Progress 07/01/17 to 06/30/21
Outputs
Target Audience:The target audiences are sprout growers and seed suppliers. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Two MS students worked on this project and one of them has graduated. Both students had the opportunityto attend the IAFP Annual Meetings. How have the results been disseminated to communities of interest?In addition to giving a presentation at the 2021 IAFP Annual Meeting and publishing a MS thesis online, we are currently preparing a manuscript for publication. The dry heat processing technology developed in this study is a much better alternative to the FDA recommended chlorine disinfection method. It can effectively decontaminate mung bean and alfalfa seeds while allowing seeds to germinate and grow normally. Because of this promising result, we have applied and received a graduate fellowship from our university to support the graduate student working on this project for two more semesters after this grant expired on June 30, 2021. The student is currently fine-tuning the dry heat processing parameters to further optimize the process. After this optimization, we plan to disseminate our results to sprout growers and seed suppliers. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Impact statement: Outbreaks associated with seed sprouts occurs almost on an annual basisthroughout the world. Currently, there is no intervention that can effectively decontaminate seeds without affecting seed's viability. The FDA recommended practice, disinfecting seeds with 20,000 ppm chlorine, could only achieve 2 -3 log reductions of Salmonella. It also negatively impacts final sprout quality. The dry heat processing technology developed in this project is able to effectively decontaminate mung bean (> 5 log reduction of Salmonella) and alfalfa seeds (> 4 log reduction of Salmonella) while preserving final sprout quality. The dry heat processing technology is much more effective than the chlorine treatment since it is capable of targeting superficial and internalized pathogens. This technology is very attractive to both health-conscious consumers and organic producers since chemicals are not involved. In addition, the dry heat processing technology is simple and low cost and can be easily implemented by sprout producers. The overall goal of this study is to develop effective treatments for seed decontamination while preserving seed's ability to germinate and grow normally. The specific objectives are: 1. To develop effective interventions for inactivation of Salmonella and E. coli O157:H7 on seeds. 2. To evaluate the effect of selected decontamination treatments on seed viability and sprout quality. Since these two objectives were intertwined, they were presented and discussed together. Two processing technologies, dry heat treatment and water-assisted UV treatment, were proposed and evaluated in this study. 1. Dry heat treatment 1) Major activities completed/experiments conducted Preliminary study indicated that Salmonella is more heat resistant than E. coli O157:H7. Therefor this study was focused on Salmonella. To determine the effect of seed's water activity level and dry heat temperature on thermal inactivation of Salmonella, sprouting seeds (alfalfa, mung bean, red clover, and radish) were dip-inoculated with a four-strain Salmonella cocktail to a final level of 6-7 log CFU/g. The inoculated seeds along with un-inoculated seeds were dried to water activities of 0.10, 0.20 and 0.30. They were then treated in hot air at 70 and 75 ºC for selected time intervals.The inoculated seeds (heat-treated and un-treated) were used for determining Salmonella counts and un-inoculated seeds (heat-treated and un-treated) were used for growing sprouts. Un-inoculated seeds were grown in sprouters for 8 days, and final weights of sprouts were measured. The sprout yield ratio was computed by dividing the sprout weight of heat-treated seeds by the sprout weight of un-treated (control) seeds. 2) Data collected and discussion of results Water activity level of seeds played a critical role in Salmonella inactivation by dry heat and seeds viability. Increasing water activity of seeds improved Salmonella inactivation by dry heat. For example, to achieve a > 5 log reduction of Salmonella on mung bean seeds, seeds with water activity levels of 0.20 and 0.30 need to be treated at 75 ºC for 30 and 22 h, respectively. Mung bean seeds with lower water activity (0.20) germinated and grew better than seeds with higher water activity (0.30) after they were dry heat-treated at 75 ºC. Decreasing dry heat temperature from 75 to 70 ºC increased the treatment time needed to achieve a > 5 log reduction of Salmonella, but better-preserved mung seed's viability. Dry heat treatment of mung bean seeds with water activity of 0.2 for 40, 50, and 60 h at 70 ºC resulted in 4.6, 5.1 and 5.6 log reductions of Salmonella, respectively. When un-inoculated mung bean seeds with 0.2 water activity were treated at 70 ºC for 40, 50, and 60 h, they successfully germinated and grew to sprout yield ratios of 1.00, 0.99, and 0.93, respectively. For alfalfa seeds, water activity of seeds needed to be decreased from 0.2 to 0.1 to better preserve seed's viability. Dry heat treatment of alfalfa seeds with water activity of 0.2 for 50 and 60 h at 70 ºC resulted in 4.2 and 5.3 log reductions of Salmonella, respectively. When un-inoculated alfalfa seeds with 0.2 water activity were treated at 70 ºC for 50 and 60 h, sprout yield ratios for the treated seeds were 0.74 and 0.61, respectively. Dry heat treatment of alfalfa seeds with water activity of 0.1 for 80 and 100 h at 70 ºC resulted in 3.3 and 4.3 log reductions of Salmonella, respectively. When un-inoculated alfalfa seeds with 0.1 water activity were treated at 70 ºC for 80 and 100 h, sprout yield ratios for the treated seeds were 1.00 and 0.96, respectively. Red clover and radish seeds were more sensitive to heat treatment. For example, when un-inoculated red clover and radish seeds with 0.2 water activity were treated at 70 ºC for 60 h, sprout yield ratios for the treated seeds were 0.45 and 0.00, respectively. 