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Produce Safety Educators Call #35 - October 29, 2018 2-3 PM EDT

Total Attendees: 104
View webinar recording 
Topic: Postharvest Sanitizers for Fruits & Vegetables
Presenter: Dr. Amanda Deering, Clinical Assistant Professor, Department of Food Science, Purdue University; Ms. Donna Pahl Clements, PSA Southwest Extension Associate
Overview: Dr. Deering provided an overview of postharvest sanitizers, how they are regulated, what a sanitizer label should tell you, and how to measure appropriate concentrations.

Meeting Notes:

  • Purpose of sanitizing: goal to reduce microorganisms to a safe level and to ensure hygienic measures are used to produce safe food. 3-5 log reduction can be achieved with a good sanitizer (5 log is very optimistic).
  • A log reduction is when the population of bacteria is reduced by 90%.
  • If the water is not properly sanitized, bacteria (pathogenic and/or spoilage) can be transferred to other products = cross contamination. Sanitizers can help achieve longer shelf life. Buyers may require a sanitizer to be used, others may not.
  • Sanitizers are considered to be pesticides. A pesticide is any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest. Under United States law, a pesticide is also any substance or mixture of substances intended for use as a plant regulator, defoliant, or desiccant.
  • Pests are living organisms that occur where they are not wanted or that cause damage to crops, humans or other animals. Bacteria are among the list of pests.
  • Indiana started a list 4-5 years ago for sanitizers that can be used for postharvest processing of fruits and vegetables.
  • Postharvest sanitizers are considered a pesticide and regulated by the Environmental Protection Agency (EPA). EPA will review toxicity data and results from tests to show how well the product kills bacteria (and not us!) to determine if the product should be approved.
  • Postharvest sanitizers need to be EPA registered and approved in the state they are to be used. Check approval list annually for your state.
  • National Pesticide Information Retrieval System – free searchable database; fee for more access on particular sanitizer.
  • All products must have an EPA registration number on the label. This means the product should perform as stated on the label and not pose unreasonable hazards to your health IF used according to the label on the instructions.
  • Contact the manufacturer to determine if they do have an EPA number and request the number. Find product EPA numbers 
  • Other logos (USDA Certified Biobased Product; FDA GRAS Approved) do not replace EPA Registration number.
  • 30 compounds not registered; minimum risk pesticide – cannot bear a health claim; can only contain a single ingredient (such as essential oils). The product still needs to be registered for use in the state that it is being used. See slide 20 for minimum risk pesticides.
  • Label examples were provided during the call. Review slides 21-36.
    • EPA Registration Number breakdown
    • Search EPA website for more information on a product. May have more than one label.
    • Some products have the same EPA number so detail should be paid to the label and how the product can be used.
    • Always read directions before use – preparing, disposing, first aid, etc.
  • Product registration data is maintained on the National Pesticide Information Retrieval System (NPIRS)
  • Indiana has a list for approved sanitizers for the state.
  • The sanitizer concentration needs to be measured to ensure it is correct. Depending on the sanitizer used (such as chlorine) you may also need to measure pH.
  • Measuring Concentration – 3rd party auditors may question how the grower assures accurate concentration or ask to measure pH. Beware of limitations of certain test strips (e.g., make sure the right ppm range is used for the target ppm).

Questions & Answers

Question: There are expiration dates on strips used to monitor sanitizer concentrations. Are there any other things that growers should keep an eye out for?
Answer: Yes, expiration dates can impact accurate monitoring. It’s good to check these.

Question: A lot of farmers ask me if they should use chlorine products for contact surfaces and peroxyacetic acid sanitizers for the water in dunk tanks. Do you have research to indicate that it is better to use a chlorine product for contact surfaces?
Answer: No. I have not seen research that indicates this. Use the product according to its label.

Question: What is difference between Sanidate 12.0 than 5.0?
Answer: The concentration, 12.0 is higher. Also, in follow up, Donna shared that the labels are not the same.

Question: I’ve seen literature saying chlorine can at 3ppm in a dump tank and effective, others 50- 150ppm to be effective. Thoughts?
Answer: Higher concentration is typically better, but needs to be labeled as such. Also need to be careful of other effects to produce if concentrations are too high (such as product bleaching or chemical safety issues).

Question: How do we communicate about pH for certain products with growers if it’s not listed on the label? Is it not important to monitor?
Answer: If label doesn’t say it has to be at a certain pH, then you may not need to be as concerned with it being in a specific pH range. You may be wasting product though if it’s not working as efficiently because the water is not at the ideal pH. Best suggestion is to contact the manufacturer of the product.

Question: There is a need to discriminate between measurements of Free Chlorine vs Total Chlorine. Can you review the difference?
Answer: You want to measure free available chlorine since that is what is actually reducing the pathogens. Be sure to buy the correct test strips – there will be ones labeled for free and ones labeled for total.

