3种酶制剂对生产面包的体积影响

研究真菌木聚糖酶、β-葡聚糖酶对面粉粉质及拉伸性能的影响,并考察真菌α-淀粉酶、真菌木聚糖酶和β-葡聚糖酶3种单酶对面包的作用效果。通过正交试验确立20 mg/kg真菌α-淀粉酶、50mg/kg真菌木聚糖酶和50 mg/kgβ-葡聚糖为加工面包的最优化工艺条件。在上述条件下,面包平均体积为885 mL,该体积比不使用酶制剂的平均体积提高了17%。     

SOME RELATIONSHIPS BETWEEN THE PROTEIN NITROGEN OF BARLEY AND THE PRODUCTION OF AMYLOLYTIC ENZYMES DURING MALTING

Barleys studied (Chariot and Delibes) contained different levels of extractable β-amylase enzymes. The potential levels of β-amylase enzymes of the two varieties studied were similar at 1.4 to 1.7% total nitrogen. Higher values of potential β-amylase enzyme were observed in the Delibes barley of higher total nitrogen of 1.9%. The higher level of β-amylase found in the barleys with the highest total nitrogen was not reflected in the protein banding patterns as revealed by SDS-PAGE protein fractionation. Extraction of barley proteins was largely influenced by the different extractants used. The alcohol soluble proteins, M_r 97 kDa (D-hordeins), were only extracted when mercaptoethanol was included in the extracting solution. Although barleys with the highest nitrogen (1.9%) had the highest apparent potential to develop β-amylase enzymes, the better modified low nitrogen barleys produced higher levels of β-amylase and α-amylase when malted. Dehusking revealed that the high nitrogen barleys contained more steely grains. In contrast, the low nitrogen barleys contained more mealy grains. Steely grains contained more nitrogen than mealy grains and had the greater potential to develop β-amylase. Notwithstanding, the results of this study suggested that the proteins of the lower nitrogen barleys (1.4–1.7%) were capable of producing higher levels of β-amylase and α-amylase than the higher nitrogen barleys (1.9%) over comparable periods of malting. The high apparent β-amylase potential of the barley was linked to high nitrogen levels and associated high levels of steeliness, whilst the corresponding high β-amylase levels of malt were linked to the efficiency of endosperm modification of the malted grain.     

IMPROVED EXTRACTION AND ASSAY OF β-AMYLASE BROM BARLEY AND MALT

β-Amylase was extracted from barley or malt using four physical techniques to break up grists which had been prepared using a Moulinex coffee grinder. Grinding with a Polytron homogeniser apparently completely disrupted all cells, as determined by transmission electron microscopy, and increased the efficiency of extraction of β-amylase from barley by more than 30%. The other treatments tested were without value . The β-amylase activity in extracts of barley or malt was assayed by measuring the production of reducing sugars from reduced soluble starch, using a PAHBAH reagent. α-Amylase, which interferes with the quantitation of β-amylase in extracts of malt, was not totally inactivated by the chelating buffer used for enzyme extraction or by several other chelating agents. α-Amylase activity was quantified specifically using Phadebas. Using purified α-amylase a calibration was developed which related activity, as determined using Phadebas, to reducing power units. Thus the α-amylase activity present in an extract containing β-amylase could be determined using Phadebas and the reducing power equivalent activity subtracted from the total “apparent” activity to give the actual β-amylase activity. α-Glucosidase and limit dextrinase activities are believed to be too low to have a significant effect on the apparent β-amylase . The soluble and bound β-amylase activities were measured in samples taken from micromalting barley (Alexis). Dry weight losses increased to over 10% after 8 days germination. Antibiotics, applied during steeping, were used to control microbes in one experiment. However, their use checked germination and reduced malting losses to 8.4% in 8 days germination. The soluble enzyme present in extracts from steeped barley and early stages of germination was activated (20–40%) by additions of the reducing agent DTT .     

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.     

RESPONSE OF CEREAL GRAINS TO GIBBERELLIC ACID

Aleurone cells of oats produce significantly less α-amylase than the aleurone cells of rye, wheat or barley after treatment with gibberellic acid (GA₃). Furthermore, excised embryos from oats, rye, wheat or barley are more efficient than exogenous gibberellic acid in catalysing the production of α-amylase in oats endosperms. Enzymic modification of the endosperm of oats, as distinct from the other cereal grains, is associated with rapid elongation of the scutellar apex under the aleurone cells.     

