Brewing Procedure Research Articles

Antioxidant capacity and phenolic composition of fermented Centella asiatica herbal teas

C. asiatica was exposed to various fermentations: no fermentation (0 min), partial fermentation (120 min) and full fermentation (24 h). Total phenolic content (TPC) and ferric-reducing antioxidant power (FRAP) of C. asiatica infusions were studied as a function of water temperature (60, 80 or 100 °C), the brewing stage (one, two or three) and the brewing time (1, 3, 5, 10, 15 or 20 min). The optimum brewing procedure was adopted to study the antioxidant properties and phenolic compounds in C. asiatica infusions. The optimum extraction efficiency of C. asiatica infusions was achieved at 100 °C after a 10 min brewing time, and decreased substantially after applying multiple brewing steeps. However, no significant different was found between the second and third infusions. The non-fermented C. asiatica (CANF) infusion had the highest antioxidant activity. Gallic acid, naringin, chlorogenic acid, catechin, rutin, rosmarinic acid and quercetin were identified to present. Luteolin and kaempferol were only found in 80% methanol extraction method. C. asiatica herbal teas should be prepared at 100 °C for 10 min to obtain the optimum antioxidant capacity. Multiple brewing steps in C. asiatica herbal tea are encouraged due to the certain amount of antioxidant obtained.

Furan Levels in Coffee As Influenced by Species, Roast Degree, and Brewing Procedures

Brazilian green coffee beans of Coffea arabica and Coffea canephora species were roasted to light, medium, and dark roast degrees and analyzed in relation to furan content by using an in-house validated method based on gas chromatography coupled to mass spectrometry preceded by headspace solid-phase microextraction. Furan was not detected in green coffees, whereas levels between 911 and 5852 μg/kg were found in the roasted samples. Higher concentrations were found in Coffea canephora species and darker ground coffees. Some of the potential furan precursors were observed in significant amounts in green coffee, especially sucrose and linoleic acid, but their concentrations could not be correlated to furan formation. Additionally, coffee brews were prepared from roasted ground coffees by using two different procedures, and furan levels in the beverages varied from <10 to 288 μg/kg. The factor that most influenced the furan content in coffee brew was the brewing procedure.

Tocopherols in coffee brews: Influence of coffee species, roast degree and brewing procedure

Tocopherols in roasted coffee and coffee brews were analysed by HPLC/diode-array/fluorescence detection. Only α and β vitamers were identified in the samples. The influence of several factors on espresso coffee content, as well as on tocopherol extractability, was ascertained, namely, coffee species, roast degree, brew volume and preparation method. Pure arabica espressos contained 2.2 and 3.9 μg of α- and β-tocopherol, respectively, while robusta espressos showed significantly lower amounts ( p < 0.05): 1.3 and 1.1 μg, correspondingly. Total contents (α + β) in espressos prepared from commercial blends ranged from 2.2 to 4.8 μg. Overall, tocopherol amounts in the brews corresponded to only 1% of those found in the coffee cake. However, espressos prepared from servings contained ∼5-fold higher amounts of tocopherol than those prepared by the classic method. The medium-roast degree seems to be more favourable for the extraction of compounds than light or dark roasts. Compared with other coffee beverages, an arabica espresso cup contained an intermediate level of total tocopherols: 7.0 μg/30 mL, against 4.4 μg for filter (150 mL), 13.6 μg for press-pot (60 mL), 19.7 μg for moka (60 mL), 25.4 μg for Turkish, and 40.1 μg for boiled (150 mL) coffees.

