Inactivation Of Pectinesterase Research Articles

Effect of Electric Field on Pectinesterase Inactivation During Orange Juice Pasteurization by Ohmic Heating

This study evaluated effect of alternating electric field on pectinesterase activity in 5-mL Navel orange juice samples subject to ohmic pasteurization. An empirical Weibull kinetic model for enzyme inactivation was fitted to data from conventional and ohmic heating runs. Discretization of time-dependent inactivation rates allowed accounting for a nonisothermal process, with similar equivalent times between paired runs indicating comparable time-temperature profiles across heating methods. Conditions were 60 Hz, 32–36 V/cm, holding temperatures 60–90 °C, holding times 0–200 s in a custom cell with stirring, and two Ti-Pt electrodes. Residual pectinesterase activity was assayed with a traditional titration method at pH 7.5 and 30 °C. The stochastic Monte Carlo resampling method of smoothed bootstrap estimated the parameter populations to propagate experimental uncertainty on enzyme activity. Joint parameter populations and confidence regions agree with least squares estimates, and indicate that kinetic parameters depend on heating technology. This difference is evidence of electric field effects on pectinesterase activity, which is more evident at lower heat process intensities; however, the thermal denaturation seems to overcome other effects at higher processing times and temperatures. The finding that there are conditions where electric fields significantly affect enzyme inactivation highlights the importance of thoroughly assessing effects of alternative processing technologies on targets and indicators in food processing.

Effects of Dense Phase Carbon Dioxide Pasteurization on the Physical and Quality Attributes of a Red Grapefruit Juice

Red grapefruit juice was treated with continuous dense phase carbon dioxide (DPCD) equipment to inactivate yeasts and molds and total aerobic microorganisms. A central composite design was used with pressure (13.8, 24.1, and 34.5 MPa) and residence time (5, 7, and 9 min) as variables at constant temperature (40 degrees C), and CO(2) level (5.7%) after experimentally measuring CO(2) solubility in the juice. Five log reduction for yeasts and molds and total aerobic microorganisms occurred at 34.5 MPa and 7 min of treatment. A storage study was performed on the fresh juice DPCD treated at these conditions. degrees Brix, pH, titratable acidity (TA), pectinesterase (PE) inactivation, cloud, color, hue tint and color density, total phenolics, antioxidant capacity, and ascorbic acid were measured after the treatment and during 6 wk storage at 4 degrees C. During storage, the DPCD-treated juice showed no growth of total aerobic microorganisms and yeasts and molds. Cloud increased (91%) while percent PE inactivation was partial (69.17%). No significant (alpha= 0.05) differences were detected between treated and untreated samples for degrees Brix, pH, and TA. Treated juice had higher lightness and redness and lower yellowness. No significant differences (alpha= 0.05) were detected for the hue tint values while the color density value was higher for the treated samples compared to the untreated. The treatment and the storage did not affect the total phenolic content of the juice. Slight differences were detected for the ascorbic acid content and the antioxidant capacity. The experimental results showed evidence that the treatment can maintain the physical and quality attributes of the juice, extending its shelf life and safety.

Modeling within the Bayesian framework, the inactivation of pectinesterase in gazpacho by pulsed electric fields

The inactivation of pectinesterase (PE) activity in gazpacho (a Spanish ready-to-use cold vegetable soup) under pulsed electric fields (PEFs) was studied. Samples were exposed to 4 μs monopolar or bipolar square-wave pulses at 5–35 kV cm −1 electric field intensity for up to 1500 μs and 200 Hz (temperature below 40 °C). Inactivation of PE was greater when treatment time and electric field intensity increased, and bipolar pulses were more effective inactivating PE than monopolar ones. Estimation of parameters and quantities involved in the tested models were performed within the Bayesian framework. The kinetic evolution of the enzyme was explained using a 3-parameter biexponential model based on a mechanism involving two irreversible consecutive steps. Rate constant k 1 was not dependent on neither electric field intensity nor pulse polarity. Rate constant k 2 and ratio between the activities of intermediate forms and the native ones of the enzyme Λ were affected by those conditions.

Inactivation of Lemon Pectinesterase by Thermosonication

The combined effect of ultrasound and temperature (thermosonication) on the inactivation of lemon pectinesterase was examined. The experiments were separated into two groups. The first ones were performed at 40°C-90°C, ambient pressure with ultrasonication of 20 kHz. The other ones were carried out at 40°C-90°C without ultrasonication. After heating at 50°C with the ultrasonic treatment for 63 min, the residual activity was 83% decreased whereas without the ultrasound the residual activity was only 30% decreased. The D-values show that the combination treatment has more influence on the inactivation of pectinesterase.

