Influence of amylases and xylanase on chemical, sensory, amylograph properties and microstructure of chapati

Effect of enzymes on the quality of chapati - the flat unleavened bread made from different wheat varieties was studied. Doughs treated with fungal α-amylase, bacterial α-amylase, xylanase and combination of bacterial α-amylase and xylanase were examined for chapati making quality. The shear force of chapatis treated with bacterial α-amylase, xylanase, fungal α-amylase and combination of bacterial α-amylase and xylanase were in the range of 2.5-2.8 N, 2.3-2.5 N, 3.5-3.7 N and 2.2-2.5 N, respectively, and they were found to be lower and significantly different than that of their corresponding controls (4.7-6.5 N). Soluble starch and soluble amylose content of the chapatis prepared from dough treated with amylases were significantly different than that of control. Chapatis prepared from dough treated with bacterial α-amylase had shown higher amount of soluble amylose (around 0.5 g/100 g) compared to other treatments (0.2-0.25 g/100 g). In chapatis prepared from dough treated with bacterial α-amylase, and combination of bacterial α-amylase and xylanase, the amylograph paste viscosities were 38-66 BU, and were very much lower and significantly different from that of control (232-390 BU) may be due to the residual enzyme activities. The microstructures of chapatis prepared from dough treated with enzymes were uniform with distorted starch granules surrounded with protein matrix, while in control, the starch granules were spherical with protein matrix overlapping on one another to form aggregation. Chapatis prepared from dough treated with enzymes had softer texture, better pliability and higher overall quality scores compared to control.     

Purification and Characterization of a Thermostable alpha-Amylase from Bacillus licheniformis

The heat stability of a bacterial α-amylase is important for industrial starch utilization. Although extensive studies have been done on heat stable α-amylase from various bacterial species little is known about the α-amylases of Bacillus licheniformis. In order to get better understanding of thermostable amylases produced by different strains of B. licheniformis and provide information how to utilize the enzyme in starch processing, studies on purification and characterization of a commercial heat stable bacterial α-amylase from B. licheniformis BLM 1777 are reported.     

Susceptibility of Various Starch Granules to Amylases as Seen by Scanning Electron Microscope

Starch granules were observed by a scanning electron microscope in order to provide information concerning the types and extent of damage of the surface and internal structure of starch granules attacked by amylases. Granules resistant to the action of amylases, namely, potato, yamanoimo, and high-amylose maize starches showed shapes and surfaces similar to the intact granules after the action of either Rhizopus glucoamylase or crystalline bacterial α-amylase. Granules susceptible to amylases, namely, normal, waxy, soft starch, and soft starch opaque-2 maize starches showed numerous pin holes on the surface layer and pores penetrated into the inner layers of the granules during the attack with amylases. In the case of α-amylolysis, it is apparent that once the enzyme has penetrated into the inner layers of a granule, the layers are more readily attacked than the peripheral layers.     

甘薯浓缩汁加工过程中液化和糖化的工艺研究

立足国内丰富的甘薯资源,解决了甘薯浓缩汁中因淀粉引起的沉淀问题,同时把甘薯淀粉转化为葡萄糖。以新型耐高温α-淀粉酶为液化酶和高转化率糖化酶,研究了影响甘薯淀粉液化、糖化的因素,同时优化了甘薯淀粉液化、糖化的工艺参数。     

Changes of Carbohydrate Compositions During Enzymatic Hydrolysis of Starches of Various Origin

Hydrolysis of starch of various origin, liquefied with bacterial α-amylase to DE 13.5 and then saccharified only with glucoamylase and simultaneously with pullulanase to DE 97–98, was investigated. It was found that the hydrolysis of wheat starch was delayed in relation to the hydrolysis of potato and maize starch, particularly in the first period of saccharification. The delay decreased with time but at the end of the saccharification it was still 24 h. The carbohydrate composition of wheat starch hydrolyzates differed from the hydrolyzates of potato- and maize starch in a smaller content of glucose and lower oligosaccharides (G₁-G₄) and a greater content of higher oligosaccharides and dextrins (G₅-G_n). This, among other things, could have an influence on higher viscosity of solutions of wheat starch hydrolyzates in relation to respective hydrolyzates of potato and maize starch.     

