The Biological Impact of Flash Pasteurization Over a Wide Temperature Interval*

Trials on the impact of flash pasteurization on beer quality showed that higher pasteurization temperatures with shorter holding times are favourable for beer quality. However, the killing effect in the temperature range up to 90°C has not been elucidated so far. Pasteurization temperatures of 50°; 60°; 72°; 84° and 90°C and pasteurization units of 0; 15; 80 and 500 PU were used. The associated residence times were calculated according to Del Vecchio et al.'s formula. The experiments with beer‐relevant yeasts and bacteria showed that Saccharomyces yeasts are much easier to inactivate than Lactobacilli and Pediococci. Furthermore, it can be stated that the commonly used PU calculation according to Del Vecchio reflects the actual killing characteristics in the temperature range from 60° to 72°C quite precisely. Although flash pasteurization with low PU figures at temperatures higher than 72°C and with very high amounts of bacteria may be insufficient, because the real inactivation effect is lower than indicated, there is no need to increase the PU load when changing to higher pasteurization temperatures and shorter holding times in practical application.     

A STUDY OF BEER STALING USING CHEMILUNINESCENCE ANALYSIS

The chemiluninescence (CL) analysis has been used to study beer staling. Several types of commercial Japanese beers were stored at 37°C and their CL development analysed at 60°C. The CL level in beer developed as the beer was stored to reach a maximum level and then decreased. The sum of the CL intensities for the first 1 hour showed a good relationship with staling degree as assessed in mean panel scores. It is postulated that the deterioration rates of beers might be assessed from the CL producing patterns in the fresh beers before storage. The presence of sulfite in beer depressed the CL production during its storage indicating that there is some contribution of sulfite to flavour stability due to its inhibitory effect on radical reactions in beer.     

Evaluation of Beer Deterioration by Chemiluminescence

The application of chemiluminescence (CL) analysis for the evaluation of staling beer was studied. Commercial Japanese lager beer was stored at 30°C, 37°C, and 60°C and its CL generation was analyzed at 60°C. The CL production was accelerated to a greater degree and its intensity reached maximum level more rapidly with increase in incubation temperature and/or time. The sum of the CL intensity for the first 1 hr showed a good relationship with staling degree in mean flavor panel scores. Therefore, CL determination may be useful for evaluating oxidation deterioration of beer.     

A study on kinetics of beer ageing and development of methods for predicting the time to detection of flavour changes in beer

The kinetics of beer ageing were studied based on the development of beer stale flavour with storage time. Results showed that the beer ageing rates at 50 and 60°C were 30.0 and 56 times as fast as those at room temperature, respectively. Based on these findings, two methods (method A and B) for predicting the ‘time to detection of flavour change’ (TDFC) of beer were developed. TDFC is the beer shelf‐life in terms of flavour stability. In method A, beers were stored in a 50°C water bath and the intensity of beer ageing was scored daily. Thus, the range of TDFC of the beer was acquired according to the maximum number of days within which the intensity of beer ageing was ≤2 and the minimum number of days within which the intensity of beer ageing was >2. In method B, the 2‐thiobarbituric acid (TBA) values of a beer were determined before and after 1 day of storage in a 50°C water bath, and the TDFC of the beer was calculated using the equation: where ΔTBA is the increment of TBA value during 1 day of storage at 50°C. Both methods were simple, rapid and accurate. Copyright © 2015 The Institute of Brewing & Distilling     

Effect of high hydrostatic pressure on quality parameters of lager beer

Unpasteurized lager beer samples from a commercial brewery were treated either by high hydrostatic pressure (HHP; 200, 250, 300, 350 MPa for 3 and 5 min at 20 °C) or by conventional heat pasteurization (60 °C for 15 min). The main attributes of the beer, such as ethanol content, extract and pH, were not affected by either treatment; however HHP and heat pasteurization affected colour, chill haze, protein sensitivity and bitterness. Change in bitterness was higher in conventional heat pasteurization, but pressures up to 300 MPa had no significant affect on bitterness. Although more studies should be carried out to investigate the effects of HHP treatment on different types of lagers and ales, our results revealed that HHP could be successfully used to process beer, even at temperatures well below those required for heat pasteurization, without affecting some of the quality attributes. Copyright © 2005 Society of Chemical Industry     

