Comparing equivalent thermal, high pressure and pulsed electric field processes for mild pasteurization of orange juice. Part I: Impact on overall quality attributes

Mild heat pasteurization, high pressure processing (HP) and pulsed electric field (PEF) processing of freshly squeezed orange juice were comparatively evaluated examining their impact on microbial load and quality parameters immediately after processing and during two months of storage. Microbial counts for treated juices were reduced beyond detectable levels immediately after processing and up to 2 months of refrigerated storage. Quality parameters such as pH, dry matter content and brix were not significantly different when comparing juices immediately after treatment and were, for all treatments, constant during storage time. Quality parameters related to pectinmethylesterase (PME) inactivation, like cloud stability and viscosity, were dependent on the specific treatments that were applied. Mild heat pasteurization was found to result in the most stable orange juice. Results for HP are nearly comparable to PEF except on cloud degradation, where a lower degradation rate was found for HP. For PEF, residual enzyme activity was clearly responsible for changes in viscosity and cloud stability during storage.

Industrial relevance

Development of mild processing technologies with a minimal impact on fruit juice can be considered as a true alternative of fresh fruit. The present work presents a fair comparison of mild heat treated, high pressure (HP) and pulsed electric field (PEF) processed orange juice as an alternative for thermal pasteurization. Orange juices were monitored during two months of storage.     

Investigating consumers' perception of apple juice as affected by novel and conventional processing technologies

This work evaluates consumers' perception of apple juice processed by high pressure processing (HPP) and pulsed electric field (PEF) compared with thermal processing. As a case study, young Chinese immigrants living in New Zealand were selected. Targeting a broad understanding of process impact, three industrially relevant apple cultivars (New Zealand Jazz, Rose and Granny Smith) were chosen. The consumer study was performed using napping with ultra‐flash profiling technique (n = 38). The process impact on sensory perception seems to vary among the investigated apple cultivars. For Jazz and Granny Smith apple cultivars, PEF‐ and HPP‐treated juices are perceived as fresh, natural, sweet and balanced flavour. For Rose apple cultivar, however PEF‐processed juices appear to be perceived as fresh flavour in comparison with HPP and thermally treated juices. Moreover, thermal processing caused cooked flavour. With respect to colour, immediately after processing, HPP retains the natural apple juice colour compared with other treatments.     

Pasteurization of carrot juice by combining UV-C and mild heat: Impact on shelf-life and quality compared to conventional thermal treatment

The combination of UV-C radiation and mild heat (UV-H) treatment is a promising strategy for synergistically increasing microbial inactivation in low UV-transmitting juices. In this research, we explored the suitability of UV-H treatment in carrot juice pasteurization and its impact on juice quality during shelf-life compared to that of thermal pasteurization. UV-H treatment at 60 °C (3.92 J/mL, 3.6 min) enabled reductions of over 5 log₁₀ cycles in the reference pathogens and a significant reduction in spoilage yeasts, bacteria, and bacterial spores. The activity of pectin methylesterase and polyphenol oxidase was reduced by UV-H treatment to levels close to those of low-temperature pasteurization (60 °C/18.1 min). The native population of total aerobic bacteria, lactic acid bacteria, and yeasts and molds of UV-H-treated juice remained undetectable during 29 days of cold storage. Furthermore, viscosity, cloud stability, and the color of fresh juice were better preserved by UV-H treatment than by thermal pasteurization throughout storage.Industrial relevanceThis study demonstrates that UV-H treatment is a beneficial alternative to conventional thermal processing in carrot juice pasteurization, since appropriate inactivation levels of pathogenic and spoilage microorganisms can be reached while better preserving the quality attributes of fresh juice throughout its shelf-life.     

Cost Analysis and Environmental Impact of Pulsed Electric Fields and High Pressure Processing in Comparison with Thermal Pasteurization

