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LuxeSci Show Notes: S1E4: Oranges

Hello again!  Welcome back to the LuxeSci Podcast, a podcast to re-ignite your wonder by exploring the intersection of science and luxury. I’m Dr. Lex, PhD, infectious disease expert, podcast host and lover of a good holiday tradition. This episode is one of 3 in a holiday series that i’ll be doing spanning December and into January.  It’s a festive time of year and that calls for festive topics.  For our fourth episode, I dug deep into a personal holiday tradition that has a special significance for me.  Growing up, and still, we celebrate the feast of St. Nicholas on December 6th every year.  St. Nicholas was a real bishop in the early Christian church and is still celebrated in several Christian denominations, including mine, Orthodox Christianity.  Nicholas was a bishop in Myra (now in Turkey) and was well known for his care of the poor.  One notable tale from his life includes him leaving gold coins to help a family in need and this translated into leaving gold coins in stockings that were hung by the fire.  In the Orthodox tradition, children leave their shoes out at night in hopes that St. Nicholas will visit them and leave little presents (and chocolate coins).  Every year, there was always an orange in my shoe for St. Nicholas day.  I often wondered why that was and it wasn’t until I was much older that I found out.  I interviewed my grandmother for a school project about what it was like living in New York City during the depression.  Among the stories she related was the sheer joy she and her brother experienced waking up to see an orange in their shoes for St. Nicholas day.  At the time, an orange was a truly extravagant purchase, such a tropical fruit in the heart of the tenements in NYC.  The oranges always showed up in our shoes as a reminder to cherish the simple things in life.  Our episode today is all about oranges as a reminder that luxury comes from anywhere, especially during this holiday season. 


Background:

  • Oranges

  • Turns out that the history of both the orange fruit and its name are quite fascinating

  • Sweet oranges (Citrus sinensis) are actually a hybrid of a mandarin and a pomelo (ancestor of a grapefruit)

  • Citrus aurantium is the bitter orange

  • Oranges originated from the Southern China, Northeast India, Myanmar region and the first record of a sweet orange was in Chinese literature in 314 BC

  • Sweet oranges are not a wild fruit and as i said above, there are a cross between a non-pure mandarin and a hybrid pomelo

  • Since many citrus fruits are infertile, there has been a lot of citrus crossbreeding over the centuries and so the taxonomy of these fruits is complex

  • Bitter oranges, by contrast, arose in the wild as a cross between a pure mandarin and a pomelo

  • In 2019 - 79 million tonnes of oranges were grown worldwide with Brazil being the biggest producer at 22%

  • The word for orange comes from the Sanskrit word for orange tree (naranga), which may sound familiar to people who speak Spanish

  • The English word comes from the Old French, orenge, which was based on the Arabic word naranj.

  • Interestingly, it’s believed that Portuguese merchants were the first to introduce the sweet orange to some of Europe and so the fruit is name after those merchants in the local languages, example, portokali, in Greek

  • I could go on about both the history of the origin and the derivations of the word in other languages but you’re here for the research

  • Research

  • OK everyone - super top secret scientist stuff I’m about to share here. I love a review article.  Review articles are where scientists look at all the literature for a particular corner of science and write an article that’s a review of that literature, putting it all together to define the landscape of scientific research in an area.  They are awesome!

  • So i found a review article about the chemistry and pharmacology of oranges.  Its from my now favorite Journal (Molecules!) and was written by JMJ Favela-Hernandez and team in 2016.

  • The review article is focused on Citrus sinensis - sweet oranges and the largest of the citrus groups grown around the world. 

  • Biologically - sweet orange trees are evergreen flowering trees with large spines on the branches (didn’t know that one) and anatomically, oranges consist of two distinct regions - the peel (called the pericarp) and the pulp with the juice sacs (endocarp)

  • Interestingly, the skin has an epicuticular wax that contains a large amount of aromatic oil glands - hence the particular orange smell and where orange oil extracts come from

  • Every part of the orange contains chemicals that have been implicated in positive health outcomes

  • Table 1 in this review has a great breakdown of the type of compound, where it was isolated geographically and the plant organ it originates from

  • Some examples of types of chemical compounds found in oranges are:

  • Flavonoids - polyphenols found in fruits and vegetables Poly (many) and phenols (aka carbolic acid, aromatic organic compound with 6 carbons, 5 hydrogrens and 1 OH group.  In the plants, flavonoids are involved in flower coloration (producing yellow and red flowers) but may have other jobs such as UV filtration or chemical messaging

  • Carbohydrates - sugars

  • Volatile compounds - VOCs are organic chemicals that have a high vapor pressure at room temp.  They are responsible for odors and scents (perfums and pollutants) and in the plants they act as signaling molecules and to attract pollinators

  • Specific ones such as hexane, chloroform, acetone from the peel

  • These may sound like scary chemicals but they are actually helpful in a variety of different ways (as my chemist friends are fond of saying “it’s all about the dose”, anything can be harmful or benign depending on the dose)

  • Effects - so let’s get into some of the effects of compounds found in oranges

  • Insecticidal - one interesting effect of oil extracted from the orange leaves is insecticidal activity.  This was tested against the Culex pipiens mosquito with two main compounds, terpineol and ⅛-cineole being the most effective offering protection from bites for around 2 hrs.  