Isoflavones in Coffee: Influence of Species, Roast Degree, and Brewing Method

This paper reports the isoflavone contents of roasted coffee beans and brews, as influenced by coffee species, roast degree, and brewing procedure. Total isoflavone level is 6-fold higher in robusta coffees than in arabica ones, mainly due to formononetin. During roasting, the content of isoflavones decreases, whereas their extractability increases (especially for formononetin). Total isoflavones in espresso coffee (30 mL) varied from approximately 40 microg (100% arabica) to approximately 285 microg (100% robusta), with long espressos (70 mL) attaining more than double isoflavones of short ones (20 mL). Espressos (30 mL) prepared from commercial blends contained average amounts of 6, 17, and 78 microg of genistein, daidzein, and formononetin, respectively. Comparison of different brewing methods revealed that espresso contained more isoflavones ( approximately 170 microg/30 mL) than a cup of press-pot coffee ( approximately 130 microg/60 mL), less than a mocha coffee ( approximately 360 microg/60 mL), and amounts similar to those of a filtered coffee cup ( approximately 180 microg/120 mL).

Investigation of shelf-life extension of sorghum beer (C hibuku) by removing the second conversion of malt

The effect of removing the second step of malt conversion in the brewing of Chibuku beer was investigated with the intention of extending the shelf-life of the product. Chibuku was brewed in the laboratory scale fermenters using Delta Beverages' standard brewing procedure. A variation was made where the second malt conversion was not conducted on one brew. The effect of increasing pasteurisation time was also investigated. The extension of shelf-life was determined by following the physicochemical and the sensory profile of the products for a period of ten days under sub-tropical ambient conditions. Ethanol productions were similar between the control and test beers (without second conversion malt). A product with overall acceptability of 70% was made from the brew without the second malt conversion and with 15 min pasteurisation at 80 °C. The product was, however, low in bite and head retention, but had less bacterial load, decreased acid production, and improved keeping quality by at least two days. However, due to contamination of the pitching yeast with lactic acid bacteria (LAB), total acids rapidly increased after 168 h and caused unacceptable sourness. Increasing pasteurisation time to 20 min reduced bacterial load of the wort to figures as low as 2 × 10 3 cfu/ml. General hygiene levels of the brewery were acceptable and no coliforms were detected in the product or contact surfaces along the production line. Bacterial contamination of the product mainly comes from the raw materials with pasteurisation greatly reducing this load. If improved, the procedure has the potential of extending the shelf-life of the beer to beyond 168 h.

Catechin stability of EGC- and EGCG-enriched tea drinks produced by a two-step extraction procedure

Catechin content of green tea drinks commercially available is reported to be very low in comparison with tea traditionally prepared, due to catechins conversion to their corresponding epimers during production. The purpose of this present study was to produce catechin-enriched tea drinks according to a two-step brewing procedure and to verify the catechin stability of those enriched drinks during storage. Those results confirmed that it is possible to produce EGC- and EGCG-enriched tea drinks regardless of the green tea used. Good extraction efficiencies were reached for the first and second extraction steps with catechin extraction yields ranging from 63.6% to 84.8%. Furthermore, it appeared that the catechin content in the two enriched tea drinks demonstrated a great stability since no significant degradation occurred within 8 weeks of storage. This simple two-step extraction procedure could be considered as an interesting way to produce enriched green tea drinks with more potent and stable bioactive catechins.

How Does Roasting Process Influence the Retention of Coffee Aroma Compounds by Lyophilized Coffee Extract?

The aims of this study were (1) to study the effect of lyophilized coffee extract on the retention of aroma compounds and (2) to study if aroma compounds selected are differently affected by the lyophilized coffee extracts obtained from conventional and Torrefacto coffee brews prepared by filter coffeemaker and by espresso coffee machine. Variable amounts of lyophilized coffee extracts, relative to coffee powder, containing different percentages of high molecular weight compounds, mainly melanoidins (value given in parentheses), were obtained: 20.9% (14.8) and 24.9% (23.3), respectively, for conventional and Torrefacto coffee brew prepared by filter coffeemaker and 18.1% (18.8) and 20.7% (57.5), respectively, for conventional and Torrefacto coffee brew prepared by espresso coffee machine. The retention of aroma compounds increased by increasing the lyophilized coffee extract concentration and was found to be dependent on the aroma compounds. The retention of aroma compounds was found to be slightly different depending on the brewing procedure employed, showing lyophilized coffee extracts obtained with espresso coffee machine had higher retention values that those extracted by filter coffeemaker. Retention capacity of lyophilized coffee extracts obtained from the conventional and the Torrefacto roasted coffee did not show differences except in the case of ethyl nonanoate.

