an equation derived from Hanai mixture theory, respectively. The BIS ECW prediction bromide dilution was r = 0.91, standard error of the estimate (SEE) 0.90 liter. The BIS TBW prediction of deuterium space was r = 0.95, SEE 1.33 liters. The BIS ICW prediction of the dilution-determined ICW was r = 0.87, SEE 1.69 liters. The BIS ICW prediction of the TBK-determined ICW for the 73 subjects was r = 0.85, SEE = 2.22 liters. These results add further support to the validity of the Hanai theory, the equation used, and the conclusion that ECW and ICW volume can be predicted by an approach based solely on fundamental principles.     

Bacterial tracking in a dairy production system using phenotypic and ribotyping methods

A systematic sampling plan was designed to collect raw and pasteurized milk samples throughout a single-raw milk source, dairy-processing operation experiencing reduced product shelf lives due to bacterial contamination. The objectives were to track bacterial contamination sources throughout a complete dairy production system and use this information to reduce bacterial spoilage losses in processed fluid products. Over a 5-week period, 233 bacterial isolates were collected, representative of different colony morphologies on psychrotrophic bacteria count (PBC) plates. Forty-five isolates (19%) were obtained from pasteurized milk and 188 (81%) were isolated from raw product. Thirty isolates were identified as Pseudomonas spp. by Gram stain and biochemical methods. Of these, 27 (90%) were postpasteurization isolates and 3 (10%) were raw milk isolates. Automated ribotyping revealed that raw and pasteurized Pseudomonas fluorescens isolates were indistinguishable (similarity index > 0.93), suggesting the possibility of postpasteurization contamination with bacteria from raw product. In the plant, filler nozzles were identified as the primary reservoirs of postpasteurization contamination. Nozzle replacement produced significantly lower finished-product PBCs at 7 days postprocessing (> 4-log reduction) and extended fluid product shelf life.     

Identification and clustering of dairy propionibacteria by RAPD-PCR and CGE-REA methods

A total of 67 classical propionic acid bacteria (PAB) strains, 10 of which were from type culture collections and 57 from milk, typical Italian cheeses, acid whey and feed flour of different regions, were analysed by Randomly Amplified Polymorphic DNA (RAPD-PCR) and by Conventional Gel Electrophoresis Restriction Endonuclease Analysis (CGE-REA). The genotypic traits achieved using RAPD-PCR with three primers (OPL-01, OPL-02 and OPL-05) and SmaI CGE-REA patterns were compared by numerical analysis and allowed a clear distinction of four clusters corresponding to the currently described species of classical propionibacteria according to type and reference strains positions. No discrepancies exist in species recognition between the two methods; 36 isolates were identified as Propionibacterium freudenreichii, 15 as P. jensenii, four as P. acidipropionici and two as P. thoenii. Many differences, however, were observed in intraspecific clustering. Numerical comparison of RAPD-PCR profiles appeared to be a suitable method for highlighting the presence of particular phenotypic characters, while intraspecific differentiation obtained by CGE-REA analysis allowed association of strains at high similarity levels on the basis of their geographical origin.     

Gas chromatographic determination of chloramphenicol residues in shrimp: interlaboratory study

An interlaboratory study of a gas chromatographic method for determining chloramphenicol (CAP) residues in shrimp was conducted. An internal standard (Istd), the meta isomer of CAP, was added to the shrimp, and the treated shrimp were homogenized with ethyl acetate. The ethyl acetate extract was defatted with hexane, and the CAP was partitioned into ethyl acetate from an aqueous salt solution. The ethyl acetate was evaporated, and the dried residue was treated with Sylon, a trimethylsilyl derivatizing agent, to yield the trimethylsilyl derivative of CAP. A portion of the solution containing the derivative was injected into a gas chromatograph equipped with an electron capture detector. Levels of fortified and incurred CAP were calculated from the peak area ratio of standard CAP to Istd. Recoveries of CAP from tissue directly fortified at 5 ppb were 102% (within-laboratory relative standard deviation [RSDr] = 5.6%), 104% (RSDr = 5.5%), and 108% (RSDr = 6.3%) from Laboratories 1, 2, and 3, respectively. Incurred-CAP residues at 5 and 10 ppb levels were also determined, with the following results: Laboratory 1: composite A, 4.56 ppb (RSDr = 14.0%); composite B, 8.38 ppb (RSDr = 11.6%); Laboratory 2: composite A, 4.17 ppb (RSDr = 12.5%); composite B, 8.90 ppb (RSDr = 5.60%); Laboratory 3: composite A, 4.66 ppb (RSDr = 14.9%); composite B, 11.0 ppb (RSDr = 11.8%).     

Risks and prevention of contamination of dairy products

Consumers and regulatory officials are becoming increasingly aware of the human health risk of the presence of micro-organisms or chemicals in the agricultural environment. Providing 'on-farm food safety' programmes which address the daily management of the production unit with regard to animal health and well-being, public health and environmental health must be a top priority for agriculturalists and veterinarians. Developing critical control point management (CCPM) procedures for animal and human health concerns is a viable approach to aid in alleviating public concerns about dairy products and the food supply in general. Such CCPM programmes may be created for individual production units based upon risk analysis, total quality management and hazard analysis and critical control point principles. Implementation of these programmes will be essential both in addressing food safety concerns for the resident population of a nation and in developing or maintaining international markets for the export of animal products.     

