Control of Superoxide Dismutase Activity during Malting Using Plackett‐Burman and Box‐Behnken Experimental Design and Its Effect on Reducing Power of Wort

The Plackett‐Burman multifactorial design was employed to screen the important malting parameters for superoxide dismutase (SOD) in final malt of Ganpi‐3. The eight factors screened for SOD were steeping temperature, steeping time, peroxide hydrogen concentration in steeping water, germination temperature, germination time, withering temperature, drying temperature and kilning temperature. Variance analysis showed that steeping time, germination temperature and kilning temperature were significant for SOD activity. Box‐Behnken experimental design was further used to optimize the levels of the above three factors. By response surface methodology and canonical analysis, the optimal malting factors for higher SOD activity in final malt were: steeping time 42.2 h, germination temperature 16.9°C and kilning temperature 82.9°C. Under these conditions, the model predicted a SOD activity of 2234 U/g of dry weight malt. Verification of the optimization showed that a SOD activity of 2220 U/g was observed under optimal conditions. It showed that the experimental data could be reliably predicted by the polynomial model. Besides Ganpi‐3, three other barley varieties including Ganpi‐4, Ken‐2 and Hamelin were malted under optimal and common conditions under laboratory conditions. To some extent, SOD activities were higher in malts from the optimal malting process than those from the common malting process. Especially, SOD activities in Ganpi‐3 and Hamelin increased by 18.8% and 15.3%, respectively. Furthermore, twenty‐nine samples of malts, including eleven imported malts and eighteen domestic malts, were used. Relationships between SOD activity in malt and the reducing power of wort were examined. There was significant correlation between SOD activity and the reducing power of wort (R² = 0.8069).     

RELATIONSHIPS BETWEEN MILLING ENERGY AND HOT WATER EXTRACT VALUES OF MALTS FROM SOME MODERN BARLEYS AND THEIR PARENTAL CULTIVARS

Determinations of hot water extract values of malts of some modern barleys and their parental cultivars correlated well (r = ?0.71) with milling energy estimates made on ungerminated grain. This confirms previous findings that these grain attributes are negatively correlated over different sites and growing seasons. Three types of barley endosperm can be distinguished on the basis of milling energy determinations. Most barley cultivars that are difficult to malt or are classified as feed barleys have high milling energy values (ranging from 370 to > 400 mg trace weight). This includes a number of currently recommended cultivars with Hordeum laevitigum in their pedigree. A second endosperm type has significantly lower milling energy values than the feed barley group (ranging from 330 to 355 mg, trace weight); barleys in this category also produce malts with high hot water extract values, e.g. Wing, Proctor and Berac. All of these barleys have one of the sister lines, Kenia—Opal—Maja in their ancestry. The third endosperm type with a loosely-structured ‘mealy’ endosperm has very low milling energy values (280 to 315 mg, trace weight) and includes the cultivars Ark Royal, Triumph and Keg, which give very high hot water extracts from their malts. All of the barleys in this group have the European malting barley Kneifel (also with a very low milling energy) in their pedigree. The results strongly indicate that hot water extract values of malts of current European cultivars are mainly due to the milling energy attribute of the endosperm, or are closely linked to it. This endosperm attribute has been selected through pedigree crossing or in barley collections, from just a few older malting quality cultivars. Evidence that this attribute is not linked to Hordein protein patterns controlled by the hor 1 and hor 2 loci on chromosome 5, is also presented .     

