The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform
David J. Armstrong - One of the best experts on this subject based on the ideXlab platform.
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Modeling, monitoring and control strategies for high temperature short time Pasteurization systems — 1. Empirical model development
Food Control, 1998Co-Authors: Antoine Negiz, Joseph E. Schlesser, Ali Cinar, P. Ramanauskas, David J. ArmstrongAbstract:Abstract Dynamic models of high temperature short time (HTST) Pasteurization systems can be developed by using empirical model development paradigms such as transfer functions and times series models. Properly designed experiments that excite all output variables provide good data that enable the development of accurate dynamic models. These models are used in feedback control and statistical process monitoring system design. The methodology for time series model development for HTST Pasteurization processes is illustrated by using data collected from a pilot scale HTST Pasteurization system.
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Modeling, monitoring and control strategies for high temperature short time Pasteurization systems — 2. Lethality-based control
Food Control, 1998Co-Authors: Antoine Negiz, Joseph E. Schlesser, Ali Cinar, P. Ramanauskas, David J. ArmstrongAbstract:Abstract A lethality-based control system was designed to provide accurate control of a high temperature short time (HTST) pasteurizer and to process milk products with a lethality equivalent of 161 °F (71.67 °C) or above for 15 s. This control system provides significant flexibility in operating the process and optimizing functional properties of the food components. Multivariable control of an HTST pasteurizer is implemented by using product total lethality to determine the controller set-points. The equation that relates the temperature and flow rate combinations to the product total lethality, 161 °F (71.67 °C), 15 s, was modified to permit overprocessing levels specified by plant personnel. By using this equation and the set-point value selected for the other variable, set-point values for the temperature or the flow rate controller were computed. The flow and temperature controllers are integrated into a real-time monitoring and control system. The monitoring and control system includes the multivariable controller, the lethality rate calculation module, statistical monitoring of the total lethality, product flow rate, hot water outlet temperature, and holding tube exit temperature measurements, and the display screens for visual inspection of the monitoring tools. This study attempted to achieve compliance of the HTST process operation with the recommended Pasteurized Milk Ordinance by providing a margin between the alarm limits of the monitoring chart and the safety limits.
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Acquisition, Storage, and Review of Safety Data from a Commercial System for High Temperature, Short Time Pasteurization
Journal of dairy science, 1998Co-Authors: Joseph E. Schlesser, David J. Armstrong, Ali Cinar, P. Ramanauskas, G. Lynn, A. NegizAbstract:A high temperature, short time (HTST) Pasteurization system was equipped with electronic sensors to determine the temperature, pressure, flow rate, and position of the flow diversion valve. A computer for data acquisition was wired to the sensors to monitor and to record processing conditions related to public health. The processing conditions were stored in safety files on the hard drive of the computer, transferred weekly to a tape drive, and stored. The processing conditions of the HTST system were monitored for 270 d to determine the accuracy and reliability of the data acquisition system. The size of the HTST safety files ranged from 6.2 to 9.1 MB when the sensors were monitored every second. The file size was reduced to < 1.8 MB when the monitoring frequency was increased to every 5 s. To determine accuracy, the temperatures recorded by the data acquisition system were compared with the temperatures recorded by an electronic recorder controller. To determine reliability, changes in the position of the flow diversion valve were examined to identify process deviations and were compared with the event marker on circular charts. The review of the data file by the actual time method was an effective alternative to the electronic recorder controller for monitoring the completeness of data in the safety files. Off-line review to determine reliability required approximately 10 min/d of records.
