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A new methodology for the selective isolation of varietal total hop essential oil from hop pellets and further chromatographic fractionation of total hop oil into terpeneless polar hop essence, is presented. The methodology is essentially based on supercritical fluid extraction (SFE) of total hop essential oil using carbon dioxide of appropriate density, followed by solid phase extraction (SPE) using octadecylsilica and ethanol/water mixtures for preparation of polar hop essence. Different SFE temperature–pressure combinations were tested for extraction of total hop essential oil from pellets. A carbon dioxide density of 0.50 g/mL (50 °C, 110 atm), proved to be the best compromise in view of selective and quantitative extraction of total hop essential oils. Further fractionation of total hop essential oil by SPE in order to remove hydrocarbons, resulted in varietal polar hop essence, highly enriched in water-soluble, oxygenated hop oil constituents. All of the applied procedures of the proposed SFE/SPE methodology are in full accordance with the principles of clean-label technology. As a result, the novel hop aroma products are fully compatible with the beer matrix. When added to beer, the novel hop oil preparations impart a typical, varietal dependant pleasant hoppy character and increase beer bitterness and mouthfeel.

Volatile compounds in traditional sorghum beer ikigage brewed with Vernonia amygdalina were investigated using Headspace-Solid Phase Micro Extraction (HS-SPME) and gas chromatography–mass spectrometry (GC/MS). A total of 75 volatile compounds were identified in the traditional ikigage made by Rwandese peasants (using V. amygdalina leaves during the preparation of traditional leaven) and pilot ikigage brewed with and without addition of V. amygdalina in the boiling kettle (instead of hops). Traditional sorghum beer brewed with V. amygdalina was characterized by the presence of higher levels of esters, alcohols and fatty acids. Ethyl acetate, ethyl caprylate, ethyl caproate and ethyl caprate are the main ester components with higher concentrations. Higher alcohols were mainly composed of propan-1-ol, 2-methyl propan-1-ol, 3-methylbutan-1-ol, 2-methylbutan-1-ol and 2-phenylethanol. Acetic, caproic and caprylic acids were the most important fatty acids. Volatile phenols such as 2-methoxy-4-vinylphenol, 4-vinylphenol and 2-methoxyphenol were also detected in the sorghum beer ikigage and may contribute to its phenolic note. V. amygdalina provides the terpenes compounds (δ-3-carene, β-farnesene, farnesol, β-citronellol and linalool), methyl salycilate and beta-damascenone in the sorghum beer. Like in hopped beers, these compounds might play a significant role in the overall flavor and aroma of the sorghum beer ikigage. V. amygdalina leaves emerge as an interesting hops substitute for tropical beers, but complementary data are still needed to understand which volatile compounds or precursors preexist in V. amygdalina.

In order to improve the hydrolysis of cellulose fiber and to obtain highly concentrated hydrolysate, two methods based on successive addition of enzyme and substrate were assessed.

The first method, which required only substrate addition, allowed to increase by 50% the hydrolysate concentration and to decrease by 30% enzyme units needed.

The second method highlighted the ability to reach very high concentrated hydrolysate (up to 170 g/l) by simultaneous addition of enzyme and substrate.

In parallel, relationships between some limiting factors and the yields of hydrolysis were investigated. In conclusion, viscosity evolution of cellulose suspension during hydrolysis step was investigated with an aim to improve the management of enzyme and substrate addition.

Despite intensive research on the gushing of carbonated beverages during the last decades, there is no universal method to predict its occurrence and consequently how to avoid the economic losses it induces. Primary gushing can be visualized as the strong overfoaming and/or strong liquid expulsion of liquid when a bottle of carbonated beverage is opened. This process results from the interaction between gaseous CO₂ and class II hydrophobins. Both chemicals are present in the pressurized liquid as CO₂ nanobubbles coated by hydrophobins which explode when at bottle opening the pressure is released, which results in a vigorous expulsing of CO₂. Hydrophobins are produced by filamentous fungi in the field or during storage and processing. To avoid gushing of beers, their early detection in the barley-to-beer chain is of capital importance. To ascertain with more certainty the presence of hydrophobins on barley and malt and their gushing inducing property, the gushing test mostly often used in practice, the doubly Modified Carlsberg Test, was used but it was followed by a new test based on the detection of CO₂-hydrophobin nanoparticles by Dynamic Light Scattering (DLS). This allowed to certify that the potential of provoking gushing by samples of barley and malt is due to the potential of provoking a primary gushing and the presence of fungal products: hydrophobins. The results showed also that only 5% of gushing provoking grains in the grist is sufficient to induce gushing and the detection of the nanoparticles, typical for primary gushing.

A method combining environmental data extracted from the dissolved oxygen profile of a fed-batch bioreactor and a dynamic discrete Markov chain model has been presented in order to give more insight about the glucose and dissolved oxygen fluctuations experienced by the microorganisms during cultivation in heterogeneous bioreactor. The fed-batch cultivation of Saccharomyces cerevisiae has been performed in a well-mixed and a partitioned scale-down reactor (SDR). The analysis of the environmental sequences has shown extended time lengths for the glucose availability and depletion sequences in the case of the SDR under a DO-controlled fed-batch culture. The Markov chain model developed in this work is able to capture the stochastic environmental events, i.e. in our case the environmental states experienced by the microorganisms crossing the tubular part of the SDR. The simulation results show clearly an extension of the starvation periods in the case of the culture performed in the SDR. The simulations have been performed at the single cells level allowing future improvements of our model and notably in the context of the population segregation phenomena occurring in fed-batch cultures. As a perspective, flow cytometry has been presented as a high-throughput analytical tool for the investigation of yeast physiology at the single cell level and in process-related conditions.

For decades, MBT (3-methyl-2-buten-1-thiol) is known as the compound responsible for the lightstruck off-flavour in beer. This leads many brewers to adapt the procedures by using reduced hop extracts. Unfortunately, other off-flavours including onion-defects often characterize these “light stable” beers. In the present work, a commercial lager beer which did not contain isohumulones (blend of dihydroisoalpha acids; bottled in clear glass) was submitted to various natural aging. Whereas no MBT-defect (skunky-like) was detected by sensorial analyses, a strong “onion-like” off-flavour was evidenced in the samples exposed to light. GC-PFPD and GC-O analyses of global (XAD) and thiol specific (pHMB) extracts allowed us to identify 2-sulphanyl-3-methylbutanol (2S3MBol) as the key-off-flavour (AEDA Flavour Dilution = 32–1024 for 2S3MBol while only 8–64 for MBT). 2S3MBol revealed to be synthesized from 3-methyl-2-buten-1-ol (MBOH) found in hop extracts. The involved radicalar mechanism is strongly enhanced by light. Although reduced hop extracts improve light stability regarding MBT, aroma-extracts give rise to strong onion-like off-flavours in presence of light. The concentration of the hop allylic precursor should be monitored in commercial hop extracts.