Lycopene degradation and isomerization kinetics during thermal processing of an olive oil/tomato emulsion

The stability of lycopene in an olive oil/tomato emulsion during thermal processing (80-140 °C) was studied. Initially, the degradation of total lycopene (all-E plus Z-forms) occurred quickly at temperatures above 100 °C. However, a nonzero plateau value, depending on the processing temperature, was attained after longer treatment times. Besides degradation, the isomerization of total-Z-lycopene as well as the individual isomerization of all-E-, 5-Z-, 9-Z-, and 13-Z-lycopene was studied in detail. After prolonged heating, the isomer conversion reached a temperature-dependent equilibrium state. The degradation of total lycopene and the isomerization could be described by a fractional conversion model. The temperature dependency of the corresponding reaction rate constants was quantified by the Arrhenius equation. The activation energy of degradation was estimated to be 28 kJ/mol, and the activation energy of overall (all-E and total-Z) isomerization was estimated to be 52 kJ/mol.     

Impact of high-pressure carbon dioxide combined with thermal treatment on degradation of red beet (Beta vulgaris L.) pigments

A combined high-pressure carbon dioxide (HP-CO 2) and thermal degradation reaction of betanin and isobetanin in aqueous solution was investigated and can be described by a first-order decay. At 45 degrees C, the degradation rate constant ( k) for each pigment component significantly increased (the half-life ( t 1/2) decreased, p < 0.05) with elevated pressure. Furthermore, HP-CO 2 treatment led to lower k values (higher t 1/2 values) than thermal treatment. However, k and t 1/2 values approached those of thermal treatment when the pressure was >30 MPa combined with temperatures exceeding 55 degrees C. Moreover, betanin was more stable than isobetanin under HP-CO 2. E a values ranged from 94.01 kJ/mol for betanin and 97.16 kJ/mol for isobetanin at atmospheric pressure to 170.83 and 142.69 kJ/mol at 50 MPa, respectively. A higher pressure and temperature as well as longer exposure time resulted in higher values of L*, b*, C*, and h degrees . HP-CO 2 induced more degradation products from betanin and isobetanin than thermal treatment with an identical temperature and exposure time.     

Thermal stability of anthocyanin extract of Hibiscus sabdariffa L. in the presence of beta-cyclodextrin

The thermal stability of anthocyanin extract isolated from the dry calyces of Hibiscus sabdariffa L. was studied over the temperature range 60-90 degrees C in aqueous solutions in the presence or absence of beta-cyclodextrin (beta-CD). The results indicated that the thermal degradation of anthocyanins followed first-order reaction kinetics. The temperature-dependent degradation was adequately modeled by the Arrhenius equation, and the activation energy for the degradation of H. sabdariffa L. anthocyanins during heating was found to be approximately 54 kJ/mol. In the presence of beta-CD, anthocyanins degraded at a decreased rate, evidently due to their complexation with beta-CD, having the same activation energy. The formation of complexes in solution was confirmed by nuclear magnetic resonance studies of beta-CD solutions in the presence of the extract. Moreover, differential scanning calorimetry revealed that the inclusion complex of H. sabdariffa L. extract with beta-CD in the solid state was more stable against oxidation as compared to the free extract, as the complex remained intact at temperatures 100-250 degrees C where the free extract was oxidized. The results obtained clearly indicated that the presence of beta-CD improved the thermal stability of nutraceutical antioxidants present in H. sabdariffa L. extract, both in solution and in solid state.     

Deactivation of ferrylmyoglobin by vanillin as affected by vanillin binding to β-lactoglobulin