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Modeling, monitoring and control strategies for high temperature short time Pasteurization systems — 3. Statistical monitoring of product lethality and process sensor reliability
Food Control, 1998Co-Authors: Antoine Negiz, Joseph E. Schlesser, Ali Cinar, P. Ramanauskas, David J. ArmstrongAbstract:Abstract Statistical process monitoring (SPM) is used in food processing industries to improve productivity and product quality. SPM can also provide information to operators on how close a process is to non-compliance to product safety limits, and carry out periodic checks of sensor accuracy at high frequency. Traditional SPM tools such as Shewhart charts are not appropriate for continuous food processes because of autocorrelation in data. Four alternative SPM techniques are presented and applied to high temperature short time (HTST) dairy Pasteurization. The study attempted to achieve compliance of the HTST process operation with the recommended Pasteurized Milk Ordinance by providing a margin between the alarm limits of the monitoring chart and the safety limits. Monitoring of residuals and parameter change detection techniques are used for monitoring processes with autocorrelated variables. Hotelling's T2 and residuals of canonical variates techniques are used for monitoring multivariable processes.
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Automated Control and Monitoring of Thermal Processing Using High Temperature, Short Time Pasteurization
Journal of dairy science, 1997Co-Authors: Joseph E. Schlesser, David J. Armstrong, Ali Cinar, P. Ramanauskas, A. NegizAbstract:Abstract High temperature, short time Pasteurization was used to evaluate a computer-based system for controlling the Pasteurization process, acquiring data, and monitoring records. Software was used for the control of hot water temperature, flow rate through the centrifugal timing pump, and diversion of underprocessed product. Three types of control strategies were conducted: single loop, cascade, and multivariable. The single loop control strategy showed the most rapid responses to temperature changes, but the temperature response curve was slowest to return to its set point. The cascade control strategy showed slower recoveries to temperature changes, but the temperature response curve was smoother. The multivariable control strategy responded slightly faster than the cascade control strategy, and the temperature response curve was slightly smoother than the cascade control strategy. The multivariable control strategy was able to control the flow diversion valve by the use of a lethality controller. The data acquisition system, used to monitor the data obtained from the high temperature, Short-Time Pasteurization system, was within ±0.1°C of the temperature recorded by the safety thermal limit recorder. Reliability was determined by examining the changes in the position of the flow diversion valve to identify process deviations and by comparing the changes to the event marker on circular charts. The data acquisition system was an effective alternative for monitoring the completeness of data.
M A Drake - One of the best experts on this subject based on the ideXlab platform.
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use of acid whey protein concentrate as an ingredient in nonfat cup set style yogurt
Journal of Dairy Science, 2019Co-Authors: Bryan Wherry, D M Barbano, M A DrakeAbstract:Acid whey resulting from the production of soft cheeses is a disposal problem for the dairy industry. Few uses have been found for acid whey because of its high ash content, low pH, and high organic acid content. The objective of this study was to explore the potential of recovery of whey protein from cottage cheese acid whey for use in yogurt. Cottage cheese acid whey and Cheddar cheese whey were produced from standard cottage cheese and Cheddar cheese-making procedures, respectively. The whey was separated and pasteurized by high temperature, short time Pasteurization and stored at 4°C. Food-grade ammonium hydroxide was used to neutralize the acid whey to a pH of 6.4. The whey was heated to 50°C and concentrated using ultrafiltration and diafiltration with 11 polyethersulfone cartridge membrane filters (10,000-kDa cutoff) to 25% total solids and 80% protein. Skim milk was concentrated to 6% total protein. Nonfat, unflavored set-style yogurts (6.0 ± 0.1% protein, 15 ± 1.0% solids) were made from skim milk with added acid whey protein concentrate, skim milk with added sweet whey protein concentrate, or skim milk concentrate. Yogurt mixes were standardized to lactose and fat of 6.50% and 0.10%, respectively. Yogurt was fermented at 43°C to pH 4.6 and stored at 4°C. The experiment was replicated in triplicate. Titratable acidity, pH, whey separation, color, and gel strength were measured weekly in yogurts through 8 wk. Trained panel profiling was conducted on 0, 14, 28, and 56 d. Fat-free yogurts produced with added neutralized fresh liquid acid whey protein concentrate had flavor attributes similar those with added fresh liquid sweet whey protein but had lower gel strength attributes, which translated to differences in trained panel texture attributes and lower consumer liking scores for fat-free yogurt made with added acid whey protein ingredient. Difference in pH was the main contributor to texture differences, as higher pH in acid whey protein yogurts changed gel structure formation and water-holding capacity of the yogurt gel. In a second part of the study, the yogurt mix was reformulated to address texture differences. The reformulated yogurt mix at 2% milkfat and using a lower level of sweet and acid whey ingredient performed at parity with control yogurts in consumer sensory trials. Fresh liquid acid whey protein concentrates from cottage cheese manufacture can be used as a liquid protein ingredient source for manufacture of yogurt in the same factory.
