Juice components and antioxidant capacity of four Tunisian Citrus varieties

BACKGROUND: Juices from four Citrus species of Tunisia were investigated mainly for quality parameters and antioxidant capacity. RESULTS: Citrus reticulata (mandarin) juice had the highest content of total flavonoids (85.33 mg CE L^?1). The latter also occurred in high quantity (82.01 mg CE L^?1) in Citrus lemon (lemon) juice which was also marked by its richness in total aroma (70.16 µg mL^?1) and in total fatty acids (48.10 µg mL^?1). Mandarin and lemon juices had the highest antioxidant activity, as determined b the β‐carotene bleaching assay (26.67% and 22.67%, respectively). Citrus aurantium (bitter orange) juice was characterised by the highest content of total polyphenols (784.67 mg GAE L^?1) and by the greatest inhibition of DPPH (96.10%). Citrus sinensis (blood orange) juice was only marked by the high quantity of ascorbic acid (36.90 mg mL^?1). GC/MS analysis of juice aroma showed the predominance of limonene (48.85–69.59%) in mandarin and in bitter and blood oranges, but of camphene (89.05%) in lemon. GC analysis of juice fatty acids revealed their richness in oleic acid (23.13–39.52%). HPLC analysis of juice phenolics indicated the predominance of phenolic acids (73.13–86.40%). CONCLUSION: The Citrus species used in this study were considered valuable varieties from the point of view of antioxidant capacity and nutrition. Copyright © 2010 Society of Chemical Industry     

Influence of processing steps and fruit maturity on volatile concentrations in juices from clementine, mandarin, and their hybrids

During growth, ripening, and post-harvest, the quality of fruits can be modified by various stresses. Ample maturation allows prolonged storage and increases the quality of citrus fruits. The eight major volatile compounds in fresh juices from mandarin (Citrus reticulata Blanco var. Willow Leaf), clementine (Citrus reticulata × Citrus sinensis var. Commune), and their six cross-pollinated hybrids were quantified by gas chromatography. Mandarin juice contained the highest volatile concentration (2177.6 ± 110.6 mg L⁻¹), whereas the total aromatic compounds of the hybrid and clementine juices were lower (1060.6 ± 81.6–1724.2 ± 138.5 mg L⁻¹ and 864.8 ± 67.8 mg L⁻¹, respectively). Limonene was the major compound (667.3 ± 53.7–1259.9 ± 98.4 mg L⁻¹) in all juices. We observed significant differences according to the process of juice extraction used (with and without peel). The relative volatile concentration was higher when the juice was extracted with peel, and the juicing process induced differences in the relative volatile concentrations of between 20 and 40%. The levels of volatile compounds in the juice changed according to the degree of fruit maturity. The concentrations of the eight major juice components increased during ripening and until the commercial maturity stage when the juice was obtained from peeled fruits, whereas their concentrations increased until the post-maturation stage when the juices were produced from whole fruits. These two factors determined the contributions of these compounds to the characteristic aromas of Citrus juices.     

Volatile composition of hybrids Citrus juices by headspace solid-phase micro extraction/gas chromatography/mass spectrometry

The volatile compounds of Citrus juices have been extracted by headspace solid-phase microextraction (HS-SPME) and analysed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). This work deals with the analysis of 65 cross pollinated hybrid fruits and their parents: mandarin (Citrus reticulata Blanco var. Willow Leaf) and clementine (Citrus reticulata × Citrus sinensis var. Commune). Among the 44 components identified which accounted for 90.2 to 99.8% of the volatile fraction, limonene (56.8–93.3%) and γ-terpinene (0.1–36.4%) were the major components in all samples. The clementine juice was characterised by the pre-eminence of limonene (90.0%) and a minor amount of γ-terpinene (1.2%) while the mandarin juice exhibited high amount of limonene (66.3%) and γ-terpinene (21.1%). All hybrid juices showed qualitatively similar composition but differing in the quantitative profile of the couple limonene/γ-terpinene. The principal component analysis (PCA) and the discriminant analysis indicated that hybrids samples were symmetrically distributed around the both parents. If some studies were found in the literature about mandarin juice, to our knowledge, this work is the first study on the volatile compounds of clementine juice and a large amount of hybrids.     

