Abstract/Summary

Smoked ingredients are used to improve the organoleptic qualities of culinary products in the food industry. This can be due to the pleasant fragrant aroma derived from the smoke, but we hypothesise that it may also be due to taste enhancement, either directly through the activity of tastant molecules or possibly from odour-induced taste enhancement (OITE). It might be possible to use smoked ingredients to reduce salt or monosodium glutamate (MSG) levels in food products. However, the smoking process, which is required for flavour development, also produces a series of polyaromatic hydrocarbons (PAHs), including the known human carcinogen benzo[a]pyrene. The concentrations of PAHs can now be reduced using Puresmoke technologyTM (PST). This technology has been shown to remove aroma compounds from the smoke, but also results in a more balanced aroma. The aim of the thesis is to investigate the contribution smoked water makes to the flavour of a soup matrix, comparing both PST and traditionally smoked water (TR). In the first instance, it is important to understand what the important aroma compounds in smoke are and the impact of PST on the flavour profile. Smoked water was selected for an in-depth analysis of the aroma compounds using a low (P25) and a high (P50) number of filter plates of PST. The effect of P25 and P50 on 77 volatile compounds using 3 wood types (apple, beech, and oak) was investigated using a sensomics approach. Solid phase microextraction (SPME) and solid phase extraction (SPE) which used diethyl ether as the eluent, were the two most effective extraction techniques for smoked water based on the number of compounds extracted. Seventy-seven aroma-active compounds were detected in P50 and TR apple-wood smoked water. The most abundant compounds were phenol and phenol derivatives, followed by aldehydes, ketones, diketones and guaiacol and guaiacol derivatives, in that order. In general, the main constituents were found in higher concentrations in TR than in PST smoked water. Aroma extract dilution analysis (AEDA) was employed in both SPME and SPE extracts to determine the most odour-active compounds. A total of 67 aroma-active compounds were detected by gas chromatography-olfactometry (GC-O), the majority of which were phenols and guaiacols. At least 22 compounds with odour activity values (OAVs) more than 1 were identified as potent aroma compounds. To confirm the identity of the odour-active compounds, the identified 22 potent aromas were combined to generate full and partial recombinates at concentrations corresponding to those in P50 smoked water. The sensory profiling scores (5- point scale) of four descriptors, smoky, woody, ashy, and phenolic, of the recombinates did not closely correspond to the original P50 smoked water, indicating that more refinement of the recombinate was required. The effect of PST on the aroma profile (77 compounds) was analysed in smoked water prepared from three different types of hardwood, each compared to TR smoked water. When the PST was used, the majority of compounds were reduced. The difference between P25 and P50 was significantly less than the difference between TR and P25. The principal component analysis (PCA) plot determined that apple smoked waters were associated with higher concentrations of phenols group, traditionally beech smoked water had high levels of syringols and guaiacols. All three samples of oak-smoked water were similar and had high levels of furans. Three mechanisms of smoked water on flavour enhancement were investigated using trained sensory panellists. In the absence of MSG, the panel with the aroma excluded through wearing of nose clips, detected an umami taste in the presence of apple-wood smoked water. In the complex mixture of model soup, the smoked water made little difference to the umami taste and when smoked water was added to the mixture of MSG and 5'-ribonucleotides, there was no umami enhancement. However, an umami enhancement was observed in the model soup containing MSG and 5'-ribonucleotides at subthreshold umami levels (below 344 mg/L or 0.038%). Intriguingly, umami was the primary taste that was enhanced when smoked water was combined with 5'-ribonucleotides in salt-reduced soups without using nose clips. This result suggests that odour-induced taste enhancement was the primary mechanism by which smoked water enhanced flavour. In contrast, partial recombinate (17 compounds) did not significantly enhance the tastes of salt-reduced soup compared to salt-reduced soup without recombinate.