Monosodium phosphate (E339i)

No. Monosodium phosphate (E339i) is not one of the markers Open Food Facts uses to classify a food as processed or ultra-processed, so on its own it doesn't raise a product's NOVA group.

What it is

Emulsifiers are substances which make it possible to form or maintain a homogenous mixture of two or more immiscible phases such as oil and water in a foodstuff.

A product that contains it can still be ultra-processed for other reasons: 7 of the 7 products here that contain monosodium phosphate (E339i) (100%) are in group 4 because of other ingredients or additives.

Function

Emulsifier: Emulsifiers are substances which make it possible to form or maintain a homogenous mixture of two or more immiscible phases such as oil and water in a foodstuff.
Humectant: Humectants are substances which prevent foods from drying out by counteracting the effect of an atmosphere having a low degree of humidity, or promote the dissolution of a powder in an aqueous medium.
Preservative: Preservatives are substances which prolong the shelf-life of foods by protecting them against deterioration caused by micro-organisms and/or which protect against growth of pathogenic micro-organisms.
Sequestrant: Sequestrants are substances which form chemical complexes with metallic ions.
Stabiliser: Stabilisers are substances which make it possible to maintain the physico-chemical state of a foodstuff; stabilisers include substances which enable the maintenance of a homogenous dispersion of two or more immiscible substances in a foodstuff, substances which stabilise, retain or intensify an existing colour of a foodstuff and substances which increase the binding capacity of the food, including the formation of cross-links between proteins enabling the binding of food pieces into re-constituted food.
Thickener: Thickeners are substances which increase the viscosity of a foodstuff.