Composition of Some Organic and Inorganic Compounds in Reverse Osmosis-Concentrated Citrus Juices

Orange, grapefruit and lemon juices were concentrated over twofold in a pilot scale reverse osmosis (RO) process using a commercially available membrane system. Major sugars, acids, vitamin C, aroma volatiles and over 20 minerals were examined in feed, concentrate and permeate streams. Typically, 15–20 aroma compounds were identified in feed juices and concentrates. Compared with less volatile compounds (e.g., ethyl butyrate, limonene), poorer retention during processing was noted for more volatile molecules (methanol, acetaldehyde, ethanol). °Brix of membrane concentrates were orange (25.3°B), grapefruit (25.1°B) and lemon (22.5°B). Vitamin C was rejected efficiently by the membrane. Mineral analyses showed similar elemental contents in feed and concentrate and insignificant concentration in permeate streams.     

Clarification and concentration of melon juice using membrane processes

Melon juice obtained from fruits discarded by exporters was first clarified by crossflow microfiltration and then concentrated by osmotic evaporation (OE). The resulting clarified melon juice was highly similar to the initial juice, except for insoluble solids and carotenoids, which were concentrated in the retentate. Average permeation flux was relatively high (about 80 L h⁻¹ m⁻²), with continuous extraction of retentate at a volumetric reduction ratio of 3. After concentration of the clarified melon juice to as much as 550 g kg⁻¹ of total soluble solids using a continuous feed-and-bleed procedure of OE, we found that almost the entire composition of the product was preserved. This integrated membrane process permitted two valuable products to be obtained: a clarified concentrate of melon juice that had not undergone any thermal treatment, and a glowing-orange retentate that was enriched in provitamin A.Industrial relevanceThe increasing quality demand for fresh fruits results in an increase in rejected melons. Juice processing could overcome the product losses occurring but thermal sensitivity of melon juice flavour prohibits conventional thermal processing. Interestingly this paper attempts to use membrane processes for microbial stabilisation and concentration. The authors present a novel way of using permeate (clear juice) as well as retentate (pulpy juice). Enzyme activities in the products during and after processing may need some attention prior to industrial application of the process.     

Coupling nanofiltration and osmotic evaporation for the recovery of a natural flavouring concentrate from shrimp cooking juice

A new combination of membrane-based processes was studied in order to produce a natural flavouring concentrate from shrimp cooking juice. The process associates a pre-concentration step by nanofiltration (NF) until a Volume Reduction Ratio (VRR) of 10 and a final concentration by osmotic evaporation (OE). Thanks to NF, the juice was partially concentrated and desalinated, allowing the further OE step to be run in optimal conditions: reduction of the quantity of water to be evaporated and of the production of brine, limitation of the loss of volatile compounds and improvement of sensory acceptability. During OE step run at pilot-scale, a 52% dry matter concentrate was obtained with aroma loss lower than 35%. Products were characterised by sensory and chemical analyses all along the process. With sensorial characteristics matching the expectancies, the concentrate could be incorporated at 2.5% in food preparations.     

Concentration of camu–camu juice by the coupling of reverse osmosis and osmotic evaporation processes

The objective of this work was to evaluate the technical feasibility of coupling two membrane separation processes, reverse osmosis (RO) and osmotic evaporation (OE), in order to concentrate clarified camu–camu juice, focusing on the vitamin C, phenolic compounds and antioxidant activity of the final product. The juice was firstly pre-concentrated by RO, reaching 285 g kg⁻¹ of soluble solids. During this step, the juice’s osmotic pressure showed to be the main factor controlling mass transfer. The juice was then concentrated by OE, reaching 530 g kg⁻¹ of soluble solids. Vitamin C, total phenolics and antioxidant activity levels of 94.6 g ascorbic acid kg⁻¹, 105.2 g galic acid kg⁻¹ and 762 mmol Trolox kg⁻¹, respectively, were achieved in the final product. The use of integrated membrane processes proved to be an interesting alternative to the concentration of thermosensitive juices, reaching concentration levels up to 7 times for camu–camu juice’s bioactive compounds.     