  • Extracts of orange peels also showed potency against mosquitoes, houseflies and cockroaches

  • While some of the studies listed in this review found that control compounds were more potent than the orange extract for insecticides but this area of research has huge potential for providing alternative insecticide treatments for both home and agriculture.  The challenge with these treatment is usually potency ( how much of the compound is needed to see an effect).  Industrial insecticides are very concentrated so a little goes a long way and that’s not usually whats found in nature.

  • Antiparasitic - having been a parasitologist in a previous iteration of my career, the antiparasitic activity of orange extract.  In in vitro tests with Trypanosoma parasites, orange extracts showed weak antiparasitic activity, leading to parasite death in 3 min or 5 min depending on the parasite species.  THis was slower than the positive control, which lead to parasite death in 2 min.  This is an ongoing area of research but one that is very interesting given the toxicity associated with some of the current antiparasitic agents

  • Relaxant, sedative - and finally, one effect that may be of interest to all the insomniacs out there. First, exposure to the odor of essential oils of C. sinensis showed a relaxing and sedative impact in dental patients (woo hoo!) and in a study where 40 male volunteers were given different numbers of sweet orange oil to inhale then were submitted to a model of anxiety.  Those that has been exposed to the orange oil demonstrated no increase in anxiety such as increased heart rate.  So maybe if you can’t sleep or are feeling anxious, get some orange oil, just don’t go sniffing the oranges in the grocery store.

  • So let’s delve a little deeper into how scientists evaluate the compounds in oranges to see what they can do

  • In a 2019 study published in the Journal of Oxidative Medicine and Cellular Longevity

  • Remember back in a previous episode when we talked about what oxidation was (loss of electrons)

  • The authors of the paper took pasteurized juice from a Cara Cara orange and exposed C elegans worms to 10% cara cara juice or 10% regular orange juice in their culture media

  • The authors used techniques to look for the formation of radical oxygen species (to indicate antioxidant behavior), to see what RNA in the worms was differentially expressed with the different culture conditions (more genetic sequencing!) and more to see the impact of OJ on the worms

  • They found that cara cara OJ had more antioxidant activity in the worms and that this led to increased longevity in the worms.  While both OJs worked, cara cara was significantly better, likely due to more antioxidants (more red color) in the juice

  • So in this case - the scientists are using a model organism to find out potential mechanisms of action (or ways things work) for compounds.  Pretty cool, huh.  We can look in the lab to see how the world may work or to find new treatments

  • So now it’s time for section of something fun/environmental

  • So last episode I started talking a bit about the environmental impact of luxury items since environmental science is science

  • Leaving aside the potential environmental impact of the agricultural industry, let’s talk about food waste

  • The biggest producer of orange juice worldwide is Brazil, which exports 99% of its juice and then the US which consumes 90% of our juice

  • With this production come a high degree of waste of the by-products (peels, pulp, seeds, membranes, etc)

  • In Brazil 40-50% of the by products are discarded every year

  • This is a shame because, as we’ve learned, there are helpful chemicals in all parts of the orange

  • A group out of the State University of the Midwest in Brazll, let by Flavia Texeira, wanted to know if some of the by products of orange juice production could be put back into the food chain.

  • To do this, they put some peel back into jam.  They chose jam because it is what they call a high acceptance food (lots of people like it)

  • Fun fact - France has the highest production and consumption of jam, with 4 thousan tons of jam produced

  • According to our good friends at Bon Appetit, the main difference between jelly and jam is that jelly is made only with the fruit of the juice, while jam is made of chopped up pieces of the actual fruit

  • Back to the oranges - the researchers made orange jam with 0, 4, 8, or 12% orange peel added to the jam

  • They had 128 untrained jam consumers (seriously, are there trained jam consumers.  Where can i sign up for that job?) rate the different orange jams on appearance, aroma, taste, color, texture and overall acceptance using a nine point scale (1 - dislike to 9 - this is amazing).  They also rated their purchase intent on a 5 point scale (not going to buy it to would buy it right now)

  • Not surprisingly, the jam with the 12% orange peel faired the worst with the lowest scores in all categories.  OP8 was about the same as OP12 and OP0 and OP4 did the best for scores of texture and intent to purchase

  • Surprisingly, all the jams scored about the same on the acceptibiity index (~70)

  • The researchers put the different jams through a variety of tests to characterize both the physical properties (texture, color, adherence, moisture content, etc) and nutritional properties of the jams

  • They found that addition of the orange peel increased the nutritional content of the jams be adding proteins, lipids, dietary fiber, ascorbic acid, carotenoids, phenolic compounds and increasing the jams antioxidant capabilities. The added peel did decrease the carbohydrate and energy content of the jam and did lead to some off color and texture parameters

  • Their overall conclusions were that orange peel could be added to jam up to 8% and not negatively impact consumer acceptability and would increase the nutritional content of the jam and lead to some diversion of orange by products from juice production

  • Glossary

  • Flavonoids - polyphenols found in fruits and veggies - usually responsible for color

  • Volatile organic compounds - compounds responsible for odors and scents


Thanks for listening to this episode of LuxeSci.  A very special thank you to my audio engineer, Dimos.  Our theme music is Harlequin Moon by Burdy. If you have a correction, comment or suggestion for a topic, you can reach me at: drlex@luxesci.com.  We’re on Twitter and Instagram at luxescipod and our website is luxesci.podcastpage.io.  If you like us, please subscribe.   Please also leave us a review where ever you listen to podcasts.  See you again in 2 weeks!




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