scholarly journals Proteolysis in raw milk in relation to microbiological indicators

2016 ◽  
Vol 34 (No. 4) ◽  
pp. 306-312 ◽  
Author(s):  
J. Chramostová ◽  
O. Hanuš ◽  
M. Klimešová ◽  
I. Němečková ◽  
P. Roubal ◽  
...  
Keyword(s):  
Early Detection ◽  
Somatic Cell Count ◽  
Correlation Coefficients ◽  
Raw Milk ◽  
Total Count ◽  
Psychrotrophic Bacteria ◽  
Milk Samples ◽  
Crucial Parameter ◽  
Microbiological Indicators

Proteolysis in raw milk is a crucial parameter indicating both cow’s mastitis and the technological problems or spoilage risk of final products. However, a suitable analytical method for its early detection in practice is still missing. Thus, we proposed a spectrophotometric determination of milk proteolysis equivalent (MPE). We tested this method on 104 bovine raw milk samples in relation to their somatic cell count (SCC) as an indicator of native proteolysis, and the total count of mesophilic bacteria (TCMB) and the total count of psychrotrophic bacteria (TCPB) as indicators of microbial proteolysis. Correlation coefficients between log TCMB and MPE and log TCPB and MPE were 0.3651 and 0.4152, respectively (both P < 0.001). SCC was not correlated with MPE (P > 0.05). We estimated the MPE limit indicating an incipient risk of proteolysis in the range from 0.9366 to 1.02 mmol/l. The determination of MPE seems to be a promising method applicable in the control of raw milk.

scholarly journals Evaluation of the caseinomacropeptide (CMP) content in raw and uht milk during storage time.

2013 ◽  
Vol 2 (2) ◽  
Author(s):  
Elaine Closs ◽  
Claucia Fernanda Volken de Souza
Keyword(s):  
Storage Time ◽  
Chromatographic Method ◽  
Correlation Coefficients ◽  
Storage Period ◽  
Raw Milk ◽  
Bacteria Growth ◽  
Uht Milk ◽  
Psychrotrophic Bacteria ◽  
Spectrophotometric Methods

<p>Coolers are used in raw milk storage in order to inhibit the growth of lactic acid producer mesophilic microorganisms. However, refrigerated milk is a favorable environment to psychrotrophic aerobic bacteria growth. These psychrotrophic bacteria promote proteolysis which is of concern to the dairy industry since it may indicate a false positive of fraudulent addition of whey to raw milk. This study evaluated the influence of storage time on the presence of caseinmacropeptide (CMP) in raw milk during storage as well as in ultra-high temperature milk (UHT) throughout its shelf life. Three different determination methods were compared each other, namely the standard chromatographic method and two spectroscopy methods for the quantitative determination of sialic acid. One is based on the determination of ninhydrin acid and the other one is an adapted method using the Ehrlich reagent. An increase of CMP content throughout the storage period for the cooled raw milk and UHT milk was detected despite the fact that none had cheese whey. The spectrophotometric methods showed correlation coefficients greater than 0.97 with the chromatographic method established by Brazilian legislation. The results indicate that the spectrophotometric method using the ninhydrin acid can be used as an alternative method for the determination of CMP in milk samples.</p><p>&nbsp;</p><p>DOI: http://dx.doi.org/10.14685/rebrapa.v2i2.54</p>

Detection of proteolysis in raw milk stored at low temperature by an inhibition ELISA

1994 ◽  
Vol 61 (3) ◽  
pp. 395-404 ◽  
Author(s):  
Catherine Picard ◽  
Isabelle Plard ◽  
Dominique Rongdaux-Gaida ◽  
Jean-Claude Collin
Keyword(s):  
Proteolytic Activity ◽  
Limit Of Detection ◽  
Bacterial Count ◽  
Raw Milk ◽  
Enzyme Linked Immunosorbent Assay ◽  
Psychrotrophic Bacteria ◽  
Milk Samples ◽  
Inhibition Elisa ◽  
Different Strains

SummaryAn inhibition ELISA (enzyme-linked immunosorbent assay) was developed for the determination of caseinomacropeptide (CMP) in order to estimate the proteolysis of κ-casein due to the enzymes of psychrotrophic bacteria in bulk raw milk. The CMP present in milk was quantified specifically by an antibody. The limit of detection was ∽ 0·1 μg/ml and the CV was < 10%. This method was used to study the proteolytic activity of three strains of psychrotrophic Pseudomonas fluorescens in raw milk and to analyse different raw milk samples supplied by four dairy plants. The proteolytic activity for different strains of psychrotrophs and for different milk samples varied considerably, but no correlation was established between the level of microbial flora and κ-casein proteolysis. It is thus not possible to determine the extent of proteolysis from the bacterial count alone. However, by CMP determination in bulk raw milk samples after 6 d storage at 4°C, the mean κ-casein proteolysis was ∽ 4%. Among the milk samples analysed that contained < 107 cfu psychrotrophs/ml, 30% exhibited a proteolysis of κ-casein < 0·5%, i.e. < 5μg CMP/ml.

