Food industries are interested in finding highly stable foaming agents for product texture improvements. Hydrophobins have been mentioned many times in that context. For the production and purification of hydrophobin HFBII from Trichoderma reesei we found that foam fractionation of the fungal fermentation media is an interesting first step. After this step, the biophysical properties of the obtained foamate were studied. The foam generated by CO2 as the only sparging gas into a HFBII enriched solution in a closed environment was more stable than the foam generated by sparging with air. The equilibrium surface tension of a foamate containing 100mg/L HFBII was measured by CAMTEL CDCA-100 tensiometry as equal to 40mJ/m2, and was confirmed by the maximum bubble pressure tensiometer. Besides, it was found that for a long term foam preservation, the foam created by the HFBII-SDS combination is more stable than that of SDS.
Amidst the rising popularity of craft beers, it would be opportune to develop a novel, unfiltered and unpasteurized sour beer with high probiotic live counts. However, as beer typically contains hop iso-α-acids that prevent the growth and survival of probiotic lactic acid bacteria, the use of suitable fermentation strategies is crucial. The growth, and survival of the probiotic bacterium, Lactobacillus paracasei L26, were assessed during a 10-day co-fermentation period with a brewer's yeast, Saccharomyces cerevisiae S-04, in unhopped wort. Isomerized hop extract was added prior to storage of the beers at 25 °C and 5 °C. During co-fermentation in unhopped wort, L. paracasei L26 maintained high viable cell counts above 8 Log CFU/mL, indicating species compatibility with the yeast. The majority of fermentable sugars were attenuated by S. cerevisiae S-04, with a concomitant production of alcohols and esters. Significant amounts of lactic acid were produced by L. paracasei L26 (P < 0.05). During storage with added isomerized hop extract, maximal probiotic viability enhancing effects were observed in the presence of live S. cerevisiae S-04, in combination with refrigeration. The results suggest that beers could be a vehicle for probiotic delivery under appropriate conditions. This was the first study demonstrating the feasibility of utilizing probiotic lactobacilli as starter cultures in beer brewing.
Nous relations récemment combien l’information abondante relative aux voies de formation des thiols polyfonctionnels du vin pouvait aider le brasseur à optimiser les arômes citronnés ou exotiques de sa bière (Gros et al., 2011, Gros et al., 2012, Gros et al., 2013a, Gros et al., 2013b, Nizet et al., 2013). Les analogies sont nombreuses entre ces deux matrices et tant les œnologues que les brasseurs peuvent tirer profit de cette complémentarité.
Large-scale production of yeast (Saccharomyces cerevisiae) is difficult to control, considering the drop of mixing and mass transfer efficiency during scale-up. The drop of hydrodynamic efficiency in large-scale bioreactors induces the formation of heterogeneities, i.e. mainly substrate and dissolved oxygen in process conditions. These extracellular fluctuations have several impacts at the level of the physiology of microorganisms, from metabolic shift to specific gene expression (stress response). Microbial cell responses to extracellular fluctuations are actually not fully understood. In this work, we propose to reproduce the main extracellular fluctuations at the level of a mini bioreactor platform. These mini-reactors are shake flasks equipped with dissolved oxygen probes. The cultures are realized with different fed-batch control strategies. A scale-down approach has been developed by considering slow release techniques and intermittent feeding, in order to reproduce the glucose and dissolved oxygen fluctuations experienced in large-scale reactors. The mini-reactor has been used to screen the response of several green fluorescent protein (GFP) reporter strains (adh2, tps2, pdc6 and hxt2). The GFP content of cells has been determined by flow cytometry in order to take into account population heterogeneity. In front of these results, the methodology presented in this work can be proposed as a scale-down tool.