淀粉酶分解马铃薯淀粉的因素研究

研究α-淀粉酶与β-淀粉酶对马铃薯淀粉的分解效果。在控制一定温度和时间的条件下,采用正交设计、因素分析、优化处理、均衡试验。实验结果表明,α-淀粉酶添加量0.15%(4000U),淀粉量20%,处理温度80.0℃,时间13min,液化效果达到最佳;β-淀粉酶量0.15%(50000U)、温度60℃、时间46h、pH5.4,糖化效果最佳。     

Changes of Carbohydrates and Molecular Structure of Dextrins During Enzymatic Hydrolysis of Starch with Maltogenase Participation

Investigations of the potato starch hydrolysis during bacterial α-amylase “BAN 240 L” liquefaction to 19.5 DE and then saccharification with exo-acting α-amylase “Maltogenase 1000 L” alone and together with pullulanase “Promozyme 200 L”, were carried out. Under adequate conditions at different enzyme dosages hydrolyzates of the maltose, content of 60 to about 80% in DS at significantly lower glucose and minimal maltotriose content were obtained. Investigations comprised both carbohydrate contents in hydrolyzates, changing with hydrolyse course and dextrin molecular structure in hydrolyzates. It was found that decreasing dextrin molecular weight and the number of branchings in dextrin molecules was accompanied by characteristic changes of the viscosity of hydrolyzate solutions.     

Raw Starch Digestion by α-Amylase and Glucoamylase from Chalara paradoxa

Glucoamylase and α-amylase of Chalara paradoxa were separated by hydrophobic column chromatography using butyl-Toyopearl 650M. The α-amylase showed the highest activity at pH 5.5 and 45°C, and was stable in the pH range of 5.5–6.5 and at temperatures lower than 40°C. The glucoamylase showed the highest activity at pH 5.0 and 45°C, and was stable in the pH range of 4.0–7.5 and at temperatures lower than 45°C. The molecular mass of the α-amylase and glucoamylase estimated by SDS polyacrylamide gel electrophoresis was 80,000 and 68,000, respectively. Both glucoamylase and α-amylase could digest more effectively raw rice starch and raw corn starch than raw sago starch and raw potato starch. 2% raw rice starch in 10 ml solution was digested by more than 90% by 100 units of each amylase. When these amylases were used combined, raw corn starch was more effectively digested than they were used singly. This cooperative action in raw corn starch digestion was also observed when. C. paradoxa α-amylase and R. niveus glucoamylase were combined.     

The Effects of Enzyme Hydrolysis on the Properties of Potato,Cassava and Amaranth Starches

X-ray diffraction method and differential scanning calorimetry were used to study the effects of enzyme hydrolysis on physico-chemical properties of potato, cassava and amaranth starches. Various hydrolysis procedures and different sources of enzymes were employed. The highest percentage of hydrolysis was obtained using the bacterial thermostable α-amylase following by the saccharification with amyloglucosidase. Enzyme treatment showed decrease in the degree of crystallinity of all hydrolyzed starch samples of A-type crystals. B-and C-types were weakened upon enzymatic hydrolysis at 60°C and completely dissappeared at 100°C. The gelatinization endotherm decreased for samples with low degree of crystallization and disappeared in samples with amorphous stage.     

Low Temperature Sweetening in Susceptible and Resistant Potatoes: Starch Structure and Composition

Starch isolated from ND 860–2 potatoes, which were resistant to chillsweetening, had higher amylose and lower amylopectin as well as a higher crystallinity as compared to starch isolated from Norchip potatoes, which were susceptible to low temperature sweetening. ND 860–2 starch exhibited greater resistance to α-amylase attack and amorphous swelling as well as higher gelatinization temperatures and onset swelling temperatures than starch isolated from Norchip. Examination of starch granule structure using bright field light microscopy indicated crystalline concentric rings in ND 860–2 not seen in Norchip. Scanning electron microscopy of granules incubated with a-amylase indicated more intact ND 860–2 starch granules compared to Norchip. These data strongly suggest that starch granule composition is a factor differentiating the low-temperature sweetening sensitive cultivar from the resistant potato seedling.     

Kinetic Studies During Enzyme Hydrolysis of Potato and Cassava Starches

The hydrolysis of raw potato and cassava starches by bacterial α-amylase depends on the time of action, temperature and on the specific starch involved. The molecular weight of the trade α-amylase (Termamyl 60L), determined by SDS-PAGE, was found to be 55–65 kDa. The properties of α-amylase such as kinetic parameters, inhibition, stability, and thermostability were studied. The constants K_m and maximum reaction rate V_max for α-amylase were fitted to Michaelis-Menten models with these two starches. Differences in response of potato and cassava starches to hydrolysis by Termamyl 60L can explain differences found in K_m and V_max values and inhibition properties.     

