How to Keep Leftover Avocado or Guacamole from Browning

Forget all the other tips and gadgets, this simple tip is the best for keeping leftover avocado and guacamole from browning. The world of TikTok seems to agree, because the tip went viral!

How do you preserve that gorgeous green color of avocado or guacamole if you have leftovers?

I’ve mentioned this tip within various avocado-centric recipes over the years, and every time I see another guaranteed method (which too often doesn’t work or requires a purchase), I remind myself that I should make a little video of this technique, which seems to have flown under the radar.

Well, I finally made that video in my kitchen one night before dinner recently. I placed my phone on the edge of an upper cabinet to get an overhead view and have use of both hands. Then, I quickly demonstrated and explained the tip, and later posted the quick clip on TikTok.

At first, nobody saw the video. Literally, nobody.

I said to Emily that maybe we should delete it. Perhaps nobody cared about my clever tip, or more likely, we lacked any degree of TikTok savvy. “Did we choose the wrong hashtags,” I laughed?

Clearly we are TikTok novices! 

The next morning, Emily texted and said the video was taking off. I looked, and almost 20,000 people had seen it, many commenting that they were excited to try the tip. 

Over the following two days, we were shocked to see this little video go viral. When it hit 75,000, I figured the tip deserved its own spot on the blog. After all, I do have a Helpful Tips page for a reason!

So, what is the best way to keep leftover avocado or guacamole from browning? 

I should first mention, that the brown layer that develops is a result of oxidation (just like an apple browns) and is tasteless and harmless. So you can eat it, or merely scrape it away.

That said, it is nice to preserve that gorgeous color, and the following tip does just that. It’s a fun science experiment too. 

Simply cut a wedge of onion (red or yellow), and place it in a bowl and cover it with plastic wrap. An airtight container works too.

The same sulfur that makes our eyes water when we cut an onion will keep the avocado or guacamole bright green. It’s simple (and practical!) science.

FAQs and helpful hints:

• If using plastic wrap to cover a bowl, it need not be placed on the surface of the avocado or guacamole. You just need an airtight seal to keep the sulfur in.
• The leftover avocado will not taste like onion. I do like to use a glass or ceramic bowl or container, however, as some plastics do hold onto the onion aroma.
• Guacamole that includes chopped onion will still be susceptible to browning on the surface because the sulfur is mostly contained within the guac. A fresh onion wedge laid on top prior to storing will do the trick.
• Note that if an avocado or guacamole is already brown or otherwise past its prime, the onion will not make it green again.
• If you plan to let an avocado half or gauc sit in the fridge for several days, you can cut a thin sliver off the onion wedge (no need to use new onion) every day if you remember. The fresh cut will release more sulfur and help to further preserve the avocado. 

What do I do with the onion?

The onion doesn’t go to waste either. I refrigerate the remaining onion and use it in salads or in general cooking in the week ahead. I’ve actually found that I will use a tablespoon or two of minced onion (to perk up, say, a salad, a sandwich, or the aforementioned avocado toast) more readily when it’s peeled and at the ready. It’s also easy to chop it and sauté as a base for a variety of soups, stews, skillet dinners, and so on. 

And though we are told not to refrigerate onions, this recommendation applies to uncut onions. Once halved or sliced, onions will maintain freshness for about one week when stored in an airtight container. As mentioned, glass or ceramic is preferable, as plastic tends to absorb odor.  

You may also chop leftover onion and freeze it without blanching or cooking first. When needed in a recipe, like a soup or stew, you can add the onions to the pot directly from the freezer without thawing. 

How long will the onion keep the avocado or guacamole green? 

I’ve tested this trick for three days, at which point the guacamole was beginning to lose its vibrant green shade but was not brown yet. (My family was also tired of waiting to eat the guacamole!)

Most often I use the onion wedge to preserve the fresh color of half an avocado, as I often use that amount for breakfast or lunch, in a quick salad, on an egg scramble, or classic Avocado Toast (often topped with a piece of smoked salmon, a fried egg, or a combination of sliced tomato, cucumber, and a sprinkle of seeds). A few slices tucked into an Egg Taco is delicious too.

Following is some additional easy recipe inspiration. 

Favorite Avocado Recipes:

• Classic Guacamole
• Sweetgreen’s Guacamole Greens Salad (aka Guac Greens)
• Super Creamy Avocado Lime Sauce
• Easy One Avocado Guac
• Avocado Turkey Panini
• Easy Egg & Guacamole Breakfast Pizza (this recipe shows an early photo of “the tip!”) 
• Baked Egg Avocados
• Avocado Toast with Salmon and Turmeric Egg
• Spring & Summer Avocado Toast
• Avocado Tomato Salsa
• Honey Lime Shrimp with Avocado and Corn
• And don’t forget the many salads and bowl meals that benefit from the buttery flavor and creamy texture of avocado–and chili and skillet meals!