Avocados have become the subject of numerous memes and considerable frustration due to their tendency to brown almost immediately after slicing. This browning process, scientifically known as enzymatic browning, gradually alters the color of fruits and vegetables, ultimately impacting their quality. The primary culprit behind this browning is a reaction involving an enzyme called polyphenol oxidase (PPO) found in the avocado pulp. Enzymatic reactions can initiate during various stages, including harvesting, transportation, storage, and processing. However, the most common contributors to browning are mechanical and physical changes such as peeling, cutting, slicing, and dicing that inflict damage on the avocado tissues. Although the browning of avocados is a natural occurrence post-cutting, there are several strategies to slow down this process. In this article, we will outline six effective tips to help you preserve the vibrant green color of your avocados for a longer time.

1. Wrap or Store in an Airtight Container

When avocados are sliced open, the enzyme polyphenol oxidase (PPO) along with a specific group of antioxidants known as phenolic compounds present in the pulp become exposed to oxygen. This exposure triggers a series of reactions where phenols are transformed into pigment-forming compounds called quinones. As these quinones interact further, they produce various byproducts that lead to the characteristic brown pigment associated with oxidized avocados. Essentially, the enzymatic browning process is initiated only when PPO, phenolic compounds, and oxygen interact. This indicates that the browning can be effectively mitigated by minimizing oxygen contact with the cut surface of the avocado. Therefore, wrapping a halved avocado in plastic wrap or placing it in an airtight container can significantly limit oxygen exposure, thereby slowing down the browning process. However, it is important to note that once the avocado is removed from the airtight environment, the browning process can quickly resume upon re-exposure to oxygen.

2. Incorporate Lemon Juice

Since polyphenol oxidase (PPO) plays a significant role in regulating browning, it’s beneficial to also focus on other elements that can affect the activity of this enzyme. One effective method to prevent the browning of avocados is by adjusting the pH levels, alongside controlling oxygen exposure. PPO operates optimally at pH levels ranging from 6 to 7.5, but it becomes inactive at pH levels below 3. This indicates that the application of acidulants—substances that can reduce pH levels—can be a strategic approach to influence PPO’s activity. Among the various acidulants, citric and ascorbic acids, which are abundant in lemon juice, are particularly effective in lowering the pH of avocados. This reduction in pH subsequently decreases the enzymatic activity associated with browning, enhancing the preservation of their vibrant green color. Thus, a practical tip for maintaining the freshness of your cut avocado is to squeeze a bit of lemon juice over its surface before storing it. This simple act not only delays browning but also adds a delightful zesty flavor to your dish.

3. Storing with an Onion

Research indicates that onion extract can effectively prevent enzymatic browning by inhibiting the activity of polyphenol oxidase (PPO). This enzyme, which contains copper, can be hindered by the sulfur compounds found in onions, as these may interact with the copper at the enzyme's active site, thus reducing its function. Interestingly, compounds that include a sulfhydryl group have been shown to disrupt PPO-induced browning by as much as 33%. Consequently, if you store your cut avocado alongside a sliced onion, it may help to prevent browning without compromising the avocado's flavor. However, it is essential to ensure that the onion only contacts the skin of the avocado and does not touch the pulp.

4. Submerge in Coconut Water

A highly effective method to prevent your avocado from browning is by immersing it in coconut water. This technique not only minimizes exposure to oxygen but also takes advantage of the antioxidant properties found in coconut water, which appear to inhibit the enzymatic reactions responsible for browning (a process driven by polyphenol oxidase, or PPO). Nonetheless, it's essential to be cautious with the duration of submersion; leaving your avocado in coconut water for an extended period can lead to a loss of its desirable firmness, resulting in a mushy texture. This method is particularly beneficial when you need to store an avocado for just one night, ensuring it remains fresh and ready for your next culinary adventure.

5. Incorporate Pineapple Juice

Similar to lemon juice, applying pineapple juice on your avocado can significantly prevent it from oxidizing and turning brown. This phenomenon can be explained through two key mechanisms that highlight the effect of pineapple juice on polyphenol oxidase (PPO), the enzyme responsible for browning. Firstly, research indicates that pineapple juice functions similarly to sulfites, which are commonly utilized as anti-browning agents known for their ability to inhibit enzymatic browning. Secondly, the antioxidant properties of pineapple juice may also contribute to its ability to combat browning. Regardless of the exact mechanism, a light brushing of pineapple juice on the exposed flesh of your avocado can effectively delay the browning process and enhance its visual appeal.

6. Coat with Honey

Applying a delicate layer of honey to the surface of your sliced avocado can significantly help in preventing browning. This natural sweetener functions as a protective barrier, minimizing exposure to oxygen while simultaneously deactivating the polyphenol oxidase (PPO) enzyme responsible for the discoloration. Interestingly, there are two main theories explaining how honey influences PPO activity. The first suggests that, much like onions, the antioxidants found in honey may interact with the copper ions within the PPO active site, thereby hindering the enzyme's function. The second theory posits that small peptides, which are chains of amino acids present in honey, can diminish the levels of quinones—compounds that undergo several reactions, ultimately resulting in the formation of the unsightly brown pigment.

Is it Safe to Consume a Browned Avocado?

Enzymatic browning is a process that significantly impacts the quality of avocados, leading to a decline in both their nutritional value and sensory attributes. This phenomenon is a major contributor to economic losses experienced by food producers as well as the food-processing sector, creating challenges for stakeholders across the industry. Despite these issues, it's important to know that avocados remain safe for consumption even after they have turned brown. You can simply cut away the discolored surface, and the remaining flesh is usually still good to eat. This practice is common in various cultures, including Indian cuisine, where avocados (known as 'makhanphal') are often incorporated into dishes. However, caution is advised; if your avocado emits an unusual or off-putting smell, it may suggest microbial spoilage. In such cases, it's best to err on the side of safety and dispose of the fruit.

The Bottom Line

The browning of avocados is a natural yet often unwelcome occurrence that takes place once the fruit is sliced, primarily due to the action of an enzyme known as polyphenol oxidase (PPO). Even though this process is unavoidable, there are effective methods to slow it down and maintain the fruit's appealing look. Some simple strategies to inhibit the enzyme's activity and reduce avocado browning include wrapping the fruit securely, applying lemon (nimbu) or pineapple juice, or even storing it alongside an onion (pyaaz). While it is safe to consume avocados that have developed a brown hue, be aware that their flavor and texture may be compromised. Discard any that emit an unpleasant odor, as they may no longer be fresh.