Chemical characterization of tomato pomace

Tomato‐processing by‐product, also known as tomato pomace, consists of peel and seeds and represents around 4% of the fruit weight. If these wastes remain unused, they not only add to the disposal problem but also aggravate environmental pollution. The aim of this paper is to evaluate the chemical composition of tomato pomace collected at different steps during industrial processing in order to assess the quality of this by‐product. Twenty‐one tomato pomace samples were considered for analysis. Samples corresponded to different steps during tomato processing for paste: seven after pulper, five after finisher, six before turbopress and three after turbopress. Samples were analyzed for moisture content, total and soluble sugars, protein, fat, soluble and total fiber, as well as mineral content. From the results obtained we can conclude that tomato pomace composition (in dry weight basis) is as follows: 59.03% fiber, 25.73% total sugars, 19.27% protein, 7.55% pectins, 5.85% total fat and 3.92% minerals. Copyright © 2006 Society of Chemical Industry     

Rheological characterization of okra pectins

Polysaccharides from okra pods (Abelmoschus esculentus) were extracted using a sequential extraction protocol and compared with a simple extraction at pH 6. Rheological properties of three okra extracts were then investigated by means of molecular weight determination, dilute solution rheology, steady shear and oscillatory rheological measurements. The extraction protocols resulted in extracts of relatively high purity and multimodal molecular weight distribution. Furthermore, molecular parameters of the isolated biopolymers such as intrinsic viscosity, Huggins constant, critical concentration and coil overlap parameter were calculated from dilute solution viscometry. Investigation of the generalized flow behaviour using a modified Cross equation and Cox–Merz plots showed evidence that as concentration increases specific interactions start taking place among the polymeric chains that modify the rheological behaviour of the extracts. The change in the rheological behaviour could not only be explained by differences in the molecular weight of the samples but also should be attributed to the fine structure of the chains that are obtained under the different extraction protocols. Present investigation shows that further optimization of such protocols may result in polysaccharide fractions with specific rheological properties.     

Ultrasonic characterization of lactose dissolution

The ultrasonic properties (at 2.25 MHz) of lactose solutions and suspension of lactose crystals (d ∼ 50 μm) were measured as a function of concentration (0–40 wt.%). Ultrasonic velocity increased linearly with concentration regardless of the state of dissolution of the lactose crystals while ultrasonic attenuation was low and concentration-independent when the lactose was dissolved and increased approximately linearly with the concentration of suspended crystals. Therefore the amount of lactose present and the state of dissolution can be determined simultaneously with single ultrasonic sensor. A sensor based on this principle was applied to a stirred tank and used to measure the time taken to mix powdered lactose into a solution and the time for the added lactose to dissolve.     

Immobilization and characterization of ficin

Fig tree latex (ficin) was immobilized on Celite by adsorption. The free and immobilized ficin were utilized in the production of teleme (a Turkish milk product). After immobilization, the optimal temperature of ficin was shifted from 60 to 80 degrees C. Both free and immobilized ficin exhibited higher milk clotting activity in the acidic pH range. Increase in solid content of milk affected milk clotting activity in opposite direction. When the amount of either free or immobilized enzymes doubled, clotting timereduced nearly 1.6 and 1.7 fold for free and immobilized enzyme, respectively. Use of immobilized enzyme in teleme production gave better results in terms of chemical and sensory properties compared with teleme made by free enzyme. Syneresis in teleme reduced from 70% to 60% depending on immobilization. Both acidity and bitter taste of teleme produced from free ficin was due to extensive protein hydrolysis by proteolytic fractions.     

Sensory characterization of human milk

Fore and hind milks from a single morning feed collected from 24 nursing mothers over 3 consecutive d were evaluated for sweetness, viscosity, and mouthcoat by a trained adult panel using magnitude estimation. Milks were perceived as sweet, thin, and low in mouthcoat. Hind milks were slightly more viscous and mouthcoating than fore milks. The higher fat content in hind milk was associated with higher estimation of physical viscosity. Milk fat content decreased as maternal age increased. Significant differences occurred between milks in lactose, fat, and protein contents. By use of a sweetness power function curve, the sweetness intensity of human milk was estimated as equivalent to a 2.12% sucrose solution.     

