The effects of gums on macro and micro-structure of breads baked in different ovens

In this study, the effects of gums on macro and micro-structure of breads baked in different ovens (infrared (IR)-microwave combination and conventional) were investigated by the help of image and SEM analysis, respectively. The gums used were xanthan, guar, κ-carrageenan and xanthan-guar blend. The gums were added to the formulation at 0.5% concentration. As a control, no gum added formulations were used. Results of Image analysis demonstrated that xanthan-guar gum blend addition improved bread quality with increasing pore area fractions. It was seen that about 75% of the pores of control breads baked in infrared-microwave combination oven and about 63% of the pores of control breads baked in conventional oven had diameters of above 1000 μm. According to SEM analysis, pores in control breads baked in conventional oven were found to be smaller, and had spherical, oval-like shape as compared to the ones baked in IR-microwave combination oven. Moreover, more homogeneous closed-cell structure was observed for conventionally baked control breads. The pores of breads baked in IR-microwave combination oven were so close to each other which resulted in coalescence of the gas cells to form channels, then the pores were no longer spherical. The starch granules in conventionally baked breads were more distorted and seen as a continuous sheet of gelatinized starch. On the other hand, granular residues and continuous starch structure was observed together in IR-microwave combination heating.     

The effects of xanthan and guar gums on staling of gluten-free rice cakes baked in different ovens

The objective of this study was to determine the effects of different concentrations of xanthan and guar gums and their blends on staling of gluten-free rice cakes baked in microwave-infrared combination oven (MW–IR) and to compare the cakes with conventionally baked ones. Gums were added at concentrations of 0.3% and 1.0%. For preparation of gum blend, 0.5% xanthan gum was mixed with 0.5% guar gum. In order to understand the staling behaviour of cakes, cakes were stored at 22 ± 2 °C for 120 h. Xanthan-guar gum blend decreased hardness, weight loss, retrogradation enthalpy and the change in setback viscosity values of cakes during storage for both types of ovens as compared to control formulation. It was found that oven type was a significant factor in affecting staling parameters of gluten-free cakes.     

RVA黏度计的不同测定条件对氧化淀粉黏度性质的影响

以玉米淀粉为原料,利用次氯酸钠为氧化剂制备了不同氧化程度的氧化淀粉样品。利用RVA黏度计,通过不同的测试方法,评价了样品的黏度性质。结果表明:随着测试温度的提高,样品的保温黏度和最终黏度呈下降趋势,崩解值呈上升趋势,样品在75℃和85℃条件下的回升值显著高于在95℃条件下的回升值。随着保温时间的延长,样品的保温黏度呈下降趋势,回升值呈上升趋势。样品的糊化温度随着测试浓度的提高而降低,样品的峰值黏度、保温黏度、最终黏度、崩解值、回升值都随着测试浓度的提高而提高。随着升温速度的提高,样品的糊化温度逐渐提高,最终黏度略有下降。     

A study on the effects of different gums on dielectric properties and quality of breads baked in infrared-microwave combination oven

In this study, the effects of different gums on dielectric properties of doughs and breads baked in infrared-microwave combination oven were investigated. In addition, the quality parameters of breads formulated with different gums baked in infrared-microwave combination oven were determined. The gums used were xanthan, guar, xanthan-guar blend and κ-carrageenan. The gums were added to the formulation at 0.5% concentration. The dielectric properties and quality parameters of breads baked in infrared-microwave combination oven were found to be dependent on gum type. κ-carrageenan resulted in undesirable final bread quality, while xanthan-guar blend addition improved bread quality (high specific volume and porosity, low hardness values). The dielectric properties of bread samples formulated with κ-carrageenan were found to be the highest among the other gum types.     

