EVALUATION OF THE INFRAALYZER 400 FOR THE ANALYSIS OF BARLEY AND MALT

A collaborative study is described of the use of infra-red reflectance for the evaluation of the analytical characteristics of barley and malt. Transfer of centrally-prepared calibrations to other reflectance machines was found to be possible for moisture content and protein content in barley and malt but not for malt extract or malt modification. The examination of infra-red reflectance results, obtained at different wavelengths, by step-wise ascending regression rather than step-wise descending regression showed that the former was more satisfactory, especially in being more rapid in execution.     

Use of a scanning near-infrared reflectance spectrophotometer for assessment of the malting potential of barley

A scanning near-infrared reflectance spectrophotometer was calibrated for the estimation of barley protein, moisture, total β-glucan and predicted malt extract. About 50 samples covering the range normally encountered in selection in barley breeding were used for each calibration. The best prediction equations each using three wavelengths, gave the following root mean square differences for the samples used in the calibration; nitrogen, 0.042%; moisture, 0.22%; total β-glucan, 0.26%; predicted malt extract, 1.4%. However, prediction of samples not in the calibration set was always slightly less accurate. These four characters were predicted in about 25 s allowing rapid screening for malting quality of large numbers of barley samples. The speed and simplicity with which successful calibrations could be produced suggests that the regular updating of calibrations to include barley from new seasons or regions should be possible.     

Effect of Different Steeping Conditions on Endosperm Modification and Quality of Distilling Malt

This study showed that when barley was steeped in water for either 8 h or 16 h, hydration of endosperm materials was suboptimal and modification of endosperm materials of barley malt was inadequate. The malt produced under these steeping regimes gave poor friability scores and produced a large number of whole grains. When barley was steeped for 24 h on a continuous basis, or when a regimented standard steeping method was used, the malt produced gave higher friability scores and a much lower number of whole grains. An important relationship was found between friability scores and whole grain results for the malt samples produced under these conditions. Optic barley, whose endosperm was more difficult to hydrate, gave a strong negative correlation between friability scores and number of whole grains at R² = 0.8689. Oxbridge, whose endosperm was more easily hydrated, gave a much stronger negative correlation between friability scores and number of whole grains at R² = 0.9769. Rapid visco‐analysis (RVA) results also confirmed that steeping the barley samples for only 8 h or 16 h produced malt that modified poorly as the RVA peak viscosities were very high. RVA pasting results further confirmed that when barley was steeped for 24 h on a continuous basis, or when a standard regimented steeping method was used, good quality malt was produced and no differences were found in the RVA peak viscosities of the barley malt samples produced under the two different steeping conditions. The results of protein breakdown (proteolysis) during these experiments, measured in terms of total soluble nitrogen (TSN) production, or soluble nitrogen ratio (SNR) further confirmed that optimal proteolysis was achieved when barley was steeped for either 24 h on a continuous basis, or with a standard steep. Optimal results were also found for hot water ex‐tractable materials such as hot water extract (HWE) and free amino nitrogen (FAN) when barley was steeped for 24 h or the standard steep. The 24 h continuous steep for barley produced quality malt comparable to that obtained when the standard regimented steep was used for steeping barley. For both Optic and Oxbridge barley, with a 24 h continuous steep, produced malt that gave significantly higher fermentabilities and PSY values, regardless of germination time, than those obtained using a standard regimented steep. Therefore steeping barley for 24 h on a continuous basis prior to malting will produce good quality malt for some barley samples/varieties. This will help to reduce water usage during steeping, will save steeping time thereby reducing malting time and will reduce the amount of water for effluent treatment. All of these factors result in an overall cost saving for the malting industry.     

Composite malt with dark-purple rice malt improves the phenolic profile and antioxidant activity of malt extract

This research presents a modification of bioactive compounds of malt extract produced from Riceberry rice malt (RRM)–barley malt composite for malt-based beverage. Malt extract was produced by varying RRM at 20% w/w, 40% w/w, 60% w/w, 80% w/w, and 100% w/w and were analysed for total polyphenol content (TPC), phenolic acids constituent, and antioxidant activity. The 100% RRM extract was rich in TPC relative to 100% w/w barley malt extract. The composite malt extract containing 40% w/w–80% w/w RRM had enough TPC in the filtered malt extract (236–524 mg L⁻¹) and boiled hopped malt extract (216–485 mg L⁻¹) and were directly proportional to the antioxidant activity in the extract. Barley malt fraction in the malt extracts had a positive response on ferulic acid and sinapic acid, whereas RRM inclusion in malt extract increased p-coumaric acid, vanillic acid, rutin, and methyl coumarate concentration. Therefore, the cereal malt composite could provide strong oxidative stability to the malt extract and derived products.     

