Singlet Oxygen Oxidation Rates of ∝-, γ-, and δ-Tocopherols

ABSTRACT:  The reaction rate constants of 5 × 10⁻⁴ M, 10 × 10⁻⁴ M, and 20 × 10⁻⁴ M α-, γ-, and δ-tocopherols with singlet oxygen in methylene chloride containing 1 × 10⁻⁵ M chlorophyll under light at 25 °C for 60 min were studied. The oxidation of tocopherols determined by a spectrophotometric method showed that the losses of 20 × 10⁻⁴ M α-, γ-, and δ-tocopherols after 60 min under light were 21%, 16%, and 9%, respectively. The degradation of α-, γ-, and δ-tocopherols was undetectable in the absence of chlorophyll under light or in the presence of chlorophyll in dark. The losses of tocopherols under light were mainly due to singlet oxygen oxidation. The degradation rates of 20 × 10⁻⁴ M α-, γ-, and δ-tocopherols were 6.6 ×10⁻⁶ M/min, 5.0 × 10⁻⁶ M/min, and 2.9 × 10⁻⁶ M/min, respectively. The reaction rates between α-, γ-, or δ-tocopherol and singlet oxygen were 4.1 ×10⁶/M s, 3.3 × 10⁶/M s, and 1.4 × 10⁶/M s, respectively. The singlet oxygen oxidation rate of δ-tocopherol was significantly lower than α- or γ-tocopherol at α= 0.05. As the electron density in the chromanol ring of tocopherol increased, the singlet oxygen oxidation was increased.     

SIMULTANEOUS DIFFUSION of CITRIC ACID and ASCORBIC ACID IN PREPEELED POTATOES

The study of the simultaneous diffusion of chemical preservatives in vegetable tissues permits the determination of the time required to complete this process and the concentration distributions of the preservatives.
The individual or simultaneous diffusion of citric and ascorbic acids in pre-peeled potatoes was analyzed; the effect of pH decrease on the diffusive flux of ascorbic acid and the interaction between both acids was considered as the multicomponent diffusion problem.
Potato spheres of different radii were immersed in individual solutions or mixtures of citric and ascorbic acids in concentration ranging from 0.5% to 2% W/V for different immersion times and agitation conditions. the residual concentration of citric acid was determined by titrable acidity (22058 AOAC method) and that of ascorbic acid by 2–6 dichlorophenol-indophenol method.
Experimental data were fitted to the mathematical models and the effective diffusion coefficients were determined for citric (D_e= 4.3 ± 0.2 × 10⁻¹⁰ m²/s) and ascorbic acids (D_e= 5.45 ± 0.4 × 10⁻¹⁰ m²/s) diffusing individually. When mixtures of two acids were used, multicomponent analysis was adopted and interaction coefficients were evaluated (D₁₂= 6.67 ± 0.8 × 10⁻¹¹ m²/s and D₂₁= 8.33 ± 0.8 × 10⁻¹¹ m²/s); they were an order of magnitude lower than binary diffusion values.
The pH effect on the diffusive flux of ascorbic acid was decoupled from the interaction of both acids during simultaneous diffusion by studying the diffusion of the first acid in potatoes preacidified with the second acid.     

Osmotic Dehydration of Tomato in Sucrose Solutions: Fick's Law Classical Modeling

ABSTRACT:  Osmotic dehydration of tomato was modeled by the classical Fick's law including shrinkage, convective resistance at the interface and the presence of water bulk flow. Tomato slices having 8 mm thickness were osmotically dehydrated in sucrose solutions at 50, 60, and 70 °Brix and at 35, 45, and 55 °C. Other experiments were done in a 70 °Brix sucrose solution at 35 °C with tomato slices of 4, 6, and 8 mm thickness and at different motion levels (velocities 0, 0.053, and 0.107 m/s). Tomato weight, water content, and °Brix of the products were measured as a function of processing time (20, 40, 80, 160, and 320 min). Results showed that temperature, concentration, thickness, and solution movement significantly influenced water loss and sucrose gain during the osmotic dehydration of tomato. The model predicted the modifications of soluble solid content and water content as a function of time in close agreement with the experimental data. Experimental Sherwood number correlations for sucrose and water were determined as Sh _s = 1.3 Re ^0.5 Sc _s^0.15 and Sh _w = 0.11 Re ^0.5 Sc _w^0.5, respectively. The effective diffusion coefficients of water (4.97 10⁻¹¹– 2.10 10⁻¹⁰ m²/s) and sucrose (3.18 10⁻¹¹– 1.69 10⁻¹⁰ m²/s) depended only on temperature through an Arrhenius-type relationship.     