不同离子胶对玉米磷酸酯双淀粉性质的影响

研究了离子胶(羧甲基纤维素钠、海藻酸钠、卡拉胶、壳聚糖)不同添加量(0∶1、1∶9、3∶7)对玉米磷酸酯双淀粉糊化特性、凝胶质构特性、溶胀度和吸油率等性质的影响。结果表明,阴离子胶(羧甲基纤维素钠、海藻酸钠、卡拉胶)降低了玉米磷酸酯双淀粉的峰值黏度、衰减值;而阳离子胶(壳聚糖)使玉米磷酸酯双淀粉的峰值黏度、衰减值显著增加。阴离子胶使玉米磷酸酯双淀粉凝胶硬度下降,而壳聚糖则使其凝胶硬度上升。阴离子胶能促进玉米磷酸酯双淀粉的溶胀,但壳聚糖抑制其溶胀。壳聚糖使玉米磷酸酯双淀粉吸油率增加。离子胶对玉米磷酸酯双淀粉性质的影响,不仅与离子胶自身性质有关,而且可能与二者之间的静电作用密切相关。     

不同聚合度甘露聚糖对甘露聚糖酶生物合成影响的研究

为了研究不同聚合度甘露聚糖对甘露聚糖酶生物合成的影响,进行了不同碳源对甘露聚糖酶生物合成的影响、魔芋甘露聚糖对菌株生长和产酶的影响、不同聚合度的甘露聚糖对甘露聚糖酶的诱导和以低聚合度的甘露聚糖为诱导物生产甘露聚糖酶的研究。结果显示：一株产甘露聚糖酶的菌种产酶存在着代谢终产物阻遏效应,合适的产酶魔芋粉浓度为12g／L,聚合度较小的甘露聚糖诱导的产酶量较大,在发酵培养基中添加低聚合度的魔芋水解物对甘露聚糖酶的生物合成有较大的促进作用,发酵34h酶活可达1831U／mL。     

Surface activity and emulsifying behaviour of some Acacia gums

The surface and emulsifying properties of six Acacia gum samples with nitrogen contents in the range 0.09–7.5% have been investigated at neutral pH. Samples which give a relatively rapid lowering of the tension at the n-hexadecane—water interface produce oil-in-water emulsions with small droplets and good stability with respect to creaming. Although the nitrogen content of these gums shows a reasonable correlation with the limiting long-time surface activity, there is no simple relationship between nitrogen content and emulsifying behaviour. It is suggested that the variability in the emulsifying properties of the gum samples from different Acacia species is dependent not only on their total protein (or polypeptide) content but also on the distribution of the protein/peptide between the low- and high-molecular-weight fractions, and on the molecular accessibility of the protein/peptide for adsorption.     

Rheological properties of commercial chestnut flour doughs with different gums

Rheology of chestnut flour (CF) doughs with arabic gum (AG), carboxymethyl cellulose (CMC), guar gum (GG) and tragacanth gum (TG) at different concentrations (up to 2.0%) were determined at 30 °C using a controlled stress rheometer. The mixing characteristics at 30 °C were achieved using Mixolab^® apparatus. Shear (0.01–10 s^?1), oscillatory (1–100 rad s^?1 at 0.1% strain), creep‐recovery (50 Pa for 60 s) and temperature sweep (30–100 °C) tests were performed. Rheological properties were significantly modified by gum added. Apparent viscosity of CF doughs, storage and loss moduli increased at content of AG (above 0.5%), CMC (at 1.0%), GG (above 1.5%) and TG (at 1.0%). Flow curves and mechanical spectra were fitted using Cross model and power models, respectively. The gelatinisation temperatures increased with gums. The same pasting trend was noticed using Mixolab^®. Creep‐recovery data, fitted by Burgers model, showed that elasticity of CF doughs improved with GG.     

不同热处理方法对芦蒿抗氧化活性的影响

对芦蒿分别进行蒸、煮和微波加热处理,用DPPH法测定它们的抗氧化活性,并与热处理前的新鲜芦蒿的抗氧化活性进行比较,发现不同热处理方法对芦蒿的抗氧化活性的影响不同。总体上看,芦蒿的抗氧化能力变化较大,新鲜芦蒿抗氧化能力较低,热处理后抗氧化能力大幅度升高。本实验专门就一系列不同浓度、不同热处理后的芦蒿进行研究,并与合成抗氧化剂BHT比较,结果表明,经微波加热处理后芦蒿的抗氧化能力很强,0.333g湿重的芦蒿经微波加热后的抗氧化能力就相当于1mgBHT纯品的抗氧化能力。      

