Preserving Fresh Basil After Harvest

I run a Community Shared Agriculture (CSA) business on about 2 acres. I grow three succession plantings (100-300 feet per planting) of basil and all of our members love fresh basil but I have had mixed success with harvesting so that it keeps. What is the best way and time to harvest so that it doesn't turn black and so it stays turgid? What should I tell members about the best way to store it?

Basils are cut continuous throughout their growing season, usually once or twice each week. Once they try to bolt, it's best to finalize the final cut and regroup for the next year's crop. Some like to let them go to full seed, as this becomes your seed source and repository,
Always clean, green chop and then freeze (below 32 degrees) basils for future use and/or manufacturing. This is the only way the volatile oils are preserved and pesto remain flavorful. This would require a walk-in freezer system with your volumes of production.
Once frozen, the integrity is maintained, except for locker burn or moisture somehow getting into the leaf. That is corrected by sealing units in such a way that moisture cannot penetrate the seal. That is NOT done with plastics, and glass works best.