Effects of homogenisation pressures on physicochemical changes in different layers of ultra-high temperature whole milk during storage

2013 ◽  
Vol 66 (3) ◽  
pp. 325-332 ◽  
Author(s):  
Chun Lu ◽  
Guorong Wang ◽  
Yan Li ◽  
Liebing Zhang
Keyword(s):  
High Temperature ◽  
Physicochemical Changes ◽  
Whole Milk ◽  
Ultra High Temperature

A modified ultra high temperature treatment for reducing microbial lipolysis in stored milk

1987 ◽  
Vol 54 (2) ◽  
pp. 275-282 ◽  
Author(s):  
Anthony R. Bucky ◽  
Patrick R. Hayes ◽  
David S. Robinson
Keyword(s):  
Heat Treatment ◽  
Fatty Acids ◽  
High Temperature ◽  
Free Fatty Acids ◽  
Storage Period ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Viable Cells ◽  
Whole Milk ◽  
Ultra High Temperature

SummaryCultures ofPseudomonasP46 grown in whole milk to contain ∼ 2 × 107or 1 × 108viable cells ml−1before ultra high temperature (UHT) treatment (140°C for 5 s) demonstrated near linear increases in the concentration of short-chain free fatty acids (FFA) during storage at 20°C. However with 5 × 106cells ml−1before UHT heat treatment there was no detectable increase in these FFA levels over a 6-month storage period. A novel heat treatment (140°C for 5 s followed by 60°C for 5 min) reduced the rate of production of volatile FFA to < 10% of the rates achieved after the normal UHT treatment.

Enhanced inactivation of bacterial lipases and proteinases in whole milk by a modified ultra high temperature treatment

1988 ◽  
Vol 55 (3) ◽  
pp. 373-380 ◽  
Author(s):  
Anthony R. Bucky ◽  
Patrick R. Hayes ◽  
David S. Robinson
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Raw Milk ◽  
Temperature Treatment ◽  
Heat Treatments ◽  
High Temperature Treatment ◽  
Amino Groups ◽  
Whole Milk ◽  
Viable Bacteria ◽  
Ultra High Temperature

SummaryCultures ofPseudomonasspp. strains P10, P12 and P15 grown in whole milk which contained ∼ 1 × 108viable bacteria ml−1demonstrated near linear increases in the concentration of short-chain free fatty acids and trichloroacetic acid soluble free amino groups at 20 °C, following either ultra high temperature (UHT) treatment (140 °C for 5 s) or dual heat treatments (140 °C followed by either 57, 60 or 65 °C). The dual heat treatments reduced the rates of lipolysis and proteolysis compared to the UHT treatment by up to 25-fold. The dual heat treatment utilizing 60 °C for 5 min also effectively limited both lipase and proteinase activities in raw milk culture samples which had contained either 6 × 106, 5 × 107or 1 × 108viable bacteria ml−1. In this system enzyme activities were reduced by up to 10-fold following dual heat treatment compared to UHT treatment alone.

The effect of oxygen content on flavour and chemical changes during aseptic storage of whole milk after ultra-high-temperature processing

1975 ◽  
Vol 42 (2) ◽  
pp. 285-295 ◽  
Author(s):  
E. L. Thomas ◽  
H. Burton ◽  
J. E. Ford ◽  
A. G. Perkin
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Vitamin B ◽  
Storage Losses ◽  
Whole Milk ◽  
Short Period ◽  
High Temperature Processing ◽  
Nutritional Effects ◽  
Effect Of Oxygen ◽  
Ultra High Temperature

