# Forging Prawn and Salmon Flavours with Non-Animal-Based Ingredients
## 3 Results and Discussion  
### Volatile Composition of PB Prawn and Salmon Prototypes  
A total of 64 volatile compounds were identified across PB prawn and salmon prototypes with various treatments. These included eight acids, eight alcohols, nineteen aldehydes, four furans, thirteen ketones, ten N-containing compounds, and two S-containing compounds. Significant (\(p<0.05\)) differences across samples were observed. A detailed summary comparison of volatiles in each sample compared by one-way ANOVA is provided in Supplementary Materials S1. To provide a clearer visualisation of the results, PCA was performed, where about 50% of the total variance was explained by the first two principal components (PCs, Figure 1). The positive side of PC1 was associated with high levels of alcohols, aldehydes, ketones,and furans, while the negative side was dominated by 2,3-pentanedione, acetic acid, and 3-methylbutanoic acid. This distribution placed most raw (R) and thermally stabilised (TS) samples for both prawn and salmon prototypes on the negative side of PC1. After subjecting the samples to frying (FTS), the samples shifted to the positive side of PC1, and this was most apparent for the prawn samples P + DHA + PFM and P + DHA. Within each prototype formulation, thermal treatment resulted in a consistent shift toward the positive side of PC1. Additionally, pyrazines and sulphides drove the distinct separation of the P + DHA + PFM (FTS) sample on the positive end of PC2. This trend was also observed for S + DHA + PFM (FTS), but to a lesser extent. The PCA highlighted the impact of formulation and thermal treatment on volatile profiles, being most strongly influenced by the higher FAAs present in the prawn samples. Typical DHA degradation products were higher in the fried prawn samples, even though they had a much lower lipid and DHA content. Raw PB prawn and salmon prototypes exhibited similar volatile profiles, regardless of the inclusion of DHA or FAA-based flavour mixes. Following thermal stabilisation by steaming, relatively small changes in volatile profiles occurred compared to frying. The vacuum-sealing of prototypes prior to steaming likely limited oxygen exposure and oxidative degradation of PUFAs, especially in salmon prototypes such as S (TS), S + DHA (TS), and S + DHA + SFM (TS), which remained on the negative side of PC1. Frying induced more substantial changes, particularly in PB prawn prototypes. The higher FAA content in prawn formulations likely contributed to the formation of reactive intermediates that accelerated PUFA breakdown, even in low-oxygen conditions [26]. This was reflected in the volatile profiles of P (FTS), P + DHA (FTS), and P + DHA + PFM (FTS). Without PFM, P and P + DHA displayed distinct volatile profiles due to differences in PUFA-derived compounds. The inclusion of PFM resulted in significantly higher levels of pyrazines and sulphide compounds, generated through Strecker degradation and Maillard reactions, creating a profile that was markedly distinct from the other prawn prototypes. A similar trend was observed in S + DHA + SFM (FTS). Figure 1: PCA biplot illustrating sample discrimination based on volatile composition. Formulations aiming to mimic prawn and salmon flavours are labelled in blue and yellow, respectively. Thermal treatments are indicated as follows: no thermal treatment applied (R), thermally stabilised (TS), and fired after thermal stabilisation (FTS). Volatile compounds are labelled with red triangles. However, due to the lower FAA content in SFM compared to PFM, the production of pyrazines and sulphide compounds was not as pronounced. The pan-frying process was designed to replicate a typical cooking method for prawn, salmon, and their PB analogues.