scholarly journals The influence of investigated factors on viscosity of stirred yogurt

2002 ◽  
Vol 47 (2) ◽  
pp. 219-231 ◽  
Author(s):  
Jelena Denin-Djurdjevic ◽  
Ognjen Macej ◽  
Snezana Jovanovic
Keyword(s):  
Milk Sample ◽  
Skim Milk ◽  
Streptococcus Thermophilus ◽  
Matter Content ◽  
Lactobacillus Delbrueckii ◽  
Dry Matter Content ◽  
90 C 10 ◽  
Milk Samples ◽  
Heat Treated ◽  
Control Milk

Skim milk was reconstituted to obtain milk with 8.44% DM, which was standardized with demineralized whey powder (DWP) to obtain milk sample A (9.71% DM) and milk sample B (10.75% DM). Milk samples were heat treated at 85?C/20 min and 90?C/10 min, respectively. Untreated milk was used as control. Milk samples were inoculated with 2.5% of commercial yogurt culture (containing Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in the ratio 1:1) at 43?C. Samples were incubated until pH 4.6 was reached. Samples were immediately cooled to 4?C and held at that temperature until analyses. Samples of acid casein gels were stirred after 1, 7 and 14 days of storage. Measurements of viscosity were done with Brookfield DV-E Viscometer. Spindle No 3 at 30 rpm was used for all samples. Duration of fermentation decreased when DWP was used for standardization of milk dry matter content. Yogurt samples produced from milk heat treated at 85?C/20 min, obtained by stirring of gel 1 day after production had a higher viscosity than sample produced from milk heat treated at 90?C/10 min. On the other hand, samples produced from milk heat treated at 90?C/10 min had a greater viscosity after 7 and 14 days of storage, which indicates a greater hydrophilic properties and a more pronounced swelling of casein micelles.

scholarly journals Viscosity of set-style yogurt as influenced by heat treatment of milk and added demineralized whey powder

2002 ◽  
Vol 47 (1) ◽  
pp. 45-56 ◽  
Author(s):  
Jelena Djurdjevic-Denin ◽  
Ognjen Macej ◽  
Snezana Jovanovic
Keyword(s):  
Heat Treatment ◽  
Milk Powder ◽  
Skim Milk ◽  
Matter Content ◽  
Lactobacillus Delbrueckii ◽  
Dry Matter Content ◽  
90 C 10 ◽  
Milk Samples ◽  
Whey Powder ◽  
Heat Treated

Skim milk powder was reconstituted to obtain milk A (with 8.44% TS). Milk sample A was standardized with different amounts of demineralized whey powder (DWP) to obtain milk B (with 9.71% TS) and milk C (with 10.75% TS). Milk samples were heat treated at 85?C/20 min and 90?C/10 min, respectively. Untreated milk was used as control. Milk samples were inoculated with 2.5% of commercial yogurt culture (containing Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in the ratio 1:1) at 43?C. Samples were incubated until pH 4.6 was reached. Samples were immediately cooled to 4?C and held at that temperature until analyses. Measurements of viscosity were done with Brookfield DV-E Viscometer. Spindle No 3 at 20 rpm was used for all samples. After 1 day of storage, set-style yogurt samples produced from untreated milk had the highest, while samples produced from milk heat treated at 90?C/10 min the smallest initial viscosity, regadless of the dry matter content and composition. Average viscosity of set-style yogurts decreased with intensifying temperature of applied heat-treatment. During storage, set-style yogurt samples produced from milk heat treated at 90?C/10 min had the least pronounced decrease of viscosity during shearing. After 14 days of storage, set-style yogurt samples produced from milk standardized with demineralized whey powder had higher viscosity than samples produced from basis milk.

scholarly journals The influence of dry matter, applied heat treatment and storage period on the viscosity of stirred yogurt

2002 ◽  
Vol 47 (2) ◽  
pp. 189-204 ◽  
Author(s):  
Jelena Denin-Djurdjevic ◽  
Ognjen Macej ◽  
Snezana Jovanovic
Keyword(s):  
Heat Treatment ◽  
Dry Matter ◽  
Milk Powder ◽  
Skim Milk ◽  
Storage Period ◽  
Matter Content ◽  
Lactobacillus Delbrueckii ◽  
Dry Matter Content ◽  
90 C 10 ◽  
Heat Treated

