IDENTIFICATION AND EVALUATION OF PRE/POST-HARVEST PRACTICES PROMOTING FOOD SAFETY OF LOUISIANA PRODUCE.

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: TERMINATED
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1006167
• Project No.: LAB94289
• Project Start Date: Sep 16, 2015
• Project End Date: Aug 31, 2020

Project Director
Adhikari, AC.

Recipient Organization
LOUISIANA STATE UNIVERSITY
202 HIMES HALL
BATON ROUGE,LA 70803-0100

Performing Department
School of Nutrition and Food Sciences

Non Technical Summary
Produce food safety has emerged as a critical agricultural issue and often presents a significant financial threat to growers and processors. With the recent enactment of the Food Safety Modernization Act (FSMA)" FDA will have a legislative mandate to require comprehensive, science-based preventive controls across the food supply". The potential introduction of foodborne pathogens during growing, harvesting and packing necessitates that producers understand pathogen sources to reduce risk, especially when dealing with fresh produce which are consumed raw. Fresh produce production is water intensive and production requirements are met by drawing water from ground and surface sources. The quality of surface water is variable, and runoff has put the quality of surface water into question. Water can be a source of both plant and human pathogen contamination and growers must take steps to minimize the risk of produce contamination with source water.Pecans are native to lower Midwest and Southeastern United States. Cattle grazing in pecan orchards are one of the most common forms of ground cover management in native pecan groves. However, cattle manure is the main source of foodborne pathogens such as E. coli O157:H7, Salmonella spp. and Listeria monocytogenes. There is a provision in the proposed FSMA produce safety rule that a farm will be exempted from the produce safety rule coverage if the produce from the farm is processed with a kill step. FDA recommends a treatment process must achieve a 5 log reduction (reduction by 100,000 fold) of microbial populations to be regarded as a kill step. If the pecan has 100,000 pathogenic microbes on it, a 5 log reduction would reduce the number of microorganisms to one. Food products processed with a kill step will insure food safety in the final products. Thus, identifying a kill step in pecan processing is vital for reducing the food safety risk associated with pecans grown in orchards that were also used for pasture.UV-C light treatment leaves no residue in the water and crops due to the use of light instead of chemical disinfectants. However, there is a critical knowledge gaps exist regarding the use of UVC light for reducing pathogen risk from agricultural water and fresh produce. This proposed research will work on identification and development of a sustainable and effective pre/post-harvest treatment process utilizing UVC light and hot water treatments for food safety risk reduction.

Animal Health Component

0%

Research Effort Categories

Basic

(N/A)

Applied

100%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
712	0210	1100	40%
712	1211	1100	30%
712	1099	1100	30%

Knowledge Area
712 - Protect Food from Contamination by Pathogenic Microorganisms, Parasites, and Naturally Occurring Toxins;

Subject Of Investigation
1099 - Tropical/subtropical fruit, general/other; 0210 - Water resources; 1211 - Pecan;

Field Of Science
1100 - Bacteriology;

Keywords

uvc light

food safety

pecan

fresh produce

irrigation water

Goals / Objectives
The goal of this research will be to develop pre/post-harvest treatments methods to minimize the food safety risk associated with fresh produce.The objectives of this proposed research are:1. Evaluate the efficacy of UV-C light treatment on food safety risk reduction from irrigation water2. Identify the time and temperature parameters for hot water treatment during pecan processing that can be regarded as a kill step3. Determine the effectiveness of UV-C light treatment on reducing bacterial pathogens on the surface of fruits