Whey Protein Film Composition Effects on Potassium Sorbate and Natamycin Diffusion

ABSTRACT: To assess the ability of whey protein films to act as antimicrobial carriers, the effect of film composition on preservative diffusion was investigated. Preservative diffusion coefficients were measured at 24°C in whey protein isolate (WPI) films with different WPI-glycerol plasticizer ratios (1:1 to 15:1), beeswax (BW) content, 0% to 40% w/w dry solids, and preservative addition of 0.3% (w/w) natamycin or 1.6% (w/w dry solids) potassium sorbate. Diffusion coefficients for potassium sorbate and natamycin were in the ranges 1.09 × 10⁻¹¹ to 13.0 × 10⁻¹¹ m²/s and 6.16 × 10⁻¹⁴ to 37.8 × 10⁻¹⁴ m²/s, respectively, and significantly decreased as the WPI-glycerol ratio increased. No significant difference in sorbate diffusion was seen with the addition of BW.     

EFFECTS OF ESCULETIN AS A LIPOXYGENASE INHIBITOR IN SOYBEAN EXTRACTS

This study was designed to determine the ability of esculetin to inhibit lipoxygenase activity in soybean. Lipoxygenase was extracted from ground soybean using 0.1 M Tris-HCl buffer (pH 8.6) and centrifuged at 3000 g for 15 min at 4C. The extract was mixed with different volumes of 0.05M esculetin solutions to provide 1.8 × 10⁻⁴M, 3.3 × 10⁻⁴M, 4.6 × 10⁻⁴M and 5.7 × 10⁻⁴M to final assay systems, respectively. Lipoxygenase activity decreased as the concentration of esculetin solution mixed in soybean extract increased. Mixing of 1.8 × 10⁻⁴M esculetin solution to soybean extract showed the least inhibition effect and was significantly different from that of 3.3 × 10⁻⁴M, 4.6 × 10⁻⁴M and 5.7 × 10⁻⁴M which inhibited LOX (lipoxygenase)'s activity of soybean extracts. In the study comparing the inhibition abilities for lipoxygenase activity among selected antioxidants, esculetin was significantly better than BHA (butylated hydroxyanisole) and α-tocopherol.     

SIMULATING DIFFUSION MODEL AND DETERMINING DIFFUSIVITY OF POTASSIUM SORBATE THROUGH PLASTICS TO DEVELOP ANTIMICROBIAL PACKAGING FILMS

A diffusion model was simulated by computer programming and diffusivities of potassium sorbate through various plastic films were determined by a lag time method. The simulation showed that partition coefficient affected the flux of total penetration but did not affect the lag time. Therefore, the lag time method is appropriate in determining diffusivity, using any value for the partition coefficient. The diffusivities of potassium sorbate were 1.83 × 10⁻⁸ cm²/s, 4.26 × 10⁻¹³ cm²/s, 4.65 × 10⁻¹³ cm²/s, and 5.47 × 10⁻¹³ cm²/s through low density polyethylene (LDPE), high density polyethylene, polypropylene, and polyethylene terephthalate, respectively at 25 C. Arrhenius equation shows very good fit between the diffusivity and the temperature by the linear regression analysis. D₀ and E_a of potassium sorbate through LDPE film resulted in 1.98 × 10⁻⁶ cm²/s, and 11.83 KJ/mole K. The concentration of potassium sorbate was insignificant and did not contribute to the statistical model. This result verifies that the diffusion of potassium sorbate in LDPE film is typical case ofFickian diffusion.     

CHANGES IN SIZE OF GAS CELLS IN DOUGH AND BREAD DURING BREADMAKING AND CALCULATION OF CRITICAL SIZE OF GAS CELLS THAT EXPAND

Microscopic observation showed that a group of small air cells entrained during the early stage of mixing is the original cause of cell structure of bread. At the beginning of fermentation, about 3 × 10⁸/m² gas cells with diameters between 3 × 10⁻⁶ and 8 × 10⁻⁴ m were entrained in the dough. The distribution curve of cell size was approximately normal on a logarithmic scale. During fermentation and proofing, a great portion of carbon dioxide was released into cells larger than about 10⁻⁴ m in diameter that was equivalent to a few percentages of total number of gas cells. After baking, gas cells smaller than 10⁻⁴ m in diameter were not observed and the total number of cells in baked bread reduced to about 10⁶/m² with diameters between 10⁻⁴ and about 5 × 10⁻³ m. The critical cell size to expand generally agreed with the calculated value using an equation, rc'= 3s/E (re': critical radius to expand, s: surface tension, E: elasticity), and cited value of s and E.     

