A screening method for the determination of ascorbic acid in fruit juices and soft drinks

A simple and rapid liquid chromatographic method based on a new stationary phase Teknokroma, Tr-010065 Mediterranea sea₁₈ (15 cm × 0.4 cm, id 3 μm), to determine ascorbic acid in beverages is reported. With the proposed method the samples were analysed by direct injection without a previous treatment. The total analysis time does not exceed 6 min. The method showed a good repeatability (RSD < 2%: n = 6) and an excellent sensitivity (LOD = 0.01 mg/l). Seventeen samples were analysed, including fruit juices, soft drinks and isotonic beverages. Ascorbic acid contents ranged from 6.6 to 840 mg/l. The ascorbic acid stability in some beverages during their shelf-life was also evaluated. Degradation of about 54% was observed in a tea drink.     

Second order derivative spectrophotometric method for determination of vitamin C content in fruits,vegetables and fruit juices

A second-order derivative UV spectrophotometric method for determination of vitamin C [ascorbic acid (AA)] content in a variety of natural samples is described. The method is based on the measurement of a peak–baseline amplitude in the second derivative of the AA spectrum at 267.5 nm. The following corresponding regression equation was obtained within the concentration range 2×10^-5 to 1×10^-4 M AA (3.5–17.6 g/cm³ AA) in 1.0 M HCl solution: ²D_267.5=2.420×10⁴ c+0.025; the correlation coefficient was 0.9993 and the detection limit 4.2×10^-6 M. The results obtained by analysing 21 different species of fruits, vegetables and juices indicated a possibility for a more extensive application of the proposed method. This method is rapid, simple and requires no pretreatment of the analysed material, which makes it suitable for routine analyses. The reliability of the method was confirmed by comparative determinations with the generally accepted 2,6-dichloroindophenol method.     

Antioxidant activity versus cytotoxic and nuclear factor kappa B regulatory activities on HT-29 cells by natural fruit juices

The antioxidant activity (free radical scavenging ability and lipid oxidation inhibitory activity) and the activity in cell culture [influence on HT-29 human colon cancer cell viability and nuclear factor kappa B (NF-κB) activation] of natural fruit juices from red grape, strawberry, cherry and sour cherry were investigated in vitro. Analysis of polyphenolic composition of fruit juices showed the dominant presence of anthocyanins (cyanidin-3-glucoside, cyanidin-3-rutinoside, peonidin-3-rutinoside, pelargonidin-3-glucoside), anthocyanidins (procyanidins B1, B2 and B3), flavonoids (glucosides of myricetin, quercetin and kaempferol), and phenolic acids (neochlorogenic acid, chlorogenic acid, ellagic acid, p-coumaroylquinic acid) in juices. DPPH test and β-carotene bleaching method indicated that grape, strawberry, cherry and sour cherry natural juices (at the concentration of 2.5%) showed very strong free radical scavenging (75–92%) and antioxidant activity (71–94%). In addition, at the concentration of 0.01% they showed complete inhibition of copper-induced oxidation of human LDL (low density lipoprotein). In contrast, selected fruit juices did not show cytotoxic effects on HT-29 cells and NF-κB inhibitory activity (at the concentrations of 0.5 and 2%). Results of this study showed no correlation between the antioxidant activity of natural fruit juices from red grape, strawberry, cherry and sour cherry and their effect on HT-29 cell viability and NF-κB inhibitory activity.     

Estimation of the freezing point of concentrated fruit juices for application in freeze concentration

In freeze concentration operations the fluids remain at temperatures below 0 °C. For a good study of this concentration operation is very important to know the values of freezing point. The aim of this work was to establish a model that predicts the freezing point of fruit juices at various concentrations within the range of interest for freeze concentration (10-40 °Brix). The model proposed relates the freezing point of a juice with the concentrations of main sugars present in the juice: sucrose, glucose and fructose. The freezing point of apple juice, pear juice and peach juice was determined experimentally at various concentrations, and experimental results were well correlated with model calculations.     

