Influence of high pressure homogenization and pulp reduction on residual pectinmethylesterase activity,cloud stability and acceptability of Lane Late orange juice: A study to obtain high quality orange juice with extended shelf life

Lane Late orange juice with extended shelf life (3 months at 3 °C) was obtained by high pressure homogenization (HPH) at 150 MPa at 68 °C for 15 s. Residual pectinmethylesterase (PME) inactivation level achieved was 75% but its cloudiness was maintained during storage and its acceptability undistinguishable from that of fresh juice during the assayed period. Juices with entire and reduced (50% and 25%) pulp contents were also homogenized at 150 MPa at different temperatures (63 °C and 58 °C for 15 s) to establish an appropriate shelf life of orange juices according to a desired level of cloudiness. Results showed how cloud stability of pulp reduced samples, even with a residual PME inactivation level above 90%, was not satisfactory (as in the case of entire juices homogenized out of 68 °C). The proposed methodology can easily be implanted by citrus industry to obtain high quality chilled orange juices with prolonged shelf life.     

Changes in orange juice characteristics due to homogenization and centrifugation

Two common operations in citrus plants are homogenization and centrifugation. By homogenization, the size of suspended particles decreases and, therefore, cloudiness and color intensity increase. By centrifugation, the total pulp content is controlled. The objective of this paper is to quantify the effect of these operations (and of their combination) on color, cloudiness, suspended pulp, particle size of cloud components, and pectin methylesterase (PME) activity, either in the whole juice or in the two fractions obtained by centrifugation. Results showed that homogenization at 20 MPa give low-pulp well-colored orange juices, although additional treatments are necessary to reduce residual PME activity. Juices with similar physical characteristics were obtained either when the whole juice was homogenized, or when homogenization was applied only to the pulpy fraction obtained by centrifugation and then blending this fraction back with the low pulp fraction.     

Effect of pH,temperature and maturity on pectinmethylesterase inactivation of citrus juices treated by high-pressure homogenization

The effects of high-pressure homogenization (HPH) at 150 MPa combined with heating at 58, 63 and 68 °C on inactivation of pectinmethylesterase (PME) were studied in orange and Clementine juices. Juices covering a range of total soluble solids (°Bx) to acid ratios (10.2–15.0 in oranges and 9.2–19.4 in Clementines) were adjusted to pH 3.1, 3.5 and 3.9 before homogenization. Results indicated how the residual PME activity of homogenized samples was greatly attenuated by lowering the pH and in a lesser extent by increasing the homogenization temperature (finding orange enzymes more HPH sensitive than their Clementine counterparts). Generally, ripeness of fruits had little influence on PME inactivation (especially in Clementine juices). In any case, orange and Clementine samples with pH 3.1 and homogenized at 68 °C showed residual PME activities below 10% of the initial value from their respective fresh juices.     

Stability of black carrot anthocyanins in various fruit juices and nectars

Fruit juices (apple, grape, orange, grapefruit, tangerine and lemon) and nectars (apricot, peach and pineapple) were coloured with black carrot juice concentrate and stability of black carrot anthocyanins in these matrices was studied during heating at 70–90 °C and storage at 4–37 °C. Anthocyanin degradation, in all coloured juices and nectars, followed first-order reaction kinetics. During heating, black carrot anthocyanins in apple and grape juices showed higher stability than those in citrus juices at 70 and 80 °C. High stability was also obtained for the anthocyanins in peach and apricot nectars at these temperatures. Black carrot anthocyanins were the least stable in orange juice during both heating and storage. During storage, degradation of anthocyanins was very fast at 37 °C, especially in pineapple nectar. Refrigerated storage (4 °C) markedly increased the stability in all samples. Activation energies for the degradation of black carrot anthocyanins in coloured juices and nectars ranged from 42.1 to 75.8 kJ mol⁻¹ at 70–90 °C and 65.9–94.7 kJ mol⁻¹ at 4–37 °C.     