SummaryIndirectly heated ultra-high-temperature (UHT) processed milk was prepared with initially high, medium, and low dissolved O2 contents of 8·9, 3·6 and 1·0 ppm respectively, aseptically bottled, and tested at intervals during storage at room temperature for 150 d. Flavour acceptability increased to a maximum after a few days, but declined slowly after about 6 d; the increase was associated with less off-flavour described as ‘cabbagey’, and the decrease with more ‘stale’ off-flavour descriptions. Milks with higher initial O2 contents were preferred up to 8–13 d, but thereafter acceptability was independent of initial O2 content. Sulphydryl group (–SH) contents rapidly decreased and O2 levels correspondingly declined in the first few days as the flavour improved. Loss of –SH was lower with lower initial O2 contents, and moderate –SH content remained in low O2 samples for several weeks. Ferricyanide reducing (FR) values did not satisfactorily measure stale flavour development. They were initially high and decreased during the first 13 d at rates dependent on O2 content. After 20 d the FR values began to rise in high O2 samples, but continued to decline slowly in low O2 samples up to 90d although stale flavour was increasing.High initial O2 contents resulted in rapid depletion of ascorbic acid and folic acid during storage. Losses of vitamin B12 were small, but were higher with high O2 contents than with low.The beneficial effect of O2 on flavour, therefore, appears to be so slight and confined to such a short period in the early life of the milk as to be completely outweighed by the adverse nutritional effects.

Changes occurring in stabilized ultra-high-temperature-treated whole milk during storage

2018 ◽  
Vol 85 (4) ◽  
pp. 449-452
Author(s):  
Fernando César dos Santos ◽  
Fabiano Érisson da Cunha ◽  
Érika de Pádua Alves ◽  
Flávia de Almeida Bergonse Pereira ◽  
Elsa Helena Walter de Santana ◽  
...  
Keyword(s):  
High Temperature ◽  
Shelf Life ◽  
Microbiological Quality ◽  
Storage Period ◽  
Raw Milk ◽  
Processing Plant ◽  
Uht Milk ◽  
Cell Counts ◽  
Whole Milk ◽  
Ultra High Temperature

This Research Communication describes the relationship between casein, free fatty acids (FFAs) and the storage period of ultra-high temperature-treated (UHT) whole milk observed for a period of 120 d of labelled shelf-life. Moreover, we aim to estimate the daily rate of casein degradation in UHT whole milk, and the total length of time estimated for its full degradation. With this aim, ten sets of samples were evaluated from batches of UHT milk manufactured by a dairy processing plant in Parana State, Brazil on 10 different days. Each set was comprised of one liter of raw milk and 12 units of 1 litre cartons of UHT milk, and represented one batch of production. Total mesophilic (TMC), psychrotrophic (TPC), and somatic cell counts (SCC) of raw milk were assessed. UHT milk was assessed for fat (%), sialic acid (mg/l), casein (%), and FFA contents. TMC ranged from 3·5 × 106 to 3·1 × 107 CFU/ml; TPC, from 106 UFC/ml and higher; and SCC, from 18 × 104 SC/ml to 4·83 × 105 CS/ml. Casein (r = −0·991; R2 = 0·9822) and FFA (r = 0·962; R2 = 0·9245) contents, and storage time of UHT milk were correlated (P < 0·05). The rate of casein hydrolysis was estimated as 0·021 g/100 g UHT whole milk/day. A complete breakdown of casein was estimated to occur by the 560th day post-manufacture. Although age gelation was not observed in our study, the report herein corroborates the understanding that the microbiological quality and SCC of raw milk are important components involving the integrity of casein and lipids of UHT milk during shelf-life.

Comparison of milks processed by the direct and indirect methods of ultra-high-temperature sterilization. II. The sporicidal efficiency of an experimental plant for direct and indirect processing

1970 ◽  
Vol 37 (2) ◽  
pp. 219-226 ◽  
Author(s):  
J. G. Franklin ◽  
H. M. Underwood ◽  
A. G. Perkin ◽  
H. Burton
Keyword(s):  
High Temperature ◽  
Bacillus Stearothermophilus ◽  
Inhibitory Effect ◽  
Processing Temperature ◽  
Experimental Plant ◽  
Indirect Methods ◽  
Large Numbers ◽  
Whole Milk ◽  
Direct And Indirect Methods ◽  
Ultra High Temperature

