Enzyme Pectin Methylesterase Research Articles

Inactivation kinetics of pectin methyl esterase in the microwave-assisted pasteurization of orange juice

The enzyme pectin methyl esterase (PME) kinetic inactivation study in orange juice was performed by conventional heat treatment (thermal bath) and focused microwave heating (synthesis microwave reactor). Experiments have been performed in batch, with temperatures ranging between 50 °C and 95 °C for time between 0 and 60 s for both processes. Non-isothermal processes were considered and histories of time-temperature have been acquired. The kinetic model adjusted considered two fractions of PME (thermosensitive and thermoresistant), and the kinetic parameters to microwave processes at Tref = 90 °C were z1 = 13.7 °C, z2 = 20.3 °C, D1 = 0.231 s and D2 = 130.8 s with α = 0.95. Comparative analysis of processes was performed graphically by residual enzymatic activity versus lethality. The results demonstrated the microwave-assisted thermal process was more effective than conventional one under the same conditions, indicating the possibility for some additive non-thermal effects. Innovative conditions of inactivation were achieved: i.e. 90% at 60 °C after 10 s and 99% at 80 °C after 20 s.

Effect of high pressure carbon dioxide on tomato juice: Inactivation kinetics of pectin methylesterase and polygalacturonase and determination of other quality parameters

Tomato juice, Lycopersicon esculentum cv. Canario, has been treated by high pressure carbon dioxide (HPCD) as non-thermal preservation treatment. The inactivation kinetics for pectinmethylesterase (PME) and polygalacturonase (PG) were determined at different pressures (8.5–20 MPa) and temperatures (35–55 °C). At the highest operating pressure and temperature essayed in this work, it was found that PME could be almost completely inactivated, whereas PG resulted to be more HPCD resistant at the working conditions. PME enzyme inactivation curves were properly described by a Weibull type model, while the fractional conversion model was the most appropriate for the PG with a sharp initial decrease in activity. On the contrary, high pressure processing (HPP) led to a nearly complete inactivation of PG while PME was very resistant at 600 MPa. It was also found that HPCD treatment led to a smaller particle size distribution of tomato juice.

Comparison of nano-calcium and calcium chloride spray on postharvest quality and cell wall enzymes activity in apple cv. Red Delicious

Abstract The aim of the experiment was to compare the effects of preharvest nano-calcium and calcium chloride spraying on postharvest quality and the cell wall enzyme activities of the apple fruit (Malus domestica L. cv. Red Delicious) at harvest and during storage (1, 2, 3, 4 month). Sprayings on apple trees were started from 70 d after full-bloom until one month before harvesting. They were sprayed 5 times, intervals of two weeks, with nano-calcium (0, 1.5, 2, and 2.5%), and calcium chloride (0, 1, 1.5, and 2%) solutions. After harvest, some fruit were transported to the laboratory to evaluate the parameters while other fruit were stored at 0 °C and at 90% RH for 4 months. Measurements were performed on fruit firmness, weight loss, titrable acidity (TA), total soluble solids (TSS), total phenolic content (TPC), browning, total antioxidant activity (TAA), and fiber content at 0, 1, 2, 3, and 4 months of storage period. Furthermore, assessments were made regarding enzymes in the cell wall such as polygalacturonase (PG), pectin methylesterase (PME), and β-galactosidase (β-Gal). Results showed that firmness, TA, TPC, TAA, and fiber content increased in fruit that treated with both nano-calcium and calcium chloride as compared to control fruit, however, these parameters decreased by prolonging the storage time. Meanwhile, weight loss, TSS, and internal browning increased during storage time, but, this increase in treated fruit was less than control fruit. Moreover, during storage, lower activities of PG, PME, and β-Gal enzymes were observed in fruit that sprayed with both calcium fertilizers. In addition, In short, it was observed that the quality of apple fruit treated with nano-calcium was better than those treated with calcium chloride in all parameters. So, it can be considered to use nano-calcium fertilizer instead of calcium chloride fertilizer for improving quality and storability of fruit such as apple.

