Phenol Reduction Research Articles

Solid peroxides in Fenton-like reactions at near neutral pHs: Superior performance of MgO2 on the accelerated reduction of ferric species

Fenton-like reactions at near neutral pHs are limited by the slow reduction of ferric species. Enhancing generation of ▪ from solid peroxides is a promising strategy to accelerate the rate-limiting step. Herein, the H2O2 release and Fenton-like reactions of four solid peroxides, MgO2, CaO2, ZnO2 and urea hydrogen peroxide (UHP), were investigated. Results indicated that UHP can release H2O2 instantly and show a similar behavior as H2O2 in the Fenton-like reactions. MgO2 released H2O2 quickly in phosphate buffered solutions, which was comparable to CaO2 but faster than ZnO2. Metal peroxides induced higher initial phenol degradation rates than UHP and H2O2 when the same theoretic H2O2 dosages and Fe(III)-EDTA were used. MgO2 displayed a superior performance for phenol degradation at pH 5, resulting in more than 93% phenol reduction at 1.5 h. According to kinetic analyses, the generation rate of ▪ in the MgO2 system was 18 and 3.4 times higher than those in ZnO2 and CaO2 systems, respectively. The addition of MgO2 significantly promoted H2O2 based Fenton-like reactions by increasing production of ▪, and the mixture of MgO2 and H2O2 had an improved utilization efficiency of active oxygen than the MgO2 system. The findings suggested the critical roles of metal peroxides in favoring Fenton-like reactions and inspired strategies to simultaneously accelerate Fenton-like reactions and improve utilization efficiency of active oxygen.

Comparative growth responses of Amaranthus [L.] species in Humus and Ferruginous Ultisols using plant growth promoting Rhizobacteria (Pseudomonas species)

The study investigated the possibility of growth-promoting rhizobacteria to enhance plant growth capacities of Amaranthus hybridus and A. viridis in ferruginous ultisols comparative to humus. The experimental setup was divided into two groups; the first comprised of 2 weeks old plants that were inoculated using the rhizobacteria – Pseudomonas putida, P. fluorescence and a combination of both in the ratio of 1:1, in both humus (HMS) and ferruginous red (FRS) soils. The second consisted of seeds of the test plants bioprimed with the bacteria in filtrates of HMS and FRS respectively. Germination percentage in the Pseudomonas-exposed seeds was better when seeds were primed for 24 h than for 3 h in both plant species. Further, results showed that plants sown in the ferruginous soil were short-lived compared to those sown in humus containing soil irrespective of microbial treatments. The growth parameters of plants inoculated with the Pseudomonas species were better than the uninoculated plants and plants sown in the humus soil. Qualitative assessment of phytochemicals showed the presence of saponins, phenolic, tannins, terpenoids, alkaloids, and flavonoids in both species notwithstanding inoculation. The presence of glycosides in plants inoculated with P. pseudomonas was reported, but not in the control plants. Significant reduction in total phenols upon inoculation of plants with P. putida was also reported. Following the failure of FRS-exposed plants to subsist, in-vitro growth studies were conducted to compare seed growth response. Results suggest that seeds sown in FRS-filtrates performed better than those in HMS-filtrates. Pseudomonas species improves the growth, development and stress tolerance of Amaranthus species in humus soil.

Stability of bioactive compounds and in vitro gastrointestinal digestion of red beetroot jam: Effect of processing and storage

The stability of total phenolics, flavonoids and betalains, as well as antioxidant capacity of red beetroot during jam processing, storage and in vitro gastrointestinal digestion were measured using spectrophotometry. Results suggested that jam processing led to a significant reduction of total phenolics (13.8%), betalains (56.3%) and antioxidant capacity (13.2–28.2%), but a significant increase of total flavonoids (99.3%). After storage at 4 °C for 90 days, the losses of total phenolics, flavonoids, betalains and antioxidant capacity were 33.9, 10.6, 7.9 and 9.7–35.7%, respectively. In addition, jam processing improved the bioaccessibility of total phenolics, flavonoids, betalains and antioxidant capacity using in vitro simulated gastrointestinal digestion analysis. The results of this study suggested that the main bioactive compounds of red beetroot including phenolics, flavonoids and betalains, could be partially preserved during jam processing and storage, with higher levels of bioaccessibility. Therefore, the red beetroot was a promising material for the development of functional foods.

Phenolic compounds seasonal occurrence and risk assessment in surface and treated waters in Minas Gerais-Brazil.