Stability of virgin olive oil and behaviour of its natural antioxidants under medium temperature accelerated storage conditions

The aim of the present research is to advance the study of virgin olive oil stability, in particular the behaviour of its natural antioxidants during long term storage. The changes undergone by tocopherols and complex and simple phenolic compounds and their antioxidant activity were studied under medium temperature (50 °C) accelerated oxidation conditions over a storage period of 8 months. Different oxygen availability (open and closed bottles, OB and CB) and four different monovarietal Tunisian virgin olive oils (VOO; Chemlali, Chétoui, El Hor and Oueslati) which vary in their fatty acid profile and content of natural antioxidants were employed. Oueslati VOO showed the lowest initial oxidation rate (4.6 PV/week) and as a consequence the highest induction period (IP; 16 days) as compared to the other VOOs studied (initial rate from 7.7 to 12.1 PV/week and IP from 9 to 12 days for El Hor and Chemlali, respectively, in both cases). In all cases the complete depletion of α-tocopherol corresponded with the observed induction period. Since the oxidation rate in the varieties studied is not sufficiently different to explain the great differences in the initial degradation rate observed in the phenolic compounds (mainly between Chétoui VOO, 163 μmol/kg/week, as compared to the other VOO oils, e.g. 6.1 and 2.5 μmol/kg/week, respectively, in Chemlali and El Hor VOOs), a concentration dependent degradation rate of complex phenols is suggested.     

A review of natural antioxidants and their effects on oxidative status, odor and quality of fresh beef produced in Argentina

Meat derived from pasture feeding, is associated with a high level of antioxidants. Antioxidants are incorporated within cell membranes and protect tissues against oxidation from reactive oxygen species. This maintains the overall quality of meat and secondary products. This paper reviews the implications of incorporating natural antioxidants into fresh beef, focusing on the benefits of feeding cattle good quality pasture. Pasture samples typically have higher levels of α-tocopherol, β-carotene, ascorbic acid and glutathione than feedlot samples. These compounds retard lipid and protein oxidation in fresh and stored meat, and preserve the color and odor quality of beef. The significance of antioxidant enzymes is variable, because their behavior depends on individual redox status before slaughter. Understanding total antioxidant activity requires information on antioxidant and pro-oxidant status. With an abundance of pasture, Argentina has a natural advantage in producing meat with a high antioxidant value.     

Calculation method for designing a multi-plate freeze-concentrator for concentration of fruit juices

The aim of this work is to establish a calculation method for designing and sizing of equipment for film freeze-concentration of fruit juices. The various steps are outlined of an algorithm that uses the characteristics of the juice as inputs.The calculation method assumes that the amount of fruit juice, its concentration (^°Brix), and its sugar composition (% of fructose, glucose and sucrose) are known. Using pre-set (constant) values for the flow of concentrated juice and for the heat flow, the algorithm predicts the values of the main unknowns: the concentration of impurities in the ice, the concentration of sugars in the final concentrate, the heat-exchange surface needed, the amount of ice obtained, and the duration of the concentration step.Using this calculation method, one can estimate the size of the equipment and its operational costs, which can be used to analyse the economic viability compared to alternative processes.     

Behaviour of aroma volatiles during the evaporative concentration of some tropical fruit juices and pulps

The dynamics of aroma separation from some tropical fruit juices and pulps was studied using a thin film evaporator. In the case of mango (Mangifera indica Linn, Alphonso and Totapuri varieties) and guava (Psidium guajava Linn) pulps, 90% of each of the volatile fraction, esters, carbonyls and alcohols, was removed at 30–35% evaporation of the water in a single pass. In the case of pineapple (Ananas sativa Schult F) juice, 90% separation of esters and carbonyls required about 80% and 47% evaporation, respectively. However, the behaviour of alcohols in pineapple juice was found to be similar to that of mango and guava. Mango pulp from Alphonso and Totapuri varieties on 60% evaporation showed a loss in oxygenated terpenes of 80% and 63%, respectively, while guava pulp lost about 58% oxygenated terpenes on 60% concentration. The dynamics of the total aroma volatiles separation from the fruit juices and pulps showed that, in a single pass evaporation, 85–90% volatiles were removed at a juice evaporation degree of 60% water, while the same extent of aroma removal occurred at 32–35% total evaporation by multiple pass.     

