ABSTRACT
The application of the Rapid Visco Analyser (RVA) as a laboratory scale rheological tool for the characterisation of mash viscosity is the subject of this study. Studies were conducted to ...simulate an industrial mashing process, taking into account temperature/time, grist loads, adjunct amounts and enzyme levels. The RVA was used to characterise the effects of different ratios of malt: barley adjunct. The method was found to have the ability of not only detecting the major viscosity changes which occur during starch gelatinisation/liquefaction processes, but also the minor viscosity changes which were found to occur during the proteolytic and saccharification steps. Clear correlations were found between the level of barley adjunct and the output rheological data points of the peak viscosity at 50°C (PV50, R2 = 0.9931), the rate of viscosity breakdown at 50°C (BR50, R2 = 0.9522), the peak viscosity prior to gelatinisation (PVG, R2 = 0.9988), the area recorded under the gelatinisation curve (PGA, R2 = 0.9928) and the peak viscosity breakdown rate (VBR, R2 = 0.9783). The developed RVA rheological method is a useful tool for characterising grain quality (adjunct level) with regard to macromolecular viscosity compounds and the grains endogenous enzymatic capabilities.
ABSTRACT
In this study four strains of lactic acid bacteria (LAB) were chosen to bioacidify a mash containing 50% barley and 50% malt. The strains were isolated from malted and unmalted barley and ...assayed for extracellular enzymatic activities (proteases, amylases, β‐glucanases). The biologically acidified mash was compared to a chemically acidified mash, 100% malt mash un‐acidified and 50% malt and 50% barley mash unacidified. Characteristics such as pH, extract, colour, viscosity, total soluble nitrogen (TSN), free amino nitrogen (FAN), apparent fermentability, β‐glucan and lautering performance of the resultant worts were determined. A model lautering system replicating one used in a brewery was designed and built in University College Cork (UCC) to measure the lautering performance of the bioacidified mashes. The new system was compared to the filtration method used in EBC method 4.5.1. Overall the addition of LAB to bioacidify a mash of 50% barley and 50% malt resulted in faster filtration times, which correlated with decreased β‐glucan levels. Proteolytic LAB had a positive influence on the quality of wort and resulted in increased FAN levels. Lighter colour worts were observed along with increased extract levels.
ABSTRACT
This paper reports on the application of a previously published laboratory scale rheological method to understand the effects that amylase addition and pH adjustment have on the rheological ...changes, which are taking place during the brewery mashing process. Clear correlations were found between the level of amylase present in mashes and the rheological data points representing primary grain/starch swelling (PVG, R2 = 0.9821) and subsequent starch digestibility (BR44, R2 = 0.9751). In addition, secondary starch gelatinisation rheological data representing viscosity increases due to the presence of smaller starch granules were clearly correlated with the level of mash amylase (VG2D, R2 = 0.9882). The influence of mash pH on starch gelatinisation/breakdown and amylase activities could be quantified from the rheological data. Overall, the studies clearly show how grain components, amylolytic enzymes and mash pH collectively influence the viscosity profiles during the mashing process. In addition, application of the method can provide the maltster/brewer/distiller with more functional information regarding raw materials and process conditions.
ABSTRACT
In this study three strains of lactic acid bacteria were applied during the malting process to evaluate the impact on malt and wort quality. The trials were performed in a micromalting plant ...simulating an industrial malting programme. The samples were compared to chemically acidified as well as non‐acidified malt. Bacterial cultures were chosen with reference to their enzymatic (proteolytic/amylolytic) activity, or their good acidifying properties. The effects of lactic acid bacteria on wort characteristics were investigated and compared to wort produced from 100% unacidified malt. A chemical food grade lactic acid was also used to acidify the barley for comparison purposes. Characteristics such as pH, extract, colour, viscosity, total soluble nitrogen, free amino nitrogen, apparent fermentability, β‐glucan and lautering performance of the resultant worts were determined. Results showed improved levels of β‐glucanase in the malt although reduced malt friability was observed where LAB was employed. An improved lautering performance, lower wort viscosity and elevated TSN levels were also reported where LAB exhibiting protease activity were applied.