Limonene, linalool, α-terpineol, and terpinen-4-ol as quality control parameters in mandarin juice processing

Consumers demand commercial citrus juices resembling fresh juices; however, citrus juice elaboration is quite delicate due to the formation of off-flavors during heat treatment and storage. Four volatile compounds, d-limonene, linalool, α-terpineol, and terpinen-4-ol were extracted using the dynamic headspace technique and were identified and quantified by GC-MS in mandarin juices from two Spanish varieties, Fortuna and Clemenules. Our results clearly demonstrated that both the pasteurization and storage steps significantly affected concentrations of these four aroma compounds. Formation of off-flavors components, α-terpineol and terpinen-4-ol, and simultaneous decomposition of d-limonene and linalool were observed in mandarin juices. Therefore, measurements of the stability of d-limonene and linalool, and formation of α-terpineol and terpinen-4-ol will help mandarin juice producers in analyzing the quality of their products.     

An Integrated Approach to Mandarin Processing: Food Safety and Nutritional Quality,Consumer Preference,and Nutrient Bioaccessibility

Mandarins are a member of the Citrus genus and are the focus of growing commercial interest, with satsuma mandarins (Citrus unshiu) and the common mandarin (Citrus reticulata Blanco) being the most important mandarin varieties. The possible health benefits and functional properties of those fruits are often associated with the antioxidative function of vitamin C, carotenoids, and phenolic compounds. While most mandarins are consumed fresh, many are processed into juices (mostly cloudy), usually via thermal processing which can lead to the creation of off‐flavors and may diminish nutritional quality. The aim of this review is to summarize the most significant and recent information on the safety, sensorial properties, and nutritional benefits of mandarins and their processing into juice. The article also discusses recent information regarding the bioaccessibility of valuable, mandarin specific, compounds.     

Effect of technological processes and storage on flavonoids content and total, cumulative fast-kinetics and cumulative slow-kinetics antiradical activities of citrus juices

Juices from the mandarin Clemenules (Citrus clementina Hort. ex Tan.), the tangor Ortanique (Citrus reticulata Blanco × Citrus sinensis Osb.) and the sweet orange Valencia Late (Citrus sinensis) have been industrially squeezed, pasteurized, concentrated and stored under refrigeration (4 °C) and at room temperature (20 °C). After each process, the flavanone-7-O-glycosides (FGs) and fully methoxylated flavones (FMFs) contents as well as total, cumulative fast-kinetics and cumulative slow-kinetics antiradical activities were determined and compared with those from the corresponding fresh hand-squeezed juices. Neither industrial-squeezing, nor pasteurization or concentration significantly affected FGs and FMFs contents and antiradical activities of assayed juices. Storage caused a slight decrease of the FMFs contents but a significant reduction of both soluble hesperidin contents and cumulative fast-kinetics antiradical activities in all assayed juices. These decreases were dependent on storage temperature. Characteristic values of the varietal characterization parameters, which are derived from the FMFs contents and antiradical activities of fresh hand-squeezed juices, held valid for industrially squeezed, pasteurized and concentrated juices. After storage, however, only the FMFs-derived varietal characterization parameters and cumulative slow-kinetics antiradical activity remained valid for the resulting juices.     

Flavone-di-C-glycosides in citrus juices from Southern Italy

6,8-Di-C-glucopyranosylapigenin and 6,8-di-C-glucopyranosyldiosmetin were detected by HPLC–DAD–ESI–MS–MS in a variety of Southern Italian Citrus juices (orange, lemon, bergamot, citron, mandarin, clementine). In some juices, the amounts of C-glycosides detected were significant. 6,8-Di-C-glucopyranosylapigenin is characteristic of orange juice, while 6,8-di-C-glucopyranosyldiosmetin is the most important C-glycoside in lemon and citron juice. In bergamot juice the concentrations of 6,8-di-C-glucopyranosylapigenin and 6,8-di-C-glucopyranosyldiosmetin are similar. Clementine juice is distinctive as the amounts of both C-glycosides present are negligible.     

