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.     

Polyphenols,ascorbic acid and antioxidant capacity of commercial nutritional drinks,fruit juices,smoothies and teas

Polyphenols of plant origin have received special interest in the last decade because of their potential health benefits. Consequently, many beverages with words ‘antioxidant’ and ‘polyphenols’ have been developed. However, many of the claims are misleading because some beverages so labelled have either no or minimal levels of polyphenols. The objectives of this study were to quantify polyphenols (TPC) and ascorbic acid contents and antioxidant capacity (AOC) of different beverages; identify major polyphenols in beverages that showed higher TPC; correlate the claim on the label with TPC and AOC; and determine the impact of consumer refrigerated storage on TPC and AOC of aronia, blackcurrant and pomegranate juices which contained the most TPC and AOC. Major polyphenols identified from these juices included anthocyanins, myricetin and epicatechin. TPC of aronia, blackcurrant and pomegranate juices was relatively stable during consumer refrigerated storage, even when the juice had been intermittently exposed to air.     

Speciation of iron and sulfate in acid waters: aqueous clusters to mineral precipitates

Acid mine drainage (AMD) contaminates surface water bodies, groundwater, soils, and sediments at innumerable locations around the world. AMD usually originates by weathering of pyrite (FeS2) and is rich in Fe and sulfate. In this study, we investigated speciation of FeII, FeIII, and SO4 in acid waters by Fourier transform infrared and X-ray absorption spectroscopy. The molalities of sulfate (15 mmol/ kg) and iron (10, 20, and 50 mmol/kg), and pH (1, 2, and 3) were chosen to mimic the concentration of ions in AMD waters. Sulfate and FeII either associate in outer-sphere complexes or do not associate at all. In contrast, sulfate interacts strongly with FeIII. The predominating species in FeIII-SO4 solutions are hydrogen-bonded complexes; inner-sphere complexes account only for 10+/-10% of the total sulfate. Our results show that the mode of interaction between FeIII and sulfate is similar in aqueous phase and in nanocrystalline precipitate schwertmannite (approximately FeO(OH)3/4(SO4)1/8). Because of this similarity, schwert-mannite should be the phase that controls solubility and availability of FeIII, SO4, and indirectly also other components in the AMD solutions.     

Ascorbate oxidase from starfruit (Averrhoa carambola): preparation and its application in the determination of ascorbic acid from fruit juices

A study was conducted to utilize ascorbate oxidase (AAO) from very immature starfruit for the enzymatic determination of ascorbic acid (AsA) in colored samples. The enzyme preparation was carried out by a combination of (NH₄)₂SO₄ fractionation, DEAE-Toyopearl 650 M and ultrafiltration. A calibration curve for AsA was constructed by plotting the amount of AsA oxidized by the enzyme at a specified reaction time against the absorbance. The curve showed a linear relationship in the range of 0–100 μg ml⁻¹ AsA used. Using the plot, the values of AsA in juice samples were determined and compared with the conventional 2,6-dichloroindophenol method.     

水溶性壳聚糖在果汁澄清中的应用研究

研究水溶性壳聚糖对果汁的澄清作用,测定果汁经壳聚糖澄清后主要成分的变化。结果表明,2%壳聚糖水溶液能提高果汁的透光率,且不影响果汁的营养成分,是一种有效的果汁澄清剂。     

乳酸菌发酵果蔬汁的风味研究进展

风味是人的感官受食物刺激后各种感觉的综合,是消费者判断果蔬汁品质的重要指标。果蔬汁通过乳酸菌发酵可改善原有风味与品质,但存在加工工艺不成熟、风味形成机制尚不明确等问题。文章从乳酸菌发酵对果蔬汁风味的影响以及工艺优化措施等方面进行系统梳理,并对益生菌发酵果蔬饮料的发展趋势与面临的挑战提出了展望,以期为果蔬汁的深度开发、风味调控等方面提供借鉴。     

全球果汁及果汁饮料消费状况

来自Euromonitor的资料显示,自1992年至2007年,全球果汁及果汁饮料消费市场大多呈现平稳的增长势头.     

Commercialization conditions and practices influence the microbiological quality of mineral waters

The objective of the present study was to determine the microbiological quality of bottled mineral water marketed in commercial establishments and by street vendors and to evaluate the influence of the storage and maintenance conditions on the microbiological quality of the product. Ten samples from the same batches of five different brands of water were analyzed, for a total of 50 samples. Of the five brands analyzed, only one (brand A), when collected in a commercial establishment, complied with the legal Brazilian standards for mineral water with respect to the presence of total coliforms, fecal coliforms, and Pseudomonas aeruginosa. The remaining samples failed to comply with these microbiological standards for at least one of the parameters evaluated. The water samples obtained from street vendors were inferior in microbiological quality to samples from the same batch that were obtained from commercial establishments.     

