Rapid analysis of sugars in fruit juices by FT-NIR spectroscopy.

A simple analytical procedure using FT-NIR and multivariate techniques for the rapid determination of individual sugars in fruit juices was evaluated. Different NIR detection devices and sample preparation methods were tested by using model solutions to determine their analytical performance. Aqueous solutions of sugar mixtures (glucose, fructose, and sucrose; 0-8% w/v) were used to develop a calibration model. Direct measurements were made by transflection using a reflectance accessory, by transmittance using a 0.5-mm cell, and by reflectance using a fiberglass paper filter. FT-NIR spectral data were transformed to the second derivative. Partial least-squares regression (PLSR) was used to create calibration models that were cross-validated (leave-one-out approach). The prediction ability of the models was evaluated on fruit juices and compared with HPLC and standard enzymatic techniques. The PLSR loading spectra showed characteristic absorption bands for the different sugars. Models generated from transmittance spectra gave the best performance with standard error of prediction (SEP) <0.10% and R(2) of 99.9% that accurately and precisely predicted the sugar levels in juices, whereas lower precision was obtained with models generated from reflectance spectra. FT-NIR spectroscopy allowed for the rapid ( approximately 3 min analysis time), accurate and non-destructive analysis of sugars in juices and could be applied in quality control of beverages or to monitor for adulteration or contamination.     

Occurrence of microorganisms of public health and spoilage significance in fruit juices sold in retail markets in Greece

Fruit juices are an important part of the modern diet in many countries. However, few data are available concerning the microbiological quality of the fruit juices sold in Greece. Using standard microbiological procedures, we conducted a bacteriological survey of commercially sold, pasteurized, shelf-stable fruit juices from retail markets. A total of 120 samples of fruit juices sold in various retail markets were examined for their bacteriological quality. The pH of the tested juices was 2.4–4.8. Bacteria were isolated from 51 samples (42.5%) and fungi from 78 samples (65%). Escherichia coli O157:H7 was detected in four of the analyzed samples (3.34%), and Staphylococcus aureus was detected in four different samples (3.34%). In 11 samples (9.1%), the total number of microorganisms detected was as high as 125 colony-forming units (CFU). Acidophilic microorganisms were isolated from 26 samples (21.7%) and Blastomyces was detected in 46 samples (38.3%). All samples were negative for Lactobacillus, Clostridium perfrigens, Salmonella spp., Bacillus cereus, total coliforms, E. coli, and Listeria monocytogenes.Many of the microorganisms detected may cause disease in humans; thus, a number of the tested samples did not meet the Greek guidelines for the microbiological quality of juices. Use of a Hazard Analysis Critical Control Point (HACCP) system should be generally introduced into the juice industry sector to improve the quality of fruit juices, as well as other manufactured foods.     

A comparison of ready-to-use systems for evaluating the microbiological quality of acidic fruit juices using non-pasteurized orange juice as an experimental model.

Several alternative analytical methods are currently available for the rapid microbiological testing of food. Due to their many advantages, particularly their convenience of use, the popularity of ready-to-use systems for the enumeration of hygiene indicator microorganisms is increasing. However, the ability of these systems to enumerate stressed microorganisms, such as those that may be found growing in acidic foods, is unknown. Therefore, the aim of this study was to evaluate the performance of Petrifilm(tm) and SimPlate(tm) plates for the enumeration of total aerobes and fungi (yeasts and molds) in acidic fruit juices, using non-pasteurized orange juice as an experimental model. The samples were analyzed before and after neutralization of pH, and the results were compared with those obtained using conventional procedures, i.e. pour-plates containing Standard Methods Agar, acidified potato dextrose agar, or dichloran-glycerol agar. The results obtained with Petrifilm and SimPlate for counts of mesophilic aerobes as well as for yeast and mold correlated well with those obtained using conventional procedures. Although no statistically significant differences were observed between counts of non-neutralized and neutralized samples (alpha >/== 0.05), better correlation indexes were observed in the neutralized samples. Both Petrifilm and SimPlate proved to be good alternative methods for testing the microbiological quality of acidic fruit juices.     

