Color is particularly important for processed tomatoes and the fruit needs to be of a uniform, strong red, free of defects such as cracks and bruises. Color is measured using a range of methods, including spectrophotometry and colorimetry. Processors lay down a strict range of values. Processed crops must ripen evenly and at least 75% of the fruit has to be mature at harvest.
Low levels of potassium can lead to poor coloration in tomatoes and reduced lycopene synthesis.
Magnesium is particularly important in ensuring even ripening of well-formed fruit.