教学课程资源库 更多>>

关键词： Superior grains   Chain length distribution   Thermal properties   Rice texture  

摘要： The difference between superior grains (SG) and inferior grains (IG) is an important factor that directly determines rice yield and quality. In this study, four varieties with different amylose contents were used to examine differences in the starch structure, physicochemical and functional properties as well as texture characteristics between SG and IG. A higher amylose content (AAC), long chain (degree of polymerization >= 37) content, average degree of polymerization, and larger granule size were observed in SG, while the short chain (DP 6-12) content and relative crystallinity showed the opposite result. This resulted in a lower swelling factor, higher gelatinization temperature, retrogradation tendency and harder texture in SG. SG were found to have higher slowly digestible starch (SDS) and resistant starch (RS) contents compared with IG, which means a better functional properties. This study indicated that higher amylose and long-chain amylopectin contents in SG probably degrades the rice eating and cooking qualities but improves functional properties as compared with IG.

关键词： Betalain   Oil-in-water emulsion   Non-Newtonian fluid   Storage stability   Sustained release  

摘要： Red beetroot extract is a widely used food colorant. Betalain is the major red pigment present in it, which is unstable at high temperature and pH. In this study, the edge of nanoemulsion over microemulsion in improving the thermal and pH stability of betalain has been demonstrated. The micro- and nanoemulsions of beet extract were prepared by rotor-stator homogenization and rotor-stator homogenization followed by ultrasonication, respectively. The resultant emulsions were compared for their physicochemical and rheological properties, storage stability (for 15 days, at refrigeration temperature: 4 +/- 1 degrees C;room temperature: 30 +/- 5 degrees C;40 degrees C and 100 degrees C), and release kinetics. Compared to microemulsion, nanoemulsion resulted in a sustained release and higher thermal and pH stabilities of betalain. During storage, nanoemulsion showed a lower rate of droplet coarsening and improved color stability than microemulsion, due to its nanoscale droplet diameter (701.53 +/- 27.2 nm), high viscosity (0.089 Pa s, at 100 s(-1)), and non-Newtonian rheological behavior.

关键词： Agricultural (environmental) weathering   Biodegradable plastic mulch film   Mulch degradation   Polylactic acid (PLA)   Polybutylene co-adipate   co-terephthalate (PBAT)  

摘要： Biodegradable plastic mulch films (BDMs) are essential in the production of vegetable and specialty crops due to their promotion of increased crop yield and quality. Unlike conventional polyethylene (PE) mulches, BDMs can be tilled into the soil after crop harvest to undergo biodegradation, thereby leading to minimal environmental impact. Agricultural weathering impacts both the performance of BDMs during crop production as a barrier to weeds and biodegradability of BDMs in the soil. To better understand the relative importance of climatic factors, the change of physicochemical properties of BDMs during single-season, 3-4 month, field trials for vegetable production at two diverse climates (Knoxville, TN and Mount Vernon, WA) across four successive years (2015-2018) was evaluated. Mulch treatments consisted of four commercially available BDMs composed primarily of polybutylene co-adipate- co-terephthalate (PBAT) that differed in color and polymeric feedstock, a black experimental BDM prepared from polylactic acid/polyhydroxybutyrate (PLA/PHA) blend, and conventional PE mulch. Solar radiation, an important factor to degradation of mulches, was higher in WA than TN in most sampling years. Yet, degradation occurred more greatly for BDMs in TN, which is attributable to higher temperatures in TN. Mulch deterioration did not very extensively between years. Loss of mechanical properties and color was greater than chemical property changes. Differences in the extent of molecular weight decrease between years correlated significantly with solar radiation exposure at the two locations. A black-colored PBAT-based BDM was less susceptible to degradation than equivalent clear and white-on-black films, due to carbon black acting as a photostabilizer. The impact of weathering also differed between three commercially available PBAT-based films. The PLA/PHA mulch was more susceptible to degradation than PBAT-based BDMs, particularly in the warmer location, TN, partially due to a lea

关键词： Sugar beet pectin   Dry-heating   Molecular polymerization   Emulsifying properties  