绿原酸对果汁加热过程中5-羟甲基糠醛形成的影响

绿原酸是水果中常见的酚酸,而5-羟甲基糠醛(5-hydroxymethylfurfural,5-HMF)是干制水果中含量较高的食品内源性污染物。将水果中绿原酸的主要组分3-咖啡酰奎尼酸(3-O-caffeoylquinic acid,3-CQA)添加到4种果汁中,在90℃下热处理48 h,以探讨绿原酸对水果热加工中5-HMF形成的影响。结果表明:3-CQA促进5-HMF形成。果汁中3-CQA浓度分别为0.5、5、50 mmol/L时,苹果汁中5-HMF含量分别增加23.5%、60.4%和115.6%;葡萄汁中的5-HMF分别增加5.6%、35.3%和74.5%;桃汁中的5-HMF分别增加12.5%、73.7%和199.8%;橙汁中的5-HMF分别增加22.0%、56.3%和125.0%。同时发现,3-CQA含量随着加热时间的延长而减少,其中35.8%的3-CQA转化为4-咖啡酰奎尼酸、5-咖啡酰奎尼酸、咖啡酸和奎尼酸,这些降解产物都促进5-HMF形成。     

HPLC assay of ascorbic acid in fresh and processed fruit and vegetables

A method is reported to estimate ascorbic acid (AA) content in fresh and preserved fruit and vegetables. Following its extraction by HPO₃, AA is separated by HPLC on a strong anionic pellicular (Partisil 10 SAX) column, isocratically eluting with 0·1 m sodium acetate buffer solution at pH 4·25, and detecting at 250 nm by a variable wavelength UV detector. The amount of AA is estimated by adding benzoic acid as an internal standard and processing data by an attached electronic printer plotter integrator.The method has shown a high selectivity and speed together with a very good reliability in the range 0·04% to 1% AA.     

Simplification of the dinitrophenylhydrazine method for the photometric determination of ascorbic acid and dehydroascorbic acid in fruit juices. I. Application to juice of black current (author's transl)]

The photometric determination of ascorbic acid and dehydroascorbic acid by preparing the 2,4-dinitrophenylhydrazone derivative of dehydroascorbic acid and purifying it by thinlayerchromatography was simplified and adapted to the microliter system of Eppendorf Ger?tebau, Hamburg, Germany. Using this method with juice of black current, quite reproducible results for vitamin C contents were obtained. Compared with the method of the International Federation of Fruit Juice Producers (titration with 2,6-dichlorphenolindophenol) the contents of vitamin C found with nine different commercial juices of black current were lower from 13 to 30%.     

Provitamin A carotenoids and ascorbic acid contents of the different types of orange juices marketed in Spain

The vitamin C and provitamin A carotenoids contents of 25 commercially available Spanish orange juices were studied. Large differences in the levels of these compounds were found. On average, ultrafrozen orange juices (UFOJ) and orange juices from the ecological agriculture (OJFEA) showed the highest ascorbic acid contents (518 and 412 mg/l respectively) among the different kinds of orange juices studied. Some disagreement between the declared and the actual amounts of vitamin C were found. Provitamin A carotenoids were determined by means of the corresponding standards. The monohydroxycarotenoid accompanying β-cyptoxanthin in orange juices was identified as the non-provitamin A carotenoid, zeinoxanthin, on the basis of the methylation test with acidified methanol. Unusually high contents of β-carotene (>0.5 mg/l) were found in two samples, which could indicate that substantial amounts of the pigment were added to those juices. The mandarin juice analyzed showed the highest provitamin A activity (359.3 retinol activity equivalents/l) Among the orange juices surveyed, UFO proved to be the best source of provitamin A (78.5 retinol activity equivalents/l, on average). The lowest contents were found in orange juices from concentrate (OJFC) (22.4 retinol activity equivalents/l, on average, without considering the orange juices with unusual β-carotene contents).     

Diversity of the heterotrophic microbial populations for distinguishing natural mineral waters

In the recent years the consumption of natural mineral waters has risen all over the world, becoming a usual alternative for tap water and other beverages. Natural mineral waters are complex environments containing a high diversity of autochthonous microbiota. The identification and characterization of this indigenous microbiota may help to detect changes occurring in the different steps of the bottling process and take preventive measures before the bottled water arrives to the consumer. The aims of this study were to describe the bacterial heterotrophic populations in natural mineral waters with a cultivation-dependent method and determine whether their autochthonous microbiota were specific enough to be clearly distinguished from that of other natural mineral waters with a phenotypic-based method. For this purpose, water from three independent Spanish springs was sampled in two seasons (winter and summer) and heterotrophic aerobic bacterial strains were isolated at two temperatures (22 ± 2°C and 36 ± 2°C) on R2A agar. Isolates were phenotyped biochemically with Php-48 plates (Bactus AB, Sweden), and the indexes of diversity and similarity between populations were calculated. The 16S rRNA gene of the most representative strains of each biochemical cluster was sequenced for its identification. Finally, a ten-fold cross-validation method was assayed for the identification of the origin of a natural mineral water when phenotyping a set of isolates. High levels of diversity were found at all sites. One of the sources was found to present less diversity due to a confirmed contamination with Pseudomonas aeruginosa. The study of the similarities showed that growing temperatures and seasons caused significant differences in structures and composition at the sources. In addition, several bacterial species were isolated and identified, some of them rarely isolated in natural mineral waters, revealing the complexity and lack of knowledge of these ecosystems. Consequently, the applied phenotypic methodology was found to be feasible for differential identification of microbiota in these environments. Moreover, the experimental model assayed was strong enough to identify the origin of a natural mineral water. It may thus be possible to confirm that the evaluation of diversity of heterotrophic aerobic bacterial populations could be applied to identify bottled water sources.     

