In recent years, the market development of hoppy top fermented beers has seen products such as pale ales and India pale ales gain an increased reputation. This, in fact, leads to an increasing scientific view on flavor changes and off-flavor evolution in these products. The basic assumptions of hoppy beer’s (off-) flavor evolution are mostly based on studies dealing with model solutions or lager style beers. As hoppy beers are different, the increase in certain off-flavor compounds can affect product enjoyment to the same degree as the decrease of pleasant notes do. In turn, fundamental research on the aging behavior of hoppy ales is needed to assess and avert flavor changes in these products. For this reason, three comprehensive studies on sensory and chemical changes of hoppy ales during long term storage were performed in this thesis. Publication A “The influence of storage conditions on the chemistry and flavor of hoppy ales” presents a basic overview of chemical and sensory changes of 11 German hoppy ales with a lager beer as reference. The beers were analyzed after forced aging and during a 24-week storage period at 4 °C and 20 °C. Due to their basic parameters (i.e., original gravity, apparent degree of attenuation, alcohol by volume, bitterness, and color), the chosen hoppy ales represented a good cross section of commercially available products. The chemical decomposition revealed that compared to the tested lager, fresh hoppy ales showed high initial levels of staling aldehydes. The group of Strecker aldehydes further rose during storage. A driving factor of staling aldehyde increase was storage under ambient conditions (20 °C, dark). The sensory impression “oxidized” was clearly driven by increasing levels of staling aldehydes (mainly as Strecker aldehydes such as 2-methylpropanal, 2-methylbutanal and 3-methylbutanal) after 24 weeks. By storing the beers at 4 °C in the dark, the “oxidized” off-flavor was suppressed. Furthermore, the “intensity of hop aroma” was negatively correlated with the “oxidized” impression. That indicates that substances leading to this certain off-flavor are behaving antagonistically to the desired impression of hop aroma in these styles (e.g., monoterpene alcohols). Ales high in hop volatile compounds like terpenoids (i.e., geraniol) were shown to have a more stable hop aroma over time while products high in esters (i.e., 2-methylbutyl isobutyrate) tended to be more unstable during prolonged storage. As mentioned, the temperature conditions impact the chemical and sensory profiles of hop forward ales and furthermore, predictions using forced aging did not prove to be effective. After forced aging some of the products investigated showed results comparable to 24 weeks of room temperature storage, whereas others did not support these observations. In Publication B “Development and Validation of a HS-SPME-GC-SIM-MS Multi-Method Targeting Hop-Derived Esters in Beer”, an assay for quantifying 16 hop-derived esters (e.g., isobutyric and geranyl-esters) from different ales was developed. This highly sensitive and fully validated method enables quantification of esters across a range of 1–200 μg/L, with calculated limits of quantification well below 1 μg/L. Spiking trials using terpenes and terpenoids showed a high robustness of this method by using two commercially available stable isotope labeled internal standards (namely d6-geranyl acetate and 13C-methyl octanoate). The method was further applied on different hoppy ales (i.e., pale ale, IPA, New England IPA, and fruit infused IPA) that were analyzed fresh and after a storage of 30 months at 20 °C in the dark. The results showed varying concentrations of these hop related esters in the different beers. Furthermore, it was shown that compounds such as ethyl 2-methylbutyrate, ethyl 3-methylbutyrate, or ethyl isobutyrate increased during the applied storage period, while other esters (i.e., isobutyl isobutyrate, 3-methylbutyl isobutyrate, or methyl geranate) decreased. These results show the importance of a sensitive method to analyze these compounds in beverages over storage as chemical changes might further influence the sensory impressions of hoppy ales. Publication C "Effect of pasteurisation on the evolution of terpenes, terpenoids, aldehydes and esters in hoppy ales upon ageing" builds on the results from Publications A and B and applies them on IPAs. For this purpose, aging parameters (e.g., aldehydes, hop aroma compounds or esters) were investigated in combination with technological aspects of shelf-life improvement (pasteurization and storage conditions) on four unpasteurized German IPAs. Each beer was subjected to two pretreatments. One portion remained unpasteurized, while another one was thermally treated in a laboratory scale simulating a tunnel pasteurizer. Subsequently, the beers were stored at 4 °C and at 20 °C in the dark. Analyses were performed on each of the treated and untreated products at the beginning of the study and after 4, 12, 24 and 52 weeks of storage. The analysis of known aging parameters (terpenes, terpenoids, higher alcohols, fermentation esters, and staling aldehydes) were supplemented by hop-relevant esters. Depending on the treatment and storage temperature, the aroma compounds in the IPAs displayed different behaviors. It has been shown that cold storage has a major impact on reducing flavor changes, however, if the beers are distributed over a long (non-refrigerated) distances, pasteurization may be an opportunity to reduce changes in beer flavor. The results highlight the need for brewers and distributors to work together to ensure an optimal beer flavor profile during distribution. Due to the distinct aroma of top-fermented hoppy beers, it is not possible to transfer the behavior of lager beer during aging to these products. In summary, new findings on the aging behavior of hoppy, top-fermented beers were obtained within this thesis. Even though substances that rapidly contribute to the aging impression in lager styles may cause an oxidative taste in hoppy products during aging, these substances tend to be masked by the desired hop aromas. Thus, it is fundamental to protect these hop aroma compounds against reduction during aging. The developed HS-SPME-GC-SIM-MS method to analyze hop esters in beer assists in detecting changes in μg/L levels. This supplement known parameters of aroma changes with a new analytical assay. Investigations on more realistic and ideal storage conditions (20 °C / 4 °C) were extended by pasteurization tests that demonstrate the benefits of pasteurization in combination with cold storage. If hoppy ales are sold and consumed quickly, cold storage without pasteurization is a suitable option; if the storage time increases due to shipping without being able to facilitate a continuous cold chain, pasteurization can help to minimize changes in odor and taste. The published method, as well as the acquired knowledge, can directly help brewing engineers and chemists get their products delivered to the consumers in the best possible way by minimizing changes in the ale aroma during shelf life.