Coffee Dietary Fiber Contents and Structural Characteristics As Influenced by Coffee Type and Technological and Brewing Procedures

Coffee brews contain considerable amounts of soluble dietary fiber, mainly low substituted galactomannans and type II arabinogalactans. Factors possibly influencing the content and structures of dietary fiber in coffee brews, such as type of coffee, roasting and grinding degree, and brewing procedure, were studied. In addition, several commercial samples such as instant espresso, instant coffee, instant cappuccino, decaffeinated coffees, and coffee pads were analyzed. The dietary fiber contents of the coffee brews ranged from 0.14 to 0.65 g/100 mL (enzymatic-gravimetric methodology), proving an influence of the factors investigated. For example, the drip brew of an arabica coffee contained significantly more soluble dietary fiber than the drip brew of a comparable robusta coffee, and depending on the brewing procedure, the soluble dietary fiber content of beverages obtained from the same coffee sample ranged from 0.26 to 0.38 g/100 mL. Dietary fiber contents of coffee brews were enhanced only up to a certain degree of roast. Drip brews of decaffeinated arabica coffees (commercial samples) contained significantly less dietary fiber than any non-decaffeinated drip brew investigated in this study. The observed differences in the dietary fiber contents were accompanied by changes in the structural characteristics of fiber polysaccharides, such as galactomannan/arabinogalactan ratio, galactose substitution degree of mannans, or galactose/arabinose ratio of arabinogalactans as analyzed by methylation analysis.

Correlation of Selected Constituents with the Total Antioxidant Capacity of Coffee Beverages: Influence of the Brewing Procedure

Relationships between volatile and nonvolatile compounds and the antioxidant capacity of coffee brews prepared from commercial conventional and torrefacto roasted coffees, employing commonly used doses and prepared by four brewing procedures (filter, plunger, mocha, and espresso machine) were assessed. Significant correlations between volatile Maillard reaction products and antioxidant capacity (measured by both 2,2-diphenyl-1-picrylhydrazyl radical and redox potential methods) were not observed. Highly positive correlations between browned compounds and caffeine with both antioxidant capacity parameters were reported. Principal component analysis allowed coffee brews separation according to coffee roasting processes (PC1) and brewing procedures (PC2), showing that in all cases coffee brews from torrefacto roasted coffee were more antioxidant that those extracted from conventional ones; also, coffee brews extracted by an espresso machine were more antioxidant than those extracted by mocha, plunger, and filter machines.

Production of green tea EGC- and EGCG-enriched fractions by a two-step extraction procedure

The aim of the present work was to test the feasibility of a two-step extraction procedure to fractionate EGCG and EGC from green tea. This work was based on previous observations that there was a variable interdependence between the brewing duration and the brewing temperature on catechin concentrations: EGC being a time-dependent compound while EGCG being a time/temperature-dependent compound. It appeared from these results that it was possible to produce from green tea, on a simple way with adding no organic solvent, an EGC-enriched extract (78.9% total catechins) in the first step and an EGCG-enriched extract (47.6% total catechins) in the second step. The two-step brewing procedure based on the temperature-dependent solubilization of both major catechins, EGC and EGCG, allowed the production of such extracts by decreasing ash and EGC contents during the second step extraction.

Changes in Headspace Volatile Concentrations of Coffee Brews Caused by the Roasting Process and the Brewing Procedure

Headspace-solid-phase microextraction technique (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O) were used to characterize the aroma compounds of coffee brews from commercial conventional and torrefacto roasted coffee prepared by filter coffeemaker and espresso machine. A total of 47 volatile compounds were identified and quantified. Principal component analysis (PCA) was applied to differentiate coffee brew samples by volatile compounds. Conventional and torrefacto roasted coffee brews were separated successfully by principal component 1 (68.5% of variance), and filter and espresso ones were separated by principal component 2 (19.5% of variance). By GC olfactometry, a total of 34 aroma compounds have been perceived at least in half of the coffee extracts and among them 28 were identified, among which octanal was identified for the first time as a contributor to coffee brew aroma.

