Lemon and orange extract can both be made quite easily in your kitchen. It uses the concept of extraction to preserve and concentrate that flavour!
How to Make Lemon Extract - Chef Tariq - Food Blog
How to Make Pectin From Orange Peel
How to Make Orange & Lemon Zest Extract by Alcohol Extraction - FoodCrumbles
This is leftover lemon peel after alcohol extraction (making limoncello). Can I put it in potting mix/garden soil? : r/gardening
Embark on a Culinary Adventure with Exotic Citrus Melody Extract – Culinary Solvent
Recovery of Phenolic Compounds from Orange Peel Waste by Conventional and Assisted Extraction Techniques Using Sustainable Solvents
Frontiers Comparative flavonoid profile of orange (Citrus sinensis) flavedo and albedo extracted by conventional and emerging techniques using UPLC-IMS-MS, chemometrics and antioxidant effects
How to Make Orange Extract + Free Labels - Tidbits
How Food Works - Page 2 of 2 - FoodCrumbles
3 Ways to Extract Oil from Orange Peels - wikiHow