MICROBIAL STABILIZATION OF INTERMEDIATE MOISTURE FOOD SURFACES I. CONTROL OF SURFACE PRESERVATIVE CONCENTRATION

Changing environmental conditions to which intermediate moisture foods (IMF's) are exposed during production, storage, distribution and use, are important microbial stability factors. Temperature changes result in local surface condensations leading to microbial outgrowth on the surface. An approach to improved surface stability using a high preservative surface concentration maintained by an impermeable edible food coating was developed. Permeability tests predicted that zein was an acceptable coating. Sorbic acid distribution experiments confirmed its barrier properties. Apparent diffusion coefficient was estimated between 3 and 7 × 10⁻⁹ cm²/s. These values were 150–300 times smaller than the value measured in the bulk of the IMF model food system used in this study, 10⁻⁶ cm²/s.     

Natural Antioxidants as a Component of an Egg Albumen Film in the Reduction of Lipid Oxidation in Cooked and Uncooked Poultry

ABSTRACT: Egg albumen coatings with natural antioxidants fenugreek, rosemary, and vitamin E were evaluated for their antioxidant activity in diced raw and diced cooked poultry breast meat. Coatings were applied using a vacuum tumbling and a boiling method. Coated samples and uncoated controls were evaluated for their malondialdehyde and reactive substances content as a measure of lipid oxidation via the thiobarbituric acid test. Cooked egg albumen-coated samples showed reactive compound changes of 1.56 × 10⁻⁷M for 4 d of refrigeration, compared to 1.59 × 10⁻⁶ M change in the cooked control. Raw control changed by 1.97 × 10⁻⁶M versus 1.67 × 10⁻⁶ M for raw rosemary coated samples. In raw and cooked studies EAS coating showed most effective against lipid oxidation.     

Quenching Mechanisms and Kinetics of α-Tocopherol and β-Carotene on the Photosensitizing Effect of Synthetic Food Colorant FD&C Red No. 3

ABSTRACT: Effects of FD&C Red No. 40, Red No. 3, Yellow No. 5, Yellow No. 6, Green No. 3, Blue No. 1 and Blue No. 2 on 0.03M soybean oil oxidation in acetone at 25 °C under light were studied by measuring headspace oxygen depletion. As Red No. 3 increased from 0 to 5, 20, 100 and 200 ppm, the headspace oxygen was reduced by 2 to 70, 73, 77 and 77%, respectively, for 4 h. Only Red No. 3 acted as a photosensitizer to produce singlet oxygen in the oil. The quenching rates of α-tocopherol and β-carotene for the singlet oxygen by Red No.3 were 4.1 × 10⁷ M⁻¹s⁻¹ and 7.3 × 10⁹ M⁻¹s⁻¹, respectively. When β-carotene was below 1.86 × 10⁻⁶ M, β-carotene quenched singlet oxygen, but it quenched both singlet oxygen and Red No. 3 at or above 3.72 × 10⁻⁶ M. However, α-tocopherol quenched singlet oxygen only.     

Characterization of Lactoferrin (LF) from Colostral Whey Using Anti-LF Antibody Immunoaffinity Chromatography

ABSTRACT: Lactoferrin (LF) in colostral whey was isolated by anti-LF immunoglobulin in yolk (IgY)-Sepharose 4B immunoaffinity chromatography, and parameters such as binding capacity (q_m) and dissociation constant (K_d, × 10⁻⁶ M) of this immunoaffinity gel for LF were discussed. Purification folds for colostral whey I (from colostrum collected within 6 d of postpartum) and colostral whey II (from colostrum collected within 1 d of postpartum) by anti-LF IgY-immunoaffinity chromatography were 135.80 and 103.60, respectively. The recovery for LF in the same colostral whey sample by anti-LF IgY-immunoaffinity chromatography was 82 to 99 %. q_m of anti-LF IgY-immunoaffinity gel for LF in colostral whey I and whey II were 0.372 and 0.272 mg LF/mL wet gel, respectively. K_d of anti-LF IgY-immunoaffinity gel for LF in colostral whey I was 1.594 × 10⁻⁶ M and II was 1.587 × 10⁻⁶ M.     