Project Methods
Objective 1: Irrigation water source for this study will be the water from a pond located at the LSU AgCenter Botanic Gardens. Pond water (750 liters) will be collected in a 250-gallon (around 946 liters) water tank (food-grade plastic). Water will be stirred and pH and turbidity will be recorded.E. coli strains and inoculation:A cocktail of three ATCC generic E. coli strains (23716, 25922 and 11775) will be used in this study. The 750 ml stationary phase cocktail strain will be added to 750 liter water to give approximately 105 to 106 CFU/liter.UV-C treatment:Water inoculated with generic E. coli from the tank will be UV treated in a continuous process by running through UV treatment unit PMD150C1/4 (Aquionics, Erlanger, KY.). This unit has a maximum disinfection capacity of 440 U.S. gal/min however; a flow rate of 15 U.S. gal/min will be used in this study.Sampling and microbial assessment of UV treated surface irrigation water:To access the microbial quality of the pond water, water sample will be collected just before adding generic E. coli cultures. After addition of generic E. coli cultures a vigorous mixing will be done by the help of a cleaned sanitized paddle. Water will be sampled pre- and post-UV treatment and at the final point of discharge from each irrigation system. Water temperature, turbidity, total dissolved salts (TDS), electrical conductivity (EC) and pH of all samples will be measured. Data appropriate statistical tests will be used to evaluate the efficacy of the UV-C treatment system in reducing generic E. coli populations in irrigation water at different points in the irrigation system.Vegetable production and irrigation:Cantaloupe will be planted twice a year over two years using sustainable growing practices at the LSU AgCenter Burden Center (Baton Rouge, LA). Field measuring 56 x 140 ft will be divided into two sites (56 x 60 ft). Cantaloupe will be planted in each site at two different dates for two years. Each site will be divided into twelve soil plots having individual plots measuring 5 x 10 ft. Cantaloupe will be grown on black plastic and irrigated with UV treated or non-treated generic E. coli inoculated surface water using a drip or sprinkle irrigation system.Sampling and microbial assessment of cantaloupe irrigated with UV treated and non-treated surface water:At each growing date, cantaloupes will be harvested four times with a 24 h interval. Each cantaloupe will be suspended in (200 ml) phosphate buffer saline and massage for 2 min to dislodge microorganisms present on the surface. Wash will be evaluated for generic E. coli.Statistical analysis:Data will be analyzed using mixed model procedure of SAS ®. A randomized complete block design with fixed effects of irrigation system and treatment will be used to determine differences in generic E. coli levels of UV-C treated and non-treated generic E. coli inoculated water. For cantaloupe data, harvest will also be considered as a fixed effect. Individual plot will be designated as blocks (random factor).Objective 2: In-shell pecans that are commonly grown in Louisiana will be selected based on factors such as high average tonnage produced annually and difference in shell thickness, shell-out percentage (percent of in-shell nut consisting of nutmeat), size, and shape of nuts.Selection of microorganisms for the study:Salmonella spp, E. coli O157:H7 and generic E. coli will be used in this study. A mixture of at least three serotypes of each organism will be used. Serotypes that were isolated from nuts or clinical isolates involved in outbreaks will be selected.Inoculation and Enumeration of In-shell pecans:Undamaged in-shell pecans (500 g) maintained at room temperature will be immersed in the 1,200ml cell suspension for 1 hour. Pecans will be removed from the cell suspension and drained. Duplicate samples (five pecans per sample) will be used to analyze the populations for each organism. GenericE. colisamples will be plated on Violet Red Bile Agar andE. coliO157:H7 will be plated on Sorbitol MacConkey Agar (SMAC) supplemented with Cefixime-Tellurite Supplement utilizing the spread plate method. Duplicate plates will be incubated at 37°C for 24h.Salmonellasamples will be plated on XLD agar plates and will be incubated at 35°C for 24 hr. The in-shell pecans after inoculating each bacterial cocktail will be stored in a sealed plastic bag at 22oC overnight to mimic the conditioning treatment normally perform by a pecan sheller prior to cracking. Conditioned nuts will be submerged in hot water at 70, 80, 90 and 99oC for 3, 6, 9, and 12 min. After heat treatment samples will be transferred to stomacher bag and immersed into ice to bring down the temperature as soon as possible. After cooling the nuts will be crushed with a hammer and transfer into another stomacher bag containing 200 ml lactose broth. Each bacterial species will be mixed and enumerated as described above.Statistical analysis:Experiments will be replicated at least three times. Data will be analyzed with a general linear model on SAS software. The death kinetics data will also be used to fit Wibull model and the predicted value will be analyzed for least significant differences using SAS software.Objective 3:Fresh fruits grown locally will be purchased from a local retail outlet and store at 7 °C for less than 24 hours before conducting the experiments. E. coli O157:H7 strains ATCC 43890 (human feces isolate known to produce shiga-like toxin I), ATCC 43895 (raw hamburger outbreak strain known to produce shiga-like toxin I and II), and SEA 13B88 (unpasteurized Odwalla apple juice outbreak isolate) and L. monocytogenes strains NRRL B-33006 (serotype 1/2b, isolated from garlic), NRRL B-33069 (serotype 1/2a, isolated from bovine milk) and NRRL B-33385 (serotype 4b, isolated from clinical isolate) will be used in this study. Salmonella isolates will be selected to align with other studies that have examined bacterial response on fruit surfaces. Fruits will be placed into the bucket containing prepared inoculation cocktail solution and will be vigorously massaged for ten minutes from the outside of the bag to facilitate bacterial adherence to the surface of the cantaloupe. The fruits will then be placed inside the laminar flow hood under forced air to promote microbial attachment. UV-C treatment on fruit surfaces:The UV-C treatment of fruits will be carried out inside a UV-C Emitter™ Table-top System at a wavelength of 254 nm at room temperature as described by Syamaladevi et al., 2013. Selected fruit surfaces, inoculated with each pathogen, will be exposed to different UV-C doses. The motorized roller will keep the fruit rolling during the treatment process thus exposing maximum surface of the fruit to the UV source. Enumeration: Generic E. coli samples will be plated on Violet Red Bile Agar and E. coli O157:H7 will be plated on Sorbitol MacConkey Agar (SMAC) supplemented with Cefixime-Tellurite Supplement utilizing the spread plate method. Duplicate plates will be incubated at 37°C for 24h. Listeria monocytogenes samples will be plated onto Oxford Agar base augmented with Modified Oxford Supplement (MOX) and will be incubated at 30°C for 24-48 hr. Salmonella samples will be plated on XLD plates and will be incubated at 35°C for 24 hr. Statistical analysis: Differences in survival of all species after the UV-C treatments will be analyzed for significance using Student's t-test following one-way analysis of variance (ANOVA) JMP-IN (version 11, SAS Institute Inc., Cary, NC). The statistical difference will be at p<0.05. Data will be based on three separate replications for each treatment.

