Frozen beetroot is normally cooked rather than merely blanched, then peeled, cut and frozen. That is the main difference from a green vegetable line, and it explains most of what a buyer sees in the finished product: full colour development, a cooked texture, and a shelf-stable colour that does not fade the way a raw-frozen root would.
The sequence in a typical plant runs as follows. Roots are received from field or from store, since beetroot keeps well and can be processed outside the harvest window. They are destoned and washed, often twice, because soil in the crown creases is the main foreign-body risk on this crop. They are then cooked, commonly by steam or in water at close to boiling, for a time set by root size and measured in tens of minutes rather than in the seconds a green vegetable takes. Cooking also loosens the skin.
Peeling follows cooking, usually mechanically by abrasion or by steam peeling, and is followed by trimming of crown and tail. The peeled roots are then cut to the required form: dice of 8 to 15 millimetres, slices, batons or wedges. Cut product is cooled, most often by chilled water or a chilled air tunnel, and then frozen, either on an IQF belt or fluidised bed for free-flowing dice or as a formed block.
Two attributes dominate the specification. Colour, because betalain pigment is the reason the product is bought and it is affected by variety, maturity and cook time; colour is usually assessed against a retained reference on thawed product. And free liquid on thaw, because a cooked root releases coloured liquid, and the amount of it decides whether the product works in a salad application or bleeds into a blend.
Nitrate is worth a question. Beetroot is a nitrate-accumulating crop, and while EU maximum levels are set for certain leafy vegetables rather than for beetroot generally, buyers serving infant or child nutrition applications frequently specify their own limit.