Clarification of Citrus Juice is Influenced by Specific Activity of Thermolabile Pectinmethylesterase and Inactive PME-Pectin Complexes

ABSTRACT: Thermolabile pectinmethylesterase (PME) from Valencia orange pulp was extracted, partially purified by cation exchange chromatography (IEX), and added to reconstituted orange juice at 2 units/ml. Of the juices that clarified, %T increased, cloud particle size increased and % degree of esterification (DE) decreased in the 15 d storage study. The rate of clarification was most rapid for juices with added PME extracts that never bound Hi-Trap SP and contained 36 and 27 kDa peptide, intermediate for crude extracts of PME not applied to IEX, and lowest for PME extracts that bound Hi-Trap SP and contained 36 and 13 kDa peptide. These results suggest that PME-pectin complexes and low peptides moderate PME activity and juice clarification.     

Calcium Supplementation and Processing Variable Effects on Orange Juice Quality

Untreated, pectinesterase treated, low pulp, and pectinase treated orange juices were fortified to 20% RDA of calcium with calcium carbonate or calcium phosphate/lactate (75/25). Neither calcium supplement adversely affected flavor, cloud density, settling pulp, or viscosity in untreated, low pulp, or pectinase treated juices. PME exposed orange juice held 4 hr before pasteurization and calcium supplementation had less cloudy density, increased viscosity and more settling pulp. Calcium carbonate fortified PME exposed and pectinase treated juices had lower flavor scores, while calcium phosphate suspensions caused slightly lower color scores of all juices.     

Quality of Freeze Concentrated Orange Juice

Pasteurized Valencia and Temple orange juices concentrated to 45°Brix by freeze concentration retained their fresh juice flavor. Direct steam infusion heating to inactivate enzymes allowed more rapid heating than indirect heating and successfully lowered juice peel oil during vacuum cooling. Except for considerable pulp reduction of feedstream juices, there were few differences from normal citrus juice recovery procedures for freeze concentration. Since the product retained most of the aroma constituents of fresh juice, careful handling and high quality feed juice prior to freeze concentration was much more important than for evaporation. Fresh juice freeze concentrated to 45°B, then pasteurized at temperatures of 80°, 97° and 111°C had reduced sucrose (up to 25%) as the temperature increased to 111°C.     

Effect on Orange Juice of Batch Pasteurization in an Improved Pilot-Scale Microwave Oven

ABSTRACT:  The effects on orange juice batch pasteurization in an improved pilot-scale microwave (MW) oven was evaluated by monitoring pectin methyl-esterase (PME) activity, color, carotenoid compounds and vitamin C content. Trials were performed on stirred orange juice heated at different temperatures (60, 70, 75, and 85 °C) during batch process. MW pilot plant allowed real-time temperature control of samples using proportional integrative derivative (PID) techniques based on the infrared thermography temperature read-out. The inactivation of heat sensitive fraction of PME, that verifies orange juice pasteurization, showed a  z -value of 22.1 °C. Carotenoid content, responsible for sensorial and nutritional quality in fresh juices, decreased by about 13% after MW pasteurization at 70 °C for 1 min. Total of 7 carotenoid compounds were quantified during MW heating: zeaxanthin and β-carotene content decreased by about 26%, while no differences ( P  < 0.05) were found for β-cryptoxanthin in the same trial. A slight decrease in vitamin C content was monitored after MW heating. Results showed that MW heating with a fine temperature control could result in promising stabilization treatments.     

Physical–chemical and sensory properties of pulsed electric field and high hydrostatic pressure treated citrus juices

The consumers have increasing desire towards fresh, long shelf-life and healthy products by consisting favourable sensory properties. As an ambivalent fact appears that the product should meet all these requirements and should be consumable long time. All these demands lead to the importance of the minimal processing methods. The properties of widely common citrus juices (100% orange, – grapefruit, – and tangerine juice) were analyzed by measuring the possible changes in the physical–chemical parameters (pH, Brix°, electric conductivity, colour) respectively the aroma and acid content. The applied technology was pulsed electric field (in furthers: PEF) treatment with the parameters of 28 kV/cm with 50 pulses; respectively high hydrostatic pressure (HHP) technology with the parameter of 600 MPa pressure for 10 min treatment time. The sensory properties of the juices were analyzed with electronic-nose and -tongue to measure the possible changes of the treated juices compared to the untreated (control) samples with the help of these electronic tools, which can serve as a potential detection system for the differentiation of the treatments mentioned above.

