Effect of pH on Enzyme Inactivation Kinetics in High-Pressure Processed Pineapple (Ananas comosus L.) Puree Using Response Surface Methodology

Effect of pH and high-pressure process treatments viz. pressure, temperature, and dwell time on inactivation of polyphenoloxidase (PPO), peroxidase (POD), bromelain (BRM), and pectinmethylesterase (PME) in pineapple puree was studied. Experiments were conducted according to rotatable central composite design (RCCD) within the range (?α to?+?α) of 100–600 MPa, 20–70 °C, and 0–30 min at three different pH levels (3.0, 3.5, and 4.0) followed by analysis through response surface methodology (RSM). Enzyme inactivation was significantly (p?k in min^?1) revealed that PPO was the most resistive (k ranged between 0.0020 and 0.0379 min^?1) when compared with other three enzymes within the experimental domain. Increased k at lower pH with constant pressure and temperature depicted that pH had negative effect on the inactivation process. The optimized conditions targeting maximum inactivation of PPO, POD and PME with simultaneous retention of BRM in pineapple puree, were 600 MPa/60 °C/9 min, 600 MPa/60 °C/10 min and 600 MPa/60 °C/10 min for the samples of pH 3.0, 3.5, and 4.0, respectively.     

High Pressure and Temperature Effects on Enzyme Inactivation in Strawberry and Orange Products

High hydrostatic pressure treatment (50-400 MPa) combined with heat treatment (20–60°C) effects on peroxidase (POD), polyphenoloxidase (PPO) and pectin methylesterase (PME) activities of fruit-derived products were studied. Assays were carried out on fresh orange juice and strawberry puree. Pressurization/depressurization treatments caused a significant loss of strawberry PPO (60%) up to 250 MPa and POD activity (25%) up to 230 MPa, while some activation was observed for treatments carried out in 250–400 MPa range for both enzymes. Optimal inactivation of POD was using 230 Mpa and 43°C in strawberry puree. Combinations of high pressure and temperature effectively reduced POD activity in orange juice (50%) to 35°C. The effects of high pressure and temperature on PME activity in orange juice were very similar to those for POD.     

Optimisation of High Hydrostatic Pressure Processing of Pêra Rio Orange Juice

The influence of high hydrostatic pressure (HHP) on Pêra Rio orange juice was investigated using response surface methodology. A central composite design was used to evaluate the effects of three processing conditions (independent variables), namely pressure (100–600 MPa), temperature (30–60 °C) and time (30–360 s), on the native microflora and pectin methylesterase (PME) activity of orange juice. Analysis of variance showed that second-order polynomial models fitted well with the experimental data for PME residual activity (R ²?=?0.9586, p?<?0.001) and aerobic microorganism count (R ²?=?0.9879, p?<?0.001). The optimum HHP processing conditions to produce orange juice with PME residual activity of less than 20 % and low microorganism count (<2 log cycles CFU/mL) were 550 to 600 MPa, 55 to 60 °C and 330 to 360 s.     

Modeling the inactivation kinetics of fruit bromelain in pineapple during high-pressure and thermal treatments

The stability of fruit bromelain (FBM) in pineapple pulp was studied within a high-pressure domain of 0.1–600 MPa/30–70 °C/1 s–30 min. The pulse effect was quantified as a function of pressure, temperature, pressure build-up and decompression times. A maximum of 60% reduction in FBM activity was obtained after a single pulse of 600 MPa/70 °C. Upon applying nth order model, the obtained reaction order (n) for thermal (0.1 MPa/30–70 °C) and high-pressure (100–600 MPa/30–70 °C) inactivation was 1.1 and 1.2, respectively. The inactivation rate constant (k) ranged from 1.2 to 45.0 × 10^− 3 U^n − 1 min^− 1. The activation energy was nonlinearly dependent on pressure (P); whereas, the activation volume was linearly related to temperature (T). The nonlinear dependence of k on P and T was modeled by an empirical equation. The D-values obtained from the empirical model appeared to be more realistic than those from the log-linear kinetics.Industrial relevancePineapple fruit bromelain (FBM) has numerous health benefits and therapeutic effects. It is a protease enzyme that helps in digestion. Processing of pineapple pulp needs attention towards retaining the maximum FBM activity in it. A detailed kinetic study of FBM within a broad range of pressure–temperature–time domain will help in designing a high-pressure process for the pineapple pulp with respect to its bromelain stability.     