The cost of high pressure processing (HPP) and the environmental impact of pulsed electric fields (PEF), HPP and thermal pasteurization of orange juice were estimated in the US. The cost analysis was based on commercial processing conditions that were validated for a 2-month shelf-life of orange juice under refrigeration conditions. Total electricity consumption was estimated to be 38,100 and 1,000,000 k Wh/year for thermal and HPP processing, respectively. Total pasteurization cost of HPP was estimated to be 10.7 ¢/l for processing 16,500,000 l/year (3,000 l/h). Of this, capital costs accounted for 59 % (6.3 ¢/l), labor costs accounted for 37 % (4.0 ¢/l) and utility charges, mainly electricity, accounted for 4 % (0.4 ¢/l). The total HPP cost was 7-folds higher than that of conventional thermal processing (1.5 ¢/l). The equivalent CO₂ emission was 90,000 kg for thermal processing and 700,000 and 773,000 kg for PEF and HPP, respectively. This corresponds to an increase between 7- and 8-folds in comparison to the thermal processing. Increasing the production output by 2- to 6-folds reduced the total production costs of nonthermal processing by 50–75 %. A deeper knowledge of the processing costs and environmental impact of nonthermal technologies will afford companies a better understanding of the benefits and limitations of these novel systems.     

High pressure processing of Australian navel orange juices: Sensory analysis and volatile flavor profiling

Navel orange juices subjected to high pressure processing (HPP) and temperature treatment (TT) were stored at 4 and 10 °C for up to 12 weeks to establish the shelf-life of such products. The processed juices and a control juice, stored at − 20 °C, were assessed by a trained sensory panel and a consumer acceptance panel at 0, 1, 2, 4, 8 and 12 weeks or until such time that the juices were considered unfit for consumption. Untreated juice stored at 4 °C was similarly assessed for up to 2 weeks and untreated juice stored at 10 °C was assessed for up to 1 week. The volatile components of corresponding juices were isolated by SPME and the extracts were analyzed by GC–MS. Twenty key aroma compounds were selected for quantification and these data were used to monitor the change in volatile content of the juices during storage. The study showed that the odor and flavor of the HPP juice was acceptable to consumers after storage for 12 weeks at temperatures up to 10 °C. However, only the TT juice stored at 4 °C was acceptable after the same length of storage.

Industrial relevance

Orange juice is a sensitive product subject to a high microbial load that can tolerate only moderate heat treatment without the destruction of the product’s delicate aroma and flavor characteristics. High pressure processing at moderate pressures and storage at refrigeration temperatures have been evaluated as means of maximizing microbial inactivation while maintaining consumer acceptability of the product. The sensory and analytical data presented demonstrate that high pressure processing with refrigeration can extend the shelf-life of orange juice while maintaining consumer acceptability.     

Identification of equivalent processing conditions for pasteurization of strawberry juice by high pressure,ultrasound, and pulsed electric fields processing

The objective of this study was to evaluate the effectiveness of high pressure processing (HPP), ultrasound (US) and pulsed electric fields (PEF) for the pasteurization of strawberry juice (SJ). Acid-adapted Escherichia coli was used to inoculate SJ prior to treatment with HPP, US, and PEF. HPP was applied at several pressures (200–400 MPa) up to 2 min while US (120 μm, 24 kHz) was conducted at 25, 40, and 55 °C up to 10 min in continuous pulsing mode. In order to avoid excessive use of SJ, PEF was performed using a model solution (MS) basically composed of citric acid (8 g/L), fructose (35 g/L), glucose (35 g/L), Na₂HPO₄ (0.2 M) and NaCl (5%) to simulate the SJ electrical conductivity, pH, and total soluble solid (TSS). A face-centered composite design was conducted for PEF processing at different electric field intensities (EFI) (25–35 kV/cm) and treatment times (5–27 μs). Processing conditions were selected that resulted in 5-log CFU/mL inactivation of E. coli. HPP at 300 MPa for 1 min, and US at 55 °C (thermosonication) for 3 min reduced E. coli in SJ by 5.75 ± 0.52 and 5.69 ± 0.61 log CFU/mL, respectively. PEF treatment at 35 kV/cm, 27 μs treatment time, 350 mL/min flow rate, and 2 μs pulse width in monopolar mode resulted in 5.53 ± 0.00 log reduction of E. coli in MS. Likewise, E. coli population in SJ was also reduced by 5.16 ± 0.15 log after applying the same PEF conditions to SJ. No E. coli was detected in SJ subjected to conventional thermal pasteurization at 72 °C for 15 s. All technologies reduced the natural microbiota below 2 log CFU/mL in terms of the total aerobic bacteria and yeast-mold counts. Thus, this study identified the equivalent conditions for the SJ pasteurization by three nonthermal processing technologies.Industrial relevanceConsumers have an increasing interest towards fresh-like food products with desirable nutritional and sensorial attributes. High pressure, ultrasound and pulsed electric field are three relevant novel nonthermal technologies as alternatives to conventional thermal treatments. This study identified the processing conditions of these three nonthermal technologies for the pasteurization of strawberry juice based on equivalent inactivation of acid-adapted E. coli. From an industrial point of view, the established processing conditions are useful references for the development of novel berry juices. In addition to microbiological safety, this study on equivalent processing allows direct efficacy and quality comparisons of a given juice pasteurized by the three nonthermal technologies under consideration.     