This study provided a monitoring of phenolic compounds occurrence in a river and in its treated water by a conventional water treatment plant (WTP) throughout a year-period, in Minas Gerais - Brazil. Furthermore, the environmental risk (hazard quotient - HQ), the human health risk (margin of exposure - MOE), and the cancer risk were calculated for the compounds. The results indicated that sixteen out of the seventeen investigated phenolic compounds were detected at some point during the sampling campaign. The most frequent compounds in the raw surface water were 2,3,4-trichlorophenol (234TCP), 2,4-dimethylphenol (24DMP), and 4-nitrophenol (4NP), whereas in treated water were 4NP and bisphenol A (BPA). In addition, the highest total concentration values were corelated to the months in which there was less precipitation, demonstrating that the presence of this micropollutants may be subject to seasonality. From the treated water results, it was not possible to state the efficiency of the conventional WTP in eliminating the phenols, since in some samples the phenolic compounds were totally removed and in others their increase or formation occurred. Regarding to the risk assessments, most of the evaluated compounds were considered highly toxic to some trophic level and posed a significant human health risk. Additionally, the risk reduction of phenolics using conventional WTP was low. The sixteen phenols contamination in surface and drinking waters appears to be subject to seasonality. Besides that, an alarming risk for environment and human health was identified.

Reprint of "Proton-coupled electron transfer from an interfacial phenol monolayer"

Abstract A tert-butyl protected phenol is covalently link to a mixed self-assembled monolayer on a gold or platinum electrode. The phenol reduction potential shows the expected pH-dependence of a one-electron, one-proton couple with a decrease in formal reduction potential of 59 ± 5 mV per pH. A titration of the phenol is observed with a pKa of 13.2 and the reduction potential for the phenolate is 0.11 V . NHE. The kinetic behavior of the proton-coupled oxidation deviates substantially from the commonly used models for a step-wise reaction that assume the proton transfer reactions are in equilibrium throughout the reaction. A novel model for step-wise proton-coupled reactions is presented that fully accounts for the pH dependent kinetics and allows the formal rate constants and the transfer coefficients to be determined.

Green silver nano-particles: synthesis using rice leaf extract, characterization, efficacy, and non-target effects.

Green synthesis of silver nano-particles (AgNPs) from silver nitrate was carried out using purple-colored rice leaves' extracts containing higher phenols, anthocyanins, and flavonoids. The efficacy of synthesized AgNPs was tested against rice diseases and investigation was carried out to check negative effect of AgNPs on soil microbes. Substantial reduction of total anthocyanins, total phenols, and total flavonoids was observed in reaction mixture during AgNP formation indicating the role of secondary metabolites on AgNP formation and stabilization. Scanning electron microscopy coupled with energy-dispersive spectroscopic images and FTIR spectral analysis of AgNPs confirmed the presence of elemental silver encapped by biomolecules. The optimized reaction parameters for synthesis of AgNPs from silver nitrate were (a) 48 h of incubation, (b) 9:1 (v/v) 1 mM AgNO3:plant extract, and (c) room temperature at 20-30 °C. Zeta potential and hydrodynamic particle sizes of synthesized AgNPs were ranged between - 16.61 to - 29.45 mV and 36-107 nm, respectively, at different time of incubation. AgNPs could control effectively Rhizoctonia solani and Xanthomonas oryzae pv. Oryzae and Helminthosporium oryzae. AgNPs at higher concentration could cause negative effect on microbial biomass carbon and soil enzymes for distant future. But the negative effects of AgNP solution (10% of 1 mM AgNPs) were comparable to commercial fungicide, carbendazim. The synthesized AgNPs with desirable characters were effective against a number of disease-causing pathogens in rice, and it can be recommended as broad-spectrum pesticide.

Anti-inflammatory and anti-hypersensitive effects of the chalcone isocordoin and its semisynthetic derivatives in mice.