DRYING KINETICS OF RED PEPPER

Desorption isotherms of unblanched and blanched red peppers were experimentally obtained at 30C. The desorption data were exploited to estimate equilibrium moisture contents of the peppers at drying temperatures other than 30C by using a semi-empirical method. Red pepper samples were dried in a tunnel-type drier with an air velocity of 2 m/s at 50C, 60C, 70C, and 80C. The blanched samples dried faster than the unblanched ones. The drying behavior of unblanched and blanched samples was characterized by falling rate period, and constant and falling rate drying periods, respectively. The interphase mass and heat transfer coefficients of the blanched sample during the constant rate period were not affected by temperature and estimated to be 1.94*10⁻³ kg mol/s. m² and 57.3 W/m². K, respectively. Effective moisture diffusivity was estimated between 6.83*10⁻¹⁰−17.4*10⁻¹⁰ m²/s for the unblanched sample and 11.4*10⁻¹⁰−31.0*10⁻¹⁰ m²/s for the blanched sample within the given temperature range. Effect of temperature on the diffusivity was described by an Arrhenius-type equation with an activation energy of 28.4 kJ/mol for the unblanched pepper and 33.3 kJ/mol for the blanched pepper.     

Pacific Cod Muscle 5'-Nucleotidase

SUMMARY: A 5'-nucleotidase, widely distributed in teleost fish muscles, was purified about 20-fold from Pacific cod (Gadus macrocephalus) by chromatography of a dialyzed aqueous extract of the muscle on DEAE-cellulose. The enzyme was unstable and lost 85% of its activity in 1 hr at 37°C 53% in 10 min at 42°C and 40% in 1 hr at 30°C. It was stable for 6 days at 0°C, could be dialyzed for up to 3 days at 0°C against 1 mM tris buffer pH 7.5 and quickly frozen and thawed without loss of activity. However, it was inactivated rapidly when held at −30°C. Brief exposure to pH 4.0 or 5.0 effected marked destruction. Attempts at further purification by means of chromatography on hydroxylapatite, adsorption using alumina Cγ and starch gel electrophoresis failed due to instability.
The enzyme was strongly inhibited by EDTA, pyrophosphate, KF and ZnCl₂ (1-10 mM); less markedly inhibited by GSH, 2-mercaptoethanol, carbonate and CaCl₂ (10 to 100 mM). It was strongly activated by Mn⁺⁺ and weakly activated by Mg⁺⁺. The optimum pH was 7.6, and the Km was 5 × 10⁻⁴M with UMP and 8 ⁻⁴M with IMP. It hydrolyzed, in order of effectiveness, LJMP, IMP, CMP, d-AMP, GMP, d-IMP, d-GMP, d-UMP and AMP, but not p-nitro phenylphosphate, sugar phosphates or a number of other compounds including 2',3'-nucleotides.     

Utilizing the R-Index Measure for Threshold Testing in Model Soy Isoflavone Solutions

ABSTRACT: Twenty-eight untrained panelists used the signal detection rating method to determine thresholds for daidzein and genistein. Five concentrations of genistein and daidzein were suspended in starch solutions. The starch solution represented the noise, and isoflavone suspensions represented the signal. Blindfolded panelists received 15 replicates of noise and signal. To determine group detection thresholds, the concentration at an R-index of 75% was calculated. The group thresholds for genistein and daidzein were 4.006 × 10⁻³ M and 2.921 × 10⁻³ M, respectively. These results indicate a much higher threshold value than reported in the literature and in soymilks. This strongly suggests that daidzein and genistein individually do not contribute to bitterness or astringency in soy food products.     

In vitro release of propranolol from oil/water microemuisions

Oil/water (o/w) microemulsions containing propranolol were studied. Isopropylmyristate was used as the oil, Tween 60 as a surfactant, butanol as a co-surfactant and a buffer of pH 6.5 for the continuous phase. The lipophilicity of propranolol was enhanced by formation of lipophilic ion-pairs to obtain a disperse phase that could act as a reservoir; octanoic acid was used as counter-ion. The diffusion rates of propranolol from microemulsions through a hydrophilic membrane decreased as the concentration of octanoic acid increased. The apparent permeability constant, determined at the beginning of the experiment, was 2.9 × 10⁻⁹ cm s⁻¹ for propranolol alone and diminished until 3.5 × 10⁻¹⁰ cm s⁻¹ in the presence of octanoic acid, at a concentration of 16.4 times that of propranolol.     

