E. Jaime Vernon-Carter

Study of the antioxidant properties of extracts obtained from nopal cactus (Opuntia ficus-indica) cladodes after convective drying

BACKGROUND The process of convective drying was evaluated in terms of the bioactive compounds contained in nopal samples before and after dehydration. Total polyphenol, flavonoid, flavonol, carotene and ascorbic acid contents were determined in undehydrated and dehydrated samples. Two drying temperatures (45 and 65 °C) and two air flow rates (3 and 5 m s(-1) ) were evaluated. The rheology of samples under the best drying conditions was also studied, since it provides important information regarding processing (mixing, flow processing) as well as the sensory attributes (texture) of rehydrated samples. RESULTS Non-Newtonian shear-thinning behaviour was observed for samples dried at 45 °C, while samples dried at 65 °C showed shear-thickening behaviour, possibly caused by thermal chain scission of high-molecular-weight components. CONCLUSION The best conditions for bioactive compound preservation were a drying temperature of 45 °C and an air flow rate of 3 m s(-1) , resulting in 40.97 g phenols, 23.41 g flavonoids, 0.543 g β-carotene and 0.2815 g ascorbic acid kg(-1) sample as shown in table 3.

High intensity ultrasound treatment of faba bean (Vicia faba L.) protein: Effect on surface properties, foaming ability and structural changes

Response surface methodology was used for establishing the amplitude (72.67%) and time (17.29 min) high-intensity ultrasound (HIUS) conditions leading to an optimized faba bean protein isolate (OFPI) with lower interfacial tension, zeta potential and viscosity, and higher solubility than native faba bean protein isolate (NFPI). OFPI showed significantly higher adsorption dynamics at the air-water interface, and produced foam with significant smaller bubble diameter, higher overrun, stability and yield stress, and lower liquid drainage than NFPI. Fourier Transform Spectroscopy (FT-IR) revealed that the secondary structure of OFPI deferred from NFPI in terms of increases in β conformations (6.61% β-sheet, 19.6% β-turn, 0.8% anti-parallel β-sheet) and decreases in inter-molecular aggregates (43.54%). Multienzyme study pinpointed that the structural changes could have induced a decrease on the relative protein digestibility of OFPI respect that of NFPI. The results of this work demonstrate that HIUS technology improves the surface and foaming properties of faba bean protein isolate, which may favour the revalorisation of this crop.

Mesquite gum/chitosan insoluble complexes: relationship between the water state and viscoelastic properties

Abstract The aim of this work was to form polyelectrolyte complexes (PECs) mesquite gum (MG) and chitosan (Ch), as a function of the biopolymer mixing ratio (RMG/Ch). The water state during PECs formation was monitored as a way of assessing its effect on the viscoelastic properties. The maximum difference of zeta potential values for polyelectrolyte solutions as a function of pH was found in the range from 4.0 to 5.0. PECs were obtained with zeta potential values of ∼ |< 10 mV| between R7 – R12 at a pH of 4.5. This condition was favorable for producing high insoluble-PECs yield (92.16 ± 0.56%). The viscoelastic properties and water state assessed the insoluble-PECs interactions. The insoluble-PECs exhibited a liquid-like behavior, typical of concentrated solutions. Similar loss modulus was observed independently of the RMG/Ch. (G” ∼ 20 Pa, ω = 1 rad/s). DSC analysis showed that the water content influences the water state of insoluble-PECs. Freezing water increased exponentially with the increase of the water content independently of the RMG/Ch. Nonfreezing water reached a maximum value of 37% around of 50% of water content, showing the hydrophobic nature of insoluble-PECs. This work will support futures studies to use PECs for foods and pharmaceutical applications. Graphical Abstract