Progress 09/16/15 to 08/31/20

Outputs
Target Audience:Growers, Food Processors, Extension agents, Scientists, Undergraduate, and graduate students, farmers market organizations, Louisiana Sweet Potato Association, Louisiana Fruits and Vegetable Growers Association, Louisiana Pecan Growers Association Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Graduate and undergraduate students received hands-on experience in produce food safety and microbiological techniques. How have the results been disseminated to communities of interest?Several Good Agricultural Practices and Good Handling Practices workshops, Food Safety Modernization Act (FSMA) training, and other on-farm food safety trainings were hosted to disseminate the results to growers and producers. Results were also published in scientific journals to share results with the scientific community. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? We evaluated the ultraviolet (UV-C) light treatment for microbial inactivation in agricultural waters with different levels of turbidity. All tested doses of the UV-C treatment reduced the E. coli levels significantly (p < .05) in the water samples with the turbidity levels up to 23.32 NTU. The decrease in turbidity from 23.32 to 10.93 NTU increased the level of reduction by more than 2.15 log most probable number (MPN)/100 ml). UV-C treatment effectively reduces the microbial load in agricultural water; however, the turbidity of water may significantly affect disinfection efficacy. This study also demonstrated that the sprinkler system resulted in a higher level of contamination of cantaloupes compared with drip irrigation. The results indicated that UV-C treatment could be a promising strategy in reducingproduce safety risks associated with irrigation water. We also investigated the effect of chlorine and lactic acid on the viability of E. coli O157: H7 on spinach leaves right after treatment and during refrigerated storage using propidium monoazide staining and real-time PCR (PMA-qPCR). Chlorine and lactic acid wash resulted in the reduction in viable E. coli O157: H7 counts by 2.51 and 3.43 log CFU/g, respectively. After 48h of refrigerated storage, the viable E. coli O157:H7 population was significantly reduced by 2.86 log CFU/g on chlorine-treated leaves and by 4.42 log CFU/g on lactic-treated leaves. This study emphasized the potential effect of chlorine and lactic acid in reducing viable E. coli O157: H7 population on produce surfaces. The effect of hot water pre-treatment of in-shell pecans on physicochemical properties, consumer acceptance, and purchase intent of dehulled and roasted kernels was evaluated. In-shell pecans were first subjected to hot water at 70, 80, and 90ºC for 8.6, 6.6, and 4.6 min, respectively; and kernels were later dry roasted at 160ºC for 10 min. The physicochemical properties of hot water-treated and untreated nuts before and after roasting were determined. Furthermore, consumer acceptance and purchase intent of the roasted kernels were determined. Hot water treatment alone and subsequent roasting had minimal effect on pecans' physicochemical properties. Consumers liked (P<0.05) the color and aroma of treated pecans. No effect (P>0.05) of pre-treatment was observed on the acceptability of other sensory attributes. The safety claim increased treated pecans' overall liking; however, it decreased purchase intent. Hot water treatment showed promise as a post-harvest microbial intervention strategy without affecting the physicochemical properties and consumer acceptability. We investigated UV-C light inactivation of Escherichia coli O157: H7 and Listeria monocytogenes on the surface of organic apples, pears, strawberries, red raspberries, and cantaloupes. Our results demonstrate that bacterial pathogens on fruit surfaces respond differently to UV-C light exposure. Inactivation rates were higher for less hydrophobic fruits with smoother surfaces (apples and pears) as compared to fruits with rougher surfaces (cantaloupe, strawberry, and raspberry). Findings indicate that UV-C light can effectively reduce E. coli O157: H7 and L. monocytogenes populations on fruit and berry surfaces. However, surface characteristics influence the efficacy of UV-C light.