PINEAPPLE JUICE CONCENTRATED BY OSMOTIC EVAPORATION1

Pasteurized pineapple juice was concentrated by osmotic evaporation to produce a 51 d?Brix concentrate that was reconstituted to single strength juice for evaluation. Headspace gas chromatography (HSGC) showed that the concentrate retained an average of 62% of the volatile components present in the initial juice. A sensory panel preferred initial juice over reconstituted concentrate, and noted a decrease in desirable flavor top notes as well as development of some processed flavor in the concentrate. Similar HSGC analysis of four other commercial juice samples showed a wide range of quantitative values for volatile components, with the initial juice being similar to the weakest of these commercial juices. Analysis of concentrated juice extracts permitted identification of additional less‐volatile components not monitored directly by HSGC of the juice. Relatively low levels of these components were also present in the initial juice. Although this nonthermally produced concentrate retains more volatile components than when traditional thermal processing methods are used, addition of aqueous aroma to the concentrate may be required for satisfactory flavor.     

2种浓缩方法对柠檬汁特性影响的比较

采用界面渐进冷冻浓缩法和真空蒸发法分别对柠檬汁进行界面渐进冷冻浓缩和真空蒸发浓缩。通过对 2种浓缩液处理前后柠檬汁香气成分含量的定性定量分析 ,以及柠檬汁色差、Vc含量、电导和 pH值的比较分析 ,证明了冷冻浓缩柠檬汁明显地比真空蒸发浓缩果汁能更好地保持柠檬汁的香气成分、Vc含量和原汁的香气协调性。     

RETENTION OF FRESH ORANGE JUICE FLAVOR AND AROMA IN AN AQUEOUS DISTILLATE FROM VALENCIA ORANGE JUICE1

Freshly squeezed Valencia orange juice, distilled at low temperature and reduced pressure, yielded an aqueous distillate with the necessary balance of volatile flavor and aroma constituents to retain the fresh juice characteristics. Flavor comparisons by an experienced sensory panel determined that orange juice reconstituted by combining the aqueous distillate with the residual juice solids had significantly more fresh juice character than reconstituted commercial frozen concentrated orange juice; commercial not pasteurized single strength orange juice (SSOJ); pasteurized SSOJ, not from concentrate; canned SSOJ, from concentrate; or aseptically packed SSOJ, from concentrate. The panel also found no significant difference in fresh juice characteristics between freshly squeezed orange juice and distillate and residual solids recombined from the same juice sample. Fifty four volatile constituents were identified from the aqueous distillate of freshly squeezed orange juice.     

Aroma components at various stages of litchi juice processing

BACKGROUND: Considering the importance of flavour on the quality of litchi juice, a study was conducted on how processing and operating stages influence the aroma components of clear litchi juice during processing. RESULTS: The aroma fractions isolated by solid‐phase micro‐extraction were analysed by capillary gas chromatography–mass spectrometry. According to statistical analyses, the amount of total and seven characteristic aroma compounds (geraniol, citronellol, phenylethyl alcohol, D ‐limonene, nonanal, geranial and linalool) increased significantly after enzyme hydrolysis, but decreased significantly during the process of enzyme inactivation, ultra‐filtration and sterilisation. CONCLUSION: The aromatic fraction of litchi juice decreased greatly during processing. The major losses in aromatic composition of clear litchi juice were related to the ultra‐filtration and sterilisation processes. With regard to the retention of aroma, an ultra‐filtration membrane with a larger pore size is better than a membrane with a smaller pore size, and a high‐voltage pulsed electric field was better than thermal sterilisation. Copyright © 2009 Society of Chemical Industry     

Evolution of aroma compounds from orange juice stored in polyethylene terephthalate (PET).