Effects of seeding rate, nitrogen rate and cultivar on barley malt quality

BACKGROUND: Crop management tools have been shown to affect barley kernel size and grain protein content, but the direct effect on malt quality is not well understood. The present study investigated the effect of seeding rate, nitrogen fertilisation and cultivar on malt quality. RESULTS: Higher seeding rates produced barley with less grain protein and smaller, more uniformly sized kernels. The small, uniformly sized kernels modified more completely, leading to malt with higher extract and lower wort β‐glucan than malt from low‐seeding‐rate barley. Increasing rates of nitrogen fertilisation caused grain protein levels to increase, which limited endosperm modification and reduced malt extract levels. AC Metcalfe showed better modification and higher malt extract than CDC Copeland, but CDC Copeland had better protein modification at higher fertilisation rates, which resulted in less reduction of malt extract as nitrogen rate increased. CONCLUSION: Higher seeding rates reduced kernel size and grain protein levels without compromising malt extract owing to better endosperm modification of the more uniformly sized kernels. Negative effects of higher nitrogen rates on malt quality can be reduced through development of cultivars with improved ability to modify protein during malting. © 2012 Her Majesty the Queen in Right of Canada     

RAPID PREDICTION OF MALT HOT WATER EXTRACT BY NEAR INFRARED REFLECTANCE SPECTROSCOPY STUDIES ON BARLEY

In recent years there has been an increasing awareness of the need for rapid screening tests for malting quality in barley. An infrared reflectance instrument has been calibrated against malt hot water extract (HWE). Results suggest that this type of instrument can be used to estimate HWE on barley and that this might provide a suitable screening method for use in a breeding programme. Greater accuracy is achieved if separate calibrations are made for winter and spring barleys and the correlation coefficients with HWE were 0.70 (n = 168) and 0.82 (n = 134) respectively.     

HOMOGENEITY OF THE FRIABLE FLOUR OF MALTING BARLEY

A detailed comparison was made of the properties of the friable flours and non-friable residues of two samples of malted barley of different nitrogen contents. The friable flours were sieved and fractionated to give a range of particle sizes, and the intact malt, whole friable flour, non-friable residues and fractionated friable flours were subjected to a range of analyses. Endosperm fractionation studies showed that the pattern of enzymic degradation of proteins in the modified friable flour of low nitrogen malt was more uniform than the corresponding pattern of protein breakdown in the friable flour of high nitrogen malt. Examination of the non friable residues showed that cell wall breakdown in the high nitrogen malt was less extensive than the low nitrogen malt. It is proposed that the high protein levels in the endosperm caused starch/protein compacting which limited endosperm hydration and enzymic modification during malting. The friability scores of high nitrogen malts may given an over estimate of endosperm modification.     

Near‐Infrared Spectroscopy for Proficient Quality Evaluation of the Malt and Maize Used for Beer Production

Moisture and total nitrogen content are considered very important factors that influence barley malt quality, as well as moisture and lipid content for maize quality. In the present study, the feasibility of using Near‐Infrared (NIR) spectroscopy to measure the moisture, total nitrogen and lipid content of the whole malt grains and maize grits was examined. The NIR spectra of the following samples were examined: 295 malt whole grains for moisture, 281 malt whole grains for total nitrogen, 128 maize grits for moisture and 102 maize grits for total lipids. Validation was carried out both by means of cross‐validation and test set validation. Coefficients of determination (R²) were higher than 93% for both malt and maize moisture and higher than 71 and 80 for malt total nitrogen and maize total lipids, respectively. The Root Mean Square Error (RMSE) values (both in Cross Validation (RMSECV) and in Prediction through external validation (RMSEP)) ranged from 0.127 to 0.165% for both malt and maize moisture, whereas they ranged from 0.043 to 0.053% for malt total nitrogen and from 0.065 to 0.079% for maize total lipids. Repeatability (r₉₅) ranged from 0.105 to 0.222% and from 0.012 to 0.155% for malt moisture and total nitrogen content, respectively, and from 0.086 to 0.192% and from 0.020 to 0.171% for maize moisture and total lipid content, respectively. The findings showed that NIR spectroscopy has potential for the rapid prediction of quality of whole malt grains and maize grits for brewing.     