Vanillin was found to be efficient as a deactivator of ferrylmyoglobin with a second-order rate constant of k(2) = 57 ± 1 L mol(-1) s(-1) for reduction to metmyoglobin with ΔH(?) = 58.3 ± 0.3 kJ mol(-1) and ΔS(?) = -14 ± 1 J mol(-1) K(-1) in aqueous pH 7.4 solution at 25 °C. Binding to β-lactoglobulin (βLG) was found to affect the reactivity of vanillin at 25 °C only slightly to k(2) = 48 ± 2 L mol(-1) s(-1) (ΔH(?) = 68.4 ± 0.4 kJ mol(-1) and ΔS(?) = 17 ± 1 J mol(-1) K(-1)) for deactivation of ferrylmyoglobin. Binding of vanillin to βLG was found to have a binding stoichiometry vanillin/βLG > 10 with K(A) = 6 × 10(2) L mol(-1) and an apparent total ΔH° of approximately -38 kJ mol(-1) and ΔS° = -55.4 ± 4 J mol(-1) K(-1) at 25 °C and ΔC(p, obs) = -1.02 kJ mol(-1) K(-1) indicative of increasing ordering in the complex, as determined by isothermal titration microcalorimetry. From tryptophan fluorescence quenching for βLG by vanillin, approximately one vanillin was found to bind to each βLG far stronger with K(A) = 5 × 10(4) L mol(-1) and a ΔH° = -10.2 kJ mol(-1) and ΔS° = 55 J mol(-1) K(-1) at 25 °C. The kinetic entropy/enthalpy compensation effect seen for vanillin reactivity by binding to βLG is concluded to relate to the weakly bound vanillin oriented through hydrogen bonds on the βLG surface with the phenolic group pointing toward the solvent, in effect making both ΔH(?) and ΔS(?) more positive. The more strongly bound vanillin capable of tryptophan quenching in the βLG calyx seems less or nonreactive.     

Processing strawberries to different products alters contents of vitamin C, total phenolics, total anthocyanins, and antioxidant capacity

Strawberries were processed to juice, nectar, wine, and puree. For investigation of the antioxidant capacity as well as the contents of ascorbic acid, total phenolics and total anthocyanins, samples were taken after different stages of production to determine the effects of processing. The content of vitamin C was measured spectrophotometrically. The total phenolic content was analyzed by using the Folin-Ciocalteu method, and the amount of total anthocyanins was determined by using the pH-differential method. Two different methods-the trolox equivalent antioxidant capacity assay and the ferric reducing antioxidant power test-were used to determine the hydrophilic antioxidant capacity. This study showed the decrease of all investigated parameters within processing strawberries to different products. The content of ascorbic acid decreased with production time and processing steps, especially during heat treatment. The investigations on total phenolics in strawberry products proved fining to be a mild method to clarify berry juices and wines without removing high amounts of total phenolics. Fermentation did not lead to heavy losses of total phenolics, probably due to polymerization and condensation of monomer phenolics such as anthocyanins. Total anthocyanins and the hydrophilic antioxidant capacity decreased while using high temperatures. Anthocyanins also decreased considerably during the processing of wines, mainly caused by fermentation and pasteurization.     

Kinetic study of the thermal stability of tea catechins in aqueous systems using a microwave reactor

Tea catechins may undergo complex reactions such as oxidation, polymerization, and epimerization during thermal processing. The thermal stability of tea catechins in an aqueous system, including degradation and epimerization reactions, was investigated using a microwave reactor. Reactions were controlled at high temperatures ranging from 100 to 165 degrees C with various durations up to 120 min. Three sources of tea catechins containing different levels of (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG), and their epimers were studied. Kinetic models for the degradation/epimerization of tea catechins were developed and validated by the reactions at 145 degrees C. It was shown that the epimerization and degradation of tea catechins followed first-order reactions and the rate constants of reaction kinetics followed the Arrhenius equation. Values of the activation energy (E(a)) for the epimerization of EGCG from epi- to nonepi-structures, the epimerization of GCG from nonepi- to epi-structures, and the total degradation of EGCG and its epimer GCG were 117.6, 84.2, and 42.8 kJ/mol, respectively. For ECG and CG, the E(a) values were 119.3, 96.2, and 41.6 kJ/mol, respectively. The mathematical models may provide a useful prediction for the loss of tea catechins during any thermal processing.     