酪蛋白酶解特性的研究

用胰蛋白酶酶解酪蛋白,用正交实验得出的最佳酶解条件进行酶解。取不同酶解时间的酶解物,分析酶解物的水解度、氨基氮含量、可溶性氮含量、肽氮含量及pH值随时间的变化趋势,水解度和氨基氮含量在12h内出现显著性增长,可溶性氮含量和肽氮含量在1h内出现及其显著的增加,pH值在10h内表现出明显的下降趋势。从不同角度分析和推测酪蛋白酶解过程。     

载银介孔SBA-15抗菌剂的制备及表征

为解决有机抗菌剂耐热性差、易分解和使用寿命短的问题,选用介孔无机材料SBA-15作为载体,以γ-氨丙基三乙氧基硅烷(APTES)为修饰剂,采用嫁接的方法对介孔SBA-15进行改性,使其表面接枝氨基官能团,采用常规AgNO3溶液浸渍法,制得抗菌性能优良、杀菌效果持久的广谱抗菌剂.通过x射线衍射(XRD)、红外光谱(FT-...     

仿紧空间的一个刻画

称拓扑空间X的开覆盖U有迭次σ-相对局部有限相对闭加细,如果U有一个加细PP(n,k)满足:(1) n,k∈N+,P(n,k)相对子空间X-∪P*(i)∪∪P*(n,j),∪∞=∪∞n=1k=1i相似文献   

羊毛粗纱改性研究及表征

为了去除羊毛鳞片,以消除羊毛织物对人体的刺痒感,采用高锰酸钾-蛋白酶法对羊毛粗纱进行改性处理,适当浓度的高锰酸钾与羊毛的鳞片层发生氧化反应,使鳞片得到适度降解,再加上蛋白酶的协同作用,加快了鳞片层的蛋白质肽键的水解,从而达到良好的剥鳞效果,降低了纤维的定向摩擦效应及纤维的细度,同时也减少了染色壁障,使低温染色成为可能。选用L9(34)正交试验方法,对改性前后的羊毛纤维进行了表观形态、力学性能、红外性能和热重测试等客观表征分析,确定了最佳改性工艺。结果表明:高锰酸钾-碱性蛋白酶法羊毛改性工艺是一种有效的减量剥鳞的加工新手段,改性后羊毛粗纱的线密度由15.2 tex减小到14.7 tex,提高了粗纱羊毛纤维织物的服用性能。     

A-伸缩多小波集的一种刻划

基于对A-伸缩单小波集的研究,引入A-伸缩多小波集的概念,将A-伸缩单小波集是伸缩平移tiling的特征推广到A-伸缩多小波集.利用傅里叶变换及相关的集合知识,给出并证明了在L2(Rd)中可测集族{En}m-1n=1是A-伸缩多小波集的充要条件.     

Molecular characterization of Italian rice cultivars

Random amplified polymorphic DNA (RAPD) is an efficient tool to detect DNA polymorphisms and to distinguish different clones and cultivars. We have applied the RAPD technique to distinguish, starting from a single rice seed, among some Italian rice cultivars from market and from National Institute for research on food and nutrition, Italy. We also estimated the genomic similarity among the rice cultivars object of this study taking advantage of the amplification patterns. Despite the low genomic variability among Italian rice cultivars, RAPD technique allowed us to distinguish among them. This indicates that RAPD can be used routinely to verify the identity of Italian rice cultivars in order to prevent fraudulent commercial activity.     

