Citrus fruits are a type of fruit that contains high levels of citric acid. The most common citrus fruits include lemons, limes, oranges, and grapefruits. Citrus fruits are a good source of Vitamin C and can be eaten fresh, juiced, or used in cooking.
Citrus fruits are believed to have originated in Southeast Asia and were brought to the Mediterranean region by traders. The first recorded mention of citrus fruits was by Chinese philosopher Confucius (551-479 BC). The Romans were the first to cultivate citrus trees extensively and they introduced these trees into England and other parts of Europe during the 1st century AD.
The word “citrus” comes from the Latin word for lemon, citrus limon. The genus name Citrus is also derived from this same Latin word. The family Rutaceae includes all plants in the genus Citrus as well as other closely related genera such as Fortunella (kumquats), Poncirus (trifoliate orange), Aegle marmelos (bael fruit), Murraya paniculata (jaman) , Atalantia monophylla ( Star aniseed ), Zanthoxylum armatum ( Sichuan pepper ), etc.. Most botanists agree there are between 9-12 species of true citrus while others believe there could be up to 30 species. All true citrus species are evergreen trees or shrubs with alternate leaves that contain oil glands in their blades and petioles . The flowers are white or very pale pink/purple and have many petals arranged in a corymb . Each flower has 8-9 stamens that protrude beyond the petals . After pollination , small greenish berries known as hesperidia develop. These mature into the characteristic round or oval shape we know as citrus fruits . Inside each fruit is a white fleshy edible part called the pulp which is surrounded by thin albedo tissue . This tissue contains essential oils that give each citrus its unique flavor . Between the pulp and outer rind is another layer called pith which is composed of spongy white material filled with air cells . It is important to note that not all Hesperidia produce edible fruit – some like mandarin oranges produce small seeds instead while others like grapefruit can have large seeds or no seeds at all depending on cultivar . Finally,the outermost layer is what we call the peel or rind which protects the inner layers from damage/dehydration & pests but also contains valuable flavoring agents itself such as limonene & terpenes depending on species/cultivar