Kinetic study of high pressure microbial and enzyme inactivation and selection of pasteurisation conditions for Valencia Orange Juice

Keeping quality of fresh orange juice is highly dependent on pectinolytic enzyme activity and the growth of spoilage microorganisms. The inactivation kinetics of indigenous pectin methylesterase (PME) and of the two more pressure resistant species of spoilage lactic acid bacteria (LAB) Lactobacillus plantarum and L. brevis in freshly squeezed Valencia orange juice under high hydrostatic pressure (100–500 MPa) combined with moderate temperature (20–40 °C) was investigated. PME inactivation followed first order kinetics with a residual PME activity (15%) at all pressure–temperature combinations used. The values of activation energy and activation volume were estimated at each pressure and at each temperature, respectively. Values of 90 kJ/mol and ?30 mL/mol at reference pressure of 300 MPa and reference temperature of 35 °C were estimated respectively. The corresponding z_T and z_P values of LAB inactivation were also estimated at all conditions tested. Values of 19.5 °C and 95 MPa at reference pressure of 300 MPa and reference temperature of 30 °C were estimated respectively for L. plantarum, while the corresponding values for L. brevis were 40 °C and 82 MPa, respectively, at the same reference conditions. Pressure and temperature were found to act synergistically both for PME and LAB inactivation. The PME and LAB inactivation rate constants were expressed as functions of the temperature and pressure process conditions. These functions allow the determination of the pressure/temperature conditions that achieve the target enzyme and microbial inactivation at a selected processing time. The process conditions of 350 MPa at 35 °C for 2 min are proposed as effective for Valencia orange juice cold pasteurisation.     

Inactivation Kinetics of the Most Baro-Resistant Enzyme in High Pressure Processed Litchi-Based Mixed Fruit Beverage

This work focused on a litchi-based mixed fruit beverage, comprising of coconut water and lemon juice, mixed in an optimized proportion. Based on preliminary studies, three resistant spoilage enzymes were identified in the beverage, viz. polyphenol oxidase (PPO), peroxidase (POD), and pectin methyl esterase (PME). The response surface methodology (RSM) based on central composite face-centered design (FCCD) screened out PPO as the most resistant enzyme within the high pressure processing (HPP) domain of 200–600 MPa/30–70 °C/0–20 min. A detailed kinetic study was conducted on PPO inactivation within the same HPP domain along with a set of thermal treatments (0.1 MPa/30–70 °C). A synergistic effect of pressure and temperature on PPO inactivation was observed, throughout the HPP domain. However, PPO was almost completely inactivated at 500 MPa/70 °C/20 min. The inactivation order (n) values for PPO were 1.10 and 1.25 for thermal and HPP treatments, respectively. For every 10 °C rise in temperature, the inactivation rate constant (k, U^n-1 min^?1) increased approximately by 1.5 times, within 50–70 °C (at 0.1 MPa), while a 10-fold increase was obtained in the case of HPP treatments. The activation energy (E _a ) and the activation volume (V _a), depicting the temperature and pressure dependence of k, was found to decrease slightly, with an increase in pressure and temperature, respectively. The PPO inactivation rate constant was modeled as a function of both temperature and pressure conditions by combining both Arrhenius and Eyring equations.     

Inactivation Kinetics of Peach Pulp Pectin Methylesterase as a Function of High Hydrostatic Pressure and Temperature Process Conditions

A kinetic study of the inactivation of endogenous pectin methylesterase (PME) in Greek commercial peach pulp under high hydrostatic pressure (HHP; 100–800 MPa) combined with moderate temperature (30–70 °C) was conducted. Thermal inactivation of the enzyme at ambient pressure conditions was also studied. PME inactivation was modeled by first order kinetics at all conditions tested. High pressure and temperature acted synergistically on PME inactivation, except at the high temperature of 70 °C at the middle pressure range (100–600 MPa), where an antagonistic effect of pressure and temperature was observed. At this specific middle pressure range, an increase of pressure processing led to increased inactivation rate constants of peach PME. A multiparameter model was developed to express the PME inactivation rate constant as a function of temperature and pressure process conditions, taking into account the dependence of both activation energy and activation volume on pressure and temperature, respectively. A good correlation between experimental and predicted values of inactivation rate constants was established. This modeling approach enables the quantitative estimation of the HHP–temperature conditions needed to achieve a targeted PME inactivation in the peach pulp.     