Models in a Bayesian framework for inactivation of pectinesterase in a commercial enzyme formulation by pulsed electric fields

The inactivation of pectinesterase (PE) in a commercial enzyme formulation (CEF) under pulsed electric fields (PEF) was studied. Samples of an aqueous solution of the CEF were exposed to exponential waveform pulses for up to 16 ms at electric field intensities ranging from 5 to 24 kV cm−1. Pulses were delivered in monopolar mode. The observed inactivation of the enzyme was described by several kinetics and regarding the input of electrical energy density (Q) models using Bayesian non-linear regression. Posterior distributions of the characteristic parameters for each kinetic model (based on the Hulsheger or the Weibull equation) and each Q model (based on exponential decay or the Weibull equation) were obtained. Kinetics models based on the Weibull equation showed better goodness and accuracy than the other models.

Reduction of pectinesterase activity in a commercial enzyme preparation by pulsed electric fields: comparison of inactivation kinetic models

AbstractThe inactivation of pectinesterase (PE) in a commercial enzyme preparation (CEP) under high intensity pulsed electric fields (HIPEF) was studied. After desalting and water dilution of the raw CEP, samples were exposed to exponentially decay waveform pulses for up to 463 µs at electric field intensities ranging from 19 to 38 kV cm−1. Pulses were applied in monopolar mode. Experimental data were fitted to a first‐order kinetic model as well as to models based on Fermi, Hülsheger or Weibull equations to describe PE inactivation kinetics. Characteristic parameters for each model were calculated. Relationships between some of the parameters and process variables were obtained. The Weibull model yielded the best accuracy factor. The relationship between residual PE and input of electrical energy density was found to be that of exponential decay. Copyright © 2005 Society of Chemical Industry

A kinetic study on pectinesterase inactivation during continuous pasteurization of orange juice

Studying pectin esterase inactivation behavior is important because it is responsible for the juice cloud stability loss, is composed of several isoenzymes and occurs naturally in orange. Freshly squeezed juice of ‘pera’ orange ( Citrus Sinensis (L) Osbeck) was pasteurized at temperatures of 82.5 °C, 85.0 °C and 87.5 °C using ARMFIELD laboratory plate heat exchanger. At least five runs with different holding times were conducted for each temperature. As the obtained isothermal curves showed deviation from the expected first-order kinetics, data was statistically treated applying a non-linear regression and the estimated best fit was a three-parameter-multicomponent-first-order model. At 82.5 °C, the isothermal curves showed a non-zero asymptote of inactivation indicating that at this temperature the most heat resistant isoenzyme could not be totally inactivated. The 87.5 °C isotherm showed the highest inactivation among the temperatures studied. These facts agree with the batch inactivation data found in literature, but the holding time required for a satisfactory inactivation was significantly smaller than the found in literature, suggesting that the proposed model can be used to design continuous process with more accuracy.

RESIDUAL PECTINESTERASE ACTIVITY IN DEHYDRATED ONION AND GARLIC PRODUCTS

During the dehydration of onion and garlic products, use of high temperatures is undesirable due to the potential loss of aroma and flavor characteristics. As a consequence, residual pectinesterase (PE) activity may be found in these dehydrated spices. This study reports the presence of PE activity in raw onions and in dehydrated onion and garlic products. Pectinesterase activity is higher in the raw onion stem disks, and dehydrated products made from this tissue, than in the bulbs. Dehydrated onion products induced gelation of citrus pectin solutions and tomato purees. Although some inactivation of PE in dehydrated onion water suspensions and extracts was observed after 10 min at 50C, complete inactivation required 2 min at 82C. Commercial dehydration operations may require reevaluation to eliminate residual PE activity in dehydrated onion and garlic products.

THERMAL INACTIVATION KENETICS of PECTINESTERASE EXTRACTED FROM ORANGES

A study was carried out on the kinetics of thermal inactivation of pectines terase (PE), extracted from the pulp of Valencia and Navel oranges. Moreover, the influence of intrinsic factors on the kinetics of Navel orange PE was investigated. In a citric acid buffer, at a pH of 3.7 and 4.2, the enzyme was more thermostable as compared to water. However, at pH 3.2 an increased inactivation and an increased temperature sensitivity of the rate constant was observed. Ca2+-ions also enhanced the inactivation, whereas the temperature sensitivity of the rate constant decreased. In presence of sucrose, a diminished inactivation of PE was observed, and addition of sucrose only slightly influenced the activation energy.

