降解黄原胶与降解瓜胶凝胶体系的流变性研究

降解黄原胶与降解瓜胶在一定条件下共混,形成凝胶体系.通过对其流变特性进行研究,表明该体系具有显著的黏弹性和剪切变稀性.考察了总胶浓度、蔗糖、共混比例及降解食品多糖的分子量等因素对共混凝胶体系流变特性的影响.研究了该凝胶体系的本构方程,结果表明,修正Williamous-Oldroyld-4参数模型可确切描述凝胶体系的黏度曲线,计算值与实验值吻合良好.     

黄原胶与魔芋胶的协效凝胶性研究

黄原胶与魔芋胶均为非凝胶多糖,但二者在一定条件下共混可以得到凝胶。当黄原胶与魔芋胶以0.7/0.3的配比共混,多糖总浓度为1%时,二者的协效凝胶性最强,即凝胶强度最大,同时对制备温度和体系盐离子浓度对多糖共混凝胶性的影响作了初步研究,研究表明,当制备温度80℃,盐离子浓度为0.2mol/L,凝胶强度最大。     

黄原胶降解酶酶学性质的初步研究

利用黄原胶降解菌(Paenibacillus lautus)XD2-8制备黄原胶降解酶,并对其酶学特性做了初步的研究。结果显示,该酶的最优酶促反应条件为:温度35℃、pH6.0、底物浓度5g/L;葡萄糖对该酶促反应具有抑制作用,且葡萄糖浓度越大抑制作用越强。     

黄原胶与魔芋胶混胶黏度的影响因素研究

黄原胶和魔芋胶都是非凝胶多糖，二者在一定条件下共混可以出现强烈的协同效应。本文研究当黄原胶和魔芋胶以5／5的配比共混，总浓度为1％，温度，柠檬酸，蔗糖和功能型甜味对混胶多糖黏度的影响。结果表明：升高温度使混胶的黏度降低；当柠檬酸的使用量大于0．2％时，混胶的黏度下降；40℃时甜味剂的加入使得混胶的黏度升高。     

猪屎豆胶与黄原胶复配胶的流变性研究

本实验主要通过测定体系黏度研究了猪屎豆胶与黄原胶复配胶的流变学性质。实验结果表明,猪屎豆种子胶与黄原胶有较强烈的协效性,二者的最佳复配比为6：4;复配胶的黏度随浓度的升高而升高,浓度达到0．4％时开始形成凝胶,浓度达到0．8％时形成坚实的凝胶,浓度为0．7％时的溶液黏度为5367mPa·s;混合胶液为“非牛顿流体”,溶液具有“假塑性”;胶液的最佳加热温度为80℃,最佳加热时间为1h;pH5～9、冻融变化、苯甲酸钠、超声波和微波处理对对其黏度影响较小;复配胶具有良好的耐盐稳定性。     

魔芋胶-黄原胶复配体系流变学特性及其凝胶形成动力学分析

为探究魔芋胶与黄原胶2 种食品胶复配使用后的协同作用,以魔芋胶和黄原胶为原料,控制总凝胶质量分 数为1%,以魔芋胶与黄原胶质量比分别为2∶8、4∶6、5∶5、6∶4、8∶2进行复配后,考察复配体系的流变学特性并对 其凝胶形成进行动力学分析。结果表明：魔芋胶-黄原胶复配体系具有假塑性,当魔芋胶的添加比例逐渐增大时, 复配体系黏度系数K增大,流体系数n减小,且复配体系的动态黏弹性质也随着魔芋胶与黄原胶的质量比不同而改 变,当魔芋胶与黄原胶质量比为6∶4时,复配体系的K值达到最大、n值最小,具有最强的假塑性及黏弹性。同时, 魔芋胶与黄原胶的不同质量比对凝胶形成速率有较大影响,当质量比小于6∶4时,凝胶形成显示出较慢的速率,且 形成的凝胶强度较弱;当质量比为6∶4时凝胶形成速率加快,SDRa曲线和G’曲线上升明显,形成的凝胶强度增大, 当质量比继续增加时,凝胶形成速率反而降低。采用阿伦尼乌斯方程对凝胶形成过程中的动力学参数进行拟合,决 定系数均在0.98以上,表现出较高的拟合精度;凝胶形成过程中的活化能在魔芋胶与黄原胶质量比为6∶4时有显著 增加（P＜0.05）,高温段与低温段间的活化能也表现出明显差异。     

