Purpose: The nutritional products for patients with liver failure available on the Japanese market contain many branched-chain amino acids (BCAAs), such as L-leucine, L-isoleucine, and L-valine, which not only have a bitter taste but also strong, unpleasant odours, leading to low palatability. The palatability of these nutritional products can be significantly improved by the addition of flavoured powders. The purpose of the present study was to evaluate the effects of specific flavoured powders on the palatability of nutritional products. Method: In the present paper, three experiments were performed to clarify the effect of taste–odour interactions on improvements in palatability of nutritional products. Results: First, the effect of flavoured powders on the palatability of single nutritional products was studied in subjects with and without nose clips. The improvement of palatability of the flavoured powders was reduced in subjects wearing nose clips. This suggests that odour has a significant effect on palatability. In the second experiment, it was demonstrated that liquid aromas could significantly suppress the bitterness of quinine sulphate. The aromas increased the bitterness threshold for quinine, causing bitterness suppression. In the third experiment, it was confirmed that the sweet taste of sucrose together with the aroma used in experiment 2, synergistically suppressed the bitterness of a BCAA solution. Conclusion: As far as the palatability of nutrients for liver failure is concerned, it appears that not only bitterness but the smell itself is a critical factor. Moreover, it is clear that the sweetness evoked by the odour of the aroma inhibited the bitterness of BCAA.