Does your refrigerator smell bad? Whenever that happens, have you ever considered throwing in a few pieces of orange peels to combat the smell?
We all know that orange peels work like magic and will also leave behind its fragrant citrus scent. Now, have you ever wonder about the secret behind the magic?
Citrus peels are the skins of fruits such as orange, pomelo, lime and grapefruit. Each giving off its unique and subtle fragrances. In fact, the outer layer of a citrus fruit is known to contain natural oil consisting of many volatile chemical compounds.
We looked into these volatile chemical compounds in the peels of orange, pomelo, grapefruit, lime and hyuganatsu. The zest of the 5 individual citrus fruit were grated and analysed with headspace GC-MS. Gas Chromatography (GC) is a separation technique used for the separation of volatile compounds in the vapor phase while Mass Spectrometry (MS) is an analytical technique that ionizes and fragment chemical species. We identified the volatile chemical compounds in all of the five citrus fruits effortlessly with SmartDalton and MoleculeDB software. Through the usage of these two software, many volatile chemical compounds were found.
We found that limonene was present in the highest concentration as compared to other volatile chemical compounds across the five types of citrus fruits. Limonene is classified as a cyclic monoterpene and is a volatile compound that makes up for at least 79% across the five different citrus fruit samples. Pomelo has the highest limonene content of 92%, followed by lime, grapefruit, orange and hyuganatsu. Limonene is commonly used as a fragrance and flavoring ingredient and is known to give off a lemon, minty and orange odor. It demonstrates anti-cancer properties, relieve heartburn and reduce stress, anxiety and depression. Not only that, limonene also have many other great benefits. Therefore, limonene is commonly used in aromatherapy and orally taken in the form of soft gel capsules.
Hexanal is another compound that is identified across all five samples. The odor description of hexanal is fruity and clean with a woody nuance. Orange has the highest hexanal content of 0.23%, followed by grapefruit, hyuganatsu, lime and pomelo. Another compound identified is linalool.
Linalool has a floral odor type. Hyuganatsu is found to contain the highest linalool content of 0.44%, followed by orange, lime, grapefruit and pomelo. The chemical compounds identified in trace amounts are the cause behind the different scent given off by the citrus fruit.
Now that we have a better idea of the volatile chemical compounds in citrus fruits, perhaps pomelo peels would be a good solution to get rid of bad smells in your refrigerator. Instead of disposing the peels of the citrus fruit that you consume, there is an endless possibility for the usage of citrus fruit peels. When you consume oranges, limes, grapefruits or any other citrus fruits, you can easily turn it into cheap, magical and natural freshener!
Written by: Lynn Tay, Intern (Singapore Polytechnic), Aug 2018