Total,cumulative fast-kinetics and cumulative slow-kinetics antiradical activities of juices from clementine (<Emphasis Type="Italic">Citrus clementina</Emphasis>), clementine-hybrids and satsuma (<Emphasis Type="Italic">Citrus unshiu</Emphasis>) cultivars and their utility as discriminant variables

Mandarin juices from three pure clementine (Citrus clementina Hort. ex Tan.) cultivars: Clemenules, Hernandine and Marisol, two clementine-hybrid cultivars: Nova (clementine×tangelo Orlando) and Fortune (clementine× mandarin Dancy), one mandarin-hybrid cultivar: Ortanique (mandarin×orange) and one satsuma (Citrus unshiu Marc) cultivar: Clauselline have been analysed for determination of total, cumulative fast-kinetics and cumulative slow-kinetics antiradical activities. Total antiradical activity followed the order: pure clementine and Nova> Ortanique>Fortune and Clauselline. Cumulative fast-kinetics antiradical activity was the major contributor to total antiradical activity, accounting for about 87% as average. Ascorbic acid content was the major contributor to cumulative fast-kinetics antiradical activity, accounting for about 93.5% as average. A weak correlation (r ²=0.151) between total flavanone-7-O-glycosides (FGs, Narirutin, Hesperidin and Didymin) content and cumulative slow-kinetics antiradical activity was observed. However, ascorbic acid and total FGs contents showed a significant negative correlation (r ²=0.658). By using the cumulative fast-kinetics and slow-kinetics antiradical activities as variables, all the assayed juices were significantly discriminated (<0.05) by statistical multivariate discriminant analysis.     

Assessment of the Variations in Selected Industrially Desirable Morphological and Biochemical Traits of Eleven Citrus Species in Sri Lanka

The fruits with nutraceutical and medicinal values are having a greater significance in modern food industry. Out of many fruit tree bearing genera, the genus Citrus is extremely important in this regard. It contains well known species such as orange, lime, mandarin, lemon and many other underutilized species. The nutritive value of Citrus is given by many bioactive compounds present in the fruits such as alkaloids, tannins, phenols and saponins. In Sri Lanka, the available Citrus germplasm is not characterized in detail. Especially underutilized Citrus species are yet to receive a proper taxonomic identity. Therefore in the present study we report some of the important morphological and biochemical traits of eleven Citrus species. The fruit size traits; weight, height and width were very highly variable among the studied genotypes and positively correlated to each other (P<0.05). However, juice volume was not highly correlated with the other fruit size traits. The juice volume per unit fruit weight can be given as a better indicator for the selection of these species for industrial applications. Pummelo, a popular edible Citrus fruit, showed the lowest volume to weight ratio of 0.06. The size of the endocarp cells (i.e. juice sacks) was also very highly variable among genotypes / species studied. The brix value, a parameter of total soluble solids, was highest in Sidaran fruits (8.07%) and lowest in cooking types such as lemon and lime (3.27% and 3.76% respectively). Similarly the ascorbic acid concentration was also lowest in lime and lemon (1.9 and 1.5 mM respectively). The sweet orange cultivar Sisila (5.9 mM) and Pummelo (6.9 mM) had the highest ascorbic acid concentrations. The results reported here are very useful to select these genotypes / species for potential industrial applications, future genetic and breeding studies and to further characterize at molecular level to establish an accurate taxonomic scheme for Sri Lankan Citrus germplasm which will be the next focus of our group.     

Elucidation of key aroma enhancement in cloudy lemon juices by the addition of peel oil using GC–MS-Olfactometry

Volatile substances play a crucial role in the consumer preference of lemon juices. The effects of heat treatment and addition of lemon peel oil to lemon juice (Citrus limon Burm. cv. Kutdiken) on the aroma compounds were elucidated for the first time. Total phenolic, antioxidant activity, acidity, pH and colour properties were also studied. Results revealed that the aroma of the juice samples comprised mostly the terpene compounds. Limonene, γ-terpinene, β-pinene and α-pinene were the influential terpenes responsible for the distinctive odour of the lemon juice. The addition of the lemon peel oil increased the amounts of the aroma and aroma-active compounds. Besides, the heat treatment had a positive effect on the total phenolics and the antioxidant activity but it caused significant reduction of the aroma compounds. Sensory analysis revealed that the most preferred sample was the juice with lemon peel oil added after pasteurisation.     

