Acceptability,storage stability and costing of α‐amylase‐treated maize–beans–groundnuts–bambaranuts complementary blend

The effects of α‐amylase treatment on physical properties, acceptability to mothers, and cost of roasted and extruded maize–beans–groundnuts–bambaranuts complementary porridge recipes were assessed prior to their industrial production. Storage stability of the extruded α‐amylase‐treated fortified blend was assessed at 2 weeks and 6 months by sensory evaluation, peroxide value, water activity and microbiological load. The use of α‐amylase at 0.04% w/w enhanced porridge acceptability and resulted in 88% and 122% increase in flour concentration for roasted and extrusion‐cooked porridge flour, respectively, while maintaining porridge viscosity at 1000‐fold lower than that of traditionally used porridges. The extrusion cooked blend was stable for 6 months. α‐Amylase application increased the unit cost of the developed blend by only 1.4%. The total cost was less than US $ 2 kg^?1, half the minimum price of commercially available complementary foods. Further work on marketing and the efficacy of this inexpensive food on growth of infants is warranted. Copyright © 2007 Society of Chemical Industry     

Amylase production in solid state fermentation by the thermophilic fungus Thermomyces lanuginosus

The production of extracellular amylase by the thermophilic fungus Thermomyces lanuginosus was studied in solid state fermentation (SSF). Solid substrates such as wheat bran, molasses bran, rice bran, maize meal, millet cereal, wheat flakes, barley bran, crushed maize, corncobs and crushed wheat were studied for enzyme production. Growth on wheat bran gave the highest amylase activity. The maximum enzyme activity obtained was 534 U/g of wheat bran under optimum conditions of an incubation period of 120 h, an incubation temperature of 50 degrees C, an initial moisture content of 90%, a pH of 6.0, an inoculum level of 10% (v/w), a salt solution concentration of 1.5:10 (v/w) and a ratio of substrate weight to flask volume of 1:100 with soluble starch (1% w/w) and peptone (1% w/w) as supplements.     

Stabilization of α‐amylase by chemical modification with carboxymethylcellulose

Carboxymethylcellulose activated by periodate oxidation was covalently linked to porcine pancreatic α‐amylase (EC 3.2.1.1). The specific activity of the conjugate prepared was 54% of the native enzyme. The carbohydrate content was estimated to be 62% by weight as a result of the modification of 67% of the amino groups from the protein. In comparison with the native enzyme, the thermostability and pH stability were improved for α‐amylase by this modification. The conjugate was also more resistant to the action of denaturant agents such as urea and sodium dodecylsulfate. We conclude that modification of enzymes by the anionic polysaccharide carboxymethylcellulose might be a useful method for improving enzyme stability under various denaturing conditions. © 1999 Society of Chemical Industry     

中温淀粉酶改性玉米淀粉在纸板中的应用研究

目的 以酶改性玉米淀粉为施胶剂,对箱纸板和瓦楞纸板进行表面施胶,研究其对纸板物理性能的影响.方法 使用中温淀粉酶改性玉米淀粉,测试其粘度变化;然后将酶改性淀粉施胶于箱纸板和瓦楞纸板表面,测试箱纸板的挺度、环压强度、耐破度、耐折度、抗张强度以及瓦楞纸板的边压强度和耐破度,探索酶改性玉米淀粉对箱纸板和瓦楞纸板表面施胶的最佳用量.结果 使用2.5μL淀粉酶改性质量分数为10％的玉米淀粉后,将其施胶于箱纸板表面,此时箱纸板的物理性能最优.与空白样相比,箱纸板的横向挺度提高了380％,纵向挺度提高了464％,环压强度提高了53.2％,纵向抗张强度提高了10.6％,横向抗张强度提高了9.6％,箱纸板的耐破度变化不大,耐折度降低;经2μL淀粉酶改性质量分数为10％的玉米淀粉后,将其施胶于瓦楞纸板表面,其边压强度提升最多;与空白样相比,边压强度提高了45.5％.结论 酶改性玉米淀粉的制作工艺简单,为制备高性能纸板提供了参考依据.     

