Immunodetection of lactosylated proteins as a useful tool to determine heat treatment in milk samples

The primary objective of this study is to validate a new fast method for determination of uric acid in milk. The method is based on an enzymatic-fluorometric technique that requires minimal pre-treatment of milk samples. The present determination of uric acid is based on the enzymatic oxidation of uric acid to 5-hydroxyisourate via uricase where the liberated hydrogen peroxide reacts with 10-acetyl-3,7-dihydroxyphenoxazine via peroxidase and the fluorescent product, resorufin, is measured fluorometrically. Fresh composite milk samples (n=1,072) were collected from both Jersey (n=38) and Danish Holstein (n=106) cows from one local herd. The average inter- and intra-assay variations were 7·1% and 3·0%, respectively. Percent recovery averaged 103·4, 107·0 and 107·5% for samples spiked with 20, 40 or 60 μmof standard, respectively, with a correlation (r=0·98;P<0·001) observed between the observed and expected uric acid concentrations. A positive correlation (r=0·96;P<0·001) was observed between uric acid concentrations using the present method and a reference assay. Storage at 4°C for 24 h resulted in lower (P<0·01) uric acid concentrations in milk when compared with no storage or samples stored at −18°C for 24 h. Addition of either allopurinol (a xanthine oxidase inhibitor) or dimethylsulfoxide (a solvent for allopurinol) did not affect milk uric acid concentrations (P=0·96) and may indicate that heat treatment before storage and analysis was sufficient to degrade xanthine oxidase activity in milk. No relationship was observed between milk uric acid and milk yield and milk components. Authors recommend a single heat treatment (82°C for 10 min) followed by either an immediate analysis of fresh milk samples or storage at −18°C until further analysis.

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SOME OBSERVATIONS ON THE BACTERIOLOGICAL KEEPING QUALITY OF MILK PROCESSED BY HIGH TEMPERATURES WITH A 0.6 SECOND HOLDING TIME1 2

Journal of Milk and Food Technology ◽

10.4315/0022-2747-26.10.332 ◽

1963 ◽

Vol 26 (10) ◽

pp. 332-336 ◽

Cited By ~ 2

Author(s):

D. A. Evans ◽

Eleanor L. Lachman ◽

Warren Litsky

Keyword(s):

Heat Treatment ◽

Raw Milk ◽

Plate Heat Exchanger ◽

Plate Heat ◽

Milk Samples ◽

Whole Milk ◽

Keeping Quality ◽

Quality Of Milk ◽

Sterilized Milk

Summary Raw milk was processed through a commercial sized plate heat exchanger at temperatures of 160 F through 260 F with a 0.6 sec hold. Milk samples were collected at increments of 10 F during processing and analyzed for psychrophilic, mesophilic and thermophilic counts initially and at weekly intervals thereafter. All samples were held at 40 F after processing. Results indicated that temperatures of processing at 160 F and 170 F were not sufficient to impart acceptable keeping qualities to whole milk held at 40 F for a period of one week. By comparison, processing temperatures of 180 F through 210 F with 0.6 sec hold appeared to impart to whole milk keeping qualities which were approximately comparable to those observed in milk pasteurized according to present standards. When heat treatment in the range of 220 F through 260 F were used, it was indicated that bacteriological keeping quality of the milk was improved to an extent far beyond that experienced with present day commercial pasteurization. There appeared to be somewhat of a tendency for higher count raw milk related to the level of population in the processed product although the magnitude of this relationship was not clearly defined in all cases. It was evident that this process did not produce “commercially sterilized” milk at the processing temperatures and holding time used.

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Impact of heat treatment and acid gelation on polyphenol enriched milk samples

LWT ◽

10.1016/j.lwt.2019.108282 ◽

2019 ◽

Vol 113 ◽

pp. 108282 ◽

Cited By ~ 1

Author(s):

Mukaddes Kılıç Bayraktar ◽

Niamh B. Harbourne ◽

Colette C. Fagan

Keyword(s):

Heat Treatment ◽

Milk Samples ◽

Acid Gelation ◽

Enriched Milk

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Rennet coagulation of heated milk: influence of pH adjustment before or after heating

Journal of Dairy Research ◽

10.1017/s0022029900026030 ◽

1988 ◽

Vol 55 (2) ◽

pp. 205-215 ◽

Cited By ~ 40

Author(s):

Harjinder Singh ◽

Samweul I. Shalabi ◽

Patrick F. Fox ◽

Albert Flynn ◽

Anne Barry

Keyword(s):