Industrial relevance

Fruit juices are preserved mainly by heat treatment which can change many prosperous flavour- , acid and sensory properties. The present work shows in case of citrus juices the application of pulsed electric field treatment and high hydrostatic pressure techniques as non-thermal preservation possibilities and the use of electronic tongue and – nose as a new method for sensory testing.     

Novel,non-thermal hydrodynamic cavitation of orange juice: Effects on physical properties and stability of bioactive compounds

Effect of hydrodynamic cavitation (HC) at pressure 3–15 bar and treatment time5–25 min on physical and chemical qualities of orange juice was investigated. Processing parameters were optimized on the basis of retention of vitamin C and antioxidant activity; inactivation of pectin methyl esterases (PME) and peroxidase (POD) enzyme and stability of pH, °Brix, viscosity, titratable acidity and total color difference. HC of orange juice at 5 bar 15 min and 13 bar 10 min resulted into maximal overall desirability at 0.52 and 0.40 respectively. No significant change in °Brix, pH, titratable acidity for fresh and cavitated orange juice was observed. Only 21% and 13% of reduction in PME and POD respectively was recorded. A 94% and 91% of antioxidant activity and vitamin C retention was noted in both optimized samples. This study demonstrated that HC can produce orange juice more economically with better physical properties and nutritional value.Industrial relevanceThe demand for more natural, preservative free with highest nutritional bioactive containing juices has created a need of non-thermal processing. Hydrodynamic cavitation (HC) processing is novel, emerging and under explored technology for fruit juices. HC due to the formation of cavities and shock waves causes enzyme and microbial inactivation at low temperature while retaining natural bioactives with fresh-like organoleptic characteristics. It is believed worldwide that non thermal technologies like HC will be among the most cost effective, scalable and impactful liquid food processing technologies in the coming decades especially for commercial products.     

Formation of α-terpineol in Citrus Juices, Model and Buffer Solutions

The formation of α-terpineol from its putative precursors in citrus juice (d-limonene and linalool) was investigated in juice, buffers and model solutions. α-Terpineol content was higher in commercial lemon juice than in orange or grapefruit juices. Its content exceeded its taste threshold of 2.5 mg/L in orange juice stored for 1 month at 35 °C. During storage of homogenized model solutions fortified with d-limonene or linalool, α-terpineol was simultaneously formed and degraded, especially at 45 °C and its formation was strongly dependent on pH. Linalool was a more reactive substrate than limonene for α-terpineol formation; the protonation in linalool was faster than in limonene. However, since there was more limonene than linalool in citrus juices, a-terpineol appeared to have been formed to about the same extent from both precursors.     

Orange Juices and Concentrates Stabilization by a Proteic Inhibitor of Pectin Methylesterase

A proteic inhibitor of pectin methylesterase (PME), recently discovered in kiwi, was used to stabilize cloud of orange juice concentrate with “Cut-back,” 42° Brix. To concentrated and pasteurized orange juice were added increasing amounts of fresh juice (12° Brix) with PME 0.8 U/mL at the fresh to pasteurized ratios 6.6 to 38%. The PME inhibitor (65% pure), from kiwi, was added at 50 mg/L. After 8 mo at 5°C samples were compared with controls containing the same amount of fresh juice with PME inhibited by pasteurization. Pasteurized samples were not different from those treated with PME inhibitor. Conversely, where PME was not inhibited, cloud stability decreased with increasing amounts of fresh juice. Use of kiwi PME inhibitor in fruit juice production has potential advantages.     