SHELF-LIFE EVALUATIONS OF LIQUID FOODS TREATED BY PILOT PLANT PULSED ELECTRIC FIELD SYSTEM

There is a pressing need to validate the shelf-life extension of Pulsed Electric Field (PEF) treated foods. This study was designed to evaluate the shelf-lives of cranberry juice and chocolate milk as a function of PEF and the interaction of PEF+heat treatments. Cranberry juice was exposed to PEF and PEF+heat (60C), and chocolate milk to PEF+heat (105 and 112C). Microbial analysis and color measurement were performed on untreated and treated cranberry juice and chocolate milk aseptically packaged and stored at 4, 22, and 37 C for 197 and 119 days, respectively. Microbial analysis of cranberry juices demonstrated that the shelf-life of PEF and PEF+heat treated juices stored at 22 and 37 C increased significantly during 197 days (p<0.05). The shelf-life of chocolate milk treated by PEF+105C and PEF+112C increased significantly at all storage temperatures (p<0.05). The PEF nor PEF+heat treatments did not result in any significant differences in color retention of either cranberry juice or chocolate milk (p>0.05). This study presented that PEF and PEF+heat treatments were very effective to increase shelf-lives of cranberry juice and chocolate milk.     

Evaluation of Microbial Stability,Bioactive Compounds,Physicochemical Properties,and Consumer Acceptance of Pomegranate Juice Processed in a Commercial Scale Pulsed Electric Field System

This paper investigated the feasibility for pasteurizing raw (100 %) pomegranate juice in a commercial scale pulsed electric field (PEF) processing system. The juice was processed at 35 and 38 kV/cm for 281 μs at 55 °C with a flow rate of 100 L/h. Effect of PEF processing on microbial stability, color, °Brix, pH, sediment, antioxidant activity, total phenolic content, anthocyanin, and sensory properties after the treatments and during storage at 4 °C for 12 weeks were studied and compared to those of thermally processed juice. PEF treatments significantly (p?<?0.05) inhibited the growth of total aerobic bacteria, which remained at <2.5 log colony-forming units (CFU)/ml during the 12-week storage. No yeast and mold were detected (<0.69 log CFU/ml) in the PEF-treated juices during storage up to weeks 10 and 12, which is similar to the thermally processed juice. There were no significant differences in pH and °Brix values between the PEF processed juice and unprocessed juice. PEF processing did not alter the contents of total phenolics and anthocyanin as compared to unprocessed juice. PEF processing had significantly (p?<?0.05) less impact on the color of pomegranate juice than thermal processing. PEF-treated juice had the same consumer satisfaction scores as the unprocessed juice, which were significantly (p?<?0.05) higher than thermally processed juice samples. There was no significant difference between the two PEF treatments in all results. This study demonstrated that PEF technology extended microbial shelf-life and preserved the major quality and nutritional characteristics of pomegranate juice, and hence, is technically feasible for commercialization in the juice industry.     

超高压处理对果汁品质影响的研究进展

超高压处理（High-Pressure Processing,HPP）在保证果汁安全的前提下,能够使果汁的色香味更接近鲜榨果汁,因而受到人们的关注。本文通过综述HPP在不同果汁中的应用案例来分析总结HPP对果汁品质的影响,发现HPP对糖度、酸度、pH等理化指标几乎没有影响;对大部分的一般营养成分和部分功能活性成分（如多酚、类胡萝卜素及糖等）的影响较小;对果汁感官品质（如色泽、状态、香气等）虽有一定的影响,但可以更好地保持果汁特征香气和青鲜香气。值得注意的是,HPP对酶的灭活能力有限,可通过改变各种酶的活力而间接地影响果汁各方面的品质。与热杀菌相比,HPP能更好地保持果汁原有的品质。此外,HPP对不同种类果汁的影响不尽相同,所以在选择加工参数时,需要针对不同的果汁通过试验确定最优的加工方案。     