Kinetics of thermal modifications in a grape seed extract

The thermal modification kinetics of a commercial grape seed extract (GSE) was investigated. A GSE was exposed to 60, 90, and 120 °C for 5, 10, 15, 30, 45, and 60 min. The antioxidant activity (AA) and the absorbance at 420 nm (A(420)) were measured. (+)-Catechin, (-)-epicatechin, procyanidins B1 and B2, and gallic acid were identified and measured. After the thermal treatments, the AA did not show a significant difference (p > 0.05) and both procyanidins and gallic acid increased as well as A(420). (+)-Catechin and (-)-epicatechin decreased. To obtain the activation energy (E(a)) of the changes, a modified Weibull and a combined zero- and first-order model were compared, both followed by the Arrhenius equation. The Weibull model was more accurate. The E(a) values for browning and (+)-catechin, (-)-epicatechin, gallic acid, and procyanidins B1 and B2 were 170, 286, 42, 102, 249, and 95 kJ/mol, respectively. The results were valid at a confident level of 95%.     

Thermal degradation of commercial grade sodium copper chlorophyllin

Sodium copper chlorophyllin (SCC), a water-soluble commercial derivative of chlorophyll, has gained importance as a food colorant and dietary supplement with apparent chemopreventive activities. The thermal stability of SCC was studied to assess the potential application of this chlorophyll derivative for use in thermally processed foods and supplements. Thermal degradation of an aqueous 500 ppm SCC solution was monitored between 25 and 100 degrees C by a loss of absorbance at 627 nm. Decomposition was also followed by reversed phase C18 HPLC with photodiode array detection to monitor the loss of Cu(II)Chlorin e4, the major component of commercial grade SCC. The rate of thermal degradation of SCC was found to follow first-order reaction kinetics. HPLC analysis confirmed the ultraviolet and visible absorbance data and also demonstrated loss of the major SCC component, Cu(II)Chlorin e4, at a rate faster than that of overall SCC. The activation energy was estimated using the Arrhenius equation and found to be 13.3 +/- 0.8 and 16.0 +/- 2.1 kcal/mol for the thermal degradation of SCC and Cu(II)Chlorin e4, respectively. The observed temperature sensitivity of SCC was determined to be similar to that of natural chlorophyll and raises the possibility of color deterioration when used in food products where mild to severe thermal treatment is applied. Furthermore, the implication of rapid loss of Cu(II)Chlorin e4, a reported bioactive component of SCC, upon heating may result in alteration of potential dietary benefits such as antimutagenic and antioxidant activity.     

Extraction of anthocyanins and other phenolics from black currants with sulfured water

Health benefits of fruits, vegetables, and red wine are attributed to anthocyanins and other phytochemicals. In this research, the extraction of phenolics from black currants was optimized using different SO(2) concentrations (28, 300, 700, 1100, and 1372 ppm), temperatures (6, 20, 40, 60, and 74 degrees C), and solvent to solid ratios (S/S) (6, 20, 40, 60, and 74 mL/g). Surface response methodology was used to optimize yields of anthocyanins and total phenolics, as well as their antiradical and antioxidant activities. The extraction of phenolics varied with the SO(2) concentration, S/S, and temperature. Maximum yields of total phenolics and anthocyanins were obtained at an SO(2) concentration of 1000-1200 ppm and 19 L of solvent/kg of milled frozen berries. The increase of extraction temperature increased the rate of extraction and, thus, times to reach equilibrium for the extraction of total phenolics and anthocyanins were reduced. However, for the extraction of anthocyanins it is recommended that temperatures of 30-35 degrees C be used, as higher temperatures will degrade these compounds. Antioxidant activity was affected by all three experimental variables evaluated; however, the main variable affecting it was S/S. The higher the S/S, the lower the antioxidant index.     

Picrocrocin kinetics in aqueous saffron spice extracts (Crocus sativus L.) upon thermal treatment

The kinetics of picrocrocin degradation in aqueous extracts of saffron upon thermal treatment from 5 to 70 °C have been studied, together with the degradation of purified picrocrocin in water at 100 °C. The best fits to experimental data were found for a second-order kinetics model. Picrocrocin showed high stability with half-life periods (t(1/2)) ranging from >3400 h at 5 °C in saffron extracts to 9 h in the experiments with purified picrocrocin at 100 °C. In saffron extracts, the evolution of the rate constant (k) with temperature showed maximum values at 35 °C, and filtration of the extracts contributed to picrocrocin stability. In the case of purified picrocrocin, the generation of safranal in the first 5 h (yield up to 7.4%) was confirmed. Spectrometric parameters used in saffron quality control (E(1cm)(1%) 257 nm and ΔΕ(pic)) were not appropriate for documenting the evolution of picrocrocin.     

