教学课程资源库 更多>>

关键词： skim milk powder dispersion   casein micelle   calcium chelator   colloidal calcium phosphate  

摘要： Due to health benefits of proteins, the demand for protein beverages has grown rapidly. Translucent protein drinks with neutral pH may have advantages over acidic beverages that may cause dental erosion, and skim milk powder (SMP) is an affordable protein ingredient. Dissociating casein micelles by calcium chelators is a well-known method to reduce SMP dispersion turbidity, but much is to be studied for physicochemical properties as affected by chelator type and concentration. The objective of the present study was to characterize physicochemical properties of dispersions with 5% (wt/vol) SMP after addition of 0 to 30 mM sodium tripolyphosphate, trisodium citrate, or sodium hexametaphosphate. The turbidity was decreased with increasing chelator concentration, with the lowest turbidity observed in the SMP dispersions with sodium hexametaphosphate. The smallest hydrodynamic diameter was observed at an intermediate chelator concentration, resulting from the balance of casein micelle dissociation and aggregation of dissociated caseins induced at an elevated ionic strength. Heating at 90 degrees C for 5 min increased turbidity but lowered hydrodynamic diameter of SMP dispersions, with some exceptions. The morphology of SMP dispersions differed for each chelator and was also affected by chelator concentration and heating. Trisodium citrate was the most effective to demineralize colloidal calcium phosphate in casein micelles, but the amount of dissolved calcium was not directly correlated with the decreased turbidity, indicating different chelating mechanisms by each chelator. Analysis of serum calcium and phosphorus concentrations also suggested that the type and concentration of soluble and insoluble calcium phosphates and their partitioning in the serum and casein micelles were dynamically changed by the studied parameters to affect dispersion turbidity and structures of casein micelles. Findings from the present study may be used to formulate translucent beverages inco

关键词： WDLC coatings   Ionic liquids   Glycerol   Close-to-ultra-low friction   Wear-resistant coatings   XPS   ToF-SIMS   Tribofilm   Green tribology  

摘要： An interaction between tungsten-doped diamond-like-carbon (WDLC) coatings and ionic-liquid (IL) additives under boundary-lubrication conditions is investigated. Three phosphate-based IL additives were employed: two had dimethylphosphate anion however, third one hydrolytic trifluorophosphate anion. In tribological tests, low friction (0.024) was achieved at 10 N and 100 degrees C with both dimethylphosphate containing IL additives. In contrast, IL with the trifluorophosphate anion had the poorest performance of all the ILs. Surface analyses revealed the thermal dissociation of dimethylphosphate into phosphate radicals which interacted with the WDLC surface to form phosphate-based tribofilm, which provides an easy shear thus reduces the friction. However, trifluorophosphate anions are thermally stable in given conditions and don't form a tribofilm on the WDLC surface hence show poor tribological performance.

关键词： Micellar casein concentrate (MCC)   Casein (CN)   Z-average (Z-avg)   Microfiltration (MF)   Whey proteins (WP)  

摘要： In the present study, the physicochemical properties of micellar casein concentrate (MCC) prepared from skim milk (buffalo and cow), using microfiltration (MF), were assessed. There was no significant difference (P > 0.05) between the average particle size of skim milk casein micelles (cow and buffalo) and their respective MCC. The casein-to-whey protein ratio increased from 4.91 and 4.75 in skim milk to 135.16 and 159.22 in MCC of buffalo and cow, respectively. Transmission electron microscopy (TEM) images showed an interwoven intact structure in both buffalo skim milk and MCC as compared to cow MCC. MCC showed excellent heat stability with type B characteristic curve.

关键词： Orbignya phalerata Mart.   Vegetable oil   Raw material for food industry   Fatty acids   TAG   DSC   TGA   Thermal properties  

摘要： Babassu oil is a raw material widely used in the pharmaceutical and biofuels industry. However, its physical-chemical and thermal characteristics are not widely described in the literature. This article describes these characteristics and, thus, seeks to increase the application of this raw material in the food industry. In this work, two different types of babassu oils, extra-virgin and virgin, were studied. The physicochemical characteristics, lipid profile, composition of the triacylglycerol and thermal properties of both oils were determined. Moreover, the crystallization and melting behavior was determined and the FTIR-ATR spectra of the oils acquired. The results show that the main fatty acids present are medium-chain and the type of extraction modifies the amounts of fatty acids present in each type of oil. Despite this, its physical-chemical characteristics and thermal properties are the same, except color and thermal stability, where extra-virgin oil is lighter and more stable than virgin babassu oil.