ENZYME INACTIVATION ON APPLE JUICE TREATED BY ULTRAPASTEURIZATION AND PULSED ELECTRIC FIELDS TECHNOLOGY

Apple juice was pasteurized by an ultra-high temperature treatment (UHT) at 115, 125 and 135C for 3 and 5 s, and compared with a high-voltage pulsed electric field treatment (PEF) at ranges between 33 and 42 kV/cm with frequencies of 150, 200, 250 and 300 pulses per second (pps). Enzyme inactivation and physicochemical properties of the treated juices were compared using a nontreated sample as control. The UHT treatment was more efficient in enzyme inactivation, reducing 95% the residual activity of polyphenoloxidase at the maximum temperature and time. However, a PEF treatment at 38.5 kV/cm and 300 pps combined with a temperature of 50C achieved a 70% reduction of residual PFO activity. In terms of quality characteristics as a function of physicochemical properties, color, pH, acidity and soluble solids were all less affected by PEF than by UHT when compared with the untreated juice.

PRACTICAL APPLICATIONS

Apple juice is a popular beverage worldwide and it is consumed nearly as much as orange juice. Consumers prefer fresh-squeezed fruit juices with high nutrient value and fresh-like sensory attributes. Enzymatic browning negatively impacts appearance, nutritive value and flavor of fruit juices. The use of ultra-high temperature processing is efficient in microbial control, as well as in enzyme inactivation. Any thermal processing may, however, decrease the overall quality of the treated juices. Pulsed electric field processing provides a potential alternative to thermal pasteurization of fruit juices.     

PULSED ELECTRIC FIELD INACTIVATION of MICROORGANISMS and PRESERVATION of QUALITY of CRANBERRY JUICE

Cranberry juice was treated either by high voltage pulsed electric field (PEF) at 20 kV/cm and 40 kV/cm for 50 and 150°s, or by thermal treatment at 90C for 90s. Higher field strength and longer treatment time reduced more viable microbial cells. the overall volatile profile of the juice was not affected by PEF treatment but it was affected by thermal treatment. No Significant difference in color was observed between the control and PEF treated samples. the application of 40kV/cm for 150 1ts resulted in no growth of molds and yeasts during storage at 22 and 4C, and no growth of aerobic bacteria during storage at 4C. PEF is an alternative process to thermal pasteurization for cranberry juice.     

Anthocyanins,non-anthocyanin phenolics,tocopherols and antioxidant capacity of açaí juice (Euterpe oleracea) as affected by high pressure processing and thermal pasteurization

We studied the effect of high pressure processing (HPP) (400, 450, 500, and 600 MPa/5 min/20 °C) and thermal pasteurization (85 °C/1 min) on anthocyanins, non-anthocyanin phenolic compounds, tocopherols and antioxidant capacity toward oxygen and nitrogen reactive species of açaí juice. HPP was more effective for the preservation of anthocyanins than thermal pasteurization (up to 40%), probably due to its thermal-sensitivity. A significant increase was observed for the non-anthocyanin compounds' content at 500 MPa, possibly related to cell wall rupture due to the applied pressure. As a result, this sample showed greater antioxidant capacity (ORAC and total phenolic compounds). On the other hand, H₂O₂ scavenging capacity_, tocopherols and vitamin E activity were not affected, whereas scavenging capacity against HOCl and NOC formation was not well correlated with bioactive compounds concentration. Nevertheless, these properties were effectively preserved in HPP treatments. These results indicate that HPP may provide açaí juice with high functional quality.Industrial relevanceAçaí juice (AJ) has been increasingly valued worldwide due to its bioactive compounds and health-promoting effects, however, thermal pasteurization (TP), usually applied to AJ preservation, may cause degradation of these compounds and damage AJ bioactivities. Our results contribute to understanding how the main bioactive compounds and functional properties of AJ are affected by high pressure processing (HPP) and TP. In addition, they represent an important advance in the field of emerging preservation technologies as it indicates optimal high pressure conditions for AJ processing. Ultimately, given that HPP adds values to food products, our results may be used by the food industry to produce new açaí-based formulations with high market value.     

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.     