The brewing industry is facing an ever increasing challenge to become more cost-effective, while at the same time maintaining or improving product quality. Brewing with unmalted oats (Avena saliva L.) has the potential to reduce the costs of raw materials. However, the replacement of malted barley with unmalted oats can also adversely affect the quality and processability of mashes, worts, and beers. In this study, brewing with unmalted oats (0-40%) and malted barley was carried out in a 60-L pilot plant. The impact of various levels of oats on mashing, lautering, and fermentation performance was monitored in detail and the quality of the final beers was evaluated using Lab-on-a-Chip capillary electrophoresis as well as standard methods specified by Mitteleuropaische Brautechnische Analysenkommission (MEBAK), European Brewery Convention (EBC), or the American Society of Brewing Chemists (ASBC). It has been found that the P-glucan content and viscosity of mashes and worts increased significantly with increasing amounts of oats. In addition, the use of 20% or more oat adjunct resulted in a clearly increased lautering time. The replacement of barley malt with unmalted oats also had adverse effects on total soluble nitrogen (TSN), free amino nitrogen (FAN), and extract levels in worts. The foam stability of the final beers decreased significantly using 20% oats or more. However, their sensory quality improved with increasing levels of oat adjunct.
Several hundred samples of barleys and corresponding pilot scale malts were analyzed for eight barley parameters and 15 malt parameters. Principal components analysis (PCA) was applied to the barley and malt data sets. The barley data had three significant PCs, corresponding to kernel size, germination rate and protein content, and moisture. The malt data had 5 significant components, largely corresponding to modification, extract, enzyme activity, nitrogenous substances, and wort pH. Pattern recognition of the barley and malt data sets was carried out with Linear Discriminant Analysis (LDA), k-Nearest Neighbor analysis (k-NN) and SIMCA. Classification of the barley samples into 2- or 6-row, winter or spring, origin country and cultivar was fairly successful. Classification of the malt samples into hulled or hull-less barleys, country of origin, and cultivar was quite successful; classification by crop year and 2- or 6-row barley was less successful. Models of malt parameters as a function of multiple barley measurements were constructed using partial least squares regression (PLSR). An excellent model of malt total protein (R2 = 0.74) was obtained. Fair models of friability, fine and coarse extract, soluble protein, Kolbach index, diastatic power and α-amylase activity were produced. Only poor models of the other parameters were obtained.
J. Am. Soc. Brew. Chem. 70(4):275-279, 2012 The evolution of polypeptide profiles during three successive fermentations with yeast generation N0, N+1, and N+2 was examined under large scale brewing conditions using 1,000 and 3,000 hL cylindroconical vessels, coded as G and H, respectively. ANOVA analyses indicated that the total protein content decreased significantly from wort (before yeast pitching) to green beer (samples collected after 2, 4, 6, 8, and 10 days of fermentation), and in general increased from green beer to mature beer (collected during beer conditioning after 12 and 14 days of yeast addition). Polypeptides from wort, green beer, and mature beer (without further treatments) were separated by chromatography according to their molecular size and by RP-HPLC. Quantitative differences were observed in peak areas, indicating the polypeptide, peptide, and amino acid changes throughout the fermentation and conditioning processes due to foam formation, protein precipitation, and yeast metabolism. A MANOVA was performed using RP-HPLC profile of beer from N0, N+1, and N+2 yeast generations produced in G and H fermentation vessels to establish the effect of vessel size and yeast generation. F values indicated greater importance of the yeast generation than the vessel size on the beer polypeptide profile. Yeast generation effect was notable in generation NO. Beer produced with generations N+1 and N+2 in the two cylindroconical vessels gave similar polypeptide profiles.
Sensory descriptive analysis and free choice profiling have been applied to the characterization of aroma in thirteen hop varieties, both in the whole cone form and after the hops had been used to dry hop beer. 180 terms were identified and used for the classification of hops. Only two of the varieties displayed closely similar profiles. Varieties could, however, be broadly grouped into those with overriding citrus notes and those with substantial green tea, hay and wet wood nature. Dry hopping tends to compress varieties when evaluated for aroma, perhaps indicating a degree of masking by other beer components. However the aroma notes detected are similar whether assessed in whole cones or in beers.
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.
Les micro-organismes sont utilisés dans de nombreux domaines (agro-alimentaire, pharmaceutique, environnemental, énergétique,…) que ce soit pour la production de biomasse ou de métabolites particuliers. Le passage de l’échelle du laboratoire à l’échelle industrielle est souvent problématique car les micro-organismes sont sensibles aux conditions environnementales développées au sein du volume réactionnel. De plus, la perte de l’efficacité d’homogénéisation des bioréacteurs industriels entraîne des perturbations au niveau du métabolisme des cellules. C’est pourquoi il est important d’étudier les conditions hydrodynamiques développées au sein du réacteur. Cet article présente des méthodes de calcul et de modélisation de ces conditions. L’impact de l’hydrodynamique sur le métabolisme microbien peut être étudié par l’utilisation de réacteurs scale-down. Les techniques nouvelles permettant de réaliser un scale-up prennent en compte des caractères physiologiques des cellules, qui estiment l’impact des conditions environnementales sur le métabolisme microbien et donc la bonne réussite du procédé. Enfin, l’étude de Saccharomyces cerevisiae, micro-organisme de grand intérêt biotechnologique, est réalisée.