Effect of batch‐to‐batch variation on the quality of laboratory and commercially malted Oxbridge barley

The malting performance of two different batches of Oxbridge barley was studied. The study showed that a single 24 h continuous laboratory steep was suitable for steeping the two batches of Oxbridge to provide good quality malt. Although each batch represented the same variety, and was of similar malting quality, they behaved differently in terms of friability scores, filtration rate and predicted spirit yield (PSY) by day 4 of the germination period. Worts prepared from the two malts gave different patterns of filtration rates, showing that each batch of Oxbridge modified at a different rate and in a different way, although they achieved similar final PSY results at the end of the malting period. The two batches of Oxbridge both malted rapidly, but behaved differently in terms of modification pattern, as revealed by the Rapid Visco‐Analysis peak viscosities, as well visual germination results. The results of this study confirmed that, given the same malting conditions, batch 1 germinated more rapidly than batch 2, and supports the view that Oxbridge shows some inconsistency as a malting barley variety. The study further showed that the PSY result per se is not necessarily a good indicator of optimum modification of finished malted barley. This study showed that, while a particular barley variety, such as Oxbridge, may be associated with certain qualities and can produce good quality malt when a short steeping cycle is used, other factors are likely to cause batch‐to‐batch variations from the same barley variety. While the short steeping cycle was very successful in producing high‐quality laboratory malt from Oxbridge, and results in a significant reduction of the quantity of water required for steeping, reduces malting time and also saves costs, there is evidence that there may be some additional variability associated with Oxbridge malting barley. Copyright © 2012 The Institute of Brewing & Distilling     

Effects of nitrogen application on malt modification and dimethyl sulfide precursor production in two Japanese barley cultivars

BACKGROUND: Nitrogenous components have a great influence on both malt and beer qualities. Barley storage proteins are degraded during the germination process, in which amino acids and small peptides are released. Some of these compounds relate to dimethyl sulfide precursor production in the malting process. In this study, barley and malt qualities were investigated using two Japanese barley cultivars, Sukai Golden and Mikamo Golden, with several different nitrogen (N) treatments. RESULTS: Nitrogen top‐dressing treatments efficiently increased N and sulfur (S) concentrations in grains. A difference in malt modification was induced by these treatments without any change in protease activity in malts. S‐Methyl methionine (SMM) concentration in malt of Sukai Golden with low‐N treatment was 1.8–2.1 times higher than that with higher‐N treatments. Methionine concentration in malts was not significantly affected by N treatments of both cultivars, while grain S level was not consistent under any treatments. CONCLUSION: Results show that low‐N treatment increases SMM concentration in malts despite major S‐containing amino acids of malts being not highly affected by the difference in nutrient status of grains. Further investigations are necessary into aspects of both metabolic profiles in barley germination and SMM degradation in the kilning process. Copyright © 2008 Society of Chemical Industry     

The influence of germination conditions on beta-glucan, dietary fibre and phytate during the germination of oats and barley

This study aimed to quantify the changes caused by varying germination conditions on the contents of some bioactive compounds in barley and oats. Samples of the two grains were germinated at temperatures between 10 and 20 °C for a period of 2–6 days, using a two-dimensional central composite design. The germination temperature had only minor effect in comparison with the germination time. Slight changes in the mineral content of the malts were observed, mainly caused by steeping. Phytate has been seen as an anti-nutritional compound, as it complexes minerals and lowers their bioavailability. The phytate content in barley malts was considerably lower than in the native kernels. Variations in the germination conditions did not have a significant effect on phytate content. In oats, degradation of phytate was significantly enhanced by prolonging the germination period. It was possible to retain the amounts of soluble dietary fibre, when short germination periods were applied. However, long germination periods caused an extensive breakdown of soluble dietary fibre, especially beta-glucan. The content of insoluble fibre, however, was increased by applying long germination periods for oat malts.     

Optimizing red sorghum malt quality when Bacillus subtilis is used during steeping to control mould growth

