Mixture Optimisation of the Mineral Nutrition of Tomatoes in Relation to Mineral Content of the Fruit: Effects of preharvest factors on fruit quality

The mineral composition of tomatoes is an important intrinsic quality parameter, concerning both the conservation and the nutritional value of the product. This study investigates the effects of the mineral composition of the nutrient solution and the moisture content of the substrate on the mineral content of hydroponically grown tomato fruits. Using “design and analysis of mixture systems“, a {3.1} simplex lattice design extended with the overall centroid was set-up in the cation factor space (K+, Ca2+ and Mg2+) of the nutrient solution. For each nutritional composition two moisture contents (40 and 80 volume %) of the substrates were investigated.

Higher moisture content of the substrate yielded a higher production, due to the production of more tomatoes of the same weight. Increasing the K+, Ca2+ and Mg2+ concentration of the nutrient solution resulted in a higher potassium, calcium and magnesium content of the fruit respectively. No interaction effect on fruit mineral content between moisture content of the substrate and mineral content of the nutrient solution was found. This study demonstrates the usefulness of mixture theory for investigating the effect of preharvest mineral nutritional factors on fruit quality.