Progress 12/15/15 to 12/14/19
Outputs
Target Audience:Food scientists and the dairy industry Changes/Problems:None What opportunities for training and professional development has the project provided?I trained two undergraduates (Logan Sherman and Jeffrey Jarman) and two graduate students (Vidita Deshpande and Namhyeon Park) on laboratory techniques required to confuct this research. How have the results been disseminated to communities of interest?I have two peer reviewed publications (2016 and 2020), two international presentations (2020) and one regional presentation related to this research (2019). What do you plan to do during the next reporting period to accomplish the goals?This project has been completed
Impacts
What was accomplished under these goals?
Thermophilic bacteria and spores survive pasteurization and reduce milk and milk product quality. This research investigated the use of thermosonication (sonication combined with heat) as a processing treatment for milk to reduce the thermophilic spoilage microbial population allowing for an extended shelf live and improved quality without affecting milk properties. The first objective was to evaluate the effect of thermosonication in batch and a continuous flow system on the survival of thermophilic and indigenous milk microflora. The second objective was to evaluate the effect of thermosonication in a continuous pilot scale flow system that simulated high-temperature short-time (HTST) pasteurization on the shelf life and sensory properties of milk. Vegetative cells and spores of Geobacillus stearothermophilus, Anoxybacillus flavithermus, and Bacillus subtilis (spores only) were treated with either heat alone or thermosonication in a batch system from 0-120 s to identify microbial reduction in tryptic soy broth and 2% fat milk at 72 and 73 C. Thermosonication reduced the number of vegetative cells and spores of all organisms in both solutions as compared to the application of heat alone. D-values for vegetative cells were calculated and were reduced after thermosonication particularly for G. stearothermophilus. Maximum reduction in vegetative cells was 1 log after 30-45 s. Maximum log reduction in thermophilic spores was ≤ 0.2 after 120 s of thermosonication, which may not have a significant effect on overall quality of milk and milk products in scale up systems. The effect of thermosonication along with heat in a lab-scale continuous system on the survival of G. stearothermophilus inoculated into sterile milk and indigenous microbes in raw milk was evaluated using a plate heat exchanger (PHE) and a flow-through sonicator, both set at 72C with control samples flowing through the system with the sonicator off. Additionally, the location of the sonicator, pre or post PHE, was investigated with G. stearothermophilus cells. Two different flow rates resulted in two settings (setting 1: 27.7 s total heating time with or without 11.9 s of sonication; setting 2: 20.3 s total heating time with or without 7.1 s of sonication). Thermosonication in a lab-scale continuous system increased the log reductions for G. stearothermophilus cells which was dependent on the residence times in the PHE and sonicator. However, the effect of thermosonication overall was not significant. Longer residence times (setting 1), showed higher reductions of G. stearothermophilus cells, with log reductions ranging between 0.45-0.54 for treatments as compared to 0.25-0.37 for control. The position of the sonicator (before or after the PHE) did not have a significant effect on control and treatment (within each setting) log reductions of G. stearothermophilus. Thermosonication significantly decreased the indigenous microflora in milk as compared to heat alone at both settings. Longer residence times (setting 1) had significantly higher log reductions at week 0, and treatment samples had significantly higher reductions than control during storage time at both the settings. Thermosonication was integrated into a high-temperature short time pasteurization system which included a pre-heat PHE (set at 80°C), a PHE set at 75°C followed by a 15 s hold (pasteurization conditions), a flow through sonicator (11 s resident time, set at 73°) and a cooling PHE set at 0°C. Control samples flowed through the system with the sonicator turned off. Raw whole milk was passed through this system and evaluated for microbial count, pH, casein/total protein (CN/TP) content, and free