Previous work has shown that Bacillus subtilis‐S499‐based biocontrol treatments applied without aeration at the steeping stage of red sorghum malting offer good mould reduction, but yield malts with low levels of key hydrolytic enzymes. Thus we attempted to raise these levels by aerating the steeping liquor, varying the steeping time (from 8 to 40 h) and temperature (from 25 to 35 °C), and combining a biocontrol treatment with prior steeping in 0.2% NaOH. Aeration proved particularly important whenever B. subtilis cells were present in the steep liquor. The optimal temperatures for α‐ and β‐amylase were 30 and 25 °C, respectively. By increasing the steeping time, it was possible to improve the α‐amylase activity, but the β‐amylase activity peaked sharply between 16 and 20 h, depending on the steeping medium. A good compromise was steeping in a biocontrol medium for 14–16 h at 30 °C. Combination steeping treatments (0.2% NaOH for 8 h followed by biocontrol for 8 h) yielded malts of a quality approaching that afforded by dilute alkaline treatment. Copyright © 2012 The Institute of Brewing & Distilling     

MALTING TECHNOLOGY AND THE PROPERTIES OF MALT: A CLUSTER ANALYSIS STUDY

A cluster analysis study of 72 malts produced from four varieties of barley malted under varying conditions has demonstrated the relative importance of the degree of steeping, germination time and temperature and kilning on the chemical and physical analysis of the malt. Seventy-two malt samples were produced from four barley varieties malted at two different degrees of steeping, two germination temperatures, two germination times, and two kilning temperatures. The malt samples were divided into 2 or 3 groups (clusters) by means of the Fuzzy Cluster Variety family of algorithms, applied to nine chemical or physical malt analyses. Each cluster could be characterized by certain mean values for the laboratory analyses and also by a particular set of technological parameters. The degree of steeping was the most important of these parameters. Laboratory analyses such as fine/coarse difference and friability were able to discriminate between a high or low degree of steeping. The cluster with a high degree of steeping could be further divided into two subclusters, with different kilning temperature. The DMS-precursor discriminated between these two kilning temperatures.     

MALT PROCESSING STABILITY OF BARLEY CULTIVARS — A STATISTICAL ANALYSIS

This paper presents a simple statistical analysis of malting process stability of barley cultivars grown for three years in the Mississippi Valley Six-rowed Uniform Barley Nursery and in the Western United States Two-rowed Uniform Barley Nursery. The effects of variety, location, and year on barley and malt quality were investigated. First, the Duncan Multiple Range Test was used to determine whether there were any varietal, location and year differences in barley and malt properties. The effects of variety, location, and year on various characteristics were further studied by comparing differences between extremes for the two-rowed and six-rowed barleys. Second, correlations between various properties were determined by calculating simple correlation coefficients. Barley nitrogen is the single most important parameter which affects extensively the processing characteristics of barley in malting and brewing, so the partial correlation coefficients, independent of total barley nitrogen, also were calculated. Third, the effects of variety, location, year, variety × location, variety × year, and location × year, were tested with variety × location × year as the estimate of error for each of the barley and malting properties. The stability model was designed to evaluate stability of all barley and malt properties. Based on the principle of regression analysis, the stability was measured by regression coefficient and the varietal mean of each barley and malting property. Stability (over years and locations) for kernel weight was significantly higher in the new than in the old cultivars. Improvements in stabilities of total extract and fine-coarse grind extract were greater and more consistent for the six-rowed than for the two-rowed barley malts. This reflects, presumably, the generally more satisfactory total extract and fine-coarse grind extract in the two-rowed barley malts than in the six-rowed barley malts.     

EFFECTS OF THE MYCOTOXINS DIACETOXYSCIRPENOL AND DEOXYNIVALENOL ON MALTING CHARACTERISTICS OF BARLEY

In germination tests, the trichothene diacetoxyscerpanol (DAS) caused reductions in the number and total length of rootlets, and the length of the coleoptile, developing from excised barley embryos, but the effects were less than those of T-2 toxin. Rootlet and coleoptile growth was also inhibited during micromating of barley artificially contaminated with DAS before steeping, whilst α-amylase activity of finished malts were reduced by up to 49%, and α-amino nitrogen levels in worts were also lower than in controls. The effects of deoxynivalenol (DON) were less than those of DAS, e.g. the reduction in α-amylase activity caused by DON applied at the rate of 50 μg g-1 grain was less than one-half of that caused by 20 μg DAS g^?1.     