Flavonoids and furocoumarins distribution of unripe chinotto (<Emphasis Type="Italic">Citrus</Emphasis> × <Emphasis Type="Italic">myrtifolia Rafinesque</Emphasis>) fruit: beverage processing homogenate and juice characterization

The present study reports for the first time qualitative and quantitative data about flavonoids and furocoumarins distribution of unripe Citrus × myrtifolia Rafinesque homogenate, used as ingredient of the popular soft drink Chinotto. No data are available in literature about the chemical characterization of flavonoids and furocoumarins of the chinotto homogenate used to produce the industrial extract. Samples for analysis were therefore processed to better reproduce the crude materials used to obtain industrial chinotto extract: the whole fruits were cut in half, seeds removed, softly squeezed discarding part of the juice, and homogenized in small pieces. The polyphenolics separation was made by HPLC–PDA detector coupled to ESI/MS/MS in positive and negative mode. It has allowed the identification and relative quantification of 16 compounds, among which the flavone-C-glycoside lucenin-2, the 3-hydroxy-3-methylglutaryl flavanone glycoside melitidin and five polymethoxylated flavones have been detected for the first time in Citrus × myrtifolia. The flavonoids and furocoumarins distribution was compared with one of the Citrus × myrtifolia juice, and the antioxidant activity of both samples was assessed by ORAC (Oxygen Radical Absorbance Capacity)-fluorescein assay.     

Viscosity of tangerine and lemon juices as a function of temperature and concentration

Viscosities of two fruit (lemon and tangerine) juices have been measured with a capillary flow technique. Measurements were made in the temperature range from 303 to 393 K. The range of concentration was between 15 and 40 °Brix for tangerine juice and between 17 and 45 °Brix for the lemon juice. The total uncertainty of viscosity and temperature measurements was estimated to be <0.5% at low concentrations and up to 1.5% at high concentrations and 0.025 K, respectively. The effect of temperature and concentration on viscosity of tangerine and lemon juices was study. The measured values of the viscosity were used to calculate the temperature, (? ln η/?T)_x, and concentration, (? ln η/?x)_T, coefficients for each juice. The Arrhenius type correlation equations for viscosity were used to represent the temperature dependence of viscosity. The values of the Arrhenius equation parameters (flow activation energy, E_a, and η_∞) were calculated for the measured viscosities of tangerine and lemon juices as a function of concentration. Different theoretical models for the viscosity of fruit juices were stringently tested with new accurate measurements on tangerine and lemon juices. The predictive capability of the various models was studied. The concentration and temperature dependence behavior of the viscosity of tangerine and lemon juices are discussed in light of the various theoretical models for viscosity of fruit juices. The applicability and predictive capability of the models used previously for aqueous solutions to represent the effect of temperature and concentration on viscosity of fruit juices was also studied. New model was developed to represent the combined effect of temperature and concentration on the viscosity of the juices. The average absolute deviation between measured and calculated values from this correlation equation for the viscosity was 0.8% and 2.1% for tangerine and lemon juices, respectively.     

Effect of high hydrostatic pressure and high-pressure homogenisation on <Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> inactivation kinetics and quality parameters of mandarin juice

The inactivation kinetics of Lactobacillus plantarum in a mandarin juice treated by thermal treatment (45–90 °C), high-pressure homogenisation (HPH) (30–120 MPa at 15 and 30 °C) and high-pressure processing (HPP) (150–450 MPa at 15, 30 and 45 °C) were fitted to different Weibullian equations. A synergic effect between pressure and temperature was observed in HPH and HPP treatments achieving 2.38 log cycles after 120 MPa at 30 °C for 10 s (final T of 45 °C) and 6.12 log cycles after 400 MPa at 45 °C for 1 min (final T of 60 °C), respectively. A combined treatment of 100 MPa at 15 °C for 10 s and 300 MPa at 15–30 °C for 1 min in HPH and HPP, respectively, was needed to the first logarithm microbial population decline. Weibull model accurately predicted microorganism inactivation kinetics after HPH and HPP processing when displaying single shoulder or tail in the survivor curves, whereas when a more complex trend was observed after thermal treatment, the double-Weibull equation was found more appropriate to explain such behaviour. Equivalent treatments that achieved the same degree of microbial inactivation (77 °C–10 s in thermal processing, 120 MPa–10 s at 30 °C in HPH processing and 375 MPa–1 min at 30 °C in HPP) were selected to study the effects on quality parameters. The application of dynamic pressure led to a decrease in sedimentable pulp, transmittance and juice redness, thus stabilising the opaqueness and cloudiness of mandarin juice. Pectin methyl esterase (PME) was found to be highly baroresistant to static and dynamic pressure. Carotenoid content remained unaffected by any treatment. This study shows the potential of high-pressure homogenisation as an alternative for fruit-juice pasteurisation.     