Application of a multi-pass high-pressure homogenization treatment for the pasteurization of fruit juices

This work evaluates both the effects of a multiple-pass high-pressure homogenization treatment on the microbial inactivation of selected microbial strains (Saccharomyces cerevisiae, Lactobacillus delbrueckii, Escherichia coli) inoculated into commercial fruit juices (orange, red orange, pineapple) as well as the application of this non-thermal technology to the pasteurization of fresh juices (Annurca apple juice). The pressure level ranged from 50 to 250 MPa, the number of passes from 1 to 5 and the inlet temperature from 2 to 20 °C.Preliminary tests in distilled water showed that the efficiency of the multiple-pass treatment significantly depends on both the homogenizing pressure as well as the microbial species. The subsequent extension of the multiple-pass treatment to the inactivation of S. cerevisiae inoculated into three different fruit juices (orange, red-orange and pineapple juice) highlighted that the inactivation induced by the high pressure treatment did not depend on the properties of the tested juices and was not statistically different from inactivation in water (p value < 0.05). These findings were supported by the comparison of two different mathematical models used to fit the inactivation kinetics, whose fitting parameters were not significantly different for water and the fruit juices for any pressure level applied.Three homogenization passes at 150 MPa and 25 °C, which resulted to be optimal for yeast inactivation in fruit juices, were effective for the stabilization of the endogenous microbial load of fresh Annurca apple juice. The treated apple juice showed a minimum shelf-life of 28 days under refrigerated conditions, during which the natural qualities of the fresh juice were completely preserved.     

Inactivation of pectinmethylesterase in fresh orange juice by cold atmospheric plasma technology: A kinetic study

Preservation of fruit juices requires the inactivation of natural endogenous enzymes, such as pectinmethylesterase (PME). Within this work, cold atmospheric plasma (CAP), and in particular a dielectric barrier plasma jet fed with helium gas, was demonstrated to effectively inactivate PME of freshly squeezed orange juice in short treatment times (2–30 min). By a combination of temperature measurements and a multidimensional heat transfer model, the temperature profile of the whole sample during plasma treatment was extracted. It was found that the thermal phenomena were not a driving factor for PME inactivation. Plasma treatment of orange juices resulted in inactivation of 55–80% of PME with <5.0% of PME inactivation caused by the temperature increase from 20 to 90 °C. The Weibull distribution model compared to the first-order fractional, the sigmoidal logistic and the Hulsheger's kinetic models was found to better describe mathematically (R² > 0.99; A_f = 1.002–1.052) the effect of CAP processing on residual PME activity. Multi-parameter equation fits allowed the prediction of residual PME activity as a function of the applied voltage, helium flow, and treatment time. Generally, higher voltages and lower helium flows applied led to higher PME inactivation rates in fresh orange juice.     

Carotenoid and flavanone content during refrigerated storage of orange juice processed by high-pressure, pulsed electric fields and low pasteurization

The impact of different processing technologies, including non-thermal technologies, on bioactive compounds of orange juice was investigated. Freshly squeezed orange juice was treated by high pressure (HP) (400 MPa/40 °C/1 min), pulsed electric fields (PEF) (35 kV cm⁻¹/750 μs) and low pasteurization (LPT) (70 °C/30 s). The stability of main carotenoids and flavanones was studied just after treatment and during 40 days of refrigerated storage at 4 °C. Just after treatment, HP juice showed a significant increase on total carotenoid and flavanone content extracted (45.19 and 15.46%, respectively) and on vitamin A value (30.89%) with regard untreated juice, whereas no significant changes were observed for PEF and LPT juices. For all treated orange juices, flavanone content decreased significantly (around 50%) during the first 20 days of storage at 4 °C while carotenoid content showed a moderate decrease (less than 11%) that took place during the last 20 days. In general, during refrigerated storage, carotenoids and flavanones remained higher in HP juice than in LPT and PEF juices. Hence, HP and PEF technologies were as effective o even more than LPT to preserve bioactive compounds in orange juice during refrigerated storage.     