Separation and thermal characterization of ionically and tightly cell-wall-bound pectin methylesterase from cucumbers (Cucumis sativus)

Thermal characteristics of cell-wall-bound pectin methylesterase (PME) from cucumbers were determined. Heat inactivation of PME followed first-order reaction kinetics. Biphasic inactivation curves indicated the presence of heat-labile and heat-stable fractions. Inactivation of PME accelerated above 65??°C. The z values between 70??°C and 80??°C were 7.6??°C and 9.0??°C for heat-stable fractions of ionically (IPME) and tightly cell wall bound PME (TPME), respectively. Temperature optima for the initial activities of IPME and TPME were 65??°C and 60??°C, respectively. However, for longer periods of activity determination, both IPME and TPME showed a temperature optimum at 50??°C. The E _a values for initial activities were 5?kcal mol^–1 (20–65??°C) and 7.2?kcal mol^–1 (20–60??°C) for IPME and TPME, respectively.     

Changes in Quality Attributes During Storage of High-Pressure and Thermally Processed Pineapple Puree

The primary issue of the pineapple puree processing industry is its limited stability. The study compares the quality changes in high-pressure and thermally processed pineapple puree at different storage conditions and estimates the shelf-life. The untreated (S1) and treated samples (S2, S3, and S4 treated at 600 MPa/50 °C/13 min, 600 MPa/70 °C/20 min, and 0.1 MPa/95 °C/12 min, respectively) packed in ethylene vinyl alcohol (EVOH) and multi-layered (ML) polyethylene terephthalate (PET) pouches were stored up to 125 days at 5, 15, and 25 °C. The total color change (?E*) and browning index during storage increased according to zero-order kinetic model, whereas ascorbic acid (AA), total phenolics, and total antioxidant capacity followed the first-order decay. The overall sensory acceptability (OA) of S2 was higher than both S3 and S4 at 5 °C, and it dropped rapidly at 15 and 25 °C. The activity of polyphenol oxidase and pectin methylesterase in S3 and S4 was less than 10 % up to 120 days at 5 °C. The consistency (κ) and residual enzyme activity in S2 decreased with storage duration and temperatures. For estimating the shelf-life, the change in OA was crucial for S2 and S3, whereas retention of AA served as the critical parameter for S4. The sample S2 packed in ML pouch was found to be the best sample having the shelf-life (microbial count?<?6-Log cfu g^?1, ?E*?<?12, OA?>?5, and AA?>?200 mg kg^?1) of 120, 50, and 25 days at 5, 15, and 25 °C, respectively.     

THERMAL AND HIGH-PRESSURE STABILITY OF PURIFIED PECTIN METHYLESTERASE FROM PLUMS (PRUNUS DOMESTICA)

Pectin methylesterase (PME) from greengage plums (Prunus domestica) has been extracted and purified using affinity chromatography. Only one band on sodium dodecyl sulfate–polyacrylamide gel electrophoresis was obtained, with an estimated molecular weight of 31 kDa. On isoelectric focusing electrophoresis, two bands with neutral isoelectric points (6.8 and 7.0) were detected. The optimal pH and temperature for plum PME activity were 7.5 and 65C, respectively. A study of purified plum PME thermostability was performed at pH 7.5 and 4.0, indicating a higher thermostability at pH 7.5 than at pH 4.0. A biphasic inactivation behavior was observed for thermal treatments (54–70C), whereas its pressure inactivation could be described by a first‐order kinetic model in a pressure range of 650–800 MPa at 25C. Purified plum PME was found to be relatively stable to thermal and pressure (≤600 MPa) treatments, compared to PME from other fruits.     

Selection of Process Conditions for High Pressure Pasteurization of Sea Buckthorn Juice Retaining High Antioxidant Activity