Effects of β‐Glucans and Environmental Factors on the Viscosities of Wort and Beer

This paper reports on the influence of molecular weight and concentration of barley β‐glucans on the rheological properties of wort and beer. Environmental conditions such as pH, maltose level in wort, ethanol content of beer, shearing and shearing temperature were also examined for their effects on wort and beer viscosities. In the range of 50–1000 mg/L, β‐glucans increased solution viscosity linearly with both molecular weights (MW) of 31, 137, 250, 327, and 443 kDa and concentration. The influence of MW on the intrinsic viscosity of β‐glucans followed the Mark‐Houwink relationship. Shearing wort and beer at approximately 13,000 s^?1for 35 s was found to increase the wort viscosity but reduce beer viscosity. Shearing wort at 20°C influenced β‐glucan viscosity more than shearing at 48°C and 76°C whereas the shearing temperature (0, 5 and 10°C) did not effect the viscosity of beer. At lower pHs, shearing was found to reduce the viscosity caused by β‐glucans in wort but had no effect in beer. Higher concentrations of maltose in wort and ethanol in beer also increased the viscosity of β‐glucan polymers. It was found that β‐glucans had higher intrinsic viscosities in beer than in wort (5°C), and lower critical overlap concentrations (C^*) in beer than in wort.     

Detection of Free Radicals in Beer Oxidation

Short-lived radicals produced during the incubation of beer at 60°C were detected by electron spin resonance (ESR) spectroscopic analysis using N-tert-butyl-α-phenylnitrone (PBN) as a spin trapping reagent. The hyperfine splitting (hfs) constants were 15.7 ± 0.2 G and 3.2 ± 0.2 G for α_N and a^β_H, respectively. The hfs constants of PBN adducts produced by Co⁶⁰γ irradiation were 15.6 ± 0.3 G and 3.1 ± 0.2 G for α_N and α^β_H in beer and 15.7 ± 0.3 G and 3.3 ± 0.3 G for α_N and α^β_H in double distilled water. It is proposed, therefore, that short-lived radicals produced during the incubation of beer at 60°C may be hydroxyl radicals.     

Pilot Scale Production of a Lager Beer from a Grist Containing 50% Unmalted Sorghum

Pilot scale (1000 L) brews were carried out with a grist comprising of unmalted sorghum (50% of total wet weight of grain) (South African variety) and malted barley (50% of total wet weight of grain) grist using a mashing program with rests at 50°C, 95°C and 60°C. Mashes were supplemented with a high heat stable bacterial α‐amylase, a bacterial neutral protease and a fungal α‐amylase. A control brew containing 100% malted barley was also carried out. Saccharification difficulties were encountered during mashing, and extraction of the grist was lower for the sorghum mashes. The sorghum mashes showed comparable lautering behaviour to that of the control mash. At mashing off the sorghum worts were starch positive. Apparent degree of fermentation of the sorghum gyles were less than the control gyles. Green beer filtration proved unproblematic. The sorghum beers compared quite closely with the control beer with regard to colour, pH and colloidal stability. Foam stability deficiencies were apparent with the sorghum beer. However, the fermentability of the sorghum worts were lower. Hence the sorghum beers were lower in total alcohol. Sensory analysis indicated that no significant differences existed between the sorghum beer and both the control beer and a commercial malted barley beer with regard to aroma, mouth‐feel, after‐taste and clarity. However, the sorghum beer was found to be significantly different to both of the other beers with regard to colour, initial taste and foam stability.     

Detection of aluminum residue in fresh and stored canned beer

The United States produces about 200 million barrels of beer each year from which a large percentage is packaged into aluminum cans. It is important to identify the possible effects a particular foodstuff may induce on its package especially when it is being purchased and consumed nationwide on a regular basis. Very few studies have been done on aluminum can corrosion by beer. The purpose of this study was to compare aluminum levels in fresh, and stored, canned beer representative of U.S. quality draft. A 2 × 2 × 4 design was employed for two brands of beer, A and B, held at two different temperatures of 23 °C (room temperature) and 5 °C (refrigerated) over a period of 5 months. Room temperature beer was found to contain more aluminum (108μgl⁻¹) than refrigerated beer and brand A at room temperature had significantly more aluminum content (546μgl⁻¹) than brand B (414μgl⁻¹) at the end of the duration of storage period. Aluminum content changes from day 0 to day 150 were significant. From these results, it is shown that aluminum cans are corroded over time by canned beer. However this corrosion may be reduced through refrigeration.     