Postharvest quality of plums in response to the occurrence of leaf scald disease

Plum leaf scald (PLS) is considered the main barrier to expanding plum cultivation in Brazil. The disease causes water flow to be obstructed in the xylem of infected plants. Infected host plants produce fruit of lower quality; however, no information is available about the postharvest quality attributes in plum. Fruit from the ‘Gulfblaze’ and ‘Reubennel’ plant cultivars, both with and without PLS symptoms, were collected from commercial orchards. Bacterial presence was confirmed using a polymerase chain reaction, and the physicochemical, biochemical, and physiological properties were evaluated. Brown rot incidence was also determined during the ripening period. According to a molecular analysis, symptomatic plants used in the assay carried Xylella fastidiosa (which causes PLS), but healthy plants did not. Fruit collected from infected plants had a reduced diameter and weight in the 2015/2016 growing season. There was a greater reduction in pulp firmness and higher pectin methylesterase enzyme activity in fruit harvested from infected compared with healthy plum trees. The total soluble solids content was higher in fruit from ‘Gulfblaze’ and ‘Reubennel’ diseased compared with disease-free plants. A higher incidence of brown rot was observed in plants with leaf scald symptoms. The highest phenylalanine ammonia-lyase activity was observed in fruit from ‘Gulfblaze’ diseased plants. CO2 and ethylene production was higher in the infected than healthy plants, indicating that the presence of X. fastidiosa can accelerate fruit ripening mechanisms.

Pectinolytic enzymes-solid state fermentation, assay methods and applications in fruit juice industries: a review.

A plethora of solid substrates, cultivation conditions and enzyme assay methods have been used for efficient production and estimation of polygalacturonase and pectin methylesterase enzymes. Recent developments in industrial biotechnology offer several opportunities for the utilization of low cost agro-industrial waste in Solid State Fermentation (SSF) for the pectinolytic enzyme production using fungi. Fruit waste mainly citrus fruit waste alone and along with other agro-industrial waste has been explored in SSF for enzyme production. Agro-industrial waste, due to the economic advantage of low procuring cost has been employed in SSF bioreactors for pectinolytic enzyme production. Acidic pectinases produced by fungi are utilized especially in food industries for clarification of fruit juices. This review focuses on the recent developments in SSF processes utilizing agro-industrial residues for polygalacturonase and pectin methylesterase production, their various assay methods and applications in fruit juice industries.

Bioactive compounds and antioxidant activity of buriti fruits, during the postharvest, harvested at different ripening stages

Abstract The buriti ( Mauritia flexuosa L.f.) is a highly nutritious fruit with a yellowish-orange pulp and a bittersweet taste. Its endocarp is surrounded by a spongy material made of starch and oil, while the fruit skin is hard, consisted of small reddish-brown scales. This work aimed to characterize the bioactive compounds and the antioxidant activity of buriti fruits, during the postharvest time, harvested at different ripening stages. The fruits were harvested in a transitional environment savannah/forest at private properties in the city of Boa Vista, Roraima, Brazil. Fruits were analyzed for five consecutive years (2012–2016), at three different ripening stages: immature (with up to 75% green color between the scales), mature (with up to 50% green color between the scales) and ripened (with up to 25% green color between the scales). The selected fruits were standardized on the basis of their appearance, such as color of the epidermis and phytosanitary conditions, and later sanitized. Different fruit variables were analyzed every 2 days during a 10-day postharvest period including loss of fresh mass, pH, total acidity, soluble solids, total pectins, pectin methyl esterase and polygalacturonase enzyme activity, respiratory behavior (CO 2 and ethylene), and functional activity such as phenolic compounds, carotenoids and antioxidant activity (ORAC and DPPH). High antioxidant activity, in both methods, was observed in buriti fruits at different ripening stages during the postharvest storage period, characterized by high phenolic and carotenoid compounds. Fruits harvested at mature and immature stages showed a longer postharvest shelf life. It was observed a climacteric behavior of the buriti fruits here analyzed, that showed an increase in the respiration rate and ethylene production, indicated by the peak of CO 2 and ethylene production. Similar changes were observed in the fruit pH, total acidity and soluble solids, as well as in the activity of peptic enzymes whereas a decrease was observed in the total pectin contents. The fruits showed reasonable amount of phenolic compounds, carotenoids and antioxidant activity, thus confirming the functional potential of these fruits.