Comparative immunological and chromatographic study of some plant β-Amylases

A comparative study has been made of the β-amylases of barley, wheat, rye, oats and sweet-potato by means of exclusion chromatography and immunochemical analysis. The reactivity of barley malt and wheat β-amylase was compared with different anti-barley and anti-wheat sera. In exclusion chromatography on Sephadex G100, barley β-amylase yielded four, and both wheat and rye, two active components, whereas oat and sweet-potato had only one active component. During the storage of barley, wheat and rye β-amylases the large-molecule components were split into smaller ones; no changes occurred in oat and sweet-potato β-amylases. On analysis against a specific barley β-amylase antiserum, wheat and rye β-amylase gave a reaction which indicated that they were immunologically partly identical with barley β-amylase, and identical with each other. This serum induced no reaction in β-amylases of sweet-potato and oats. The rye β-amylase precipitation line did not display enzymic activity after reaction with this antiserum. Analyses with different antisera of barley and wheat confirmed the partial immunological identity of barley malt and wheat β-amylase. With some barley antisera, partial inhibition of wheat β-amylase activity was observed. A similar phenomenon was apparent when barley malt β-amylase was precipitated with some wheat antisera.     

PRODUCTION OF α-AMYLASES IN GERMINATING WHOLE AND INCUBATING DE-EMBRYONATED BARLEY KERNELS*

α-Amylases produced in germinated barley and incubated de-embryonated barley kernels (cv. Bonanza), in the absence and presence of gibberellic acid (GA₃), were analyzed qualitatively by polyacrylamide gel isoelectric focusing (PAG-IEF) and quantitatively by chromatofocusing. Identical patterns of α-amylase components were obtained for both germinated barley and incubated de-embryonated barley kernels at each germination/incubation stage, in the absence or presence of GA₃. Total α-amylase increased rapidly in the germinating whole seed whereas in the incubating de-embryonated grain the α-amylase activity increase was much slower. Addition of exogenous GA₃ did not induce production of higher levels of α-amylase in either the germinating whole or incubating de-embryonated barley kernel. Quantitative chromatofocusing analysis revealed that the proportion of α-amylase III to α-amylase II activity decreased linearly with germination time in the whole grain but remained constant in the incubating de-embryonated grain in the absence or presence of GA₃. The major proportion of α-amylase activity in the germinating whole grain and incubating de-embryonated grain was synthesized in the form of α-amylase II components. However, α-amylase I represented a larger proportion of the total α-amylase activity produced in the incubating de-embryonated grain, as compared to the germinating whole seed in the absence or presence of GA₃. These results suggest that embryo excision differentially affects production of α-amylase II as compared to α-amylase I.     

THE DEVELOPMENT OF β-GLUCAN SOLUBILASE DURING BARLEY GERMINATION

β-Glucan solubilase in either germinating barley or in endosperm slices treated with gibberellic acid is synthesized before endo-β-glucanase, α-amylase and protease. In common with these enzymes, β-glucan solubilase is synthesized much sooner in endosperm slices than in whole grain. Gibberellic acid stimulates β-glucan solubilase synthesis in endosperm slices and most of the activity is rapidly released into the surounding medium, irrespective of whether the hormone is present. Inhibitors of RNA and protein synthesis block the formation of β-glucan solubilase. Unlike β-glucanase, α-amylase and protease, β-glucan solubilase is present in significant quantity in untreated barley where it is concentrated in the embryo-containing half of the grain. The only β-glucan solubilase activity in barley is due to an acidic carboxypeptidase. Malt contains a small amount of a second solubilizing enzyme which appears to be an endo-β1, 3-glucanase.     

Kaffircorn malting and brewing studies. XVI. The distribution and activity of alpha- and beta- amylases in germinating kaffircorn

Unlike barley which possesses β-amylase activity before germination, sorghum grain is devoid of this enzyme. Both α- and β-amylase are produced during the germination of sorghum and, in any particular malting trial, the ratio of the enzymes to one another remains approximately constant throughout the trial. The actual value at which the ratio remains constant depends on the temperature of the malting and the variety but not on the watering treatment given during malting. The amylase concentration in the embryo is usually higher than in the endosperm but the total amount of amylase in the embryo is much less than in the endosperm. Although the embryo of sorghum is a minor contributor to the total amylase, it contributes more thsn does the embryo of barley to barley malt. The ratio of α- to β-amylase in the embryo differs from that found in the endosperm. In Short Red kaffircorn, a common malting variety, the embryo contained ii significantly lower percentage of αamylase than the endosperm. The opposite was found with the Birdproof and Sugar Drip varieties, the embryo being the richer in αamylase.     