Ohmic Heating of Lemon and Grapefruit Juices Under Vacuum Pressure— Comparison of Electrical Conductivity and Heating Rate

Ohmic heating fundamentally depends on electrical conductivity. In this study, grapefruit and lemon juices were ohmically heated under vacuum conditions. The electrical conductivity was measured at voltage gradients (10, 20, and 30 V/cm) and vacuum pressure (0 [atmospheric pressure], ?30, and ?60 kPa) for four temperature ranges (30, 40, 50, and 60 °C), meanwhile the heating rate was also reported at the same level of pressure and voltage gradient. The electrical conductivity and heating rate considerably vary by voltage gradient relative to pressure. Grapefruit had considerably lower electrical conductivity (about 20%) relative to lemon juice for the same pressure–voltage gradient treatment, while the percent reduction of heating rate (grapefruit relative to lemon) varied from 19 to 32%. The multivariate linear regression of electrical conductivity, including temperature and voltage, was found to be a more suitable model. pH assessments showed that pressure significantly affected the pH of grapefruit and lemon juices (P < 0.01). The combination of different treatments, which created a shorter residence time, caused a greater decrease in pH.     

Changes in orange juice color by addition of mandarin juice

The most natural way of improving the color of orange juices is by adding other juices, which provide a more intense coloration. The US legislation allows the addition of up to 10% of mandarin juice to the orange juice to improve its color. The first objective of this study was to compare the color characteristics of juices from 11 mandarin cultivars, currently being grown in Spain. Experimental results proved that only the green-red coordinate, a*, of the orange juices can be improved by adding mandarin juice. The mandarin cultivar that provided a juice with the highest values of a* was Clemenules. Once this selection was made, the effects of adding mandarin juice at different ratios, up to 10%, on the color characteristics of the orange juice were studied. Values of the a* coordinate went from 5.50 for the pure orange juice up to 6.29 for the mixture of 90% orange juice plus 10% of mandarin juice. Finally, hedonic tests proved that regular juice consumers preferred the color of mandarin juice to that of orange juice and that they liked better the color of the juice mixture containing 10% mandarin juice than that containing 3% mandarin juice.     

Effects of tangential microfiltration and pasteurisation on the rheological,microbiological, physico‐chemical and sensory characteristics of sugar cane juice

The aim of this study was to determine the physico‐chemical, microbiological, rheological and sensory characteristics of sugar cane juice with passion fruit pulp (5% w/w) added and which had been submitted to microfiltration and pasteurisation (90 °C/30 s; 95 °C/30 s) processes. The results showed that the juices obtained after the microfiltration and pasteurisation processes had low microbial counts. The microfiltered juice showed a reduction in the soluble solids, acidity and vitamin C content (P = 0.05), while the pasteurised juice showed no change in these parameters (P > 0.05) in relation to the natural sugar cane juice, with the exception of vitamin C, which was not detected after the thermal treatment. In relation to the rheological properties, Newtonian behaviour was observed for both microfiltered and pasteurised juices. The sensory tests on a hedonic scale showed good acceptance of both juices (microfiltered and pasteurised).     