Physicochemical, total phenols and pectin methylesterase changes on quality maintenance on guava fruit (Psidium guajava L.) coated with candeuba wax solid lipid nanoparticles-xanthan gum

The objective of this work was to evaluate the application of candeuba wax solid lipid nanoparticles (SLN) and xanthan gum (XG) as coatings on guava, and their effect on the fruit's physicochemical and nutritional parameters, complementing a previous publication carried out by Zambrano-Zaragoza et al. (2013). The concentrations of SLN were selected according to those reported as the most (65g/L) and least (75g/L) efficient in post-harvest life preservation, and were compared to a coating of XG and untreated control samples. According to results, the submicron-sized systems used in the coatings with a particle size range of 267–344nm, a polydispersity index <0.2, and zeta potential of −22.8 to −30mV remained stable during 8weeks of storage. The best results were from the fruits coated with 65g/L of SLN and stored at 10°C, as they showed the lowest O2 and CO2 respiration rates and, consequently, less weight loss. They also had the best retention of ascorbic acid and total phenol content, with less change in fruit color compared to the control guava and those coated only with XG. These findings indicate that this batch continued their natural maturation process, but at a slower rate than the other samples. The firmness was affected by the activity of the enzyme pectin methylesterase, but results show that the 65g/L coating was efficient in maintaining fruit texture. In contrast, the 75g/L coating produced epoxy in the fruit, causing physiological damage. Finally, the guava coated with XG only had a maturation rate similar to that of the control fruit.

Effect of high pressure and thermal processing on spoilage-causing enzymes in mango (Mangifera indica)

The aim of the present work was to model the effect of combined pressure-temperature processing on spoilage-causing enzymes in mango pulp; which conventionally are inactivated using high temperatures leading to inevitable quality losses. The inactivation of enzymes pectin methylesterase (PME), polyphenol oxidase (PPO) and peroxidase (POD) was studied in mango pulp within the pressure, temperature and hold-time ranges of 0.1 to 600MPa, 40 to 70°C and 1s to 90min, respectively. The enzyme inactivation was described as a dual process: initial change in activity during dynamic pressure build-up phase and subsequent decrease under isobaric-isothermal conditions. The former led to considerable increase in activities of all the three enzymes (p<0.05); however, the increased activity reduced with increased intensity of applied pressure-temperature. On the other hand, isobaric-isothermal conditions led to substantial inactivation (p<0.05), with 600MPa/70°C/20min treatment being most effective in reducing the activities of PME, PPO and POD to 32, 15 and 26%, respectively.The enzyme inactivation data was non-linear under isobaric-isothermal conditions and fitted to the nth-order reaction model, indicative of the occurrence of series of reactions possibly due to pressure-temperature interaction effects. The estimated reaction order ‘n’ was 0.815, 1.106 and 1.137 for PME, PPO and POD, respectively. The estimated reaction rate constant k (min−1) depicted PME to be the most baroresistant enzyme followed by POD and PPO. Temperature and pressure dependency of k was expressed in terms of activation energy and activation volume using the Arrhenius- and Eyring-type relations, respectively. An empirical model with good correlation between actual and predicted data (R2>0.90) was proposed to simulate the rate of enzyme inactivation under isobaric-isothermal conditions as a function of pressure and temperature.