摘要： As a polyhydroxy carboxylic polymer, pectin is prone to physicochemical reactions under dehydration stress. This study investigated the molecular polymerization, structures and emulsifying properties of sugar beet pectin (SBP) after dry-heating at 45, 60, 75 and 110 degrees C for different lengths of time. When thermally treated, SBP molecules gradually cross-linked into insoluble and irregular-shaped flocs in a timeand temperature-dependent manner. The polymerized SBP was confirmed by high-performance size exclusion chromatography and dynamic light scattering techniques, and then morphologically characterized by a scanning electron microscope, which exposed a compact texture. Both soluble and insoluble SBP cross-linked polymers (named ISBP) were formed, depending on the dry-heating conditions. ISBP110 degrees C-2 h had a notably high protein content (16.2%), which evidenced the role of proteinaceous materials in constructing the cross-linked structures. Moreover, the FTIR and NMR spectroscopic bands relative to the amidation between amino and carboxyl groups suggested that SBP molecules might be covalently cross-linked with protein as the linker. The emulsifying properties of dry-heating treated SBP (75 degrees C for 12 h or 110 degrees C for 2 h) were significantly improved with the soluble cross-linked SBP with increased surface hydrophobicity. In that case, controlled dry-heating treatment could be employed as a simple method to improve the emulsifying activities of SBP. Altogether, this work demonstrates that the endogenous protein moiety plays an essential role in the polymerization of SBP under dry-heating, possibly via cross-linking SBP chains through the amidation with carboxyl groups of galacturonic acid residues.

关键词： Ultrasound   Micellar casein concentrates   Morphology   Thermal stability   Digestion  

摘要： In this study, microfiltered casein micelle retentates were treated with sonication within 15 min prior to spray drying, and the impact of ultrasound pretreatment on the physicochemical, functional, and digestion properties of the resultant micellar casein concentrates were investigated. The results showed that the intrinsic fluorescence intensities of casein samples increased after extending the ultrasound pretreatment time from 2 to 6 min, but decreased if pretreatment time was further prolonged;this was also true for the oil absorption capacity. Additionally, there was a reduction in particle size and thermal stability and an increase in the solubility of pretreated samples in the pH range of 4-8 compared with controls. Bulk and tapped density values decreased after extending the sonication time from 2 to 4 min, but increased if sonication time was further prolonged. No significant changes in the secondary structure of the samples were observed after sonication. An obvious disintegration of micellar casein particles was observed by scanning electron microscopy following ultrasound pretreatment times up to 10 min, resulting in improved digestibility in simulated intestinal fluid. Thus, we concluded that prolonged ultrasound pretreatment facilitates enhanced digestion of micellar casein concentrate and its products.

关键词： Pearl millet   Seeds   Starch   Paracetamol   Disintegrants  

摘要： Objectives. - The aim of the current study was to compare the physicochemical and disintegrant properties of pearl millet starch with other starches using paracetamol as model drug. Methodology. - Determination of percentage yield, Physicochemical, micrometrics characteristics of starch/granules, drug excipients compatibility studies and evaluation of prepared paracetamol tablets were measured using official techniques. Results. - The yield of the millet starch ranged from 30 to 40%. Moisture content 8.77%, pH 5.7, Swelling capacity 1.2, Hydration capacity 1.748, Moisture uptake 11.8%. Amylase 24.6%, with poor flowability and compressibility. No significant difference in hardness, friability% & disintegration times for formulations containing millet starch to that containing potato and maize starch (P > 0.05). Conclusion. - From the study, Millet seeds locally cultivated in Sudan gave a high yield of starch, has same physicochemical properties as maize and potato starch so can be used as an alternative to those starches. (C) 2020 Academie Nationale de Pharmacie. Published by Elsevier Masson SAS. All rights reserved.

关键词： Silane-grafted polyethylene   Stabilisation   Irganox 1076 (R)   Phenolic antioxidant   Heterogeneous distribution   Exudation  