Evaluation of microbial inactivation and physicochemical properties of pressurized tomato juice during refrigerated storage

Effects of high pressure processing (300-500 MPa/25 °C/10 min) on microbial inactivation and processing qualities of tomato juices during refrigerated storage at 4 °C for 28 days were investigated to compare with those of conventionally thermal processing. Conventionally, thermal processing almost inactivated all the microorganisms and pectolytic enzymes and produced microbially and consistency stable tomato juices; however, they also reduced the color, extractable carotenoids and lycopene and vitamin C compared with fresh juice. During storage, all the pressure processing could improve the extractable carotenoids and lycopene contents compared with fresh juice, and they also retained more vitamin C contents than thermal processing. Although 300- and 400-MPa processing could retain a/b values of tomato juices as fresh juice during storage for 21 and 28 days, 500-MPa processing could improve the color of juices even after storage. Syneresis occurred in the 300- and 400-MPa processing juices by storing for 7 and 14 days; however, viscosity stable juice was produced by 500-MPa processing. Moreover, 400- and 500-MPa processing significantly inactivated microorganisms and the juices were microbially stable during storage. This study demonstrated that 500-MPa processing would be an alternative for conventionally thermal processing for tomato juice with improvement of some processing quality attributes.     

Combinatory Effect of Thermal Treatment and Blending on the Quality of Pomegranate Juices

In the food industry, browning and colour alteration are usually the main problems to solve in red juices. In an attempt to ease complications due to pomegranate juice processing, the combination of thermal treatment, storage at selected temperature and blending of juices was assessed as a novel and combined solution. A pure monovarietal juice, a combination of two widely distinct varietal juices (75 % Mollar de Elche + 25 % Wonderful) and a blend of pomegranate juice plus lemon (75 % + 25 %, respectively) were compared after pasteurization at two different heat treatments (high temperature–short time (HTST) and low temperature–long time (LTLT)). The effect of processing on the bioactive composition and colour parameters was monitored during juice shelf-life at two storage conditions (room and refrigeration temperatures). The reaction kinetics of main phytochemicals and a factorial analysis were also performed in order to achieve comprehensive data on the evolution of juice quality during storage. Results displayed how blending can protect the desirable properties of pomegranate juices better than pure monovarietal juices. Likewise, a high specificity between thermal treatment and kind of juice was found for each considered parameter. HTST exhibited a higher protective role than LTLT for blends of varietal pomegranate juices, whilst LTLT seemed to protect mixtures with lemon much better than HTST. Moreover, the concomitant degradation of anthocyanins and vitamin C and their role in colour variations were exposed. Overall, the array of outcomes might provide a satisfactory solution of colour alteration in pomegranate juices as well as red fruits in general.     

Effect of refrigerated storage on vitamin C and antioxidant activity of orange juice processed by high-pressure or pulsed electric fields with regard to low pasteurization

A better knowledge of the effect of refrigerated storage on the nutritional and antioxidant characteristics of foods processed by emerging technologies with regard to thermal traditional technology is necessary. Thus, freshly squeezed orange juice was processed by high-pressure (HP) (400 MPa/40 °C/1 min), pulsed electric fields (PEF) (35 kV/cm/750 μs) and low pasteurization (LPT) (70 °C/30 s). The stability of vitamin C and antioxidant activity was studied just after treatment and during 40 days of refrigerated storage at 4 °C. The determination of total vitamin C (ascorbic acid plus dehydroascorbic acid) was achieved by HPLC whereas the antioxidant activity was assessed by the measurement of the DPPH• radical scavenging. Just after treatment, all treated orange juices showed a decrease lower than 8% in vitamin C content compared with the untreated one. At the end of refrigerated storage, HP and LPT juices showed similar vitamin C losses (14 and 18%, respectively) in relation to untreated juice, although HP juices maintained better the vitamin C content during more days than LPT juices. Regarding antioxidant activity, after 40 days at 4 °C, differences among treated juices were no significant in terms of antiradical efficiency (AE=1/EC₅₀T_EC50). HP and PEF may be technologies as effective as LPT to retain antioxidant characteristics of orange juice during refrigerated storage.     

Comparing equivalent thermal, high pressure and pulsed electric field processes for mild pasteurization of orange juice: Part II: Impact on specific chemical and biochemical quality parameters

The impact of thermal, high pressure (HP) and pulsed electric field (PEF) processing for mild pasteurization of orange juice was compared on a fair basis, using processing conditions leading to an equivalent degree of microbial inactivation. Examining the effect on specific chemical and biochemical quality parameters directly after treatment and during storage at 4 °C revealed only significant differences in residual enzyme activities. For pectin methylesterase inactivation, none of the treatments was able to cause a complete inactivation, although heat and HP pasteurization were the most effective in limiting the residual activity. Peroxidase was completely inactivated by heat pasteurization and was much less susceptible to HP and PEF. All other quality parameters investigated, including the sugar profile, the organic acid profile, bitter compounds, vitamin C (ascorbic acid and dehydroascorbic acid), the carotenoid profile, furfural and 5-hydroxymethylfurfural, experienced no significantly different impact from the three pasteurization techniques.

