Antioxidant activity and mechanism of action of thymol and carvacrol in two lipid systems

The autoxidation of purified triacylglycerols of lard and sunflower oil (TGL and TGSO) containing 0.02, 0.05, 0.10 and 0.20% thymol and carvacrol was studied at ambient temperature. The results obtained with the inhibited lipid systems (thymol - TGL; carvacrol - TGL; thymol - TGSO and carvacrol - TGSO) showed that thymol had the highest antioxidant effectiveness and activity during TGSO oxidation. Thymol and carvacrol participated in one side reaction during inhibited TGL oxidation, and thymol took part in two side reactions during TGSO oxidation. Carvacrol molecules did not participate in side reactions during TGSO oxidation. Thymol and carvacrol contributed to chain initiation to a higher degree during TGSO oxidation than during TGL oxidation. Thymol radicals did not participate in chain propagation during TGL and TGSO oxidation. Carvacrol radicals took part in one reaction of chain propagation in both lipid systems. In general, during autoxidation of lipids at ambient temperature, thymol is a more effective and more active antioxidant than carvacrol. Both antioxidants differ in the mechanism of their inhibiting action which depends on the character of the lipid medium. Thymol is a better antioxidant in TGSO than in TGL, whereas the activity of carvacrol in the two lipid systems does not differ significantly.     

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.     

Alginate- and gellan-based edible films for probiotic coatings on fresh-cut fruits

ABSTRACT:  Alginate- (2% w/v) or gellan-based (0.5%) edible films, containing glycerol (0.6% to 2.0%), N-acetylcysteine (1%), and/or ascorbic acid (1%) and citric acid (1%), were formulated and used to coat fresh-cut apple and papaya cylinders. Water vapor permeability (WVP) was significantly higher ( P < 0.05) in alginate films (0.30 to 0.31 × 10⁻⁹g m/Pa s m²) than in the gellan ones (0.26 to 0.27 × 10⁻⁹g m/Pa s m²). Addition of 0.025% (w/v) sunflower oil decreased WVP of gellan films (0.20 to 0.22 × 10⁻⁹ g m/Pa s m²). Water solubility of gellan and alginate films at 25 °C (0.47 to 0.59 and 0.74 to 0.79, respectively) and their swelling ratios (2.3 to 2.6 and 1.6 to 2.0, respectively) indicate their potential for coating high moisture fresh-cut fruits. Fresh-cut apple and papaya cylinders were successfully coated with 2% (w/v) alginate or gellan film-forming solutions containing viable bifidobacteria. WVP in alginate (6.31 and 5.52 × 10⁻⁹g m/Pa s m²) or gellan (3.65 and 4.89 × 10⁻⁹ g m/Pa s m²) probiotic coatings of papaya and apple, respectively, were higher than in the corresponding cast films. The gellan coatings and films exhibited better water vapor properties in comparison with the alginate coatings. Values > 10⁶ CFU/g B. lactis Bb -12 were maintained for 10 d during refrigerated storage of fresh-cut fruits, demonstrating the feasibility of alginate- and gellan-based edible coatings to carry and support viable probiotics on fresh-cut fruit.     

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.     

APPLICATION OF CORRELATION BETWEEN BIOT AND DINCER NUMBERS FOR DETERMINING MOISTURE TRANSFER PARAMETERS DURING THE AIR DRYING OF COROBA SLICES

The moisture mass transfer parameters characterizing the air drying of coroba slices were determined using the correlation between Biot and Dincet numbers. The air drying was carried out at temperatures of 71, 82 and 93C and velocities of 0.82, 1.00 and 1.18 m/s. Experimental moisture content data for coroba slices were collected. The drying coefficient and lag factor were calculated from the experimental data and were incorporated into the correlation. The moisture diffusion coefficient, Biot number and mass transfer coefficient ranged between 1.147  ×  10 ^{− 12} –3.740  ×  10 ^{− 12}  m²/s, 0.097–0.114 and 0.903  ×  10 ^{− 4} –1.729  ×  10 ^{− 4}  m/s, respectively. The predicted dimensionless moisture content profiles showed adequate agreement with the experimental observations, with the mean relative error between 0.98 and 4.61%.

PRACTICAL APPLICATION

As drying is an energy-intensive operation, it has become the prime concern of the researchers to optimize process conditions that lead to energy savings. Moisture transfer parameters are important transport properties needed for accurate modeling in food drying applications. Therefore, accurate determination of these parameters for the drying operation is essential. There is a large amount of studies available in the literature to determine and calculate these parameters for the products subjected to drying. But limited studies have been carried out to determine these parameters using the drying process parameters in terms of lag factor and drying coefficient as first introduced by Dincer and Dost.     