Publications

• Type: Journal Articles Status: Published Year Published: 2020 Citation: Yemmireddy, V., Carson, C., Moreira, J., and Adhikari, A. 2020. Effect of pecan variety and the method of extraction on the antimicrobial activity of pecan shell extracts against different foodborne pathogens and their efficacy on food matrices. Food Control. https://doi.org/10.1016/j.foodcont.2020.107098
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Adhikari, A., Chhetri, V., and Camas A. 2020. Evaluation of microbiological quality of agricultural water and effect of water source and holding temperature on the stability of indicator organisms level using seven US EPA approved methods. Journal of Food Prot. 83:249-255
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Adhikari, A., E. K. Parraga, V. S. Chhetri, M. Janes, K. Fontenot, and Beaulieu, J. C. 2020. Evaluation of Ultraviolet (UV-C) light treatment for microbial inactivation in agricultural waters with different levels of turbidity. Food Science & Nutrition. 8:1237-1243
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Chhetri, S. V., Han, Y., J. Marlene, and Adhikari, A. 2020. Evaluation of viability of E. coli O157: H7 on chlorine and lactic acid-treated spinach leaves using combined propidium monoazide staining and real-time PCR. LWT-Food Science and Technology. https://doi.org/10.1016/j.lwt.2020.109259

Progress 10/01/18 to 09/30/19

Outputs
Target Audience:Growers, Food Processors, Extension agents, Scientists, Undergraduate, and graduate students, farmers' market organizations, Louisiana Sweet Potato Association, Louisiana Fruits and Vegetable Growers Association, Louisiana Pecan Growers Association Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Graduate and undergraduate students received hands-on experience in produce food safety and microbiological techniques. How have the results been disseminated to communities of interest?Several Good Agricultural Practices and Good Handling Practices workshops, Food Safety Modernization Act (FSMA) training, and other on-farm food safety training were hosted to disseminate the results to growers and producers. Results were also presented during the IAFP and IFT annual conference and the Tri-State pecan growers meeting.Five peer-reviewed manuscripts and several fact-sheets were published as a result of this project. What do you plan to do during the next reporting period to accomplish the goals?We will continue working on Pecan food safety research and antimicrobial treatments.

