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

LWT ◽  
2019 ◽  
Vol 113 ◽  
pp. 108282 ◽  
Author(s):  
Mukaddes Kılıç Bayraktar ◽  
Niamh B. Harbourne ◽  
Colette C. Fagan
Keyword(s):  
Heat Treatment ◽  
Milk Samples ◽  
Acid Gelation ◽  
Enriched Milk

Fluorometric determination of uric acid in bovine milk

2010 ◽  
Vol 77 (4) ◽  
pp. 438-444 ◽  
Author(s):  
Torben Larsen ◽  
Kasey M Moyes
Keyword(s):  
Heat Treatment ◽  
Uric Acid ◽  
Xanthine Oxidase ◽  
Bovine Milk ◽  
Oxidase Inhibitor ◽  
Enzymatic Oxidation ◽  
Fast Method ◽  
Xanthine Oxidase Inhibitor ◽  
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.

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

The Analyst ◽  
2001 ◽  
Vol 126 (1) ◽  
pp. 66-70 ◽  
Author(s):  
Micaela Pallini ◽  
Dario Compagnone ◽  
Giuseppe Palleschi ◽  
Stefania Di Stefano ◽  
Stefano Marini ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Milk Samples

Comparison of pressure treatment and heat treatment of skim milk with added starch on subsequent acid gelation of milk

LWT ◽  
2011 ◽  
Vol 44 (4) ◽  
pp. 1189-1198 ◽  
Author(s):  
H.E. Oh ◽  
M. Wong ◽  
D.N. Pinder ◽  
S.G. Anema
Keyword(s):  
Heat Treatment ◽  
Skim Milk ◽  
Pressure Treatment ◽  
Acid Gelation ◽  
Subsequent Acid

scholarly journals Changes in the acid gelation of skim milk as affected by heat-treatment and alkaline pH conditions

2007 ◽  
Vol 87 (2) ◽  
pp. 119-137 ◽  
Author(s):  
Fanny Guyomarc’h ◽  
Orlane Mahieux ◽  
Marie Renan ◽  
Marc Chatriot ◽  
Valérie Gamerre ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Skim Milk ◽  
Alkaline Ph ◽  
Ph Conditions ◽  
Acid Gelation

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

1963 ◽  
Vol 26 (10) ◽  
pp. 332-336 ◽  
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.

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

1988 ◽  
Vol 55 (2) ◽  
pp. 205-215 ◽  
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.

Chemiluminescent determination of xanthine oxidase activity in milk

1999 ◽  
Vol 66 (3) ◽  
pp. 441-448 ◽  
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%.

scholarly journals The influence of various factors on milk clotting time

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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