Skim milk powder reconstituted to 8.44% TS, 9.65% TS and 10.84% TS respectively was used for investigation. Untreated milk and milk heat treated at 85?C/20 min and 90?C/10 min, respectively, were used for the investigation. Milk was inoculated with 2.5% of yogurt culture (containing Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in the ratio 1:1) at 43?C. Samples were incubated until pH 4.6 was reached. Samples were immediately cooled to 4?C and held at that temperature during 14 days. Acid casein gel was stirred after 1, 7 and 14 days of storage. Measurements were done at 30 rpm during 2 min, at 20?C. According to the investigation, it could be concluded that both applied heat treatment and dry matter content influence viscosity of stirred yogurt. Viscosity increases when dry matter content increases. The smallest viscosity had yogurt produced from untreated milk with 8.44% TS, while samples produced from milk with 10.84% TS had the highest viscosity. Applied heat treatments had significant influence on viscosity of yogurt gained by stirring of acid casein gels after 7 and 14 days of storage. Stirred yogurt produced from milk heat treated at 90?C/10 min had a higher viscosity than samples produced from milk heat treated at 85?C/20 min. Storage period influenced average viscosity of stirred yogurt. Samples of stirred yogurt produced from milk with 8.44% TS showed a decrease of average viscosity during storage regardless of the applied heat treatment of milk. The highest average viscosity had samples produced from milk with 10.84% TS.

scholarly journals The influence of applied heat treatments on whey protein denaturation

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%.

scholarly journals The influence of GDL concentration on milk pH change during acid coagulation

2002 ◽  
Vol 47 (1) ◽  
pp. 75-85 ◽  
Author(s):  
Safet Fetahagic ◽  
Ognjen Macej ◽  
Jelena Denin-Djurdjevic ◽  
Snezana Jovanovic
Keyword(s):  
Buffer Capacity ◽  
Milk Powder ◽  
Skim Milk ◽  
Skim Milk Powder ◽  
90 C 10 ◽  
Ph Change ◽  
Protein Ratio ◽  
Milk Samples ◽  
Ph Values ◽  
Heat Treated

Skim milk powder was reconstituted to obtain milk A (with 8.01% TS). Milk A was standardized with 3% of skim milk powder and 3% of demineralized whey powder (DWP), respectively, to obtain milk B (with 11.15% TS) and milk C (with 11.10% TS). Milk 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. Acidification was carried out at 25?C, 35?C and 45?C during 240 min with GDL (glucono-d-lactone), namely with the amount of 0.5%, 0.75%, 1.0%, 1.25% 1.5%, 1.75%, 2.0% and 3.0% of GDL, respectively. The results showed that all investigated factors, explicitly GDL concentration, acidification temperature and applied heat treatment of milk as well as added DWP influence the change of pH during acidification. Milk samples standardized with DWP had smaller buffer capacity and faster change of pH than samples standardized with skim milk powder. Only at acidification temperature of 25?C, added DWP did not influence the change of milk buffer capacity regardless of the change of casein:whey protein ratio. Under this acidification condition, both milk samples standardized with skim milk powder and DWP had similar final pH values.

scholarly journals Influence of selected factors on the viscosity of set style yogurt and acid casein gel at constant speed of spindle rotation

2004 ◽  
Vol 49 (2) ◽  
pp. 233-250 ◽  
Author(s):  
Safet Fetahagic ◽  
Jelena Denin-Djurdjevic ◽  
Snezana Jovanovic ◽  
Ognjen Macej
Keyword(s):  
Linear Relationship ◽  
Dry Matter ◽  
Heat Treatments ◽  
Matter Content ◽  
Constant Speed ◽  
Dry Matter Content ◽  
Milk Samples ◽  
Heat Treated ◽  
Spindle Rotation