Nisin, in the form of the commercial product Nisaplin, and lacticin 3147 in whey powdered form were added to minced pork-meat in amounts of 0.15% (w/w) and 1.5% (w/w), respectively. The meat was ...cooked and inoculated with a Staphylococcus aureus strain of meat origin and a Listeria innocua strain at a level of 10^sup 7^ or 10^sup 5^ CFU g^sup -1^. The batches were stored vacuum-packaged for 21 days at 8 °C. Nisin and lacticin 3147 immediately reduced the L. innocua population at the time of inoculation. Nisin showed higher inhibitory activity than lacticin 3147. During the storage period, a slight L. innocua growth was observed in the batches inoculated with the larger inoculum, and a bacteriostatic effect was observed against Listeria in the batches inoculated with 10^sup 5^ CFU g^sup -1^. Nisin maintained a constant S. aureus population in the cooked batch inoculated with 10^sup 7^ CFU g^sup -1^, although the bacteriocin was capable of reducing the amount of S. aureus by 90% in the batch inoculated with 10^sup 5^ CFU g^sup -1^. On the other hand, lacticin 3147 did not show an inhibitory effect against S. aureus in the cooked meat. The starter culture Lactococcus lactis DPC 303-T4 (containing the conjugative plasmid encoding production of lacticin 3147) was inoculated in a portion of a Longissimus dorsi pork muscle with brine. L. lactis DPC 303-T4 performed a good fermentation, but lacticin 3147 production was not found after 7 days at 12 °C of storage.PUBLICATION ABSTRACT
This study investigates the effects of lactic acid bacteria (LAB) added concomitantly to barley infected with fungal spores or mycelia of Fusarium culmorum TMW 4.0754. The trials were performed in a ...micromalting plant simulating an industrial malting program. Malt samples were compared with those of nonacidified barley, disinfected nonacidified barley, chemically acidified barley, and barley with additional modified DeMan-Rogosa-Sharpe 4 medium. All control samples had fungal spores and fungal mycelia added. Bacterial cultures were chosen as a result of their enzymatic (proteolytic/amylolytic) activity level or their good acidification properties. The effects of the LAB and Fusarium-infected malts on wort characteristics were investigated. Characteristics such as pH, extract, color, viscosity, total soluble nitrogen (TSN), free amino nitrogen (FAN), apparent fermentability, and lautering performance of the resultant worts were determined. Results showed that spores of F. culmorum TMW 4.0754 do not affect the quality of malt or wort. The quality of wort was reduced when mycelia of F. culmorum were applied in the presence of LAB or chemical lactic acid leading to slower filtration rates, lower extract, fermentability, TSN, and FAN yields along with higher viscosity levels. These effects seemed to depend mainly on the presence of mycelia together with the content of lactic acid present.
This study evaluates the influence of biological mash and wort acidification using a thermophilic proteolytic/amylolytic active Lactobacillus amylovorus on brews containing 20% (wt/wt) unmalted ...barley in laboratory-scale trials as well as 10-hL pilot-scale brews. The biologically acidified mash was compared with a chemically acidified mash, 100% malt mash unacidified, and 80% malt (wt/wt)/20% (wt/wt) barley unacidified mash. Characteristics such as pH, extract, color, viscosity, total soluble nitrogen (TSN), free amino nitrogen (FAN), apparent fermentability, β-glucan, sugar, and amino acid profiles of the resultant worts were determined. In the pilot-scale brews, foam stability, accelerated shelf life, and sensory evaluation of the beer was determined. It was clearly shown that biological acidification (BA) could compensate for a lower enzymatic activity level of grists containing 20% (wt/wt) barley. Increased levels of extract, fermentability, TSN, and FAN were observed in the laboratory-mash trials along with a sharp decrease in β-glucan levels when BA was applied. Cast-out wort showed a considerable increase in nitrogenous fractions. Viscosity was decreased by acidification of mashes but did not correlate with β-glucan levels. The final biologically acidified beer showed a lighter color, improved foam stability, and a more well-rounded taste with increased shelf life in comparison with the chemically and the nonacidified beer.
This paper reports on the application of a previously published laboratory scale rheological method to understand the effects that amylase addition and pH adjustment have on the rheological changes, ...which are taking place during the brewery mashing process. Clear correlations were found between the level of amylase present in mashes and the rheological data points representing primary grain/starch swelling (PVG, R2 = 0.9821) and subsequent starch digestibility (BR44, R2 = 0.9751). In addition, secondary starch gelatinisation rheological data representing viscosity increases due to the presence of smaller starch granules were clearly correlated with the level of mash amylase (VG2D, R2 = 0.9882). The influence of mash pH on starch gelatinisation/breakdown and amylase activities could be quantified from the rheological data. Overall, the studies clearly show how grain components, amylolytic enzymes and mash pH collectively influence the viscosity profiles during the mashing process. In addition, application of the method can provide the maltster/ brewer/distiller with more functional information regarding raw materials and process conditions.
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