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flavor and flavor chemistry differences among milks processed by high temperature short time Pasteurization or ultra Pasteurization
Journal of Dairy Science, 2018Co-Authors: D M Enois, D M Arbano, M A DrakeAbstract:ABSTRACT Typical High-Temperature, Short-Time (HTST) Pasteurization encompasses a lower heat treatment and shorter refrigerated shelf life compared with ultra-Pasteurization (UP) achieved by direct steam injection (DSI-UP) or indirect heat (IND-UP). A greater understanding of the effect of different heat treatments on flavor and flavor chemistry of milk is required to characterize, understand, and identify the sources of flavors. The objective of this study was to determine the differences in the flavor and volatile compound profiles of milk subjected to HTST, DSI-UP, or IND-UP using sensory and instrumental techniques. Raw skim and raw standardized 2% fat milks (50 L each) were processed in triplicate and pasteurized at 78°C for 15 s (HTST) or 140°C for 2.3 s by DSI-UP or IND-UP. Milks were cooled and stored at 4°C, then analyzed at d 0, 3, 7, and 14. Sensory attributes were determined using a trained panel, and aroma active compounds were evaluated by solid-phase micro-extraction or stir bar sorptive extraction followed by gas chromatography-mass spectrometry, gas chromatography-olfactometry, and gas chromatography-triple quad mass spectrometry. The UP milks had distinct cooked and sulfur flavors compared with HTST milks. The HTST milks had less diversity in aroma active compounds compared with UP milks. Flavor intensity of all milks decreased by d 14 of storage. Aroma active compound profiles were affected by heat treatment and storage time in both skim and 2% milk. High-impact aroma active compounds were hydrogen sulfide, dimethyl trisulfide, and methional in DSI-UP and 2 and 3-methylbutanal, furfural, 2-heptanone, 2-acetyl-1-pyrroline, 2-aminoacetophenone, benzaldehyde, and dimethyl sulfide in IND-UP. These results provide a foundation knowledge of the effect of heat treatments on flavor development and differences in sensory quality of UP milks.