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY OF BARLEY PROTEINS: RELATIVE QUANTITIES OF HORDEIN FRACTIONS CORRELATE WITH MALT EXTRACT

Several high performance liquid chromatography (HPLC) approaches have been used to study the relationships between amounts of particular groups of grain storage proteins (hordeins) and malt extract, using two sets of barley samples. The areas of several chromatogram peaks varied between samples in a manner that correlated with malt extract. Size-exclusion HPLC of protein aggregates extracted by sonication gave negative correlations of the relative areas of the three largest chromatogram peaks with malt extract in a set of 39 samples of the one variety, but not in a set of samples of 8 varieties grown at 4–5 sites. Under reducing conditions, disulphide-bonded hordeins were quantitatively extracted and the proportion of hordein in the largest peak, comprised of D- and B-hordeins, correlated well with malt extract in both sets of samples. The hordeins sequentially extracted into 50% (v/v) 1-propanol and 50% (v/v) 1-propanol-50 mM dithiothreitol (DTT) were also analysed by reversed-phase HPLC, and could be resolved into several peaks of B-, C- and D- hordeins. Relationships between the amount of certain C- hordeins in the propanol extract, and certain B- hordeins in the propanol-DTT extract and malt extract were seen. As well as providing a better understanding of the relationship between barley grain protein composition and malting quality, these HPLC methods are useful additional methods to enable partial prediction of malt extract using un-malted barley.     

RATES OF ENDOSPERM MODIFICATION DURING MICRO-MALTING OF SOME AUSTRALIAN BARLEYS

The rate and extent of endosperm modification during germination of some Australian varieties varied considerably. Barley of the variety Clipper modified rapidly in the first days of germination, but following longer germination, endosperm modification was similar to or less than other varieties. The addition of more water and the additives gibberellic acid and potassium bromate increased modification with the response depending upon the variety. A total of 23 varieties and experimental barley lines grown at two locations were micro-malted using additives. Average endosperm modification was estimated to range from 61% to 89%.     

Effect of High Temperature‐High Humidity Treatment of Germinated Unkilned Barley on Malt Quality and Extract Characteristics

The effect of a high temperature‐high humidity treatment (HT‐HHT) of germinated unkilned barley on malt quality and extract characteristics was studied. Two samples of six‐row barley were steeped to 42% moisture and germinated, with and without gibberellic acid, at 15°C for 5 days. The germinated barley was placed in a high humidity (75–80%) atmosphere maintained at 45, 55, and 65°C, respectively. For each temperature, treatments were carried out for 30, 60 and 90 min, respectively. At 45°C for 30–60 min, the malts developed high diastatic power and proteolytic activity. The high values for cold water extract and reducing sugars in the extracts indicated extensive amylolysis of starch granules during HT‐HHT of the germinated barley at 55–65°C. The worts were light in colour, with a pH of 5.3–5.8 and titratable acidity was in the range of 0.09‐0.23%. A consistent increase in soluble nitrogen and Kolbach index was observed in the malts treated at 45–55°C for 30–90 min. Free α‐amino nitrogen of the malts was in the desirable range of 120–150 mg L^?1. Therefore, HT‐HHT can be useful for improving malt modification and wort characteristics and to shorten the germination time for malts from poor quality barley.     

Image analysis and quality attributes of malting barley grain dried with infrared radiation and in a spouted bed

The impact of drying two spring barley cultivars (Mauritia and Prestige) in a spouted‐bed and in infrared radiation (IR) dryers on grain dimensions, colour, pigment content, vitality and malt quality was investigated. The results indicate that the investigated drying methods led to kernel dimension changes. Kernel shrinkage was typical of spouted bed drying, while kernel expansion was observed after IR drying at the intensity of 900 W m^?2. An increase in the intensity of yellowness (b*) on the surface of dried grain and a decrease in the yellowness intensity of kernel cross‐section were also observed. The aforementioned changes were associated with the decomposition of carotenoids (endosperm colour) and reduction of soluble proanthocyanidin and total phenolic compounds (surface colour). The drying processes also lowered germination energy and capacity, in addition to susceptibility to moisture diffusion into the endosperm. These adverse results were cultivar dependent and affected the quality of malt and wort only to a limited extent. The main changes were an increase in the Kolbach index in malt from Mauritia cv., and a fluctuation of the diastatic power of malt that did not exceed ±3%. Generally, drying of barley grain in spouted bed should be conducted at an inlet air temperature of 40 °C and using an IR drier at a radiation intensity of 600 W m^?2.     

