High brix ..I think its actually the measure of the number of covalent bonds within the plant tissue, which includes minerals, sugars as mentioned, acids, and (often sulfur-containing) flavour-compounds too
This can be achieved organically or more or less synthetically, I would think
Being organic, tho
..I think its about Evaporated organic cane juice-fed worm teas, fresh young coconut water, a timely sulphur/magnesium foliar application, and a little aloe vera help keep the vitamin, mineral, enzyme, and exudate levels high in the rhizospheres
Of course a high population of balanced bacteria and fungi in a healthy preferably humus based soil with a plant who has either a bene biofilm / plenty of chitin/ase / bene bio predators would be other prerequisites, otherwise one risks losing all that hard work n plant tissue goodness to pests like thrips
Defense first!