Circulating microRNA profiles based on direct S-Poly(T)Plus assay for detection of coronary heart disease

Coronary heart disease (CHD) is one of the leading causes of heart-associated deaths worldwide. Conventional diagnostic techniques are ineffective and insufficient to diagnose CHD with higher accuracy. To use the circulating microRNAs (miRNAs) as non-invasive, specific and sensitive biomarkers for diagnosing of CHD, 203 patients with CHD and 144 age-matched controls (126 high-risk controls and 18 healthy volunteers) were enrolled in this study. The direct S-Poly(T)Plus method was used to identify novel miRNAs expression profile of CHD patients and to evaluate their clinical diagnostic value. This method is an RNA extraction-free and robust quantification method, which simplifies procedures, reduces variations, in particular increases the accuracy. Twelve differentially expressed miRNAs between CHD patients and high-risk controls were selected, and their performances were evaluated in validation set-1 with 96 plasma samples. Finally, six (miR-15b-5p, miR-29c-3p, miR-199a-3p, miR-320e, miR-361-5p and miR-378b) of these 12 miRNAs were verified in validation set-2 with a sensitivity of 92.8% and a specificity of 89.5%, and the AUC was 0.971 (95% confidence interval, 0.948-0.993, P < .001) in a large cohort for CHD patients diagnosis. Plasma fractionation indicated that only a small amount of miRNAs were assembled into EVs. Direct S-Poly(T)Plus method could be used for disease diagnosis and 12 unique miRNAs could be used for diagnosis of CHD.     

Citrinin in fruit juices

Despite the wide distribution of citrinin-producingPenicillium spp. there are only rare reports about the occurence of this mycotoxin in foodstuffs. Particularly, the discrepancy between the common detection of the applerotting fungusP expansum and the complete lack of data about the occurrence of citrinin in apple-based foods is noteworthy. Based on an indirect enzyme immunoassay (EIA) a study was performed aiming at the sensitive detection of citrinin in apple and other fruit juices. The direct analysis of diluted apple juices by the EIA failed due to pronounced sample matrix effects. Though these problems could be resolved by the extraction of artificially contaminated apple juice with dichloromethane, a poor recovery rate (20–30%) for citrinin was observed. Astonishingly, similar results (mean recovery of 29.9%) were received when doted apple juices were directly purified on immunoaffinity columns despite the minimal sample treatment associated with this method. For the detection of citrinin in tomatoe juices samples were purified with a liquid-liquid partition step. Again, the mean recovery rate was very low (32.0%). Analyzing 55 fruit and vegetable juices purchased in local retail stores only traces of citrinin (maximum 0.2 μg/L) could be detected in the samples.     

Antioxidant Properties of Fruits and Vegetables Shots and Juices: An Electron Paramagnetic Resonance Study

The antioxidant activity of some commercially available fruit and vegetable juices was evaluated with regard to their radical scavenging activity against the stable free radical 4-hydroxy-2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPOL) monitored by electron paramagnetic resonance (EPR) spectroscopy. TEMPOL is a stable nitroxide free radical characterized by a well-defined EPR spectrum consisting of three peaks. The integral intensity of the EPR spectra of TEMPOL was decreased upon juice addition, and the decrease was dose dependent. EPR spectroscopy using stable free radicals provides a simple, rapid, and sensitive method for the determination of antioxidant activity of fruit and vegetable juices. The method was standardized by using the standard antioxidant compound Trolox, and the antioxidant activity of the juices was expressed as Trolox equivalents. When concentrated juices of fruits and vegetables (shots) were considered, the evaluated antioxidant activity was almost twofold higher than that of the conventional, non-concentrated ones. Fruits and vegetables shots also showed very good stability during storage. This finding indicates that natural antioxidant compounds contained in commercially available concentrated juices are not eliminated or inactivated when the juices are kept refrigerated according to the instructions of the manufacturer.     

