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.     

Application of osmotic membrane distillation process in red grape juice concentration

The osmotic membrane distillation process was applied in dehydration of red grape juice (Most de Raïm Concentrat Negre) of different concentrations (5–20 °Brix). Experiments were performed using polytetrafluoroethylene (PTFE) hydrophobic membranes of different nominal pore diameter. Red grape juice solution and concentrated calcium chloride solution (50 wt.%) were used as feed and stripping solutions, respectively. The permeate flux, the initial and the final juice concentration, the total phenolic content (TPC) and the antioxidant activity (TEAC) were measured for each single experiment.     

Response surface methodological study on HMF and fluorescent accumulation in red and white grape juices and concentrates

White and red grape juices and their concentrates were subjected to thermal treatments at different temperatures ranging from 50 to 70 °C at different times. 5-Hydroxymethylfurfural (5-HMF) and fluorescence relative index (FLRI) were measured. Response surface methodology (RSM) was applied to determine the effect of temperature and time on the HMF and FLRI formation at the different Brix (bx) degrees. An increase in temperature (from 50 to 70 °C) and time (from 12 to 192 h) for 15°, 45° and 65° Brix degrees was associated with an increase in HMF and FLRI development of white and red grape juices. HMF formation was higher in white grape juice and concentrates than in red ones. Optimum conditions were confirmed and these fitted the experimental data well. Thus, regression equations can be used to estimate HMF and FLRI values at various Brix degrees for white and red grape juices and concentrates.     

Brix degree and sorbitol/xylitol level of authentic pomegranate (Punica granatum) juice

With regard to 45 pomegranate fruits from different regions and several domestic varieties, fruit weight was found to be 137.1–738.2 g, peel share 34.4–73.1%, aril share 26.9–65.6% and fruit juice yield 19.2–48.0%. Brix degree of pomegranate juice samples obtained from the aforementioned fruits changed from 12.2 to 17.8 and was lower than 14.0 in approximately 18% of the samples. Titratable acidity of pomegranate juice samples varied between 2.4 and 30 g/L and the formol number varied between 4.0 and 20.0. The sorbitol/xylitol content ranged between 16 and 423 mg/L, mostly lying between 51 and 200 mg/L with a frequency of 64%. The share of samples containing sorbitol/xylitol higher than 250 g/L is 7%.     

Reverse osmosis concentration of press liquid from orange juice solid wastes: Flux decline mechanisms

Orange juice production produces high amount of solid waste. An alternative for these wastes is their pressing with lime to obtain a press liquor stream and a dried solid for cattle feeding. The press liquor (around 10 °Brix) is traditionally concentrated up to 70 °Brix (citrus molasses) by multiple effect evaporation. In this investigation, reverse osmosis is evaluated as an alternative for press liquor preconcentration. Two synthetic feed solutions were studied, one included pectin in its composition (WP) and the other lacked pectin (WOP) to simulate a previous depectinization of WP. The concentration process was evaluated in terms of some selected parameters (chemical oxygen demand, total soluble solids, total dissolved solids and osmotic pressure). The fouling mechanism as well as the membrane resistance to the permeate pass were assessed. It was found that for later stages of concentration cake filtration was the dominant fouling mechanism while for earlier stages, the mechanism found was the complete pore blocking. The presence of pectin not only maximized the membrane fouling but also led to worse permeate quality.     

Extraction of phenolic compounds from grapes and their pomace using β-cyclodextrin

Use of aqueous cyclodextrins (CD) for recovery of selected bioactive phenolic compounds from grapes and their pomace was evaluated. When α, β and γ forms of CD were compared, β-CD was the most effective in recovering stilbenes, flavonols, and flavan-3-ols from grape pomace. The maximum quantified phenolics were obtained from the powder and the slurry of grape pomace when extracted with 2.5% (w/v) aqueous β-CD solutions at 60 °C for 12–24 h. With β-CD, total quantified phenolics obtained from the dry powder were 123 mg/100 g (DW) while from the slurry, they were 35.8 mg/100 g (FW). Incorporation of β-CD to grape mash prior to pressing for juice enhanced the recovery of phenolics in juice. Incorporation of β-CD was more effective in recovering flavan-3-ols than flavonols. Aqueous CD can effectively be used in recovering phenolics from by-products of fruit processing and therefore for functional foods and nutraceutical applications.     

