The invention relates to a kit of parts comprising 2 to 100 containers each containing an infant formula, wherein each infant formula is in a form suitable for administration to an infant and/or toddler or in a form suitable for administration to an infant and/or toddler after admixing with an aqueous liquid, wherein the kit of part comprises at least two different infant formulas which differ from each other in taste and/or flavor by having a different protein fraction or by being a fermented infant formula, wherein each of the different protein fractions is selected from the group consisting of intact milk proteins including cow milk proteins, intact plant proteins including soy protein, hydrolysed proteins, free amino acids, or mixtures of two or more thereof.