Heat Treatment ◽

Adverse Effect ◽

Adverse Effects ◽

Skim Milk ◽

Ph Adjustment ◽

Milk Samples ◽

Heated Milk ◽

Rennet Coagulation ◽

Low Concentrations ◽

Influence Of Ph

SummaryThe rennet coagulation times of infant milk formulae or fresh skim milk (milk) samples heated at temperatures in the range 70–140 °C for 1–10 min decreased on acidification, usually to pH < 6·0. Heated milk samples acidified to pH 5·5 and reneutralized to pH 6·6 retained good rennet coagulability. Acidification of such milk samples before heating also reduced the adverse effect of severe heat treatment (95 °C for 1 min) on rennet coagulation. Addition of low concentrations of CaCl2 to heated milks offset the adverse effects of heating. Acidification of heated milks increased the [Ca2+], and reneutralization of acidified milk only partly restored the [Ca2+], i.e. acidified/reneutralized milk had a higher [Ca2+] than normal milk, suggesting this as the mechanism via which acidification/neutralization improves the rennet coagulability of heated milk. Approximately 50% of the whey protein can be incorporated into rennet gels in heated milks while retaining good coagulability and curd tension; this may be a useful technique for increasing cheese yield.

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Chemiluminescent determination of xanthine oxidase activity in milk

Journal of Dairy Research ◽

10.1017/s002202999900360x ◽

1999 ◽

Vol 66 (3) ◽

pp. 441-448 ◽

Cited By ~ 1

Author(s):

STEFANO GIROTTI ◽

SANDRO LODI ◽

ELIDA FERRI ◽

GRAZIELLA LASI ◽

FABIANA FINI ◽

...

Keyword(s):

Heat Treatment ◽

Enzyme Activity ◽

Detection Limit ◽

Sample Preparation ◽

Xanthine Oxidase ◽

Milk Sample ◽

Uht Milk ◽

Milk Samples ◽

Chemiluminescent Method

A chemiluminescent method for determining xanthine oxidase (XOD) activity was developed and applied to the assay of milk enzyme activity using a photomultiplier luminometer. Various kinds of milk and cream samples were analysed for XOD content. In pasteurized milk, XOD activity depended on the fat content and in UHT milk it disappeared owing to the heat treatment. Milk sample preparation was very simple, requiring only homogenization at 40°C followed by a 1[ratio ]10 dilution with UHT (‘XOD-free’) milk. The assay was carried out at 25°C. The response obtained from XOD standard solutions in milk was linear from 0·1 to 500 enzyme units (U) l−1, but for the actual milk samples values ranged only from 1 to 135 U l−1. The detection limit at 2 SD was 0·1 U l−1 in milk, while in buffer it was 100 times lower. The intra-assay and interassay CV for XOD activity in milk were 6–12%.

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The influence of various factors on milk clotting time

Journal of Agricultural Sciences Belgrade ◽

10.2298/jas0201057j ◽

2002 ◽

Vol 47 (1) ◽

pp. 57-73

Author(s):

Snezana Jovanovic ◽

Ognjen Macej ◽

Jelena Djurdjevic-Denin

Keyword(s):

Heat Treatment ◽

Coagulation Factors ◽

Clotting Time ◽

Coagulation Rate ◽

Milk Clotting ◽

Milk Samples ◽

Heat Treated ◽

Milk Coagulation ◽

C 30 ◽

Influence Of Ph

The influence of pH (6.5 and 5.8), amount of added CaCl2 (0, 200 and 400 mg/l)), coagulation temperature (30?C and 35?C) and heat treatment of milk (65?C/30 min and 87?C/10 min) on the rate of rennet induced milk coagulation (s) were investigated. The time (s) from rennet addition to onset of gelation (as indicated by the first visible floccules) was measured. The milk samples heat-treated at 87?C/10 min, with 400 mg/l added CaCl2, which were coagulated at 35?C and pH 5.8, coagulated 23.28-fold faster than the same samples without added CaCl2, which were coagulated at 30?C and pH 6.5. The results of investigations related to the influence of particular coagulation factors on the coagulation rate of heat-treated milk showed that at pH 6.5 the most pronounced influence was demonstrated by the amount of Ca2+ and temperature of coagulation. At pH 5.8, different amounts of Ca2 and used temperatures of coagulation did not influence coagulation rate regardless of the used heat treatment of milk. The influence of used heat treatment of milk was particularly pronounced during coagulation of samples without added CaCl2 that coagulated at 30?C and pH 6.5. The used heat treatment of milk practically did not influence the milk coagulation rate at pH 5.8. The greatest influence on milk coagulation rate was showed by pH. This influence was the most marked in coagulation of samples in which the coaggregates were formed, regardless of the amount of added Ca2+ and used coagulation temperatures.