3) Key outcomes a. Dry heat treatment of mung bean seeds with water activity of 0.2 for 50 h at 70 ºC resulted in 5.1 log reductions of Salmonella and a sprout yield ratio of 0.99. a. Dry heat treatment of alfalfa seeds with water activity of 0.1 for 100 h at 70 ºC resulted in 4.3 log reductions of Salmonella and a sprout yield ratio of 0.96. c. Red clover and radish seeds were sensitive to heat treatment and no effective dry heat treatment could be identified. 2. Water-assisted UV treatment 1) Major activities completed/experiments conducted Alfalfa seeds were inoculated with a four-strain cocktail of Salmonella to a level of 6.7 log CFU/g and then dried to a water activity level of 0.40. The dry inoculated seeds were washed in agitated tap water in a round-shape stainless steel bowl while being exposed to UV light (water-assisted UV treatment) at intensity levels of 10 and 30 mW/cm^2. The water agitation speed was set at 110, 150, or 230 RPM. Inoculated seeds were also washed in 50, 100, and 200 ppm chlorine without exposure to UV light. For both the chlorine washing and UV treatment, alfalfa seed samples were treated for 5, 10, 15, and 30 min. After UV and chlorine treatments, the Salmonella counts in the seeds were determined. Un-inoculated alfalfa seeds were also similarly treated by UV and chlorine washing. Treated and un-treated seeds were then germinated and grown for 8 days and the sprout yield ratio was computed. 2) Data collected and discussion of results The water-assisted UV treatments achieved 1.4-2.1 log reduction of Salmonella on alfalfa seeds. The UV intensity and treatment time did not significantly affect Salmonella inactivation. Chlorine washing achieved 1.4-2.3 log reduction of Salmonella on alfalfa seeds. The overall results showed the potential damage on alfalfa seeds due to the combined application of UV and high-speed agitation. After 8 days of growth, the alfalfa sprout for the UV-treated seeds weighted around 70% of the control (a sprout yield ratio of 0.70) regardless of the agitation speeds. The 200 ppm chlorine treatment, however, resulted in a sprout yield ratio of 0.96. Since the water-assisted UV treatment was not effective for seed decontamination, other types of seeds were not investigated. 3) Key outcomes The water-assisted UV treatment is not a viable method for seed's decontamination.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Yao, S. and Chen, H. 2021. Inactivation of Salmonella on mung bean sprouting seeds using dry heat treatment. 2021 International Association for Food Protection Annual Meeting, Phoenix, Arizona.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2020
Citation:
Darelius, C. 2020. Inactivating Salmonella on alfalfa sprouting seeds and increasing seed viability using dry thermal treatments. Master thesis. University of Delaware. https://udspace.udel.edu/handle/19716/28007.
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Progress 07/01/19 to 06/30/20
Outputs
Target Audience:The target audiences are sprout growers and seed suppliers. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The graduate student working on this project attended the IAFP Annual Meeting in 2020. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?Further research on dry heating will be conducted on other sprouting seeds. The effect of dry heating temperature and water activity of seeds on Salmonella inactivation and sprout yield will be determined.
Impacts
What was accomplished under these goals?
Alfalfa seeds were inoculated with a four-strain cocktail of Salmonella to a level of 6.7 log CFU/g. Seeds were then dried for 2 days at room temperature to water activity level of 0.40. The dry inoculated seeds were washed in agitated tap water in a round-shape stainless steel bowl while being exposed to UV light (water-assisted UV treatment) at intensity levels of 10 and 30 mW/cm^2. The water agitation speed was set at 110, 150, or 230 RPM. Inoculated seeds were also washed in 50, 100, and 200 ppm chlorine without exposure to UV light. For both the chlorine washing and UV treatment, alfalfa seed samples were treated for 5, 10, 15, and 30 min. After UV and chlorine treatments, the Salmonella counts in the seeds were determined. Un-inoculated alfalfa seeds were also similarly treated by UV and chlorine washing. Treated and un-treated seeds were then germinated and grown for 8 days. The final weights of sprouts were measured. The water-assisted UV treatments achieved 1.4-2.1 log reduction of Salmonella on alfalfa seeds. The UV intensity and treatment time did not significantly affect Salmonella inactivation. Chlorine washing achieved 1.4-2.3 log reduction of Salmonella on alfalfa seeds. The overall results showed the potential damage on alfalfa seeds due to the combined application of UV and high-speed agitation. After 8 days of growth, the alfalfa sprout for the UV-treated seeds weighted around 70% of the control (without UV and chlorine treatments) regardless of the agitation speeds. The 200 ppm chlorine treatment, however, resulted in a sprout weight that was 96% of the control.