Inactivation of Pectinesterase in Orange and Grapefruit Juices by High Pressure

The enzyme pectinesterase (PE) reduces the quality of citrus juices. Current inactivation of the enzyme is accomplished by heat, resulting in a loss of fresh fruit flavor in the juice. We explored the use of pressurized treatments of orange and grapefruit juices to bypass the use of extreme heat during processing. PE inactivation using isostatic high pressure in the range of 500−900 MPa was accomplished in orange and grapefruit juices. The higher pressures (>600 MPa) caused instantaneous inactivation of the heat labile form of the enzyme but did not inactivate the heat stable form of PE. Treatment times caused significantly different (α = 0.05) total PE activity losses in orange but not in grapefruit juices, and PE inactivation at different pressures was significantly different in both juices. Heat labile grapefruit PE was also more sensitive than orange to pressure. Dp values for orange PE inactivation at 500 and 600 MPa were 83.3 and 2.4 min, respectively; while the zp value between 500 and 600 MPa was ...

COMPARISON OF INVERTASE AND PECTINESTERASE INACTIVATION IN PROCESSED TOMATO PULP1

ABSTRACTThe heat stability of pectinesterase (PE) and invertase in tomato pulp was investigated to examine the feasibility of using invertase inactivation to predict pectinesterase inactivation. Both invertase and PE were inactivated at 80C in macerated tomato pulp. Between temperatures of 65C to 75C invertase was less heat stable than PE. Results indicate that when temperatures above 80C are reached, almost instantaneously, it would be feasible to use invertase activity as measured by sucrose level to predict PE activity.

Inactivation of Pectinesterase in Orange Juice by Supercritical Carbon Dioxide

ABSTRACTSingle strength orange juice was treated with supercritical carbon dioxide (CO2) and the effect of process time, temperature and pressure on pectinesterase (PE) activity was determined. PE could be inactivated with supercritical CO2 below temperatures necessary for thermal inactivation. Higher pressure, temperature and longer treatment time resulted in more inactivation. Inactivation kinetics showed activation energy was significantly reduced at SC C02 treatment at 31 MPa (97.4 KJ/mole), compared to identical treatments at atmospheric pressure (166.6 KJ/mole). D values ranged from 2673 min at atmospheric pressure and 40°C to 10 min at 31 MPa and 60°C. z value at atmospheric pressure was 8.8C°, and at 31 MPa 5.2C°.

Kinetic compensation relations for ascorbic acid degradation and pectinesterase inactivation during orange juice pasteurisations

AbstractThe thermal degradation kinetics of ascorbic acid and the inactivation kinetics of pectinesterase were studied experimentally with pH‐adjusted orange juice. No simple trends were observed in variation of the kinetic parameters with pH, but both kinetic functions agreed with kinetic compensation relations. An isokinetic temperature was observed for ascorbic acid degradation at pH 2.5, 3.0, and 3.5 implying that the same degradation mechanism was valid at these pH values. A large deviation at pH 4.0 from this isokinetic reaction rate implied that the degradation mechanism was different at this pH. There was no isokinetic temperature for pectinesterase inactivation reactions, indicating that pectinesterase was inactivated by different mechanisms at different pH values. The variation of the inactivation mechanism of pectinesterase with pH was attributed to its more complex molecular structure.

Pressure Inactivation of Yeasts, Molds, and Pectinesterase in Satsuma Mandarin Juice: Effects of Juice Concentration, pH, and Organic Acids, and Comparison with Heat Sanitation

Satsuma mandarin juice, the concentrated juice and the acid-free juice were prepared and treated with pressures of 1000–6000 bar after mixing with organic acids, various yeasts and molds, or pectinesterase, to study the effects of pressure on inactivation of microorganisms and the enzyme. The effects of heat treatment were also studied in similar conditions. As results, the inactivation effect of pressure on microorganisms and the enzyme was decreased by increasing juice concentration. Pressure-induced inactivation of microorganisms was not affected by either juice pH (between 2.5 and 4.5) or kinds of organic acids (citric, tartaric, lactic, or acetic acid). With 9 species of yeasts and molds tested, pressurization at 3500 bar for 30 min or at 4000 bar for 5 min was required to reduce them to 1/105 or below 1/105. Microorganisms resistant to heat tend to be highly resistant to pressure. Although no complete inactivation of pectinesterase was attained after pressurization at 3000 or 4000 bar for 10 min, th...

Low pH Inactivation of Pectinesterase in Single Strength Orange Juice

ABSTRACTFrozen orange juice concentrate (63.8° Brix) was reconstituted with water to single strength juice and supplemented with a commercial citrus pectinesterase (PE) to give an activity of 1.5 PE units/mL juice. Reconstituted juice and freshly squeezed single strength orange juice were treated with a cation exchange resin. Resin treatment decreased the pH of the juice from 3.75 to 2.0 and completely inactivated PE. PE was also inactivated following acidification of the juice to pH 2.0 with concentrated hydrochloric acid. Very little cloud loss occurred in refrigerated (4°C) juice at pH 2.0 for approximately 12 wk; however, a loss (> 95%) of ascorbic acid resulted. Only microorganisms died‐off rapidly (> 99.9%) in juices adjusted to pH 2.0 using ion exchange resin, but not in juices lowered to pH 2.0 with HCl.