Behavior of functional compounds during freeze concentration of tofu whey

The liquid waste generated from tofu production, denominated as Tofu Whey (TW), contains important amounts of isoflavones that can be evaluated by various separation techniques. In this work TW was concentrated by falling-film freeze concentration from 1.9 to 15.5 °Brix, up to levels of 208 mg of isoflavones per 100 g solids. The levels of isoflavones, proteins, sugars, calcium and magnesium were determined both in the ice and in the concentrate obtained. It was found by rheological characterization that TW shows a Newtonian behavior at concentrations between 1.9 and 15.5 °Brix with freezing points of −0.6 to −2.7 °C.     

Electronic nose to study postharvest dehydration of wine grapes

Montepulciano grapes were dehydrated at 10 and 20 °C, 45% RH and 1–1.5 m/s of air flow. Samplings were performed at 10%, 20%, 30%, and 40% of weight loss (wl). TSS (total solids content) increased up to 43° and 36° Brix at 20 and 10 °C, respectively, in 27 and 48 days. A straight regression line between M (kg water/kg dry matter) loss and days of dehydration with R² values, equal to 0.97, was found but an angular coefficient of −0.048 and −0.038, respectively at 20 and 10 °C indicated a different rate of weight loss. Volatiles compounds profile changed significantly with the temperature during the dehydration process. Anaerobic metabolites such as ethanol, acetaldehyde, and ethylacetate were much higher at 20 °C than at 10 °C and rose progressively, while at 10 °C, the significant rise was observed between 30% and 40% weight loss. Alcohols and esters prevailed at 20 °C while at 10 °C larger abundances of aldehydes and terpene alcohols are observed. PCA analysis of GC/MS confirmed the volatiles compounds separation between the samples held at 20 and 10 °C. A progressive evolution of the profile is observed for the samples held at 20 °C while those held at 10 °C show a change of volatiles compounds profile only at 40% wl. Loadings analysis show that aldehydes and terpenols are oriented towards the direction of 10 °C samples while alcohols and esters in that of 20 °C samples. The behaviours of GC/MS data were partially corroborated by the data of electronic nose. Electronic nose was able to follow the progressive change of aroma profile at 20 °C while at 10 °C grouped the responses obtained at 10%, 20%, 30% wl all together but at 40% wl, it discriminated the aroma response. This result opens a window on the potential use to monitor commercially the grape dehydration.     

Spray evaporation of liquid foods

‘Spray evaporation’ based on the principle of adiabatic humidification was examined as an evaporation technique for the concentration of two types of representative liquid foods, namely, fruit juice and milk. The concentration of apple juice could be increased from 10.0 to 13.0 °Brix by this technique without application of heat utilizing the humidity potential to an extent of 89%. Employing heated process air during processing increased the amount of water evaporation owing to increased saturation humidity level, enabling higher concentrations to be achieved in apple juice (48 °Brix), reconstituted milk (29 °Brix) and single toned milk (22 °Brix). Feed flow rate had an inverse effect on the final concentration under otherwise similar conditions. Evaporative cooling associated with spray evaporation actually delivered the concentrate at a relatively lower temperature. By manipulating the operating conditions, humidity potential could be utilized to the extent of 55% with heated process air. The spray evaporation technique seemed to have a good potential for the concentration of liquid foods.     