Extracellular enzymes activity determining the virulence of Rhizoctonia bataticola, causing root rot in soybean

Enzymes play crucial role in successful host-pathogen interactions and degradation of the cell wall. The cellulolytic, hemicellulolytic, pectolytic and proteolytic enzymes produced by plant pathogens are capable of degrading major polymeric components of the host cell wall. A number of pathogenic fungi have been reported to produce cellulases, but relatively a small quantum of plant pathogens are able to degrade insoluble cellulose even after it has been physically or chemically modified to make it more susceptible to enzyme action. Present study revealed Rhizoctonia bataticola as major cause of soybean root rot. Result of the R. bataticola, 20 isolates collected from various regions of Maharashtra, seven isolates were moderate virulent and thirteen isolates highly virulent. These isolates showed wide variability in per cent root rot infection of soybean ranged from 48.00 to 69.33%. Highest extracellular enzyme activity was found in respect of cellulase (Rb-33), pectinase (Rb-33), lipase (Rb-10), protease (Rb-32) and amylase (Rb-36). The per cent root rot infection was found to be highly significant and positively correlated with the enzyme viz., cellulase, pectinase and protease. The entire 20 test isolates exhibited production of extracellular enzymes under both plate culture and plant sample assay methods. Maximum enzyme activity profile from R. bataticola infected root tissues was found in respect of cellulolytic (Rb-1), polygalacturonase (Rb-32) and pectin methylesterase (Rb-32) enzyme. There was low enzyme activity even the isolates were more virulent and vice versa.

Textural Properties and Enzyme Activity of Mango (Mangifera indica L.) Fruit Coated with Chitosan during Storage

Mango is a tropical fruit and deteriorates very fast after harvest due to ripening and senescence. This study investigated the effect of different concentration of chitosan coatings 0.5, 1.0 and 1.5% on postharvest quality and activities of cell wall degrading enzyme on mango cv. Choke Anan fruit stored at 25°C for 12 days. Fruit not treated with chitosan served as the control. The results showed that pre-storage application of chitosan coatings, especially at 1.5% significantly reduced decay symptoms, weight loss, respiration rate, ion leakage, malondialdehyde (MDA) content and maintained higher firmness of mango fruit as compared to the control. Chitosan coating treatment inhibited polygalactronase (PG) and pectin methylesterase (PME) enzyme activities. Moreover, chitosan coatings had a positive effect on retaining higher total phenolic and antioxidant activity, which reduced in the control fruit. These results suggest that chitosan coatings might be protected the fruit from quick deterioration and maintained the quality of mango by enhancing the antioxidant defense system during storage.

Evolutionary origins of pectin methylesterase genes associated with novel aspects of angiosperm pollen tube walls

The early evolution of angiosperms was marked by a number of innovations of the reproductive cycle including an accelerated fertilization process involving faster transport of sperm to the egg via a pollen tube. Fast pollen tube growth rates in angiosperms are accompanied by a hard shank-soft tip pollen tube morphology. A critical actor in that morphology is the wall-embedded enzyme pectin methylesterase (PME), which in type II PMEs is accompanied by a co-transcribed inhibitor, PMEI. PMEs convert the esterified pectic tip wall to a stiffer state in the subapical flank by pectin de-esterification. It is hypothesized that rapid and precise targeting of PME activity was gained with the origin of type II genes, which are derived and have only expanded since the origin of vascular plants. Pollen-active PMEs have yet to be reported in early-divergent angiosperms or gymnosperms. Gene expression studies in Nymphaea odorata found transcripts from four type II VGD1-like and 16 type I AtPPME1-like homologs that were more abundant in pollen and pollen tubes than in vegetative tissues. The near full-length coding sequence of one type II PME (NoPMEII-1) included at least one PMEI domain. The identification of possible VGD1 homologs in an early-diverging angiosperm suggests that the refined control of PMEs that mediate de-esterification of pectins near pollen tube tips is a conserved feature across angiosperms. The recruitment of type II PMEs into a pollen tube elongation role in angiosperms may represent a key evolutionary step in the development of faster growing pollen tubes.