Impacts
What was accomplished under these goals? 1 - We optimized the UV-C light treatment to minimize food safety risks associated with surface water used for irrigation.The waters were inoculated with a cocktail of generic E. coli (ATCC 23716, 25922, and 11775) and then treated with UV-C light (20-60 mJ/cm2). All tested doses of the UV-C treatment reduced the E. coli levels significantly (P< 0.05) in the water samples with the turbidity levels up to 23.32 NTU. The decrease in the turbidity from 23.32 to 10.93 NTU increased the level of reduction by more than 2.15 log most probable number (MPN)/100 mL). UV-C treatment effectively reduces the microbial load in agriculture water; however, the turbidity of water may significantly affect the disinfection efficacy. 2 - The effect of hot water pre-treatment of in-shell pecans on physicochemical properties, consumer acceptance and purchase intent of dehulled and roasted kernels was evaluated. In-shell pecans were first subjected to hot water at 70, 80 and 90ºC for 8.6, 6.6 and 4.6 min, respectively; and kernels were later dry roasted at 160ºC for 10 min. The physicochemical properties of hot water treated and untreated nuts before and after roasting were determined. Furthermore, consumer acceptance and purchase intent of the roasted kernels were determined. Hot water treatmentaloneand subsequent roasting had minimal effect on pecans' physicochemical properties. Consumers liked (P<0.05) color and aroma of treated pecans. No effect (P>0.05) of pre-treatment was observed on the acceptability of other sensory attributes. Safety claim increased treated pecans' overall liking; however, it decreased purchase intent. Hot water treatment showed promise as a post-harvest microbial intervention strategy without affecting the physicochemical properties and consumer acceptability. 3 - We investigated UV-C light inactivation of Escherichia coli O157: H7 and Listeria monocytogenes on the surface of organic apples, pears, strawberries, red raspberries, and cantaloupes. Our results demonstrate that bacterial pathogens on fruit surfaces respond differently to UV-C light exposure. Inactivation rates were higher for less hydrophobic fruits with smoother surfaces (apples and pears) as compared to fruits with rougher surfaces (cantaloupe, strawberry, and raspberry). Findings indicate that UV-C light can effectively reduce E. coli O157: H7 and L. monocytogenes populations on fruit and berry surfaces. However, surface characteristics influence the efficacy of UV-C light.

Publications

• Type: Journal Articles Status: Published Year Published: 2019 Citation: Chhetri, V. S., Janes, M. King, J. M., Doerrler, W. T., and Adhikari, A. 2019. Effect of residual chlorine and organic acids on survival and attachment of Escherichia coli O157: H7 and Listeria monocytogenes on spinach leaves during storage. LWT - Food Science and Technology. 105:298-305. https://doi.org/10.1016/j.lwt.2019.02.019
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Kharel, K., Prinyawiwatkul, W., Yemmireddy, V. K., Graham, C. J. and Adhikari, A. 2019. Effect of hot water treatment of in-shell pecans on physicochemical properties and consumer acceptability of roasted pecan kernels. Int J Food Sci Technol. doi:10.1111/ijfs.14096
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Chhetri, V. S., Fontenot, K. Strahan, R. Yemmireddy, V., Cason, C., Kharel, K., and Adhikari, A. 2019. Attachment strength and on-farm die-off rate of Escherichia coli on watermelon surfaces. PLOS ONE. doi.org/10.1371/journal.pone.0210115
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Nguyen, T., Adhikari, A. Bhattacharya, D., Chhetri V. S., and Kharel, K. 2019. Microbial food safety risks associated with fresh and thawed catfish fillets during refrigerated storage. Food and Nutritional Sciences. 9:1261-1272.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Adhikari, A. Debanjana, B. Chhetri, V., and Carson C. 2019. Efficacy of aqueous chlorine dioxide and ozone water in controlling the growth of Listeria monocytogenes during sprouting of alfalfa seeds. Letters in Applied microbiology. doi.org/10.1111/lam.13209

Progress 10/01/17 to 09/30/18

Outputs
Target Audience:Growers, Food Processors, Extension agents, Scientists, Undergraduate, and graduate students, farmers market organizations, Louisiana Sweet Potato Association, Louisiana Fruits and Vegetable Growers Association, Louisiana Pecan Growers Association Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Graduate and undergraduate students received hands-on experience in produce food safety and microbiological techniques How have the results been disseminated to communities of interest?Several Good Agricultural Practices and Good Handling Practices workshops, Food Safety Modernization Act (FSMA) training and other on-farm food safety training were hosted to disseminate the results to growers and producers. Results were also presented during the Tri-State pecan growers meeting. What do you plan to do during the next reporting period to accomplish the goals?We will continue working on the Pecan food safety research and bacterial attachments.

