Effect of cereal,fungal and bacterial α-amylase on the rheological and breadmaking properties of medium-protein wheats

Optimal levels of cereal malt, fungal and bacterial α-amylase for baking of medium-protein flours were found to be 5 - 10. 20 and 0.35 SKB/100 g, respectively. The dough consistency decreased considerably with time, depending on the source and level of α-amylase. The paste viscosities of the flours were reduced considerably by the cereal malts even at 2.5 SKB/100 g than by the fungal and bacterial α-amylase used optimally. Satisfactory loaf volumes were obtained with optimised α-amylase supplements without extraneous sugar in the bread formula. With 0.35 SKB of bacterial α-amylase, a bread having distinguishably softer texture was obtained as compared to cereal and fungal α-amylases. Accumulated maltose in the crumb indicated the need for a strain of baker's yeast with an active maltase system to render in situ contribution of α-amylase supplements more effective.     

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).     

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     

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.     

STUDIES ON COMPARATIVE MALTING CHARACTERISTICS OF SOME TROPICAL CEREALS AND MILLETS

Malts prepared from some of the tropical cereals and millets were evaluated for their suitability in weaning food formulations. Pearl millet and finger millet malts exhibited high α-amylase activity within 2–3 days of germination, while maize, sorghum, wheat and triticale malts showed high enzyme activity after 4–5 days of germination. Malting drastically lowered the paste viscosity of cereal flours especially millet. Finger millet malt had desirable flavour and taste besides high amylase activity. Wheat and triticale malts also had acceptable flavour. Rice malt was bitter and pearl millet malt developed rancid odour and bitterness within a week after preparation.     

Fungal Hydrophobins as Predictors of the Gushing Activity of Malt

Fungal infection of barley and malt, particularly by strains of the genus Fusarium, is known to be a direct cause of beer gushing. We have shown previously that small fungal proteins, hydrophobins, isolated from strains of the genera Fusarium, Nigrospora and Trichoderma act as gushing factors in beer. A hydrophobin concentration as low as 0.003 ppm was sufficient to induce gushing. The gushing‐inducing abilities of the isolated hydrophobins varied probably due to their structural differences. The hydrophobins did not affect beer foam stability. A correlation was observed between the hydrophobin level analyzed by the hydrophobin ELISA developed and the gushing potential of malt. The risk of gushing was found to increase with hydrophobin concentrations above 250 μg/g malt. The levels of hydrophobin and the Fusarium mycotoxin deoxynivalenol (DON) in malts were not correlated which indicated that the formation of those two fungal metabolites may not be linked. Furthermore, we did not observe a correlation between the DON content and the gushing potential of the malt studied. Our observations suggest that the accuracy of predicting gushing could be improved by measuring the amount of the actual gushing factors, hydrophobins, in barley or malt.     

Optimised quantification of the antiyeast activity of different barley malts towards a lager brewing yeast strain

The brewing of beer involves two major biological systems, namely malted barley (malt) and yeast. Both malt and yeast show natural variation and assessing the impact of differing malts on yeast performance is important in the optimisation of the brewing process. Currently, the brewing industry uses well-established tests to assess malt quality, but these frequently fail to predict malt-associated problem fermentations, such as incomplete fermentations, premature yeast flocculation (PYF) and gushing of the final beer product. Antimicrobial compounds, and in particular antiyeast compounds in malt, may be one of the unknown and unmeasured malt factors leading to problem fermentations. In this study, the adaptation of antimicrobial assays for the determination of antiyeast activity in malt is described. Our adapted assay was able to detect differing antiyeast activities in nine malt samples. For this sample set, malts associated with PYF during fermentation and gushing activity in beer showed high antiyeast activity. Both PYF and gushing are malt quality issues associated with fungal infection of barley in the field which may result in elevated antimicrobial activity in the barley grain. Also, two more malts that passed the normal quality control tests were also observed to have high antiyeast activity and such malts must be considered as suspect. Based on our results, this assay is a useful measure of malt quality as it quantifies the antiyeast activity in malt which may adversely impact on brewery fermentation.     

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.     