fatty acids (FFA). The average microbial count was significantly lower for thermosonication samples as compared to control after treatment and during shelf life. Control samples showed signs of curdling at 4 weeks while the treatment samples showed no signs of curdling at 6 weeks. The pH, CN/TP content, and FFA content for both control and thermosonication were not significantly different after processing, but pH and CN/TP decreased during the shelf life while FFA content increased. Thermosonication samples had significantly higher pH values as compared to control at respective weeks. Lower FFA values and higher CN/TP values were observed for thermosonication samples during shelf life as compared to control which is related to the microbial count as discusses above. The effect of thermosonication on consumer liking was evaluated using the sonication system described above without the PHE, just flowing through the sonicator. Commercial pasteurized 2% fat milk was preheated to 70°C in a water bath before flowing through the sonicator for a heat only or thermosonication at 11 s at 72°C. The first consumer panel was conducted 24 hrs after milk treatment. Control samples were rated significantly higher by the panelists than thermosonication samples for all attributes (overall appearance, smell, flavor and overall liking), except for color. Overall panelists thought that the control samples, had a slightly cooked flavor and were not as sweet. Whereas, treatment samples tasted more cooked with notes of maltiness, smokiness, and a strange after taste. To investigate the aftertaste further, a focus group was conducted with 6 panelists over a period of 6 days and the cooked flavor was found to be absent at day 4. A second consumer panel was designed where samples from day 1 and day 4 were used for both control and treatment. Panelists were asked to indicate their liking for all the four samples for flavor and overall liking. There were significant differences between the control and treatment milks on day 1, but no significant differences were observed on day 4 between the samples. All the titanium concentrations were at normal background content in control and treatment for bovine milk. Thus, the off flavors detected in the consumer panel could not have been due to deterioration of the titanium tip used in the sonication assembly leading to dissolution in the milk. Thermosonication in a continuous system coupled with pasteurization conditions successfully improved the shelf life attributes of whole milk during storage as compared to pasteurization alone which could potentially increase the shelf of milk by 2 weeks. The average microbial count was lower for thermosonicated samples as compared to control throughout its shelf life. Shelf life of control and thermosonication samples was estimated to be 4 and 6 weeks, respectively. The pH of milk for both control and treatment were not significantly different immediately after processing, but decreased during the shelf life, with thermosonicated samples having significantly higher pH values as compared to control at respective weeks. The FFA content increased over shelf life with thermosonication samples having significantly lower FFA at the end of the shelf life. The first consumer panel showed significantly lower scores for overall appearance, smell, flavor, and overall liking of treatment samples but not for color. Panelists commented on thermosonication samples having an off flavor, which when further investigated in a focus group seemed to decline after 2-4 days. The second consumer panel performed on control and treatment samples on day 1 and day 4 after processing showed no significant difference between treatment samples on day 4 as compared to control samples on day 1 and 4.Therefore, application of thermosonication in a continuous system using practical residence times (10-15 s) coupled with pasteurization may improve the overall milk quality and potentially increase the shelf life of milk. Future studies should focus on investigating thermosonication conditions for industrial applications and changes in sensory attributes in scale up systems.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Deshpande, V. K., & Walsh, M. K. (2018, January). Effect of sonication on the viscosity of reconstituted skim milk powder and milk protein concentrate as influenced by solids concentration and temperature. International Dairy Journal., 78, 122-129.
