High hydrostatic pressure as pretreatment and adjuvant for the enzymatic release of ferulic acid from corn cob

Process Biochemistry

https://doi.org/10.1016/j.procbio.2017.04.011

Bioprocesses based on the use of enzymes can be employed for the obtainment of ferulic acid by its solubilization from corn cob, which is a natural source of this phenolic compound. In order to overcome the limitations caused by the recalcitrance of biomass, the application of pretreatments is advisable. The utilization of high hydrostatic pressure on the enzymatic release of ferulic acid from corn cob with three feruloyl esterase extracts was studied applying pressurization at 600 MPa as a pretreatment in combination with a mild thermal treatment at 130 °C/2 h. Additionally, pressurization at 200 MPa during the enzymatic hydrolysis step was assessed to increase the ferulic acid yield. The results showed that the application of a high pressure pretreatment at 600 MPa/40 °C/15 min to thermally treated corn cob increased by 20% the ferulic acid release in comparison with the thermal treatment for Ultraflo® L, but not for the Aspergillus extracts. Pressurization at 200 MPa during the hydrolysis stage affected differently the enzymes stability and ferulic acid release depending on the extract and the pretreatments applied, showing that the effects of pressurization are complex and must be assessed in each case.

Effect of long-term frozen storage on the rheological properties of pressurized glucomannan gels

Food Hydrocolloids

http://dx.doi.org/10.1016/j.foodhyd.2016.11.021

Several weakly deacetylated glucomannan gels (pH = 9.1), at a concentration of 5 g/100 mL, were subjected to high hydrostatic pressure (HHP) at 0, 100, 200, 400 and 600 MPa. They were frozen and stored at −20 °C for two years to study the influence of long-term frozen storage on the rheological properties of pressurized samples (FP100, FP200, FP400, FP600) compared with a frozen unpressurized control (FP0) and an unfrozen unpressurized control (P0). In unpressurized gels, frozen storage reduced stress (σmax) and strain (γmax) amplitudes while forming a more solid-like network (FP0 vs P0). Gel FP0 maintained the rubber-like response from temperature (T) > 70 °C as in P0. HHP reduced loss of conformational stability and enhanced cohesiveness in FP100−FP600 vs FP0. Particularly, 400 MPa improved the degree of connectivity in the glucomannan (GM) network producing a better thermoset response at T > 70 °C (FP400).