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Giampiero Sacchetti Paola Pittia Manuela Biserni Gian G. Pinnavaia & Marco D. Rosa 《International Journal of Food Science & Technology》2003,38(2):135-143
Summary Ready‐to‐eat breakfast cereals immersed in milk undergo undesirable changes in texture because of sudden moisture uptake. The textural changes are ascribable to a plasticizing effect of water, which modifies the mechanical strength of products by softening the starch/protein matrix. In this work, some textural parameters of different cereal flakes were derived from the force–displacement curves monitored during 300 s of immersion in milk. Hardness loss, deformability increment and changes in the force–displacement curve profile were calculated and plotted against soaking time. The application of a sugar coating process to a model cereal flake increased the initial product hardness and improved the preservation of the textural parameters during immersion. The Peleg model closely fitted the experimental data, with regression coefficients from 0.967 to 0.999. 相似文献
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Fa‐Ai Zhang Ming Luo Zheng‐Ji Chen Zhi‐Bo Wei Thomas J. Pinnavaia 《Polymer Engineering and Science》2014,54(12):2746-2752
Rod‐like and spherical mesoporous SBA‐15 silica particles were synthesized as pure silicas and surface modified by organosilane coupling agents firstly, and then the effects of these mesoporous materials on the critical micelle concentration (CMC) of sodium dodecylsulfate (SDS), the stabilities of batch and semi‐continuous MMA emulsion polymerizations, and the molecular weights and molecular weight distributions of the polymer products were studied. The incorporation of both unmodified and silane‐modified forms of the mesoporous silica particles in the polymerization reaction increased the CMC of SDS. The presence of the unmodified mesoporous silica in the polymerization process led to instability in the batch emulsion polymerization process, as indicated by the formation of increased amounts of coagulum, and a decrease in the molecular weight of the polymer product. However, in comparison to the polymer formed in the absence of particle additives the molecular weight of the PMMA polymer increased with the amount of emulsifier and the addition of silane‐modified SBA‐15 particles, suggesting the growth of the polymer chains is facilitated at least in part by reaction in the pores of the particles. The improvement in molecular weight indicates that semi‐continuous MMA emulsion polymerization is best suited for the preparation of PMMA–mesoporous silica composites. POLYM. ENG. SCI., 54:2746–2752, 2014. © 2013 Society of Plastics Engineers 相似文献
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K.S. Triantafyllidis A.A. Lappas I.A. Vasalos Y. Liu H. Wang T.J. Pinnavaia 《Catalysis Today》2006,112(1-4):33-36
Aluminosilicate mesostructures (MSU-SBEA) assembled from zeolite Beta (BEA) seeds exhibited relatively high hydrothermal stability and were significantly more active in the cracking of gas–oil compared to MCM-41 after severe steaming pretreatment. The MSU-SBEA mesoporous materials with wormhole framework structure and those having morphology of solid nanoparticles with high interparticle mesoporosity were more steam-stable and more active after severe steaming than those with hexagonal pore structure. Differences in acid sites strength between the MSU-SBEA materials and MCM-41 could not be probed by the complex reaction system of the large hydrocarbon molecules of gas–oil. 相似文献
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Despoina D. Asouhidou Kostas S. Triantafyllidis Nikolaos K. Lazaridis Kostas A. Matis Seong-Su Kim Thomas J. Pinnavaia 《Microporous and mesoporous materials》2009,117(1-2):257-267
In the present study two synthetic mesoporous carbons, a highly ordered CMK-3 sample with hexagonal structure and a disordered mesoporous carbon (denoted DMC) were investigated for the sorption of Remazol Red 3BS (C.I. 239) dye in comparison to three commercial activated carbons and a HMS mesoporous silica with a wormhole pore structure. The structural, porosity and surface characteristics of the materials were evaluated using XRD, TEM, N2 porosimetry, FT-IR spectroscopy and zeta-potential measurements. Optimal dye sorption occurred at pH ~2. Equilibrium sorption data followed the Langmuir model and showed that the two synthetic mesoporous carbons exhibit higher sorption capacities (qmax ~ 500–580 mg/g at 25 °C) in comparison to the commercial activated carbons which possessed either microporous (Takeda 5A and Calgon carbon) or combined micro-/mesoporous (Norit SAE-2) structures and to the HMS mesoporous silica. Thermodynamic parameters as the change in free energy, enthalpy, and entropy of sorption were also estimated. Kinetic studies were carried out and showed a rapid sorption of dye in the first ca. 30 min while equilibrium was reached after ca. 3 h. The sorption kinetics of dye was best described by a second-order kinetic model. A surfactant enhanced carbon regeneration (SECR) technique was used to regenerate the dye-loaded carbon sorbents. 相似文献
