## 3 Results and Discussion
### Addition of Kokumi Peptides Reduces Bitter Taste  
Bitterness is not a preferred taste for many people. Many nutritious foods like vegetables and cereals contain compounds such as isothi cyanates or glucosinolates that can cause bitterness [54]. These flavours can be further accentuated in plant-based upcycled products [55], preventing wider acceptance and changes in dietary habits towards more planetary friendly food options [8]. Kokumi peptides have been studied to increase umami, saltiness, sweetness, and fatty texture [17]. In particular, bitterness has been implicated to be reduced by fermentation through \(\gamma\)-glutamyl reactions [39]. Based on this observation, our study tested whether the \(\gamma\)-glutamyl peptides produced during the fermentation of our upcycled miso were able to reduce bitterness when added to plant-based ingredients. Endive (_Cichorium intybus var. foliosum_) was selected as the vegetable for our sensory analysis due to its distinct bitter taste produced by glucosinolates [12]. Using a method of water extraction, we obtained an extract from each of our upcycled misos that was rich in kokumi peptides, and after adding them to the endive puree in the same concentrations, performed sensory analysis for each of the samples (for details, see Materials and Methods). It should be noted that extraction and sensory analysis were only performed for three of the four misos (barley S1/BSG, wheat bran S1/barley, and wheat bran S2/barley). The wheat bran S1/BSG miso was excluded due to the undesirable aroma profile and unexpectedly high pH observed throughout the fermentation. For the sensory analysis, an intensity scale was used to evaluate the bitterness, aftertaste, coating, and thickness. The questionnaire also included questions about the participants' attitudes to vegetables in order to establish whether their preferences and previous experiences might affect their perception of bitterness. Results from the sensory analysis confirmed our hypothesis that the addition of kokumi-rich miso extracts could reduce the perceived bitterness in the endive samples; we observed that this was the case for two of the three samples tested. The endive sample containing extract from the barley S1/BSG miso was perceived to be the least bitter, followed by wheat bran S1/barley, control (water instead of extract added), and wheat bran S2/barley (Figure 5). This result may partly be explained by the total abundance of \(\gamma\)-glutamyl peptides in each sample (Figure 5B), where barley S1/BSG miso has the highest amount, followed by wheat bran S2/barley and wheat bran S1/barley. Interestingly, despite wheat bran S1/barley having a lower abundance of \(\gamma\)-glutamyl peptides overall, it shows a higher absolute quantity of \(\gamma\)-EVG than wheat bran S2/BSG (Figure 5B). \(\gamma\)-EVG has been reported as a potent kokumi peptide with a sensory activity that is 12.8-fold stronger than GSH [56]. The higher abundance of \(\gamma\)-EVG in the wheat bran S2/BSG could, therefore, be a possible explanation for why its addition to endive puree results in lower perceptions of bitterness than the wheat bran S1/BSG sample. In terms of the other attributes assessed in the sensory analysis, aftertaste was the only attribute other than bitterness that significantly differed between samples (Table 2). This could be the result of the lingering bitterness, especially for the sample containing the extract from the wheat bran S2/barley, which was perceived to be the most bitter and was ranked the highest for aftertaste (Figure 5A). Other studies have shown that the extent and impact between the bitter taste and aftertaste may be related to the regional distribution of bitter taste receptors on our tongue [57]. Future experiments should investigate whether \(\gamma\)-glutamyl peptides have differential effects on different bitter taste receptors. Finally, our study found that participants who reported liking vegetables perceived the bitterness as being lower than those who did not.