A dual-port THz Time Domain Spectroscopy System optimized for recovery of a sample’s Jones matrix

We describe the design, build and characterization of a novel two-output port configuration for a THz-Time Domain Spectroscopy (TDS) system. By introducing a tilted THz ultra-broadband polarizer, we split the THz beam in two orthogonal polarization detector branches. The probe laser is similarly split (with an optical polarizer) replicating the detection chain to obtain two independent orthogonal polarization detection units. We describe the system’s performance highlighting some of the advantages of this system in one of its two modes of operation: optimized polarimetry for Jones matrix measurements. A bi-refringent sapphire standard was measured to confirm its capabilities and assess the performance of the system showing good agreement with existing literature data

DOE-NSF-NIH Workshop on Opportunities in THz Science, February 12-14, 2004

This is the report of the Workshop on Opportunities in THz Science, held on February 12-14, 2004 in Arlington, VA. This workshop brought together researchers who use or produce THz radiation for physics, chemistry, biology, medicine, and materials science to discuss new research opportunities and common resource needs. The charge from the sponsors of the workshop was to focus on basic science questions within these disciplines that have and can be answered using THz radiation

Thermal versus high pressure processing of carrots: A comparative pilot-scale study on equivalent basis

This report describes the first study comparing different high pressure (HP) and thermal treatments at intensities ranging from mild pasteurization to sterilization conditions. To allow a fair comparison, the processing conditions were selected based on the principles of equivalence. Moreover, pilot- and industrial-scale equipment were opted for, supporting conditions close to industrial application. The overall impact on carrot quality was characterized by analyzing a wide range of quality attributes, including specific (micro)nutrients (carotenoids and sugars), process-induced contaminants (furfural and 5-hydroxymethylfurfural), enzyme activities (pectin methylesterase and peroxidase) and other relevant quality aspects (texture, dry matter content and color). This study demonstrated that the potential benefit of HP over thermal processing of carrots is largely dependent on the processing intensity applied. Thermal sterilization affected carrot quality the most, while mild and severe thermal pasteurization, mild and severe HP pasteurization and HP sterilization resulted in a comparable overall quality. Industrial relevance: The extensive nature of this investigation and the corresponding results can be considered of key importance for further implementation of HP technology in the food industry, since a correct and complete assessment of process-induced changes is of major importance in the context of legislative aspects of novel processing technologies

Thermal versus high pressure processing of carrots: A comparative pilot-scale study on equivalent basis

This report describes the first study comparing different high pressure (HP) and thermal treatments at intensities ranging from mild pasteurization to sterilization conditions. To allow a fair comparison, the processing conditions were selected based on the principles of equivalence. Moreover, pilot- and industrial-scale equipment were opted for, supporting conditions close to industrial application. The overall impact on carrot quality was characterized by analyzing a wide range of quality attributes, including specific (micro)nutrients (carotenoids and sugars), process-induced contaminants (furfural and 5-hydroxymethylfurfural), enzyme activities (pectin methylesterase and peroxidase) and other relevant quality aspects (texture, dry matter content and color). This study demonstrated that the potential benefit of HP over thermal processing of carrots is largely dependent on the processing intensity applied. Thermal sterilization affected carrot quality the most, while mild and severe thermal pasteurization, mild and severe HP pasteurization and HP sterilization resulted in a comparable overall quality. Industrial relevance: The extensive nature of this investigation and the corresponding results can be considered of key importance for further implementation of HP technology in the food industry, since a correct and complete assessment of process-induced changes is of major importance in the context of legislative aspects of novel processing technologies

Production of Antioxidant Egg White Hydrolysates in a Continuous Stirred Tank Enzyme Reactor Coupled with Membrane Separation Unit

The objective of this research was to design an efficient continuously operated membrane reactor with a separation unit for egg white protein (EWP) hydrolysis and production of hydrolysates with improved antioxidant properties. For this purpose, a mechanically stirred tank reactor coupled with the polyethersulfone ultrafiltration module with a molecular weight cutoff of 10 kDa was employed. Several proteolytic enzymes have been tested in order to obtain the best quality of peptide-based formulations intended for human consumption. Among protease from Bacillus licheniformis (Alcalase), protease from Bacillus amyloliquefaciens (Neutrase), and protease from papaya latex (papain), the highest degree of hydrolysis (DH), as well as the best antioxidant properties of obtained hydrolysates, was achieved with Alcalase. The effects of operating variables such as enzyme/substrate ([E]/[S]) ratio, impeller speed, and permeate flow rate were further studied using response surface methodology (RSM) and Box-Behnken experimental design. Results obtained in RSM analysis confirmed that over the studied range [E]/[S] ratio, impeller speed and permeate flow rate had the significant effect on the DH and reactor capacity. The effects of different impeller geometries were also studied and four-bladed propeller stirrer enabled the highest DH. Antioxidant properties were analyzed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), by the 2,2'-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) radical scavenging activity, and by the linear voltammetry methods. Results show that the use of Alcalase in the membrane reactor system is of potential interest for the EWP hydrolysis and obtaining value-added egg products

Production of egg white protein hydrolysates with improved antioxidant capacity in a continuous enzymatic membrane reactor: optimization of operating parameters by statistical design

This study focuses on the influence of operating conditions on Alcalase-catalyzed egg white protein hydrolysis performed in a continuously stirred tank reactor coupled with ultrafiltration module (10 kDa). The permeate flow rate did not significantly affect the degree of hydrolysis (DH), but a significant increase in process productivity was apparent above flow rate of 1.9 cm(3) min(-1). By contrast, an increase in enzyme/substrate (E/S) ratio provided an increase in DH, but a negative correlation was observed between E/S ratio and productivity. The relationship between operating conditions and antioxidant properties of the hydrolysates, measured by three methods, was studied using Box-Behnken experimental design and response surface methodology. The statistical analysis showed that each variable (impeller speed, E/S ratio, and permeate flow rate) had a significant effect on the antioxidant capacity of all tested systems. Nevertheless, obtained response functions revealed that antioxidative activity measured by DPPH, ABTS and FRAP methods were affected differently by the same operating conditions. High impeller speeds and low permeate flow rates favor ABTS while high impeller speeds and high permeate flow rates had a positive effect on the DPPH scavenging activity. On the other hand, the best results obtained with FRAP method were achieved under moderate operating conditions. The integration of the reaction and ultrafiltration membrane separation in a continuous manner appears to be a right approach to improve and intensify the enzymatic process, enabling the production of peptides with desired antioxidant activity