STUDIES ON THE CLARIFICATION AND CONCENTRATION OF BEETROOT JUICE

Studies on the clarification and subsequent concentration of beetroot juice were carried out. The juice was clarified using enzyme, fining agent (FA), centrifugation and ultrafiltration (UF), while reverse osmosis (RO) and thermovacuum evaporation were used for concentration. The juices were concentrated to 23–25°Brix, and the physicochemical characteristics were evaluated at different stages of processing on the basis of clarity, permeate flux, °Brix, acidity, sugars, pigments and CIE L*, a* and b* (lightness, redness and yellowness, respectively) color values. Average permeate flux during RO was found to be highest (36.08 liters per square meter of membrane per hour [L/m²h]) in the case of enzyme treatment, followed by UF juice, and lowest (30.33 L/m ² h) in the case of enzyme and FA treatments. In terms of clarity of concentrate, the highest value was obtained for juices pretreated with enzyme and UF. Pigment content and L*, a* and b* values showed that pigment loss was higher in the case of RO‐concentrated juice pretreated with enzyme. Comparative evaluation in terms of clarity, color and chemical parameters showed that concentrates obtained using both techniques were comparable.     

Changes in bioactive compounds and antioxidant capacity of fresh-cut cashew apple

In this study, ascorbic acid, total polyphenols and proanthocyanidins of fresh-cut cashew apple were quantified. Antioxidant capacity was determined in whole juice and in polyphenols extracts by three methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and ??-carotene bleaching. Effect of cutting and storage for 24 h at 2 °C, 27 °C and 40 °C on these compounds were also evaluated. Cashew apple presented 163 mg of ascorbic acid per 100 g of fresh weight (FW). Soluble and hydrolysable polyphenols contents were 12.79 mg GAE/100 g FW and 18.53 mg GAE/100 g FW and proanthocyanidins were 9.27 mg/100 g FW. Antioxidant capacity of juice and polyphenols extract was high for DPPH method. Storage temperatures affected bioactive compounds on cut cashew apple. The content of ascorbic acid decreased in all temperatures. Proanthocyanidins were more sensitive to 40 °C than to other temperatures. The content of polyphenols and antioxidant capacity of juice by DPPH assay did not change. However, the reducing power was lower in samples kept at high temperatures. A strong positive correlation between ascorbic acid and FRAP (r = 0.99) and a negative correlation between DPPH and FRAP (r = − 0.79) were observed. No correlations were found between polyphenols and antioxidant capacity indicating the importance of phenolic composition in the extracts. The results confirm the importance of temperature and injury on the quality of cashew apple.     

Characterization of juice in fruits of different Chaenomeles species

The juice in fruits of 21 genotypes of Japanese quince (Chaenomeles japonica), 1 genotype of Chinese quince (C. cathayensis), 1 genotype of flowering quince (C. speciosa) and 1 genotype of a hybrid taxon (C. ×superba), representing plant breeding material, was extracted and characterized. The content of juice in the fruits varied between 41% and 52%, on fresh weight basis. The juice was very acidic (pH 2.6 and a titratable acidity of 3.5% calculated as anhydrous citric acid, on average) and transparent (52 NTU, on average), with low density and viscosity. The content of soluble solids was also low (7.1°Brix, on average). Proteins constituted 26 mg/100 ml juice on average, but no soluble polysaccharides were present. A high content of vitamin C (59 mg/100 ml juice, on average) and phenols (284 mg/100 ml juice, on average), beside the high acidity of the juice, suggests that chaenomeles juice may be an interesting raw material as ingredient for the food industry and a source of valuable substances. A principal components analysis separated the Japanese quince genotypes from the other genotypes studied, thus indicating a clear difference in the characteristics and chemical composition of the juice.     