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effects of fat content Pasteurization method homogenization pressure and storage time on the mechanical and sensory properties of bovine milk
Journal of Dairy Science, 2018Co-Authors: Helen S Joyner, B G Carter, M A DrakeAbstract:Fluid milk may be pasteurized by High-Temperature Short-Time Pasteurization (HTST) or ultraPasteurization (UP). Literature suggests that UP increases milk astringency, but definitive studies have not demonstrated this effect. Thus, the objective of this study was to determine the effects of Pasteurization method, fat content, homogenization pressure, and storage time on milk sensory and mechanical behaviors. Raw skim (<0.2% fat), 2%, and 5% fat milk was pasteurized in duplicate by indirect UP (140°C, 2.3 s) or by HTST Pasteurization (78°C, 15 s), homogenized at 20.7 MPa, and stored at 4°C for 8 wk. Additionally, 2% fat milk was processed by indirect UP and homogenized at 13.8, 20.7, and 27.6 MPa and stored at 4°C for 8 wk. Sensory profiling, instrumental viscosity, and friction profiles of all milk were evaluated at 25°C after storage times of 1, 4, and 8 wk. Sodium dodecyl sulfate PAGE and confocal laser scanning microscopy were used to determine protein structural changes in milk at these time points. Fresh HTST milk was processed at wk 7 for wk 8 evaluations. UltraPasteurization increased milk sensory and instrumental viscosity compared with HTST Pasteurization. Increased fat content increased sensory and instrumental viscosity, and decreased astringency and friction profiles. Astringency, mixed regimen friction profiles, and sensory viscosity also increased for UP versus HTST. Increased storage time showed no effect on sensory viscosity or mechanical viscosity. However, increased storage time generally resulted in increased friction profiles and astringency. Sodium dodecyl sulfate PAGE and confocal laser scanning microscopy showed increased denatured whey protein in UP milk compared with HTST milk. The aggregates or network formed by these proteins and casein micelles likely caused the increase in viscosity and friction profiles during storage. Homogenization pressure did not significantly affect friction behaviors, mechanical viscosity, or astringency; however, samples homogenized at 13.8 MPa versus 20.7 and 27.6 MPa showed higher sensory viscosity. Astringency was positively correlated with the friction coefficient at 100 m/s sliding speed (R2 = 0.71 for HTST milk and R2 = 0.74 for UP milk), and sensory viscosity was positively correlated with the mechanical viscosity at a shear rate of 50 s-1 (R2 = 0.90). Thus, instrumental testing can be used to indicate certain sensory behaviors of milk.
Joseph E. Schlesser - One of the best experts on this subject based on the ideXlab platform.
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Modeling, monitoring and control strategies for high temperature short time Pasteurization systems — 1. Empirical model development
Food Control, 1998Co-Authors: Antoine Negiz, Joseph E. Schlesser, Ali Cinar, P. Ramanauskas, David J. ArmstrongAbstract:Abstract Dynamic models of high temperature short time (HTST) Pasteurization systems can be developed by using empirical model development paradigms such as transfer functions and times series models. Properly designed experiments that excite all output variables provide good data that enable the development of accurate dynamic models. These models are used in feedback control and statistical process monitoring system design. The methodology for time series model development for HTST Pasteurization processes is illustrated by using data collected from a pilot scale HTST Pasteurization system.
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Modeling, monitoring and control strategies for high temperature short time Pasteurization systems — 2. Lethality-based control
Food Control, 1998Co-Authors: Antoine Negiz, Joseph E. Schlesser, Ali Cinar, P. Ramanauskas, David J. ArmstrongAbstract:Abstract A lethality-based control system was designed to provide accurate control of a high temperature short time (HTST) pasteurizer and to process milk products with a lethality equivalent of 161 °F (71.67 °C) or above for 15 s. This control system provides significant flexibility in operating the process and optimizing functional properties of the food components. Multivariable control of an HTST pasteurizer is implemented by using product total lethality to determine the controller set-points. The equation that relates the temperature and flow rate combinations to the product total lethality, 161 °F (71.67 °C), 15 s, was modified to permit overprocessing levels specified by plant personnel. By using this equation and the set-point value selected for the other variable, set-point values for the temperature or the flow rate controller were computed. The flow and temperature controllers are integrated into a real-time monitoring and control system. The monitoring and control system includes the multivariable controller, the lethality rate calculation module, statistical monitoring of the total lethality, product flow rate, hot water outlet temperature, and holding tube exit temperature measurements, and the display screens for visual inspection of the monitoring tools. This study attempted to achieve compliance of the HTST process operation with the recommended Pasteurized Milk Ordinance by providing a margin between the alarm limits of the monitoring chart and the safety limits.