The presence of Class II hydrophobins produced by fungi on barley results in primary gushing of beer. Gushing is the spontaneous overfoaming of carbonated beverages by opening of bottles. Solving gushing problems caused by brewing raw materials has received much scientific attention. Lipophilic extract of hops are introduced to brewers as foam suppressor in fermenters. We studied the effects of hop extract on gushing and found that lipophilic hop extract could reduce gushing. The effects are different when hop extract is added before mashing than when it is added after mashing. Hop extract contains fats and waxes and the effects on gushing are explained by a change in the physical state of its components during mashing which are due to temperature effects. Especially the effect of saturated fatty acids and waxes becomes apparent which are known as gushing inducers. This indicates that with respect to gushing potential of the hop extract's components, it is better to be added to cold wort (after mashing and filtration). Our study also showed an important effect of the filtration step on the amount of gushing.
A method was developed for quantification of sulfite in beer based on derivatization with the maleimide-derived probe ThioGlo 1 followed by separation of fluorescent adducts by reversed-phase high-performance liquid chromatography and fluorescence detection. Sulfite gave two ThioGlo 1 derivatives and it was shown by mass spectrometry that both had identical mass spectra. Matrix effects were observed when constructing sulfite standard curves in different beers and, therefore, use of a matrix-matched calibration curve is proposed. ThioGlo 1 was found to generate fluorescent adducts with both bound and free sulfite, providing a quantification of the total sulfite content in beer. The limit of quantification of sulfite was 0.6 mg/L and the method can be used for quantification of sulfite in highly colored beers.
Although chronic exposure to alcohol or its contaminants is the main carcinogenic risk factor in the high prevalence of hepatic cancers, information on the mutagenicity of Soju alcoholic spirits is limited. Presently, the mutagenicity of Soju was tested using the Ames test. Evaporation residues of 11 common brands of Soju were examined and four of the 11 brands displayed a mutagenic response in the TA98-based Ames test without S9 liver extract. Moreover, among these positive samples, two had mutagenic activity in both TA98- and TA100-based Ames tests with S9 liver extract. Some samples of Ames test-positivity also contained N-nitrosodimethylamine or N-acetoxy-2-acetylaminofluorene, implicating potential etiologic factors for the Ames test.
J. Am. Soc. Brew. Chem. 70(1):29-34, 2012 A modified de Man-Rogosa-Sharpe (MRS) medium suitable for easy, fast, and specific detection of beer-spoilage bacteria Pectinatus spp. from beer and brewery swab samples was developed. It contains readily commercially available MRS broth, cysteine hydrochloride, and sodium thioglycolate as compounds lowering the redox potential of the medium, Tetra (a mixture of tetrahydroiso-alpha-acids) and 2-phenylethanol as the specificity-ensuring components, and bacteriological agar, which prevents medium oxidation during sample manipulation and transport. Tests with beer and brewery isolates of Pectinatus frisingensis, P. cerevisiiphilus, P. haikarae, Lactobacillus brevis, L. paracasei, L. plantarum, Lactococcus lactis, Pediococcus damnosus, and brewery strains of Saccharomyces pastorianus and S. cerevisiae showed that the medium does not inhibit the growth of Pectinatus spp. yet suppresses the growth of other beer- and brewery-contaminating microorganisms, which, thus, do not interfere with Pectinatus determination. The characteristic and easy-to-detect snake-like motile cells of Pectinatus spp. appear after a 24-to-48 hr cultivation of samples in MRS medium with Tetra.