Impacts
What was accomplished under these goals? We evaluated the efficacy of ultraviolet (UV-C) light on pathogen risk reduction in surface water used for irrigation of cantaloupe in an agricultural setting. The pecan food safety study was performed to investigatethe feasibilityof using hot water treatment as a kill-step for food-borne pathogens during pecan shelling. In-shell pecans were subjected to hot water at 70, 80 or 90°C for 1, 2, 3, 4 or 5 minutes. The time-temperature treatments to achieve a 5-log reduction ofSalmonellaenterica,Escherichia coliO157:H7,Listeria monocytogenes,and non-pathogenicEnterococcusfaeciumwere determined. Thermal death values were determined for each tested condition.L. monocytogeneswas most susceptible to heat treatment and were reduced by 4.6±0.35 log CFU/g at 70°C for 5 min, while 3 to 5 min at 80 and 90ºC treatmentswasrequired to achieve a similar reduction level forS.enterica,E. coliO157:H7, andE.faecium.S.entericawere most resistant and required 4 min treatment time to achieve a 5-log reduction at 80 and 90°C. The D-values ranged from 1.15 to 1.72, 0.83 to 1.19, and 0.41 to 0.92 min at 70, 80 and 90?C, respectively.E.faeciumhad the highest D-value (1.72 min at 70oC), indicating a potential surrogate for process validation for pecan industries. Utilizing proper hot water treatment during pecan shelling could reduce food safety risk.

Publications

• Type: Journal Articles Status: Published Year Published: 2018 Citation: Chhetri, V. S., Fontenot, K. Strahan, R. Yemmireddy, V., Estrada, K. P. and Adhikari, A. 2018. Effect of surrounding vegetation on microbial survival or die?off on watermelon surface in an agriculture setting. Doi.org/10.1111/jfs.12520
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Kharel, K. Yemmireddy, V., Graham, C., Prinyawiwatkul, W., and Adhikari A. 2018. Hot water treatment as a kill-step to inactivate Escherichia coli O157:H7, Salmonella enterica, Listeria monocytogenes and Enterococcus faecium on in-shell pecansLWT 97:555-560. doi.org/10.1016/j.lwt.2018.07.048

Progress 10/01/16 to 09/30/17

Outputs
Target Audience:Growers, Food Processors, Extension Agents, Scientists, Undergraduate and graduate students, Farmers market organizations, Young farmers, Louisiana Sweet Potato Association, Louisiana Fruits and Vegetable Growers Association, Louisiana Pecan Growers Association, Food hubs, School garden instructors Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Graduate and undergraduate students received hands-on experience in produce food safety and microbiological techniques How have the results been disseminated to communities of interest?Several Good Agricultural Practices and Good Handling Practices workshop, Produce Safety Alliance Growers Trainings and other on-farm food safety trainings were hosted to disseminate the results to the growers and producers What do you plan to do during the next reporting period to accomplish the goals?Our study indicated pecans may have bioactive compounds with antimicrobial properties. We will be workon extracting bioactive compounds from several varieties of pecans and will evaluate their antimicrobial properties.