Sea buckthorn berries juice is a nutritious beverage, rich in vitamin C and carotenoids with high antioxidant activity. The main requirements for a freshly squeezed sea buckthorn juice production are the cloud stability and antioxidant activity retention after processing. Appropriate process technologies and conditions have to be applied in order to inactivate pectin methyl esterase (PME), responsible for cloud loss, while maintaining the nutritional characteristics and antioxidant activity of the juice. The objectives of the present work were to study and model the effect of thermal treatment and high pressure (HP) processing on the inactivation kinetics of endogenous PME and on total antioxidant activity alteration. Thermal treatment significantly affected PME inactivation and residual antioxidant activity. Processing even at mild process conditions (60 °C for 1 min) resulted in 2.5-fold antioxidant activity reduction and 50 % PME inactivation compared to untreated sample. Pressure and temperature acted synergistically for PME inactivation that followed first-order kinetics with a residual PME activity at all pressure–temperature combinations used (200–600 MPa and 25–35 °C). The effect of temperature and pressure on the inactivation rate constants was expressed through the activation energy and activation volume, respectively. Values of 163 kJ/mol and ?17 mL/mol at reference pressure of 600 MPa and reference temperature of 35 °C were estimated, respectively. Antioxidant activity of the samples was expressed through the determination of the effective concentration (EC₅₀). A slight increase in sea buckthorn antioxidant activity when applying pressures (200–600 MPa) at ambient temperature (25 °C) was observed compared to the corresponding value of untreated juice. Processing at higher temperatures did not significantly alter the total antioxidant activity of sea buckthorn juice. For sample treated at 600 MPa–35 °C for 5 min, a 5 % reduction of total antioxidant activity was observed. These conditions are proposed as effective process conditions for sea buckthorn juice cold pasteurization, based on the higher antioxidant activity retention and simultaneous PME inactivation.     

Response Surface Optimization of Process Parameters and Fuzzy Analysis of Sensory Data of High Pressure–Temperature Treated Pineapple Puree

The high‐pressure processing conditions were optimized for pineapple puree within the domain of 400‐600 MPa, 40‐60 °C, and 10‐20 min using the response surface methodology (RSM). The target was to maximize the inactivation of polyphenoloxidase (PPO) along with a minimal loss in beneficial bromelain (BRM) activity, ascorbic acid (AA) content, antioxidant capacity, and color in the sample. The optimum condition was 600 MPa, 50 °C, and 13 min, having the highest desirability of 0.604, which resulted in 44% PPO and 47% BRM activities. However, 93% antioxidant activity and 85% AA were retained in optimized sample with a total color change (?E*) value less than 2.5. A 10‐fold reduction in PPO activity was obtained at 600 MPa/70 °C/20 min; however, the thermal degradation of nutrients was severe at this condition. Fuzzy mathematical approach confirmed that sensory acceptance of the optimized sample was close to the fresh sample; whereas, the thermally pasteurized sample (treated at 0.1 MPa, 95 °C for 12 min) had the least sensory score as compared to others.     

Comparison of Microbial Inactivation and Rheological Characteristics of Mango Pulp after High Hydrostatic Pressure Treatment and High Temperature Short Time Treatment

The effects of high hydrostatic pressure (HHP) treatments at pressures of 300–600 MPa for 1–20 min and of high-temperature, short-time (HTST) treatment on the inactivation of natural microorganisms in blanched mango pulp (BMP) and unblanched mango pulp (UBMP) were investigated. No yeasts, molds, or aerobic bacteria were detected in BMP or UBMP after HHP treatments at 300 MPa/15 min, 400 MPa/5 min, 500 MPa/2.5 min, and 600 MPa/1 min and HTST treatment at 110 °C/8.6 s. Therefore, these conditions were selected to study the effects of HHP and HTST treatments on pectin methylesterase (PME) activity, water-soluble pectin (WSP) levels, and the rheological characteristics of UBMP and BMP. HHP treatment at a pressure of 600 MPa for 1 min significantly reduced PME activity in UBMP and significantly activated PME in BMP, whereas pressures of 300–500 MPa activated PME regardless of blanching. However, PME activity was reduced by 97 % in UBMP and was completely inactivated in BMP by HTST treatment. WSP levels were significantly decreased by HHP treatment but were increased by HTST treatment in UBMP and BMP. Both HHP and HTST treatments increased the viscosity, storage modulus, and loss modulus of UBMP and BMP. No significant changes in total sugar, total soluble solids, titratable acid, or pH were found after any treatment.     