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The influence of applied heat treatments on whey protein denaturation

Journal of Agricultural Sciences Belgrade ◽

10.2298/jas0202205f ◽

2002 ◽

Vol 47 (2) ◽

pp. 205-218

Author(s):

Safet Fetahagic ◽

Ognjen Macej ◽

Jelena Denin-Djurdjevic ◽

Snezana Jovanovic

Keyword(s):

Heat Treatment ◽

Whey Protein ◽

Protein Denaturation ◽

Skim Milk ◽

Heat Treatments ◽

Matter Content ◽

90 C 10 ◽

Milk Samples ◽

Heat Treated ◽

Sera Samples

Reconstituted skim milk with 8.01% DM was standardized with 3% skim milk powder and with 3% demineralized whey powder (DWP), respectively. Gained milk samples are named as 8%, 11% and 8%+3%DWP. All samples were heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min, respectively. Untreated milk was used as control. Milk samples were coagulated by glucono-d-lactone (GDL) at the temperature of 45?C until pH 4.60 was reached. Milk nitrogen matter content decreased during heat treatments, but linear relationship between applied heat treatments and nitrogen matter decreasing was not found. Nitrogen matter content of sera gained from both untreated and heat treated milk increased with the increase of milk dry matter content and with the addition of DWP. The higher temperature of applied heat treatment, the smaller sera nitrogen matter content. Nitrogen matter content in sera obtained from untreated milk were 64.90 mg%, 96.80 mg% and 117.3 mg% for milk 8%, 11% and 8%+3.0% DWP, respectively. Sera samples obtained from milk 8% heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min had 38.70 mg% 38.30 mg% and 37.20 mg% of nitrogen matter, respectively. Sera samples obtained from milk 11% heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min had 55.90 mg%, 52.80 mg% and 51.30 mg% of nitrogen matter, respectively. Sera samples obtained from milk 8% heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min had 69.50 mg%, 66.20 mg% and 66.00 mg% of nitrogen matter respectively. Distribution of nitrogen matter from untreated milk to milk sera were 12.01%, 11.14% and 17.69% for milk 8%, 11% and 8%+3.0% DWP respectively. Distribution of nitrogen matter from milk 8% heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min to sera samples were 6.99%, 6.72% and 6.59%, respectively. Distribution of nitrogen matter from milk 11% heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min to sera samples, were 6.02%, 5.32% and 5.21%, respectively. Distribution of nitrogen matter from milk 8%+3%DWP heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min to sera samples were 9.64%, 8.66% and 8.67%, respectively. Whey protein denaturation increased with increasing of the temperature of the applied heat treatment. Denaturation was the most significant for milk sample 11%.

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Microbiological Examination of Pasteurized, Deaerated Human Milk

Journal of Food Protection ◽

10.4315/0362-028x-52.8.552 ◽

1989 ◽

Vol 52 (8) ◽

pp. 552-559 ◽

Cited By ~ 1

Author(s):

MICHAEL T. MUSGROVE ◽

MARK A. HARRISON ◽

HAROLD M. BARHNART ◽

ROMEO T. TOLEDO ◽

RONALD R. EITENMILLER

Keyword(s):

Heat Treatment ◽

Dissolved Oxygen ◽

Human Milk ◽

Oxygen Content ◽

Species Level ◽

Processing Conditions ◽

Gram Negative ◽

Milk Samples ◽

Microbiological Examination ◽

Skin Commensals

Three composites of human milk samples were subjected to different processing conditions: (1) deaerated, vacuum packaged in metalized polyester bags and pasteurized at 56°C for 8 min; (2) vacuum packaged and pasteurized; (3) vacuum packaged. On days 0, 4, 7, 14, 28, 64, and 96 of storage, each treatment was analyzed for dissolved oxygen content and viable microflora. On days 0, 4, and 14, randomly selected isolates from each treatment were identified to the species level. Heat treatment of the milk samples reduced the number of viable microorganisms and resulted in a shift in the type of bacteria in the milk. Pasteurized samples contained primarily non-pathogenic skin commensals, while non-pasteurized samples were populated by species of Pseudomonas and other Gram negative microorganisms, including potential pathogens. Deaeration did not affect either the number or types of microorganisms surviving the heat treatment.