Publications
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Progress 07/01/18 to 06/30/19
Outputs
Target Audience:The target audiences are sprout growers and seed suppliers. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The graduate student working on this project attended the IAFP Annual Meeting in 2019. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?Further research will be conducted at higher heating temperatures such as 80 and 85°C to identify better and faster treatment conditions. The results obtained from the alfalfa seeds research will be used to guide our study on other sprouting seeds.
Impacts
What was accomplished under these goals?
Alfalfa seeds were inoculated with a four-strain cocktail of Salmonella to a level of 10^7 CFU/g. Seeds were then dried to a water activity level of ~0.20. Water in a volume of 0 (no water added), 0.1 or 0.2 mL was added to 10 g of the inoculated seeds, vortexed, and left to sit for 1 hour. Inoculated seeds with/without water added were placed into a sealed container and then heated in dry air at 72.5°C for up to 24 hours. After heating, the Salmonella counts in the seeds were determined. Un-inoculated seeds were also dried to a water activity of ~0.20. They were then underwent the same addition of 0, 0.1 or 0.2 mL of water into 10 g of seeds, vortexed, and left to sit for 1 hour. Seeds were then heated as described above. After heating, seeds were germinated and grown for 8 days. The final weights of sprouts were measured and divided by the dry weight of seeds (10 g) to calculate the sprout yield. The results demonstrated that the water activity of seeds was vital; small changes could drastically affect both sprout growth and inactivation of salmonella. Addition of water increased the Salmonella inactivation, but decreased the sprout yield. For the 12 h treatment at 72.5°C, addition of 0, 0.1 and 0.2 mL of water resulted in 3.5, 4.0 and 4.3 log reduction of Salmonella. Compared with the control seeds without heat treatment, the 12 h treatment increased the sprout yield of seeds without water added by 23.5%, but deceased the sprout yield of seeds with 0.1 and 0.2 mL water added by 28.3% and 71.2% respectively. For the 18 h treatment at 72.5°C, addition of 0 and 0.1 mL of water resulted in 4.6 and 5.4 log reduction of Salmonella. Compared with the control seeds without heat treatment, the 18 h treatment increased the sprout yield of seeds without water added by 17.6%, but deceased the sprout yield of seeds with 0.1 mL water added by 56.8%. Further extending the treatment time at 72.5°C to 24 h slightly increased Salmonella inactivation, but at the expense of decreasing sprouting yield for both seeds without water added and seeds with 0.1 mL water added. In conclusion, the recommended treatment conditions for alfalfa seeds are 18 h heat treatment at 72.5°C on seeds with water activity of ~0.20 and without addition of water. These treatment conditions achieved > 4 log reduction of Salmonella and increased the sprouting yield compared with the control.
Publications
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Progress 07/01/17 to 06/30/18
Outputs
Target Audience:The target audiences are sprout growers and seed suppliers. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The graduate student working on this project attended the IAFP Annual Meeting in 2018. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?We will determine the effect of water activity of seeds, heating temperature of dry air and treatment time on Salmonella inactivation and seed germination ability. The goal is to identify optimum combinations to achieve targeted level of Salmonella inactivation while maintaining seed germination ability.
Impacts
What was accomplished under these goals?
Alfalfa seeds were inoculated with a four-strain cocktail of Salmonella to a level of 10^7 CFU/g. Seeds were then dried to a water activity level of ~0.35. Water in a volume of 0 (no water added) or 0.1 mL was added to 10 g of the inoculated seeds, vortexed, and left to sit for 1 hour. Inoculated seeds with/without water added were placed into a sealed container and then heated in dry air at 65°C for 5 or 6 days. After heating, the Salmonella counts in the seeds were determined. Un-inoculated seeds were also dried to a water activity of ~0.35. They were then underwent the same addition of 0 or 0.1 mL of water into 10 g of seeds, vortexed, and left to sit for 1 hour. Seeds were then heated as described above. After heating, seeds were germinated and grown for 8 days. The final weights of sprouts were measured and divided by the dry weight of seeds (10 g) to calculate the sprout yield. In general, increasing the water activity of seeds by addition of 0.1 mL of water enhanced the heat inactivation of Salmonella. For example, the heat treatment of 65°C for 5 days reduced Salmonella in seeds without water added by 3.6 log, while addition of 0.1 mL water to seeds enhanced the Salmonella reduction to 4.2 log. Longer treatment time resulted in higher Salmonella inactivation. Treatments at 65°C for 6 days achieved 5.0 log reduction of Salmonella in seeds without water added. Heating at 65°C for 5 or 6 days did not significantly affect the sprout yield of seeds without water added.
Publications
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