Proteinaceous Inhibitors of Trypsin and of Amylases in Developing and Germinating Seeds of Pigeon Pea ( Cajanus cajan(L) Millsp)

Inhibitors of trypsin and amylase in the extracts of developing seeds of 12 pigeon pea cultivars were analysed using a gel-X-ray film contact print technique and an enzyme-inhibitor assay, respectively. The inhibitors of amylase and trypsin in the extracts of germinating seeds of a pigeon pea cultivar (BDN2) were also studied. Nine trypsin inhibitor bands were detected in mature seeds of all the 12 cultivars. Inhibitory activities against amylase and trypsin were not detected in the extracts of seeds collected 11 and 27 days after flowering (DAF) by the enzyme-inhibitor assay. However, up to three trypsin inhibitor bands could be detected in the extracts of seeds collected 27 DAF by the gel-X-ray film contact technique. Two new slow-moving trypsin inhibitor bands were detected in the extracts of germinating seeds of BDN2 cultivar. These bands were prominent in extracts of seeds 10 days after germination (DAG). The amylase inhibitors and trypsin inhibitors in pigeon pea seeds are late synthesised proteins, their highest levels were observed in mature seeds and they were found to be slowly degraded during germination. Significant inhibitor activities were observed even 15 DAG. The amylases in developing seeds are insensitive to endogenous inhibitors.     

Influence of the Heating Rate on the Pasting Properties of Various Flours

Viscoamylographic tests were carried out on six commercial flour samples, three wheat flours (WF), two semolinas (S) and one rice flour (RF), using the Brabender Micro Visco‐Amylo‐Graph (MVA). The slurries were subjected to a definite temperature profile (30°C‐95°C, 95°C×30 min, 95°C‐50°C, 50°C×30 min), stirring at 250 min⁻¹ and using a 300 cm·g_f cartridge and recording the viscosity (in Brabender Units, BU) as a function of temperature and time. The aim of this work was to evaluate the influence of different heating rates (1.5, 3.0, 5.0, 7.5, 10.0°C/min) on the pasting properties of the various flours. The peak viscosity of WFs and Ss increased when high heating rates were applied, while the RF showed similar pasting properties independently of the heating rate. These behaviours were mainly ascribed to the different molecular organisation of the starch granules, responsible of different swelling and gelatinising extents, and also to a different kinetic of alpha‐amylase inactivation according to the heating rate applied. The key role of the alpha‐amylase activity in controlling the pasting viscosity of the different samples was demonstrated by the viscoamylographic test performed in the presence of silver nitrate as enzyme inhibitor.     

苎麻织物新型淀粉酶DMA-160退浆工艺研究

用正交实验探讨了酶的用量、处理温度、处理时间、溶液pH值等因素对退浆效果的影响,以毛效、失重率、白度和退浆率4个指标为评价依据,初步确定出适合苎麻织物新型淀粉酶DMA-160退浆的工艺参数,即酶用量1.0 g/L、90℃、50 min、溶液pH值5.5,浴比1∶50,JFC用量1 g/L,达到了较佳的退浆效果(退浆后织物的毛效可以达到13.0 cm/30 min,失重率达到7.6%,退浆率可达到8级,白度也有所提高),可以替代传统碱退浆工艺.     

Rheological Changes in Oatmeal Suspensions During Heat Treatment

Two amylases from fungal and bacterial source were added to oatmeal suspensions in concentrations varying from 0.0125 to 0.64%. Changes in viscosity, phase angle and elastic modulus during heating were followed together with sedimentation and flow properties. The complete pasting behavior could be followed without sedimentation problems. The hydrocolloidal properties of β-glucans appeared to be important. The bacteria/enzyme reduced peak viscosity much more rapidly than the Fungamyl enzyme at low concentrations. The flow properties of a Fungamyl treated oat meal suspension with the peak viscosity reduced > 90% were pseudoplastic.     

固态发酵生产细菌α-淀粉酶

采用国内α 淀粉酶生产常用菌株BF7658变异菌种 ,直接以麸皮为原料固态发酵法生产α 淀粉酶 ,得到较适宜的条件为 :培养基初始含水量 (质量分数 )为 60 % ,起始 pH自然 ,液体接种量为 5mL/kg ,3 7～ 3 9℃培养 4 8～ 60h ,三角瓶培养产酶水平可达 1 2 4 8U/ g ,浅盘培养平均产酶可达 1754U/ g .固态发酵生产细菌α 淀粉酶产酶水平为液体深层发酵法的 4～ 5倍 ,并且成本低廉 ,具有较好的经济和环境效益 .