The evolution of aroma compounds from orange juice made from concentrate and stored in glass, standard monolayer polyethylene terephthalate (PET 1), multilayer PET (PET 2) and plasma-treated PET (internal carbon coating) (PET 3) was investigated. Bottles were stored at room temperature (20 degrees C) under artificial light. Volatile compounds in orange juice samples and corresponding packaging materials were analysed at zero time and after 2, 3 and 5 months of storage. After 5 months of storage, from 0.2 to 0.3% of the initial amounts of limonene and beta-myrcene in the orange juice had been absorbed by the plastic packaging materials. Statistical analyses showed that the evolution of aroma compounds was strongly correlated to the duration of storage, but not to the type of packaging material. Indeed, whatever the stored orange juice samples, the same evolutions were observed, with a decrease in aldehydes and ketones, esters, aliphatic alcohols, sesquiterpene and monoterpene alcohols, and an increase in two aliphatic and monoterpene alcohols (i.e. furfural and 4-vinylguaicol). The results suggest that the losses of aroma compounds from the juice could be attributed to the high acidity of the matrix, implying acid-catalysed reactions. Finally, PET packaging materials and their corresponding oxygen permeabilities showed no correlation with the loss of aroma compounds.     

超高压处理对猕猴桃汁品质的影响

为了研究超高压处理对猕猴桃汁品质的影响,对新鲜猕猴桃进行200～500MPa超高压处理。结果表明：超高压猕猴桃汁中可溶性固形物、总酸、pH值等指标随压力升高变化不显著,VC及叶绿素含量有少量降低,香气成分中酸类、醛类物质在超高压处理后增加,酯类、醇类物质减少。超高压猕猴桃汁4℃条件下贮藏28d时VC损失21.8%,叶绿素损失40.5%,果汁趋于变质;－18℃条件下贮藏120d时,VC损失14.6%,叶绿素损失20.8%,因此－18℃贮藏条件能较好保持超高压处理后猕猴桃汁的营养物质。     

Recovery of volatile fruit juice aroma compounds by membrane technology: Sweeping gas versus vacuum membrane distillation

The influence of temperature (10–45 °C), feed flow rate (300–500 L/h) and sweeping gas flow rate (1.2–2 m³/h) on the recovery of berry fruit juice aroma compounds by sweeping gas membrane distillation (SGMD) was examined on an aroma model solution and on black currant juice in a lab scale membrane distillation set up. The data were compared to recovery of the aroma compounds by vacuum membrane distillation (VMD). The flux of SGMD increased with an increase in temperature, feed flow rate or sweeping gas flow rate. Increased temperature and feed flow rate also increased the concentration factors (C_permeate/C_feed) of the aroma compounds. At 45 °C the most volatile and hydrophobic aroma compounds obtained the highest concentration factors: 12.1–9.3 (black currant juice) and 17.2–12.8 (model solution). With black currant juice a volume reduction of 13.7% (vol.%) at 45 °C, 400 L/h, resulted in an aroma recovery of 73–84 vol.% for the most volatile compounds. Compared to VMD, the aroma recovery with SGMD was less influenced by the feed flow rate but more influenced by the temperature. Higher fluxes were achieved during concentration by VMD and this reduced the operation time, which in turn reduced the degradation of anthocyanins and polyphenolic compounds in the juice.

Industrial relevance

High temperature evaporation is the most widely used industrial technique for aroma recovery and concentration of juices, but membrane distillation (MD) may provide for gentler aroma stripping and lower energy consumption. This study gives important clues about the fate of berry juice aroma compounds and polyphenols during concentration by MD, and identifies the main factors influencing the aroma recovery efficiency with MD. Both SGMD and VMD are promising techniques for gentle stripping of berry juice aroma compounds and deserve further consideration as alternative techniques for gentle aroma stripping in industrial fruit juice processing.     

Gehalte an stabilen Sauerstoff-Isotopen in Wasser von Apfelsaftkonzentrat als Kriterium für den Nachweis einer Zuckerung

Using a modified method for the determination of the¹⁸O/¹⁶O ratio in water the δ¹⁸O values for authentic apple juice concentrates (70 °Brix) of known origin, for industrially produced invert sugar syrups, for commercial apple juice concentrates, and for spiked apple juice concentrates have been measured. The δ¹⁸O values for the authentic apple juice concentrates were correlated to the δ¹⁸O values of the related pressed (single strenght) apple juices and to the sugar content of the concentrates in °Brix. The results for the samples were compared to and evaluated together with the δ¹³C values for the sugars. Concluding from the results, a minimum value for authentic apple juice concentrate of 0 to 1%., depending on the regional origin of the material, is suggested, while the determination of the δ¹⁸O value of apple juice concentrate is preferably used in addition to the already well known methods on the basis of stable isotope measurement.     