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Acquisition, Storage, and Review of Safety Data from a Commercial System for High Temperature, Short Time Pasteurization
Journal of dairy science, 1998Co-Authors: Joseph E. Schlesser, David J. Armstrong, Ali Cinar, P. Ramanauskas, G. Lynn, A. NegizAbstract:A high temperature, short time (HTST) Pasteurization system was equipped with electronic sensors to determine the temperature, pressure, flow rate, and position of the flow diversion valve. A computer for data acquisition was wired to the sensors to monitor and to record processing conditions related to public health. The processing conditions were stored in safety files on the hard drive of the computer, transferred weekly to a tape drive, and stored. The processing conditions of the HTST system were monitored for 270 d to determine the accuracy and reliability of the data acquisition system. The size of the HTST safety files ranged from 6.2 to 9.1 MB when the sensors were monitored every second. The file size was reduced to < 1.8 MB when the monitoring frequency was increased to every 5 s. To determine accuracy, the temperatures recorded by the data acquisition system were compared with the temperatures recorded by an electronic recorder controller. To determine reliability, changes in the position of the flow diversion valve were examined to identify process deviations and were compared with the event marker on circular charts. The review of the data file by the actual time method was an effective alternative to the electronic recorder controller for monitoring the completeness of data in the safety files. Off-line review to determine reliability required approximately 10 min/d of records.
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Modeling, monitoring and control strategies for high temperature short time Pasteurization systems — 3. Statistical monitoring of product lethality and process sensor reliability
Food Control, 1998Co-Authors: Antoine Negiz, Joseph E. Schlesser, Ali Cinar, P. Ramanauskas, David J. ArmstrongAbstract:Abstract Statistical process monitoring (SPM) is used in food processing industries to improve productivity and product quality. SPM can also provide information to operators on how close a process is to non-compliance to product safety limits, and carry out periodic checks of sensor accuracy at high frequency. Traditional SPM tools such as Shewhart charts are not appropriate for continuous food processes because of autocorrelation in data. Four alternative SPM techniques are presented and applied to high temperature short time (HTST) dairy Pasteurization. The study attempted to achieve compliance of the HTST process operation with the recommended Pasteurized Milk Ordinance by providing a margin between the alarm limits of the monitoring chart and the safety limits. Monitoring of residuals and parameter change detection techniques are used for monitoring processes with autocorrelated variables. Hotelling's T2 and residuals of canonical variates techniques are used for monitoring multivariable processes.
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Automated Control and Monitoring of Thermal Processing Using High Temperature, Short Time Pasteurization
Journal of dairy science, 1997Co-Authors: Joseph E. Schlesser, David J. Armstrong, Ali Cinar, P. Ramanauskas, A. NegizAbstract:Abstract High temperature, short time Pasteurization was used to evaluate a computer-based system for controlling the Pasteurization process, acquiring data, and monitoring records. Software was used for the control of hot water temperature, flow rate through the centrifugal timing pump, and diversion of underprocessed product. Three types of control strategies were conducted: single loop, cascade, and multivariable. The single loop control strategy showed the most rapid responses to temperature changes, but the temperature response curve was slowest to return to its set point. The cascade control strategy showed slower recoveries to temperature changes, but the temperature response curve was smoother. The multivariable control strategy responded slightly faster than the cascade control strategy, and the temperature response curve was slightly smoother than the cascade control strategy. The multivariable control strategy was able to control the flow diversion valve by the use of a lethality controller. The data acquisition system, used to monitor the data obtained from the high temperature, Short-Time Pasteurization system, was within ±0.1°C of the temperature recorded by the safety thermal limit recorder. Reliability was determined by examining the changes in the position of the flow diversion valve to identify process deviations and by comparing the changes to the event marker on circular charts. The data acquisition system was an effective alternative for monitoring the completeness of data.
David A. Mills - One of the best experts on this subject based on the ideXlab platform.
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Reservoirs of antimicrobial resistance genes in retail raw milk.