Comparative analysis of the volatile fraction of fruit juice from different Citrus species

The volatile composition of fruit from four Citrus varieties (Powell Navel orange, Clemenules mandarine, and Fortune mandarine and Chandler pummelo) covering four different species has been studied. Over one hundred compounds were profiled after HS-SPME-GC-MS analysis, including 27 esters, 23 aldehydes, 21 alcohols, 13 monoterpene hydrocarbons, 10 ketones, 5 sesquiterpene hydrocarbons, 4 monoterpene cyclic ethers, 4 furans, and 2 aromatic hydrocarbons, which were all confirmed with standards. The differences in the volatile profile among juices of these varieties were essentially quantitative and only a few compounds were found exclusively in a single variety, mainly in Chandler. The volatile profile however was able to differentiate all four varieties and revealed complex interactions between them including the participation in the same biosynthetic pathway. Some compounds (6 esters, 2 ketones, 1 furan and 2 aromatic hydrocarbons) had never been reported earlier in Citrus juices. This volatile profiling platform for Citrus juice by HS-SPME-GC-MS and the interrelationship detected among the volatiles can be used as a roadmap for future breeding or biotechnological applications.     

Viscosity decrease of pectin and fruit juices catalyzed by pectin lyase from Penicillium italicum in batch and continuous-flow membrane reactors

Summary The extracellular pectin lyase (PNL, E.C. 4.2.2.10) from Penicillium italicum was utilized in batch and confined in a continuous-flow ultrafiltration membrane reactor. The enzyme catalyzed the decrease in viscosity of pectin solutions at pH 6.0 as well as of different fruit juices at their respective pH. PNL decreased the viscosity of pectin solutions in the membrane (60% after 30 min) more than in the batch (46% after 70 min) reactors, but similar viscosity reduction of fruit juices was achieved in both reactors. The enzyme decreased the viscosity of grape, peach and melon juices to different extents, but failed to do so with apple or pear juices. It can be concluded that the utilization of PNL in a membrane reactor appears of interest for the clarification of fruit juices.     

Content of the <Emphasis Type="Italic">Alternaria</Emphasis> mycotoxin tenuazonic acid in food commodities determined by a stable isotope dilution assay

The Alternaria mycotoxin tenuazonic acid (TA) was quantified in fruit juices (n = 50), cereals (n = 12) and spices (n = 38) using a recently developed stable isotope dilution assay (SIDA). [¹³ C₆,¹⁵ N]-TA was used as the internal standard. Method validation revealed low limits of detection (LODs) of 0.15 μg/kg (fruit juices), 1.0 μg/kg (cereals) and 17 μg/kg (spices). The respective limits of quantitation were about three times higher. Recovery was about 100% for all matrices. The precision (relative standard deviation of replicate analyses of naturally contaminated samples) was 4.2% (grape juice; 1.7 μg/kg), 3.5% (whole wheat flour; 36 μg/kg) and 0.9% (curry powder; 215 μg/kg). The median content of TA in the analyzed samples was 1.8 μg/kg (fruit juices), 16 μg/kg (cereals) and 500 μg/kg (spices). Positive samples amounted to 86% (fruit juices), 92% (cereals) and 87% (spices).     

A single HPLC-PAD-APCI/MS method for the quantitative comparison of phenolic compounds found in leaf, stem, root and fruit extracts of Vaccinium angustifolium

A method was developed for the analysis of Vaccinium angustifolium Ait. (Lowbush blueberry), which is a widely used natural health product, particularly for the treatment of diabetic symptoms. While the anthocyanin content of the fruit has been well characterized, the chemistry of the vegetative parts used in supportive therapy for diabetes has been largely ignored. Using a metabolomics-based approach for compound identification with an emphasis on phenolic metabolites, a single HPLC-PAD-APCI/ MS method was developed for the separation and quantitation of the major metabolites found in the 95% ethanol extracts of leaf, stem, root and fruit. The leaf extract contained high concentrations of chlorogenic acid (approximately 100 microg/mg extract) and a variety of quercetin glycosides that were also detected in the fruit and stem extracts. Flavan-3-ol monomers (+)-catechin and (-)-epicatechin were found in all plant parts but their procyanidin dimers were exclusively identified in the stem and root. The accuracy and precision of the presented method were corroborated by low intra- and inter-day variations in quantitative results in all plant part extracts. Further validation of the extraction and analytical protocols focused on identified compounds with reputed anti-diabetic activity, revealing recoveries greater than 80% and detection limits of 0.12-2.73 microg/mL.     

