# Profiling Croatian Whisky Using GC/MS-MS and UHPLC-QTOF
## 3 Results and Discussion
### Aromatic Profile of Croatian Whisky Determined by SPME-GC-MS
#### 3.3.3. Organic Acids in Whisky  
Ten organic acids were identified in tested whiskies: fumaric acid, glucoheptonic acid, acetic acid, D-glyceric acid, lactobionic acid, threonine acid, gluconic acid, homocitric acid, citramalic, and glutaric acid. Fumaric acid is an intermediate in the Krebs cycle. As a product of fermentation, fumarate can contribute to the acidity and therefore flavor profile of whisky [31; 37]. Glucoheptonic acid, sugar acid, may form from the oxidation of sugars during fermentation and aging processes in whisky production, influencing its sweetness and mouthfeel characteristics [1; 20]. Acetic acid is a by-product of yeastferentation that contributes the tart flavor profile of whisky. Acetic acid also can act as a precursor to form secondary metabolites, such as higher alcohols, esters, fatty acids, and other lipids when it reacts with acetyl-CoA. For example, acetic acid can serve as a precursor to ethyl acetate, which contributes sweet and fruity aromas. Elevated levels of ethyl acetate could be attributed to the initially produced acetic acid (by _Lactobacillus_) being subsequently metabolized by yeast or formed through esterification during one of the distillation stages. Usually, acetate esters provide fruity notes in new-make spirit [1; 14; 38]. These findings are consistent with research by [PERSON] et al. [45], which demonstrated that higher concentrations of acetaldehyde and ethyl acetate are achieved when a distillery fermentation is co-inoculated with _Lactobacillus_. Acetoacetic acid, a \(\beta\)-keto acid, may be present in whisky as a result of yeast metabolism during fermentation. It can contribute certain acidic notes to the whisky's profile and at higher concentrations it could lead to off-flavors [31]. D-glyceric acid is an intermediate in carbohydrate metabolism, and it can be found in whisky as a metabolic product from yeast during fermentation. Moreover, it can contribute to the acidity and overall flavor profile of the whisky. Another sugar-based acid detected in whisky is lactobionic acid, a congener derived from lactose oxidation, which can enhance the sweetness and mouthfeel of the whisky [1; 23; 31]. Threonine acid, an oxidation product of ascorbic acid, may also impact the flavor profile. Gluconic acid influences the acidity/taste, and it is formed through glucose oxidation. D-glucuron acid might influence flavor due to its presence in maturation processes/sources such as grains or fermentation metabolites [3; 14; 46]. Homocitric acid is associated with the citric acid cycle. It is found in specific fermentation processes, likely as a result of yeast metabolism during whisky production, and may impact whisky's acidity profile [1; 37]. Citramatic acid and glutaratic acid are both dicarboxylic acids, and their presence may influence flavor and mouthfeel characteristics. Citramalic acid forms during metabolic processes, likely arising during fermentation, providing subtle flavor nuances. Glutaric acid, another dicarboxylic acid, could be produced during the fermentation or derived from the grain raw materials [15].