Biomedical subjects

B E Farkas

Publications and source records attributed to B E Farkas.

5 recordsLinked to original sources

PubMed2003

Characterization of radiant emitters used in food processing.

Radiant emissions from short, medium, and long wavelength thermal radiant emitter systems typically used for food processing applications were quantified. Measurements included heat flux intensity, emitter surface temperature, and spectral wavelength distribution. Heat flux measurements were found highly dependent on the incident angle and the distance from the emitter facing. The maximum flux measured was 5.4 W/cm2. Emitter surface temperature measurements showed that short wavelength radiant systems had the highest surface temperature and greatest thermal efficiency. The emitter spectral distributions showed that radiant emitter systems had large amounts of far infrared energy emission greater than 3 microm when compared to theoretical blackbody curves. The longer wavelength energy would likely cause increased surface heating for most high moisture content food materials.

Equipment Failure Analysis↗

PubMed2002

Parametric analysis of cryogenic carbon dioxide cooling of shell eggs.

Parametric analysis of cryogenic cooling of shell eggs was performed using finite element analysis. Two cooling temperatures (-50 and -70 C), three cooling convective heat transfer coefficients (20, 50, and 100 W/ m2K), two equilibration temperatures (7 and 25 C), and two equilibration heat transfer coefficients (0 and 20 W/ m2K) were considered in the analysis. Lower temperatures and higher cooling convective heat transfer coefficients resulted in higher cooling rates and lower final egg temperatures. A chart and equation were developed to identify combinations of processing parameters to yield the desired egg temperature (7 C) at the end of adiabatic equilibration. Results show that a cooling time of 8.2 min was required to reach a final egg temperature of 7 C for a cooling temperature of -50 C and a convective heat transfer coefficient of 20 W/m2K. The cooling time decreased to 2 min when the convective heat transfer coefficient increased to 100 W/m2K, at a cooling temperature of -50 C. Processing at -70 C and 20 W/m2K, required 5.3 min to reach a final temperature of 7 C. At a higher convective heat transfer coefficient (100 W/m2K) and -70 C, a processing time of 1.3 min was sufficient to reach the target temperature of 7 C. The results may be used as a reference in process or equipment design for shell egg cooling in cryogenic CO2.

Animals↗

PubMed2000

Gas exchange into shell eggs from cryogenic cooling.

The gas composition of the air cell in a shell egg is influenced by heating from egg washing and candling and the method of cooling and storage. This study found that N2 gas (-122 C), CO2 gas (-45 C), and cold air (-15 C) could be used to rapidly cool shell eggs from 47.7 C to 7 C in 30 min or less. These results suggest that the gas composition of the air cell in shell eggs can be significantly modified using N2 cooling and CO2 cooling. Commercial field studies have shown that these modifications, which take place during cryogenic cooling, can significantly reduce microbial levels and increase shelf life of shell eggs. Storage in a modified atmosphere environment further enhanced these changes. It was found that the CO2 concentration in the air cell of a shell egg can be increased from 0.04 to 48% by CO2 cooling and storage in a CO2 environment.

Animals↗

PubMed2000

The influence of rapid air cooling and carbon dioxided cooling and subsequent storage in air and carbon dioxide on shell egg quality.

This study examined the effect of rapid cooling with air and CO2 on shell egg quality over 14 wk. The 240 fresh eggs were initially heated to 47 C for 24 h in an incubator, cooled using rapid air cooling or CO2 cooling, and then stored in air or CO2 in 250-mL jars for 14 wk. The CO2 levels were recorded of the jar atmosphere, of the egg air cell, and of the egg albumen. The Haugh units of each egg, pH, and of albumen from five eggs per group were also recorded. Haugh units are a logarithmic, empirical relationship between albumen height and egg weight (Stadelman, 1995). Haugh units for the control eggs averaged 70.8 over 10 wk of the study. The control eggs were of such poor quality that they could not be sampled after 10 wk. The air-cooled and CO2-stored eggs averaged 70.3 Haugh units over the 14-wk storage period; however, the egg quality significantly deteriorated after 10 wk. The CO2-cooled and CO2-stored eggs averaged 75.9 Haugh units over the 14 wk study, with no observable decrease in quality. Rapid air-cooling produces a lower quality egg than rapid cooling with CO2. Subsequent storage of rapidly air-cooled eggs in C02 may increase shelf life, but Haugh units were not statistically different from rapid air-cooled eggs. CO2-cooling and subsequent storage in CO2 increased Haugh units. The shelf life of shell eggs could be extended to greater than 14 wk when the eggs were CO2-cooled and CO2-stored.

Air↗

PubMed1999

Use of mutant strain for evaluating processing strategies to inactivate Vibrio vulnificus in oysters.

Vibrio vulnificus is a ubiquitous marine bacterium frequently isolated from shellfish and associated with severe and often fatal disease in humans. Various control strategies to reduce the disease risk associated with V. vulnificus contamination in shellfish have been proposed. However, evaluating the efficacy of these control strategies is complicated because of the difficulty in distinguishing V. vulnificus from the high levels of background environmental Vibrio spp. The purpose of this research was to develop a model indicator V. vulnificus strain that could be readily differentiated from background microflora and used to facilitate the evaluation of processing efficacy. A spontaneous nalidixic acid-resistant strain of V. vulnificus (Vv-NA) was prepared from a wild-type parent (Vv-WT) using selective plating techniques. Vv-NA was very similar to Vv-WT with respect to biochemical characteristics, appearance on selective plating media, detection limits using most probable number and polymerase chain reaction, and growth rate. In comparative freeze inactivation studies on pure cultures, Vv-WT and Vv-NA had similar freeze inactivation profiles at -20 degrees C (conventional freezing), at -85 degrees C (cold blast freezing), and in liquid nitrogen (cryogenic freezing). In oyster homogenates artificially inoculated with Vv-NA, the organism was inactivated 95 to 99% after freezing, irrespective of freezing temperature. Thermal inactivation comparisons of pure cultures of Vv-WT and Vv-NA using the capillary tube method revealed statistically significant differences in D values at 47 degrees C (2.2 versus 3.0 min, respectively) and 50 degrees C (0.83 versus 0.56 min, respectively), but nearly identical values at 52 degrees C (0.21 versus 0.22 min, respectively). However, these D values were notably higher than those reported by other investigators and hence provided a conservative means by which to evaluate thermal inactivation. In oyster homogenates seeded with Vv-NA, D values of 1.3+/-0.09 min and 0.41+/-0.01 min were obtained at 46 degrees C and 48 degrees C, respectively. This study demonstrated that Vv-NA is readily enumerated and could be used as a surrogate for evaluating the degree of V. vulnificus inactivation provided by freezing and thermal treatments of oyster homogenates.

Animals↗