不同鱼鳞胶原蛋白黏度特性研究

以四种鱼鳞为原料,用胃蛋白酶提取鱼鳞胶原蛋白,对胶原蛋白的分子量与不同条件影响下的黏度进行了研究。结果表明:同条件下制得的胶原蛋白分子量,鲤鱼主要分布约在94·0kDa以上,草鱼主要分布在约70·0kDa以上,鲫鱼主要分布约在65·0kDa以上,鲢鱼鱼鳞胶原蛋白分子量主要分布约在60·0kDa以上。鱼鳞胶原蛋白的黏度随着浓度的增加而增加;pH在3～4之间时,四种鱼鳞胶原蛋白黏度最大;NaCl与CaCl2对四种鱼鳞的胶原蛋白黏度的影响都呈现出相同的趋势,两者都使胶原蛋白黏度随其浓度增加而减小,但CaCl2对黏度的影响比NaCl的影响幅度变化大;四种鱼鳞胶原蛋白的黏度随丙三醇和乙醇的浓度增加而增加;鲢鱼胶原蛋白变性温度约为26℃,鲫鱼胶原蛋白变性温度约为23℃,草鱼胶原蛋白变性温度约为22℃,鲤鱼胶原蛋白变性温度约为24℃。     

Cation effects on the viscosity of gum ghatti

Gum ghatti may be readily separated into a water-soluble fraction and a gel fraction. Although the gel fraction contains a higher proportion of calcium ions this is not the cause of gel formation since electrolytes which displace calcium ions do not dissolve the gel. Single-salt forms of the gel fraction have very similar properties. Added simple electrolytes produce no specific effects related to calcium ion concentration. Different cations have different affinities for the available anionic sites in the gel and this is apparently the reason for the higher calcium concentration in the gel fraction. The gel structure is destroyed by sodium borohydride which suggests that it results from intermolecular linkages unrelated to the cation.     

Comparison of the effects of gums on dynamic rheological properties of acetylated sweet potato starch

Dynamic rheological properties of acetylated sweet potato starch (ASPS) pastes mixed with 3 commercial gums (guar gum, locust bean gum, and xanthan gum) were investigated at different gum concentrations. The dynamic moduli of the ASPS-gum mixtures were higher than those of the control, and they increased with an increase in gum concentration. In particular, the G′ value of xanthan and G″ value of guar gum at a 0.6% gum concentration were much higher as compared to those of other mixtures. Tan δ values of ASPS-xanthan mixtures were much lower than those of other samples, indicating that the elastic properties in the ASPS-gum mixture systems were strongly affected by the additions of xanthan. These results suggest that the presence of gums in ASPS modifies the viscoelastic properties, and that these modifications are dependent on the gum type and gum concentration.     

盐浓度对不同米曲霉所产中性蛋白酶活力的影响

试验对酱油酿造过程中，盐浓度对不同米曲霉所产中性蛋白酶活力的影响进行了研究。结果表明盐浓度对不同米曲霉所产中性蛋白酶活力的影响是不同的。所以在酱油酿造过程中，在一定的盐浓度下测定中性蛋白酶活力才是更客观更有效的。     

Quantitative analysis of macro and micro-structure of gluten-free rice cakes containing different types of gums baked in different ovens

The effects of different gums on macro-structure of gluten-free rice cakes baked in conventional and infrared–microwave (IR–MW) combination ovens were investigated by using the images obtained by scanner and scanning electron microscopy in this study. The gum types used were xanthan, guar, locust bean, κ-carrageenan and xanthan–guar blend. Cake containing no gum was used as control. It was observed that both addition of different types of gums affected the pore area fraction and percent number of pores of the rice cakes. The highest pore area fraction was obtained in cakes containing xanthan and xanthan–guar blend. Cakes baked in IR–MW combination oven had higher porosity than those baked in conventional oven. Micro-structure of gluten-free rice cakes was also analyzed. According to these results, conventionally baked cakes showed more starch granule deformations. Both granular starch residues and deformed starch structure were observed together in cakes baked in IR–MW combination oven. All of the starch granules did not lose their identity and did not disintegrate completely.     

