Jorge Welti-Chanes

Drying of Pepper Seed Particles in a Superheated Steam Fluidized Bed Operating at Reduced Pressure

A series of drying experiments was performed in a reduced-pressure superheated steam fluidized bed, employing pepper seed particles and some novel data were obtained. Experiments were carried out using different chamber pressures (40–67 kPa), temperatures (90–122°C), steam velocities (2.35–4.10 m/s), and mass flow rates (0.0049–0.0134 kg/s). In the majority of the experiments, the moisture gain observed in some other studies in the warm-up period of the process was prevented through some supplementary heat provided to the column. The drying rate was found to be increasing by operating temperature; however, it was not affected much by the superficial gas velocity and the operating pressure. Nevertheless, the reduced pressure operation increases the degree of superheating that appears as the most important parameter of the process. The experimental results showed that the equilibrium moisture content decreases by the increasing degree of superheating. On the other hand, the critical moisture content assumes higher values for the greater degrees of superheating. It was concluded that a relatively lower temperature process can be achieved through a reduced-pressure superheated steam fluidized bed.

Application of Osmotic Dehydration Processes to Produce Apple Slices Enriched with β-Carotene

The objective of this work was the impregnation of β-carotene in apple slices by osmotic dehydration (OD) at atmospheric pressure and by pulsed vacuum osmotic dehydration (PVOD). Osmotic solutions were sucrose solutions of 30, 40, and 50 °Brix containing β-carotene (0.01 g/mL). Maximum impregnation using OD treatments was 1.5, 3.5, and 4.1 mg β-carotene/g ds. When using PVOD, significantly shorter processing times were required and impregnation reached 4.7, 5.5, and 6 mg β-carotene/g ds. Values of aw obtained by OD were 0.973, 0.967, and 0.960 while by PVOD were 0.960, 0.930, and 0.880. Results showed that PVOD was a good option to impregnate apple with β-carotene.

Effect of Input Data Variability on Estimations of the Equivalent Constant Temperature Time for Microbial Inactivation by HTST and Retort Thermal Processing

UNLABELLED Consumer demand for food safety and quality improvements, combined with new regulations, requires determining the processors confidence level that processes lowering safety risks while retaining quality will meet consumer expectations and regulatory requirements. Monte Carlo calculation procedures incorporate input data variability to obtain the statistical distribution of the output of prediction models. This advantage was used to analyze the survival risk of Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) and Clostridium botulinum spores in high-temperature short-time (HTST) milk and canned mushrooms, respectively. The results showed an estimated 68.4% probability that the 15 sec HTST process would not achieve at least 5 decimal reductions in M. paratuberculosis counts. Although estimates of the raw milk load of this pathogen are not available to estimate the probability of finding it in pasteurized milk, the wide range of the estimated decimal reductions, reflecting the variability of the experimental data available, should be a concern to dairy processors. Knowledge of the C. botulinum initial load and decimal thermal time variability was used to estimate an 8.5 min thermal process time at 110 °C for canned mushrooms reducing the risk to 10⁻⁹ spores/container with a 95% confidence. This value was substantially higher than the one estimated using average values (6.0 min) with an unacceptable 68.6% probability of missing the desired processing objective. Finally, the benefit of reducing the variability in initial load and decimal thermal time was confirmed, achieving a 26.3% reduction in processing time when standard deviation values were lowered by 90%. PRACTICAL APPLICATION In spite of novel technologies, commercialized or under development, thermal processing continues to be the most reliable and cost-effective alternative to deliver safe foods. However, the severity of the process should be assessed to avoid under- and over-processing and determine opportunities for improvement. This should include a systematic approach to consider variability in the parameters for the models used by food process engineers when designing a thermal process. The Monte Carlo procedure here presented is a tool to facilitate this task for the determination of process time at a constant lethal temperature.

Drying Kinetics of Paddy in a Reduced Pressure Superheated Steam Fluidized Bed

Drying kinetics of paddy are experimentally studied in a superheated steam fluidized bed operating at reduced pressure. During the experiments, different operating pressures (40–67 kPa), operating temperatures (98–118°C), superficial steam velocities (2.9–4.0 m/s), and mass flow rates (0.0061–0.0103 kg/s) were employed. The condensation problem, typically observed in the initial part of the process, was eliminated in the majority of the experiments through some additional heat supplied into the column by electrical resistances. The experiments demonstrated that drying rates increase by increasing operating temperature. Nevertheless, the operating pressure and the superficial steam velocity showed only limited influences over the process. The degree of superheating was identified as the principal parameter controlling the phenomenon. It was also observed that higher degrees of superheating generate lower equilibrium moisture contents and a superheating steam fluidized bed operating at reduced pressure can achieve drying processes at relatively lower temperatures.

Influence of Particle Size on Vacuum–Fluidized Bed Drying

The effect of particle size on the vacuum–fluidized bed drying process was experimentally studied using pepper seed particles with two distinct diameters. In the constant drying rate period, the small particles demonstrated stronger drying rates resulting from higher mass transfer coefficient values and larger contact area for per unit particle humidity. The experimental results also showed that the falling drying rate period was controlled in the beginning by the particle diameter and later by the effective porosity of the particle. Consequently, in the beginning of the falling drying rate period the small particles presented higher drying rates, whereas toward the end of the period, the large particles, with higher effective porosity, produced stronger drying rates than the small ones. The effects of the vacuum pressure and the superficial gas velocity throughout the process were only observed in the constant drying rate period, whereas the higher operating temperatures enriched the drying rates in both periods.