Process stability of Capsicum annuum pectin methylesterase in model systems, pepper puree and intact pepper tissue

Process stability studies towards temperature and/or pressure on pepper pectin methylesterase (PME) were carried out in different systems (purified form, crude extract, pepper pieces and puree) at pH 5.6. Within the temperature range studied (22–80 °C, 5 min), pepper PME in pure form and crude extract was gradually inactivated showing a biphasic inactivation behaviour, indicating the presence of isoenzymes of different thermostability. Pepper samples heated for 15 min showed a maximum of residual PME activity around 55 °C. Isothermal inactivation of pepper PME in purified form and crude extract at pH 5.6 could be described by a biphasic inactivation model for the temperature range studied (62–76 °C). A stable behaviour towards high-pressure/temperature treatments (400–800 MPa/25–60 °C) was observed for crude extract and purified pepper PME. PME in pepper puree samples revealed to be very pressure stable. Mild temperatures combined with pressure treatments seem to increase the extractability from PME in pepper tissue, probably due to the effect on the cell structure.     

Pressure-Thermal Kinetics of Furan Formation in Selected Fruit and Vegetable Juices

Furan, a potential carcinogenic compound, can be formed in array of processed foods. The objective of this study was to conduct kinetic studies in pineapple juice and assess the interactive effects of pressure (0.1 to 600 MPa) and temperature (30 to 120 °C) on furan formation. Additional experiments were carried out in tomato, watermelon, cantaloupe, kale, and carrot juice to understand the influence of matrix and juice pH. Furan was monitored in raw (control) and processed samples by automated headspace gas chromatography mass spectrometry, and quantified by calibration curve method with d₄-furan as internal standard. The data were modeled using zero-, first-, and second-order equations. The zero-order rate constants (k _T,P ), activation energy (E _a ), and Gibbs free energy of activation (ΔG ^?) of furan formation in thermally processed (TP; 90–120 °C) pineapple juice were found to be 0.036–0.55 μg/kg/min, 98–114 kJ/mol, and 173.9–180.5 kJ/mol, respectively. Furan concentration was negligible and close to the detection limit (0.37 μg/kg) after pressure treatment (600 MPa at 30 °C) of juice samples. For similar process temperatures, the rate constants of pressure-assisted thermally processed (PATP; 600 MPa at 105 °C) pineapple juice were lower than that of TP samples. Furan formation was influenced by juice matrix and pH. On the other hand, PATP markedly suppressed furan (0.7 to 1.6 μg/kg) in these selected juices. In conclusion, furan formation increased with process temperature and treatment time, while pressure treatment at ambient temperature did not promote its production. Furan formation in TP fruit juices was also influenced by juice matrix and pH, but these were not the significant factors for PATP-treated juices.     

Effect of High Hydrostatic Pressure and Temperature on Enzymatic Activity and Quality Attributes in Mango Puree Varieties (cv. Tommy Atkins and Manila)

Pectinmethylesterase (PME), peroxidase (POD), and polyphenoloxidase (PPO) residual activities (RAs) and physicochemical parameters (pH, total soluble solids (TSS), water activity (a_w), viscosity and color) of Tommy Atkins and Manila mango purees (MPs) were evaluated after high hydrostatic pressure (HHP) treatments at 400–550 MPa/0–16 min/34 and 59 °C. HHP treatment applied at 59 °C induced higher enzyme inactivation levels than the treatment applied at 34 °C in both MPs. The lowest RA of PME (26.9–38.6%) and POD (44.7–53%) was achieved in Manila MP treated at 450 MPa/8–16 min/59 °C and 550 MPa/4–16 min/59 °C, respectively. Otherwise, Tommy Atkins puree pressurized at 550 MPa/8–16 min/59 °C had the lowest PPO RA (28.4–34%). A slight decrease in pH and TSS values of both HHP-processed MPs at 34 and 59 °C was observed, whereas the a_w remained constant after processing. The viscosity of MPs tended to augment up to 2.1 times due to the application of HHP. No significant changes were observed in color parameters of Tommy Atkins MP, except at 550 MPa and 59 °C where higher yellow index (YI) (122.4?±?3.3) and lower L* (37.3?±?5.3) were obtained compared to the untreated MP. HHP caused an increase in L* values in Manila MP, whereas no clear trend was observed in YI. HHP processing at 550 MPa combined with mild temperature (59 °C) during 8 min could be a feasible treatment to reduce enzymatic activity and preserve fresh-like quality attributes in MP.     