脉冲电场对啤酒大麦萌发性质的影响

在啤酒麦芽制备过程中引入脉冲电场(PEF)技术,对浸渍后的大麦种子进行不同电场强度的处理,以了解PEF对大麦萌发性质的影响。结果表明,PEF处理有利于提高大麦萌发活力和相关理化性质。大麦籽粒经电场强度1.5、3.0、4.5、6.0、7.5 kV/cm处理后,萌发大麦的芽长、根长、根数、鲜重、干重、发芽势、发芽率、简化活力指数、还原糖含量、β-葡聚糖酶活力、α-淀粉酶活力、β-淀粉酶活力、可溶性蛋白质和氨基态氮含量等指标与对照组比较均有明显提高,发芽势、根长、β-葡聚糖酶活力、α-淀粉酶活力和β-淀粉酶活力提高的幅度分别为38.96%、43.33%、21.46%、26.48%和23.57%。对14项指标进行主成分分析的结果表明,当电场强度为6.0 kV/cm时,脉冲电场对大麦萌发的促进效果最好。     

DIFFERENCES IN MALTING PERFORMANCE BETWEEN BARLEYS GROWN IN SPAIN AND SCOTLAND

Two barley genotypes were grown, in 2 seasons, at sites in both Scotland and Spain. The development of enzyme levels and endosperm modification were assayed, over the final 3 days of malting. Spanish grown samples demonstrated faster and more extensive synthesis of both α-amylase and β-glucanase, more rapid cell wall modification and a greater reduction in milling energy during malting than Scottish grown samples. Malt milling energy was strongly associated with cell wall breakdown, which was a limiting step in modification of Scottish, but not Spanish, grown samples. Extract levels were not related to α-amylase activity, but Kolbach index exhibited an association with extract at both sites.     

Effects of Genotype and Environment on Malt β-Glucanase Activity

Fifteen genotypes of barley grown in two different locations (Gönen and Besni) were used in this study. The malting characteristics and β-glucanase activities of their malts were determined. Although, malt β-glucanase activities of the samples grown in the Besni location were much higher than those of Gönen samples, the malting quality of the samples from both locations were comparable. The results indicate that both genotype and environment affected β-glucanase activity with a more pronounced effect of the latter.     

The Development of Enzymes During Germination and Seedling Growth in Nigerian Sorghum

The levels of enzymes responsible for the enzymic modification of sorghum endosperm have been followed during germination and seedling growth. Sorghum β-glucanase was shown to be inactive towards barley β-glucan. Gibberellic acid does not appear to control the levels of α-amylase. In contrast to barley, the synthesis of this enzyme occurs in the embryo but it subsequently acts on the starch granules in the endosperm. Limit dextrinase, on the other hand appears to be present in the endosperm as a zymogen. Proteases were also examined during germination and seedling growth. Amino acid-releasing enzymes develop in the embryo and are absent from the endosperm, whereas endoproteases can be detected in the embryo and to a greater extent in the endosperm. Amylolytic attack on endosperm starch in sorghum is very extensive during the early stages of grain growth. The significance of these results to the malting properties of sorghum is discussed.     

Amylase, β-Glucanase and Protease Activities from a Mutant of Bacillus subtilis

Enzymes in the shake culture of a mutant of Bacillus subtilis developed mainly during the stationary phase of growth. Extracellular α-amylase and protease activities increased and then declined to relatively low levels after 48 h of incubation while the β-glucanase activity remained high. The production of extracellular proteolytic activity commenced only when the low molecular weight nitrogen source in the medium was completely consumed. Enzymes were fractionated by ionexchange chromatography and the molecular weights of β-glucanase, α-amylase, protease I and protease II were estimated by gel filtration to be 1.3 × 10⁴, 3.2 × 10⁴, 6.3 × 10³ and 2.0 × 10⁴, respectively. The β-glucanase and α-amylase showed maximum activities at around pH 7, but the two proteases had different pH optima (pH 6–7 and 8.5, respectively). The presence of proteolytic activity in the enzyme preparation had a significant effect on the stability of the β-glucanase and the α-amylase at 65°C.     