Rheological properties of gluten derived from wheat cultivars with identical HMW glutenin subunit composition†

Ten spring wheat cultivars possessing identical HMW glutenin subunits (2*, 7+8, 5+10) were evaluated for gluten and protein content. Gluten content was related to flour protein content (r=0·98). Addition of freeze-dried gluten to the base flour (cv Alpha) to a constant protein level of 12% generally increased dough strength. However, the magnitude of variation in mixing patterns depended more on the type of the supplemental gluten. Fortification of the base flour with the freeze-dried gluten from the cv Glenlea produced mixographs with the longest mixing development time (MDT), and highest band width energy (BWE) and energy to peak (ETP), suggesting that the source of gluten had a strong effect on dough rheology. The viscoelastic properties of undiluted wet gluten varied between cultivars during mixing reflecting differences in gluten quality. Freshly prepared wet gluten of Glenlea showed extended mixing tolerance as compared to Norseman or Alpha gluten. The wet gluten from cv Glenlea was less extensible with high maximum resistance to extension and had a larger area under the extensigraph curve than gluten obtained from cv Norseman. Gluten prepared from the cultivars Glenlea, Bluesky and Wildcat were less soluble in aqueous propanol and produced more froth when the dough was washed with deionised water. The froth proteins, separated by SDS-PAGE, predominantly contained strongly stained bands in the region corresponding to molecular weight <50 kDa. The rapid tests such as froth formation and alcohol solubility used in this study to discriminate various glutens were highly correlated with the mixograph parameters. These methods can be of practical value in evaluating gluten quality. © 1998 Society of Chemical Industry.     

CELLULASES OF PLANT AND MICROBIAL ORIGIN IN GERMINATING BARLEY

Cellulase activity in crude extracts of germinating barley is at least five-fold higher in hulled than in hull-less cultivars. Surface sterilization of the grain prior to germination reduces cellulase to levels that are similar in all cultivars. In hulled barley most of the cellulase detected during germination is probably of microbial origin, but there is circumstantial evidence to suggest that significant activity can also be attributed to cellulases of plant origin. The micro-organisms associated with germinating grain reside largely in the hull and the major fungal species present on the hulled variety Clipper were Aureobasidium pullulans, Rhizopus stolonifer and Penicillium spp. Surface sterilization of the grain with silver nitrate, followed by steeping in a solution containing antibiotics, completely eliminated microbial growth on hull-less cultivars. After similar treatment of a hulled barley two yeasts could be detected. The results emphasize the importance of eliminating microbial growth prior to studies of polysaccharide hydrolases which develop during the germination of barley and which are assumed to be of plant origin.     

Micromalting triticale: Optimising processing conditions

Small-scale trials were carried out to optimise the conditions for micromalting triticale grain, using three varieties grown in the UK. Compared with barley, triticale grains required short steeping periods with a short air rest. They malted rapidly, and produced malts with high hot water extracts after 4 or 5 days' germination. Applications of gibberellic acid and potassium bromate during malting significantly altered the qualities of malts. Gibberellic acid increased hot water extracts, soluble nitrogen levels and malting losses. When the additives were used in combination, high hot water extracts were obtained and malting losses were reduced relative to controls, but unexpectedly the level of total soluble nitrogen was elevated and did not significantly differ from that obtained using gibberellic acid alone. Both additives usefully reduced wort viscosities, which were unacceptably high by barley malt brewing standards. Wort separation from small-scale mashes was slow.     

MALTING CHARACTERISTICS OF FINGER MILLET,SORGHUM AND BARLEY*

The malting characteristics of the finger millet variety Imele (FI), sorghum varieties Andivo (SA) and Ingumba (SI) and the barley variety Research (BR) were compared in relation to the brewing of traditional African opaque beer as well as conventional lager beer. The investigations include (a) the effect of steeping and germination conditions, (b) the influence of gibberellic acid and kilning temperature on the activity of important brewing enzymes and (c) an appraisal of the brewing potential of the worts obtained. FI, SA and SI malts were considered unsuitable as barley malt extenders for conventional lager beers, but FI and possibly SI malts would be suitable for tropical lager beer manufacture.     