1995: a decisive progress for the interlaboratory transferability of results by using enzyme and protein reference materials

Transferability of results in clinical enzymology and immunochemistry may be improved by using validated calibrators. For that purpose, certified reference materials (CRM) have been developed. Authors emphasize the need to make known and to use these tools properly, and on the potential efficiency of this approach in immunochemistry with CRM 470, certified for 14 plasma proteins and with enzyme CRMs produced at the international level. They recall the necessity to validate calibrators for specified techniques of measurement used in routine. They also indicate that this approach, if properly conducted, should allow to ensure the transferability of results in enzymology and immunochemistry and thus the clinical efficiency of laboratory results.     

Histometric study of meat products. A literature review

In the present paper, the literature on the development of methods for histometric monitoring the quality of meats is reviewed. The value of specific techniques, statistical interpretation of results and the practicability of automation of histometric analysis are examined more closely. It is concluded from the study of the literature that histometric examination of meats allows an objective assessment of volume percentages of tissue components. When a distinct difference in contrast between various tissues is achieved by specific staining methods, developments in the field of image analysis systems will allow automation of the quantitative histological examination of meats.     

Routine cultures of bone marrow and peripheral stem cell harvests: clinical impact, cost analysis, and review

The American Association of Blood Banks requires routine culture of hematopoietic progenitor cells prior to bone marrow transplantation. We sought to evaluate the cost of that requirement and the incidence and clinical significance of positive cultures. We performed a retrospective analysis of transplant recipients at our institution. Of the 605 patients for whom 1,934 consecutive cultures of harvests were done between December 1992 and February 1996, 11 had positive cultures. Six patients received a culture-positive harvest with no adverse effects. The total cost of cultures was $35,660 (U.S. $). In North America and worldwide in 1995, routine culture of harvests would have prevented 7.9 and 18.9 cases of bacteremia, respectively, at a cost of $95,000 per bacteremia prevented. We conclude that routine culture of hematopoietic progenitor cells yields low rates of positivity and that infusion of contaminated harvests rarely results in clinically adverse outcomes.     

刀具锋利度测试方法的研究

锋利度是刀具最重要的技术指标之一.但是长期以来,国内对锋利度测定方法没有统一明确的规定,严重制约了该行业的技术研究及产品质量提高.作者对锋利度的物理原理进行论述、比较了国内现有的锋利度测试法,对英国最新的锋利度测试法进行探讨及改良,提出了可行的刀具锋利度测试方法.     

Determination of leucogentian violet in chicken fat by liquid chromatography with electrochemical and ultraviolet detection: interlaboratory study

A laboratory trial was completed for a liquid chromatographic method that can quantitate leucogentian violet (LGV) in chicken fat at 10 ppb. With this method, LGV is isolated from the fat matrix by a series of liquid-liquid extractions. This trial evaluated 2 detection systems: electrochemical (EC) and ultraviolet (UV). The participating laboratories determined incurred residues at 2 levels as well as fat samples fortified at 5, 10, and 20 ppb. Using UV detection, the 3 laboratories reported the following range of recoveries: 71.0-89.6% at 5 ppb, 74.7-83.9% at 10 ppb, and 77.2-79.0% at 20 ppb. When these same samples were chromatographed with EC detection, the 2 reporting laboratories obtained the following average recoveries: 79.0 and 92.5% at 5 ppb, 75.9 and 85.4% at 10 ppb, and 77.3 and 79.8% at 20 ppb. The average concentrations found for the first level of incurred sample were 6.3, 6.3, and 5.4 ppb with coefficients of variation (CVs) of 2.4, 7.6, and 33.7%, respectively, when UV detection was used. Samples chromatographed with EC detection averaged 6.3 and 6.4 ppb with CVs of 4.0 and 8.2%, respectively. The second level of incurred sample gave average concentrations of 27.6, 29.0, and 10.9 ppb with CVs of 11.0, 5.0, and 42.8%, respectively, when the UV detection system was used. With the EC detector, the concentrations averaged 27.2 and 30.7 ppb with CVs of 15.7 and 3.5%, respectively.     

Development of a technology for pressing high-density products using gas-draining methods

The factors that hinder the formation of high-density compacts by cold-pressing of powders are considered. The main factors are the gases present in the charge and the technological lubricant introduced to facilitate the work of the press mold. A procedure has been developed for calculating the efficiency of gas drainage from a mold and the pressure in gas pores in the compacts. Recommendations are made for increasing the density of compacts from iron powders by a single cold pressing.Scientific-Industrial FirmBakkonditsioner,Baku. Translated from Poroshkovaya Metallurgiya, No. 5–6, pp. 34–39, May–June, 1994.     

Selection for economic efficiency of dairy cattle using information on live weight and feed intake: a review

The objective of this study was to review some of the latest evidence of genetic variation in feed intake and feed utilization and to determine how this variation might be used. The most important sources of genetic variation in gross efficiency are likely to be the quantities of feed eaten and used for yield or maintenance and the extent to which body tissue is mobilized. Accounting for just one of these components when selection is for improved feed efficiency might result in undesirable genetic changes. For example, in an ad libitum feeding system, the heritability of body condition score is reported to be 0.43 for heifers; genetic correlations of body condition score with milk production and live weight were -0.46 and 0.66, respectively. Also, the genetic correlation between milk yield and live weight depends on lactation stage. For example, over the first 26 wk of lactation, this correlation was reported to be -0.09, but, after genetic adjustment for body condition score, the correlation was 0.29. When economic values are being derived, energy norms or genetic correlations can be used, and double counting of the feed costs needs to be avoided. An index that contained linear type traits, however, gave high accuracy of selection. Hence, although there appears to be great potential to improve economic efficiency by selecting for feed intake and live weight or by possible indicator traits, there is still uncertainty about some of the genetic parameters, especially among traits related to health, reproduction, and energy balance.