关键词： Chitosan film   Deep eutectic solvent   Choline chloride   Malonic acid   Mechanical properties   Food packaging  

摘要： This paper concerns novel, biodegradable and nontoxic materials for food-packaging. In order to obtain these properties, chitosan (Ch) and choline chloride (ChCl)-based deep eutectic solvent (DES) with malonic acid (MA), were used. The use of ChCl-MA mixtures as a potential plasticizer of chitosan (DD = 72 and 83%) films was proposed. All films with DES content ranging from 0 to 80 wt% were successfully prepared by a solution casting method. The properties of the DES-modified films were compared to those of the unmodified chitosan films. The effect of DES content on the structural (FTIR, SEM and AFM methods), mechanical, thermal and barrier properties of chitosan films was studied. The addition of ChCl:MA resulted in a significant increase in the elasticity. Chitosan films containing 80 wt% of DES exhibits Young's modulus lower by ca. 2400 MPa in comparison to the native chitosan films. According to the AFM images, chitosan-DES films possess higher roughness compared to the unmodified ones. Thermal properties were also influenced by the presence and content of DES due to the lower thermal stability of ChCl:MA mixture. Evaluation of water vapor permeability confirmed an increase in this parameter for all DES-modified films. Observed changes in chitosan properties increase the potential of this material being successfully used in food packaging.

关键词： Lotus seed starch nanoparticles   Ultrasonic-assisted enzymatic hydrolysis   Physicochemical properties   Small-sized  

摘要： Lotus seed starch nanoparticles were prepared by ultrasonic (ultrasonic power: 200 W, 600 W, 1000 W;time: 5 min, 15 min, 25 min;liquid ratio (starch: buffer solution): 1%, 3%, 5%) assisted enzymatic hydrolysis (LS-SNPs represent lotus seed starch nanoparticles prepared by enzymatic hydrolysis and U-LS-SNPs represent lotus seed starch nanoparticles prepared by high pressure homogenization-assisted enzymatic hydrolysis). The structure and physicochemical properties of U-LS-SNPs were studied by laser particle size analysis, scanning electron microscope, X-ray diffraction, Raman spectroscopy, nuclear magnetic resonance and gel permeation chromatography system. The results of scanning electron microscopy showed that the surface of U-LS-SNPs was cracked and uneven after ultrasonic-assisted enzymolysis, and there was no significant difference from LS-SNPs. The results of particle size analysis and gel permeation chromatography showed that the particle size of U-LS-SNPs (except 5% treatment group) was smaller than that of LS-SNPs. With the increase of ultrasonic power and time, the weight average molecular gradually decreased. The results of X-ray diffraction and Raman spectroscopy showed that ultrasonic waves first acted on the amorphous region of starch granules. With the increase of ultrasonic power and time, the relative crystallinity of U-LS-SNPs increased first and then decreased. The group (600 W, 15 min, 3%) had the highest relative crystallinity. The results of nuclear magnetic resonance studies showed that the hydrogen bond and double helix structure of starch were destroyed by ultrasound, and the double helix structure strength of U-LS-SNPs was weakened compared with LS-SNPs. In summary, U-LS-SNPs with the small-sized and the highest crystallinity can be prepared under the conditions of ultrasonic power of 600 W, time of 15 min and material-liquid ratio of 3%.