Effect of malting on antioxidant capacity and vitamin E content in different barley genotypes

Unprocessed barley is known to contain relatively high levels of antioxidants, which play a critical role in human health and the preservation of food and drink products. However, there are limited data on how the antioxidant levels in barley are affected by malting, and whether the level of antioxidants in the processed malt differs between barley varieties. This study aimed to determine the levels of individual vitamin E isomers, total vitamin E content and total antioxidant capacity before, during and after malting in 12 covered and two hulless barley genotypes. Vitamin E content and antioxidant capacity were determined by high‐performance liquid chromatography (HPLC) and ability to scavenge DPPH radicals, respectively. The vitamin E content of most genotypes was reduced after steeping, germination and kilning compared with the unprocessed samples. However, the antioxidant capacity in the malt was higher than in the unprocessed samples for the majority of the genotypes. While there was variation in the percentage change in antioxidant capacity between varieties, the antioxidant capacity of samples after malting was directly correlated with their antioxidant capacity before processing (r = 0.9, n = 14, p < 0.05). These results indicate that barley varieties that have higher antioxidant capacity at harvest retain their antioxidants after malting. Thus, these varieties are likely to be the most suitable for producing malts with the added health benefits and anti‐spoiling properties associated with greater antioxidant content. Copyright © 2015 The Institute of Brewing & Distilling     

不同蛋白质溶解度的小麦芽蛋白质组成及麦芽质量分析

为了研究小麦芽蛋白质溶解度与蛋白质组分及麦芽指标间的相关性,通过控制不同的浸麦度和发芽时间,制备了蛋白质溶解度分别为31.4％、33.1％、37.0％、37.6％、39.5％、40.9％、45.5％和54.2％的8种小麦芽,分析了小麦芽蛋白质组分、降解酶及麦芽基本指标.结果表明:随着小麦芽库值的增加,水溶性蛋白质含量成线性增加,醇溶性和碱溶性蛋白质呈现直线下降.小麦芽内肽酶活力与水溶性蛋白质含量、水分及浸出物呈现显著正相关(r分别为0.732、0.792和0.727),与醇溶性蛋白质含量呈现显著负相关(r=-0.734).因此小麦芽内肽酶活力的提高将有助于小麦芽浸出物的增加.小麦芽库值与水分、色度、浸出物、FAN、酸度均存在极显著正相关性(r=0.885、r=0.971、r=0.880、r=0.915和r=0.964);与浊度存在显著正相关(r=0.714);与有效酸度存在极显著负相关(r=-0.921).所以提高蛋白质溶解度小麦芽浸出物、浊度、FAN、酸度、色度等指标都会提高.比较8种小麦芽指标,蛋白质溶解度为39.5％时小麦芽指标较好.此时,浸出物为82.0％,FAN 166 mg/100 mg,糖化力为496 WK,黏度为1.61 cP,糖化时间为6 min.     

STUDIES ON COLD WATER EXTRACT OF MALTS: SOLUBLE PROTEIN AND MALTING BEHAVIOUR

Modification of the IoB method for Cold Water Extract (CWE) allowed the determination of the CWE and Cold-Water-Soluble (CWS-) protein in 96 micromalts per day by a single operator. The method was used to follow the changes in CWS-protein of malts of four cultivars of barley with increasing modification. Malting and non-malting cultivars were shown to have different patterns of protein solubilisation during malting. The equivalent of a Kolbach determination carried out on Cold Water Extracts of malts of more than three days modification sharply differentiated between malting and non-malting cultivars. Cold-Water-measurable proteolysis was shown not to be the cause of an unexpectedly high malting potential shown by a variety with low Diastatic Power.     

