THE DETERMINATION OF THE HOLDING TIME IN HIGH-TEMPERATURE, SHORT-TIME PASTEURIZING UNITS

Tryptic hydrolysis of whey protein isolate under specific incubation conditions including a relatively high enzyme:substrate (E:S) ratio of 1:10 is known to preferentially hydrolyse β-lactoglobulin (β-LG), while retaining the other major whey protein fraction, i.e., α-lactalbumin (α-LA) mainly intact. An objective of the present work was to explore the effects of reducing E:S (1:10, 1:30, 1:50, 1:100) on the selective hydrolysis of β-LG by trypsin at pH 8.5 and 25 °C in a 5% (w/v) WPI solution during incubation periods ranging from 1 to 7 h. In addition, the use of a pilot-scale continuous high-temperature, short-time (HTST) heat exchanger with an extended holding time (EHT) of 5 min as a means of inactivating trypsin to terminate hydrolysis was compared with laboratory-based acidification to <pH 3 by the addition of HCl, and batch sample heating in a water bath at 85 °C. An E:S of 1:10 resulted in 100% and 30% of β-LG and α-LA hydrolysis, respectively, after 3 h, while an E:S reduction to 1:30 and 1:50 led >90% β-LG hydrolysis after respective incubation periods of 4 and 6 h, with <5% hydrolysis of α-LA in the case of 1:50. Continuous HTST-EHT treatment was shown to be an effective inactivation process allowing for the maintenance of substrate selectivity. However, HTST-EHT heating resulted in protein aggregation, which negatively impacts the downstream recovery of intact α-LA. An optimum E:S was determined to be 1:50, with an incubation time ranging from 3 h to 7 h leading to 90% β-LG hydrolysis and minimal degradation of α-LA. Alternative batch heating by means of a water bath to inactivate trypsin caused considerable digestion of α-LA, while acidification to <pH 3.0 restricted subsequent functional applications of the protein.

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STUDIES ON THERMAL METHODS OF MEASURING THE HOLDING TIME IN HIGH-TEMPERATURE SHORT-TIME PASTEURIZERS

Journal of Milk and Food Technology ◽

10.4315/0022-2747-16.1.15 ◽

1953 ◽

Vol 16 (1) ◽

pp. 15-25 ◽

Cited By ~ 4

Author(s):

W. K. Jordan ◽

R. F. Holland

Keyword(s):

High Temperature ◽

Correction Factor ◽

Holding Time ◽

Thermal Waves ◽

Thermal Methods ◽

Thermal Test ◽

High Temperature Short Time ◽

The Difference ◽

Short Time

Data are presented on the properties of thermal waves produced by several means of suddenly increasing or decreasing the temperature of the fluid moving through the holding tube of a high-temperature short-time pasteurizer. Thermal holding-time measurements made with eight instruments or methods are compared with the holding time measured by the 3-A standard salt test. The reasons for variation in the correction factor, the difference beween the holding times measured by the salt test and a thermal test, are discussed.

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Effect of Commercial-Scale High-Temperature, Short-Time Pasteurization on the Viability of Mycobacterium paratuberculosis in Naturally Infected Cows' Milk

Applied and Environmental Microbiology ◽

10.1128/aem.68.2.602-607.2002 ◽

2002 ◽

Vol 68 (2) ◽

pp. 602-607 ◽

Cited By ~ 136

Author(s):

Irene R. Grant ◽

Edward I. Hitchings ◽

Alan McCartney ◽

Fiona Ferguson ◽

Michael T. Rowe

Keyword(s):

High Temperature ◽

Cetylpyridinium Chloride ◽

Raw Milk ◽

Holding Time ◽

Mycobacterium Paratuberculosis ◽

Pasteurized Milk ◽

Milk Samples ◽

Commercial Scale ◽

High Temperature Short Time ◽

Short Time

ABSTRACT Raw cows' milk naturally infected with Mycobacterium paratuberculosis was pasteurized with an APV HXP commercial-scale pasteurizer (capacity 2,000 liters/h) on 12 separate occasions. On each processing occasion, milk was subjected to four different pasteurization treatments, viz., 73Ã¯Â¿Â½C for 15 s or 25 s with and without prior homogenization (2,500 lb/in2 in two stages), in an APV Manton Gaulin KF6 homogenizer. Raw and pasteurized milk samples were tested for M. paratuberculosis by immunomagnetic separation (IMS)-PCR (to detect the presence of bacteria) and culture after decontamination with 0.75% (wt/vol) cetylpyridinium chloride for 5 h (to confirm bacterial viability). On 10 of the 12 processing occasions, M. paratuberculosis was detectable by IMS-PCR, culture, or both in either raw or pasteurized milk. Overall, viable M. paratuberculosis was cultured from 4 (6.7%) of 60 raw and 10 (6.9%) of 144 pasteurized milk samples. On one processing day, in particular, M. paratuberculosis appeared to have been present in greater abundance in the source raw milk (evidenced by more culture positives and stronger PCR signals), and on this occasion, surviving M. paratuberculosis bacteria were isolated from milk processed by all four heat treatments, i.e., 73Ã¯Â¿Â½C for 15 and 25 s with and without prior homogenization. On one other occasion, surviving M. paratuberculosis bacteria were isolated from an unhomogenized milk sample that had been heat treated at 73Ã¯Â¿Â½C for 25 s. Results suggested that homogenization increases the lethality of subsequent heat treatment to some extent with respect to M. paratuberculosis, but the extended 25-s holding time at 73Ã¯Â¿Â½C was found to be no more effective at killing M. paratuberculosis than the standard 15-s holding time. This study provides clear evidence that M. paratuberculosis bacteria in naturally infected milk are capable of surviving commercial high-temperature, short-time pasteurization if they are present in raw milk in sufficient numbers.