scholarly journals Bulk tank somatic cell count and associated microbial quality of milk from selected dairy cattle herds in Oyo State, Nigeria

2018 ◽  
Vol 7 (2) ◽  
Author(s):  
Olufemi Olatoye ◽  
Adesola Amosun ◽  
Uzo Ogbu ◽  
Yemi Okunlade
Keyword(s):  
Somatic Cell ◽  
Cell Count ◽  
Somatic Cell Count ◽  
Health Management ◽  
Development Program ◽  
Raw Milk ◽  
Human Consumption ◽  
Quality And Safety ◽  
Milk Samples ◽  
California Mastitis Test

Improvement of traditional and nomadic milk production through dairy development program in Nigeria requires routine quality and safety monitoring of milk both at herd level and milk collection centers. A total of 411 bulk raw milk samples aseptically obtained from Ibarapa, Oyo and Oke-Ogun industrial milk collection centers were subjected to California Mastitis Test (CMT), Bulk Somatic Cell Count (BSCC) and bacteriological analysis for assessment of quality and safety of milk from the herds. One hundred and seven (26.0%) of the samples were CMT positive, while 74.0% were negative to CMT. The overall mean BSCC, TAC and TCC were 1.27×103 ± cells/mL, 1.12×103± 34 cfu/mL, 97.8±9.8 cfu/mL in the CMT negative milk samples while for the strong positive samples the mean BSCC, TAC and TCC were 4.33×106 ± cells/mL, 2.35×106 ± 453 cfu/mL, 189.3±41.1 cfu/mL respectively; these were higher than the Pasteurized Milk Ordinance acceptable limits. Positive correlation was found between CMT scores and bacterial contamination and between CMT scores and SCC was recorded. About 26.0% of the samples with positive CMT could be considered unsafe due to strong correlation with microbial contamination that could result in milk borne zoonoses and public health hazards. However, a greater proportion (76.9%) of the milk with negative CMT scores could be safe for human consumption after post-harvest pasteurization. Consequently, there is need to improve handling, environmental and milking hygiene; as well as proper herd and udder health management to improve quality and safety of Nigeria dairy products.

scholarly journals Simultaneous Determination of C18 Fatty Acids in Milk by GC-MS

Separations ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 118
Author(s):  
Meiqing Chen ◽  
Yangdong Zhang ◽  
Fengen Wang ◽  
Nan Zheng ◽  
Jiaqi Wang
Keyword(s):  
Fatty Acids ◽  
High Sensitivity ◽  
Raw Milk ◽  
Uht Milk ◽  
Milk Samples ◽  
Accuracy And Precision ◽  
Different Temperatures ◽  
Chromatographic Resolution ◽  
Commercial Milk

The determination of C18 fatty acids (FAs) is a key and difficult aspect in FA profiling, and a qualified method with good chromatographic separation and high sensitivity, as well as easy methylation, is required. A GC-MS method was established to simultaneously determine C18 FAs in milk. To simplify the methylation protocol for milk samples, besides a base-catalyzation methylation (50 °C for 20 min), the necessity of an additional acid-catalyzation was also studied using different temperatures (60 °C, 70 °C, 80 °C, and 90 °C) and durations (90 min and 150 min). The results showed that the chromatographic resolution was improved, although three co-eluted peaks existed. The base-catalyzation was sufficient, and an additional acid-catalyzation was not necessary. The proposed method was validated with good sensitivity, linearity, accuracy, and precision, and then applied in determining C18 FAs in 20 raw milk and 30 commercial milk samples. UHT milk presented a different profile of C18 FAs from raw milk and PAS milk samples, which indicated that excessive heating could change the profile. Overall, the proposed method is a high-throughput and competent approach for the determination of C18 FAs in milk, and which presents an improvement in chromatographic resolution and sensitivity, as well as a simplification of methylation.