Isocordoin (1), a chalcone isolated from different plants, has been found to present a range of interesting biological properties. This study aimed to evaluate the anti-hypersensitive and anti-inflammatory effects of isocordoin (1) and several natural and semisynthetic derivatives (2-10). Initial evaluation of (1), dihydroisocordoin (2) and six semisynthetic derivatives (3-8) in the inhibition of abdominal writhes induced by acetic acid model showed that only isocordoin dimethylether (5) caused more than 70% of inhibition. Further evaluation of 5 for its anti-oedematogenic activity and anti-hypersensitivity effect induced by carrageenan, lipopolysaccharide (LPS), bradykinin (BK), prostaglandin E2 (PGE2), and epinephrine showed that isocordoin dimethylether (5) presented a discrete inhibition of carrageenan- and LPS-induced hypersensitivity, and of carrageenan-induced paw oedema, and that it was able to significantly reduce both the oedema and hypersensitivity induced by BK. Furthermore, when tested in the PGE2 model, 5 interfered only with the paw-oedema, without showing any effect against the paw-hypersensitivity. Evaluation of the natural isocordoin (1), together with the semisynthetic derivatives isocordoin dimethylether (5), isocordoin methylether (9), and dihydroisocordoin methylether (10) in the BK-induced oedema and hypersensitivity showed that the monoalkylated derivatives 10 and 9 had the strongest antinociceptive activity. The results of this investigation indicate that both monoalkylation of the C-4' phenolic hydroxyl group and reduction of the double bond in the α,β-unsaturated system of the chalcone skeleton favor activity.

English

Injera or Biddena commonly made from tef (Eragrostis tef (Zucc) Trotter) grain and a combination with other grains is a staple food of Ethiopian and neighboring countries. Millet and millet-based food products are rich in polyphenols and antioxidant activities. This study aimed to evaluate millet varieties for their injera making quality and polyphenol content and antioxidant activity. Five millet varieties and one tef variety called Quncho were collected, investigated and compared. A significant (p 0.05) reduction in total phenols, total flavonoids contents and DPPH free radical scavenging capacity. Hence, it is recommended that Tesema and Kola-1 varieties could be used for functional food development and injera making quality, respectively. Key words: Millet varieties, tef, injera, baking, polyphenols, antioxidant effects.

Degradation kinetics of bioactive compounds and antioxidant activity in strawberry juice concentrate stored at high and low temperatures

In this study, changes in ascorbic acid (AA), phenolics, anthocyanins (ACNs) and antioxidant activity (AOA) were monitored during storage at − 25, 4, 10 and 20 °C to observe the stability of bioactive compound in strawberry juice concentrates (SJCs). Half-life periods (t1/2) for ACN and AA degradations were 7.9 and 50 days at 20 °C, respectively. On the contrary, much higher t1/2 values were found for the reduction in AOA and phenolics, i.e. 251 and 430 days at 20 °C, respectively. AOA and phenolics were more stable during storage than AA and ACNs. p-Coumaric acid was the major phenolic identified in SJC. p-coumaric acid (33.8%), catechin (23.1%), vanilic acid (18.6%) and epicatechin (16.1%), which constituted 91.6% of phenolics in SJC, followed by chlorogenic acid (4.9%) and caffeic acid (3.2%). Chlorogenic acid was the least stable phenolic in SJC stored at 20 °C. Strong correlations were found between AOA and ACNs (r = 0.99), phenolics (r = 0.94) and AA (r = 0.92) in SJC stored at 20 °C. Significant ACN and AA degradations occurred at storage temperature as low as 4 °C. Therefore, storage at − 25 ℃ was suggested for SJC to maximize the stabilities of especially ACNs and AA in SJC.

A Comparative Study on Trichoderma harzianum and a Combination of Candida/Bacillus as Tools for the Bioremediation of Table Olive Processing Water.

A comparative study was performed on Trichoderma harzianum and a combination of Candida boidinii/Bacillus pumilus to reduce the polluting effect of TOPW (Table Olive Processing Water) from the Spanish style. A 2k fractional design was used to study the effect of pH (6–11 for the fungus and 6–9 for Candida/Bacillus), temperature (10–35 °C) and duration (7–14 days for Candida/Bacillus and 14–21 days for T. harzianum), and the effect on phenol reduction, COD and color was evaluated. The experiments were also performed on diluted TOPW (dilution ratio 1:1). Generally, Trichoderma removed higher amounts of phenols and reduced COD more than the combination Candida/Bacillus, thus confirming the higher efficiency of filamentous fungi reported in the literature. The dilution of TOPW had an effect only on COD reduction; however, the effect was mild, at least for T. harzianum (4%), while yield increase was 9% for Bacillus/Candida. pH acted in a different way on phenol removal and COD reduction; an increase of pH caused a reduction of efficiency for COD, while the effect was positive for phenols.

Fertilizing Potentiality of Fungal-Treated Olive Mill Solid Waste to Improve Some Growth and Physiological Parameters of Vicia faba L.