The effects of different chilling methods on meat quality and calpain activity of pork muscle longissimus dorsi

The objective of this study was to investigate the effects of conventional chilling (0 to 4 °C), rapid chilling (RC, -20 °C for 30 min, followed by 0 to 4 °C), and short-duration chilling (0 to 4 °C for 30 min, followed by 25 °C) on meat quality and calpain activity of pork muscle longissimus dorsi (LD). The muscle quality characteristics pH, color, cooking loss, pressing loss and tenderness, and calpain activities were measured 0-, 3-, 12-, and 24-h postmortem. Results show that the RC resulted in a faster temperature decline of the muscle, and prevented the meat pH and Commission Internationale de l'Eclairage L* value from declining during postmortem aging. RC also reduced meat cooking loss and pressing loss compared with the other two chilling methods. However, the chilling methods did not significantly affect meat shear force. During the first 24-h postmortem, there was not a noticeable change in the activity of m-calpain. But μ-calpain activity decreased regardless of chilling method. In the rapidly chilled carcasses, μ-calpain activity remained the same 3- and 12-h postmortem. However, in the short-duration chilled and conventionally chilled carcasses, the activity was visibly reduced. At 24-h postmortem, no clear zones on the gel were observed in all three treatments. PRACTICAL APPLICATION: Conventional and RC methods are commonly used for pork in commercial practice nowadays. Compared with conventional chilling, the effect of RC on quality parameters of pork varies. In recent years, short-duration chilling (SC) is widely used in many Chinese pig slaughtering facilities. However, few researchers have studied the effect of SD on pork quality. Therefore, the present study investigated the effect of different chilling methods on functionalities or quality of chilled pork meat.     

亲水性胶体在乳制品工业中的应用

<正> 亲水性胶体是指水溶性多糖,其作用是使多糖分散体系具有黏度和形成凝胶的能力。根据原料来源,亲水性胶体可分为:生物胶(黄原胶、葡聚糖、结冷胶)、植物胶(刺槐豆胶、瓜尔豆胶)、植物渗出液(阿拉伯胶、黄耆胶)、海藻胶(卡拉胶、琼胶)、纤维素及衍生物(纤维素、羧甲基纤维素(钠))、淀粉及其衍生物、动物胶(明胶)、果胶。 在乳制品工业中被广泛应用的亲水性胶体主要有刺槐豆胶、瓜尔豆胶、果胶和卡拉胶。主要作用是保护体系中的蛋白质以耐受加工中     

The viscosity of cheese sauces with different starch systems and cheese powders

Cheese sauces were prepared by blending cheese powders, starches, skim milk powder, flavouring agents, milk and/or water to ˜24% dry matter, cooking to 98°C and simmering for ˜2 minutes. Most sauces exhibited thixotrophic behaviour as characterized by the curvilinear decreases in viscosity and shear stress with time when subjected to a constant shear rate (118s^-1). However, Colflo 67 based sauces underwent shear thinning initially and then shear thickening at shearing times >˜200 s. Increasing the total starch level from 2 to 4% resulted in sauces which had more viscous consistencies, higher susceptibility to shear thinning and higher viscosities on completion of shearing. The rheological properties of sauces were markedly influenced by serving temperature and the type of starch base used. Variation in the level of cheese solids in the cheese powder had little influence on the rheological characteristics of sauces when used at levels of <10% (w/w).     

硅胶黏度对汽车安全气囊涂层织物力学性能的影响

用不同黏度的硅胶与锦纶66织物经刮刀烘干式涂层工艺制得相应的汽车安全气囊涂层织物,对其力学性能如断裂强度、断裂伸长率、撕裂强度、耐磨性能和刚度进行了测试和分析。实验结果表明:硅胶性能和涂层界面分布对涂层织物的力学性能有着明显的影响,即随着硅胶黏度的降低,涂层织物的拉伸断裂强度、断裂伸长率、撕裂强度和耐磨性能均明显改善,而刚度维持不变。在设计安全气囊气袋时,应综合考虑材料成本和气囊模块功能来选用由合适类型的硅胶涂层的锦纶66织物。     

生物合成甘露聚糖酶中氮源作用的研究

为了研究不同氮源及氨基酸对微生物合成碱性甘露聚糖酶的影响,分别进行了不同氮源对碱性β-甘露聚糖酶合成的影响、酵母氮基作为唯一氮源对碱性β-甘露聚糖酶合成的影响、在合成培养基中添加不同的氨基酸对微生物产酶的影响、几种氨基酸作为唯一氮源对微生物产酶的影响、在粗酶液中添加氨基酸对酶活的影响和几种氨基酸复配对碱性β-甘露聚糖酶...