Scientifically, this tart-tasting fruit is Citrus paradisi
The grapefruit has a distinctive bitter taste and is ideal eaten as it is, or in... [DOC] [TLE] Bitter taste, phytonutrients, and the consumer: a review [PAR] Sensitized to the bitter taste of plant alkaloids and other poisons, humans reject 
.... Flavonoids in citrus fruit include flavanones (naringin), flavones (nobiletin), 
and ...... and naringin in the fruit tissues of three varieties of Citrus paradisi.