Fast and reliable analyses of sulphite in fruit juices using a supramolecular amperometric detector encompassing in flow gas diffusion unit

A new compact system encompassing in flow gas diffusion unit and a wall-jet amperometric FIA detector, coated with a supramolecular porphyrin film, was specially designed as an alternative to the time-consuming Monier-Williams method, allowing fast, reproducible and accurate analyses of free sulphite species in fruit juices. In fact, a linear response between 0.64 and 6.4 ppm of sodium sulphite, LOD = 0.043 ppm, relative standard deviation of ±1.5% (n = 10) and analytical frequency of 85 analyses/h were obtained utilising optimised conditions. That superior analytical performance allows the precise evaluation of the amount of free sulphite present in foods, providing an important comparison between the standard addition and the standard injection methods. Although the first one is most frequently used, it was strongly influenced by matrix effects because of the unexpected reactivity of sulphite ions with the juice matrixes, leading to its partial consumption soon after addition. In contrast, the last method was not susceptible to matrix effects yielding accurate results, being more reliable for analytical purposes.     

Effect of thermosonication on bioactive compounds in watermelon juice

Freshly squeezed watermelon juice was subjected to thermosonication treatments with processing variables of temperature (25-45 °C), amplitude level (24.1-60 ??m) and processing time (2-10 min) at a constant frequency of 20 kHz and pulse durations of 5 s on and 5 s off. Hunter color values (L*, a* and b*), lycopene (LC), phenolic content (TP) and ascorbic acid (AA) content were measured. Higher retention of AA and LC was observed at low treatment conditions. AA, LC & TP decreased significantly at higher amplitude levels and at the maximum processing time. A second order response function covering the range of experimental conditions investigated was obtained for each of the compounds measured. Model predictions for color parameters and bioactive compounds were closely correlated to the experimental results obtained. Prediction models were found to be significant (p < 0.05) with low standard errors and high coefficients of determination (R²). It was concluded that thermosonication significantly influences key watermelon juice quality parameters     

Use of kinetic, Weibull and PLSR models to predict the retention of ascorbic acid, total phenols and antioxidant activity during storage of pasteurized pineapple juice

In this study, the usefulness of different mathematical models to predict the retention of ascorbic acid (AA), total phenols (TP) and DPPH radical scavenging activity (SA) of pasteurized pineapple juices during storage has been evaluated. The results indicate that first-order kinetic model provided the best prediction of the degradation of AA (MAE = 0.0059; MRE = 0.0117; MSE = 0.0001; R² = 0.9995) whereas Weibull model provided the less satisfactory prediction (MAE = 0.2387; MRE = 0.2911; MSE = 0.0769; R² = 0.9993). In addition, zero-order (MAE = 0.0016; MRE = 0.0017; MSE = 0.0000; R² = 0.9992) and first-order (MAE = 0.0027; MRE = 0.0029; MSE = 0.0000; R² = 0.9989) kinetic models are adequate models for application in the prediction of TP loss, and first-order kinetic (MAE = 0.0294; MRE = 0.0549; MSE = 0.0015; R² = 0.9845) and Weibull (MAE = 0.0533; MRE = 0.0881; MSE = 0.0044; R² = 0.9823) models are recommended to predict the change of SA. These results show that the behaviors of AA, TP and SA during storage of juices can be accurately described by different prediction models. Therefore, the selection of the most adequate model is of great importance to predict nutritional deterioration in food products during storage.     