Characterisation of volatile aroma compounds of orange juices by three dynamic and static headspace gas chromatography techniques

The influence of collection of volatiles by different headspace sampling techniques was compared for different orange juices, including one fresh unpasteurised, two reconstituted commercial juices and one juice freshly hand extracted in the laboratory. Dynamic headspace sampling from stirred juice samples (DH + S) and notably by purge and trap (PT) sampling gave the highest levels of analysed volatiles, but the composition of the isolated volatiles from the different types of juices varied depending on the volatiles collection method. Aroma sampling by dynamic headspace method without stirring (DH) gave results that reflected the equilibrium aroma composition as determined by static headspace better than that obtained by PT sampling. Totally, 67 aroma constituents were identified among all the orange juices. The largest amount of volatiles was isolated from the fresh commercial, unpasteurised juice, followed by the two reconstituted juices and the hand extracted juice. Limonene was the major constituent of all commercial juices comprising 72–93% of the total peak area of isolated volatiles, meanwhile its amount in the freshly hand extracted juices ranged from 25 to 62% depending on the method of isolation. Qualitatively, the aroma profiles of the freshly extracted oranges and the fresh, commercial unpasteurised juice were described by 62 and 55 aroma compounds, respectively, which included large proportions of esters and aldehydes. Only 41 and 34 aroma compounds, mainly terpenes, were identified in the reconstituted orange juices.     

Quantitative bioactive compounds assessment and their relative contribution to the antioxidant capacity of commercial orange juices

Dietary recommendations for healthy eating include the consumption of fruit juices whose health effects are ascribed, in part, to carotenoids, phenolic compounds and vitamin C. These bioactive compounds have been implicated in the reduction of degenerative human diseases, mainly due to their antioxidant potential. Orange juice is characterized by substantial accumulation (apart from ascorbic acid) of flavonoids and carotenoids. Commercial orange juice is the main human dietary source of antioxidant compounds in developed countries. The qualitative and quantitative determination of carotenoid, flavonoid and vitamin C content of Spanish commercial orange juices was achieved by high‐performance liquid chromatography. The health‐related properties of bioactive compounds contained in orange juice are based on their antioxidant activity. The antioxidant capacity of these juices was assessed by 2,2‐diphenyl‐1‐picrylhydrazyl stable radical scavenging and was compared with a freshly squeezed orange juice. In addition, the relative contribution of the different bioactive compounds to the antioxidant activity of orange juices was calculated. Total vitamin C was found to be the major contributor to the antioxidant potential of the orange juices studied, followed by flavonoid and carotenoid compounds. Ascorbic acid, total vitamin C and β‐cryptoxanthin content correlated positively with the free‐radical scavenging parameters. No significant differences, in terms of antioxidant capacity, were found between commercial traditional pasteurized orange juices and freshly squeezed orange juice. Copyright © 2003 Society of Chemical Industry     

Influence of CMC‐ and guar gum‐based silver nanoparticle coatings combined with low temperature on major aroma volatile components and the sensory quality of kinnow (Citrus reticulata)

Aroma profile and organoleptic quality of CMC‐ and guar gum‐based silver nanoparticle‐coated kinnow (Citrus reticulata cv. Blanco) was evaluated for 120 days at 4 °C and 10 °C, 85–95% relative humidity. Loss in three major aroma‐active volatile compounds (limonene, linalool and γ‐terpinene) was determined after every 15 days by GC‐MS. Sensory quality of coated and uncoated fruit stored at 10 °C was declined during storage. Twenty five volatile aroma compounds were identified in fresh kinnow juice. Guar gum‐Ag coatings and 4 °C storage has significantly reduced losses of limonene, linalool and γ‐terpinene contents from 91 to 23%, 99 to 10% and 97 to 29% respectively as compared to uncoated fruit stored at 10 °C. Study suggests that CMC‐ and guar gum‐based silver nanoparticle‐coated kinnow stored at 4 °C has preserved the fruit aroma and sensory quality for 120 days.     