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Walsh, M. K., & Beatty, N. (2016, May). Influence of thermosonication on Geobacillus stearothermophilus inactivation in skim milk. International Dairy Journal., 61, 10-17
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2019
Citation:
Presentations
Deshande, V. (Presenter & Author), Walsh, M. K. (Author Only), American Dairy Science Association, "Effect of sonication combined with heat to improve the microbial quality of milk," American Dairy Science Association, Ohio. (June 2019)
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2019
Citation:
Presentations
Deshpande, V. (Presenter & Author), Walsh, M. K. (Author Only), American Dairy Science Association, "Effect of thermosonication in a batch system on the survival of thermophilic bacteria in milk," American Dairy Science Association, Ohio. (June 2019)
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2019
Citation:
Presentations
Vidita, D. (Presenter & Author), Walsh, M. K. (Author Only), Bonneville Section of IFT Regional Meeting, "Effect of thermosonication to improve the microbial quality of milk," Bonneville Section of IFT Regional Meeting, Salt Lake City, UT. (April 2019)
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2018
Citation:
Presentations
Walsh, M. K., Deshpande, V. K. (Author Only), American Society of Nutrition, USDA/NIFA, "Application of ultrasound with pasteurization to improve the microbial quality of milk," American Society of Nutrition, USDA/NIFA, Boston MA. (June 8, 2018)
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Progress 12/15/17 to 12/14/18
Outputs
Target Audience:Food scientists and the dairy industry Changes/Problems:I received a one year extension on this project. It now has an end date of December 2019. No other delays are expected. What opportunities for training and professional development has the project provided?I have trained one undergraduate researcher (Jeffrey Jarman) and one graduate student (Vidita Deshpande) on the laboratory techniques required to conduct this research. How have the results been disseminated to communities of interest?I have two publications related to this research that are published in international peer-reviewed journals and I attended one international meeting to present this research. What do you plan to do during the next reporting period to accomplish the goals?We will complete Objective 2 during the first half of the 2019 year and also conduct the sensory analysis described in Objective 3 also in 2019.
Impacts
What was accomplished under these goals?
Accomplishments for 2018. A continuous flow system consisting of a plate heat exchanger (PHE) and a sonicator (SON) with a 261 mL flow-through cell, and a masterflex pump were used for the thermosonication experiments. Initial experiments used sterile 2% fat milk inoculated with Geobacillus stearothermophilus (GS). Three different flow rates resulting in different residence times were used including Setting 1: 0.83 L/min, 15.8 s pasteurization (PAS), 18.8 s SON, Setting 2: 1.28 L/min, 13.2 PAS, 12.8 SON, Setting 3: 1.8 L/min, 12.1 PAS, 8.1 SON. The placement of the PHE was before and after the SON and plate counts were used to determine microbial reduction. PAS alone reduced the microbial count, but the reduction was not significant. There was an increase in microbial reduction with longer residence times (Setting 1). SON and PAS combined significantly reduced the microbial count with higher microbial reductions with an increase in residence times (Setting 1). Position of the PHE did not have a significant effect on reduction of GS cells; therefore we have the PHE before the SON for continued experiments. To determine the effects of thermosonication on the reduction of indigenous microbes in milk, 5 L of raw milk obtained from Utah State University's dairy processing plant was left at room temperature to increase the microbial load and treated at Settings 1 and 2. Aliquots were stored at 4 C in sterile containers for 6 weeks and microbial counts were done weekly. Thermosonication had higher log reductions as compared to pasteurization. Samples with PAS only had drastically higher microbial growth after 2 weeks as compared to thermosonicated samples. We also Ran 5 L of raw milk on the collection day with Settings 1 and 2 conducted microbial counts up to 7 weeks of storage at 4 C. Raw milk treated at Setting 1 showed greater than a 2 log reduction with thermosonication as compared with PAS alone that showed a l log reduction. On average, milk treated with thermosonication had lower microbial counts than milk treated with only PAS. Milk treated at Setting 1 had significantly lower microbial counts than milk treated at Setting 2. For all treatments, storage time had a significant effect with higher microbial counts upon storage at 4 C. We are in the process of analyzing the milk for free fatty acids and the nitrogen distribution.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Deshpande, V. K., & Walsh, M. K. (2018, January). Effect of sonication on the viscosity of reconstituted skim milk powder and milk protein concentrate as influenced by solids concentration and temperature. International Dairy Journal., 78, 122-129
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2018
Citation:
Walsh, M. K., Deshpande, V. K. (Author Only), American Society of Nutrition, USDA/NIFA, "Application of ultrasound with pasteurization to improve the microbial quality of milk," American Society of Nutrition, USDA/NIFA, Boston MA. (June 8, 2018)
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