Taste of Nordic forests: Analysis of the taste of mushrooms and taste modification properties of nanocellulose

The assessment of taste eliciting compound concentrations and interactions is a vital part of food sciences. Even though many interactions are known and widely studied, both the complexity of food and the unique nature of human taste perceptions make it more difficult to draw conclusions about the impact of these interactions on actual perception solely based on instrumental studies. In this thesis, the taste properties of two different matrices were studied with sensory and instrumental methods, the emphasis being on instrumental analysis. First, the taste of mushrooms was analyzed as a part of a larger research entity on the total flavor and hedonic liking of the Nordic mushrooms. Simultaneously, free amino acid and nucleotide/nucleoside contents of mushrooms were analyzed and combined with results from sensory analysis and data of sugar, sugar alcohol and organic acid composition. Secondly, to learn about possibilities to utilize nanocellulose in food applications, particularly in bitterness modification, the impact of nanofibrillar cellulose on selected taste compounds was analyzed with a novel high-throughput method based on fluorescent indicator displacement and further, with sensory methods.

In this thesis, new methods were developed to analyze the free amino acid and nucleotide/nucleoside contents in mushrooms and the binding strengths between nanocellulose and taste compounds. These results were compared with the results from sensory evaluations. According to the statistical analysis, umami taste of mushrooms was not correlated primarily with glutamic acid or sweetness with total sugar contents, but they correlated better with umami enhancing nucleotides/EUC values and with the sugar-acid ratio, respectively. Further, relatively high binding was found particularly between nanofibrillar cellulose and bitter tasting quinine while compounds like sucrose, glutamic acid or aspartame showed no binding letting us to believe that nanocellulose could have ability to suppress bitterness. However, according to sensory studies, the taste modification ability of nanocellulose was on the same level or poorer as with carboxymethyl cellulose that was used as a reference. Both research entities emphasize the complexity of the taste perception. Even though instrumental methods provide valuable guidelines to be followed, particularly when studying novel materials, such as nanocellulose in this dissertation, the effect of chemical composition on taste is difficult to predict without sensory evaluations.