In the process of pasteurizing, juice is heated and stripped of oxygen, a process called deaeration, so it doesn’t oxidize. Then it’s put in huge storage tanks where it can be kept for upwards of a year. It gets stripped of flavor-providing chemicals, which are volatile. When it’s ready for packaging, companies such as Tropicana hire flavor companies such as Firmenich to engineer flavor packs to make it taste fresh. People think not-from-concentrate is a fresher product, but it also sits in storage for quite a long time.