Molecular marker-assisted selection for enhanced yield in malting barley

Brewers are reluctant to change malting barley (Hordeum vulgare ssp. vulgare L.) cultivars due to concerns of altered flavor and brewing procedures. The U.S. Pacific Northwest is capable of producing high yielding, high quality malting barley but lacks adapted cultivars with desirable malting characteristics. Our goal was to develop high yielding near isogenic lines that maintain traditional malting quality characteristics by transferring quantitative trait loci (QTL) associated with yield, via molecular marker-assisted backcrossing, from the high yielding cv. Baronesse to the North American two-row malting barley industry standard cv. Harrington. For transfer, we targeted Baronesse chromosome 2HL and 3HL fragments presumed to contain QTL that affect yield. Analysis of genotype and yield data suggests that QTL reside at two regions, one on 2HL (ABG461C-MWG699) and one on 3HL (MWG571A-MWG961). Genotype and yield data indicate that additional Baronesse genome regions are probably involved, but need to be more precisely defined. Based on yield trials conducted over 22 environments and malting analyses from 6 environments, we selected one isogenic line (00-170) that has consistently produced yields equal to Baronesse while maintaining a Harrington-like malting quality profile. We conclude there is sufficient data to warrant experiments testing whether the 2HL and 3HL Baronesse QTL would be effective in increasing the yield of other low yielding barley cultivars.

Application of Immunological Methods to Differentiate between Foam-Positive and Haze-Active Proteins Originating from Malt

Beer foam and storage haze stability are of critical importance to brewers because they are among the first characteristics by which a consumer judges the quality of his or her beer. Key malt-derived, foam-positive proteins, including protein Z4, lipid transfer protein 1 (LTP1), and some members of the hordein storage protein family, interact principally with hop acids to stabilize foam. Silica-mediated beer stabilization procedures remove haze-active protein with high levels of proline (>30%) and glutamine (>30%), suggestive of a hordein origin, without reducing foam stability. Polyclonal antibodies to protein fractions of enriched beer foam proteins and proteins extracted from silica used for beer stabilization were developed. The antibodies were found to measure different malt-derived proteins. The antibodies were subsequently used to select foam-positive and haze-active hordein-recognizing monoclonal antibodies, which enabled the development of enzyme-linked immunosorbent assays (ELISAs). The ELISAs and immunochemical procedures were applied to predict beer foam and haze quality from malt used to brew beer by using pilot- (50 L) and small-scale (0.6–0.8 L) brewing procedures. It is anticipated that the immunochemical methods may be applied to select and manipulate malt for brewing to improve beer foam stability while reducing the likelihood of storage haze formation.

Beer Polypeptides and Silica Gel Part I. Polypeptides Involved in Haze Formation

Beer contains approximately 500 mg/L protein depending on the brewing procedures employed. This protein is in the form of polypeptides, the majority of which lie within the 10–40 kD size range. Some of these polypeptides are responsible for causing colloidal haze, others enhance foam stability and the remainder appear to have no function in beer except to contribute to mouth-feel. The polypeptides responsible for haze formation are those that can combine with polyphenols to produce a visible cloudy haze. This is undesirable as it can have a negative effect on the beer's shelf life. One way to reduce this effect is to remove these polypeptides using silica gels. It is important that this removal is selective, and the desirable foam enhancing polypeptides are not removed. Data will be presented to show that beer polypeptides are glycosylated and that silica preferentially adsorbs glycoproteins, particularly those with protein components rich in the amino acid proline. The molecular size and composition of glycoproteins recovered from untreated beer, cooked adjunct, silica exposed to beer and beer aged for one year are presented. Glycoproteins involved in foam, and the apparently functionless polypeptides, will be discussed in a subsequent paper.