Antioxidant activity and diffusion of catechin and epicatechin from antioxidant active films made of poly(L-lactic acid)

Active membranes and food packaging containing antioxidants like catechin and epicatechin, combined with the use of materials made of biopolymers obtained from renewable sources, could create a novel alternative to reduce oxidation in food, pharmaceutical, and cosmetic products. Poly(94% L-lactic acid) films containing 1.28% catechin and 1.50% epicatechin were extruded in a pilot plant-scale extrusion machine. The diffusion kinetics of catechin and epicatechin into 95% ethanol at 20, 30, 40, and 50 °C and 50% ethanol at 40 °C displayed Fickian release behavior and diffusion coefficients between 0.5 and 50 × 10(-11) cm(2)/s. According to the Arrhenius equation, the energy of activation for the diffusion of catechin and epicatechin in the films was 110.43 and 98.92 kJ/mol, respectively. The antioxidant activity of the films was measured in methanol extracts containing 46.42 μg/mL of catechin and 57.52 μg/mL of epicatechin as 32.90 and 36.68% of scavenging the 2,2-diphenyl-1-picrylhydrazyl radical, respectively.     

Inhibition of protein and lipid oxidation in liposomes by berry phenolics

The antioxidant activity of berry phenolics (at concentrations of 1.4, 4.2, and 8.4 mug of purified extracts/mL of liposome sample) such as anthocyanins, ellagitannins, and proanthocyanidins from raspberry (Rubus idaeus), bilberry (Vaccinium myrtillus), lingonberry (Vaccinium vitis-idaea), and black currant (Ribes nigrum) was investigated in a lactalbumin-liposome system. The extent of protein oxidation was measured by determining the loss of tryptophan fluorescence and formation of protein carbonyl compounds and that of lipid oxidation by conjugated diene hydroperoxides and hexanal analyses. The antioxidant protection toward lipid oxidation was best provided by lingonberry and bilberry phenolics followed by black currant and raspberry phenolics. Bilberry and raspberry phenolics exhibited the best overall antioxidant activity toward protein oxidation. Proanthocyanidins, especially the dimeric and trimeric forms, in lingonberries were among the most active phenolic constituents toward both lipid and protein oxidation. In bilberries and black currants, anthocyanins contributed the most to the antioxidant effect by inhibiting the formation of both hexanal and protein carbonyls. In raspberries, ellagitannins were responsible for the antioxidant activity. While the antioxidant effect of berry proanthocyanidins and anthocyanins was dose-dependent, ellagitannins appeared to be equally active at all concentrations. In conclusion, berries are rich in monomeric and polymeric phenolic compounds providing protection toward both lipid and protein oxidation.     

Stability and antioxidant activity of black currant anthocyanins in solution and encapsulated in glucan gel

The effects of ferric and ferrous ions, pH, and temperature on the stability and antioxidant activity of black currant anthocyanins (BCA) were studied, and the recovery of BCA from glucan gel [mixed linked (1-->3,1-->4)-beta-D-glucan] after using different encapsulating procedures was determined. The degradation of individual anthocyanins follows first-order kinetics and shows Arrhenius temperature dependence. The activation energies of individual anthocyanins, evaluated over the temperature range 60-100 degrees C, decrease with an increase in pH. While the antioxidant activity of BCA, measured by the ferric reducing antioxidant power assay, decreased with the degradation of anthocyanins, the completely degraded products still exhibited approximately 30% of the initial antioxidant activity. Ferric ions have a detrimental effect on the stability of BCA, especially for delphinidins. Freeze drying of encapsulated BCA gives approximately 20% higher recovery of individual anthocyanins than infrared drying.     