淀粉基气凝胶的制备及其表征方法研究进展

淀粉基气凝胶是一种新型生物可降解材料,用于食品配料、营养素、药品的包埋与输送、包装、隔热等。淀粉基气凝胶具有高比表面积、高孔隙率、优良生物活性及可降解性等特点,是优良的载体材料。根据淀粉基气凝胶的形状不同,可分为淀粉基微球气凝胶和淀粉基块状气凝胶,淀粉基微球气凝胶应用范围较广,但其制备工艺较为复杂,本文主要对其制备及影响因素进行综述,分析其特性与结构表征,为淀粉基气凝胶的高效制备、有效表征、拓展应用提供参考。     

乙酰化香蕉淀粉的特性

通过与玉米淀粉比较,乙酰化香蕉淀粉的灰分、蛋白质、脂肪含量均比乙酰化玉米淀粉高.乙酰化香蕉淀粉糊的透明率在低温下出现较小的退化趋势,但常温下淀粉糊的透明率较高且有较好的稳定性.在较高温度下,乙酰化香蕉淀粉的持水能力比原淀粉高.乙酰化作用增加淀粉的溶解度和膨胀率.乙酰化作用也增加了香蕉淀粉糊的粘度值.     

苏氨酸锌的制备与表征

以苏氨酸和氧化锌为原料,在水溶液中反应合成了新型锌营养强化剂———苏氨酸锌螯合物。用EDTA络合滴定法、凯氏定氮法、IR、TG-DTA、ESI-MS等分析手段对制备的目的产物进行成分测定和结构表征,确定其化学式为C8H16N2O6Zn·2H2O。     

纳米ZnO的改性与表征

以尿素、醋酸锌为原料,采用微波水解法制备纳米ZnO,利用SiO2对纳米ZnO包覆改性,并通过XRD,TEM,分光光度计等对纳米ZnO的形状和尺寸进行表征,对其性能进行测试.结果表明,纳米ZnO改性的最佳工艺条件为：w（SiO2）=3%,时间0.5 h,温度80℃.纳米ZnO的比表面积改性前为20.21 m^2/g,改性后为14.65 m^2/g,且改性后纳米ZnO的吸光度明显提高.TEM显示纳米ZnO表面有明显的包覆层,说明用SiO2包覆纳米ZnO是可行的.     

聚乳酸的制备与性能研究

采用二步法由乳酸制备丙交酯,由丙交酯的开环聚合制备高分子量的聚乳酸。实验采用正交设计方法,通过改变催化剂种类、催化剂用量、脱水时间、环化时间四个主要影响因素进行实验,根据实验结果选择最好的丙交酯制备的实验方案。再次运用正交设计方法,通过改变催化剂种类、催化剂用量、反应时间、反应温度得到性能和分子量不同的聚乳酸,采用乌氏黏度计方法测定聚乳酸的分子量,利用傅立叶红外光谱和扫描电镜对聚乳酸的结构和形貌进行表征。     

纤维素氨基甲酸酯的合成及表征

系统地研究了纤维素氨基甲酸酯的合成方法、原料聚合度、合成温度及其时间、载体及其用量、尿素用量等对产物含氮量的影响。结果表明:载体的加入可提高反应试剂的可及度;纤维素浆粕的聚合度在320~390时反应性能较好;反应体系呈碱性时,有利于酯化反应的进行;产物含氮量随尿素用量的增大及预处理时间的延长而增加。最终确定最佳合成工艺条件为尿素用量40%,预处理2 h,酯化反应温度150℃,酯化反应时间3 h。产物的FT-IR谱图证实了酰胺键的存在。X-射线衍射表明产物的晶型与活化后纤维素的晶型类似,结晶度变化不大。     

Physico-chemical characterization of phosphate-added skim milk

The addition of potassium phosphate (KH₂PO₄) to milk is a common practice in the dairy industry but the changes resulting from such addition have not been fully elucidated. Physico-chemical changes were evaluated after addition of KH₂PO₄ at concentrations from 0 to 160 mm with or without adjustment of pH. At pH adjusted to 6.8, the addition of phosphate to milk-induced formation of insoluble calcium phosphate salt, decrease in lightness and solubilization of casein molecules. As a result of these biochemical changes, especially at high phosphate concentrations (about 120 mm and more), the formation of large aggregates occurred. At the same time, the amount of water combined with the modified casein strongly increased. When the pH was not adjusted, the same biochemical changes occurred but they were quantitatively lower. In this case, no destabilization of casein micelles occurred.