Stability of zearalenone in naturally contaminated corn during Nigerian traditional brewing

The extent of carryover of zearalenone in mouldy substrate guinea-corn into native beer, burukutu, was determined using a laboratory adaptation of the traditional brewing procedure. Mean zearalenone carryover into finished product was 51.4 +/- 7.3% of that in the starting mixture, suggesting a moderate stability. Some 12.1 +/- 3.3% was removed with discarded solid residue.

New Methods for the Evaluation of Barley and Malt

The frequent appearance on the French market of new barley varieties, especially two-row and six-row winter types, has caused some delays in adapting malting and brewing procedures. Malting studies with several quantities (10 and 250 g; 2 and 300 kg) of barley have been conducted, and evaluations were made of malt at various malting times. Some of these malts were tested by microbrewing (7 L) and by pilot scale (2,000 L) brewing. The methods of Aalbers/Greif (methylene blue) and of Carlsberg (Calcofluor) were used to measure the modification and the homogeneity of malts. The InfraAlyzer was used to measure modification, but this method does not measure homogeneity. The TEPRAL mashing system was also used. Its advantage is that in addition to the determination of extract, other parameters of industrial importance are measured. The close relationship between filtrability of the TEPRAL mash and filtrability of beer is discussed. The application of these new analytical methods allows better evaluation of barleys and of malts prepared at micro, pilot, and industrial scales.

New Methods for the Evaluation of Barley and Malt

The frequent appearance on the French market of new barley varieties, especially two-row and six-row winter types, has caused some delays in adapting malting and brewing procedures. Malting studies with several quantities (10 and 250 g; 2 and 300 kg) of barley have been conducted, and evaluations were made of malt at various malting times. Some of these malts were tested by microbrewing (7 L) and by pilot scale (2,000 L) brewing. The methods of Aalbers/Greif (methylene blue) and of Carlsberg (Calcofluor) were used to measure the modification and the homogeneity of malts. The InfraAlyzer was used to measure modification, but this method does not measure homogeneity. The TEPRAL mashing system was also used. Its advantage is that in addition to the determination of extract, other parameters of industrial importance are measured. The close relationship between filtrability of the TEPRAL mash and filtrability of beer is discussed. The application of these new analytical methods allows better evaluation of barleys and of malts prepared at micro, pilot, and industrial scales.

Degradation of starch by amylases in beer brewing.

In the beer brewing industry throughout the world about 8 × 106 tons of starch is annually converted into fermentable sugars and dextrins. Determining factors for the degradation of starch are the conditions of mashing and the action pattern of the amylases, α-amylase and β-amylase. Although present in germinating barley and in barley malt, α-glucosidase and debranching enzyme (plant pullulanase) exert little action in normal brewing procedures. Accordingly, the majority of the α-1, 6 linkages in amylopectin survive the brewing process. In a series of studies the formation and the composition of the dextrins present in beer wort have been examined by enzymic methods and quantitative gel filtration chromatography. The results show:-About 75% of the starch degradation products are glucose, maltose, and maltotriose. The remaining 25% constitutes the unf ermentable residue, generally known as dextrins.-About half of the dextrins consists of oligosaccharides with less than 10 glucose units, either linear or singly-branched.-About half of the dextrins contains 10 or more glucose units per molecule and may be termed megalosaccharides. These dextrins are multiply-branched.-The weight of the dextrins versus their molecular weight exhibits a characteristic pattern for which the term wavy distribution has been coined, inter alia to indicate that the dextrins in wort and beer seem to fall into distinct groups. Subsequent structural analysis has revealed that these groups of dextrins are characterized by their number of α-1, 6 linkages.-The multiply-branched dextrins in wort and beer represent structural entities of dense branching in the original amylopectin (starch) molecules. Thus the study of dextrins in brewing also provides information of the fine structure of starch. Based on these findings a model for the degradation of starch in beer brewing by a-amylase and β-amylase will be proposed.