THE MAIN objective of the present work is to biodegrade the phenols content of olive mill solid waste by a locally isolated fungus under optimized culture conditions and study the effect of the crude olive mill solid waste (OMSW), fermented olive mill solid waste (FOMSW), as well as the residue of water extracted olive mill solid waste (ROMSW) on some growth and physiological biomarkers of Vicia faba. Aspergillus tamarii was the most efficient fungus of ten isolated fungi, where it completely (100%) degraded the phenolic contents of OMSW under the optimized culture conditions. Data showed that applying FOMSW and ROMSW resulted in a significant alleviation of OMSW adverse effects on plant shoots and roots, chlorophylls content, chlorophyll stability index, quantum yield of PSII (Fv/Fm), carbohydrates and protein content as well as the macro-elements K, P, Mg and Ca content. This improvement was increased with increasing concentrations of ROMSW, while it increased up to 4% of FOMSW. Even as the crude OMSW negatively affects the growth and physiological attributes of the tested plant, all treatments stimulated them. It seems that detoxification of OMSW either by A. tamarii or water resulted in a marked reduction of phenolics and rising in pH that might improve the soil characteristics and allows a secure and efficient dumping of OMSW.

Detoxification impact of Trichosporon cutaneum in saline condition for efficient reduction of phenol co-contaminated with cadmium.

Treatment strategies applied for co-contaminated environments may not work due to a mixture of organic and inorganic contaminants. Here, we study the efficiency of simultaneous phenol and cadmium removal by Trichosporon cutaneum in saline condition. Initially, phenol degradation and cadmium removal were analyzed separately. The results showed the high potential of T. cutaneum for phenol degradation and almost all the phenol (1250mg/L) was degraded in the presence of 5% NaCl. Cadmium removal by T. cutaneum indicated a direct relation to NaCl concentration. Increasing salt concentration from 0 to 5% caused an increase in cadmium adsorption from 57.3 to 80.2%. In the simultaneous remediation of phenol and cadmium, T. cutaneum showed a delay in the growth curve and phenol degradation, probably because of toxicity effect of cadmium, but at the end of a week, almost the same amount of phenol was removed (> 99% in 1250mg/L phenol). T. cutaneum showed good efficiency in cadmium removal in simultaneous remediation and removed 90, 89, and 75% of cadmium in the existence of 5% NaCl in 750, 1000, and 1250mg/L initial concentration of phenol, respectively. Our findings support the high activity of T. cutaneum in the bioremediation of polluted saline areas that phenol coexists with cadmium.

Optimization of process parameters and catalytic pyrolysis of Cascabela thevetia seeds over low-cost catalysts towards renewable fuel production

The present study deals with the optimization of process parameters and thermocatalytic pyrolysis of Cascabela thevetia (CT) seeds in a semi-batch cylindrical-shaped reactor. Response surface methodology (RSM) was employed for the optimization of process variables, while commercial catalysts CaO and Al2O3 were used for catalytic pyrolysis. From results, it was concluded that 525 °C temperature, 75 °C min−1 heating rate, and 75 mL min−1 flow of nitrogen yielded maximum pyrolytic liquid (45.26 wt%) while with the attendance of catalysts at 20 wt% increased the yield of pyrolytic liquid (49.12 wt% and 46.87 wt% for CaO and Al2O3 respectively). Optimization outcomes displayed that linear and quadratic terms of utilized factors were more noteworthy while interaction effects between the factors were not significant. Further, characterization of pyrolytic oil established that utilization of catalysts expressively enhanced its properties by reducing viscosity and boosted the calorific value. FTIR examination of pyrolytic oil showed that the attendance of phenols, ethers, alcohols, ketones, alkanes, acids, etc., while 1H NMR results supported the FTIR results. GC-MS analysis showed a substantial reduction of phenols and oxygen-rich products and boost the development of alcohol and aldehydes in pyrolytic oil with the introduction of catalysts. These parameters indicate improved properties of pyrolytic oil, which intensified its bioenergy capabilities.