The influence of milk dry matter (DM) content (8.20%, 9.27% and 10.28%) and applied heat treatments (untreated milk and milk heat-treated at 90oC/10?) on the viscosity of set-style yogurt and acid casein gel gained by acidification with GDL (glucono-d-lactone) has been investigated. Viscosity was measured during the time of 3 minutes at constant speed of spindle rotation of 20 rpm. The results have shown that yogurt samples produced from untreated milk had higher viscosity values than samples produced from heat-treated milk. An increase of dry matter content influenced the increase of viscosity of yogurt samples produced from both untreated milk and heat-treated milk. Samples with 10.28% DM had the highest viscosity values. An increase of DM content in samples of acid casein gel produced by acidification with GDL had an opposite influence. The samples with smallest DM content had the highest viscosity values. There is no linear relationship between the period of storage of set-style yogurt produced from heat-treated milk and viscosity value.

scholarly journals Sestavení kompetitivní enzymové imunoanalýzy pro stanovení α-laktalbuminu  a β-laktoglobulinů kravského mléka

1999 ◽  
Vol 17 (No. 1) ◽  
pp. 5-14 ◽  
Author(s):  
L. Karasova ◽  
P. Rauch ◽  
L. Fukal
Keyword(s):  
Capillary Electrophoresis ◽  
Milk Sample ◽  
Polyclonal Antibodies ◽  
Whey Proteins ◽  
The Other ◽  
Milk Samples ◽  
Heat Treated ◽  
Very High ◽  
Raw Cow’S Milk

Polyclonal antibodies were raised against three immunogens- a-lactalbumin (LA), -lactoglobulin A (LGA) and B (LGB). Using these antibodies the procedures of an indirect competitive enzyme immunoassay (ELISA) were constructed, optimized a nd characterized for determination of indi vidual immunogens. It was found that ELISA of LA is very specific without any inter­ ferences of other whey proteins. However, in ELlSAs of both lactoglobulins A and B were demonstrated very high interferences of the other genetic varian t (cross-reactivities  20-280% depending on antibody and immu nogen). An excellent sensitivity of ELISA for all proteins (detection limits for LA, LGA and LGB were 13, 0.4 and 54 ng/ml, respectively) makes it possible to analyze milk samples diluted more than 1000 times. Average values of variation coefficient were in the range 16-27%. A compari­ son of whey protein determinations in raw cow's milk by ELISA and by capillary electrophoresis resulted in the best similarit y in results of LA concentration. The decrease of LA, LGA and LGB concen trations was detected by using capillary electrophoresis for an analysis of whey from heat-treated milk, while ELISA of the same milk sample showed the increase of LGB immunoreac­ tivity to 700%.

scholarly journals Anti-staphylococcal effect of cinnamaldehyde in milk

2020 ◽  
Vol 33 (2) ◽  
pp. 108-116
Author(s):  
Milijana Babic ◽  
Milica Glisic ◽  
Jasna Djordjevic ◽  
Nemanja Zdravkovic ◽  
Radoslava Savic-Radovanovic ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
High Temperature ◽  
Milk Sample ◽  
Low Fat ◽  
Pasteurized Milk ◽  
Milk Samples ◽  
Colony Forming Units ◽  
Control Milk ◽  
Ultra High Temperature

The survival of Staphylococcus aureus in inoculated (105 colony forming units [CFU]/mL) 3.2% and 0.5% fat ultra-high temperature-pasteurized milk samples containing 0%, 0.05%, or 0.1% cinnamaldehyde stored at 4°C or 10°C was evaluated within 15 days. S. aureus populations reached 7.92 (0.5% fat) and 7.95 (3.2% fat) log CFU/mL in control milk samples stored at 10°C, while in milk sample stored at 4°C, S. aureus counts remained almost unchanged. At the end of the study, the number of this pathogen decreased by 1.52–4.04 log CFU/mL in milk treated with cinnamaldehyde. The greatest anti-staphylococcal effect was achieved in low-fat milk at 10°C and treated with 0.1% cinnamaldehyde.

scholarly journals Enhancement of the Molecular and Serological Assessment of Hepatitis E Virus in Milk Samples