Question: Do peroxyacetic acid sanitizers have generic test strips? My understanding is that they should be bought specific for the brand, whereas, chlorine products can use a generic test strip. Comments on this?
Answer: We have tested a number of those compared to titration kit. They’re all about the same. Make sure some have the appropriate ranges for the use or dilute down to the concentration of the test strip.

Question: Can you talk about microbial resistance when using chlorine products. Should growers rotate products occasionally?
Answer: Yes, is could be a concern. The fresh cut industry has been using chlorine forever. Some people are using chlorine in combination with other products.

Question: What do you say to farmers who believe sanitizers are bad because they will reduce the produce’s benefits to human intestinal biodiversity?
Answer: If they choose not to use a sanitizer for these reasons, they may need to find a buyer who will take it unwashed. There is value to sanitizer use for extending shelf-life and reducing spoilage organisms. That translates into more $ for growers.

Question: One PAA product, Shield Brite, says it can be used from 30-300 ppm on label, but FDA in 21 CFR Part 173.315 says PAA should not exceed 80 ppm in fruit and vegetable wash water. Do you know the reason for this difference?
Answer: Typically on food contact surfaces you can use a higher range – so check the label to see if that range is also for direct contact with produce. Not familiar with product. Could be for food contact surface or drains.

Follow up Question: Can PAA only be used up to 80 ppm as per 21 CFR 173.315?
Answer (after call): I pulled the label for Shield Brite and for sanitizing produce it says the following:

TREATMENT OF FRUIT AND VEGETABLE PROCESSING WATERS
Use Shield-Brite PAA 5.0 for the treatment of waters used in the processing of raw fruits and vegetables. Mix Shield-Brite PAA 5.0 with water either batch-wise or continuously at a rate of 59.1 to 209.5 fl. oz. of Shield-Brite PAA 5.0 solution to 1,000 gallons water. This will provide 462 to 1636 ppm of Shield-Brite PAA 5.0, or 24 to 85 ppm 100% peracetic acid in the use solution. The fruits and vegetables can be sprayed or submerged in the resulting solution for a minimum contact time of 45 seconds, followed by adequate draining. At this use dilution, Shield-Brite PAA 5.0 will control the growth of spoilage and decay causing non-public health organisms in process waters and on the surface of fresh cut or postharvest fruits and vegetables. This product is not intended for control of any public health organisms on fruit and vegetable surfaces. I would stick to 80 ppm PAA as that is typical concentration of most products that are labeled as fruit and vegetable postharvest washing. 

Question: I think I understood one of your slides to say that some essential oils are effective sanitizers. If yes, if a grower wants to use an essential oil, do you know where to find scientific research to back that up? Have you heard of a grower passing a GAP audit using an essential oil as their sanitizer?
Answer: I have not worked with any growers using essential oils as a sanitizer. These products would not have an EPA label. Not necessarily all good sanitizers, but there is some literature out there looking at combination treatments utilizing essential oils. These studies have shown some log reduction. If they are following the label accordingly, this should not present a problem.

Follow up: Rene Kittle provided an example of research that is on-going in this field: ALTERNATIVE POST-HARVEST WASHING SOLUTIONS TO ENHANCE THE MICROBIAL SAFETY AND QUALITY OF ORGANIC FRESH PRODUCE

Questions addressed after the call:

Question: What sanitizers should organic growers avoid?
Answer: Organic growers should check with their organic certifier for which products are approved for use. OMRI certification is listed on the PSA’s sanitizer spreadsheet, where it applies, but we encourage growers to always check with their organic certifier first before starting to use any sanitizer product.

Question: If sanitizer is used effectively at the correct concentration, what does that mean for infiltration risk? Is infiltration less of a concern? Is there a concern with infiltration of sanitizers alone, aside from microorganisms?
Answer: If sanitizers are used that will help reduce the bacteria that could be present in the wash water, so it would be less likely to have bacteria present if everything is done correctly. However, the extent of infiltration will depend on the temperature difference between the produce and the water with a greater difference increasing the likelihood that infiltration could take place.
Comment: Third-party auditors have down scored for not having PAA test strips from the chemical manufacturer. They may all work universally, but auditors do not treat them that way.

Question: Are growers being asked to simply use a sanitizer, or to use a sanitizer that provides 'x’ logs of microbial reduction?
Answer: I am not aware of buyers requesting using a sanitizer to document a specific log reduction. Most sanitizers will advertise the log reduction they should get if used (such as 99.9% reduction of Listeria monocytogenes) so most will take those data into consideration when choosing their sanitizer. To my knowledge some buyers are only asking that a sanitizer being used and not that they achieve a specific log reduction.

Other resources shared after the call:

Review of PSA Resources related to Sanitizers – Donna Pahl Clements

Next Meeting –

Date: December 17, 2018 - 2PM Eastern
Topic: FSMA Produce Safety Rule Draft Guidance
Speakers: TBD
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