Malting of Hulless Barley Cultivars and Glenlea (T. aestivum) Utility Wheat

Malting of hulless barley cultivar, Scout, and Utility wheat, Glenlea, was compared with the hulled barley, Harrington. Hulless barley showed faster steeping rate than either Harrington or wheat cultivars. Gibberellic acid, applied by steeping in 1 ppm solution, and germination for 2-8 days significantly increased cr-amylase activity of Scout and Glenlea cultivars and their extract yields were 46% higher than Harrington malts. The 2-day Scout malts produced highly viscous extracts. Desirable viscosity (5500 cPs) was obtained from 5-day malts.     

Impact of Dark Specialty Malts on Extract Composition and Wort Fermentation

Dark specialty malts are important ingredients for the production of several beer styles. These malts not only impart colour, flavour and antioxidative activity to wort and beer, they also affect the course of wort fermentations and the production of flavour‐active yeast metabolites. The application of considerable levels of dark malt was found to lower the attenuation, mainly as a result of lower levels of fermentable sugars and amino acids in dark wort samples. In fact, from the darkest caramel malts and from roasted malts, practically no fermentable material can be hydrolysed by pilsner malt enzymes during mashing. Compared to wort brewed with 50% pilsner malt and 50% dark caramel malt or roasted malt, wort brewed with 100% pilsner malt contained nearly twice as much fermentable sugars and amino acids. Reduced levels of yeast nutrients also lowered the fermentation rate, ranging from 1.7°P/day for the reference pilsner wort of 9 EBC to 1.1°P/day for the darkest wort (890 EBC units), brewed with 50% roasted malt. This additionally indicates that lower attenuation values for dark wort are partially due to the inhibitory effects of Maillard compounds on yeast metabolism. The application of dark caramel or roasted malts further led to elevated levels of the vicinal diketones diacetyl and 2,3‐pentanedione. Only large levels of roasted malt gave rise to two significant diacetyl peaks during fermentation. The level of ethyl acetate in beer was inversely related to colour, whereas the level of isoamyl acetate appeared to be affected by the use of roasted malt. With large levels of this malt type, negligible isoamyl acetate was generated during fermentation.     

RATE-LIMITING ENZYMES IN THE LIBERATION OF AMINO ACIDS IN MASHING

When 29 malts representing a wide variation in free amino nitrogen of wort were mashed for 3 h at 45°C, the increases in TCA-soluble amino nitrogen varied from 47 to 116 μmoles per gramme of malt. The carboxypeptidase activities of the malts showed only small positive correlations with the increase of amino nitrogen during mashing. Inactivation of the different malt carboxypeptidases by 70 to 90% with diisopropylfluorophosphate decreased the liberation of amino nitrogen by only 5 to 25%. Moreover, addition of purified malt carboxypeptidase I to the mashing suspensions had no effect on the liberation of amino nitrogen. It is therefore evident that the carboxypeptidases do not have a major rate-limiting role in the liberation of amino acids in mashing, although it has earlier been shown that they are essential enzymes in this process. The proteinase activities of the malts, determined using two methods, correlated strongly with the liberation of amino nitrogen in mashing. Addition of crude malt proteinase to the mash increased, and addition of purified barley proteinase inhibitor decreased the measured proteinase activity and the liberation of amino acids roughly to the same extent. These results indicate that the most important rate-limiting enzyme activity in the liberation of amino acids in mashing is the proteinase activity of the malt.     

Influence of malt browning degree on lipoxygenase activity

The development of off-flavour in pale beer is generally attributed to the oxidation of the intermediate products of lipid degradation catalysed by lipoxygenase during mashing. This paper deals with the effect of speciality malts, having different browning levels, on malt lipoxygenase. The results obtained showed that lipoxygenase activity, which was found to be present only in the pale malt, was affected by mashing temperatures above 63 °C and by the presence of Maillard reaction products in the speciality malts. In particular, the addition to pale malt of speciality malts, having high inhibitory capacity towards lipoxygenase but low colouring potential, was effective in reducing the off-flavour development in pale beer.     