Effect of PEF and heat pasteurization on the physical-chemical characteristics of blended orange and carrot juice

The effect of different Pulsed Electric Fields (PEF) intensities (25 kV/cm and 280 μs, P1; and 25 kV/cm and 330 μs, P2) and conventional HTST treatment (98 °C, 21 s, T) on quality characteristics (pH, °Brix, total acidity, turbidity, hydroxymethylfurfural (HMF), color, microbial flora, pectinmethylesterase (PME) activity, and sensory analysis) of blended orange and carrot juice were investigated. HMF, L* (luminosity) and C* (saturation or chrome) color parameters did not vary with any of the treatments. Total acidity and turbidity were slightly higher after HTST treatment. Sensory characteristics of the PEF-treated juice were more similar to the untreated juice than the HTST-pasteurized juice. Nevertheless, heat pasteurization (98 °C, 21 s) was more efficient in inactivating microbial flora and PME and preventing the growth of microbial flora and reactivation of PME at 2 and 12 °C for 10 weeks. However, the shelf-life of the PEF-treated juice was established as 4 weeks at 2 °C. This appears to be a reasonable shelf-life for this type of foodstuff.     

Effect of postharvest dehydration on the composition of pinot noir grapes (Vitis vinifera L.) and wine

This study was conducted in order to improve our understanding of how phenolics and aroma compounds change in wine grapes during postharvest dehydration. Pinot noir grapes grown in the Willamette Valley of Oregon were harvested at 22.0 and 24.0 °Brix. Grapes harvested at 22.0 °Brix were divided into three equal lots with one lot immediately used for wine production, and the remaining two lots placed inside an air tunnel with an air speed of 1.0–1.8 m s⁻¹, 38% relative humidity and a temperature of 22 °C. The soluble solids content and weight loss were measured daily and wines were made from grapes when they reached 24.8 and 26.7 °Brix. The soluble solids of grapes increased about 1 °Brix per day; therefore, on the third and fourth day the berries reached the desired concentration; weight loss was 14 and 16%, respectively. Results from berry phenolic analysis indicated that per berry anthocyanin amount remained unchanged during dehydration. The composition of proanthocyanidins isolated from berries changed during dehydration. Volatile compounds in wines made from dehydrated grapes contained more terpenes and norisoprenoids (β-ionone, β-damascenone) when compared to wine made from the original fruit. Wines made from increasingly dehydrated grapes tended to resemble the composition and flavour profile of wines made from grapes left on the vine (i.e. with extended ripening). The results of this study suggest that postharvest flavour changes consistent with changes during fruit ripening can occur in grapes when harvested early and allowed to dehydrate under controlled conditions prior to fermentation.     

Inactivation of Saccharomyces cerevisiae in pineapple, grape and cranberry juices under pulsed and continuous thermo-sonication treatments

Pineapple, grape and cranberry juice were thermo-sonicated (24 kHz, 400 W, 120 μm) at 40 °C, 50 °C and 60 °C during 10 min at continuous and pulsed mode. Inactivation of Saccharomyces cerevisiae was tested from 0 to 10 min; color and pH were measured. Survivor’s curves were fitted with Weibull distribution, four parameter model and modified Gompertz equation. The acoustic energy (AE) was also calculated. S. cerevisiae was inactivated in the treatments at 60 °C, with the continuous mode being more effective. Grape juice showed total inactivation (7-log) after 10 min. Results showed that pH and color changed significantly (p < 0.05); ultrasound may promote chemical reactions and extract some components. The modified Gompertz equation showed the best fit. Energy analysis showed that pineapple juice (4287.02 mW/ml) required a higher amount of energy; grape juice showed the lowest value (3112.13 mW/ml). Ultrasound represents a viable option for juice pasteurization.     