Heat Inactivation of Pectinesterase in Orange Juice Pulp

ABSTRACTHeat inactivation of pectinesterase in juice pulp was nonlinear suggesting the presence of fractions of pectinesterase with differing heat stabilities. The residual activity rapidly decreased to 4% upon heating for 19 sec at 80°C and decreased very little upon subsequent heating for up to 180 sec at 80°C. The D values (time to inactivate 90% of the enzyme) at 90°C of the heat sensitive and heat stable fractions were estimated to be 0.225 and 32 sec, respectively. The Z values (change in temperature to achieve a 10‐fold change in time of inactivation) were estimated to be 10.8°C and 6.5°C for the sensitive and stable fractions, respectively.

Effect of Total Solids Level on Heat Inactivation of Pectinesterase in Orange Juice

ABSTRACTPectinesterase (PE) heat inactivation at various Brix did not obey first order reaction kinetics. Inactivation of PE at 10 ‐ 35° Brix did follow straight line semilogarithm plots of enzyme activity versus time. However, at 40° Brix and above the semi‐log graph between PE activity versus time was unclear. At high Brix levels a protective effect seemed to occur because the rate of enzyme inactivation declined. Increasing enzyme concentration in the 40° Brix sample showed that the curve was S‐shaped or sigmoidal. Increasing pH from 4 to 7 decreased the “Thermal Death Time” from 18 set to 4 sec.

Pectinesterase Activity, Pectin Methylation, and Texture Changes During Storage of Blanched Cucumber Slices

ABSTRACTPectin methylation in blanched cucumber slices after 6 months’storage in acid brine (pH 3.7) ranged from 9% (no blanch) to 48% (99°C, 3 min blanch). An 81°C blanch caused complete pectinesterase inactivation, but 15 ‐ 20% reactivation occurred during storage. After a 99°C blanch, only slight reactivation was observed. Pectinesterase was not inactivated at 66°C or less, but up to 85% of the activity was lost during storage. Firmness changes were complex. A clear relationship between pectin methylation and firmness changes was not observed. A 66 or 81°C blanch resulted in best firmness retention. Calcium ion was very effective in prevention of firmness loss regardless of the extent of pectin methylation.

Determination of a thermal process schedule for guava (Psidium guajava Linn.)

SummaryA thermal process schedule for guava canned in syrup has been evolved on the basis of inactivation of pectinesterase (PE) which was found to be more heat resistant than peroxidase. The values for thermal inactivation and thermal resistance of PE in syrup homogenate containing guava pulp and sugar syrup in the ratio of 11:6 and total soluble solids content of 20% at pH 4.0 were respectively. The F value of 1 was equivalent to 1.69 D. In commercial canning, a 2.5 D process is recommended which ensures a microbiologically safe and organoleptically acceptable product.Process time was calculated both by graphical and formula methods. Calculation by the formula method using slopes of heating and cooling curves plotted on semilog paper by least squares analysis, and fh/U:g tables for actual values of jc gave process times very close to those obtained by the graphical method. The process times required at different initial and processing temperatures are given.To minimize viscosity increase in the covering syrup during storage, firming of guava in 1% calcium chloride solutions for 30 min prior to canning is suggested. In addition, use of covering syrup containing 0.125% ascorbic acid with or without citric acid (0.06%) yields a product of good colour, texture and flavour.

Determination of Thermal Process Schedule for Acidified Papaya

ABSTRACTThe pH of papaya varies from 4.2‐5.65 and is required to be lowered to enable processing at atmospheric pressure. A thermal process has been evolved on the basis of inactivation of pectinesterase (PE), the heat resistant enzyme naturally present. The values for thermal inactivation of PE in pulp were F26.8212= 1.04 and D27212= 0.39 at pH 4.0. In the syrup homogenate of 20% TSS, the values were F27.6207.3= 1.00 and D29207.3= 0.53 at PH 3.8, and F27.2212= 1.23 and D27.5212= 0.8 at pH. 4.0. These F values in syrup homogenate were equivalent to 1.88D at pH 3.8 and 1.5 3D at pH 4.0. In commercial canning, a 2.5D process at pH 3.8 and 2.0D process at pH 4.0 which are equivalent to the F values of 1.33 and 1.31, respectively, are recomended. Using these F values, process times for different processing conditions were calculated by graphical method and compared with values found by three different procedures of the formula method. The thermal process, thus evolved on the basis of enzyme inactivation, resulted in a safe and acceptable product.