Influence of enzyme treatment on the rheology of rye doughs

The rheological behaviour of rye dough is mainly influenced by enzymatic reactions. An investigation with a rotation rheometer called a rheological baking test was used to study the influence of pentosanase, proteinase, fungal α-amylase, and bacterial α-amylase, respectively. The application of pentosanase increased the plasticity of the dough and decreased the viscosity. Proteinase had only a slight influence on the rheological behaviour of rye dough. It slightly decreased the dough viscosity, but had no influence on the visco-elasticity. The fungal and the bacterial α-amylase showed the same effects. The dough elasticity decreased with the increase in temperature. These effects are obvious even at temperatures below gelatinization, and the bacterial amylase shows a greater influence, because it can work at higher temperatures. It could be concluded that the dough structure is mainly built up by pentosans and proteins at temperatures of 30°C, whereas the starch plays a major role in the temperature range above 45°C. A bread baking test showed that pentosanase had an effect on the shape of the loaf whereas the amylases influenced the volume and the crumb elasticity. Proteinase showed no influence on baking results. This correponds well with the results of the rheological investigations. The rheological baking test is a good tool for predicting the baking performance of rye flour.     

Substituent distribution within cross-linked and hydroxypropylated sweet potato starch and potato starch

Revealing the substituents distribution within starch can help to understand the changes of starch properties after modification. The distribution of substituents over cross-linked and hydroxypropylated sweet potato starch was investigated and compared with modified potato starch. The starches were cross-linked with sodium trimetaphosphate and/or hydroxypropylated with propylene oxide. The native and modified starches were gelatinized and hydrolysed by pullulanase, β-amylase, α-amylase and a combination of pullulanase, α-amylase and amyloglucosidase. The hydrolysates were analysed by HPSEC, HPAEC and MALDI-TOF mass spectrometry. Cross-linking had only a slight effect on the enzymatic hydrolysis, where hydroxypropylation evidently limited the enzymatic hydrolysis. The results obtained suggest that the hydroxypropyl substituents are not distributed regularly over the starch chains. Although the average substitution was around 2 hydroxypropyl groups per 10 glucose units, in the enzyme digests of hydroxypropylated starches, oligomer fragments of 10–15 glucose units, carrying 5–8 hydroxypropyl groups, were identified. It is hypothesised that higher levels of substituents are present in the amorphous regions and periphery of clusters of starch granules. This is the first time that the location of hydroxypropyl groups within sweet potato starch has been examined in this detail. Despite significant differences in granule architecture between starches from potato and sweet potato, similar patterns of hydroxypropylation have been found.     

不同品种甘薯的干燥特性及对全粉品质的影响

以9个甘薯品种为原料,研究不同品种甘薯在相同工艺条件下的干燥特性,分析甘薯品种与其全粉品质及得率的相关性。结果表明:鲜薯成分中影响熟化甘薯热风干燥速率的因素主要是可溶性糖含量,而影响颗粒全粉得率及品质的因素主要是水分、淀粉、可溶性糖、粗蛋白含量及多酚氧化酶、β-淀粉酶活性。鲜薯的水分含量及可溶性糖含量越低,淀粉含量越高,加工成颗粒全粉的产品得率越高。     

Some Properties and Degradability of Isolated Starch Granules

Starch granules of 11 starchy feedstuffs were isolated. An isolation procedure is presented. The procedure did not damage the starch granules, as could be proven by scanning electron microscopy. The starch granules were nearly completely defatted by the procedure and only about 0.5% of the original protein remained in the starch, except for rice starch. The content of apparent and real amylose was measured in the isolated starch granules. Degradability of raw materials and isolated starch granules was determined with α-amylase and rumen fluid. Starch of tapioca and rice was relatively easy to degrade by α-amylase and rumen fluid, while potato starch was relatively difficult to degrade by α-amylase. Starches containing a low amount of amylose were found to degrade faster than starches containing a high amount of amylose.     