A RAPID MANOMETRIC/VOLUMETRIC METHOD FOR THE DETERMINATION OF DISSOLVED CARBON DIOXIDE CONTENT OF BEER IN TANKS

A simple manometric/volumetric method has been devised for the rapid estimation of CO₂ in tank beer by unskilled operators. Tables are provided to allow calculation of CO₂ content of beer at 0°C and 15°C, and results compare satisfactorily with those obtained by determinations made using the Recommended Method of Analysis.     

Thermal Resistance of Saccharomyces cerevisiae in Pilsen Beer

The thermal resistance of S. cerevisiae (CMOJ896) was determined in Pilsen beer (pH = 4.28 ± 0.05; extract of original wort (EOW %) = 11.30 ± 0.08; percentage of alcohol by volume (% at 20°C) = 4.97 ± 0.05; total nitrogen content (mg/L) = 590 ± 37; bitterness units (BU) = 20.5 ± 1.3; carbonation of the beer (Vol. CO₂) = 2.89 ± 0.09; color (SRCM) = 3.3 ± 0.4). The flask method was used for an initial population of 1 × 10⁴ cells/mL. Decimal reduction times of D_47°C = 3.16 min, D_48°C = 2.65 min, D_49°C = 1.74 min and D_50°C = 0.68 min were obtained at the temperatures studied. Values of D_60°C = 0.01 min and z = 4.6° were obtained for this microorganism.     

Thermal Convection in Cylindro‐Conical Tanks During the Early Cooling Process

Industrially it is important to understand the cooling process of beer in cylindro‐conical tanks (CCTs) in regard to energy efficiency and to the maturation of beer from 10°C to 0°C. However the cooling process is a complicated phenomenon. We have previously studied thermal convection in a miniature CCT constructed of transparent acrylic resin (ACCT) and found that thermal convection was not uniform, but rather wavy in the circumferential direction. In this report thermal convection was studied in a CCT constructed of metal and enlarged to the 500 L size. The water temperature in the CCT was measured by thermosensors and the surfaces visualized using an infrared camera. We confirmed that both 500L CCT and ACCT have qualitatively similar flow from 10°C to below 4°C. Although there are size effects between small CCTs and large CCTs, experiments with the smaller CCT gave useful information on the early cooling process. An infrared camera was employed to investigate the state of convection and gave information on how to effectively refrigerate beer.     

Free α-amino nitrogen production in sorghum beer mashing

Free α-amino nitrogen (FAN) is an essential nutrient for yeast growth during fermentation. Under normal conditions of sorghum beer mashing, 60°C at pH 4.0, production of FAN by proteolysis accounts for approximately 30% of wort FAN, the remaining 70% being preformed in the malt and adjunct. The quality of the FAN in sorghum beer worts is good as it does not contain a high percentage of proline. Optimum conditions for FAN production during mashing are 51°C and pH 4.6. Wort FAN was increased proportionally by raising the ratio of sorghum malt to adjunct and conversely decreased by raising the ratio of adjunct to malt. FAN was also increased by the addition to the mash of a microbial proteolytic enzyme. Wort FAN is directly proportional to malt FAN.     

A preliminary study about the influence of high hydrostatic pressure processing on the physicochemical and sensorial properties of a cloudy wheat beer