Low pH Inactivation of Pectinesterase in Single Strength Orange Juice

Frozen orange juice concentrate (63.8° Brix) was reconstituted with water to single strength juice and supplemented with a commercial citrus pectinesterase (PE) to give an activity of 1.5 PE units/mL juice. Reconstituted juice and freshly squeezed single strength orange juice were treated with a cation exchange resin. Resin treatment decreased the pH of the juice from 3.75 to 2.0 and completely inactivated PE. PE was also inactivated following acidification of the juice to pH 2.0 with concentrated hydrochloric acid. Very little cloud loss occurred in refrigerated (4°C) juice at pH 2.0 for approximately 12 wk; however, a loss (> 95%) of ascorbic acid resulted. Only microorganisms died-off rapidly (> 99.9%) in juices adjusted to pH 2.0 using ion exchange resin, but not in juices lowered to pH 2.0 with HCl.     

Development and optimization of low temperature enzyme-assisted liquefaction for the production of colouring foodstuff from purple pitaya (<Emphasis Type="Italic">Hylocereus</Emphasis> sp. [Weber] Britton &; Rose)

An innovative liquefaction process for the production of colouring foodstuff from purple pitaya was developed and optimized. Conducting an enzyme screening, the most suitable enzyme preparation for the liquefaction of pitaya pulp at low temperatures (4–12 °C) was selected allowing extensive viscosity reduction (50%) and high betalain retention (80%). A modified D-optimal design was used for the optimization of significant influence factors. Maximizing a heuristic optimization function composed of regression terms of the responses relative viscosity (R ² = 0.97), betalain retention (R ² = 0.88) and betanin–isobetanin retention (R ² = 0.92), a numeric algorithm was established for process parameter optimization. The total juice yield was increased from 25–39 to 48–60% by implementation of the optimized liquefaction procedure into the pitaya juice production process. Mucilage separation steps were unnecessary and pitaya seeds could simply be separated as a by-product after juice filtration due to the extensive degradation of the mucilaginous matrix. In contrast to previously described mucilage liquefactions, the betalain profile was remarkably changed due to the applied enzymatic treatment resulting in a colour shift (Δh° = −14.7 ± 0.3) to bluish tones, and concentration of the so obtained pitaya juices from 12.3% TSS to 33% TSS and 65% TSS was successful at pilot plant scale.     

Physicochemical and nutritional properties and volatile constituents of six Japanese plum (<Emphasis Type="Italic">Prunus salicina</Emphasis> Lindl.) cultivars

The aim of this study is to contribute to the qualitative characterisation of six cultivars of Japanese plum (Prunus salicina Lindl.), i.e. ‘Black Amber’, ‘Suplumeleven’, ‘Fortune’, ‘Larry Ann’, ‘Suplumsix’ and ‘Songold’, by investigating their physicochemical and nutritional properties and their volatile fractions. The results indicate that the plum has a mean sugar content of 15% (between 12.3 and 17.8%), dietary fibre 1.2% (from 0.84 to 1.50%) and a mean energy value of 255 kJ 100 g⁻¹ of fresh produce (from 183 to 331 kJ 100 g⁻¹). ‘Black Amber’ has the highest phenolic and anthocyanin contents and the greatest total antioxidant activity. In terms of their volatile fraction, Japanese plums are relatively poor in volatile compounds in comparison with other stone fruits. However, there are significant differences between the cultivars studied, with ‘Fortune’ standing out as the richest in volatile compounds and especially in esters.     

Determination of phenolic composition and antioxidant capacity of blood orange juices obtained from cvs. Moro and Sanguinello (Citrus sinensis (L.) Osbeck) grown in Turkey

The phenolic compounds and antioxidant capacities of orange juices obtained from cvs. Moro and Sanguinello (Citrus sinensis (L.) Osbeck) were determined. A high-performance liquid chromatographic method coupled with diode-array detection was used to identify and quantify phenolic compounds of the orange juices. A total of 18 phenolic compounds were identified and quantified in Moro and Sanguinello orange juices, including hydroxybenzoic acids (2), hydroxycinnamic acids (5), flavanones (5), and anthocyanins (6). It was observed that total phenolic content of Moro juice was higher than that of Sanguinello juice. Ferulic acid was the most dominant hydroxycinnamic acid and cyanidin 3-(6″-malonyl glucoside) and cyanidin 3-glucoside were the most dominant anthocyanins in both cultivars. Antioxidant activities of orange juices were measured using the DPPH^· (2,2-diphenyl-1-picrylhydrazyl) method. According to DPPH^· assays, the antioxidant capacity of Moro juice was found to be higher than that of Sanguinello juice.