Arabidopsis Plants Expressing a Fungal Pectin Methylesterase Enzyme Have Reduced Degree of Polysaccharide Methylation and Exhibit a Dwarfed Phenotype and Resistance to Stresses

Pectin is a major component of the plant cell wall and is involved in functions including growth of the plant cell, organ development, and defense against pathogens. Our lab has developed a suite of transgenic Arabidopsis thaliana plants expressing microbial‐derived cell wall‐degrading enzymes to study Cell Wall Integrity (CWI) responses. Plants expressing one such enzyme, A. nidulans Pectin Methylesterase (AnPME), exhibit dwarfism beginning with emergence of the first true leaves and affecting all specialized organs and structures throughout their lifetime. These plants also possess reduced sensitivity to salt stress; while roots of AnPME plants are much smaller than wild‐type roots under unstressed conditions, root growth was not inhibited by 100 mM NaCl treatment. Preliminary results have also shown that AnPME plants are less susceptible to infection by the cyst‐forming nematode H. schaachtii. Ongoing research aims to quantify the degree of cell wall de‐methylesterification to correlate with degree of dwarfism, and further confirm resistance of roots to nematode penetration. These results illustrate the importance of pectin methylesterification status in plant fitness and development, as well as response to both biotic and abiotic stresses, most likely through CWI response.Support or Funding InformationLinder Family Undergraduate Research Fellowship, Rob Stupka Memorial Scholarship

Kinetic Assessment of High Pressure Inactivation of Different Plant Origin Pectinmethylesterase Enzymes

High pressure can be applied for the inactivation of endogenous enzymes detrimental to fruit and vegetable products. One of the enzymes that affect the quality of fruits and vegetables is pectinmethylesterase (PME), responsible for cloud destabilization and consistency changes. Depending on the desired quality of the developed product, PME can be partly or fully inactivated. In this review paper, the cited results in the literature of the high pressure inactivation of PMEs in model systems after extraction and purification as well as in real food systems is comprehensively presented. It is discussed that the pressure stability of PMEs can vary significantly, especially when comparing the more pressure-sensitive types, like orange juice (Valencia cv.) PME, with the more barotolerant ones like purified banana PME (Cavendish cv.). This variation can be attributed to the type of enzyme, the coexistence with other enzymes, type of substrates, ionic strength, pH and nature of the medium in which the enzyme is dispersed. This review may support the systematic evaluation and optimal design of fruit and vegetable product high pressure (HP) processing aiming to control their shelf-life, especially when considering that milder conditions are necessary for the inactivation of microorganisms compared to endogenous enzymes. Using literature data, an exponential mathematical model was uniformly applied to enable a better comparative assessment of pressure effects, on all PMEs discussed in this manuscript, obtained from different plant sources.

Enzyme inactivation of tomato juice by ohmic heating and its effects on physico‐chemical characteristics of concentrated tomato paste

AbstractFresh juice of fully ripe tomato was subjected to ohmic heat (OH) treatment (90°C for 1 min) and the effectiveness of treatment was compared with conventional hot break (CT) treatment (90°C for 5 min). PG (Polygalacturonase) and PME (Pectin methyl esterase) enzyme inactivation achieved by the OH (1 min.) was similar as compared to CT of 5 min. During the kinetic analysis it was observed that the inactivation of PME &amp; PG enzyme and degradation of ascorbic acid followed first order trend in ohmic as well as conventional treatment of tomato juice, however total color change (DE) was found to follow least‐squares non‐linear parameter algorithm behavior. Thermal treatments leads to the increased release of phyto‐chemicals from the matrix which results in a significant (p&lt;0.01) increase in lycopene content during the early phases of the treatments. The Paste (28±0.5 °Brix) obtained after pre‐treatment was analyzed for lycopene, ascorbic acid content and apparent viscosity and color. OH Paste was found more viscous than CT treatment with maximum viscosity of 2.33×103 mPa‐s. The color of OH treated paste was bright red as compared to CT treatment, however the lycopene and ascorbic acid content of paste were found similar in OH and CT. Based on results of present study it is concluded that the ohmic treatment may be applied as an efficient alternative to the conventional method of enzyme inactivation in tomato juice.

