The Effect of High-Pressure Microfluidization Treatment on the Foaming Properties of Pea Albumin Aggregates

The effect of dynamic high-pressure treatment, also named microfluidization, on the surface properties of thermal pea albumin aggregates (AA) and their foaming ability was investigated at pH 3, 5, and 7. The solubility of albumin particles was not affected by the increase in microfluidization pressure from 70 to 130 MPa. Particle charge depended only on the pH, whereas protein surface hydrophobicity was stable at pH 5, decreased at pH 3, but increased at pH 7 after microfluidization treatment and with the applied pressure. Surface tension of AA measured at air/water interface was favorably affected by the microfluidization treatment at each pH preferentially due to size reduction and increased flexibility of protein particles. The foaming capacity and stability of AA depended on the pH conditions and the microfluidization treatment. The high-pressure treatment had little influence in foaming properties at acidic pHs, probably related to a more compact form of AA at these pHs. At neutral pH, the foaming properties of pea AA were strongly influenced by their surface properties and size associated with significant modifications in AA structure with microfluidization. Changes in albumin aggregate characteristics with pH and microfluidization pressure are also expected to modulate other techno-functional properties, such as emulsifying property. PRACTICAL APPLICATION: Albumins are known for their interesting nutritional values because they are rich in essential amino acids. This fraction is not currently marketed as a protein isolate for human consumption, but can be considered as a potential new vegetable protein ingredient. This document demonstrated that heat treatment or dynamic high-pressure technology can control the foaming properties of this protein for possible use in expanded foods.

Comparison Study between Batch and Continuous Processes to Obtain Chitosan-Based High Porous Biomaterial for Biological Applications

Foaming process can be monitored under batch or continuous flows conditions. In the batch process, foaming is time-dependent and the foaming efficiency is controlled by the operator. On the other hand, in the continuous process, the foaming efficiency is only monitored by gas and liquid flow rates. The aim of this work is to compare the two technologies to perform porous scaffold biomaterial based on chitosan (a biocompatible polysaccharide) as well as calcium (Ca2+) and silica (SiO2) (two osteogenesis compounds). Diverse recipes using chitosan (CS) solution (2% (w/v)) in acetic acid (1% (v/v in distilled water)) mixed with whey protein isolate (WPI) (2% (w/v)) as natural surfactant were studied. They were supplemented or not by hydroxyapatite powder (HAp) and tetraethyl orthosilicate (TEOS). A jacketed narrow annular gap unit (NAGU) was used to perform the continuous foaming process. For all experimentations, the mixture flow rate was maintained at 30 mL min-1. The influence of operating conditions such as gas and liquid flow rates was studied to obtain foams and final scaffold material with different densities and porosities. Some other recipes followed foaming under batch conditions. Generally, the recipes were placed in a vessel under mixing allowing the gas phase to come from the roof of the vessel. In this case, it becomes very difficult to control the density and the size distribution of bubbles in the final product. In both cases, liquid foams were analysed (density, bubble size distribution) and then freeze-dried for mechanical and porosity investigations using the dynamic mechanical analysis (DMA) system and scanning electron microscopy (SEM). It has been shown that the controlled injected gas affected the continuous phase, resulting in a lighter and higher porous structure, a more homogeneous appearance, and a more uniform distribution of osteogenesis components compared to one obtained using batch operation. The obtained porous materials exhibited good properties (porosity, interconnectivity, and good HAp and silica distribution) and potential for future bone regeneration applications.