Impacts
What was accomplished under these goals? This research project identified the time and temperature parameters for hot water treatment during pecan processing that can be regarded as a kill step and evaluated the effect of the treatment on physicochemical properties, consumer acceptance and purchase intent of dehulled and roasted pecans. The optimum times (1 to 5 min) and temperature (70, 80, and 90 ºC) treatment conditions to achieve a 5-log reduction of Salmonella enterica, E. coli O157:H7 and Listeria monocytogenes as well as non-pathogenic Enterococcus faecium were studied. The D-value of organisms showed that Salmonella and Listeria were the most and least resistant pathogens, respectively; and Enterococcus faecium was found to be the suitable surrogate for Salmonella enterica. As calculated from the D-value, hot water treatments for 8.6, 6.6 and 4.6 min at 70, 80 and 90°C respectively, were found to reduce the most heat resistant pathogen by 5 log CFU/g. In-shell species were then subjected to these treatments, shelled and roasted at 160°C for 10 mins. The effect of hot water treatment on the physicochemical properties such as % moisture content, water activity, color, and texture of the roasted pecans was determined. Sensory evaluation studies using 9-point hedonic scale were performed by serving the samples of roasted pecans to consumers (N=112). Hot water treatment had no significant effect on the moisture content, water activity, texture and color of shelled pecans. However, roasting decreased the moisture content (P<0.05), water activity (P<0.05) and hardness values (P>0.05). Hot water treated pecans became darker on roasting which was liked by consumers; pecan hot water treated at 90°C was the darkest with lowest L* value (P<0.05). Pecans hot water treated at 70°C for 8.6 min followed by roasting were most liked by the consumers. Thus, hot water conditioning of pecans is an effective method as it improves its microbial and sensory quality.

Publications

• Type: Theses/Dissertations Status: Accepted Year Published: 2017 Citation: Kharel, K., Karki, N., and Adhikari, A. Optimization of time and temperature of hot water treatment as a kill step to inactivate Salmonella spp and E. Coli O157:H7 in pecan processing. International Association of Food Protection Conference, 2017. Chhetri, V. S., and Adhikari, A. Effect of residual chlorine on the attachment and survival of E. coli O157:H7 on spinach surface. International Association of Food Protection Conference, 2017. Karki, N., K. Kharel, J. L. Cabezas, A. D. Arias, and Adhikari, A. Effectiveness of hot water and peroxyacetic acid treatment on inactivation of inoculated Salmonella spp. on alfalfa, clover and radish seeds intended for sprout production. International Association of Food Protection Conference, 2017. Chhetri, V. S., K. Fontenot, R. Strahan, R., K. Kharel, N. Karki, and Adhikari, A. Effect of Environmental Stress on Microbial Attachment and Die-Off Rate on Watermelon Surface in an Agricultural Setting. International Association of Food Protection Conference, 2017.

Progress 10/01/15 to 09/30/16

Outputs
Target Audience:Growers, Food Processors, Extension agents, Scientists, Undergraduate and graduate students, farmers market organizations, Louisiana Sweet Potato Association, Louisiana Fruits and Vegetable Growers Association, Louisiana Pecan Growers Association Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Graduate and undergraduate students received hands-on experience in produce food safety and microbiological techniques How have the results been disseminated to communities of interest?Several Good Agricultural Practices and Good Handling Practices workshops, Food Safety Modernization Act (FSMA) trainings and other on-farm food safety trainings were hosted to disseminate the results to growers and producers. What do you plan to do during the next reporting period to accomplish the goals?We wiill continue working on the Pecan food safety research.

Impacts
What was accomplished under these goals? This research project evaluated the efficacy of ultraviolet (UV)-C light on pathogen risk reduction in surface water used for irrigation of cantaloupe in an agricultural setting. Different mixture levels of pond and well water (1000 L) (UV transmittance rate 53.74±2.12) collected in a tank were inoculated with a cocktail of generic E. coli (ATCC 23716, 25922, and 11775). The inoculated water (7.4 log most probable number, MPN 100 mL-1) was then treated with UV-C light delivered to the water samples at varying UV-C doses (10-20, 20-30, 30-40, 40-50, 50-60, 60-70, 80-90, 90-100, 120-130 mJ cm-2) using a PMD 150C1/4 (Hanovia LDT, SL1 4LA, Slough, UK). Significant reduction (P< 0.05) of generic E. coli (>3 log MPN 100 mL-1) was achieved with lower doses of UV-C light (10-20 mJ cm-2) and below the detectable limit of the test for UV-C doses above 50-60 mJ cm-2. Replicated cantaloupe plots (12 plots, 3 plots/treatment, plot size 1.5 x 3 m, 5 plants/plot and 10 plants/plot for the first and second plating, respectively) were irrigated (spray or drip irrigation) with UV-C light-treated or non-treated water. The generic E. coli counts on cantaloupe irrigated with UV-C light-treated or non-treated water were not significantly different. Cantaloupe harvested from drip-irrigated plots were significantly lower in counts (1.83 ± 0.27, and 3.20 ± 0.24 log MPN cantaloupe-1 for the first and second plating, respectively) as compared with sprinkle-irrigated plots (3.57 ± 0.27, and 5.01 ± 0.29 log MPN cantaloupe-1 for the first and second plating, respectively). Our results indicated UV-C light is an effective antimicrobial treatment for microbial risk reduction of surface irrigation water, but influence on generic E. coli levels on cantaloupe surfaces was unclear. We are currently working on identifying the time and temperature parameters for hot water treatment during pecan processing that can be regarded as a kill step.