Utilização de biofilme comestível na conservação pós-colheita de pimentão verde (capsicum annuum L.)

A utilização de biofilmes comestíveis são uma das alternativas tecnológicas eficientes na manutenção da vida útil de frutos e hortaliças. A fina camada de material comestível atua como excelente propriedade de barreira artificial, e associada à refrigeração age mantendo a qualidade pós-colheita dos frutos. Este trabalho teve como objetivo avaliar a aplicação do biofilme a base de alginato de sódio sobre a manutenção da qualidade pós-colheita de pimentões verdes (Capsicum annuum L.). Os frutos foram selecionados, lavados, sanitizados, revestidos com 1% e 3% de alginato. Frutos sem revestimento foram utilizados como controle Após aplicação do revestimento os frutos foram armazenados em expositor vertical a 7°C e 87±1% UR por até 15 dias. A cada três dias Foram realizadas analises de perda de massa fresca, firmeza do fruto, teores de acidez titulável e de ácido ascórbico, pH, parâmetros de cor, e atividade da enzima pectinametilesterase (PME). O uso do revestimento foi eficiente em retardar o metabolismo dos frutos de pimentão. O revestimento também foi capaz de manter por mais tempo a firmeza dos frutos quando comparados com o controle. Frutos revestidos apresentaram maiores valores de SS e AT, menor atividade da enzima pectinametilesterase, menor perda de massa fresca, e melhor aspecto visual durante os 15 dias de armazenamento.

Influence of effectors pectin methylesterase alfalfa deesterification kinetics of pectin substances

The modern technology of food production enzyme preparations with pectolytic activity were used in technological operations of clarification of juices, as well as in the production of juices with pulp, which makes them indispensable in the processing of berries, fruits and vegetables. In basis of their use in technologies ability of deeterificashon lies and to depolymerize a pectin. The resulting pectin methylesterase herbaceous crops - alfalfa, possible to obtain an environmentally friendly preparation. One of the most important features of pectin methylesterase alfalfa enzyme preparation is the presence in its composition two catalytically active sites that, despite the high degree of homology differ in substrate specificity, affinity for inhibitors capable of activating cations. Influence of effectors by modifying the Michaelis constant and maximum reaction velocity as a result of the interaction of activators and inhibitors of the enzyme pectin preparation alfalfa as with the free form of the enzyme and to the enzyme-substrate complex. Experiments have shown that the resistance to the natural inhibitors of the enzyme preparation exceeds the data of microbiological origin of "Pectofoetidin P20х", which allows to increase the technological properties of the plant enzyme. An important fact is also that the Ca2 + ions and pyrocatechol widely present in fruit and vegetable raw materials, so the study and characterization of their influence on the behavior of pectolytic enzyme preparation with selective functional features, allowing to get low esterificated pectin, possessing both detoxifying and gelling properties, is the justification of the relevance research data. Thus, pectin methyl esterase enzyme alfalfa product most adapted to the biological system plant material, indicating that the high catalytic ability

Thermal inactivation kinetic of pectin methylesterase and cloud stability in sour orange juice

Heat treatment is a common method to improve cloud stability of high acid food products such as sour orange juice. Inactivation of pectin methylesterase enzyme (PME), naturally found in citrus, is known as a heat treatment index for these products. In this work, the kinetics of PME thermal inactivation and cloud stability in sour orange juice were investigated. The fresh sour orange juice was heated in a controlled water bath at 60, 70, 80 and 90 °C for different times depending on applied temperature. Time–temperature data was simultaneously recorded using a data-logger. The inactivation kinetics of PME was calculated in terms of thermal resistance parameters (D & Z values), activation energy, enthalpy, entropy and free energy. The obtained Z-value (36.90 °C), activation energy (62.61 ± 0.84 kJ/mol) and free energy (93.52–96.37 kJ/mol) revealed the high stability of PME during the heat treatment. Based on thermal resistance of PME, heating times were corrected by considering the come-up time effectiveness. The results showed that cloud value of heated juice increased by PME inactivation during heat treatment.

