There is a number of variables that define tomato quality requirements.
The degree and level of these external factors can have a big impact on tomato crop price and marketability. Acceptable size and grade varies according to market, most countries set their minimum standards.
Flavor of tomato is generally related to the relative concentrations of sugars and acids in the fruit, mainly fructose and citric acid. The best, most flavorsome combination is a high sugar and high acid content.
Nitrogen and potassium are important for tomato aroma. Too much ammonium-N adversely affects taste. Potassium on the other hand is the main nutrient affecting the overall quality of the tomato, improving the uniformity of ripening, shape, acidity and taste of fruit.
High levels of calcium are important in maintaining firmness and preventing damages due to disorders or during handling and transportation.
Low levels of boron can lead to poor marketable tomato quality. Zinc also has a role to play in maintaining tomato fruit quality.