Effect of Processing,Post-Harvest Irradiation,and Production System on the Cytotoxicity and Mutagenicity of Vitis labrusca L. Juices in HTC Cells

The juices of grapes (Vitis labrusca L.) are similar to the fruit itself because the main constituents of the fruit are present in the juice. However, their quality characteristics may be modified by the harsh technological processes used for the production of integral food, such as production systems of raw materials and post-harvest treatment of grapes with ultraviolet (UV) irradiation. Therefore, the present study analyzed juices produced naturally (by liquefying the fruit) or by the technological process of extraction by steam distillation (90°C) of grapes from organic and conventional production systems that were untreated or treated with UV type C (65.6 J/m² for 10 minutes). Using cultures of Rattus norvegicus hepatoma cells (HTC) in vitro, cytotoxic effects were assayed by the MTT test and by calculating the cytokinesis blocked proliferation index (CBPI), and mutagenic effects were measured by the cytokinesis block micronucleus assay. The results of the MTT assay and the CBPIs indicated that none of the juices were cytotoxic, including those that induced cell proliferation. The results of the micronucleus assay showed that none of the juices were mutagenic. However, the average number of micronuclei was lower in the juices produced from organic grapes, and cell proliferation, soluble acids and phenolic compounds were significantly higher. Compared with the natural juices, the integral juices of conventional grapes showed a higher average number of micronuclei as well as lower stimulation of cell proliferation and lower levels of bioactive compounds. The results demonstrate a beneficial effect of UV-C irradiation of post-harvest grapes in stimulating the synthesis of nutraceutical compounds without generating cytotoxic or mutagenic substances. Taken together, our findings support the consumption of grape juice and the application of food production techniques that enhance its nutritional value and promote its production, marketing and consumption.     

Performances of a multidimensional on-line SPE-LC-ECD method for the determination of three major catecholamines in native human urine: validation, risk and uncertainty assessments

A novel, multidimensional on-line SPE-LC method with electrochemical detection is described for the fully automated and direct analysis of the catecholamines norepinephrine, epinephrine and dopamine in urine. The integrated extractive clean-up of the raw biofluid is based on a SPE-column packed with restricted access material (RAM) which is modified with the affinity ligand nitrophenylboronic acid. The method was fully validated according to a recent approach based on an accuracy profile. The acceptance limits were set at +/-15% of the nominal concentration values. The method was found accurate over a concentration range from 15 to 500 microg/l for norepinephrine, from 5 to 500 microg/l for epinephrine and from 50 to 500 microg/l for dopamine. The relative risk for the use of the validated method in routine analysis was also assessed based on this validation strategy. It was found that at most 3.5% of future sample measurements will fall outside the acceptance limits. This demonstrates the high reliability of the analytical method described. Moreover, the measurements uncertainties were deduced from the validation experiments without any additional effort.     

Mutation induction and tissue culture in improving fruits

This review describes in vitro mutation induction methods in fruits and the in vitro selection procedures available for early screening. Results obtained through in vitro mutation techniques, including somaclonal variation, are reviewed and compared with the current achievements and future prospects of transgenic breeding. Plant improvement based on mutations, which change one or a few specific traits of a cultivar, can contribute to fruit improvement without altering the requirements of fruit industry. Induced mutations have well defined limitations in fruit breeding applications, but their possibilities may be expanded by the use of in vitro techniques. Tissue culture increases the efficiency of mutagenic treatments for variation induction, handling of large populations, use of ready selection methods, and rapid cloning of selected variants. Molecular techniques can provide a better understanding of the potential and limitations of mutation breeding e.g. molecular marker-assisted selection, which can lead to the early identification of useful variants. The relatively high number of research reports compared with the low number of cultivars released suggests that mutagenesis in combination with tissue culture is either ineffective or has yet to be exploited in fruits. Positive achievement recorded in other species seem to support the hypothesis that in vitro mutation induction has high potential also for fruit improvement. The possible contribution of a well-pondered and coordinated use of the numerous mutation induction, mutant selection, and field validation procedures available to advances in fruit breeding is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Validation of a fluid–structure interaction numerical model for predicting flow transients in arteries