一株源自深海沉积物产中温α-淀粉酶菌株的鉴定及其酶学性质的研究

通过使用寡营养人工海水培养基,从深海沉积物中筛选能够降解淀粉的菌株。通过划线培养获得单菌落,并利用革兰氏染色、扫描电镜和gyrB基因测序进行菌株的初步鉴定和系统发育分析。通过采用3,5-二硝基水杨酸法测定该菌株所产生的α-淀粉酶酶活力,并探讨不同淀粉含量、菌株生长温度及生长周期对该α-淀粉酶产量的影响。结果表明:分离获得一株革兰氏阳性菌,能够有效地降解淀粉,形状为杆状,初步确定为解淀粉芽孢杆菌TVG11-1。菌株TVG11-1最适的生长温度和pH分别为45 ℃和pH7.0,其所产生的α-淀粉酶是一种不依赖淀粉底物的胞外中温淀粉酶,其最适反应温度为60 ℃,最适反应pH为6.5。本研究将为淀粉糖化以及其它涉及淀粉降解的食品加工过程提供菌种资源。     

Enhancing the hydrolysis of corn starch using optimal amylases in a high-adjunct-ratio malt mashing process

Incompletely degraded corn starch particles often seriously inhibit wort filtration and decrease a brewery’s beer productivity. Herein, the inhibiting factors of starch hydrolysis and the application of amylases to degrade residual starch were evaluated. The results showed that resistant starch and the amylopectin of corn starch were not the inhibiting factors. Almost all residual starch left in the spent grain layer was proved to be degradable by amylases. Mesophilic α-amylase was selected through a comparison of nine amylases, which increased the wort filtration rate by 44%. However, >6% of corn starch was still left after mashing when a high ratio of corn starch to water (>1:3.5) was used in liquefaction. The low water content in liquefaction was proved to be the key inhibiting factor. Considering the existing equipment and brewing technology, the application of mesophilic α-amylases should be a simple and effective method for enhancing the hydrolysis of corn starch and accelerating the wort lautering process during a high-adjunct-ratio beer brewing process.     

Labeling of Starch Granules by Bombardment with Tritium Atoms

Starch granules were labeled by exposure to tritium atoms produced by thermal dissociation of tritium gas at a tungsten filament. Activity was shown by α-amylase etching experiments to be confined to the surface of the granule. Dextrins and low molecular weight compounds could be partially resolved on Sephadex G-75. The dextrin produced during tritiation had an elution volume corresponding to dextrin of 20–35 glucose units and was hydrolyzeable by α-amylase. Labeled starch was hydrolyzed first with ß-amylase and the limit dextrin hydrolyzed further with α-amylase. A comparison of the specific activities of the maltoses produced by the two enzymes demonstrated that labeling was more heavily concentrated in outer brunches than in inner branches. Amylose obtained from labeled potato starch was purified by crystallization and on DEAE-Sephadex columns. The ion-exchange purified potato amylose was hydrolyzed with ß-amylase with 50% of the activity retained in maltose. Tritium was found to be concentrated at the nonreducing ends of the amylose molecules. These results suggest that starch molecules are organized in granules with nonreducing ends oriented to the surface.     

Carbohydrate Compositions and Molecular Structure of Dextrins in Enzymatic High Conversion Starch Syrups

35% DS potato starch slurry liquefied with bacterial α-amylase to 13,6 DE was saccharified with a combination of fungal α-amylase and glucoamylase at different enzyme dosages ratios. Saccharification was carried out 44 h at 55°C and pH 5.0. DE-value, carbohydrate compositions, molecular structure of dextrins and viscosity at 35°C were investigated in starch hydrolyzate samples taken after 4, 8, 20, 32 and 44 h. In dependence on the ratio of enzyme dosages of fungal α-amylase to glucoamylase and on hydrolysis (DE) progress, changes in carbohydrate composition, decrease of molecular weight and number of dextrin branchings were observed and in dependence on them viscosity of hydrolyzate solutions decreased.     

Prediction of Degradability of Starch by Gelatinization Enthalpy as Measured by Differential Scanning Calorimetry

It was investigated whether the degradability of starch could be predicted by differential scanning calorimetry (DSC). Degradation of potato starch with a varying degree of gelatinization. of isolated starch of different origins, and of raw materials differing in origin and technological treatment was determined with α-amylase and bovine ruminal fluid. Gelatinization enthalpy and the gelatinization temperature of starch were determined by DSC. There was a good correlation between gelatinization enthalpy measured by DSC and degradation with α-amylase and ruminal fluid for potato starches with varying degrees of gelatinization and for isolated starch granules of different origins. For raw materials of different origins there was a good correlation between gelatinization enthalpy and degradation with α-amylase, whereas the correlation between gelatinization enthalpy and degradation with ruminal fluid was poor. There was a good correlation between gelatinization enthalpy and degradation with both α-amylase and ruminal fluid for (technologically treated) raw materials of one and the same origin. There was no relation between starch degradation and gelatinization temperature.