黄原胶与瓜尔豆胶混胶黏度的影响因素及微结构研究

黄原胶与瓜尔豆胶以不同配比共混后具有良好的协同增效作用.当黄原胶与瓜尔豆胶的混配比例为5:5时,其协同增效作用最大.混胶体系的黏度随着制备温度的升高而增大,当制备温度80℃时,体系黏度达到最大值.混胶体系的黏度在酸性条件下不稳定,而在碱性范围内其黏度保持相对稳定.柠檬酸加入量在0.1～0.3 g/100mL之间时,对混胶体系的黏度基本无影响;甜味剂的使用影响混胶体系的黏度.偏光显微结构表明,纯黄原胶溶液和黄原胶/瓜尔豆胶混合物都有双折射现象,在瓜尔豆胶存在的情况下,但混胶形成的液晶中间相在相同浓度下比纯黄原胶溶液具有更多的非均相.     

响应面法优化Paenibacillus sp.JX426产黄原胶降解酶发酵培养基

从土壤中分离筛选出1株具有较强黄原胶降解能力的类芽孢杆菌(Paenibacillus sp.)JX426.为了获得高活力的黄原胶降解酶,研究借助Minimb15软件,采用Plackett-Burman试验设计方法、最陡爬坡试验设计方法和响应面分析方法对菌株JX426进行了液体发酵条件的优化.首先通过Plackett-Burman方法对7个相关影响因素的效应进行了评价,并筛选出有显著正效应的黄原胶、CaCl2添加量和有显著负效应的酵母粉添加量等3个因素,然后利用最陡爬坡试验设计方法和响应面分析方法确定了上述3个因素的最佳工艺参数,即黄原胶、CaCl2和酵母粉的添加量分别为0.39%、0.02%和0.042%.试验结果表明,在最佳浓度和组成条件下,黄原胶降解酶的酶活能达到4.20U/mL,较优化前的3.05U/mL提高了37.7%,为黄原胶降解菌的实际应用奠定了基础.     

结冷胶与黄原胶复配体系流变与凝胶特性

对质量分数1%的不同比例的结冷胶和黄原胶复配体系的流变和凝胶特性进行了研究,初步探讨了其相互作用机理。结果表明:随着黄原胶比例的提高,复配体系的粘弹性增加,储能模量G'和损耗模量G″增加。黄原胶的添加还提高了复配体系的凝胶弹性、内聚性和持水力。初步判断在复配体系中,2种聚合物相互混合,形成单独的凝胶彼此渗透,形成了一个互相结合的网络结构。     

黄原胶降解酶发酵条件的优化及其降解产物活性的研究

本试验对Mictobacterium sp XT11菌产生的降解黄原胶的降解酶进行发酵条件的优化,并研究在发酵过程中生成的具有生物活性的黄原胶寡糖。实验结果表明：该菌种最适宜的发酵条件是,黄原胶为最适碳源,浓度为O．3％,酵母浸粉为最适氮源,浓度为0．3％,温度为28℃,培养基初始pH值7．0,转速为150r／min等。同时证实,降解的寡糖确实具有一定的生物活性。     

不同分子量降解壳聚糖和降解卡拉胶复合凝胶体系及其流变性质

以降解壳聚糖与降解卡拉胶为主要原料,将不同分子量级别的降解多糖在一定条件下共混制得不同凝胶体系,通过选取3个代表性的体系考察分子量对凝胶体系流变特性的影响。在特定条件下,降解壳聚糖和降解卡拉胶复配可形成凝胶。通过流变测试可见,G'、G'随着分子量的不同有差异,通过考察凝胶触变环可得到复合凝胶体系受力后恢复能力也随分子量的不同有差异,可见分子量对复合凝胶性能有显著影响;通过幂律模型表征该凝胶体系剪切速率随黏度变化趋势,表明该复合凝胶体系为假塑性流体。     

