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Authenticity Testing-Next Generation Sequencing (NGS)

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The Prof

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Posted 10 December 2021 - 03:03 PM



I would like to share some experiences regarding authenticity testing.


1. Having identified some 'high risk' raw materials following vulnerability assessment, we have been testing 'high risk' raw materials using NGS. The test results we have received have at times been either difficult to interpret, or invalid because the NGS test did not work and there was no 'result'. For example, ground cloves and smoked garlic powder could not be tested using NGS.

2. When the NGS test result highlights a contaminant, e.g. a) field bindweed in dried oregano, b) cumin and cow pea reported in allspice, c) fennel and cardamom reported in ground cinnamon; we report this to the supplier but they either challenge the method as being valid, and/or state that these contaminant's grow alongside the main crop and are therefore known contaminants, yet this is not stated in the raw material specification.

3. We use reference standards to check consignments of whole seeds, e.g. mustard seeds. This has been working well.


I would value your thoughts on this approach.


Question 1: What 'low-cost' methods do you use to verify raw material authenticity?

Question 2: How do you respond when a contaminant is detected?

Question 3: What actions are taken by your suppliers when a contaminant is detected?




The Prof



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Posted 10 December 2021 - 03:49 PM

What are you trying to achieve here?


I would note that agricultural commodities will ALWAYS have contamination...........drive by any field of soybeans and you will see random single corn stalks growing.....do they drive around that corn? No, it gets harvested and mixed in with the soybeans


IMHO, you need to give "contamination" a framework as your asking products that grow in the ground to contain zero contaminates (which is not a reasonable expectation) and this may be part of why your getting such pushback from your vendor




Is the lab your using follow a certified method in a certified lab to prove identity?  If not, you should be, then you have a leg to stand on re: authenticity


If you expect the COA to contain every known possible "contaminate" you'll end up with zero vendors to chose from


Farming is dirty work and mother nature is ultimately in charge

Please stop referring to me as Sir/sirs

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Posted 10 December 2021 - 04:28 PM

I'd suggest having a good chat with your lab's manager, and probably with some of the alternatives, to understand exactly what they can offer for your raw material types, what the limitations and strengths are for the methods, and whether they can suggest follow-up testing to understand the scale of contamination / adulteration where applicable.

As Scampi noted, for some commodities you're always going to get some degree of presence of other things, and modern analytical methods are very sensitive so potentially will detect these.

Your suppliers might be willing to amend their specs to mention known potential "contaminant" materials, or they may well have a position statement or similar on them, either of their own or from an industry body.


As for "low-cost" testing options, this isn't always something that exists, so you may need to explore other potential avenues for verification. I have materials for which the only useful analytical approach to authenticity starts at about £500 per sample, and if this finds anything requiring further investigation then the follow-up is over £2000 per sample. Testing every batch of this would make me very unpopular with people who need to worry about boring things like money and profit margins ;)


In terms of response in the event of a failure / positive detection of a potential adulterant, my process very much depends on exactly what has been found. Except for the methods that give quantitative results in a format that I can useful interpret, my first action is always to call the lab and have a chat with them first. I might be able to get some "off the record" (non-accredited...) interpretation, or agree sensible options to follow up with further more targeted analysis.

If I can't make useful semi-quantitive inferences from the results, that have validity in the context of the material, then I'm unlikely to raise it with the supplier beyond a cursory "we've found this and we're looking into it, so please provide your initial comments" type of thing.

The response varies widely, from the good suppliers who give intelligent and reasoned feedback, through to those who have outright denied anything is wrong even when presented with solid evidence that the product they've shipped has been grossly adulterated to the extent that circa 50% of the material is the adulterant rather than the intended product.

N.B. You get bonus points if they change story part-way through the investigation, from "nothing wrong" to "we accidentally shipped you a different product", only to then send you an even more heavily adulterated product when you agree to take one more trial order for some development work, presumably not expecting you to test it despite having just sent back the previous material... (yes, I've seen this happen)


If you're able to then talk to a contact at the supplier by telephone first - it makes it much easier to come across as a collaborative enquiry rather than an accusation, as you never know quite how someone is going to read the tone of an email. Sometimes you'll get to talk to someone who is extremely knowledgeable and come away feeling more reassured about the supplier and the material, and be in a better place to look at monitoring the authenticity of that type of product. Other times that won't happen, and you'll end up in an acrimonious exchange of solicitors' letters about who owes what to whom and when, but it's usually worth a try IMO. 

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Posted 13 December 2021 - 01:47 PM



Sorry if I'm a bit late to the party, but just wanted to add something about NGS which, as a lab technical person I talk about quite a lot. The process is generally very good when the question is "What DNA is present in my sample?" as long as the quality of DNA is acceptable. DNA extraction techniques generally need to b modified for spices, which still gives no guarantee that the DNA will be recognisable to the NGS system. Because this outcome is only know at the end of the test, and the platform is very expensive to run (hence the high cost and long turnarounds), customers are invoiced for a "Unable to provide result" outcome. 

Your seeds will generally have minimal processing, and are the home of the DNA in the organism and so it makes sense that you're having no issue with these.

In terms of weeds cropping up on the results, it would really depend where in the results they appear and what had happened to the sample during its production. You'd expect the commodity you're looking for to be top of the list and then weeds to be below this. I'd generally only get excited if a known adulterant was on the list and not explainable. You wouldn't reject flour as non-vegan for containing flour mite DNA, and so it's impractical for crops to be 100% free of weeds for the same reason. The concern with interprteing results again goes back to the quality of the DNA. If a spice is dried and ground then stored with something with "fresher" DNA and this contaminates the sample then this fresher DNA could amplify much faster, drowning out the expected DNA into 2nd place. 

This is why I always discuss unexpected results with our manufacturers - we don't do the test but before we outsource it I make sure everyone is on the same page.

Wherever possible, ask the question "Is there x in my sample?" and if a test is available, do that - eg. Peanut in garlic etc. If you're going to use NGS then make sure you've got someone to sense check the results with and stop doing NGS on samples which are proven to not have high enough quality DNA.

There is a new method coming out of Ireland which can help with spices - I'm not sure if I'm allowed to mention it here for commercial reasons but if interested please get in touch.


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