Isomerization and degradation kinetics of hop (Humulus lupulus) acids in a model wort-boiling system

The rate of isomerization of alpha acids to iso-alpha acids (the compounds contributing bitter taste to beer) was determined across a range of temperatures (90-130 degrees C) to characterize the rate at which iso-alpha acids are formed during kettle boiling. Multiple 12 mL stainless steel vessels were utilized to heat samples (alpha acids in a pH 5.2 buffered aqueous solution) at given temperatures, for varying lengths of time. Concentrations of alpha acids and iso-alpha acids were quantified by high-pressure liquid chromatography (HPLC). The isomerization reaction was found to be first order, with reaction rate varying as a function of temperature. Rate constants were experimentally determined to be k1 = (7.9 x 10(11)) e(-11858/T) for the isomerization reaction of alpha acids to iso-alpha acids, and k2 = (4.1 x 10(12)) e(-12994/T) for the subsequent loss of iso-alpha acids to uncharacterized degradation products. Activation energy was experimentally determined to be 98.6 kJ per mole for isomerization, and 108.0 kJ per mole for degradation. Losses of iso-alpha acids to degradation products were pronounced for cases in which boiling was continued beyond two half-lives of alpha-acid concentration.     

Aerobic versus Anaerobic Microbial Degradation of Etofenprox in a California rice field soil

The microbial degradation of etofenprox, an ether pyrethroid, was characterized under anaerobic (flooded) and aerobic (nonflooded) California rice field soil conditions by determination of its half-life (t1/2) and dissipation rate constant (k) and identification and quantification of degradation products at both 22 and 40 °C using LC-MS/MS. The overall anaerobic t1/2 at 22 °C ranged from 49.1 to 100 days (k=-0.0141 to -0.0069 days(-1)) compared to 27.0 days (k=-0.0257 days(-1)) at 40 °C, whereas under aerobic conditions the overall t1/2 was 27.5 days (k=-0.0252 days(-1)) at 22 °C compared to 10.1-26.5 days (k=-0.0686 to -0.0262 days(-1)) at 40 °C. The biphasic dissipation profiles were also fit to a first-order model to determine the t1/2 and k for both the fast and slow kinetic regions of the dissipation curves. Hydroxylation at the 4'-position of the phenoxy phenyl ring was the major metabolic process under anaerobic conditions for both 22 °C (maximum% yield of applied etofenprox mass=1.3±0.7%) and 40 °C (max % yield=1.2±0.8%). Oxidation of the ether moiety to the ester was the major metabolite under aerobic conditions at 22 °C (max% yield=0.5±0.1%), but at 40 °C increased amounts of the hydroxylated form were produced (max% yield=0.7±0.2%, compared to 0.3±0.1% for the ester). The hydrolytic product of the ester, 3-phenoxybenzoic acid (3-PBA), was not detected in any samples. Sterilized control soils showed little etofenprox degradation over the 56-day incubation period. Thus, the microbial population in a flooded soil was able to transform and contribute to the overall dissipation of etofenprox. The simulated summer temperature extreme (40 °C) increased the overall degradation.     

Effect of processing on the phytochemical profiles and antioxidant activity of corn for production of masa, tortillas, and tortilla chips

The phytochemical profiles (total phenolics, anthocyanins, ferulic acid, carotenoids) and antioxidant activities of five types of corn (white, yellow, high carotenoid, blue, and red) processed into masa, tortillas, and tortilla chips were studied. The nixtamalization process significantly (p < 0.05) reduced total phenolics and antioxidant activities when compared to raw grains. Nixtamalized grains exhibited higher concentration of free phenolics and soluble conjugated ferulic acid and had lower concentrations of bound phenolics and ferulic acid than unprocessed grains. Among processed products, there was little difference in the phytochemical contents and antioxidant activities. Among types of corn, the highest concentrations of total phenolics, ferulic acid, and antioxidant activity were observed in the high-carotenoid genotype followed by the regular yellow counterpart. The white corn contained the lowest amount of total phenolics and antioxidant activity. The pigmented blue corn had the highest anthocyanin concentration followed by the red counterpart. These findings suggest that lime-cooking significantly reduced the phytochemical content of nixtamalized products but released phenolics and ferulic acid.     