PARTIAL PURIFICATION AND CHARACTERIZATION OF α-GALACTOSIDASE FROM ASPERGILLUS ORYZAE

A crude extract of α-galactosidase obtained by fermenting Aspergillus oryzae on wheat bran was purified 35 fold by ethanol precipitation, gel filtration and ion-exchange chromatography. The final preparation was free of protease activity but contained invertase activity. The molecular weight of the enzyme was estimated as 64,000 daltons. The pH and temperature optima were 4.0 and 60°C, respectively. The enzyme was stable over the pH range 3–7.5 and at temperatures up to 55°C (pH 4.0). The K_m values for p-nitrophenyl α-Dgalactopyranoside (PNPG) and raffinose were 4.0 × 10⁻⁴M and 1 × 10⁻²M, respectively. Divalent cations were not required for activity. More than 80% of the oligosaccharides in soy milk were hydrolyzed after 3 h at 50°C using 0.113 PNPG units/mL milk.     

Effect of winemaking practices on color indexes and selected bioactive phenolics of Aglianico wine

ABSTRACT:  Phenolic compounds are responsible for the sensory properties of wine as well as the properties beneficial to human health. The objective of this study was to establish the effect of the use of SO₂ and pectolitic enzymes in the prefermentative phase, maceration time, and oak aging on color, anthocyanins, tannins, (+)-catechin, (–)-epicatechin, rutin, trans -resveratrol, and quercetin content of Aglianico wine. Color indexes and phenolics were analyzed by HPLC and spectrophotometric methods. The addition of SO₂ and pectolitic enzymes before fermentation caused an increase in color intensity, color stability, total phenolics, anthocyanins, (+)-catechin, (–)-epicatechin rutin, trans -resveratrol, and quercetin content in Aglianico wine. Longer maceration times gave wines richer in total phenolics and with better chromatic characteristics. Storage in oak caused a decrease in anthocyanins, (+)-catechin, (–)-epicatechin, trans -resveratrol, and quercetin content but an increase in total phenolic content, and a stabilizing effect on color also occurred.     

Effect of the phenol antioxidant type on the kinetics and mechanism of inhibited lipid oxidation in the presence of fatty alcohols

A kinetic analysis of inhibited lipid autoxidation in the presence of a phenol antioxidant and a hydroxy compound is proposed. It is based on studies of the dependence of the W^ROH/W_inh ratio (between the inhibited oxidation rates in presence and absence of a hydroxy compound) on the hydroxy compound concentration. This analysis permits establishing the mechanism of action of the hydroxy compound in the presence of different types of phenol antioxidants during inhibited lipid oxidation. The kinetic analysis has been applied to the oxidation at 80°C of triacylglycerols of sunflower oil (TGSO) inhibited by 0.1 mM hydroquinone, butylated hydroxytoluene (BHT) or α-tocopherol in the presence of different concentrations of 1-tetradecanol (1-TD) and 1-octadecanol (1-OD). A linear character of this dependence is established during hydroquinone-inhibited oxidation of triacylglycerols of sunflower oil in presence of 1-TD. In the case of α-tocopherol this dependence is linear for both 1-TD and 1-OD. The equilibrium constant of interaction between the phenol antioxidant and the fatty alcohols is determined by the angle coefficient of the linear dependence. The hydroquinone-inhibited autoxidation of TGSO in the presence of 1-OD has shown a non-linear character of the dependence under consideration. A kinetic model describing simultaneous participation of 1-OD in reaction with both the phenol antioxidant and the lipid hydroperoxides is deduced. Studying the kinetics of BHT-inhibited autoxidation of TGSO in the presence of 1-OD, it has been shown that due to steric reasons there is no interaction between 1-OD and BHT, 1-OD participating in the process only by accelerating the decomposition of the lipid hydroperoxides.     

ANALYSIS OF VARIABLES AND MODELING OF GEVUINA AVELLANA OIL EXTRACTION WITH ETHANOL NEAR AZEOTROPE CONDITIONS

Oil extraction from Gevuina avellana Mol. (Chilean hazelnut) with ethanol, near the conditions of its azeotrope with water, was carried out in this work. The effects of solubility, liquid-to-solid ratio and moisture content of ethanol were studied using 92% ethanol, azeotropic (96%) and absolute ethanol (99.9%) as solvents. Water content had a high effect on oil solubility, which reached 140 g/L in 99.9% ethanol, whereas it was 40 g/L with azeotropic ethanol. Oil accounted for 93% of total extractable compounds with absolute ethanol.
Kinetics studies of the extraction process were performed at 50C, giving as a result apparent diffusivity values near 10 ^{− 11}  m²/s, being the highest values obtained for ethanol 92% (7.5–16  ×  10 ^{− 11} ). It was also found that the higher the liquid-to-solid ratio, the higher the diffusivity. Simulation of four-stage countercurrent extraction with azeotropic ethanol yielded 23.5% oil extraction, whereas simulation of four-stage cross-flow extraction yielded 40.7%. Ethanol can be an alternative to batch cold pressing or hexane solvent extraction, for G. savellana seeds or meal processing .

PRACTICAL APPLICATIONS

The results presented in this paper are applicable for obtaining oil from oilseeds by extraction with ethanol. It includes relevant results for the optimization of extraction conditions and particularly those regarding liquid-to-solid ratio and percentage of water. Considering the more specific focus of this research, the results are applicable to obtaining Gevuina avellana oil by using an ethanol-based process, which will allow to avoid one of the cold-pressing process drawbacks: the high oil content of the meal, which is a factor limiting its lifetime.     