Preservation and Storage Mechanisms for Raw Milk Samples for Use in Milk-Recording Schemes

1996 ◽  
Vol 59 (2) ◽  
pp. 151-154 ◽  
Author(s):  
HUMBERTO G. MONARDES ◽  
ROBERT K. MOORE ◽  
BRIAN CORRIGAN ◽  
YVON RIOUX
Keyword(s):  
Cell Count ◽  
Somatic Cell Count ◽  
Potassium Dichromate ◽  
Dairy Herd ◽  
Raw Milk ◽  
Storage Conditions ◽  
Sample Storage ◽  
Milk Samples ◽  
Whole Process ◽  
And Storage

This study, carried out by the Quebec Dairy Herd Analysis Service, compares (during summer conditions in Quebec) the performance of three types of preservatives for raw milk under four different systems of sample storage: no refrigeration, refrigeration at the laboratory only, refrigeration during transport and at the lab, and complete refrigeration from sampling at the farm to analysis. The objective was to determine the best preservative and storage conditions for protecting milk components during transportation and storage of raw milk samples collected at the farm and sent to a central testing lab for analysis. Milk samples were analyzed at day 3 and at day 7 after sampling to observe the effect of aging. A total of 12,480 samples were collected during the trial. The components studied were percentage of fat and protein and somatic cell count (SCC). In general, samples preserved with bronopol (2-bromo-2-nitropropane-1,3-diol and 2-bromo-2-nitropropanol) in liquid or in microtab tended to give higher readings for fat and protein contents than samples preserved with potassium dichromate. Significantly lower fat values were observed in 7-day-old samples compared to 3-day-old samples. Fat depression was more accentuated in nonrefrigerated samples. Under current methods of handling raw milk samples, refrigeration during the whole process of sampling, transportation, and until analysis, seems an ideal to attain to avoid significant reductions of fat values.

Determination of Viable Bacterial Populations in Raw Milk within 20 Minutes by Using a Direct Epifluorescent Filter Technique

1997 ◽  
Vol 60 (7) ◽  
pp. 874-876 ◽  
Author(s):  
CLAUDE P. CHAMPAGNE ◽  
NANCY J. GARDNER ◽  
JULIE FONTAINE ◽  
JACQUES RICHARD
Keyword(s):  
Raw Milk ◽  
Plate Count ◽  
Bacterial Populations ◽  
Filter Technique ◽  
Milk Samples ◽  
Standard Plate ◽  
Plate Counts ◽  
Direct Epifluorescent Filter Technique ◽  
Triton X

The results from a shortened procedure for the direct epifluorescent filter technique (DEFT) determination of viable bacterial populations in raw milk were compared to standard plate counts. Shortening the prefiltration trypsin-Triton X-100 incubation period from 10 to 3 min enabled the completion of the analysis within 20 min. The short DEFT method results had a correlation coefficient (r) of 0.81 with plate counts. With respect to precision, the average difference between values of duplicate plate count analyses was 0.16 log units; that of the short DEFT was 0.14 log units. The slopes of the regressions equations were less than 1, indicating that a direct correlation is not achieved. Short DEFT values were 0.17 log units higher than those of plate counts on milk samples containing less than 10,000 CFU/ml. For milk samples containing counts over 10,000 CFU/ml, short DEFT values averaged only 0.05 log units above plate count readings. Daily preparation of the stain appears unnecessary since acridine orange solutions stored for up to 2 days at 4°C did not produce results significantly (P &gt; 0.05) different from those obtained with fresh solutions. The short DEFT method has potential for the assessment of the bacteriological quality of raw milk in tanker deliveries.

BACTERIAL COUNTS OF RAW MILK AND FLAVOR OF THE MILK AFTER PASTEURIZATION AND STORAGE

1972 ◽  
Vol 35 (4) ◽  
pp. 203-206 ◽  
Author(s):  
G. B. Patel ◽  
G. Blankenagel
Keyword(s):  
Raw Milk ◽  
Bacterial Counts ◽  
Psychrotrophic Bacteria ◽  
Milk Samples ◽  
Standard Plate ◽  
Plate Counts ◽  
Subsequent Storage ◽  
And Storage ◽  
Common Defect

A total of 216 raw milk samples with a variety of Standard Plate Counts and psychrotrophic bacteria counts were laboratory-pasteurized, stored at 7 C, and then evaluated for flavor after 1 and 2 weeks. Results showed that milk with counts of &gt;1,000,000/ml before heating frequently developed objectionable flavors after pasteurization and subsequent storage. The most common defect was a bitter flavor which appeared within 2 weeks after pasteurization in nearly all samples which as raw milk had counts exceeding 10,000,000/ml. This off-flavor developed in spite of small numbers of organisms in the pasteurized product and in the absence of post-pasteurization contamination.

