Avocados are berries which have a pear shape. They may also be known as butter fruits or alligator pears due to the scaly or leathery appearance many varieties of avocados have. It is believed that avocados were first cultivated by humans around 8000 BC in South and Central America. Mexico is currently the largest producer of these fruits, with Brazil, the United States and Columbia following.

Many varieties of avocados begin a dark green color and turn black as they ripen. The flesh of the avocado is a yellowish-green, has a buttery consistency and a nutty flavor. Hass is a typically brown avocados. Fuerte avocados have a smoother dark green skin and are larger than the Hass. Zutano and Bacon varieties are also available, though they are less common.

Avocados contain several valuable nutrients such as vitamins A, B6, C, E and K. They also contain high amounts of calcium, copper, foliate, magnesium and potassium along with plenty of fiber. Avocados have a high fat content, with fat accounting for 70-80 percent of the calories of the fruit. However, as much as two thirds of this fat is mono-unsaturated, a type of fat that is beneficial to your overall health.

Can We Eat Brown Avocados?

If the avocado you have is not Hass, an avocado may turn brown because it has been handled harshly and has become bruised. This causes the inside and outside to take on a brownish hue. When you cut an avocado, this will expose the flesh to oxygen. As the flesh oxidizes, it will start to brown as well. If your avocado is slightly browned, you can still eat it, but the flavor may be bitterer than a fresher avocado would be. However, if your avocado's flesh has become very dark or the flesh has become stringy, you should avoid eating it, particularly if there is any sign of mold. Avocados have a very high fat content, so they oxidize and become rancid very quickly at room temperature and will need to be thrown away.

How to Keep Fresh Avocados from Turning Brown

In general, reducing the avocado's exposure to the air will help you keep it fresh for a longer period of time.

• Pit Method - People are often recommended to leave the pit in the avocado to keep the flesh from turning brown. Many will place the pit in a dish that contains avocado like guacamole to keep it from turning brown as well. In general, it is found that avocado flesh that remains in contact with the pit will stay green. It usually takes around 6 hours to become a brown avocado at room temperature because it hasn't been exposed to much oxygen yet. So, in most cases, covering your dip with plastic wrap or a tight lid is more likely to keep your avocado fresh rather than placing the pit in the mixture.
• Citrus Method - The presence of acid can keep avocados fresh so it will not turn brown. If you have half an avocado, rubbing some lime or lemon juice on the flesh and placing it in a bag will help keep it from turning brown. If you take out as much air as possible from the bag, it can stay in your refrigerator for as much as 2 days. Some flesh may be discolored after this time period, but it can easily be removed. If you are trying to protect pieces of avocado, add a half teaspoon of lemon juice for every avocado and wrap it tightly in plastic wrap, allowing the plastic wrap to come in contact with the avocado flesh to help prevent oxidation.
• Water Method - Cold water can also protect an avocado from turning brown. Restaurants will frequently place avocados in ice water to keep them fresh when they are prepping ingredients in advance. As soon as you cut your avocado, place it in ice water and it will stay green for as much as 4 hours. You can also rinse your avocado in cold water to avoid brown avocado. This will help keep the oxygen out of the avocado so they will stay fresher longer.