Microbiome, 2020Co-Authors: Jinxin Liu, Yuanting Zhu, Michele T. Jay-russell, Danielle G. Lemay, David A. MillsAbstract:It has been estimated that at least 3% of the USA population consumes unpasteurized (raw) milk from animal sources, and the demand to legalize raw milk sales continues to increase. However, consumption of raw milk can cause foodborne illness and be a source of bacteria containing transferrable antimicrobial resistance genes (ARGs). To obtain a comprehensive understanding of the microbiome and antibiotic resistome in both raw and processed milk, we systematically analyzed 2034 retail milk samples including unpasteurized milk and pasteurized milk via vat Pasteurization, High-Temperature-Short-Time Pasteurization, and ultra-Pasteurization from the United States using complementary culture-based, 16S rRNA gene, and metagenomic sequencing techniques. Raw milk samples had the highest prevalence of viable bacteria which were measured as all aerobic bacteria, coliform, and Escherichia coli counts, and their microbiota was distinct from other types of milk. 16S rRNA gene sequencing revealed that Pseudomonadaceae dominated raw milk with limited levels of lactic acid bacteria. Among all milk samples, the microbiota remained stable with constant bacterial populations when stored at 4 °C. In contrast, storage at room temperature dramatically enriched the bacterial populations present in raw milk samples and, in parallel, significantly increased the richness and abundance of ARGs. Metagenomic sequencing indicated raw milk possessed dramatically more ARGs than pasteurized milk, and a conjugation assay documented the active transfer of blaCMY-2, one ceftazidime resistance gene present in raw milk-borne E. coli, across bacterial species. The room temperature-enriched resistome differed in raw milk from distinct geographic locations, a difference likely associated with regionally distinct milk microbiota. Despite advertised “probiotic” effects, our results indicate that raw milk microbiota has minimal lactic acid bacteria. In addition, retail raw milk serves as a reservoir of ARGs, populations of which are readily amplified by spontaneous fermentation. There is an increased need to understand potential food safety risks from improper transportation and storage of raw milk with regard to ARGs.
P. Ramanauskas - One of the best experts on this subject based on the ideXlab platform.
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Modeling, monitoring and control strategies for high temperature short time Pasteurization systems — 1. Empirical model development
Food Control, 1998Co-Authors: Antoine Negiz, Joseph E. Schlesser, Ali Cinar, P. Ramanauskas, David J. ArmstrongAbstract:Abstract Dynamic models of high temperature short time (HTST) Pasteurization systems can be developed by using empirical model development paradigms such as transfer functions and times series models. Properly designed experiments that excite all output variables provide good data that enable the development of accurate dynamic models. These models are used in feedback control and statistical process monitoring system design. The methodology for time series model development for HTST Pasteurization processes is illustrated by using data collected from a pilot scale HTST Pasteurization system.
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Modeling, monitoring and control strategies for high temperature short time Pasteurization systems — 2. Lethality-based control
Food Control, 1998Co-Authors: Antoine Negiz, Joseph E. Schlesser, Ali Cinar, P. Ramanauskas, David J. ArmstrongAbstract:Abstract A lethality-based control system was designed to provide accurate control of a high temperature short time (HTST) pasteurizer and to process milk products with a lethality equivalent of 161 °F (71.67 °C) or above for 15 s. This control system provides significant flexibility in operating the process and optimizing functional properties of the food components. Multivariable control of an HTST pasteurizer is implemented by using product total lethality to determine the controller set-points. The equation that relates the temperature and flow rate combinations to the product total lethality, 161 °F (71.67 °C), 15 s, was modified to permit overprocessing levels specified by plant personnel. By using this equation and the set-point value selected for the other variable, set-point values for the temperature or the flow rate controller were computed. The flow and temperature controllers are integrated into a real-time monitoring and control system. The monitoring and control system includes the multivariable controller, the lethality rate calculation module, statistical monitoring of the total lethality, product flow rate, hot water outlet temperature, and holding tube exit temperature measurements, and the display screens for visual inspection of the monitoring tools. This study attempted to achieve compliance of the HTST process operation with the recommended Pasteurized Milk Ordinance by providing a margin between the alarm limits of the monitoring chart and the safety limits.