关键词： corn flour   fermentation   Lactobacillus plantarumY1   proteins   starch  

摘要： Corn flour is fermented withLactobacillus plantarumY1 at 37 degrees C for 60 h to modify its functional properties. The effects of the fermentation on structural and physicochemical properties of corn flour, starch, zein, and glutelin are investigated. Swelling power, solubility, water binding capacity, and light transmittance of corn flour increases significantly after fermentation. The fermentation process reduces the hardness and retrogradation tendency of corn flour dough;while, viscidity, elasticity, and cohesiveness of corn flour dough enhances after fermentation. Microscopy analysis shows that the surface structure of corn flour particles and starch granules become porous after fermentation. Starch isolated from the fermented corn flour shows greater viscosity, pasting temperature, and enthalpy values than those of starch isolated from ordinary corn flour. Zein hydrolyzes moderately and its secondary structure becomes more regular and ordered after fermentation. However, glutelin hydrolyzes to a greater extent and its secondary structure tends to be disordered after fermentation. Cakes made of the fermented corn flour show lower hardness and greater chewiness compared to those of cakes made of the ordinary corn flour. The obtained results indicate that the functional properties of corn flour can be successfully improved by the fermentation withL. plantarumY1.

关键词： Potatoes   Parenchyma cells   Starch gelatinisation   In vitro digestion   Cell walls   Microstructure  

摘要： Intact parenchyma cells and native starch granules were isolated from Agria and Sunlite potato (Solanum tuberosum L.) cultivars. Their morphology, physicochemical properties, and in vitro starch digestion were investigated. Parenchyma cells varied in shape, size, and composition. Each cell contained numerous starch granules enveloped by a cell wall. Starch inside Agria cells exhibited higher gelatinisation temperatures than isolated Agria starch. For both cultivars, starch inside cells had higher peak and breakdown paste viscosities than isolated starch. Cooked cells and isolated starches exhibited similar in vitro starch hydrolysis profiles. These results indicate that the entrapment of starch granules in parenchyma cell walls affected thermal and pasting properties of starch, but had no effect on starch digestion kinetics in vitro. The study provides evidence supporting the use of dehydrated parenchyma cells by the food industry for development of novel potato-based food products with desirable physical properties.

关键词： solid dispersions   solubility   benzonal   polyvinylpyrrolidone (PVP)   polyethylene glycol (PEG)   beta-cyclodextrin  

摘要： The influence of solid dispersions (SDs) on some physicochemical properties of benzonal is studied. Investigated: benzonal and its SD with polyvinylpyrrolidone-10 000 (PVP), polyethylene glycol-1500 (PEG), beta-cyclodextrin (CD). The preparation of SD by the solvent removal method increases the solubility and dissolution rate of benzonal in water. The solubility increases by 3.5-5.5 times;and the speed of dissolving, by 4.0-10.0 times. The complex of physical and chemical research methods suggests that the preparation of an SD with the studied polymers is accompanied by loss of crystallinity and formation of a solid solution of benzonal in the polymer, as well as solubilization and formation of colloidal solutions of benzonal during subsequent dissolution of SD in water. The results obtained can be used in the development of fast-dissolving benzonal tablets with increased release and bioavailability.

关键词： Veterinary drugs   Antibiotics   Fermentation   Heat treatment   Milk   Cheese   Food safety  

摘要： Considering the widespread use of the antibiotic monensin (MON) in the Brazilian livestock and the possibility of residues in milk, this paper aimed to study the stability and fate of this drug during the production of Brazilian Minas Frescal cheese, its effects on milk fermentation and on the physicochemical characteristics of this product. For that, samples of raw milk were fortified with MON at three different nominal concentrations (1.0, 2.0 and 8.0 mu g/kg), passed through heat treatment and used to produce Minas Frescal cheese. Pasteurization efficiency was certified by alkaline phosphatase and peroxidase enzyme tests and cheese samples were evaluated for pH, moisture and total protein and fat content. MON residues were determined by LC-MS/MS in the following steps: raw milk, heat-treated milk, whey and cheese. No significant degradation of MON due to heat treatment was observed, suggesting that the drug is resistant to high temperatures. Moreover, the residue levels quantified in cheese and whey demonstrated a concentration of this antibiotic in the curd by about 5-fold, with a small amount of MON being lost during draining. There were no significant differences (p > 0.05) considering the physicochemical parameters evaluated in cheese samples. Fermentation was also not affected by the presence of the drug. The results showed that residues of MON in milk are stable during cheese production and may be concentrated in the final product, as well as indicate the need to establish a MON safe residue level for this food commodity.