反渗透浓缩西番莲汁的控制因素研究

<正> 西番莲汁是一种热敏性果汁,它含有多种挥发性成份和芳香物质,并且含有较丰富的维生素C、B_1、B_2、PP和A。Murray等人用气相色谱法和光谱法鉴定出西番莲汁中有73种挥发性组分,主要由四种酯类—丁酸乙酯、己酸乙酯、丁酸己酯和己酸己酯构成了西番莲汁的95％的芳香成份。西番莲汁在加热浓缩过程中,上述芳香成份和维生素极易受热分解,因     

Quality evaluation of grape juice concentrated by reverse osmosis

The objective of this work was to evaluate the concentration of grape juice by reverse osmosis (RO). Preliminarily, a factorial design was carried out in which the independent variables were transmembrane pressure (40, 50 and 60 bar) and temperature (20, 30 and 40 °C) of the process, and the dependent variables were pH, content of soluble solids, acidity, concentration of phenolic compounds and those of monomeric and total anthocyanins, colour index, colour density, and permeate flux. None of the experiments resulted in significant changes in the juice characteristics. The best process conditions, 60 bar transmembrane pressure and 40 °C, was selected based on the resulting high permeate flux value. Subsequently, a new trial was performed in order to determine whether increasing the temperature from 40 to 50 °C would result in any changes in the juice characteristics. The transmembrane pressure was kept at 60 bar, which was also the maximum value that could be applied by the equipment. Under these conditions, an increase in permeate flux was achieved with no significant difference in the physical or chemical parameters of the product compared to the best condition corresponding to the factorial design. The physical and chemical properties of the concentrated juice increased in proportion to the volumetric concentration factor, indicating the technical feasibility of reverse osmosis for pre-concentrating grape juice.     

Concentration of grape juice: Combined forward osmosis/evaporation versus conventional evaporation

The present study aimed to evaluate the process of forward osmosis (FO) for the concentration of grape juice using NaCl as the osmotic solution facing the thermal evaporation process, commonly used in industry. A combined experiment (FO + evaporation) was also performed to evaluate the potential of FO as a pre-concentration process. FO experiments were performed according to the Box-Behnken design. Some degree of concentration of the grape juice was obtained in all FO experimental runs, and it was observed a strong influence of the parameters studied on the fluxes. In the evaporation experiments, the quality of the final product was affected concerning the content of phenolic compounds, which have undergone significant degradation by heat. In the combined process, grape juice concentration to up to 65.7°Brix could be achieved showing greater retention of quality factors and bioactive compounds, highlighting the advantage of FO and its potential as a pre-concentration step.     

Application of a commercial immunoassay to the direct determination of insecticide imidacloprid in fruit juices

An ELISA was used to directly determine residual imidacloprid in fruit juices. Imidacloprid could be determined by only diluting samples without any pre-treatments such as filtration, centrifugation, and clean-up procedures. The ELISA enabled imidacloprid to accurately determine down to about 5 μg/L in apple and grape juice samples and down to about 20 μg/L in orange juice sample. Recovery and precision of the ELISA were evaluated by spiking fruit juice samples with imidacloprid in the 10–400 μg/L ranges. Coefficients of variation were lower than 20% in all cases, and average recoveries were 94.2%, 113.2%, and 104.2% for apple, grape, and orange juice samples, respectively. No false positive results were found. The results obtained with the proposed ELISA well correlated with the reference HPLC for each fruit juice sample (r > 0.99).     

Pre-bottling use of dehydrated waste grape skins to improve colour,phenolic and aroma composition of red wines

Different dehydrated waste grape skins from the juice industry were added into aged and young red wines as an innovative way of compensating for colour loss before bottling. After addition of grape skins, colour intensity of wines increased a mean 11% and a maximum of 31% with predominance of the red component. Total polyphenols mean increase was 10% with a maximum value of 20%. Analysis of low molecular weight phenolic compounds by HPLC–DAD showed a significant (p < 0.05) content increase of the bioactive compounds gallic acid, (+)-catechin, (−)-epicatechin, and (E)-resveratrol. Anthocyanins content also increased at an average of 50 mg/l. The volatile profile of wines analysed by SBSE–GC–MS was only moderately influenced by the treatments. Mixtures of dehydrated waste grape skins were useful to improve the colour and polyphenol profile of red wines, considering them a useful tool for correcting colour loss before bottling.