Microbiological quality of ice creams commercialized in some cities in the state of Rio de Janeiro, Brazil

The microbiological quality of 60 ice cream samples of three commercial brands (A, B and C) of various flavours, commercialized in some towns in the State of Rio de Janeiro, Brazil, was evaluated. Total bacteria count (TCB), coliforms at 35°C (CT), coliforms at 44°C (CF) and presence of Staphylococcus aureus were performed on all samples. TCB ranged from 2.0 × 10 ² to 6.9 × 10 ⁵ cfu/mL, CT from < 3–≥ 2400 MPN/mL, CF from < 3–1100 MPN/mL and S. aureus from < 10–1.4 × 10 ⁶ cfu/mL. The level of bacterial contamination found in this study reflects the unhygienic conditions prevalent in manufacturing and storage of ice creams. Actions are thus necessary by the Brazilian regulatory agencies to require the ice cream processing plants to adopt quality guarantee systems, such as good manufacturing practices and hazard analysis and critical control points system.     

A mathematical model to describe the change in moisture distribution in maize starch during hydrothermal treatment

Instantaneous Controlled Pressure Drop, ' Détente Instantanée Contrôlée ' (DIC) was performed on standard maize starch at residual moisture content (∼12%). Changes in moisture distribution were observed during the treatment and modelled through a phenomenological model based on gravimetric data. The model proposes an exponential variation in the moisture content with processing time at various pressures. The predicted data were found to be in good agreement with experimental data. The values of water activity coefficient ( γ ) obtained from the model decrease, when processing pressure increases; 5.86, 3.71 and 3.36 (dry basis)⁻¹ for 1, 2 and 3 bar, respectively. The mass transfer coefficient decreases, when the pressure increases. Its value ranged from 5.89 × 10⁻⁵ m s⁻¹ for 1 bar down to 0.92 × 10⁻⁵ m s⁻¹ for 2 bar and 0.77 × 10⁻⁵ m s⁻¹ for 3 bar. This coefficient is not only controlled by a simple resistance to the mass transfer, but also by gelatinisation phenomenon that progresses when temperature increases.     

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.     

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.     

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.     

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.     

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.     

The increase of CO2 permeability of paper packaging with increasing hydration

CO₂ transport through hydrated paper was studied using gas chromatography to measure CO₂ permeability (P) and diffusivity (D). With increasing water content from 0 to 0.8 g water/g paper, P and D increased from 3.47 to 9.03 × 10⁻⁶ m³ m⁻² s⁻¹ bar⁻¹ and from 1.35 to 3.51 × 10⁻⁵ m² s⁻¹, respectively. This resulted from structural changes in the cellulose network as reported in the literature; water sorption isotherms were used to explain these changes using BET theory.     

Some chemical and microbiological properties of ghee produced in Eastern Anatolia

Some properties of 30 ghee samples produced in Eastern Anatolia in Turkey were evaluated. Lipolytic bacteria and yeast–mould counts ranged from undetectable to 9.9  ×  10⁵ and 6.9  ×  10⁵ cfu/g, respectively. Most of the samples showed higher free fatty acids (FFA) and peroxide values (PV) than the limits mentioned in International Dairy Federation standards. Storage at 5°C for 30 days was not sufficient to stop the lipolytic and yeast–mould growth and lipid oxidation of the samples. Ghee samples with considerably higher trans -C18 : 1 and trans -C18 : 2 fatty acids contents were considered to be adulterated with hydrogenated oils. It is recommended that specific attention should be given to technology transfer and the education of traditional dairy product manufacturers.     

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.     

Inverse Method to Estimate Kinetic Degradation Parameters of Grape Anthocyanins in Wheat Flour Under Simultaneously Changing Temperature and Moisture

ABSTRACT:  Thermal and moisture effects on grape anthocyanin degradation were investigated using solid media to simulate processing at temperatures above 100 °C. Grape pomace (anthocyanin source) mixed with wheat pastry flour (1: 3, w/w dry basis) was used in both isothermal and nonisothermal experiments by heating the same mixture at 43% (db) initial moisture in steel cells in an oil bath at 80, 105, and 145 °C. To determine the effect of moisture on anthocyanin degradation, the grape pomace–wheat flour mixture was heated isothermally at 80 °C at constant moisture contents of 10%, 20%, and 43% (db). Anthocyanin degradation followed a pseudo first-order reaction with moisture. Anthocyanins degraded more rapidly with increasing temperature and moisture. The effects of temperature and moisture on the rate constant were modeled according to the Arrhenius and an exponential relationship, respectively. The nonisothermal reaction rate constant and activation energy (mean ± standard error) were k _{80 °C, 43% (db) moisture} = 2.81 × 10⁻⁴± 1.1 × 10⁻⁶ s⁻¹ and Δ E  = 75273 ± 197 J/g mol, respectively. The moisture parameter for the exponential model was 4.28 (dry basis moisture content)⁻¹. One possible application of this study is as a tool to predict the loss of anthocyanins in nutraceutical products containing grape pomace. For example, if the process temperature history and moisture history in an extruded snack fortified with grape pomace is known, the percentage anthocyanin loss can be predicted.