Industrial relevance

HP and PEF processing have received important attention during the last years for application as alternatives to traditional thermal pasteurization. For the further implementation of HP and PEF treatment in the food industry, legal approval of such processes is required. Accordingly, an in-depth characterization of products treated by these novel technologies is indispensable. This paper addresses orange juice as a relevant model food product to compare the impact of HP and PEF processing with that of a conventional thermal pasteurization process and to search for significant differences in specific known nutrients, undesired substances and other quality-related aspects of orange juice.     

Impact of Thermal and Pressure-Based Technologies on Carotenoid Retention and Quality Attributes in Tomato Juice

The aim of this study was to investigate the impact of thermal processing (TP) (90 °C, 90 s), high-pressure processing (HPP) (600 MPa, 46 °C, 5 min), and high-pressure homogenization (HPH) (246 MPa, 99 °C, <1 s) on product quality parameters, specifically carotenoid content, and physicochemical attributes of particle size, color, viscosity, total soluble solids, and pH in tomato juice. Unprocessed tomato juice was used as control. The four major species of carotenoids (lycopene, β-carotene, phytoene, and phytofluene) in tomato juice were analyzed by HPLC. The content of total lycopene, all-trans-lycopene, cis-lycopene isomers,  phytoene, and phytofluene, in TP-, HPP-, and HPH-treated tomato juice did not significantly differ from that in unprocessed (control) juice. Significant reduction in β-carotene content was observed after TP treatment but not after HPP and HPH treatments. HPH significantly reduced tomato juice particle volume mean diameter from ～330 μm in control, HPP-, and TP-treated tomato juices to ～17 μm. A concomitant increase in apparent viscosity was observed in HPH-treated juice versus control. HPH-treated juice had increased redness (a*) and yellowness (b*) than that in control and HPP-treated tomato juices. These results indicate that high-pressure-based technologies (HPP and HPH) can preserve carotenoids as well as improve physicochemical properties.     

Comparative study of juice production by pulsed electric field treatment and enzymatic maceration of apple mash

The application of pulsed electric fields (PEF) to apple mash as an alternative to enzymatic mash maceration (EM) was investigated on a pilot plant scale. Chemical composition of the juices obtained by different processes was similar, except for phenolic content and antioxidative capacity, thus proving substantial equivalence of the juices. However, PEF led to an enhanced release of nutritionally valuable phenolics into the juice. Sensory properties of the juices did not significantly differ when PEF pre-treatment was applied. Total juice yield amounting to approx. 85% was not increased by PEF treatment and was irrespective of the different mash pre-treatments, however, juice release was delayed after PEF application (W = 10 kJ/kg), whereas EM enhanced the de-juicing process. In contrast to EM, genuine pectin quality was retained by PEF processing, which allows sustainable pomace utilisation and additional commercial benefit through its commercialisation. Within a storage time of 40 weeks juice composition remained unchanged.     

Processing and analytical characterisation of pulp-enriched cloudy apple juices

Pulp-enriched cloudy apple juices were manufactured from two apple varieties by blending of apple puree with natural cloudy apple juice in order to enrich bioactive secondary plant substances. Finishing of the puree with a 0.6-mm mesh screen and final product homogenisation revealed as the optimum processing technology for the novel 100% fruit beverage. The presence of large particles originating from the puree prevented long-term cloud stability, but due to the proportion of cloud-stable juice a complete phase separation did not occur. Optimal drinkability was achieved at a viscosity of 11.5 mPa s. Polyphenol compositions and concentrations were determined by means of RP-HPLC/PDA. The results ranged from 109 to 610 mg/l. All samples showed the typical polyphenol pattern of apples with dominating hydroxycinnamic acids followed by flavanols and flavonols. The puree addition to the cloudy apple juices increased the polyphenol concentrations by average 100%. Relatively, the highest increase could be observed for dimeric procyanidins. Different technological variants did not affect significantly the polyphenol concentrations. The dietary fibre contents of the pulp-enriched cloudy apple juices ranged from 5.8 to 9.4 g/l.