High hydrostatic pressure (HHP) (400 MPa/15 min, 500 MPa/10 min, 600 MPa/5 min at 20 °C) and heat (60 °C/15 min) processing of wheat beers were evaluated by examining their impacts on microorganisms, colloidal haze, flavour, foam stability and shelf‐life prediction during 84 days of storage at 20 °C. The results obtained showed that the microbiological stability of HHP beers was comparable with heat‐treated samples, and the development of both aerobic bacteria and lactic acid bacteria was inhibited for 84 days of storage. The main parameters of the wheat beer, such as ethanol content, original extract, pH, bitterness and viscosity, were scarcely affected by either treatment compared with the control samples; however, heat pasteurization increased the colour value. Heat‐pasteurized beer resulted in an increase in the phenethyl alcohol concentration and a decrease in isoamyl acetate and ethyl acetate levels compared with the HHP samples. These treatments did not affect the amount of 4‐vinylguaiacol and 4‐vinylphenol in the beer. The HHP‐treated beers had higher colloidal haze and foam stability values than the heat‐pasteurized beers. Dynamic light scattering analysis showed that HHP treatments at 500 MPa/10 min resulted in smaller and more uniform particle sizes, which had a positive effect on beer haze stability during storage. Copyright © 2016 The Institute of Brewing & Distilling     

Characterisation of protein-polyphenol interactions in beer during forced aging

Proteins and proteinaceous material were extracted by acetone precipitation of beer that had undergone forced aging through 0 (control), 5 (medium) or 10 (high) heat/chill cycles (60°C 48h/0°C 24h). Size exclusion chromatography analysis of the crude beer extract showed that forced ageing led to a significant increase in binding of phenolic compounds to Protein Z and especially to lipid transfer protein 1 (LTP1). Protein-polyphenol conjugates were also present in high molecular weight (> 100 kDa) and low molecular weight fractions (< 5 kDa), but these conjugates were already present in the fresh beer and were not affected by the forced aging. Treatment of the crude beer extract with sulphite (2 M) dissociated the protein-polyphenol bindings in LTP1 and Protein Z that had been generated during medium forced aging. Identification and quantification of the free, the non-covalently, and the covalently bound phenolic compounds were performed by UHPLC after extraction by methanol, acetic acid, and sulphite, respectively. The amounts of vanillic acid and caffeic acid decreased in the free polyphenol fraction, indicating binding to proteins during forced aging. Epicatechin and quercetin-3-O-glucoside were found to be non-covalently bound during forced aging. Finally, gallic acid, epicatechin, protocatechuic acid, and astragalin were found to be covalently bound already in the fresh beer. © 2020 The Institute of Brewing & Distilling     

Effects of high hydrostatic pressure on shelf life of lager beer

Filtered bright lager beer samples were either treated with high hydrostatic pressure (HHP, 350 MPa for 3 and 5 min at 20 °C) or conventional heat pasteurization (60 °C for 15 min). A storage period of 56 days showed that HHP and heat pasteurization had similar results in terms of pH and color (p<0.05). However HHP-treated samples had lower bitterness and protein sensitivity and higher chill haze values than the heat pasteurized samples at the end of the storage period. The microbiological stability of HHP-treated beers was the same as that of heat-treated beers, and the development of both lactic and acetic acid bacteria was inhibited for 56 days of storage. Although more studies should be carried out to investigate the effects of HHP treatment on different types of lagers and ales, our results revealed that HHP could be successfully used to increase the shelf life of beer even at temperatures well below those required for heat pasteurization.     

Optimization of a HS-SPME-GC-MS Procedure for Beer Volatile Profiling Using Response Surface Methodology: Application to Follow Aroma Stability of Beers Under Different Storage Conditions

The optimization of the main experimental variables, such as extraction temperature, volume of sample and the extraction time of an HS-SPME/GC-MS procedure, for profiling beer volatile analysis was evaluated using response surface methodology. A central composite circumscribed design was employed to study the effect of the experimental variables on the extraction of 28 representative volatile compounds of beer flavour profile. The parameters of the models were estimated by multiple linear regressions. The strongest influence in the volatile extraction yield was the volume of the sample (V) and the extraction temperature (T), with a positive and a negative effect, respectively. The performance characteristics of the optimised method were also determined, showing adequate linear ranges, repeatability, detection and quantification limits. The optimised methodology was applied to the same beer sample stored during 5?months at three different temperature conditions (4, 20 and 40?°C). Sampling was performed monthly, and the results showed that the concentration of most volatile compounds decreased during beer storage, although the rate of decrease was clearly higher at room temperature (20?°C) compared with refrigeration conditions (4?°C). Accelerated ageing conditions (40?°C) showed the most different volatile profile. Sensory analysis also revealed large differences in the overall quality of the samples, showing that even at room temperature the aroma profile of beer is greatly modified during its shelf life.     