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The Control of the Holding Time in High Temperature-Short-Time Pasteurisation of Milk

Journal of the Royal Sanitary Institute ◽

10.1177/146642405307300102 ◽

1953 ◽

Vol 73 (1) ◽

pp. 11-18

Author(s):

J.G. Davis

Keyword(s):

High Temperature ◽

Holding Time ◽

High Temperature Short Time ◽

Short Time

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Differential impact of Holder and High Temperature Short Time pasteurization on the dynamic in vitro digestion of human milk in a preterm newborn model

Food Chemistry ◽

10.1016/j.foodchem.2020.127126 ◽

2020 ◽

Vol 328 ◽

pp. 127126 ◽

Cited By ~ 2

Author(s):

Stefano Nebbia ◽

Marzia Giribaldi ◽

Laura Cavallarin ◽

Enrico Bertino ◽

Alessandra Coscia ◽

...

Keyword(s):

High Temperature ◽

Human Milk ◽

In Vitro Digestion ◽

Preterm Newborn ◽

Differential Impact ◽

High Temperature Short Time ◽

Short Time

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High-Temperature Short-Time and Holder Pasteurization of Donor Milk: Impact on Milk Composition

Life ◽

10.3390/life11020114 ◽

2021 ◽

Vol 11 (2) ◽

pp. 114

Author(s):

Diana Escuder-Vieco ◽

Juan M. Rodríguez ◽

Irene Espinosa-Martos ◽

Nieves Corzo ◽

Antonia Montilla ◽

...

Keyword(s):

High Temperature ◽

Human Milk ◽

Milk Composition ◽

Donor Human Milk ◽

High Temperature Short Time ◽

Lactose Concentration ◽

C 30 ◽

Milk Banks ◽

Short Time

Holder pasteurization (HoP; 62.5 °C, 30 min) is commonly used to ensure the microbiological safety of donor human milk (DHM) but diminishes its nutritional properties. A high-temperature short-time (HTST) system was designed as an alternative for human milk banks. The objective of this study was to evaluate the effect of this HTST system on different nutrients and the bile salt stimulated lipase (BSSL) activity of DHM. DHM was processed in the HTST system and by standard HoP. Macronutrients were measured with a mid-infrared analyzer. Lactose, glucose, myo-inositol, vitamins and lipids were assayed using chromatographic techniques. BSSL activity was determined using a kit. The duration of HTST treatment had a greater influence on the nutrient composition of DHM than did the tested temperature. The lactose concentration and the percentage of phospholipids and PUFAs were higher in HTST-treated than in raw DHM, while the fat concentration and the percentage of monoacylglycerides and SFAs were lower. Other nutrients did not change after HTST processing. The retained BSSL activity was higher after short HTST treatment than that following HoP. Overall, HTST treatment resulted in better preservation of the nutritional quality of DHM than HoP because relevant thermosensitive components (phospholipids, PUFAs, and BSSL) were less affected.

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Influence of Guar Gum on the Thermal Stability of Listeria innocua, Listeria monocytogenes, and γ-Glutamyl Transpeptidase during High-Temperature Short-Time Pasteurization of Bovine Milk

Journal of Food Protection ◽

10.4315/0362-028x-62.8.861 ◽

1999 ◽

Vol 62 (8) ◽

pp. 861-866 ◽

Cited By ~ 12

Author(s):

PUNIDADAS PIYASENA ◽

ROBIN C. McKELLAR

Keyword(s):

High Temperature ◽

Laminar Flow ◽

Protective Effect ◽

Guar Gum ◽

Listeria Innocua ◽

Water Mixture ◽

High Temperature Short Time ◽

Whole Milk ◽

Short Time ◽

Glutamyl Transpeptidase

Mathematical models describing the thermal inactivation of γ-glutamyl transpeptidase (TP) and Listeria innocua in milk during high-temperature short-time (HTST) pasteurization were validated with data from TP, L. innocua, and L. monocytogenes trials in guar gum–milk. Holding tube times were determined for turbulent flow using water, and for laminar flow using a guar gum (0.27% wt/wt)–sucrose (5.3% wt/wt)–water mixture. Inactivation of TP and L. innocua was lower in a solution of guar gum (0.25% wt/wt) in whole milk than was predicted by models derived from studies with whole milk alone. Use of laminar flow timings improved model fit but did not completely account for the observed protective effect. L. monocytogenes survival was close to that predicted by the L. innocua model, although some protection was afforded this pathogen under laminar flow. Considerable intertrial variability was noted for L. monocytogenes. Risk analysis simulations using @RISK, a Lotus 1-2–3W add-in, were used to account for intertrial variability. Simulated log10 %reductions consistently underpredicted experimental L. monocytogenes survival (fail-safe), thus the L. innocua model derived in milk is suitable for estimating L. monocytogenes survival in viscous products. Increased thermal tolerance during laminar flow may be attributed to the protective effect of stabilizer.

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