THE LAMINAR FLOW TUBULAR REACTOR WITH HOMOGENEOUS AND HETEROGENEOUS REACTIONS I. Integral Equations for Diverse Reaction Rate Regimes

Design equations for non-isothermal Laminar Flow Tubular Reactors (LFTRs) with homogeneous and heterogeneous - at the reactor wall - reactions with arbitrary kinetic equations have been satisfactorily treated transforming the original P.D.E. problem into a system of integral equations. The kernels of the integral operators are related to an eigenvalue problem which does not depend on the kinetic equations; this avoids repetitive computational effort in the treating of different reaction kinetics.

To render a more efficient numerical treatment and according to the governing reaction rate regime, modified expressions of the general solution were obtained was follows: (i) a solution with kernels depending only on the diffusion and convective times was obtained for a low reaction regime; (ii) another solution with kernels including the reaction lime, besides the diffusion and convective ones, was necessary for a fast reaction regime and (iii) the local quasi-steady-state approximation was obtained as limiting case of solution (ii) for a instantaneous reaction regime.     

Effect of Surface Freezing on Ascorbic Acid Retention in Water Blanched Potato Strips

The average retention of ascorbic acid in potato strips (10 × 10 × 80 mm) blanched in water at 50°C and 65°C over various blanching times, with and without surface freezing pre-treatment was determined. The strips were frozen in Freon Freezant-12 for 15 sec, with the freezing front penetrating 0.4–0.5 mm. Average retention of ascorbic acid in the surface-frozen potato strips was significantly lower than that in fresh strips and lower at 65°C than at 50°C. At an equal average retention of ascorbic acid, at 50°C the fresh strips required a blanching time four times higher than that for the surface-frozen strips; at 65°C it was twice as high.     

PHYSICAL–CHEMICAL AND SENSORY QUALITY EVALUATION OF GARLIC CULTIVARS

ABSTRACT

Physical–chemical quality of 14 garlic cultivars grown in Spain was analyzed, and the cultivars were classified into three types: purple, white and Chinese, in order to show the possible differences among them. The most useful instrumental color parameter to discriminate among the different types of garlic was lightness (L*). The high pH value of the purple‐type cultivar Moraluz, and the high content of d ‐glucose, d ‐fructose and total sugars of the Chinese‐type cultivars were quite remarkable. The consumer judges preferred the color and pungency of the purple‐type cultivar Morasol, while Chino Sprint stood out for its intense garlic odor. Finally, correlations between the physicochemical and the sensory parameters were studied. The red color intensity was correlated with lightness (L*) and with hue (h*); pH was correlated with chroma (C*) and moisture percentage was correlated with sucrose content.

PRACTICAL APPLICATIONS

One of the main objectives of this work was to advise growers on the selection of garlic seed. The data obtained in this work was sent to a regional research and advising agronomic center (Technical Agronomic Institute, provincial council of Albacete), where advice was given to local growers concerning the selection of the most adequate seeds, in terms of physical– chemical properties and consumer preference, plus agronomic performance (data not included in this article). The conclusions reached in this study will make an important contribution to the agronomic characterization of the garlic cultivars grown in Spain.

     

Optimizing Processing Conditions for Chemical Peeling of Potatoes using Response Surface Methodology

Using Response Surface Methodology the effects of NaOH concentration (4–20%), process temperature (55–95°C) and time (1–7 min) was determined on the yield, peeling quality, unpeeled skin and total usage of NaOH. Also evaluated were titratable NaOH in the potato tissue, NaOH penetration and “heat ring” depths during one stage chemical peeling of potatoes (Huincul variety). The best peeling quality, maximum yield and minimum total usage of NaOH was obtained for the following ranges: concentration, 11–13%, time 5–5.70 min and temperature, 90–95°C. The maximum temperature for which the “heat ring” and NaOH penetration depths were equal was 72°C where, at 20% NaOH and 7 min, peeling quality was very good and “heat ring” was absent.     

Use of Fluorogenic Assays for the Enumeration of Escherichia coli from Selected Seafoods

Escherichia coli was enumerated and immediately confirmed by incorporating 4-methylumbelliferone glucuronide (MUG) into Lactose Broth (LB), Violet Red Bile Agar (VRB) and M-Endo Broth (M-Endo) in selected seafoods. E. coli in the seafood samples ranged from 1.0 × 10¹– 1.0 × 10³ Most Probable Number (MPN)/g, 1.0 × 10¹– 3.5 × 10² cfu/g and 0.9 × 10¹– 2.8 × 10² cfu/g in LB-MUG, VRB-MUG, and M-Endo-MUG, respectively. Although not statistically significant (α= 0.05), LB-MUG resulted in higher counts in fresh finfish, frozen fish and breaded seafoods. Specificity for E. coli in LB-MUG, VRB-MUG and M-Endo MUG was 96.5%, 92.0%, and 90.0%, respectively. All three fluorogenic assays enabled a rapid and sensitive enumeration of E. coli from seafood products.     

High passage numbers induce resistance to apoptosis in C2C12 muscle cells

Cell lines with high passage numbers exhibit alterations in cell morphology and functions. In the present work, C2C12 skeletal muscle cells with either low (<20) or high (>60) passage numbers (identified as lC2C12 or h-C2C12, respectively) were used to investigate the apoptotic response to H2 O2 as a function of culture age h-C2C12. We found that older cultures (h-C2C12 group) were depleted of mitochondrial DNA (mtDNA). When we analyzed the behavior of Bad, Bax, caspase-3 and mitochondrial transmembrane potential, we observed that cells in the h-C2C12 group were resistant to H2 O2 induction of apoptosis. We propose serially cultured C2C12 cells as a refractory model to H2 O2 -induced apoptosis. In addition, the data obtained in this work suggest that mtDNA is required for apoptotic cell death in skeletal muscle C2C12 cells.     

OSMOTIC DEHYDRATION OF KIWIFRUIT (ACTINIDIA CHINENSIS): FLUXES AND MASS TRANSFER KINETICS

Pulsed‐Vacuum‐Osmotic‐Dehydration of kiwifruit (Actinidia chinensis) was studied using two kinds of osmotic solution: sucrose (65 Brix) and concentrated grape juice (63 Brix), three temperatures (25, 35 and 45C) and four vacuum pulse times (0, 5, 10 and 15 min). Experimental results enabled the mass transfer kinetics for water and solutes to be studied (compositional changes of the liquid fraction and changes in the liquid fraction/solid matrix ratio). The impregnation of samples, because of the vacuum pulse, was higher when concentrated grape juice was used as the osmotic solution, probably due to its lower viscosity. The effective diffusivity (D_e) was obtained for each experimental condition and the results show higher diffusivities for vacuum‐pulsed treatments, although differences between treatments with different vacuum‐pulse time could not be observed. D_e values were slightly greater for treatments with concentrated grape juice. The activation energies (E_o) were obtained by fitting the data to the Arrhenius equation.