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Acquisition, Storage, and Review of Safety Data from a Commercial System for High Temperature, Short Time Pasteurization
Journal of dairy science, 1998Co-Authors: Joseph E. Schlesser, David J. Armstrong, Ali Cinar, P. Ramanauskas, G. Lynn, A. NegizAbstract:A high temperature, short time (HTST) Pasteurization system was equipped with electronic sensors to determine the temperature, pressure, flow rate, and position of the flow diversion valve. A computer for data acquisition was wired to the sensors to monitor and to record processing conditions related to public health. The processing conditions were stored in safety files on the hard drive of the computer, transferred weekly to a tape drive, and stored. The processing conditions of the HTST system were monitored for 270 d to determine the accuracy and reliability of the data acquisition system. The size of the HTST safety files ranged from 6.2 to 9.1 MB when the sensors were monitored every second. The file size was reduced to < 1.8 MB when the monitoring frequency was increased to every 5 s. To determine accuracy, the temperatures recorded by the data acquisition system were compared with the temperatures recorded by an electronic recorder controller. To determine reliability, changes in the position of the flow diversion valve were examined to identify process deviations and were compared with the event marker on circular charts. The review of the data file by the actual time method was an effective alternative to the electronic recorder controller for monitoring the completeness of data in the safety files. Off-line review to determine reliability required approximately 10 min/d of records.
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Modeling, monitoring and control strategies for high temperature short time Pasteurization systems — 3. Statistical monitoring of product lethality and process sensor reliability
Food Control, 1998Co-Authors: Antoine Negiz, Joseph E. Schlesser, Ali Cinar, P. Ramanauskas, David J. ArmstrongAbstract:Abstract Statistical process monitoring (SPM) is used in food processing industries to improve productivity and product quality. SPM can also provide information to operators on how close a process is to non-compliance to product safety limits, and carry out periodic checks of sensor accuracy at high frequency. Traditional SPM tools such as Shewhart charts are not appropriate for continuous food processes because of autocorrelation in data. Four alternative SPM techniques are presented and applied to high temperature short time (HTST) dairy Pasteurization. The study attempted to achieve compliance of the HTST process operation with the recommended Pasteurized Milk Ordinance by providing a margin between the alarm limits of the monitoring chart and the safety limits. Monitoring of residuals and parameter change detection techniques are used for monitoring processes with autocorrelated variables. Hotelling's T2 and residuals of canonical variates techniques are used for monitoring multivariable processes.
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Automated Control and Monitoring of Thermal Processing Using High Temperature, Short Time Pasteurization
Journal of dairy science, 1997Co-Authors: Joseph E. Schlesser, David J. Armstrong, Ali Cinar, P. Ramanauskas, A. NegizAbstract:Abstract High temperature, short time Pasteurization was used to evaluate a computer-based system for controlling the Pasteurization process, acquiring data, and monitoring records. Software was used for the control of hot water temperature, flow rate through the centrifugal timing pump, and diversion of underprocessed product. Three types of control strategies were conducted: single loop, cascade, and multivariable. The single loop control strategy showed the most rapid responses to temperature changes, but the temperature response curve was slowest to return to its set point. The cascade control strategy showed slower recoveries to temperature changes, but the temperature response curve was smoother. The multivariable control strategy responded slightly faster than the cascade control strategy, and the temperature response curve was slightly smoother than the cascade control strategy. The multivariable control strategy was able to control the flow diversion valve by the use of a lethality controller. The data acquisition system, used to monitor the data obtained from the high temperature, Short-Time Pasteurization system, was within ±0.1°C of the temperature recorded by the safety thermal limit recorder. Reliability was determined by examining the changes in the position of the flow diversion valve to identify process deviations and by comparing the changes to the event marker on circular charts. The data acquisition system was an effective alternative for monitoring the completeness of data.