Skip to content

Tomato Nutrition: Why are Tomatoes Red?

People who only know tomatoes from the supermarket would say that tomatoes are red in color, but any gardener knows that tomatoes spend the majority of the time green and only turn red at the very end. So, what makes a tomato red, and why does this change in color occur? The changing ratio of two pigments, chlorophyll and lycopene, accompanied by the release of the chemical ethylene, account for this color change. Let’s dig a little deeper into the color changing process.

There are two main pigments present in tomatoes, chlorophyll is green and lycopene is red. Chlorophyll is the most common pigment in fruits and vegetables that are not ripe and is present in large amounts during the early growing season. Once a tomato has reached the mature green stage, the plant starts producing ethylene gas, which triggers the ripening process. Chlorophyll will start to dissolve, and lycopene will take over as the primary pigment. The tomatoes will turn from green to yellow to red. Also during this process, the sugar levels in the tomatoes will rise, causing the fruit to get softer and ready for harvest.

What other factors influence tomato ripening?

Different tomato varieties will ripen at different times. Smaller varieties like cherry or grape tomatoes will ripen earlier than larger ones like beefsteaks. Temperature also plays a role in ripening. The production of lycopene only occurs when temperatures are between approximately 50-85 degrees Fahrenheit. If it is much hotter or cooler than this, the tomatoes will not ripen.

Can you get a tomato to ripen off the vine?

There are various reasons why you might want to encourage tomatoes to ripen off the vine. Growers actually harvest their tomatoes when they are still green. Since the tomatoes are more firm in the green stage, this keeps the tomatoes from bruising and smashing during transportation. When the tomatoes reach their destination, they are sprayed with ethylene gas to encourage them to ripen. The flavors typically do not develop as much as when they are allowed to ripen directly from the vine.

Another situation when you may want to ripen a tomato off the vine is when the fruit has fallen off or is knocked off due to frost or other circumstances. As long as the tomato has reached the mature green stage, it will still ripen. Simply place the unripe tomato in a brown paper bag. The bag will trap the ethylene gas that is being put off and help the tomato to eventually turn red.

Best Tomato Fertilizer

For the perfect red, vine-ripened tomato, we suggest growing your own. With our Chicken Soup for the Soil and the best tomato fertilizer, Dr. JimZ can help you skip the flavorless supermarket tomatoes and grow your own delicious ones. Check out for all your tomato growing needs.


Photo Credit