Effects of mashing on total phenolic contents and antioxidant activities of malts and worts

Effects of mashing on total phenolic contents (TPC), radical‐scavenging activity, reducing power and metal chelating activity of malts and corresponding worts were clarified in this study. Results showed that there were significant variations in TPC and antioxidant activity across malts and worts. An 8.8% of increase in TPC was observed during the early stage of mashing, accompanied by an increase in antioxidant activity. However, 2.6% of decrease in TPC and inconsistent changes in antioxidant activity were found during the mashing at higher temperature. Overall, mashing resulted in 6.0% and >10.0% of increases in TPC and antioxidant activity, respectively. Moreover, Pearson correlation analysis revealed that there were good correlations (ranging from 0.622 to 0.735, P < 0.01) between TPC and antioxidant activity of malts and worts. Additionally, mashing resulted in more positive correlations between TPC and antioxidant activity, emphasising the key role of malt phenolic compounds for wort antioxidant activity.     

EFFECT OF CALCIUM IONS IN SORGHUM BEER MASHING

One of the problems in sorghum beer brewing is that of sugar production. This is because sorghum malts are low in diastatic activity, the grist contains a high proportion of adjunct and in some brewing processes conversion is carried out at pH 4. Since the positive effects of calcium ions on alpha-amylase activity are well described, the use of additional calcium in sorghum mashing was investigated. Mashing at pH 4.5 in the presence of 0.1% calcium acetate (227 ppm Ca) resulted in almost complete conservation of diastatic activity during conversion and higher reducing sugar production compared with tap water (31 ppm Ca). At a mash pH of 4, a calcium ion concentration of approximately 200 ppm gave maximum reducing sugar production and wort yield and increased extract. Under these conditions, some alpha-amylase activity was detected at the end of the conversion, whereas without calcium no alpha-amylase activity was detected. It, therefore, appears that improved conversion took place due to the conservation of alpha-amylase activity by calcium ions. The inclusion of additional calcium ions in sorghum beer mashes also enabled the same amount of sugar production compared with straight tap water but using a substantially lower proportion of malt in the grist.     

Lipase Activities During Malting and Fermentation of Sorghum for Burukutu Production

Local red and white, and SK₅₉₁₂ varieties of sorghum grains were malted, and assayed for amylase, diastatic and lipase activities. The 5‐day malts from the red and white varieties were fermented for 48 h to produce burukutu, during which, lipase activities were monitored. Malt values peaked on day 5, and the red malts had the highest diastatic activities while the white variety had the lowest. Lipase activity in the malts peaked on day 4 with the red having the highest activity. The pH of the fermenting gruels decreased from 5.33 and 5.35 and levelled off at 3.88 and 3.85 for the red and white malts respectively. During fermentation, lipase activity peaks were detected at 0 h, 21 h and 45 h for the red malt with the highest peak at 45 h. The peak fermentation times for lipase activity in the white malt was at 0 h, 21 h and 48 h with the highest peak at 48 h. Lipase activity within the first 39 h was higher in the white gruel. Sorghum malt lipase from the red and white varieties may consist of three isoforms, two of which may have activity optima in the acidic pH range.     

α-GLUCOSIDASE ACTIVITY OF SORGHUM AND BARLEY MALTS

Sorghum malt α-glucosidase activity was highest at pH 3.75 while that of barley malt was highest at pH 4.6. At pH 5.4 employed in mashing sorghum malt α-glucosidase was more active than the corresponding enzyme of barley malt. α-Glucosidase was partly extracted in water but was readily extracted when L-cysteine was included in the extraction buffer, pH 8. Sorghum malt made at 30°C had higher α-glucosidase activities than the corresponding malts made at 20°C and 25°C. Nevertheless, the sorghum malts made at 20°C and 25°C produced worts which contained more glucose than worts of malt made at 30°C. Although barley malts contained more α-glucosidase activity than sorghum malts, the worts of barley had the lowest levels of glucose. The limitation to maltose production in sorghum worts, produced at 65°C, is due to inadequate gelatinization of starch and not to limitation to β-amylase and α-amylase activities. Gelatinization of the starch granules of sorghum malt in the decantation mashing procedure resulted in the production of sorghum worts which contained high levels of maltose, especially when sorghum malt was produced at 30°C. Although the β-amylase and α-amylase levels of barley malt was significantly higher than those of sorghum malted optimally at 30°C, sorghum worts contained higher levels of glucose and equivalent levels of maltose to those of barley malt. It would appear that the individual activities of α-glucosidase, α-amylase and β-amylase of sorghum malts or barley malts do not correlate with the sugar profile of the corresponding worts. In consequence, specifications for enzymes such as α-amylase and β-amylase in malt is best set at a range of values rather than as single values.     

