IMPROVING THE SAFETY OF HISPANIC STYLE FRESH CHEESES

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1013801
• Project Start Date: Oct 1, 2017
• Project End Date: Sep 30, 2022
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF ILLINOIS
2001 S. Lincoln Ave.
URBANA,IL 61801

Performing Department
Food Science & Human Nutrition

Non Technical Summary
Most cheese styles have not been associated with foodborne illness in the U.S. However, Hispanic-style fresh cheeses (HSFCs) present a unique problem as evidenced by their numerous Listeria monocytogenes outbreaks. Favorable growth conditions in Hispanic-style fresh cheeses like queso fresco (QF), including high moisture, low salt content, and near neutral pH, along with the ability of L. monocytogenes to grow under refrigeration, are primary factors contributing to increased L. monocytogenes-associated food safety risk. Todate, there are few L. monocytogenes control measures during the manufacturing of these types of cheese; as a consequence the contamination of cheese with L. monocytogenes is likely to affect consumers. As U.S. population demographics shift, the demand for these products has risen. Outbreaks of listeriosis from illicit production of queso fresco make headlinesand yet commercial QF production can also be a problem. In fact, 5 of the 12 listeriosis outbreaks reported to the CDC from 2009-2011 were linked to soft-cheeses, of those 4 were HSFCs; evidence HSFCs are the major risk among modern soft-cheese production. These outbreaks highlight the growing market for these products, but this has been met with hesitance to meet market demands by many manufacturers due to liability concerns. Strategies to make Hispanic-style fresh cheeses safer are needed to help meet market demand and prevent Listeria outbreaks.

Animal Health Component

100%

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	3430	1100	50%
712	4010	1100	50%

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

Subject Of Investigation
3430 - Cheese; 4010 - Bacteria;

Field Of Science
1100 - Bacteriology;

Keywords

food safety

foodborne illness

hispanic-style cheeses

listeria monocytogenes

Goals / Objectives
Objectives: The long term goal of this proposal is to improve the safety of HSFCs. To accomplish our goal, we will pursue the following objectives: 1. Screen novel combinations of antilisterials for effectiveness in our laboratory QF model. 2. Test effective combinations of antilisterials under home abuse situations. 3. Evaluate sensory implications of best antilisterial combinations.

Project Methods
We previously developed a lab-scale model for queso fresco (QF) that we will utilize for Objective 1 and 2. For Objective 1, we will mix combinations of antilisterials (bacteriocins, organic acids, etc.) into the making of the model QFs and quantify the Listeria monocytogenes population over four weeks of refrigerated storage. The combinations that work the best will be evaluated with Objective 2 where we will incubate QF at abuse temperatures such as 10 degrees C. At this temperature, we predict Listeria monocytogenes will grow much faster than at 4 degrees C (refrigeration) and will put greater stress on the antilisterials added to the QF. We will also evaluate consumer contamination by inoculating QF after 21 days of refrigeration followed by another week of incubation at 4 degrees C. Ideally, the antilisterials will still prevent L. monocytogenes growth which will demonstrate that the antilisterials are very stable in QF. For combinations of antilisterials that are effective, a sensory test will be performed to determine if the incorporation of antilisterials will impact consumer perception of the product (Objective 3). We will use a triangle test to determine if consumers can tell the difference between the untreated QF and QF that has antilisterials included at the doses determined in Objectives 1 and 2.

Progress 10/01/19 to 09/30/20

Outputs
Target Audience:These expected outcomes are significant, because they can be used to improve the ability of producers to incorporateeffective antilisterial additives into high-risk QF and thus enabling the QF industry to grow while meeting food-safetydemands. The primary target audience is the cheese industry. Changes/Problems:We are using a similar approach to evaluate antilisterials in a miniturized ham model. What opportunities for training and professional development has the project provided?Support of a student and provided research supplies to facilitate experiments. How have the results been disseminated to communities of interest?Poster at American Dairy Science Association at the 2020 annual meeting. What do you plan to do during the next reporting period to accomplish the goals?We will try novel combinations with PlyP100. For example, combine with holin and other pore forming compounds which might act synergistically with PlyP100.

Impacts
What was accomplished under these goals? Aim 1: We continue to make progress. We published a recent paper that looked at the effectiveness of various GRAS antilisterials in QF. We will continue testing for more useful treatments. Aim 2: Work is ongoing. The only combination that works great is nisin with PlyP100 (an endolysin). We continue to look for more useful combinations. Aim 3: We have evaluated some treatments which are moderately effective at listeria control and don't impact QF quality as perceived by consumers.

