Towards a control theory for acidity of vegetable crops

Quality attributes of vegetables can be changed by the way a crop and its environment are managed, as is routinely done by wine growers. Raw product with higher acidity may offer opportunities for novel processing and products. Our aim is to characterise how acidity is controlled in a range of vegetable crops to see if general theories can be developed. We are progressing a control theory for processing tomato and testing its applicability to capsicum and chilli cultivars. Control is partly via weather (thermal time and solar radiation) and partly stresses (water or nutrient deficit), but may also involve direct effects of nutrient cations on [H+]. Among storage root and leaf type crops our initial findings suggest that acidity control know-how may be commercially important in some species but not others. One way to distinguish this among species may be the value of the ratio of (0)Brix to titratable acidity.