Influence of Refractance Window evaporation on quality of juices from small fruits

A new type of evaporator (Refractance Window^® (RW) evaporator) has been developed that operates at atmospheric conditions and uses thermal energy from hot water to concentrate foods. The influence of product temperature and dissolved solids on vitamin C in blueberry juice and color of cranberry juice was evaluated in this new evaporation method in comparison with conventional falling film multi-effect evaporators. During RW evaporation, vitamin C in blueberry juice was reduced by 32% and 48% with product temperatures at 55.5 and 59.0 °C, respectively. Concentration of the same juice from single strength to 65°Brix in an industrial falling film evaporator operating at 68 °C reduced vitamin C content by 70.1%. The color of cranberry juice, defined by the hue angle, was not significantly different between the concentrates from the RW and falling film evaporation methods. Further investigation is needed for complete insights into the mechanism for vitamin C loss in RW evaporation.     

Freeze Concentration of Pineapple Juice

Juice, extracted from fresh Costa Rican pineapples using a commercial extractor, was adjusted by finishing and centrifugation to two pulp levels, 12% and 2% by volume. Physical, chemical and sensory differences were measured in heat stabilized single strength juices, evaporator concentrated, and freeze-concentrated juices. Results indicated no significant differences between samples for Brix, % acid, total hexose, vitamin C, browning index, color, viscosity. Pulp content was lower in both freeze- and evaporator-concentrated samples. Significant (P < 0.01) flavor differences were detected between freeze-and evaporator-concentrated juices. Juices were ranked according to highest degree of fresh fruit taste as follows: (1) high pulp single strength, (2) freeze concentrate high pulp, and (3) evaporator concentrate high pulp. Flavor of reconstituted freeze-concentrated juice was comparable to single strength juice and preferable to evaporator concentrate.     

Development of a headspace trap HRGC/MS method for the assessment of the relevance of certain aroma compounds on the sensorial characteristics of commercial apple juice

A reliable and simple method was developed for the completely automatised analysis of apple juice aroma compounds. In total 26 flavour compounds could be measured by headspace trap gas chromatography/mass spectrometry (GC/MS). We used the method to analyse 85 commercially available apple juices, of which 67 apple juices were not from concentrate. Our results show that apple juices not from concentrate are mainly characterised by flavour compounds responsible for fruity, ripe, and sweet aroma impressions, such as 1-butanol, 2-methyl-1-butanol, ethylbutyrate, and ethyl-2-methylbutyrate. On the contrary, apple juices made from concentrate were dominated by acetaldehyde, E-2-hexenal, 3-methyl-1-butanol, ethyl acetate, and hexanal, which are mainly responsible for sensory impressions, such as ‘green, fresh, estery’. According to our data, neither of the single compounds nor indexes calculated thereof as suggested by some authors could be used for the reliable assessment of apple juice quality. Thus, these results suggest that sensory evaluation remains the ultimate mean to reliably assess apple juice quality.     

Volatile compounds and changes in flavour‐related enzymes during cold storage of high‐intensity pulsed electric field‐ and heat‐processed tomato juices

BACKGROUND: The effects of high‐intensity pulsed electric field (HIPEF) processing (35 kV cm^?1 for 1500 µs, using 4 µs bipolar pulses at 100 Hz) on the production of volatile compounds and flavour‐related enzymes in tomato juice were investigated and compared with those of thermal processing (90 °C for 30 or 60 s). RESULTS: Tomato juice treated by HIPEF showed lower residual lipoxygenase (LOX) activity (70.2%) than juice heated at 90 °C for 60 s (80.1%) or 30 s (93.2%). In contrast, hydroperoxide lyase (HPL) was almost completely inactivated when the juice was subjected to 90 °C for 60 s, whereas roughly 50% of the control tomato juice was depleted after HIPEF treatment or thermal processing at 90 °C for 30 s. A slight decrease was observed in the initial LOX activity of treated and untreated samples during storage, whereas initial HPL activity was strongly affected over time. CONCLUSION: HIPEF‐treated juice exhibited higher levels of compounds contributing to tomato aroma than untreated and heat‐treated juices throughout storage. Thus HIPEF processing can preserve flavour quality and stability of tomato juice compared with conventional thermal treatments. Copyright © 2010 Society of Chemical Industry