Microwave heat treatment of leek: drying kinetic and effective moisture diffusivity

The effect of microwave drying technique on moisture ratio, drying time and effective moisture diffusivity of white and green parts of leek ( Allium porrum ) were investigated. By increasing the sample amount (100–300 g) at constant microwave output power of 180 W, the drying time increased from 52 to 130 min and increased from 55 to 135 min for white and green parts of leek, respectively. Effective moisture diffusivity values for white and green parts of leek ranged from 0.618 × 10⁻¹⁰ to 2.128 × 10⁻¹⁰ m².s⁻¹ and 0.256 × 10⁻¹⁰ to 0.611 × 10⁻¹⁰ m² s⁻¹, respectively. Among the models proposed, Midilli et al. model gave a better fit for all drying conditions applied. The activation energy for microwave drying of white and green parts of leek was calculated using an exponential expression based on Arrhenius equation; found as 0.9530 and 1.2045 W g⁻¹, respectively. The dependence of drying rate constant on effective moisture diffusivity gave a linear relationship.     

Osmotic dehydration kinetics of carrot cubes in sodium chloride solution

Osmotic dehydration kinetics of carrot cubes in sodium chloride solution having concentrations 5%, 10% and 15% (w/v), solution temperature 35, 45 and 55 °C, sample to solution ratio (STSR) 1:4, 1:5 and 1:6 were studied up to 240 min duration. During the experimentation, effect of solution temperature and process duration was significant and that of solution concentration and STSR were non-significant on water loss. Among the different models applied (Penetration model, Magee Model, and Azuara model), Azuara model best fitted to the experimental data for water loss and solute gain during osmotic dehydration. Effective diffusivities of water and solute were calculated by using the analytical solution of Fick's unsteady state law of diffusion by iterative technique with a computer program. For the above conditions, the effective diffusivity of water was found to be in the range between 2.6323 × 10⁻⁹ and 6.2397 × 10⁻⁹ m²/s and that of solute between 3.1522 × 10⁻⁹ and 4.6400 × 10⁻⁹ m²/s.     

Mass Transfer in Strawberry Tissue During Osmotic Treatment II: Structure-function Relationships

ABSTRACT: The surface response method demonstrated macroscopic changes in strawberry tissue during osmotic treatment (OT). Changes in the structural elements of strawberry were determined by evaluating bulk phenomena such us water loss, solid gain, and shrinkage. The changes were related to microstructural changes (determined in Part I) that took place in the same range of process conditions. The extension of impregnation, with respect to dewatering, increased as cellular shrinkage and cell destruction increased. The macroscopic effective diffusivity of water ranged from 5.1 ± 1.0 × 10⁻¹⁰ to 0.7 ± 0.2 × 10⁻¹⁰ m²/s, which was 2 orders of magnitude higher than the microscopic effective diffusivity of water (in the order of magnitude of 10⁻¹² m²/s), calculated from cellular shrinkage.     

INFLUENCE of REACTION CONDITIONS ON the FORMATION of NONDIALYZABLE MELANOIDINES FROM D-FRUCTOSE and GLYCINE

The influence of the water content, molar ratio of reagents, time and temperature on the formation of nondialyzable melanoidines of the model system D-fructose-glycine has been studied.
The rate constants of the reaction for molar ratios 2.5:1, 1:1, 1:2.5 have been calculated to be (2.38 ± 0.17) x 10⁻⁵ S⁻¹, (3.94 ± 0.28) x 10⁻⁵ S⁻¹ and (5.11 ± 0.36) x 10⁻⁵ S⁻¹, respectively.
The activation energy has been determined (105.0 ± 3.6) kJ/mol and (74.6 ± 7.1) kJ/mol for molar ratios 2.5:1 and 1:2.5, respectively.     

Osmotic Dehydration Behavior of Red Paprika (Capsicum Annuum L.)

ABSTRACT: Osmotic dehydration of red paprika was studied using a combined sucrose (5 to 45 g/100 g) and sodium chloride (0 to 15 g/100g) solution. The effective diffusion coefficients for water and solute were determined using the slope method based on the Fickian diffusion model. The effects of concentration of sucrose, sodium chloride and their complex interaction on water and solute diffusion coefficients as well as on equilibrium moisture and solid contents were studied using central composite rotatable design of experiments. The graphical optimization showed that at optimum conditions (sucrose concentration and sodium chloride concentration were 21.86 g/100 g and 2.02 g/100 g, respectively), the following criteria were achieved: water diffusion coefficient (D_ew) 0.80 × 10⁻⁹ m²/s, solid diffusion coefficient (D_es 0.82 × 10⁻⁹ m²/s, equilibrium moisture content (m∞) 6.85 kg/kg, and equilibrium solid content (s∞) 2.00 kg/kg.