2020 ◽  
Vol 8 (8) ◽  
pp. 1231
Author(s):  
Ibrahim M. Sayed ◽  
Ahmed R. A. Hammam ◽  
Mohamed Salem Elfaruk ◽  
Khalid A. Alsaleem ◽  
Marwa A. Gaber ◽  
...  
Keyword(s):  
Milk Sample ◽  
Hepatitis E Virus ◽  
Skim Milk ◽  
Hepatitis E ◽  
Rna Detection ◽  
Extraction Procedures ◽  
Milk Samples ◽  
Milk Serum ◽  
Whole Milk ◽  
Spin Column

Hepatitis E virus (HEV) infection is endemic in developing and developed countries. HEV was reported to be excreted in the milk of ruminants, raising the possibility of transmission of HEV infection through the ingestion of contaminated milk. Therefore, the detection of HEV markers in milk samples becomes pivotal. However, milk includes inhibitory components that affect HEV detection assays. Previously it was reported that dilution of milk matrix improves the performance of HEV molecular assay, however, the dilution of milk samples is not the best strategy especially when the contaminated milk sample has a low HEV load. Therefore, the objective of this study is to compare the effect of extraction procedures on the efficiency of HEV RNA detection in undiluted milk samples. In addition, we assessed the effect of the removal of milk components such as fats and casein on the performance of the molecular and serological assays of HEV. Phosphate buffered saline (PBS) and different milk matrices (such as whole milk, skim milk, and milk serum) were inoculated with different HEV inoculums and subjected to two different extraction procedures. Method A includes manual extraction using spin column-based extraction, while method B includes silica-based automated extraction. Method A was more sensitive than method B in the whole milk and skim milk matrices with a LoD95% of 300 IU/mL, and virus recovery yield of 47%. While the sensitivity and performance of method B were significantly improved using the milk serum matrix, with LoD95% of 96 IU/mL. Interestingly, retesting HEV positive milk samples using the high sensitivity assay based on method B extraction and milk serum matrix increased the HEV RNA detection rate to 2-fold. Additionally, the performance of HEV serological assays such as anti-HEV IgG and HEV Ag in the milk samples was improved after the removal of the fat globules from the milk matrix. In conclusion, HEV RNA assay is affected by the components of milk and the extraction procedure. Removal of inhibitory substances, such as fat and casein from the milk sample increased the performance of HEV molecular and serological assays which will be suitable for the low load HEV milk with no further dilutions.

scholarly journals Development of turbidity index as field method to detect mixing of heated milk with raw milk

2014 ◽  
Vol 43 (2) ◽  
pp. 123-127
Author(s):  
MRH Rakib ◽  
R Habib ◽  
MN Hassan ◽  
MF Imam ◽  
MN Hassan
Keyword(s):  
Milk Sample ◽  
Dry Matter ◽  
Raw Milk ◽  
Field Method ◽  
Matter Content ◽  
Ash Content ◽  
Dry Matter Content ◽  
Heated Milk ◽  
Significant Difference ◽  
C 50

The research was undertaken to determine the amounts of precipitate formed in the milk plasma due to mixing of different levels of heated milk with raw milk, and to establish a turbidity index, which will be helpful as a field method in detecting the extent of addition of heated milk. The tests were conducted on five different treatments namely, Milk sample A (100% Heated milk), Milk sample B (75% Heated milk + 25% Raw milk), Milk sample C (50% Heated milk + 50% Raw milk), Milk sample D (25% Heated milk + 75% Raw milk) and Milk sample E (100% Raw milk). Samples were examined by chemical analysis including fat content, protein content, dry matter content, ash content, pH, acidity, turbidity test, and precipitation content of plasma. There was a highly significant difference (p<0.001) in case of fat, protein and precipitate contents of plasma as affected by extent of addition of heated milk. A statistically significant difference (p<0.05) was also found for ash content. On the other hand, no significant difference was found in case of dry matter content, pH and acidity of milk. A strong correlation (R2=0.819) was observed between the amount of precipitate and proportion of heated milk mixed with raw milk. A field method was devised on the basis of extent of turbidity, which was in fact amount of precipitate formed in the milk plasma as a function of extent of the addition of heated milk to raw milk.DOI: http://dx.doi.org/10.3329/bjas.v43i2.20708 Bang. J. Anim. Sci. 2014. 43 (2): 123-127

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