Essential oil nanoemulsions: antibacterial activity in contaminated fruit juices

Many human acid tolerant bacterial and fungal pathogens can be transmitted through the consumption of the contaminated fruit juices. We aim to formulate essential oil nanoemulsions (basil, black seed, turmeric, clove & cinnamon), determine their ability to clear contamination by food borne bacterial pathogens from fruit juices. The antibacterial activity of the optimised formulations was tested in the fruit juices against bacterial pathogens causing gastrointestinal tract infections. The minimum bactericidal concentration (MBC) of clove emulsions ranged from 15.6 to 25 μL mL⁻¹. Cinnamon oil emulsion had an MBC ranging between 15 and 31 μL mL⁻¹. At MBC, cinnamon oil emulsions caused a 6log₁₀ decrease in viable counts by 8 h and maintained the sterility of fruit juices for 7 days at ambient temperature. Thus, clove and cinnamon microemulsions can be used as juice additives to control food borne bacterial pathogens and maintain the bacterial sterility of fruit juices.     

An industrial approach in the search of natural antioxidants from vegetable and fruit wastes

Eleven fruit and vegetable byproducts and two minor crops were screened for industrial polyphenol exploitation potential by determination of their extraction yield, total phenolic content (TPC, Folin–Ciocalteu), and antioxidant activity (NTZ/hypoxanthine superoxide assay, ferric thiocyanate method). Extracts with the highest activity, economic justification and phenolic content were obtained from apple (TPC maximum 48.6 ± 0.9 mg Gallic acid equivalents g⁻¹ dry extract), pear (60.7 ± 0.9 mg GAE g⁻¹), tomato (61.0 ± 3.0 mg GAE g⁻¹), golden rod (251.4 ± 7.0 mg GAE g⁻¹) and artichoke (514.2 ± 14.9 mg GAE g⁻¹). Apple, golden rod and artichoke byproducts were extracted at pilot plant scale and their antioxidant activity was confirmed by determination of their free radical scavenging activity (DPPH) and the inhibition of stimulated linoleic acid peroxidation (TBA and Rancimat^® methods). The preservative effect of the three extracts (determination of the peroxide value in test crème formulations with 0.1–1.0% extract concentrations) was similar to the established antioxidants Oxynex^® 0.1%, Controx^® KS 0.15%, and butylated hydroxytoluene (BHT) 0.01%. This study demonstrates the possibility of recovering high amounts of phenolics with antioxidant properties from fruit and vegetable residuals not only for food but also cosmetic applications.     

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).     

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.     

Functionality of fruit powders in extruded corn breakfast cereals

Consumer interest in naturally colored foods such as breakfast cereals is growing. Degermed white cornmeal, sucrose, citric acid and dehydrated fruit powder (blueberry, cranberry, Concord grape and raspberry) were mixed in 84.3%:14.3%:0.4%:1.0% proportions, then extruded in a laboratory-scale twin-screw extruder. Feed rate was 255 g/min; water was pumped at a rate of 12.5 g/min; screw speed was 175 rpm. Cooking temperature during extrusion was generally <130 °C. Samples were cut into small spheres and dried to 5% moisture. Cereals were stored at room temperature in opaque bags. The control samples were lighter and less red than the fruit cereals. Soluble phenolics and anthocyanins were higher in the fruit cereals. At three and six weeks of storage, fruit cereals had smaller levels of hexanal, as measured by gas chromatography of headspace of ground cereals. Although anthocyanins from fruit powders survive extrusion and retain some antioxidant activity, the levels used in this study may have been too low. Higher levels of fruit will increase production costs, but the expense may be offset by the more attractive and functional cereals that result.     