The Possibilities of Particle Analysis Demonstrated by the Measurement of the Colloidal Stability of Filtered Beer

Long‐term stability is one of the most important quality criteria of beer. Three groups of measuring methods are available for its determination: real time tests, predictive tests and indicative tests. One of the most common methods is the predictive forcing test, which is a time‐consuming method for accelerating beer ageing, e.g., at 0°C and 60°C. Two ways exist to perform this test: (1) follow‐up of haze development and determination of the lag phase or (2) the measurement of haze values after several days. The first option was evaluated by performing a long‐term Forcing test over a period of 4 months by analyzing a bottom‐fermented beer. It was shown that the haze curve followed a typical course with a lag phase, an increase phase and a stationary phase. Significant differences between the measurement after the cooling and the warm period were shown. In search of quicker methods and more accurate predictive indicators, the charge titration method was developed as an alternative to determine the particle charge of filtered beers, whereupon the relationship was elucidated between the increase in hazing and decrease of potential along with the advanced aging of beer. The results showed that with increased particle size due to agglomeration, the total charge decreased. In this array of trials, two differently stabilized beers were examined. Although both beers showed different haze values in the beginning (0.32 EBC and 1.30 EBC), the less stabilized beer had only 10 warm days and in contrast the beer with the good stabilization had over 20 warm days. With the help of the total charge, predictions were possible regarding the long‐term stability of the beer.     

Thermal Stability of Ricin in Orange and Apple Juices

ABSTRACT: Ricin is a potent protein toxin that could be exploited for bioterrorism. Although ricin may be detoxified using heat, inactivation conditions in foods are not well characterized. Two brands of pulp-free orange juice and 2 brands of single-strength apple juice (one clarified and the other unclarified) containing 100 μg/mL added ricin were heated at 60 to 90 °C for up to 2 h. With increasing heating times and temperatures the heat-treated juices exhibited decreasing detectability of ricin by enzyme-linked immunosorbent assay (ELISA) and cytotoxicity to cultured cells. Z-values for ricin inactivation in orange juices were 14.4 ± 0.8 °C and 17 ± 4 °C using cytotoxicity assays, compared to 13.4 ± 1.5 °C and 14 ± 2 °C determined by ELISA. Although insignificant differences were apparent for z-values measured for the 2 orange juice brands, significant differences were found in the z-values for the 2 brands of apple juice. The z-values for ricin inactivation in the clarified and unclarified apple juices were 21 ± 4 °C and 9.5 ± 1.1 °C, determined by cytotoxicity assays, and 20 ± 2 °C and 11.6 ± 0.7 °C, respectively, using ELISA. Overall, there were no significant differences between results measured with ELISA and cytotoxicity assays. Ricin stability in orange juice and buffer was evaluated at 25 °C. Half-lives of 10 ± 3 d and 4.9 ± 0.4 d, respectively, indicated that active ricin in juice could reach consumers. These results indicate that ricin in apple and orange juices can remain toxic under some processing and product storage conditions. Practical Application: Ricin is a potent toxin that is abundant in castor beans and is present in the castor bean mash by-product after cold-press extraction of castor oil. U.S. Health and Human Services recognizes that ricin could be used for bioterrorism. This study reports the stability of ricin in apple and orange fruit juices at temperatures ranging from 60 to 90 °C (140 to 194 °F).     

THE INFLUENCE OF CONDITIONING ON LAGER BEER QUALITY

The relative contributions to lager beer quality of malt, conditioning, and other parts of the brewing process have been assessed by analytical and sensory evaluation. Backed beers, brewed and fermented under various conditions, were stored at temperatures of 12°C, 4°C or 0°C for periods ranging from 2 to 38 days before filtration and bottling. No evidence could be found to justify a need for long periods of beer storage. Although prolonged storage can provide a remedial process, correcting aspects of beer quality such as diacetyl levels, final gravity, and removal of ‘young beer’ flavour, all these features can be more rapidly, effectively and economically controlled by closer attention to materials quality and primary fermentation procedure.