Harvesting period of Murici (Byrsonima crassifolia Kunth) fruit in relation to physical and chemical parameters evaluated during fruit development

The fruits were harvested for six consecutive years during the rainy season from a population native to a savannah environment, and they were analyzed at intervals of seven days after anthesis (DAA). Chemical analyses were conducted (pH, total acidity, soluble solids, total and reducing sugars, total and soluble pectin, polygalacturonase enzyme (PG) and pectin methyl esterase (PE) enzymes, phenolic compounds, vitamin C and antioxidant activity by the oxygen radical absorbance capacity (ORAC) and α, α-diphenyl-β-picrylhydrazyl (DPPH) methods), respiratory activity was determined, and physical evaluations were performed (diameter and fruit and pulp fresh weight). The experiment was conducted in a completely randomized design (CRD) with a regression analysis and model fitting using the statistical F-test at a 5% significance level. The results showed climacteric behavior of the fruit as well as significant antioxidant activity related to the presence of phenolic compounds and vitamin C. The harvesting time, according to the evaluated parameters, was determined to be the interval between 28 and 35DAA.

Micropilar and embryonic events during hydration of Melanoxylon brauna Schott seeds

Abstract:Germination is a complex process that involves molecules properties that make up the cell walls, hydrolytic enzymes that break the bonds between the polymers and action of reactive oxygen substance. Melanoxylon braunais a forest species of high economic value. In order to evaluate the physiological and biochemical changes that occur in the embryonic axis during germination, fresh matter, length, activities of the enzymes pectin methylesterase, polygalacturonase, superoxide dismutase, catalase, peroxidase and hydrogen peroxide levels were quantified in the embryonic axis. Furthermore, in the micropyle area the composition of carbohydrates and micropyle physical resistance were evaluated with and without drying. During soaking, if there are increases in fresh matter and length of the embryonic axis, there is the same trend of polygalacturonase and pectin methylesterase enzymes. The hydrogen peroxide content was reduced during the soaking, as well as the puncture force of the micropylar area. It is concluded that the seed coat and the cotyledons are responsible for 90% of the water soaked by the seeds. The events in the micropyle and embryonic axis occur independently in the first 16 hours. The weakening of the micropyle features an elastic step and a plastic one. Enzymes pectin methylesterase and polygalacturonase act in cellular expansion of the embryonic axis.

Effects of high hydrostatic pressure and temperature increase on Escherichia coli spp. and pectin methyl esterase inactivation in orange juice.

The aim of this study was to evaluate the effect of high hydrostatic pressure treatment combined with moderate processing temperatures (25 ℃-50 ℃) on the inactivation of Escherichia coli O157: H7 (ATCC 700728), E. coli K12 (ATCC 23716), and pectin methyl esterase in orange juice, using pressures of 250 to 500 MPa with times ranging between 1 and 30 min. Loss of viability of E. coli O157:H7 increased significantly as pressure and treatment time increased, achieving a 6.5 log cycle reduction at 400 MPa for 3 min at 25 ℃ of treatment. With regard to the inactivation of pectin methyl esterase, the greatest reduction obtained was 90.05 ± 0.01% at 50 ℃ and 500 MPa of pressure for 15 min; therefore, the pectin methyl esterase enzyme was highly resistant to the treatments by high hydrostatic pressure. The results obtained in this study showed a synergistic effect between the high pressure and moderate temperatures in inactivating E. coli cells.