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Fun with fluorescence in olive oil (2012)
- atoav 3y agoOils generally can have funny properties, like dichromatism in pumpkin-seed oil (small layers are perceived green, thicker layers red)
- HPsquared 3y agoSimilarly, yellow food colouring looks red when concentrated. Also water looks blue but deep underwater there's no blue light left. Beer's Law
- dylan604 3y agoThere's a yellow mica pigment that when used in soap making it turns a very reddish-orange (almost like rust) until the saponification has completed and then returns to yellow. It is very disheartening the first time you see it and start to think how your batch of soap is going to not be what you hoped, and then 24 hours later it looks exactly how you hoped.
- kshacker 3y agoAs someone who has used only white soap for decades, so quite ignorant, could you provide a name?
- dylan604 3y agoOf the mica? There's probably others, but I have direct experience with Lemon Cupcake from Mad Micas https://www.madmicas.com/products/lemon-cupcake-mica?_pos=5&_fid=aa4176fbd&_ss=c https://www.madmicas.com/products/lemon-cupcake-mica?_pos=5&...
- HPsquared 3y agoI wonder if that has something to do with the pH.
- dylan604 3y agoThat would be my guess as well. After thinking about this further, I do remember as a kid using the kits for dying eggs for easter (somewhat belated topic) that required vinegar instead of water. The yellow dye would also appear orange until it dried as yellow. So, yeah, I'm leaning towards the pH as to the cause, but we still don't know the reason. I'm going to deliberately NOT go down that rabbit hole...* "An acid-base indicator is an organic compound that changes color with a change in pH. Methyl orange is a very common acid-base indicator, red in solutions that have pH values less than 3.2 and yellow in solutions with pH greater than 4.4. Indicators change color because the chromophoric system is changed by an acid base reaction (see below)." https://chem.libretexts.org/Ancillary_Materials/Laboratory_Experiments/Wet_Lab_Experiments/MIT_Labs/Lab_4%3A_Intro_to_Organic_Chemistry/Experiment_2%3A_Dyes_-_Methyl_Orange https://chem.libretexts.org/Ancillary_Materials/Laboratory_E... * I swear I tried really hard. Luckily, the hole wasn't too deep
- avsteele 3y agoA recall a number of news items from a few years ago which talked about how some olive oil vendors were adulterating their products with other oils. If this phenomenon could be better understood maybe there would be a rapid, optical/spectroscopic way to characterize olive oil purity.
- vixen99 3y agoYes, if only. I continually hear that much olive is not what it is supposed to be and it seems that authorities empowered to do something about this don't do much to stop it or perhaps they're fighting an uphill battle. In general the higher the price, the more likely the product is 100% genuine. The logic here might be that there's not that much profit in adulterating pricey oil selling rather limited quantities. For a technical delve into olive oil fluorescence: https://cdn.intechopen.com/pdfs/27027/InTech-Analysis_of_olive_oils_by_fluorescence_spectroscopy_methods_and_applications.pdf https://cdn.intechopen.com/pdfs/27027/InTech-Analysis_of_oli...
- kurthr 3y agoThe simpler, cheaper, and faster you make the test... the more quickly it will be defeated by the adulterators. Much like spam filters and SEO, leaking anything about how you defend against an attack just makes the attackers marginally improve their game. Simple amine/nitrogen tests for protein is how we got poisonous melamine in fake milk and wheat gluten killing babies, dogs, and cats. It comes down to Goodhart's law.
- canadiantim 3y agoThat’s not entirely true. The domain within which the cheating can occur shrinks by eg checking certain properties, tho the problem you’re talking about happens when only a few properties are checked because then of course only those properties need to be gamed/manipulated. It’s about how much coverage your tests have over the properties of what you’re testing
- lostlogin 3y agoI agree that the test becomes the target in many things, but how do you suggest applying that to food safety? If easy tests are out, you go to a very complex test immediately?
- robert_tweed 3y agoI don't have a green laser, but I just tried shining a 365nm UV torch on the various bottles of oil in my kitchen. My good EV olive oil in a glass bottle goes a sort of pinkish colour. With the natural colour of the oil & the way the glass reflects/refracts light, it makes it look like copper. I don't get the same effect with cheapo refined olive oil in a plastic bottle. I get a bit of fluorescence - the normal violet colour and much less than say a white piece of paper - but all or most of that is just from the container.
- detrites 3y agoInteresting. I wonder if this technique could be used as an olive oil purity/quality test of sorts? Maybe correlating a few samples of various kinds, along with some external form of verifiable testing, it may be possible to figure it out.
- robert_tweed 3y agoI'm definitely taking my UV torch to the supermarket next time. However, most good olive oils come in dark glass bottles, so I don't think it will be possible to check those. Might be interesting to look for variation among the cheaper EV ones. The article mentions differences between brands, but IDK if there's a specific correlation with quality other than that fake olive oils certainly won't turn red/pink.
- kjellsbells 3y agoI think your instinct is right: the dark glass is going to negate any test. I always assumed that products like olive oil sold in thick green bottles were sensitive to degradation by (UV, sun)light, so if that is true then by definition a casual in store test is not going to work. But perhaps green bottles mean nothing vis a vis light. I do recall that brown bottles were a thing in brewing to prevent beer from becoming funky by the action of light, but perhaps oils aren't susceptible to that.
- shirleyquirk 3y ago
- stared 3y agoQuinine is another fluorescent substance - it glows blue in UV light. I used to carry a UV diode into malls to test if tonics contained quinine.