Changes in β-glucan and other carbohydrate components of barley during malting

Changes in total (1→3), (1→4)-β-glucan content were followed during the micro-malting of nine varieties of barley with a wide range of malting qualities. These changes were related to estimates of endosperm modification based upon staining with Calcofluor. β-Glucan content declined from an average of 3.54% in the barley to 0.75% in the malt. Pentosan and total starch (including starch-derived oligosaccharides) levels showed comparatively little change during malting. β-Glucan composition of the barley was a poor indicator of malting performance. However, the β-glucan, starch and xylose contents of the malt all showed significant correlations with malt extract. Estimation of malt β-glucan content gave the best indication of malt quality. Direct determination of β-glucan may be of more value in assessing malt quality than indirect techniques based upon assessing modification of stained grains.     

CHANGES IN THE CATIONIC ISOENZYMES OF PEROXIDASE DURING THE MALTING OF BARLEY. I: TISSUE LOCATION STUDIES

Sixteen cationic isoenzymes of peroxidase were detected in barley grain (variety: Chariot) and twenty in green malt, falling to fifteen after kilning. The distribution of these among the different seed tissues was examined with a view to determining which isoenzymes were likely to survive mashing and be active during brewing. In isolated barley tissues, the aleurone layer contained one major band (Rm 0.77), and the endosperm only the four fastest running bands (Rm values 0.84–0.97). In green malt the growing embryo tip contained fifteen isoenzyme bands (Rm values 0.04–0.70), with an absence of only the faster running bands. In kiln-dried malt, isoenzymes with Rm values 0.04–0.10 increased in activity, two extra light bands appeared (Rm 0.26 and 0.61) and three other bands present in barley were lost (Rm values 0.63, 0.70 and 1.0). Much of the activity in the aleurone layer was lost. Seven of the fifteen isoenzymes in finished malt accounted for over 75% of the cationic peroxidase activity. Variation in aleurone and endosperm isoforms between different cultivars was observed, whereas the embryo showed little variation. The endosperm isoforms seem to be the ones most likely to cause oxidation problems during brewing.     

SOME BARLEY GRAIN AND GREEN MALT PROPERTIES AND THEIR INFLUENCE ON MALT HOT-WATER EXTRACT: II. PROTEIN,PROTEINASE AND MOISTURE

This paper continues the study of variation between varieties in some properties of barley and malt and examines protein-related characters and moisture uptake. Initial rate of moisture uptake was more closely related to enzyme activities than maximum moisture content. Significant varietal variation was found in all characters and this variation was greater than environmental variation with the exception of grain nitrogen concentration. In the endosperm endopeptidase activity was the character most highly correlated with malt hot water extract (HWE). The combined influence of protein- and β-glucan-related characters was investigated and the relative influence of each group of characters on HWE varied in different sections of the grain. In the endosperm the protein- and β-glucan-related characters accounted for 30% and 60% of the variation in HWE respectively.     

A SIMPLE AND RAPID TEST FOR ASSESSMENT OF ENDOSPERM PROTEIN MODIFICATION DURING MALTING*

A simple test has been developed for the quantitation of endosperm protein modification in malts. Barley meals or ground malts were extracted with a suitable solvent and the clarified hordein extract diluted into an appropriate precipitant. Of a variety of extractants and precipitants investigated, 1M urea-1% (v/v) mercaptoethanol and 1M sodium chloride were respectively found to be most suitable. Under these conditions a turbid suspension forms; the turbidity of extracts decreased progressively during malting. Turbidity was due to selective precipitation of a specific group of “B” hordeins. In an analysis of nine varieties differing in malting qualities, a significant correlation between the reduction in extract turbidity and cell wall modification (Calcofluor staining) was observed at 48 hours' malting. In addition, for each variety examined, protein modification occurred about one day before carbohydrate modification. Analysis of commercial malts and several samples of selected cultivars from regional trials found good correlations between malt turbidities and percent malt extract and Kolbach index. The test is rapid (10–90 mins) and can be used to screen large numbers of samples; since it is simpler than alpha—amino nitrogen or Kolbach index determination, it may be of use in analysis of malts for protein modification.     