Fluid–structure interaction (FSI) numerical models are now widely used in predicting blood flow transients. This is because of the importance of the interaction between the flowing blood and the deforming arterial wall to blood flow behaviour. Unfortunately, most of these FSI models lack rigorous validation and, thus, cannot guarantee the accuracy of their predictions. This paper presents the comprehensive validation of a two-way coupled FSI numerical model, developed to predict flow transients in compliant conduits such as arteries. The model is validated using analytical solutions and experiments conducted on polyurethane mock artery. Flow parameters such as pressure and axial stress (and precursor) wave speeds, wall deformations and oscillating frequency, fluid velocity and Poisson coupling effects, were used as the basis of this validation. Results show very good comparison between numerical predictions, analytical solutions and experimental data. The agreement between the three approaches is generally over 95%. The model also shows accurate prediction of Poisson coupling effects in unsteady flows through flexible pipes, which up to this stage have only being predicted analytically. Therefore, this numerical model can accurately predict flow transients in compliant vessels such as arteries.     

Apple juice inhibits human low density lipoprotein oxidation.

Dietary phenolic compounds, ubiquitous in vegetables and fruits and their juices possess antioxidant activity that may have beneficial effects on human health. The phenolic composition of six commercial apple juices, and of the peel (RP), flesh (RF) and whole fresh Red Delicious apples (RW), was determined by high performance liquid chromatography (HPLC), and total phenols were determined by the Folin-Ciocalteau method. HPLC analysis identified and quantified several classes of phenolic compounds: cinnamates, anthocyanins, flavan-3-ols and flavonols. Phloridzin and hydroxy methyl furfural were also identified. The profile of phenolic compounds varied among the juices. The range of concentrations as a percentage of total phenolic concentration was: hydroxy methyl furfural, 4-30%; phloridzin, 22-36%; cinnamates, 25-36%; anthocyanins, n.d.; flavan-3-ols, 8-27%; flavonols, 2-10%. The phenolic profile of the Red Delicious apple extracts differed from those of the juices. The range of concentrations of phenolic classes in fresh apple extracts was: hydroxy methyl furfural, n.d.; phloridzin, 11-17%; cinnamates, 3-27%; anthocyanins, n.d.-42%; flavan-3-ols, 31-54%; flavonols, 1-10%. The ability of compounds in apple juices and extracts from fresh apple to protect LDL was assessed using an in vitro copper catalyzed human LDL oxidation system. The extent of LDL oxidation was determined as hexanal production using static headspace gas chromatography. The apple juices and extracts, tested at 5 microM gallic acid equivalents (GAE), all inhibited LDL oxidation. The inhibition by the juices ranged from 9 to 34%, and inhibition by RF, RW and RP was 21, 34 and 38%, respectively. Regression analyses revealed no significant correlation between antioxidant activity and either total phenolic concentration or any specific class of phenolics. Although the specific components in the apple juices and extracts that contributed to antioxidant activity have yet to be identified, this study found that both fresh apple and commercial apple juices inhibited copper-catalyzed LDL oxidation. The in vitro antioxidant activity of apples support the inclusion of this fruit and its juice in a healthy human diet.     

Guidelines for analytical method development and validation of biotechnological synthesis of drugs. Production of a hydroxyprogesterone as model

In connection with biotechnological synthesis of pharmaceutical drugs, validated methods for quantification of both product and substrate at different time intervals are essential for proper calculation of rate coefficients. In this field, there still exist no guidelines for analytical validation, unlike the situation in the bioanalytical field. Therefore, in this study the detailed guidelines by FDA for bioanalytical method validation were applied to a typical biotechnological process; the enzymatic synthesis of 9alpha-hydroxyprogesterone in E. coli using progesterone as substrate. The process liquid was extracted and analyzed using an HPLC-DAD system. The quality control (QC) samples of the product demonstrated excellent precision (C.V.<1.5%) and accuracy between 99.3 and 107%. The study showed that the recommendations and the validation terms for bioanalytical methods can be used also for biotechnological production, but with some important exceptions. The tolerances (C.V. values) of the validation terms should be much narrower; the internal standard (I.S.) must be present in the process liquid before the start of the process and must be much different in structure from the substrate (so as not to participate in the biotechnological process). In addition, the selectivity must be checked very frequently during the process due to the changes in the blank process liquid with time.     