Rapid Detection of Psychrotrophic Bacteria In Manufacturing Grade Raw Milks

1991 ◽  
Vol 54 (11) ◽  
pp. 861-867 ◽  
Author(s):  
S. R. TATINI ◽  
P. MEKALA ◽  
A. EL-HABAZ ◽  
M. W. GRIFFITHS
Keyword(s):  
Rapid Detection ◽  
Bacterial Count ◽  
Raw Milk ◽  
Plate Count ◽  
Psychrotrophic Bacteria ◽  
Milk Samples ◽  
Microscopic Count ◽  
Direct Epifluorescent Filter Technique ◽  
Native Microflora

Methods to rapidly assess the bacteriological quality of raw milk were investigated. Whereas direct microscopic count, modified psychrotrophic plate count, and direct epifluorescent filter technique (DEFT) did not correlate well with initial psychrotrophic bacterial count of raw milk, improvements were obtained after preincubation of the milk samples. The best preincubation conditions were identified as 30°C for 6 h, 21°C for 10 h, 13°C for 15 h, 13°C for 20 h, or 7°C for 37 h. The “square root” equation was applied to the data, and a model was produced for predicting growth of the native microflora of raw milk. Using this equation, a DEFT count after preincubation of the milk at 21°C for 10 h could accurately predict the initial psychrotroph count and the count after storage of the milk at 6°C for 48 h.

scholarly journals Determination of Four Fluoroquinolones in Milk by Liquid Chromatography

1997 ◽  
Vol 80 (5) ◽  
pp. 982-987 ◽  
Author(s):  
José E Roybal ◽  
Allen P Pfenning ◽  
Sherri B Turnipseed ◽  
Calvin C Walker ◽  
Jeffrey A Hurlbut
Keyword(s):  
Fluorescence Detection ◽  
Solid Phase ◽  
Raw Milk ◽  
Extraction Column ◽  
Isocratic Elution ◽  
Standard Curve ◽  
Milk Samples ◽  
Relative Standard ◽  
Liquid Chromatographic

Abstract A liquid chromatographic (LC) method with fluorescence detection is presented for the analysis of 4 fluoroquinolones; enrofloxacin (ENRO), ciprofloxacin (CIPRO), sarafloxacin (SARA), and difloxacin (DIFLX) in milk. The procedure consists of extraction of milk with acidified ethanol, isolation and retention on a cation exchange solid-phase extraction column, elution with basic methanol, and LC analysis with fluorescence detection. LC analysis is performed by isocratic elution using an acetonitrile-2% acetic acid (15 + 85) mobile phase and an Inertsil phenyl column with fluorescence detection at excitation and emission wavelengths of 278 and 450 nm, respectively. A target level of 10 ppb for each of the 4 fluoroquinolones has been established for this method. Average recovery from fortified raw milk samples (5-100 ppb each) based on a 5-point standard curve calculation was 70-90%, with relative standard deviations of &lt;15%.

Preliminary Incubation Count as an Index of Raw Milk Microbiological Quality During Storage

1984 ◽  
Vol 47 (3) ◽  
pp. 206-208 ◽  
Author(s):  
J. J. RYAN ◽  
R. H. GOUGH ◽  
C. H. WHITE
Keyword(s):  
Microbiological Quality ◽  
Storage Period ◽  
Raw Milk ◽  
Plate Count ◽  
Bacterial Counts ◽  
Sample Group ◽  
Psychrotrophic Bacteria ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Standard Plate

During a 5-month period, 200 raw milk samples were collected from two Louisiana milk plants. Standard Plate Count (SPC), Psychrotrophic Bacteria Count (PBC), and Proteolytic Count (PC) of each sample were initially determined, then monitored daily during a 5-d storage period at 2.2°C. As hypothesized, all bacterial counts increased during the storage period. The magnitude of the increase in bacterial numbers during storage was further investigated by dividing the milk samples into bacteriologically acceptable and unacceptable groups based on SPC or Preliminary Incubation (PI) count. An SPC of 1.0 × 105/ml and PI counts of 1.0 × 105/ml, 1.5 × 105/ml, 2.3 × 105/ml, and 3.0 × 105/ml were used to repeatedly dichotomize the 200 raw milk samples into two groups. Median SPC, PBC, and PC for each acceptable and unacceptable group were then calculated. Dichotomization based on PI counts yielded acceptable sample groups having consistently lower bacterial counts during storage than did the acceptable sample group, which resulted from the dichotomization based on a SPC of 1.0 × 105/ml. The results of this study indicated that the PI count is of considerable value for raw milk quality control.

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