Publications

• Type: Journal Articles Status: Accepted Year Published: 2020 Citation: Martinez-Ramos, A.R., Ibarra-S�nchez, L.A., Amaya-Llano, S.L. and Miller, M.J. 2020. Evaluation of combination of nisin, lauric arginate, and -polylysine to control Listeria monocytogenes in queso fresco. Journal of Dairy Science. https://doi.org/10.3168/jds.2020-19001. (In Press).
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Ibarra-S�nchez, L.A., El-Haddad, N., Mahmoud, D., Miller, M.J. and Karam, L. 2020. Invited Review: Advances in nisin use for preservation of dairy products. Journal of Dairy Science, 103(3), 2041-2052. doi.org/10.3168/jds.2019-17498.

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

Outputs
Target Audience:These expected outcomes are significant, because they can be used to improve the ability of producers to incorporate effective antilisterial additives into high-risk QF and thus enabling the QF industry to grow while meeting food-safety demands. The primary target audience is the cheese industry. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?I have supported one graduate student with these funds. I have also used the funds to support the research needs of a few others that have contributed to the project. How have the results been disseminated to communities of interest?Poster was presented at the American Dairy Science Assoication meeting in 2019. What do you plan to do during the next reporting period to accomplish the goals?Finish publications related to Aim 1 ([1]: Limitations of nisin review; [2]: Nisin improvement via targeted modification; [3] Comparison of PlyP100 to other endolysins). Finish experiments related to Aim 2 and submit a publication. No plan for Aim 3 in next reporting year.

Impacts
What was accomplished under these goals? While most cheese styles have not been associated with foodborne illness in the U.S., Hispanic-style fresh cheeses (HSFCs) represent a continued risk for listeriosis. They have been linked to both historic and recent outbreaks. In fact, 4 of 26 listeriosis outbreaks listed in the CDC FOOD tool from 2011 to 2015 were linked to HSFCs, including 3 from pasteurized milk cheeses. In particular, Queso Fresco (QF) is the most widely produced and implicated HSFC in the U.S. Importantly, QF is known to support the growth of L. monocytogenes. Our long term goal is to improve the safety of HSFCs. Aim 1: In the last year, we have made significant progress in this area. Previously, we demonstrated thata combination of nisin and PlyP100 can eliminate L. monocytogenes in QF. In the last year, we have characterized the limitations in using nisin alone (JDS Review is in press) and have developed a strategy to improve the action of nisin in QF (publication in preparation). We are also evaluating the anti-listerial mechanism of PlyP100 so that we can potentially improve its activity. Aim 2: This work is ongoing and I can only make a broad conclusion. It is obvious with our current data that temperature is an important factor. Antilisterials that we have tested work much better at 4 C (standard refrigeration) than at 10 C (a common refrigeration abuse temperature). Aim 3: This work is ongoing and it is too early to state any conclusions.

Publications

• Type: Journal Articles Status: Accepted Year Published: 2019 Citation: Feng, Y., Ibarra-S�nchez, L.A., Luu, L., Miller, M.J. and Lee, Y. 2019. Co-assembly of nisin and zein in microfluidics for enhanced antilisterial activity in Queso Fresco. LWT  Food Science and Technology, 111, 355-362. doi:10.1016/j.lwt.2019.05.059; IF: 3.129.

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

Outputs
Target Audience:The primary target audience is the cheese industry. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?I have two graduate students that have worked on this project. In addition, I have had a visiting scholar work on this project as well. How have the results been disseminated to communities of interest?So far, we have focused on publications. I plan to engage more industry folks at future ADSA meetings. What do you plan to do during the next reporting period to accomplish the goals?As indicated above, we have a paper in preparation that evaluated several foodgrade antilisterials for activity in QF. We also tested the most promising treatments for sensory evaluation. In the coming year, we will continue to evaluate novel antimicrobials such as nisin encapsulation in order to meet our performance and cost requirements.

Impacts
What was accomplished under these goals? Objective 1. We have made significant progress with this objective. We have a recent paper plus we are working on another manuscript that will be submitted in Spring 2019. Objective 2: We have made some progress with this objective. We have attempted 4, 7 and 10 degrees celcius and found that our best antilisterials do not work well at these abuse temperatures. Objective 3: We plan to publish our first paper incorporating this objective in 2019.

Publications

• Type: Journal Articles Status: Accepted Year Published: 2018 Citation: Ibarra-Sánchez, L.A., Van Tassell, M.L. and Miller, M.J. 2018. Antimicrobial behavior of phage endolysin PlyP100 and its synergy with nisin to control Listeria monocytogenes in Queso Fresco. Food Microbiology.
• Type: Journal Articles Status: Accepted Year Published: 2018 Citation: Holle, M.J., Ibarra-Sanchez, L., Liu, X., Stasiewicz, M.J. and Miller, M. 2018. Microbial analysis of commercially available U.S. QF. Journal of Dairy Science.