Optimization of multiple parameters of coking wastewater (CWW): catalytic thermolysis (CT) at high pressure reactor (HPR)

AbstractPresent study deals with the treatment of coking waste water (CWW) for the reduction of pollutants COD, phenol and cyanide using catalytic thermolysis (CT). For screening of catalyst and optimization of pH the CT was performed at 100 °C, pH = 3–11 using catalyst mass loading Cw = 3 g/L. In this study Cu (NO3)2gave best performance. Further, CT was carried out using Cu (NO3)2catalyst in high pressure reactor (HPR). The investigated parameters range were initial pH (pHi) = 3–11, Cw = 1–5 g/L, temperature (T) = 100–160 °C and treatment time (tR) = 6 h. The maximum percentage reduction for COD, phenol and cyanide were 83.33, 80.57 and 97.61%, respectively at pH = 9, Cw = 4 g/L, T = 140 °C and tR = 6 h. The CT did not give complete reduction of pollutant; therefore it was further treated using adsorption process as second stage treatment. The initial value of COD = 610 mg/L, phenol = 70.58 mg/L and cyanide = 0.45 mg/L were further reduced to 98.85, 100.00 and 55.55%, respectively, when adsorption process was performed at pH = 9, adsorbents dose Aw = 4 g/L, tR = 2 h. The response surface methodology (RSM) was performed through central composite design (CCD) for the designing of experiments and optimization of both the process. The kinetics studies of CT at HPR showed first order with respect to COD and phenol, and 0.24–0.608 order with respect to CW.

Ultrasonically driven green synthesis of palladium nanoparticles by Coleus amboinicus for catalytic reduction and Suzuki-Miyaura reaction

A novel ultrasonically driven bio-reduction method was adopted to reduce the palladium chloride into palladium nanoparticles (PdNPs@CA) using coleus amboinicus extract as a green synthetic protocol. XRD confirms the formation of phase pure cubic Pd nanoparticles with the crystallite size range of 40−50 nm. The UV–vis spectrum reveals the formation of Pd nanoparticles by the disappeared peak at 480 nm of PdCl2 solution. The size distribution and surface morphology of prepared Pd nanoparticles showed spherical shaped nanoparticles with less agglomeration. The catalytic reduction behaviour of the Pd suspension is studied by 4-nitro phenol reduction process in 8 min further confirms its high catalytic performance. Synthesized PdNPs@CA were explored in ultrasound promoted Suzuki-Miyaura coupling reaction to determine the catalytic behaviour with ultrasonic frequency of 40 kHz and power of 150 W (Power sonic 410 bath sonicator) and its recycling ability is determined. It was found that aryl halides reacted with aryl boronic acids to obtain biaryl compound with excellent reaction yields in the presence of PdNPs@CA only in 30 min using PEG-400 as a green solvent. PdNPs@CA can be recovered efficiently and reused for 7 cycles without loss of its catalytic property.

Boron-containing magnetic nanoparticles from Co, Ni, and Fe chloride salts and their catalytic performances on 4-nitrophenol reduction

In this study, magnetic metal nanoparticles (MNP) were prepared by using Fe, Co and Ni ions and NaBH4 as reducing agents in oil-in-water microemulsion system. The prepared MNP were used as catalyst in 4-Nitro phenol (4-NP) reduction to 4-Aminophenol (4-AP). It was found that magnetic Co MNP performed superior catalytic performances than Fe and Ni MNP for 4-NP reduction. The catalytic reduction experiments revealed that as the concentration of reducing agent, NaBH4 that was used in the preparation of Co MNP was increased, the complete conversion time for 4-NP to 4-AP was decreased as the sizes of Co MNP were obatined as 75 ± 16, 60 ± 9, and 37 ± 6 nm when using 0.1, 0.2 and 0.4 M NaBH, respectively. Therefore, Co MNP prepared by using 0.4 M NaBH4 was used in the detailed investigation of various parameters such as the effect Co nanoparticles, reaction temperatures and time. The activation parameters of Co nanoparticle prepared by using 0.4 M NaBH4 as reducing agent was calculated as Ea = 32.1 ± 3.1 kJ mol−1, ΔH = 28.8 ± 2.2 kJ mol−1 and ΔS = −162.5 ± 9.4 J mol−1 K−1 that is the best catalytic performance amongst the other Co MNPs. The shelf life (storage) studies of Co nanoparticles showed that smaller Co MNP obtained by using 0.4 M NaBH4 reduce catalytic performance faster than the others, e.g, in the order of Co MNP(0.4 M NaBH4) > Co MNP(0.2 M NaBH4) > Co MNP(0.1 M NaBH4) in 20 day storage at ambient temperature. The activity% of Co MNP was decreased to 58 ± 3% after five consecutives use while maintaining 100% conversion at every use corroborating the promising industry application of this magnetic Co MNP.

Morphological and biochemical mechanisms of resistance against powdery mildew (Golovinomyces cichoraceaarun) of sunflower (Helianthus annuus L.)

