Avocado Adventures: Extracting Fat Facts for Food Labels

The detectives are sitting enjoying the delicious cheese Nancy bought from their last client, for whom she helped set up an on-line NIR system. “These are delicious,” says Cornlumbo as he fills his plate for the third time.

“What can you tell me about Guacamole?” asks Holmes. “Ah, that’s my favorite; I love whacking stuff with a big hammer,” says Cornlumbo. “With a hammer? That’s a bit extreme,” says Nancy Beef. “Of course, with a hammer; what else can you whack them with?” asks Cornlumbo. “With a fork, I squash them with a fork,” says Nancy. “A fork! You’d never be able to whack a high number with a fork,” exclaims Cornlumbo. “How many could you possibly need to whack?” asks Miss Mapple. “I average about 50, but my record is 76,” says Cornlumbo. “Wowzers! I knew you liked to eat Cornlumbo, but 76 avocados! That’s excessive; they have quite a high fat content, don’t you know,” says Miss Mapple. “Avocados, what are you on about?” asks Cornlumbo. “Guacamole, smashing avocados to make guacamole,” says Miss Mapple. “Oh, GUACAMOLE! I thought you said WHACK-A-MOLE!” says Cornlumbo to the amusement of the detectives, who fall about laughing.

“Now we’re all on the same page; I’d like to tell you about our latest case involving avocados and guacamole. As Miss Mapple correctly pointed out, avocados are high in fat, but hardly any other fruit provides so many important nutrients. They are an excellent source of healthy unsaturated fatty acids and numerous vitamins and minerals. What else can you tell me about avocados?” asks Holmes. “Testicles!” shouts Cornlumbo to a sea of confused faces. “I’m sorry, Cornlumbo, is that supposed to be helpful? Or have you developed Tourette’s?” says Holmes. “The word “avocado” comes from the Nahuatl word “āhuacatl,” which means testicle,” says Cornlumbo. “I knew there was a reason I didn’t like smashed avocado,” says Eggcule Poirot. “They are also sometimes called “alligator pear” because of their pear-like shape and rough, green skin that looks like alligator skin. Speaking of skin, avocado oil derived from the pulp is used in cosmetics for its ability to nourish the skin and even act as a natural sunblock. They’re fascinating really. An avocado tree can produce up to 500 fruits per year; in fact, botanically speaking, they are berries with a single large seed. It takes 5 to 13 years to produce berries when grown from seed, and they are climacteric, which means they mature on the tree but ripen once picked,” explains Cornlumbo.

Shallot Holmes is impressed with Cornlumbo’s knowledge of avocados and asks if he could help the client. Cornlumbo happily accepts and asks for the details of the case. “The client is based in Michoacán, Mexico, a state famous for its avocado production. They have started to produce their own guacamole but need to perform various analyses for labeling requirements in the US. The client is adamant that the analysis must be performed in the next few days,” says Holmes. “Cinco de Mayo,” says Cornlumbo. “Think-of-the-mayo,” are you purposefully trying to confuse us today, Cornlumbo?” asks Holmes. “It’s Spanish for the 5th of May. It’s a celebration of Mexico’s victory over the Second French Empire in 1862. It’s more popular in the United States than in Mexico and has become a celebration of Mexican-American culture. People celebrate Mexican cuisine and eat tons of avocados. I imagine that’s why the client is desperate to perform this analysis quickly; they want to meet the vast demand for guacamole caused by the Cinco de Mayo celebrations,” explains Cornlumbo. “Well, if that’s the case, there’s no time to waste; get thee to Mexico, post-haste!” says Holmes. “And you call me strange,” says Cornlumbo as he dashes out the door.

On arriving in Michoacán, Cornlumbo is greeted by the vibrant and somewhat frantic avocado producer Juanito Guacajete. Juanito wears a sizeable green poncho and has a large round belly. Cornlumbo chuckles as he realizes that Juanito resembles a large avocado. “Ah, Señor Cornlumbo, welcome to the avocado capital of the world!” Juanito exclaims, his hands motioning toward the endless groves of avocado trees. “We must hurry, amigo! The Cinco de Mayo is approaching, and we need your expertise to get our guacamole to the gringos pronto!”

Together, they drive to Juanito’s facility, a colorful building covered in murals of avocados wearing sombreros. They enter the bustling production area to a room filled with scientific equipment. “Here’s where the magic hasn’t been happening fast enough, Señor detective,” Juanito said, gesturing at an old fat extraction setup. Cornlumbo nods knowingly as he looks at the outdated equipment. “I can see you are performing Soxhlet extraction; the method is accurate, but the way you are performing it is very slow. What you need is a modern fat extractor. It also looks like your methods could be improved. For fat extraction, a representative and consistent sample is crucial. Tell me, Juanito, how do you homogenize your sample?” asks Cornlumbo. “Ah, we whack them with a big hammer, just like my abuela used to when she made guacamole,” says Juanito. “Hammers work great for whacking moles but not so good for guacamole,” says Cornlumbo to a confused-looking Juanito before explaining the importance of sample homogeneity and the steps involved in fat extraction using a speed extractor.

What are the steps involved in fat extraction?

Sample Preparation: The sample must be peeled, seeded, and homogenized by blending for 2 seconds in a laboratory blender. Ensuring a homogenous sample is crucial for accurate fat analysis, as any inconsistency can lead to errors in the fat content determination.
Drying & Mixing: 2.5 grams of homogenized avocado must then be mixed thoroughly with 15 grams of anhydrous sodium sulfate in a cellulose thimble to absorb the moisture and aid the drying process.
Speed Extraction: Unlike extraction using classical Soxhlet glassware, which can take hours, an automated Soxhlet extraction can significantly reduce the extraction time with more effective heating and adjustable cycle volumes. We place the dried avocado sample into a cellulose thimble. The fat is then “washed out” into the beaker by the solvent, in this case, petroleum ether.
Preservation & Stability: The extracted fats must be preserved accordingly until analysis to prevent oxidization and degradation. Avocado fats, being largely unsaturated, are susceptible to oxidation, which can affect the accuracy of the analysis if not handled under appropriate conditions. Post extraction, the beakers containing the fat extract are dried in an oven at 102ºC until a constant weight is achieved.
Calculation of Fat Content: Finally, the extract is dried and weighed, and the difference in the weight, before and after, gives the fat content. This is what will be displayed on your labels, which is essential for the U.S. market with its strict labeling laws.
Repeatability & Validation: The procedure can be validated by repeating the extraction in triplicate, confirming its reliability. A low standard deviation indicates high precision.
Hydrolysis: To speed up the process further, a comparison can be made between fat content determination with and without hydrolysis (acid treatment prior to extraction). The results of such a test suggest that hydrolysis is not necessary for avocados, as the fat content measured without this step is so close to the total fat content.

Juanito, awestruck by the accuracy, simplicity, and speed of the process, claps his hands together. “Señor Cornlumbo, you are truly the maestro of the food detectives and the savior of Cinco de Mayo!” Together, they watch as the extractor whirs into life. “Just doing my job, Señor Guacajete,” says Cornlumbo with a grin. “Let’s celebrate, Señor Cornlumbo; there’s a fun fair in town this week for the Cinco de Mayo celebrations; you want to go?” asks Juanito. “Amazing, grab your hammer; let’s go whack some moles!” says Cornlumbo. “You are one loco gringo, Señor Cornlumbo,” says Juanito as they head into town.