Publications

• Type: Conference Papers and Presentations Status: Accepted Year Published: 2016 Citation: Parraga K.,Janes, M., Fontenot, K., Williams, R., Chhetri, V., Carmoa, T., Beaulieuc, J., Adhikari, A. 2016. Evaluation of Ultraviolet (UV-C) Light Treatment for Microbial Food Safety Risk Reduction Associated with Surface Water Irrigation Sources. Abstracts. International Association of Food Protection Conference

Progress 09/16/15 to 09/30/15

Outputs
Target Audience:A study on evaluating the efficacy of UV-C light treatment on reducing food safety risk associated with irrigation water was performed. The results wereshared with growers, processors and extension agents through on-farm visits, workshops and trainings. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Graduate and undergraduate students received hands-on experience in good agricultural practices and microbiological techniques How have the results been disseminated to communities of interest?The results has been desseminated to growers and extension agents through the PI's GAPs/GHPs workshops, FSMA training and other on-farm food safety trainings and field visits What do you plan to do during the next reporting period to accomplish the goals?We will dosome laboratory studiesto examine the effect of UV-C light treatment on bacterial pathogens. We will also start the pecan food safety research during the next reporting period.

Impacts
What was accomplished under these goals? This work evaluated the efficacy of ultraviolet (UV)-C light to reduce generic E. coli from pond water used to irrigate cantaloupes. Replicated cantaloupe plots (3 per treatment, plot size 5'x10', 6 plants in each plot) were irrigated (spray or drip irrigation) with UVC light treated or non-treated water. Water and cantaloupe samples were quantified for generic E. coli using the US-EPA Approved Quanti Tray 2000 Colilert system and spread plated in VRBA. A mixture of pond and well water (1000 L) collected in a tank was inoculated with a cocktail of generic E. coli (ATCC 23716, 25922 and 11775) to a final population of 5.8 Log MPN/ml. The inoculated water was then treated with UV-C light by passing through a UV-C treatment unit PMD50C1/4 of doses ranges from 16 to 120 mJ/cm2. The different doses 16, 24, 33, 45, 57, 60, 86, 96 and 120 mJ/cm2 reduced the generic E. coli population by 2.9, 3.9, 2.9, 3.3, 4.9 log MPN/ml, respectively, and below the detectable limit for doses above 60mJ/cm2. Based on the preliminary experiment, thedose 57-67mJ/cm2 was selected to treat irrigation water which reduced the generic E. coli level by 4.2 log MPN/ml. Following three days of irrigation, cantaloupe plants were harvested for three daysat 24 hour intervals. No difference in generic E. coli was observed between cantaloupes irrigated with UV treated (sprinkle: 2.65, Drip: 2.97 log MPN/ml) or non-UV treated (Sprinkle: 2.84, Drip: 3.54) water. Generic E. coli population on the cantaloupe remained almost the same, ranging from 2.46 to 3.54 Log MPN/ml from 24 -72 hours after last day of irrigation. The results from this study indicate UV-C light as an effective antimicrobial treatment for pathogen risk reduction from surface irrigation water. However, cross contamination during irrigation may influence the microbial level on the produce.

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