Search

Hop terpenes might be oxidized during kettle boiling into more water soluble compounds that could contribute to 'hoppy' aroma of kettle hopped lager beers. Our current research proves that the boiling process induces significant changes in the hop oil volatile profile. The discrimination between volatile profiles of unboiled and boiled hop essential oil was evaluated via principal component and cluster analysis (PCA and CA). HS-SPME-GC-MS analysis revealed quantitative changes (e.g. increases in the levels of oxygenated α-humulene and β-caryophyllene derivatives) as well as qualitative changes (i.e. detection of compounds, not found in unboiled hop essential oil) in the hop oil volatile profile upon boiling. Many of these compounds were previously found in lager beer and may therefore contribute to beer flavor. Interestingly, the analytical difference between unboiled and boiled hop essential oil proved to be more pronounced as the initial hop essential oil concentration used for boiling was increased. In addition, lager beers spiked with boiled hop oil were described as 'hoppy/spicy' during sensory evaluations. Therefore, the newly formed products and hop oil constituents that are characterized by an increased recovery after boiling, are candidate compounds for 'hoppy' aroma in real brewing practice., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The volatile composition of novel varietal oxygenated sesquiterpenoid hop oil fractions ("spicy essences") was characterized by headspace solid-phase microextraction in combination with gas chromatography-mass spectrometry. Oxygenated sesquiterpenes represent the major chemical compound class, accounting for at least 65% of the total volatile fraction. In addition to oxygenated sesquiterpenes, spicy hop essences consist of several ketones, sesquiterpene and monoterpene hydrocarbons, and a relatively high number of unidentified compounds. On the basis of their relative composition, spicy hop essences can be fully differentiated according to their varietal origin. Multidimensional gas chromatography in combination with time-of-flight mass spectrometry on spicy hop essence cv. Spalter Select further demonstrated the enormous complexity of this particular hop oil fraction. The aromagram obtained via gas chromatography-olfactometry comprised nine odor-active regions described in terms of "citrus", "green", "haylike", "earthy", "woody", and "spicy". 2-Undecanone, 2-tridecanone, γ-cadinene, α-calacorene, calarene, humuladienone, caryolan-1-ol, caryophyllene oxide enantiomers, and humulene epoxide II are tentatively identified in the odor-active zones.

Technological advances are often inspired by nature, considering that engineering is frequently faced by the same challenges as organisms in nature. One such interesting challenge is creating a structure that is at the same time stiff in a certain direction, yet flexible in another. The seahorse tail combines both radial stiffness and bending flexibility in a particularly elegant way: even though the tail is covered in a protective armour, it still shows sufficient flexibility to fully function as a prehensile organ. We therefore study the complex mechanics and dynamics of the musculoskeletal system of the seahorse tail from an engineering point of view. The seahorse tail derives its combination of flexibility and resilience from a chain of articulating skeletal segments. A versatile dynamic model of those segments was constructed, on the basis of automatic recognition of joint positions and muscle attachments. Both muscle structures that are thought to be responsible for ventral and ventral-lateral tail bending, namely the median ventral muscles and the hypaxial myomere muscles, were included in the model. Simulations on the model consist mainly of dynamic multi-body simulations. The results show that the sequential structure of uniformly shaped bony segments can remain flexible because of gliding joints that connect the corners of the segments. Radial stiffness on the other hand is obtained through the support that the central vertebra provides to the tail plating. Such insights could help in designing biomedical instruments that specifically require both high bending flexibility and radial stiffness (e.g. flexible stents and steerable catheters)., (Copyright © 2012 John Wiley & Sons, Ltd.)