Effect of cold shock on the enhancement of β‐amylase activity during malting and malt processability for a red sorghum intended for brewing use

The low β‐amylase activity of sorghum malt is a major concern when malts are intended for use in brewing. Several studies have shown that the germination temperature plays an important role in β‐amylase synthesis. In this study, the cold shock treatment was envisioned as a means of improving β‐amylase synthesis during red sorghum malting. The results show that, when a high‐frequency decrease in the germination temperature is used, the obtained malt exhibits a significantly increased β‐amylase activity. This study shows that this increase is not sufficient to consider cold shock as a means of improving β‐amylase activity for red sorghum brewing use, as the processabilty of the malts is unsatisfactory. Copyright © 2015 The Institute of Brewing & Distilling     

The Impact of Malt Derived Proteins on Beer Foam Quality. Part II: The Influence of Malt Foam-positive Proteins and Non-starch Polysaccharides on Beer Foam Quality

Pilot (50 litre) and small scale (700 mL) brewing trials conducted using, similar brewing protocols with 25 different malts, indicated that differences in malt quality influenced foam stability (Rudin head retention value) by up to 24%. In addition to conventional measures of malt quality, enzyme-linked immunosorbent assays (ELISA) were used to measure the level of the putative foam-positive proteins, BSZ4 (protein Z4), BSZ7 (protein Z7), BSZ7b and lipid transfer protein 1 (LTP1). Regression analysis performed on the combined pilot and small scale data sets identified that malt BSZ4, wort β-glucan and wort viscosity, and beer protein, β-glucan and arabinoxylan were positively correlated with foam stability, while malt Kolbach index (KI), and beer FAN were negatively correlated with foam stability. Potentially foam-positive proteins such as BSZ7 and LTP1 were not correlated with foam stability. The negative correlation of BSZ4 level with KI suggested an additional role for BSZ4 in influencing protein modification. Step-wise multiple regression indicated that up to 82% of the variation in foam stability could be predicted from the malt and beer characteristics measured, demonstrating that there are a number of inter related malt derived factors that influence beer foam stability.     

An early development of the nonenal potential in the malting process

The scarce knowledge of the significance of enzymatic oxidation of polyunsaturated fatty acids throughout the malting process led the authors to conduct studies on the monitoring of a set of selected parameters involved in the reaction. Lipoxygenase (LOX) activity, the nonenal potential, the temperature and the moisture content were assessed for the top and bottom malt layers in various stages of an industrial kilning process. Significant differences were obtained between the lower and upper malt bed, suggesting that the moisture content and temperature gradient play a key role on the production of E-2-nonenal during the early stages of kilning. The residual nonenal potential already present in the finished malt (malt-RNP) may account for approximately 25% of the total nonenal potential in the mash, depending on the residual LOX activity. LOX showed a good degree of relationship with the nonenal potential for micro-malts (r=0.79, p<0.05), whereas for commercial malts no correlation was found. These results suggest that the malt-RNP plays a prominent role for commercial malts, probably owing to the great heterogeneity observed for the malt bed in the industrial kiln. On the other hand, a major role of LOX during mashing was observed for micro-malts, emphasizing that the intrinsic properties of the barley and malt may be overwhelmed by technological factors. Therefore, kilning programmes should be adopted in order to minimize formation of malt-RNP during the drying phase of the malting process.     

Studies on baking of high alpha-amylase flours: effect of pH,salt and L-cysteine . HCI in the dough

The effect of varying concentrations of sodium chloride (0 to 2.5%), pH (5.8 to 4.2) and KBrO₃ (75 ppm) with and without addition of L-cysteine ± HCI (25 to 75 ppm) on the baking of flours with high content of alphaamylase (108 to 540 SKB/100 g) was compared with a normal flour. Decreasing the pH of dough to 4.2 and increasing the salt concentration to 2.5% reduced the loaf volume and gluten recoveries considerably. Decreased pH also reduced the mixing tolerance of dough, which was counteracted by increased salt content of normal and high alpha-amylase flours. A combination of low pH, salt and L-cysteine ± HCI and 75 ppm of KBrO₃ without sugar in the dough of higher alpha-amylase flour produced a satisfactory loaf by eliminating bulk fermentation.