Validation of a HPLC method for simultaneous determination of main organic acids in fruits and juices

A liquid chromatographic method for fast and simultaneous determination of tartaric, malic, ascorbic and citric acids was validated for further application to fruits and juices. Moreover, the organic acids content of commercial samples of fruits and juices were evaluated, as well as the ascorbic acid stability during the storage. Determination of organic acids was carried out using a liquid chromatograph coupled to a diode array detector, with reversed phase (C₁₈ column) and isocratic elution with 0.01 mol L⁻¹ KH₂PO₄ (pH = 2.60) mobile phase. The validation parameters showed efficiency, adequate linearity, relative standard deviation values between 0.4% and 2.3% (n = 10) for repeatability and from 1.2% to 5.0% (n = 18) for reproducibility, limits of detection (LD) were between 0.03 and 3.31 μg mL⁻¹ and quantification (LQ) were between 0.10 and 11.03 μg mL⁻¹, recovery rates were between 82% and 110%, for two levels. In addition, the method is fast (10 min) and generates low and non-toxic residues. The values found for vitamin C were about 10 times above the values declared at the package. Ready to drink juices have a composition similar to the fruit, concerning to organic acids, except for the powder juice, in which only ascorbic and citric acids were found, for all tastes. After opening the package, a decrease of 14.0% and 27.0% in ascorbic acid content was observed for orange powder and ready to drink juices, respectively.     

A survey of Irish fruit and vegetable waste and by-products as a source of polyphenolic antioxidants

In this study, fruit and vegetable by-product and waste sources in Ireland were tested for their antioxidant activity and polyphenol content. The highest levels of antioxidants measured by both ferric reducing antioxidant power (FRAP) and diphenyl-picrylhydrazyl (DPPH) assays, were detected in whole kiwifruit. Of the vegetable by-products, broccoli stems showed the best antioxidant potential. The level of polyphenols as assessed by the Folin–Ciocalteu Reagent (FCR) was significantly correlated with the level of polyphenols by HPLC–DAD (r = 0.93). The level of polyphenols assessed by HPLC–DAD was not significantly correlated with the antioxidant assays. Apple pomace and vegetable by-products were found to be good sources of both polyphenols and antioxidants and due to their abundance may be exploitable resources to use as food ingredients.     

A comparison of nutrient density scores for 100% fruit juices

ABSTRACT:  The 2005 Dietary Guidelines for Americans recommend that consumers choose a variety of nutrient-dense foods. Nutrient density is usually defined as the quantity of nutrients per calorie. Food and nutrition professionals should be aware of the concept of nutrient density, how it might be quantified, and its potential application in food labeling and dietary guidance. This article presents the concept of a nutrient density score and compares nutrient density scores for various 100% fruit juices. One hundred percent fruit juices are popular beverages in the United States, and although they can provide concentrated sources of a variety of nutrients, they can differ considerably in their nutrient profiles. Six methodologies were used to quantify nutrient density and 7 100% fruit juices were included in the analysis: apple, grape, pink grapefruit, white grapefruit, orange, pineapple, and prune. Food composition data were obtained from the USDA National Nutrient Database for Standard Reference, Release 18. Application of the methods resulted in nutrient density scores with a range of values and magnitudes. The relative scores indicated that citrus juices, particularly pink grapefruit and orange juice, were more nutrient dense compared to the other nonfortified 100% juices included in the analysis. Although the methods differed, the relative ranking of the juices based on nutrient density score was similar for each method. Issues to be addressed regarding the development and application of a nutrient density score include those related to food fortification, nutrient bioavailability, and consumer education and behavior.     

A profile of physicochemical and antioxidant changes during fruit growth for the utilisation of unripe apples

The physicochemicals associated with fruit quality, antioxidant activities and changes in polyphenol composition during Fuji apple growth were investigated from the 25th to 105th day after full bloom day (DAFB). Three kinds of antioxidant assays, including oxygen radical absorbing capacity (ORAC) were executed, and polyphenol composition were examined using HPLC. The change in weight of the Fuji apples during fruit growth showed a typical sigmoidal curve. Both the rise of the soluble solid content and the drop of the titratable acidity appeared to be more significant (p < 0.05) after the 85th DAFB. Concurrently, the antioxidant activities and the polyphenol content decreased (p < 0.05) rapidly after the same date. Accordingly, a profitable thinning date can be chosen around the 85th DAFB to utilise dropped unripe apples as resources of antioxidants. Furthermore, the antioxidant activities of Fuji apples may be highly affected by the chlorogenic acid content.