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A.J. Karkamkar S.‐S. Kim S.D. Mahanti T.J. Pinnavaia 《Advanced functional materials》2004,14(5):507-512
We describe the hierarchical structures of mesostructured silicas assembled from electrically neutral and unsymmetrical Gemini surfactants of the type CnH2n+1NH(CH2)mNH2 with n = 10, 12, 14 and m = 3, 4. As expected for Gemini surfactants with an all anti‐chain configuration and a packing parameter near 1.0, lamellar framework structures are formed, regardless of the length of the alkyl chain (n) and the number of carbon atoms (m) linking the two amino group centers. However, different layer curvatures and levels of hierarchical structure are observed depending on the delicate balance between the hydrophilic interactions at the surfactant head group–silica interface and the hydrophobic interactions between the surfactant alkyl groups. For Gemini derivatives with n = 12 or 14 and m = 3 or 4, well‐expressed hierarchical vesicles are formed that are analogous to those assembled previously from Gemini surfactants with m = 2. However, for n = 10, a new coiled slab structure (m = 3) and an onion‐like core–shell structure (m = 4) are formed. In addition, a previously unobserved stripe‐like silica structure is obtained from a C012+2+0 Gemini surfactant in combination with an α,ω‐diamine co‐surfactant. The relative stability of these hierarchical structures depends on the delicate competition between the long‐range elastic forces occurring in the hydrophobic region of the assembled surfactant and the short‐range chemical forces in the hydrophilic moiety. Lamellar silicas with hierarchical vesicular structures, the new coiled slab, and stripe‐like phases promise to be chemically significant morphologies, because they can minimize the framework pore length and provide optimal access to the framework walls under diffusion‐limited conditions. 相似文献
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Abstract
Representative members of a new class of commercially available Gemini surfactants, namely, the alkyloxypropyl-1,3-diaminopropanes, are shown to template the direct assembly of mesoporous silicas with lamellar framework structures. The hydrolysis of tetraethylorthosilicate in the presence of a derivative with a straight hydrophobic chain, C n H2n+1O(CH2)3NH(CH2)3NH2 with n = 8 and 10 (Tomah3 DA1214), afforded a layered mesophase with a surface area of 464 m2/g, a pore volume of 0.39 cm3/g, a pore size of 3.6 nm and a vesicular hierarchical structure. The introduction of electrostatic forces into the assembly process through the protonation of up to 33% of the amine centers improves the quality of the lamellar framework order as evidenced by increases in X-ray diffraction and textural properties. Also, the vesicular hierarchical structure formed under electrically neutral assembly conditions is replaced by well dispersed multilamellar nanoparticles upon surfactant protonation. Chain branching in the hydrophobic segment of Gemini derivative i-C10H21O(CH2)3NH(CH2)3NH2 (Tomah3 DA14) compromises the quality of the lamellar framework structure, but affords higly dispersed nanoparticles with hierarchical coiled slab to vesicular motifs depending on the degree of surfactant protonation. In addition to providing unusual lamellar framework structures, these Gemini surfactants afford hierarchical nanoparticle motifs of relatively uniform size (50–200 nm) and a very high degree of dispersion for a potential use in a variety of materials applications. 相似文献10.
Influence of processing and storage on the antioxidant activity of apple derivatives 总被引:2,自引:0,他引:2
Giampiero Sacchetti Emiliano Cocci GianGaetano Pinnavaia Dino Mastrocola & Marco Dalla Rosa 《International Journal of Food Science & Technology》2008,43(5):797-804
The antioxidant activity of seven apple varieties was determined on fresh fruits and processed products (dried fruits and purees) and during storage. The antioxidant activity of apples correlated with the total phenol concentration but not with ascorbic acid concentration. Apple derivatives showed a lower antioxidant activity than the counterparts of the fresh fruits and the occurrence of browning phenomena during processing resulted in lower antioxidant activity. Dried fruits showed higher antioxidant activity per gram of dried matter than fruit purees probably because of the lower total thermal effect of processing. The antioxidant activity of all products increased within the first month of storage, and then declined. The extent of early increase was related to the polyphenol content of the fruit. Packaging conditions further influenced the antioxidant activity increase during storage possibly by affecting the oxygen availability. 相似文献