Optimising the Polyphenolic Content and Antioxidant Activity of Green Rooibos () Using Beta-Cyclodextrin Assisted Extraction.

Antioxidant activity associated with green rooibos infusions is attributed to the activity of polyphenols, particularly aspalathin and nothofagin. This study aimed to optimise β-cyclodextrin (β-CD)-assisted extraction of crude green rooibos (CGRE) via total polyphenolic content (TPC) and antioxidant activity assays. Response surface methodology (RSM) permitted optimisation of β-CD concentration (0−15 mM), temperature (40−90 °C) and time (15−60 min).

Paclitaxel/β-Cyclodextrin interactions, a perspective from pulsed NMR spectroscopy experiments.

Cyclodextrins are cyclic cone shaped oligosaccharides. A guest molecule can be incorporated into the hydrophobic inner of the cyclodextrin to form non-covalent complexes. The formation of these complexes in general, increases the solubility, stability, dissolution rate, and bioavailability of drugs with poor water solubility.

About the endothermal transitions of galactomannans: A multi-analytical DSC, LF-H NMR and DMA study.

The thermal transitions of biopolymers were subject of great discussion in the 90s due to their relevance in structure development during processing and stability on storage. In the present work two galactomannans, vinal gum and guar gum, were evaluated by DSC, DMA and LF-H NMR in order to compare them, establishing their potential operational application range and promoting the use of the non-conventional VG in foods or other products. Three endothermal transitions appeared when heating the samples in the DSC: one at temperatures -90 to -10 °C (LTT), other around 50 °C (MTT) and a third one between 50 and 100 °C (HTT).

Detection of quinoa flour adulteration by means of FT-MIR spectroscopy combined with chemometric methods.

Quinoa flour has been receiving an increasing attention as a substitute for wheat flour in bread formulations due to immuno-nutritional features. This growing interest in quinoa has increased the demand and consequently the prices, being a target for possible adulterations with cheaper cereals. Fourier transform Mid-infrared spectroscopy (FT-MIR) was used in the present work as a fingerprinting technique to detect the presence of three adulterants (soybean, maize and wheat flours).

Carotenoid and color changes in traditionally flaked and extruded products.

The objective of this study was to evaluate the impact of process and formulation on individual carotenoid loss in traditionally prepared cornflakes and those prepared by extrusion. The first step in the traditional process (maize grits cooking) promoted a 60% lutein content reduction and 40% in zeaxanthin loss, showing lutein more susceptibility to isomerization and decomposition. After toasting, the last step, the total loss averaged 80% for both compounds.

Formation of complexes between hematite nanoparticles and a non-conventional galactomannan gum. Toward a better understanding on interaction processes.

The physicochemical characteristics of hematite nanoparticles related to their size, surface area and reactivity make them useful for many applications, as well as suitable models to study aggregation kinetics. For several applications (such as remediation of contaminated groundwater) it is crucial to maintain the stability of hematite nanoparticle suspensions in order to assure their arrival to the target place. The use of biopolymers has been proposed as a suitable environmentally friendly option to avoid nanoparticle aggregation and assure their stability.

Impact of supramolecular interactions of dextran-β-cyclodextrin polymers on invertase activity in freeze-dried systems.

β-Cyclodextrin (β-CD)-grafted dextrans with spacer arms of different length were employed to evaluate the impact of supramolecular interactions on invertase activity. The modified dextrans were used as single additives or combined with trehalose in freeze-dried formulations containing invertase. Enzyme activity conservation was analyzed after freeze-drying and thermal treatment.

Impact of protective agents and drying methods on desiccation tolerance of Salix nigra L. seeds.

Willow seeds are classified as orthodox, but they show some recalcitrant characteristics, as they lose viability in a few weeks at room temperature. The aim of this work was to improve the desiccation tolerance of willow seeds (Salix nigra L.), as a model of sensitive materials to dehydration, through imbibition in solutions and later vacuum (VD) or freeze-drying (FD).

Polyethylene glycol-based low generation dendrimers functionalized with β-cyclodextrin as cryo- and dehydro-protectant of catalase formulations.

Polyethylene glycol (PEG)-based low generation dendrimers are analyzed as single excipient or combined with trehalose in relation to their structure and efficiency as enzyme stabilizers during freeze-thawing, freeze-drying, and thermal treatment. A novel functional dendrimer (DGo -CD) based on the known PEG's ability as cryo-protector and β-CD as supramolecular stabilizing agent is presented. During freeze-thawing, PEG and β-CD failed to prevent catalase denaturation, while dendrimers, and especially DGo -CD, offered the better protection to the enzyme.

Formulation and drying of alginate beads for controlled release and stabilization of invertase.

Several alternatives to the conventional alginate beads formulation were studied for encapsulation of invertase. Pectin was added to the alginate/enzyme solution while trehalose and β-cyclodextrin were added to the calcium gelation media. The effect of composition changes, freezing, drying methods (freeze, vacuum, or air drying), and thermal treatment were evaluated on invertase stability and its release kinetics from beads.