摘要： This work focuses on the physico-chemical analysis of a silane-grafted polyethylene stabilised with an excess of Irganox 1076 (R) as phenolic antioxidant before and after surface cleaning using acetone as a polar solvent. The non-uniform distribution of Irganox 1076 (R) in this polymer matrix was investigated with several complementary characterisation techniques including FTIR spectroscopy (in both ATR and transmission modes), DSC analysis, OIT measurements, and optical microscopy. Initially, the presence of antioxidant crystals at the polymer surface was confirmed. Surface cleaning showed to be effective to remove all antioxidant crystals present at the polymer surface, as confirmed by FTIR spectroscopy in ATR mode, DSC analysis, and optical microscopy. The remaining concentration of antioxidant in the polymer matrix was estimated by FTIR spectroscopy in transmission mode and OIT measurements using preliminary established OIT and FTIR calibration curves. It was found that this concentration corresponds to the solubility threshold at 25 degrees C of about 0.9 wt% (i.e. approximate to 1.6 x 10(-2) mol.L-1) determined in a previous publication. Hence, all experimental results suggest that antioxidant crystals would only be present at the polymer surface, and not within the polymer bulk, which finally allows proposing a simplified microstructural model for this heterogeneously stabilised polymer. It was also found that antioxidant crystals efficiently participate to the stabilisation process of the polymer matrix during oxidation, thus significantly increasing the OIT. This important result might constitute an interesting stabilisation route for industry, still unexplored to date, obviously depending on the intended final application of the polymer. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Milk powder   Coagulation   Near infrared spectroscopy   Multivariate curve resolution   Alternating least squares   Rheological properties  

摘要： The effect of physicochemical factors and use of skim milk powder on milk rennet-coagulation was investigated combining near infrared (NIR) spectroscopic monitoring and Multivariate Curve Resolution Alternating Least Squares (MCR-ALS). Coagulum formation has been studied by reference approaches (Formagraph and funda-mental rheology) and with NIR spectroscopy on unaltered reconstituted milk samples, pasteurized samples, samples with calcium chloride addition and samples of reconstituted milk mixed with fresh milk. The MCR-ALS models successfully described the process evolution, explaining more than 99.9% of variance. The MCR-ALS profiles revealed to be significantly directly correlated with Formagraph and rheological data (p < 0.001) and allowed assessing the significant effect (p < 0.05) of the milk powder type on the coagulation occurrence and the non-significance (p 0.05) of the CaCl2 concentration level added and the heat treatment applied. The MCR-ALS models calculated for the coagulation trials of pasteurized skimmed milk mixed with reconstituted milk samples highlighted shorter coagulation times with the increasing of reconstituted milk amount (from 4.3-6.6 min to 2-5 min). Profiles extracted from MCR-ALS models developed for a wide range of coagulation conditions proved to be suitable non-destructive, non-invasive and on-line tools to evaluate the rennet-induced coagulation of reconstituted milks.

关键词： 物理化学   化学实验   高等学校   教材  

ISBN: (纸本)9787568017749

摘要： 本书是在总结物理化学教研组老师多年来教学经验基础上而编写的实验教材。全书包括绪论、基础实验、综合实验、实验测量仪器和附录部分，共有31个教学实验。这些实验内容与物理化学课程理论知识紧密联系，同时融入我校科学研究特色，体现物理化学多学科交叉的特点。本书可供高等院校化学、化工、材料科学、轻化工程等专业本科生使用，也可作为物理化学专业研究生的参考书，对相关科研技术人员也具有一定参考价值。

关键词： Microcrystalline cellulose   alfa fibers   delignification   hydrolysis   thermal stability   crystallinity  

摘要： Esparto grass, known as alfa, is a renewable biomass widely distributed in southern and western Mediterranean basin. The present work focused on the isolation of pure cellulose from alfa stems, via different approaches, i.e., acidified sodium chlorite (NaClO2), totally chlorine free (TCF) or their combination, followed by the preparation of microcrystalline cellulose (MCC) using acid hydrolysis method. The obtained samples were characterized using infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TGA) and differential scanning calorimeter (DSC). The FTIR spectroscopy exhibited the removal of lignin and hemicellulose after the delignification and alkaline treatments. The XRD data showed that all of the MCCs have higher crystallinity indexes (Alfa-MCC 73-82%) and belong to cellulose I type. From SEM images, it is clear that the different MCC particles presented rough surface and micro-sized particles. The DSC/TGA analyses revealed that MCC samples present better thermal stability than their respective cellulose ones, with higher temperature of decomposition (more than 350 degrees C). Moreover, the use of a combined process yields to MCC with higher crystallinity and better thermal stability. Consequently, based on these findings, the delignification with combined method can be considered as a promising approach to extract MCC from alfa fibers with outstanding features.