Thermal and High-Pressure Stability of Pectinmethylesterase, Polygalacturonase, β-Galactosidase and α-Arabinofuranosidase in a Tomato Matrix: Towards the Creation of Specific Endogenous Enzyme Populations Through Processing

The thermal and pressure stability of tomato pectinmethylesterase (PME), polygalacturonase (PG), β-galactosidase (β-Gal), and α-arabinofuranosidase (α-Af) were investigated in situ. Enzyme inactivation by thermal and high-pressure processing (respectively 5 min at 25–95 °C at 0.1 MPa and 10 min at 0.1–800 MPa at 20 °C) was monitored by measuring the residual activity in crude enzyme extracts of treated tomato purée samples. PME was completely inactivated after a 5-min treatment at 75 °C. Only 30 % of the pressure stable PME was inactivated after a treatment at 800 MPa (20 °C, 10 min). A 5-min treatment at 95 °C and a treatment at 550 MPa (20 °C, 10 min) caused complete PG inactivation. β-Gal and α-Af activities were already reduced significantly by thermal treatments at 42.5–52.5 °C and 45–60 °C, respectively. These enzymes were, however, rather pressure resistant: treatments at respectively 700 and 600 MPa were necessary to reduce the activity below 10 % of the initial value. Assuming that first-order, fractional conversion or biphasic inactivation models could be applied to the respective enzyme inactivation data, inactivation rate constants and their temperature or pressure dependence for the different enzymes were determined. Based on differences in process stability of the enzymes, possibilities for the creation of specific “enzyme populations” in tomato purée by selective enzyme inactivation were identified. For industrially relevant process conditions, the enzyme inactivation data obtained for tomato purée were shown to be transferable to intact tomato tissue.     

Enzyme Activity and Nutritional Quality of Peach (Prunus persica) Juice: Effect of High Hydrostatic Pressure

The inactivation of polyphenol oxidase and pectin methylesterase in peach juice was investigated after high hydrostatic pressure processing at 400–600 MPa and 25°C for 5–25 min, respectively. At 400 MPa, polyphenol oxidase and pectin methylesterase were activated by 7.3 and 2.6%. At 500 and 600 MPa, polyphenol oxidase and pectin methylesterase were inactivated significantly with increasing the pressure and time, and the inactivation kinetics was fitted by the first order model. Moreover, some physio-chemical properties were studied. The results revealed that high hydrostatic pressure treatment preserved more L-ascorbic acid and maintained the color and sensory quality better than thermal treatment.     

超高压处理对鲜橙汁中果胶酶及过氧化物酶活性的影响

为推进国内非冷冻浓缩橙汁加工业的发展,对新型超高压杀菌技术对橙汁中酶钝化的效果进行研究,采用200～600MPa超高静压处理鲜榨橙汁,使用紫外分光光度法、滴定法分别测定鲜橙汁中过氧化物酶(POD)和果胶酶(PME)的活性,进行两种酶在常温下超高压钝化酶一级动力学拟合研究。结果表明：在常温条件下200MPa处理10min使两种酶轻微激活,在300～600MPa条件下,随压力和处理时间的增大,两种酶钝化反应明显,且符合一级动力学模型,且果胶酶对压力钝化更加敏感。     

Thermal and High-Pressure Stability of Pectin-Converting Enzymes in Broccoli and Carrot Purée: Towards the Creation of Specific Endogenous Enzyme Populations Through Processing

The thermal and pressure stability of broccoli and carrot pectin-converting enzymes, in particular pectinmethylesterase (PME), β-galactosidase (β-Gal), and α-arabinofuranosidase (α-Af), were investigated in vegetable purée matrices. In situ enzyme inactivation by thermal and high-pressure processing (respectively 5 min at 25–80 °C at 0.1 MPa and 10 min at 0.1–800 MPa at 20 °C) was evaluated by measuring the residual enzyme activity in crude extracts of treated carrot, broccoli floret, and broccoli stem purée samples. PME was completely inactivated in all vegetable purée matrices after a 5-min treatment at 80 °C. After a treatment at 800 MPa (20 °C, 10 min) only 77–90 % of pressure stable PME was inactivated, depending on the matrix. β-Gal and α-Af enzymes were inactivated in the vegetable purée matrices by thermal treatments respectively at 67.5–72.5 and 80 °C. These enzymes showed some pressure resistance: treatments respectively at 600–700 and 600–750 MPa were necessary for one log-reduction of β-Gal and α-Af activity in the different purées at 20 °C. Under the assumption of a first-order inactivation model, inactivation rate constants and their temperature or pressure dependency were determined for the different enzymes. Based on differences in process stability of the enzymes in the individual purée matrices, the feasibility for the creation of specific endogenous enzyme populations by selective processing was evaluated.