氧化降解淀粉-乙烯基类单体接枝共聚反应的研究

以十二烷基硫酸钠、Span80为乳化剂 ,过硫酸铵 /亚硫酸氢钠氧化 -还原体系为引发剂 ,用乙烯基类单体与氧化降解淀粉接枝共聚 ,制备可用于皮革复鞣的改性淀粉产品。采用逐步寻优法研究了单体配比、乳化剂用量、引发剂用量 ,对接枝率、接枝效率和单体转化率的影响 ,得到较佳的合成条件为单体配比 :丙烯酸 (AA)1 0 g、丙烯腈 (AN) 5 g、甲基丙烯酸甲酯 (MMA) 1 5 g、丙烯酸丁酯 (BA) 1 0 g;乳化剂用量 :十二烷基硫酸钠 0 .75g,Span80为 5 g;引发剂用量 2 .5 g。对接枝共聚产物进行FT -IR、XRD和SEM表征。     

The effects of ruminally degraded protein on rumen fermentation and ammonia losses from manure in dairy cows

This experiment investigated the effect of dietary crude protein (CP) and ruminally degraded protein (RDP) levels on rumen fermentation, digestibility, ammonia emission from manure, and performance of lactating dairy cows. The experiment was a replicated 3 × 3 Latin square design with 6 cows. Three diets varying in CP concentration were tested (CP, % of dry matter): 15.4 (high CP, control), 13.4 (medium CP), and 12.9% (low CP). These diets provided metabolizable protein balances of 323, −44, and 40 g/d and RDP balances of 162, −326, and −636 g/d (high, medium, and low, respectively). Both the medium and low CP diets decreased ruminal pH compared with high CP, most likely because of the higher nonfiber carbohydrate concentration in the former diets. Ruminal ammonia pool size (rumen ammonia N was labeled with ¹⁵N) and the concentration of total free amino acids were greater for the high CP diet than for the RDP-deficient diets. Apparent total-tract nutrient digestibilities were not affected by treatment. Both the medium and low CP diets resulted in lower absolute and relative excretion of urinary N compared with the high CP diet, as a proportion of N intake. Excretion of fecal N and milk yield and composition were not affected by diet. Milk N efficiency (milk N ÷ N intake) and the cumulative secretion of ammonia-¹⁵N in milk protein were greater for the RDP-deficient diets, and milk urea N concentration was greater for the high CP diet. Both medium and low CP diets decreased the irreversible loss of ruminal ammonia N compared with the high CP diet. The rate and cumulative ammonia emissions from manure were lower for the medium and low CP diets compared with the high CP diet. Overall, this study demonstrated that dairy diets with reduced CP and RDP concentrations will produce manure with lower ammonia-emitting potential without affecting cow performance, if metabolizable protein requirements are met.     

Clarifying the confusion between poligeenan,degraded carrageenan,and carrageenan: A review of the chemistry,nomenclature, and in vivo toxicology by the oral route

Abstract

Carrageenan (CGN) is a common food additive that has been widely used for decades as a gelling, thickening and stabilizing agent. Carrageenan has been proven safe for human consumption; however, there has been significant confusion in the literature between CGN and the products of intentional acid-hydrolysis of CGN, which are degraded CGN (d-CGN) and poligeenan (PGN). In part, this confusion was due to the nomenclature used in early studies on CGN, where poligeenan was referred to as “degraded carrageenan” (d-CGN) and “degraded carrageenan” was simply referred to as carrageenan. Although this nomenclature has been corrected, confusion still exists resulting in misinterpretation of data and the subsequent dissemination of incorrect information regarding the safe dietary use of CGN. The lack of understanding of the molecular weight distribution of CGN has further exacerbated the issue. The significant differences in chemistry, manufacture, and protein reactivity of CGN versus d-CGN and PGN are reviewed, in addition to the in vivo toxicological profiles of CGN, d-CGN, and PGN. As CGN cannot be hydrolyzed to PGN in vivo, concerns over the use of CGN as a food additive are unfounded, particularly since current studies support the lack of oncogenic and tumorigenic activity of CGN in humans.     