青稞β-葡聚糖对淀粉体外消化性的影响

对比青稞全粉和普通小麦粉体外消化性,研究青稞β-葡聚糖质量浓度和分子质量对青稞淀粉体外消化性的影响,从青稞β-葡聚糖流变学特性及其与α-淀粉酶的相互作用方面,探究青稞降血糖的可能机理。结果表明,青稞全粉中淀粉消化率明显低于小麦粉;随青稞β-葡聚糖质量浓度和分子质量的增大,其溶液黏弹性增大,对α-淀粉酶活性的抑制效果越明显,延缓淀粉体外消化效果越显著。青稞β-葡聚糖形成的高黏性环境是青稞全粉低淀粉消化率的潜在机理。     

CHANGES IN BARLEY ENDOSPERMS DURING EARLY STAGES OF GERMINATION*

Kernels of 4 barley cultivars were germinated at 18°C and samples were removed for analysis at short time intervals for the first 30 h and at longer intervals during the ensuing 90 h. α-Amylase, (1 → 3) (1 → 4)-β-glucanase and (1 → 3) β-glucanase activities were measured in each sample. Analysis of kernel sections stained with Calcofluor showed that hydrolysis of β-glucan in the crushed cell layer commenced 6–9 h after the initiation of germination. Hydrolysis proceeded from the ventral edge to the dorsal edge of the kernel. Starch granule hydrolysis followed a similar pattern in the endosperm region adjacent to the crushed cell layer, but starch hydrolysis was always preceded by β-glucan hydrolysis.     

PURIFICATION AND CHARACTERIZATION OF AN α-AMYLASE INHIBITOR FROM MAISE (ZEA MAIZE)

α-Amylase inhibitor is presented in maize seeds. It is a protein as indicated by precipitation with ammonium sulfate and trichloroacetic acid, denaturation by heat, digestion with proteases and by dye-staining. It was purified to homogeneity by ammonium sulfate precipitation and Sephadex G-75 gel filtration. It had an apparent molecular weight of 29,600 and did not contain any carbohydrate. Its properties differed from those of previously reported α-amylase inhibitors, since it was active against α-amylase of maize, produced during germination as well as against Bacillus subtilis α-amylase. It was also active against α-amylase from the insects Tribolium castaneum, Sitophilus zeamais and Rhyzopertha dominica, but it was inactive against α-amylase from human saliva, hog pancreas, Aspergillus oryzae, wheat, rye, barley, triticale, and sorghum. It was stable for 5 min at 96°C at pH 7. Maximal inhibition required at least 10 min of preincubation with the enzyme at pH 6.8 and 257deg;C. Polyacrylamide gel electrophoresis gave three protein bands, but only one was obtained in S.D.S. and mercaptoethanol.     

Effects of different carbohydrases on the physicochemical properties of rice flour,and the quality characteristics of fermented rice cake

Food Science and Biotechnology - The rice flours were hydrolyzed using α-amylase (A), α-amylase and xylanase (AX), and α-amylase, xylanase and β-amylase (AXB). The effects of...     

THE CHROMATOGRAPHIC PROPERTIES OF BARLEY AND MALT β-AMYLASES

Barley β-amlyase occurs as a heterogeneous, polydisperse enzyme in thiol-free extracts of Conquest barley. During malting, the polydisperse enzyme is altered, resulting in the formation of four distinct enzyme components which increase in activity as germination progresses. Addition of thioglycerol to a thiol-free extract of barley, or initial extraction with thioglycerol, produces extracts containing two discrete β-amylase enzymes. β-amylase I is the major component of the extract; β-amylase II occurs as a minor component. Similarly, malt extracts containing thioglycerol have two β-amylase enzymes, β-amylase III and IV. Barley β-amylase II and malt β-amylase III have similar chromatographic properties on CM-cellulose but it is not known whether these enzymes are identical. During the early stages of germination, barley β-amylase I disappears and cannot be detected in extracts of 1-day malt; β-amylase III is the major β-amylase enzyme in this extract. Malt β-amylase IV cannot be detected in barley extracts. It develops during germination until it becomes the major β-amylase in malt extracts.     

OPTIMIZED McCLEARY METHOD FOR MEASUREMENT OF TOTAL β-AMYLASE IN BARLEY AND ITS APPLICABILITY

The McCleary method for determination of β-amylase in malt has been modified in order to allow determination of total β-amylase in barley as well as malt. A ruggedness test, performed on the modified method, demonstrated that the method is quite robust and highly reproducible. When the variables α-amylase, β-amylase and diastatic power were measured in 90 malt samples, only β-amylase was significantly correlated to diastatic power (r² = 0.85 and p < 0.0001). The same high correlation was found between total β-amylase in 20 barley samples and diastatic power in the corresponding malts. The validity of this relationship was tested by predicting diastatic power in malt from total β-amylase in barley. Predicted values correlated highly to measured values (r² = 0.95). In breeding material a positive relationship was found between total β-amylase in barley and protein content. This relationship must be considered when evaluating new barley lines.