Degradation of β-carotene in amorphous polymer matrices. Effect of water sorption properties and physical state.

Background: The use of encapsulation in amorphous matrices of carbohydrate and/or polymer formed during dehydration processes to enhance the stability and retention of labile compounds is increasing in the food and pharmaceutical industries. Efforts to improve encapsulating properties have been made using mixtures of carbohydrates with proteins or gums in different proportions. The objective of the present work was to study the stability of encapsulated β-carotene and its degradation kinetics in maltodextrin/gum arabic and maltodextrin/gelatin matrices in relation to the physical properties and state of the dehydrated matrix.

Multi-level approach for the analysis of water effects in corn flakes.

The purpose of this work was to analyze the effect of water on thermal transitions, mechanical properties, and molecular mobility in corn flakes (CF), and their relationships. Commercial common (CCF) and sugar-frosted (SCF) corn flakes were studied in a water content (wc) range from 5 to 20 (% dry basis). The slope of (1)H NMR spin-spin relaxation time T 2* (determined by FID) versus temperature plot changed close to T g.

Non-enzymatic browning kinetics analysed through water-solids interactions and water mobility in dehydrated potato.

Non-enzymatic browning (NEB) development was studied in dehydrated potato at 70°C. It was related to the macroscopic and molecular properties and to water-solid interactions over a wide range of water activities. Time resolved (1)H NMR, thermal transitions and water sorption isotherms were evaluated.

Structure/function relationships of several biopolymers as related to invertase stability in dehydrated systems.

Structure/function relationships of different biopolymers (alginate, dextran, or beta-cyclodextrin) were analyzed as single excipients or combined with trehalose in relation to their efficiency as enzyme stabilizers in freeze-dried formulations and compared to trehalose. Particularly, a novel synthesized polymer beta-cyclodextrin-branched alginate (beta-CD-A) was employed as excipient. During freeze-drying, the polymers or their mixtures did not confer better protection to invertase compared to trehalose.

Structural collapse prevents beta-carotene loss in a supercooled polymeric matrix.

The kinetics of degradation and surface color changes of beta-carotene encapsulated in a polymeric matrix (PVP-40) and its relationship with physical changes (manifested as structural collapse) of the matrix were studied during storage of samples at several water activities at constant temperature. The degradation rate constants obtained decreased with an increase in the relative humidity (RH) of the storage atmosphere. Beta-carotene losses were observed mainly at RHs below the glass transition temperature (Tg) of the corresponding systems, and the lower degradation constant rates were observed under conditions where the matrices were fully plasticized (i.

Inhibition of trehalose crystallization by cytoplasmic yeast components.

The influence of different yeast (Saccharomyces cerevisiae) cellular fractions was studied in an attempt to gain knowledge on the feasibility of trehalose crystallization in yeast cells. Certain constituents of S. cerevisiae cells inhibited/delayed trehalose crystallization upon humidification at high relative humidities.

Fluorescence from the maillard reaction and its potential applications in food science.

The chemistry of the Maillard reaction involves a complex set of steps, and its interpretation represents a challenge in basic and applied aspects of Food Science. Fluorescent compounds have been recognized as important early markers of the reaction in food products since 1942. However, the recent advances in the characterization of fluorophores' development were observed in biological and biomedical areas.

Commercial baker's yeast stability as affected by intracellular content of trehalose, dehydration procedure and the physical properties of external matrices.

The effects of vacuum-drying and freeze-drying on the cell viability of a commercial baker's yeast, Saccharomyces cerevisiae, strain with different endogenous contents of trehalose were analyzed. An osmotolerant Zygosaccharomyces rouxii strain was used for comparative purposes. Higher viability values were observed in cells after vacuum-drying than after freeze-drying.

Glass transition temperatures and fermentative activity of heat-treated commercial active dry yeasts.

Differential scanning calorimetry thermograms of various samples of commercial instant active dry yeasts revealed a clear glass transition typical of amorphous carbohydrates and sugars. The resulting glass transition temperatures were found to decrease with increasing moisture content. The observed glass curve was similar to that of pure trehalose, which is known to accumulate in large amounts in baker's yeast.

Combined effects of trehalose and cations on the thermal resistance of beta-galactosidase in freeze-dried systems.

The purpose of this study was to investigate the combined effects of trehalose and cations on the preservation of beta-galactosidase in freeze-dried systems and their relationship to physical properties. Differential scanning calorimetry was employed to measure the glass transition temperature (T(g)) and the endothermal peak area, related to the amount of crystalline trehalose dihydrate present in the samples. In systems in which the trehalose matrix was humidified to conditions which allowed a high proportion of trehalose to crystallize, the enzyme was rapidly inactivated upon heating at 70 degrees C.