Mad about Science: Orange juice

By Brenden Bobby
Reader Staff

Before diving into today’s topic, I’d like to offer a sincere apology for my unexpected absence last week. Unafraid of exploring poop humor at my own expense, I will publicly admit that I suffered a bout of salmonella and was left essentially debilitated for the course of about three days. To paraphrase Monty Python, don’t worry, I got better. (And in case you’re wondering, this week’s subject and my recent bout of illness are unrelated.) 

Orange juice is a breakfast staple and a major source of vitamin C for many Americans. It has a sweet and tangy flavor that is immediately identifiable and is often paired with breakfast foods — but should it be?

A single glass of orange juice can contain 26 grams of sugar — comparable to a can of soda. Orange juice has a few more health benefits than soda, as it contains things like vitamin C and potassium, but the removal of fiber means your body doesn’t have to work as hard to absorb the sugar. This creates sharp blood sugar spikes, which isn’t something you want first thing in the morning. This can be offset by including fiber in the rest of your breakfast, such as whole-grain bread, waffles or pancakes, but it’s really just better to eat an orange than drink its juice.

All orange juice starts with the orange itself. Most commercially sold oranges in the U.S. are grown in California and Florida. Meanwhile, many oranges for juice are also imported from Mexico and Brazil.

Unlike many other fruit trees, oranges don’t like to freeze and need higher temperatures year-round to thrive. The consistent and high temperatures and water availability of those states make for an ideal environment for these citrus trees. Recently, however, Florida has lagged behind California in orange production due to a disease called citrus greening. This is a bacterial disease that is spread by Diaphorina citri, a sap-sucking insect from Asia that has invaded Florida orange plantations and wrought havoc on crops.

Combatting this invasive critter has proved challenging, with one of its only known predators being a parasitic wasp that can’t keep up with the sheer numbers in which D. citri reproduces. The tropical environments of Florida are likely more conducive to the lifecycle of D. citri than California, allowing the Golden State to gain an edge in Valencia orange production.

Most orange juice is produced by a mixture of two breeds of oranges: Valencia and Hamlin. Valencia oranges take between a year to 15 months to fully ripen for juice production, which can cause a delay in harvesting — something U.S. consumers are not keen on when it comes to a component of the breakfast ritual. Hamlin oranges take up to eight months to ripen, which can smooth the harvest curve and allow for more consistency at the cost of flavor.

It may surprise you to know that oranges picked for individual consumption and oranges picked for juicing aren’t harvested the same way. The piles of oranges you encounter at the grocery store are hand-picked — often by immigrant workers — and stored in a satchel the workers carry around their torso. 

The quantity needed for juicing is much greater than those that end up on display at your local grocer, so orchardists apply a specialized harvester that drives over the trees. The trees pass through a gap in the middle of the harvester, where a series of metal arms rattle and vibrate to knock fruit and leaves from the limbs onto a sorting conveyor that feeds into a secondary vehicle driving alongside the harvester. 

The harvester has the capability of collecting up to two tons of fruit per minute. The carrier vehicle will transfer its load to a semi trailer parked on the orchard. Larger orchards will often have multiple carrier vehicles swapping out between loading and unloading to maintain speed and efficiency so the harvester doesn’t have to stop collecting.

Each trailer can hold up to about 125,000 oranges and are parked in lots at the factory while they await processing. It’s common to see dozens of these trailers and millions of oranges awaiting their fate.

The oranges are machine washed with a water and alkaline solution and run through an automated brushing system to clean them ahead of sorting. Workers will individually sort through the flow of oranges to remove damaged or rotting oranges. The oranges are fed into a sorting machine that sorts each fruit by diameter ahead of the juicing machine. This allows precisely measured oranges to fit in just the right juicer without getting unwanted rind mixed into the juice.

Here is where the fun begins. The oranges are sorted into cups and sliced in half. Each half is then juiced by a cross-shaped head that spins, similar to a juicer you use at home. This guts the rind and harvests the juice and pulp for delicious OJ.

Do you like pulpy orange juice? The factory doesn’t split pulpy and non-pulpy batches. Instead, it harvests the pulp from the start of the process then reintroduces it to nearly finished batches. In all likelihood, the pulp in your orange juice isn’t from the same oranges used to make the juice you’re drinking.

Wondering where the rinds go? They’re fed through an augur and ground up to become cattle feed. Before that happens, the oil from the rinds is harvested and refined to be used in cosmetics, flood flavoring and soap.

The juice is pasteurized ahead of bottling. If your bottle says 100% orange juice, that means it was harvested, pasteurized and ended up on the grocery store shelf as-is. If it says “from concentrate,” then the bulk of the water content had been evaporated and water was reintroduced to frozen concentrate to create juice. This is less common in orange juice and more common in apple or cranberry juices.

Stay curious, 7B.