Hydrolysis of terpenyl glycosides in grape juice and other fruit juices: a review

The importance of monoterpenes on varietal flavour of must and other fruit juices has been reviewed. These compounds were mainly found linked to sugar moieties in grape juice and wines, showing no olfactory characteristics. In this way, analytical techniques developed to study these compounds, in both free or glycosidically forms, are discussed. Mechanisms to liberate terpenes were studied, making a comparative study between acidic and enzymic hydrolysis of terpene glycosides; as enzymic hydrolysis seems to be the most natural way to liberate terpenes, the ability to use glycosidases from grapes, yeasts, bacterial or exogenous, i.e. fungal commercial preparations, were reviewed. Re-arrangements of terpenes after acidic hydrolysis of glycoconjugated are discussed as well as potential adverse effects of enzyme preparations.     

Shear Viscosity Investigation on Mango Juice with High Frequency Longitudinal Ultrasonic Waves and Rotational Viscosimetry

Ultrasonic velocity and attenuation measurements were performed on mango juices at 25 MHz in order to estimate longitudinal viscosity. Juices were extracted from fruits, removed periodically from fruit batches undergoing ripening for 3 weeks under controlled conditions. The correlation between longitudinal viscosity and apparent dynamic shear viscosity, obtained from flow tests, showed that up to 12–13 wt.% of Soluble Solids Content (SSC), the juices presented a Newtonian behavior. In this case the relation between longitudinal viscosity measured by ultrasound and shear viscosity measured by flow tests was very simple leading to the conclusion that ultrasound could replace rotating viscosimeters for specific applications. Over this limit, the results were also clearly correlated but the correlation depended on the shear rate because of the shear thinning behavior of the juices certainly due to soluble pectins. The use of longitudinal ultrasonic waves as a tool for viscosity determination on large batches of samples is discussed at the end of this communication.     

Functional identification of organic cation transporter 1 as an atenolol transporter sensitive to flavonoids

Atenolol, a β1-adrenergic receptor blocker, is administered orally and its intestinal absorption has recently been indicated to be mediated by carrier protein and reduced markedly by ingestion of some fruit juices, such as apple and orange juices. This could be postulated to be a problem arising from the interaction of some components of fruit juices with atenolol at a transporter involved in its intestinal uptake, but the responsible transporter and its interacting components have not been identified yet. In an attempt to examine that possibility, we could successfully find that human organic cation transporter 1 (OCT1/SLC22A1), which is suggested to be expressed at the brush border membrane of enterocytes, is highly capable of transporting atenolol. In this attempt, OCT1 was stably expressed in Madin-Darby canine kidney II cells and the specific uptake of atenolol by the transporter was found to be saturable, conforming to the Michaelis-Menten kinetics with the maximum transport rate (V_max) of 4.00 nmol/min/mg protein and the Michaelis constant (K_m) of 3.08 mM. Furthermore, the OCT1-specific uptake was found to be inhibited by various flavonoids, including those contained in fruit juices that have been suggested to interfere with intestinal atenolol absorption. Particularly, phloretin and quercetin, which are major components of apple juice, were potent in inhibiting OCT1-mediated atenolol transport with the inhibition constants of 38.0 and 48.0 µM, respectively. It is also notable that the inhibition by these flavonoids was of the noncompetitive type. These results indicate that OCT1 is an atenolol transporter that may be involved in intestinal atenolol uptake and sensitive to fruit juices, although its physiological and clinical relevance remains to be further examined.     

Trace Elements in Fruit Juices

Fruit juices are widely consumed in tropical countries as part of habitual diet. The concentrations of several minerals in these beverages were evaluated. Four commercially available brands of juices were analyzed for cadmium, lead, copper, zinc, aluminum, iron, chromium, manganese, and molybdenum. The levels ranged from 0.02 to 0.08 mg/L for copper, from 0.05 to 0.23 mg/L for zinc, from 0.1 to 0.4 mg/L for aluminum, from 0.02 to 0.45 mg/L for iron, and from 0.01 to 0.22 mg/L for manganese. The levels of cadmium, lead, and chromium in all samples were very low or undetectable. The metal contents of fruit juices depend on a number of factors, including the soil composition, the external conditions during fruit growing and fruit harvesting, as well as on details of the fruit juice manufacturing processes employed. The concentrations of none of the metals in juice samples analyzed exceeded the limits imposed by local legislation.