The volumetric productivity of the beer fermentation process can be increased by using a higher pitching rate (i.e., higher inoculum level). Next to this, high-gravity brewing has become a standard strategy for brewers to increase their productivity. However, both technologies can have a significant effect on yeast metabolism. In this study, high-gravity and high-cell-density fermentations were combined, and their impact on yeast physiology and flavor compound production was evaluated. Additionally, an attempt was made to decrease the production of total diacetyl during accelerated fermentation systems by optimization of the free amino nitrogen content of the wort. Higher wort density resulted in decreased yeast viability, which correlated to increased expression levels of stress-related genes and higher levels of trehalose. More than wort density, the relative amounts of different assimilable sugars have a drastic effect on both yeast fermentation performance and flavor compound production. Worts with high amounts of sucrose had a stimulating effect on the uptake of amino acids, yeast growth, glycogen formation, recycling of trehalose, ethyl ester synthesis, and the turnover rate of total diacetyl. Yeast exposed to high levels of sucrose experienced more osmotic stress and stress related to stationary phase than other high-gravity worts. Although sucrose, compared with maltose, had a stimulating effect on ATFl expression, a remarkable decrease in acetate esters was observed. Considering the adverse effects of sucrose on the yeast performance, it is advisable to avoid high concentrations of these fast-food sugars and to use a combination of sucrose and maltose syrups as a way to increase the wort density.
J. Am. Soc. Brew. Chem. 70(1):35-38, 2012 Beer is derived from grist materials that contain gluten-type protein; therefore, it has long been assumed that it should not be consumed by those with celiac disease. However, because a significant objective of the malting and brewing process is protein precipitation and modification, beer may be rendered low in gluten from these processes alone. The levels of prolamin have been monitored throughout the brewing process with the RIDASCREEN Gliadin competitive R5 enzyme-linked immunosorbent assay method. The barley malt contained 6,832.3 +/- 61 mg/kg, but only 131.1 +/- 1 mg/kg of prolamin remained after fermentation. Addition of prolyl endoproteinase lowered the level of prolamin still further, to levels below the reliable limit of detection. A significant difference in foam stability was observed between the control and the prolyl endoproteinase-treated gluten-free beer, but no other beers were significantly affected by the addition of this enzyme.
For decades, kieselguhr has been the most common filter aid for beer filtration. However, costs for disposal are severely increasing and brewers today are concerned about replacing kieselguhr filtration by a greener technology. Filtration trials were carried out with the regenerable filter aid oxidized high-density polyethylene (OxPE) on a pilot-scale candle filter using green lager beer from settling tanks. OxPE has an average particle size distribution of 37 μm and its outer surface presents nodular structures. The porosity of the OxPE media is 0.6 compared with 0.85 for kieselguhr. OxPE retains a good amount of haze and yeast cells without clogging; however, the expected clarity was reached only when using Brewtan. The use of polyvinyl-polypyrrolidone (PVPP) mixed with the OxPE filter aid (25/75%) showed the best results for filtration because of the shape of PVPP particles and their slight compressibility. Regeneration is one of the most important steps to achieve because the filter aid has to be reused as many times as possible while keeping its properties of retention toward haze and yeast cells. OxPE proved to have very good resistance to aggressive regeneration conditions, and filtration trials carried out after such an operation confirmed this.
Because of epidemics of Fusarium head blight (FHB; caused by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.) Petch]) in the northern Great Plains of the United States and Canada in the past two decades, malting barley breeders have been forced to use nonadapted barley (Hordeum vulgare L.) accessions as sources of FHB resistance. Many of the resistant accessions are from East Asia, and limited information is available on their genetic diversity and malt quality. The objectives of this study were to determine the genetic diversity among 30 East Asian accessions and two North American cultivars. Genetic diversity was based on 49 simple-sequence repeat markers. All accessions were tested for barley grain brightness; protein content; 1,000-kernel weight; malting loss; fine-grind malt extract; content of plump kernels, free amino nitrogen, soluble protein, and wort β-glucan; the Kolbach index (i.e., the ratio of malt soluble protein to malt total protein); α-amylase activity; diastatic power; wort color; and wort viscosity. A few accessions had equal quality compared with Harrington and Conlon barley for individual traits but not for all. Qing 2, Mokkei 93–78, and Nitakia 48 could be excellent sources for increased malt extract; Nitakia 48 is a possible source for low wort viscosity; and Mokkei 93–78 and Nitakia 48 are putative sources of low β-glucan content. The cluster analyses also implied that the malt quality of an accession cannot be predicted based on the country where it was developed.