EFFECTS OF FINAL WARM WATER STEEP AND AIR REST CYCLES ON MALT PROPERTIES OF THREE IMPROVED NIGERIAN SORGHUM CULTIVARS

The effects of final warm steeping at 40°C and air-rest cycles on malting loss and other malt quality parameters of three improved Nigerian sorghum cultivars were investigated. Grains were steeped for 48 h under four different steep regimes then germinated for 4 days at 30°C. The effect of final warm steeping on kernel growth, malting loss, diastatic power, α and β-amylase and extracts of the malts was significantly affected by air-resting, cultivar and the pair-wise interactions of cultivar and steep regime. Generally, malting loss and kernel growth reduced significantly (p< 0.001) when the steep cycle was a combination of air-resting and final warm water steep at 40°C. Diastatic power, α-amylase, β-amylase and extract also improved significantly in both ICSV 400 and KSV 8 when these grains were malted by a steep regime which combined both air-rest cycles and final warm water steep. However steeping these grains under a final warm water steep without air-resting led to a decrease in extract recovery and enzyme activity. Conversely steeping SK 5912 by a combination of air-resting and final warm water steep generally, inhibited rather than enhanced extract and enzyme development.     

THE EFFECTS OF DIFFERENT STEEPING REGIMES ON WATER UPTAKE,GERMINATION RATE,MILLING ENERGY AND HOT WATER EXTRACT

Five spring cultivars and one winter barley cultivar have been assessed for aspects of malting quality following four different steeping regimes. There were significant effects of cultivar and steeping regime for all characters and cultivar X steeping regime interaction for germination rate and hot water extract. Moisture content after steep was the best guide to the optimum steeping regime. Malting quality was best predicted, in genotypes which germinated rapidly, by determining grain hardness following steeping and 24 hrs germination.     

Malting of Sorghum: Further Studies on Factors influencing α‐Amylase Activity

The effects of steep regime, nature of alkaline steeping agent, and kilning condition on α‐amylase development were studied for four Nigerian sorghum cultivars. Malt α‐amylase activity was highly significantly (p<.001) influenced by all the four factors as well as their various assortments of interaction. Generally malts from the Local Red (LR) variety produced the highest a‐amylase values, followed by those of SK 5912, Local White and KSV 8 in the above sequence. The presence/absence of air‐rest processes in steep regimes was a significant factor (p<.001) influencing malt α‐amylase response to final warm steeping as well as to the other factors under study. Similarly, the nature of the steeping agent was a very significant determinant of malt α‐amylase response to kilning condition and regime of steeping. Of significant interest was the observation that Ca (OH)₂ steeps enhanced malt α‐amylase activity at the higher temperature of kilning. The significantly lower α‐amylase values given under similar conditions by the other alkaline liquors suggest a possible increase in malt thermostability due to steeping in Ca (OH)₂. Additionally, the fact that the extent of enhancement of malt α‐amylase activity by Ca (OH)₂, at 50°C Kiln temperature, was regime‐dependent, suggests that the latter was an important modulator of sorghum germination physiology.     

AN AUTOMATED MICRO-MALTING UNIT FOR QUALITY ASSESSMENT IN A BARLEY BREEDING PROGRAMME

An automated micro-malting unit for quality evaluation of lines from a barley breeding programme, with the capacity to process 87 samples of 15 g grain or up to 129 samples of 5 g grain each weekly batch, is described. Aspects of the design of the equipment, in particular the malting chamber and sample containers, are discussed. The malting unit provided a relatively uniform environment within a batch when tested by malting replicates of one cultivar. There were very small gradients within the malting chamber during steeping and modification which resulted in small differences in the hot water extract of malts depending on container position. However, replicate samples within a batch gave mean extract values with good overall precision with a coefficient of variation of 0·6%. Furthermore, the equipment gave reproducible malting conditions from batch to batch. Hot water extract values of six barleys did not differ significantly between three successive malting batches and the major contribution to variance for all the malting characters measured in this case was attributed to differences between cultivars.