SummaryThe variation of sporicidal efficiency with processing temperature was determined for an experimental ultra-high-temperature (UHT) milk sterilizer operating alternatively as an indirect or as a direct heater. Whole milk was inoculated with large numbers of spores of Bacillus subtilis 786 and Bacillus stearothermophilus TH24, and the proportion of spores surviving the sterilizing process was calculated from dilution and colony counts on the untreated and treated milk. The results for B. subtilis spores were unreliable, and the dilution count results for B. stearothermophilus spores were influenced by the inhibitory effect of the UHT processed milk. The results for the colony counts of B. stearothermophilus spores were preferred as a basis for the comparison of the direct and indirect processes. Over the range of processing temperatures 137–145 °C it was found that the sterilizing temperature had to be 3–4 degC higher with direct heating than with indirect heating to give equal spore destructions.

Fouling of a plate heat exchanger used in ultra-high-temperature sterilization of milk

1984 ◽  
Vol 51 (4) ◽  
pp. 557-568 ◽  
Author(s):  
Marc Lalande ◽  
Jean-Pierre Tissier ◽  
Georges Corrieu
Keyword(s):  
High Temperature ◽  
Heating Temperature ◽  
Raw Milk ◽  
Mineral Contents ◽  
Heating And Cooling ◽  
Heating Section ◽  
Whole Milk ◽  
Mechanisms Of Formation ◽  
Comparison Of The Results ◽  
Ultra High Temperature

SummaryThe composition and weight of deposit formed in all sections of an ultra-high-temperature milk sterilization plant were determined. Deposits formed in the preheating, heating and cooling sections during sterilization of pasteurized whole milk were analysed for dry matter, protein, fat and mineral contents. The weight and composition of components of the deposit varied in different sections of the plant and with the heating temperature. Two categories of deposit could be distinguished: one in the preheating section consisting of (w/w) protein 50%, minerals 40% and fat 1% and another in the heating section consisting of minerals 75%, proteins 15% and fat 3%. Concerning the rate of formation of these deposits, a comparison of the results with those obtained for pasteurization shows that fouling was more rapid during pasteurization of raw milk than during sterilization of previously pasteurized milk. Hypotheses concerning mechanisms of formation of protein deposition are discussed.

Effect of pH on the formation of deposit from milk on heated surfaces during ultra high temperature processing

1986 ◽  
Vol 53 (1) ◽  
pp. 75-87 ◽  
Author(s):  
Paul J. Skudder ◽  
Brian E. Brooker ◽  
Andrew D. Bonsey ◽  
Norman R. Alvarez-Guerrero
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Skim Milk ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
High Concentration ◽  
Deposit Formation ◽  
Effect Of Ph ◽  
Whole Milk ◽  
Ultra High Temperature

SUMMARYInvestigation of the effect of pH on the formation of deposit from milk during ultra high temperature treatment using a plate-type plant showed that deposit formation was greatly increased when the pH of whole milk was reduced to 6·54, irrespective of whether the adjustment was made through the addition of HCl or lactic acid. Most of the increase in deposition took place in the higher temperature sections of the plant. Conversely, an increase in milk pH to 6·8 using NaOH resulted in considerably less deposit being formed during heat treatment. Reducing the pH of whole milk increased the deposition of both protein and fat, but reduced the deposition of minerals. Despite very high concentration of fat in the deposits, it is unlikely that fatper sewas responsible for increased deposit formation. Deposition also increased when the pH of skim milk was reduced to 6·51 before processing. Electron micrographs of the milks after heat treatment indicated that pH reductions caused the formation of large aggregates containing casein micelles during heating. Fat globules were also present in aggregates formed in whole milk with reduced pH. Slight reductions in the pH of milk before processing appear to enable the pH during heat treatment to fall below a critical value at which coagulation of milk takes place at the heated surfaces.

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