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Occurrence of False-Positive Results of Inhibitor on Milk Samples Using the Delvotest SP Assay

Journal of Food Protection ◽

10.4315/0362-028x-64.8.1211 ◽

2001 ◽

Vol 64 (8) ◽

pp. 1211-1215 ◽

Cited By ~ 10

Author(s):

JEONG-HUN KANG ◽

FUSAO KONDO

Keyword(s):

Heat Treatment ◽

Positive Result ◽

False Positive ◽

Reading Time ◽

False Positive Result ◽

Bulk Tank Milk ◽

Milk Samples ◽

Cell Counts ◽

Bulk Tank ◽

Positive Results

Three hundred twenty-one quarter, 207 whole udder, 310 bulk tank, and 93 tank-lorry milk samples were examined for confirmation of the presence of inhibitor by Delvotest SP assay. Four hundred twenty-six Holstein cows of no drug treatment for at least 30 days from January 1998 to September 1999 were used. Reading time was 2.50, 2.75, and 3.00 h, and results of sampling were recorded by four types according to comparison with the color of the well containing the control milk sample. False-positive outcome was identified by Delvotest SP assay in quarter (13 of 321), whole udder (9 of 207), and bulk tank milk samples (4 of 310), but was not shown on tank-lorry milk samples (0 of 93) at the reading time of 2.50 h. All of the 26 false-positive samples were negative from the examination after heat treatment at 82°C for 5 min. But, two bulk tank milk samples that appeared to have positive results in LacTek and Charm II tests were positive from the test following heat treatment. Somatic cell counts (SCC) were related to the probability of a false-positive result. The more SCC increased, the more the occurrence of a false-positive result increased. In our investigations, 4 of 310 bulk tank milk samples at the reading time of 2.50 h produced false-positive results, and no false-positive results were apparent at a reading time of 2.75 h. Also, the occurrence of false-positive results in quarter and whole udder milk samples decreased when agar was cultured for 2.75 to 3.00 h. There were no false-positive results from tank-lorry milk samples. These results indicate that the Delvotest SP assay may provide a suitable means for the detection of drug residues in not only quarter and whole udder milk of cows but also in bulk tank and tank-lorry milk following reading times of 2.75 to 3.00 h.

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Heat Treatment Effects on the Antimicrobial Activity of Macrolide and Lincosamide Antibiotics in Milk

Journal of Food Protection ◽

10.4315/0362-028x.jfp-10-297 ◽

2011 ◽

Vol 74 (2) ◽

pp. 311-315 ◽

Cited By ~ 19

Author(s):

M. A. ZORRAQUINO ◽

R. L. ALTHAUS ◽

M. ROCA ◽

M. P. MOLINA

Keyword(s):

Heat Treatment ◽

Antimicrobial Activity ◽

Linear Regression ◽

Growth Inhibition ◽

Linear Regression Model ◽

Micrococcus Luteus ◽

Multiple Linear Regression Model ◽

Antibiotic Residues ◽

Milk Processing ◽

Milk Samples

Antibiotic residues in milk can cause serious problems for consumers and the dairy industry. Heat treatment of milk may diminish the antimicrobial activity of these antibiotic residues. This study analyzed the effect of milk processing (60°C for 30 min, 120°C for 20 min, and 140°C for 10 s) on the antimicrobial activity of milk samples fortified with three concentrations of three macrolides (erythromycin: 20, 40 and 80 μg/liter; spiramycin: 100, 200, and 400 μg/liter; and tylosin: 500, 1,000, and 2,000 μg/liter) and one lincosamide (lincomycin: 1,000, 2,000, and 4,000 μg/liter). To measure the loss of antimicrobial activity, a bioassay based on the growth inhibition of Micrococcus luteus was done. The data were analyzed using a multiple linear regression model. The results indicate that treatment at 120°C for 20 min produces inactivation percentages of 93% (erythromycin), 64% (spiramycin), 51% (tylosin), and 5% (lincomycin), while treatment at 140°C for 10 s results in generally lower percentages (30% erythromycin, 35% spiramycin, 12% tylosin, and 5% lincomycin). The lowest loss or lowest reduction of antimicrobial activity (21% erythromycin and 13% spiramycin) was obtained by treatment at 60°C for 30 min.

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