AREAS OF ABSORPTION RELATING TO MALT EXTRACT VALUE IN MODIFIED NEAR INFRA-RED SPECTRA OF BARLEY FLOUR

Determinations of milling energy, nitrogen, acid-soluble beta glucan and malt extract after micromalting, were made on grain samples of twenty nine barley cultivars. In addition the flour from unmalted grains was scanned over the near infra-red spectrum, and the scan data were subjected to a principal components analysis (PC). Predicted malt extract values resulting from an NIR multiple regression equation with PC terms, correlated well (r = 0.934) with the manual extract values. This confirms previous evidence that malt extract value depends largely on constituents in the resting grain, rather than on malt enzymes. An attempt to locate NIR absorptions relating to malting quality was made by restructuring the NIR spectrum of the samples according to the weightings modified by the regression coefficients in the PC regression equation for hot water extract value. The spectrum reconstructed in this way showed a number of absorption peaks and troughs. From comparison with previous NIR scans it was concluded that a strong peak at the wavelength 2100 nm was due to a starch absorption and this together with minor starch overtone peaks correlated positively with malt extract. Troughs at 2180 nm, 1980 nm and 1700 nm indicated a negative association between malt extract and some proteins. There were also wide troughs at 1830 and 2330 nm indicating a negative relationship between malt extract and beta glucan. Other peaks and troughs in the reconstructed spectrum could not readily be assigned to a constituent. A reconstructed protein spectrum consisted of peaks and troughs that agreed with previous assignations for protein absorbancies. A milling energy reconstruction was approximately the inverse of the malt extract spectrum, and an acid-soluble beta glucan reconstruction was relatively featureless and appeared to be due to the effects of particle size variations.     

Comparison of the impact on the performance of small‐scale mashing with different proportions of unmalted barley,Ondea Pro®, malt and rice

The impact of using different combinations of unmalted barley, Ondea Pro® and barley malt in conjunction with a 35% rice adjunct on mashing performance was examined in a series of small scale mashing trials. The objective was to identify the potential optimal levels and boundaries for the mashing combinations of barley, Ondea Pro®, malt and 35% rice (BOMR) that might apply in commercial brewing. Barley and malt samples used for the trials were selected from a range of Australian commercial barley and malt samples following evaluation by small‐scale mashing. This investigation builds on previous studies in order to adapt the technology to brewing styles common in Asia, where the use of high levels of rice adjunct is common. Mashing with the rice adjunct, combined with differing proportions of barley, Ondea Pro® and malt, resulted in higher extract levels than were observed for reference mashing, using either 100% malt reference or 100% barley reference and Ondea Pro® enzymes. Synergistic mashing effects between barley, Ondea Pro® and malt were observed for mash quality and efficiency parameters, particularly wort fermentability. The optimum levels of barley in the grist (with the relative level of Ondea Pro®) were assessed to be in the range 45–55% when paired with 10–20% malt and 35% rice. When the proportion of malt was reduced below 10% of the grist, substantial reductions in wort quality were observed for wort quality parameters including extract, lautering, fermentability, free amino nitrogen and haze. Extension of this new approach to brewing with rice adjuncts will benefit from further research into barley varietal selection in order to better meet brewer's quality requirements for the finished beer. Copyright © 2016 The Institute of Brewing & Distilling     

NEW MASHING SYSTEM FOR DETERMINATION OF LABORATORY EXTRACT

The method of preparation of laboratory wort by the Tepral mashing system provides a clear improvement in the evaluation of industrial malts and in the optimization of malting procedures. The equipment required is simple and easy to operate. The use of the method has shown significant differences in terms of both wort viscosity and extract yield between malt from 2-row spring barley (variety Carina) and malt from 2-row winter barley (variety Sonja), produced under identical industrial conditions: the Sonja malt gave fewer good results for finely ground malt than did the Carina malt.     

DETERMINATION OF THE MOISTURE AND NITROGEN CONTENTS OF BARLEY AND MALT BY NEAR INFRARED SPECTROSCOPY (NIRS)

The determination of the moisture and nitrogen contents of barley and malt by near infrared spectroscopy (NIRS) has been tested by the Analysis Committee of the European Brewery Convention. In the collaborative trial four samples of barley and malt were analysed by 17 laboratories. Repeatability (r₉₅) and reproducibility (R₉₅) values of 0.3 and 1.5% m/m respectively were obtained for barley moisture over the range 12.7 to 15.8% m/m. For malt moisture these values were 0.2 and 1.3% m/m over the range 4.0 to 4.3% m/m, for barley nitrogen 0.1 and 0.3% m/m on dry matter over the range 1.57 to 2.14% m/m, and for malt nitrogen 0.1 and 0.2% m/m on dry matter over the range 1.58 to 1.82% m/m, respectively.