- cialowicz 3y agoCurious, was this a hobby or did you work for the government tonic inspection bureau?
- lostlogin 3y agoWhat did you find? I believe most use a synthetic version. I’ve only had the natural one a few times and it was quite different, but the drink wasn’t as sweetened so that might have been the difference.
- Mistletoe 3y agohttps://academic.oup.com/jaoac/article/83/6/1435/5656401#198803296 https://academic.oup.com/jaoac/article/83/6/1435/5656401#198... > Fluorescence spectra of some common vegetable oils, including olive oil, olive residue oil, refined olive oil, corn oil, soybean oil, sunflower oil, and cotton oil, were examined in their natural state, with a wavelength of 360 nm used as excitation radiation. All oils studied, except extra virgin olive oil, exhibited a strong fluorescence band at 430–450 nm. Extra virgin olive oil gave a different by interesting fluorescence spectrum, composed of 3 bands: one low intensity doublet at 440 and 455 nm, one strong at 525 nm, and one of medium intensity at 681 nm. The band at 681 nm was identified as the chlorophyll band. The band at 525 nm was at least partly derived from vitamin E. The low intensity doublet at 440 and 455 nm correlated with the absorption intensity at 232 and 270 nm of olive oil. The measurements of these fluorescence spectra were quick (about 5 min) and easy and could possibly be used for authentification of virgin olive oil. From a Halloween website, may provide a clue to the red. > Chlorophyll is green under regular light, but will fluoresce red under a black light. Chlorophyll fluoresces red under UV light.
- ChrisMarshallNY 3y agoColavita EVOO turns fairly bright orange. I wonder if this could be a way to test for purity. I know that most EVOO is garbage.
- denton-scratch 3y ago> I know that most EVOO is garbage. I don't know about "garbage". What do you mean by "garbage"? Do you mean not from olives? Not extra-virgin? Or just not very nice? Where? Perhaps this is true in the USA? I'm in Europe, and I don't know anything about the US olive oil market. I do believe that a lot of EVOO isn't what it purports to be; for example, I believe a lot of purportedly Italian EVOO is cut with Spanish oil; but I can't substantiate that belief.
- ChrisMarshallNY 3y agoI’d have to find the video, but some outfit did a survey of all the various “extra-virgin olive oil” brands on US store shelves, and found that most (not “some” -most-) were crap. I think the issue was most were more like “pure” olive oil, with food coloring. Many of the pricey ones that come in small, expensive bottles, were not actually what any decent European would expect from the cheapest canned oil.
- yumraj 3y agoThere’s an old study by UC Davis also [0] [0] https://www.ucdavis.edu/news/imported-olive-oil-quality-unreliable-study-finds https://www.ucdavis.edu/news/imported-olive-oil-quality-unre...
- VLM 3y agoIts bad enough out there that the general public thinks the smell of hexane is what olive oil is supposed to smell like. Like you open a container of hexane in the chemistry lab and people say it smells like cooking oil. Um... not supposed to, no. Kind of like how younger people think tomatoes and strawberries are supposed to be flavorless and odorless.
- ProllyInfamous 3y agoOther fun household items which will fluoresce under UV light: Your feet (athlete's foot) and sometimes hands. Banana "mold" (the black spots' edges). Your credit cards and IDs (usually a bird on VISA and "AMEX" on so-named). Money (embedded denomination "strip" is different for each modern bill). Centipedes and Scorpions (seriously, just go into your yard at night and scan the ground for wigglies). If you have beehives, the Varroa Destructor (species/pest) also shines brightly on their little carapaces.
- dehrmann 3y agoI'd add turmeric.
- sdwr 3y agoTurmeric glows???
- littlestymaar 3y agoI'm surprised not to see tonic water in this list.
- ProllyInfamous 3y agoSomebody else had listed elsewhere — but I did leave off laundry detergent!
- jbottoms 3y agoThat should be: "...some detergents", that is, those detergents that have "brightners" added to them.
- echelon 3y agoThings that obviously fluoresce under normal visible light conditions can turn much more brilliant under visible laser light (eg. 532 nm green) Orange and green fluorescent dyes (such as on tennis balls), white clothes washed in detergent, etc.
- hultner 3y agoIs the article published free somewhere?
- throwawaaarrgh 3y agoFun EVOO facts: - the label of every bottle of EVOO uses short country codes to indicate where the oil came from, which is often multiple countries. this doesn't mean it's worse, but there are more ways some part of it could have not been great. - extra virgin olive oil is a juice that will go rancid from excessive light, oxygen, or temperature fluctuation. it's basically like red wine. once you open the bottle, use it quickly, and keep it in a dark dry place. make sure the bottle is glass and is darkened. - high phenolic olive oil is more expensive to produce (and thus buy) but contains more polyphenols. - more olive oils now carry seals of authenticity. find one, Google it, see if it looks legit. there are many different certifications. Italy was the country with the most EVOO fraud, so be more circumspect with oil from there. - a list of oils sold in America certified as pure: https://www.aboutoliveoil.org/79-certified-pure-and-authentic-olive-oils https://www.aboutoliveoil.org/79-certified-pure-and-authenti... - all EVOO is cold pressed and unrefined, by definition. ignore any marketing jargon you see on different bottles. - don't pay a bunch of money for infused oil. buy whatever oil you want, put some aromatics in a jar, pour in oil. use it up in a month.
- opheliate 3y agoBe very careful when infusing your own oil. Botulism is a real concern, it is often necessary to soak your aromatics in a citric acid solution before infusing.