Patricia Lema

Modeling Respiration Rate of Strawberry (cv. San Andreas) for Modified Atmosphere Packaging Design

A model for strawberry (Fragaria × ananassa cv. San Andreas) respiration rate was determined as a function of O2 and CO2 concentrations and temperature. Strawberries were enclosed in containers under different gaseous compositions (0–24% O2 and 0–15% CO2) and temperatures (10, 19, 23°C). Respiration rate was determined as O2 consumption and CO2 production. Respiration rate data was fitted to Michaelis-Menten models, with temperature dependence according to Arrhenius type equation. Non–linear regression was applied to calculate model parameters. No CO2 inhibition was verified, so a simple Michaelis–Menten model was selected (R2 = 0.91).

Shear wave attenuation quantification in viscoelastic transverse isotropic soft tissue using shear wave elastography

Evaluation of rheological behavior of soft tissues provides an important diagnosis tool. Nowadays, most of the available commercial ultrasound systems assume tissues as isotropic and purely elastic. Recently in order to fully characterize the rheological behavior of tissues, methods to estimate both shear wave speed (V) and attenuation (α) were developed for isotropic media [1, 2]. In acoustic radiation force elastography, generated shear waves are not plane and a diffraction correction is needed to estimate α [1]. Here a diffraction correction is studied through numerical simulation and experimentally to measure α for an homogeneous transverse isotropic, viscoelastic (TIV) medium.

Study of the browning and gelation kinetics in a concentrated sheep milk and sucrose system

Browning and gelation kinetics of a sheep milk and sucrose model system with 70% total solids (simulating dulce de leche) and the influence of temperature and sucrose content on this process were studied. The Kubelka–Munk index and subjective heat stability tests were used to monitor nonenzymatic browning and to determine gelation time. Browning and gelation processes showed different kinetics where gelation was shown to occur much faster than browning. Both independent variables (temperature and sucrose content) had a significant influence in both processes, where temperature had the higher impact.