单宁酸交联处理对明胶性质的影响

采用单宁酸作交联剂对明胶进行交联改性处理,对其凝胶性、降解性进行分析,制备VB1 微胶囊并确定芯材的释放性能。结果表明,与原料明胶相比,交联明胶形成凝胶的最低浓度基本未发生改变,仍为0.6 % 左右,但是在相同浓度下交联明胶的凝胶强度明显降低。体外降解实验表明,原料明胶和交联明胶在模拟胃液中几乎不发生降解,但在模拟肠液中都发生降解,且交联明胶的降解速度更慢。交联明胶为壁材制备的微胶囊,其芯材在模拟胃液和模拟肠液中有一定的缓释效果。     

Rheological behavior of functional sugar-free guava preserves: Effect of the addition of salts

The addition of salts to carrageenan and locust bean gum gels functions to improve the characteristics of texture, thereby increasing gel strength. This effect is widely studied in gels of model systems but is studied to a lesser extent in complex systems, such as fruit preserves. The objective of this study was to evaluate the effect of adding salts on the rheological behavior of functional sugar-free guava preserves, as well as to correlate the rheological parameters. To this end, three types of texture properties were analyzed (texture profile, stress relaxation and uniaxial compression) in functional sugar-free guava preserves prepared with different concentrations of KCl and CaCl₂ salt. The analyses were performed with a texturometer (Stable Micro Systems, Model TA - XT2i), and the parameters were analyzed using a Scott-Knott test at 5% probability, principal components analysis and Pearson correlation. CaCl₂ was more effective for improving the characteristics of texture, especially gel strength (concentration near the F3: 0.33%), whereas KCl addition degraded gel strength. In the analysis of test relaxation, the Maxwell model parameters provided better discrimination between samples than the Peleg model parameters. Positive and negative correlations were observed, and the parameters of hardness, adhesiveness and elastic modulus ideal (E₁) were the most correlated with other rheological parameters.     

丙三醇醇解聚酯产物的测试与表征

 本文采用醇解法,研究了废弃聚酯纤维(PET)在丙三醇中的醇解机理,并利用红外光谱(FT-IR)、紫外光谱(UV)、质谱(MS)、高效液相色谱(HPLC)、热重(TGA)五种表征方法对醇解产物进行分析。首先通过红外光谱和紫外光谱初步判定降解产物结构;其次应用质谱分析得到降解产物的分子结构和相对分子质量;再次由高效液相色谱对降解产物进行定量分析,并结合热重分析判断产物纯度,最后应用盐酸-丙酮法测定降解产物的环氧值。综合五种表征,得到了丙三醇醇解PET聚酯的机理,并测定降解产物的环氧值为0.259。     

Aflatoxin can be degraded by the mycelium of aspergillus parasiticus.

Aflatoxins B1, B2, G1, and G2 were degraded by the 8- and 16-day old but not by the 4-day old mycelium of a toxigenic strain of Aspergillus parasiticus. The 16-day old mycelium degraded the toxin more rapidly than did the 8-day old mycelium. Degradation of toxin by the mycelium was similar at pH 2.5 and 6.0.     

Dynamic viscoelastic study on the gelation of basil seed gum

Oscillatory measurements were used to investigate the effect of temperature and concentration on the viscoelastic and gelling properties of basil seed gum (BSG). Linear viscoelastic region was determined by strain sweep and it was found in 0.5% strain. Storage modulus (G′) was greater than loss modulus (G″) in all concentrations and they increased by improving BSG concentration. Yield stress value was determined by stress sweep and it increased from 1.40 to 7.47 Pa when BSG concentration increased from 1% to 3%. Frequency sweep showed BSG solution was a typical weak gel, and complex viscosity (η*) had linear correlation with frequency. The effect of temperature on gel forming was investigated during heating (20–90 °C) and cooling (90–20 °C) phases. BSG was characterised as a thermo‐reversible gel and did not have thermal hysteresis. Gelling temperature was raised as BSG concentration was increased. Exhibiting special rheological properties of BSG makes it as a proper synergistic gel, which can be applied in real food systems such as dairy desserts.