Eighteen hybrids and two checks of sunflower were evaluated for their morphological and biochemical traitsimparting tolerance/resistance to powdery mildew during rabi, 2015-16. The results revealed that sunflower hybrids viz., LSFH-2026, LSFH-216, LSFH-3008 and LSFH-1225 exhibited moderately resistant to moderately susceptible reaction to powdery mildew. Moderately resistant hybrids exhibited least frequency and size of stomata and higher trichome density. The biochemical traits revealed that these hybrids had higher amounts of total phenols, total sugars and chlorophyll in healthy leaves. The rate of reduction of total phenols, total sugars and chlorophyll content was minimum in these three hybrids as compared to susceptible checks, after infection of powdery mildewpathogen

Evaluation of phenolics and acrylamide and their bioavailability in high hydrostatic pressure treated and fried table olives

Acrylamide was not detected after high hydrostatic pressure (HHP) of four different table olive varieties (Azeitera, Carrasqueña, Conserva de Elvas, and Morisca). Hydroxytyrosol, tyrosol, oleuropein, procyanidin B1, catechin, vanillic acid, caffeic acid, syringic acid, epicatechin, p-coumaric acid, and verbascoside were the most important phenols found in fresh olives and after HHP treatment. The content of these phenolics decreased from the fresh sample to the oral sample; however, they increased during the in vitro digestion process reaching values that were similar to the fresh samples after the final digestion phase. The highest content of phenolics was found in Carrasqueña variety subjected to intestinal digestion. With HHP, the table olives could be pasteurized without loss of phenolic compound; also the formation of acrylamide was prevented. The frying process of the filled olives induced the formation of acrylamide range from 100 to 250 µg/kg. However, Carrasqueña, the variety with the highest content of phenolic compounds presented the lowest content in acrylamide. Practical applications High hydrostatic pressure is a nonthermal technology which was applied to pasteurize table olives and to extend their shelf life, preserving the amount of phenolic compounds and preventing acrylamide formation. The frying treatments after HHP contributed to phenols reduction and acrylamide formation. However, the olives with the highest content of natural phenols showed the lower formation of acrylamide.

Ranking and multicriteria decision making in optimization of raspberry convective drying processes

AbstractSerbia is one of the leading producers and exporters of raspberry in the world, and considering the short shelf life of raspberry, the processing, storage, and transport are some of the main issues to be addressed.A comparative experiment was conducted in order to find the suitable process parameters for convective drying that may be considered as the alternatives to freeze‐drying, which is a widely used preservation method for raspberry even though it is a costly and energy‐consuming method. Twelve convective drying regimens were applied with a combination of three influencing factors: air temperature (60°C, 70°C, and 80°C), air rate (0.5 and 1.5 m·s−1), and stage of raspberry (fresh and frozen). The final product, a dried raspberry, was assessed for chemical, physical, and mechanical properties and rehydration capacity. Deep ranking analysis by power eigenvectors (DRAPE) and sum of ranking differences (SRD) were used to uncover the differences and similarities between the applied drying methods.SRD showed that convective drying of fresh raspberries proved to be more similar to freeze‐dried raspberries than convective drying of frozen ones. Fresh samples dried at 60 °C air temperature and 1.5 m·s−1 air flow proved to be the most similar to the reference freeze‐drying method. This convective regimen gives samples with the lowest color change, shrinkage, and shape deformation. With the mechanical and chemical properties of these samples being observed, statistical Duncan's test show that there is no significant difference (P < .05) in terms of hardness, shear force resistance, total phenolic, and total flavonoid preservation, compared with freeze‐dried samples. DRAPE gave similar results, but it added the variable importance in ranking as well, and total phenol reduction was defined as the most important variable. These results can help practitioners to develop cheaper and simpler drying methods that would replace the freeze‐drying but keep the same quality of the dried products.

Proton-coupled electron transfer from an interfacial phenol monolayer

A tert-butyl protected phenol is covalently link to a mixed self-assembled monolayer on a gold or platinum electrode. The phenol reduction potential shows the expected pH-dependence of a one-electron, one-proton couple with a decrease in formal reduction potential of 59 ± 5 mV per pH. A titration of the phenol is observed with a pKa of 13.2 and the reduction potential for the phenolate is 0.11 V . NHE. The kinetic behavior of the proton-coupled oxidation deviates substantially from the commonly used models for a step-wise reaction that assume the proton transfer reactions are in equilibrium throughout the reaction. A novel model for step-wise proton-coupled reactions is presented that fully accounts for the pH dependent kinetics and allows the formal rate constants and the transfer coefficients to be determined.