Modification of pectin by pectinmethylesterase and the role in stability of juice beverages

The colloidal stability of juices and pectin stabilized juice drinks depends in part on the charge and charge properties of pectins. The effect of pectinmethylesterases (PMEs) from Valencia juice sacs on the rate of clarification of citrus juice and modification of pectin are described in this study. Partially purified PME extracts that contained peptides at 36,000 and 27,000 daltons are more likely to cause clarification of citrus juices than PME extracts that contained peptides at 36,000 and 13,000 daltons. In the presence of active PME, cations enhance clarification and increase particle size of citrus juices. PME extracts that contained 36,000 and 13,000 peptides de-esterified commercial pectin in the presence of sodium chloride at pH 7.5, without loss of molecular weight. Based on elution from ion exchange, pectins of greater charge density are created at longer reaction times with PME, but some pectin chains remained unmodified.     

Effect of air-drying temperature on physico-chemical properties of dietary fibre and antioxidant capacity of orange (Citrus aurantium v. Canoneta) by-products

Dehydration promoted important modifications affecting both the physico-chemical properties of dietary fibre (DF) and the antioxidant capacity of orange by-products (peel and pulp remaining after juice extraction). The significance of such changes was largely dependent on the air-drying temperature used (from 30 °C to 90 °C). The major modifications on the DF components were observed when either extended drying periods, i.e. at lower temperatures, or elevated drying temperatures were applied. Dehydration around 50–60 °C apparently promoted the minor disruption of cell wall polymers, in particular of pectic substances. Pulp samples exhibited higher values of swelling (SW) and fat adsorption capacity (FAC) than those derived from orange peel. Although, significant decreases in water retention capacity (WRC), FAC and solubility values were detected for both by-products as the air-drying temperature increased. The antioxidant capacity associated to dehydrated citrus by-products was significantly higher for orange peel than for pulp samples. In general, the by-products studied proved to be quite resistant to the different heat treatments applied within the range of 40–70 °C. In overall, the study shows that, in order to preserve either the DF quality and/or the antioxidant capacity, air-drying temperature should be controlled since both types of compounds, DF components and antioxidants, might be degraded or modified either when extended drying periods and/or high drying temperatures are applied.     

The effect of pre-treatment on the anthocyanin and flavonol content of black currant juice (Ribes nigrum L.) in concentration by reverse osmosis

Reverse osmosis process for the concentration of black currant juice was carried using AFC-99 tubular membrane at 30 °C and 45 bar. The contents of selected flavonols and anthocyanins were analyzed after centrifugation; enzyme treatment by Panzym Super E and by Rohapect berry followed by centrifugation; and ultrafiltration black currant juices and juice concentrates. The total soluble solid (TSS) content of the juices increased from the initial 17.6–17.9 °Brix to 24–24.8 °Brix in the case of the centrifuged juice in the concentration process. Similarly, it increased from 14.5–15.5 °Brix to 23.1–23.4 °Brix for the Panzym Super E treated juice, and from 16.1–16.9 °Brix to 22.5–23.1 °Brix for the Rohapect berry treated black currant juices. The ultrafiltered juice had the lowest initial TSS content between 14.1 and 14.9 °Brix and it increased to 22.1–23.1 °Brix. The average permeate fluxes during the concentration process were 7.3 L m⁻² h⁻¹ for the centrifuged juice, 11.9 L m⁻² h⁻¹ for the Panzym Super E treated juice, 9.2 and 13.1 L m⁻² h⁻¹ for the Rohapect berry treated and ultrafiltered juice, respectively. Analysis indicated that the enzymatic treatment resulted in the increase of anthocyanin and flavonol content of the juices. The centrifugation process decreased the amount of anthocyanins and flavonols to some extent. The juice clarified by ultrafiltration had significantly lower concentrations of anthocyanins and flavonols, while the juices treated by Panzym Super E had the highest levels of these flavonoids. This study recommends enzymatic pre-treatment by Panzym Super E, since it improves the permeate flux in reverse osmosis during the concentration process, and results in a juice concentrates highest in anthocyanins and flavonols.