Antioxidant capacity in cranberry is influenced by cultivar and storage temperature

Ten cranberry (Vaccinium macrocarpon Aiton) cultivars were evaluated for oxygen radical absorbance capacity (ORAC), anthocyanins, and total phenolics contents after three months of storage at 0, 5, 10, 15, and 20 degrees C. The antioxidant capacity of cranberry was affected by cultivars and storage temperatures. Among the 10 cranberry cultivars used in this study, Early Black, Crowley, and Franklin had higher antioxidant capacities than the other cultivars. ORAC values, anthocyanins, and total phenolics contents increased during storage. The highest increases in antioxidant activity, anthocyanin, and phenolics contents occurred at 15 degrees C storage. Fruit stored at 20 degrees C had lower ORAC values than those stored at 15 degrees C. A positive relationship existed between ORAC values and anthocyanin or phenolic content in all 10 cranberry cultivars at different storage temperatures.     

Phenolic composition and antioxidant properties of Polish blue-berried honeysuckle genotypes by HPLC-DAD-MS, HPLC postcolumn derivatization with ABTS or FC, and TLC with DPPH visualization

In this study, different Polish cultivars of blue-berried honeysuckles (Lonicera caerulea L.), wild and bog bilberry, were analyzed for bioactive compounds. The chemical properties verified included composition of anthocyanins and other polyphenols, antioxidant activity, and profiles of antioxidants by HPLC postcolumn derivatization or TLC. The antioxidant activities of different blue-berried honeysuckle cultivars were similar to that of wild-growing bilberries (ranging from 170 to 417 μmol TE/g dm in ABTS and from 93 to 166 μmol TE/g dm in DPPH and Folin-Ciocalteu tests). The major anthocyanin in the blue-berried honeysuckle was cyanidin-3-glucoside, which constituted 84-92% of the total anthocyanins. The TLC and HPLC postcolumn antioxidant profiles indicated that anthocyanins are the major antioxidants in all berries studied. Wild berries and the cultivars of the blue-berried honeysuckles are also a similar source of such minerals as K, Mg, and Ca.     

Kinetic model for studying the effect of quercetin on cholesterol oxidation during heating

Inhibition of the heat-induced cholesterol oxidation at 150 degrees C by incorporation of quercetin was kinetically studied. Results showed that without quercetin, the cholesterol oxidation products (COPs) concentration increased with increasing heating time. A low amount (0.002%, w/w) of quercetin was effective in inhibiting the formation of COPs during the initial heating period (< or =30 min) at 150 degrees C. However, after prolonged heating (30-120 min), a low antioxidant activity was observed because of the degradation of quercetin. When using nonlinear regression models for kinetic study of cholesterol oxidation in the absence of quercetin, the epoxidation showed the highest rate constant (h(-1) = 683.1), followed by free radical chain reaction (h(-1) = 453.5), reduction (h(-1) = 290.3), dehydration (h(-1) = 155.5), triol dehydrogenation (h(-1) = 5.35), dehydrogenation (h(-1) = 0.68), thermal degradation (h(-1) = 0.66), and triol formation (h(-1) = 0.38). However, in the presence of quercetin, the reaction rate constants (h(-1)) for epoxidation (551.4), free radical chain reaction (111.7), and thermal degradation (0.28) were reduced greatly. The kinetic model developed in this study can be used to predict the inhibition of COPs by quercetin during the heating of cholesterol.     

Inactivation of apple pectin methylesterase induced by dense phase carbon dioxide

The inactivation of apple pectin methylesterase (PME) with dense phase carbon dioxide (DPCD) combined with temperatures (35-55 degrees C) is investigated. DPCD increases the susceptibility of apple PME to the temperatures and the pressures have a noticeable effect on apple PME activity. A labile and stable fraction of apple PME is present and the inactivation kinetics of apple PME by DPCD is adequately described by a two-fraction model. The kinetic rate constants k L and k S of labile and stable fractions are 0.890 and 0.039 min (-1), and the decimal reduction times D L and D S are 2.59 and 58.70 min at 30 MPa and 55 degrees C. Z T representing temperature increase needed for a 90% reduction of the D value and the activation energy E a of the labile fraction at 30 MPa is 22.32 degrees C and 86.88 kJ /mol, its Z P representing pressure increase needed for a 90% reduction of the D value and the activation volume V a at 55 degrees C is 21.75 MPa and -288.38 cm (3)/mol. The residual activity of apple PME after DPCD exhibits no reduction or reactivation for 4 weeks at 4 degrees C.