What's Up With Stringy Avocados?

Experts explain why some avocados have little fibrous "strings" in the flesh while others are creamy and smooth.

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Avocados: They're packed with disease-fighting antioxidants, healthy fats, a long list of vitamins and minerals, and...strings? It often seems like there is about a 50% chance of finding fibrous little strings when slicing open a supermarket avocado.

Sometimes the flesh is a darker brown color, making the strings easy to identify. But other times they aren't clearly visible until you start making your avocado toast. While this is not a meal-ruining problem, strings or not, avocados are delicious and amazing and nutritional powerhouses. But for about $2 each, you likely prefer to buy ones that are creamy and smooth.

What Causes Stringiness on Avocados?

According to Mary Lu Arpaia, PhD, an extension subtropical horticulturist at the University of California, Riverside who works with the California Avocado Commission, these strings are actually the vascular bundles that bring nutrients and water into the fruit. The vascular bundles serve an important purpose: They are the internal "plumbing" within the tree and connect the fruit to the rest of the tree (yes, avocados are a fruit).

Arpaia explained that there are a few different reasons why some avocados develop more prominent vascular bundles, the first being simple genetics. "Some varieties just tend to be stringier than others," said Arpaia. "Hass generally is not stringy, but you do run into fruit that is [stringy] from this variety. On the other hand, Stuart, which is a rich, nutty-flavored variety, almost always is stringy."

Some Avocados Are Stringier Than Others

There may also be a "grower effect" when it comes to avocado texture. "Over the years, when we have done experiments with fruit from multiple growers, we have noted that some have 'stringier' fruit than others," said Arpaia.

And while there aren't any external signs that a particular avocado is going to be stringy (you have to cut it open to be 100% certain, Arpaia confirmed), fruit maturity (how long the fruit has been on the tree) and seasonality can play a role.

"Early-season fruit tends to be stringier than mid- or late-season fruit," said Arpaia. This means if you're buying California Hass avocados, if they are going to be stringy they'll most likely be stringy early in their season, which lasts from January until September.

Peruvian Hass avocados are in season from April until August, while Chilean avocados are from August until early spring. The seasonality of avocados from Mexico is a little more difficult to pinpoint, since trees in Michoacán flower several times per year, contributing to several annual "fruit seasons."

What Makes Avocados Creamier?

Although more research is needed to understand why avocado texture tends to become creamier later in the season, Arpaia said the ripening process may have something to do with it. "My guess is that as the fruit gets more mature, the enzymes responsible for ripening are more active, and this results in more cell wall breakdown, even to the strings," said Arpaia. "But this is just a guess with no evidence to support it."

It is possible that increased demand for the versatile fruit has contributed to more less-mature avocados or fruit from younger trees in circulation. "Avocados have gained so much attention and demand, for good reason," said Wendy Bazilian, DrPH, RD, author of "Eat Clean, Stay Lean." "Keeping up with this demand has likely created more plants, and more immature ones that are 'coming up' and maturing naturally."

"Theoretically, a younger fruit or tree may have lower nutrients in an area or two, potentially, but we don't really know for sure—and I would say that it would probably be a fairly insignificant difference at best," said Bazilian.

Nor will they change the way your favorite avocado dishes taste. "I know that strings can be a nuisance at times," said Arpaia. "But they should not influence the flavor of the fruit."

A Quick Review

Stringy or not, according to the US Department of Agriculture, one whole Hass avocado provides 20 grams of healthful fat; almost 3 grams of protein; and about 12 grams of carbohydrate with 9 grams as fiber (which is over 30% of the daily fiber target). One whole avocado also supplies 30% of the daily value for folate, 36% of vitamin K, 20% of vitamin C, 13% of vitamin E, 20% of potassium, and 10% of magnesium. Experts agree that, with or without the pesky strings, you'll benefit from the many health perks of avocados.

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