Assessing the acid tolerance and the technological robustness of probiotic cultures for fortification in fruit juices

The suitability of probiotic cultures as fruit juice supplements was examined by assessing their acid tolerance and technological robustness. Survival of Lactobacillus and Bifidobacterium strains in orange juice (OJ), pineapple juice (PJ) and cranberry juice (CJ) was monitored. Results revealed that extensive differences exist among probiotic strains regarding their acid resistance. All of the strains screened survived for longer in OJ and PJ compared to CJ. L. casei DN-114 001, L. rhamnosus GG and L. paracasei NFBC43338 displayed the greatest robustness surviving at levels above 10⁷ cfu ml^− 1 in OJ and above 10⁶ cfu ml^− 1 in PJ for at least 12 weeks. Probiotic tolerance to thermal and non-thermal processing was studied to determine the feasibility of their addition to OJ prior to pasteurisation. OJ fortified with probiotic cultures was subjected thermal pasteurisation at 76 °C for 30 s and 90 °C for 1 min in addition to a high pressure treatment of 400 MPa for 5 min. Results indicated no strain was capable of withstanding treatments necessary to achieve a stable juice at levels > 10⁶ cfu ml^− 1. The outcome of the overall study points to L. rhamnosus GG, L. casei DN-114 001 and L. paracasei NFBC43338 as having promising potential for exploitation as functional supplements in fruit juices due to their impressive tolerance in acidic environments; however, fortification post processing is recommended.Industrial relevanceThe ability of health-promoting cultures to survive for at least 12 weeks in orange juice and pineapple juice at commercially critical levels renders them suitable strains for exploitation. Their inclusion may enhance the market potential of these already successful beverages.     

Anthocyanins and chlorogenic acid copigmentation - influence on the colour of strawberry and chokeberry juices

The effect of copigmentation of chlorogenic acid with anthocyanins in strawberry and chokeberry juices was investigated. It was found that chlorogenic acid, at concentrations greater than that of anthocyanins, enhanced the colour intensity of these juices. The maximum copigmentation effect in both juices was observed at pH 3.4. In the investigated range of the copigment/pigment ratio, i.e. 11 to 501, absorbance increased (A) linearly with copigment content, A/g chlorogenic acid was greater in chokeberry than in strawberry juices. In solutions of purified pigments of these fruits, smaller copigmentation effects were observed than in juices under the same conditions, which indicates the participation of natural copigments present in fruits in the copigmentation process.     

Effects of ultra high hydrostatic pressure on Listeria monocytogenes and natural flora in broth, milk and fruit juices

Listeria monocytogenes was subjected to ultra high hydrostatic pressure (UHHP) treatments from 200 to 700 MPa at 25 °C in broth, raw milk, peach juice and orange juice. Survivor curves showed that cell death increased as pressure increased. After 10 min pressure treatment at 400 MPa reductions of about 2.09 and 2.76 log CFU mL^?1 in aerobic bacteria and L. monocytogenes, respectively, were produced in raw milk, this increased to 5.09 and 6.47 log CFU mL^?1, respectively, at 600 MPa. Death of bacteria at UHHP treatment was greater in orange juice than peach juice, and in peach juice than milk. Listeria monocytogenes was more sensitive to increased pressure than increased pressurization time. Injury of L. monocytogenes occurred from 0 to 100%. Factors effecting the rate of microbial inactivation are: pressure, age of cell, composition of medium, and pressurization time. UHHP inactivation can be used to extend shelf life and increase food quality during storage, and may also contribute to inactivation of L. monocytogenes.     

Degradation of anthocyanins in sour cherry and pomegranate juices by hydrogen peroxide in the presence of added ascorbic acid

Effects of hydrogen peroxide in the presence of ascorbic acid on the degradation of sour cherry and pomegranate juice anthocyanins were studied at three H₂O₂ concentrations (4.65, 6.98 and 9.31 mmol l⁻¹) and two ascorbic acid concentrations (60 and 80 mg l⁻¹) at 20 °C. Degradation of anthocyanins by H₂O₂ was fitted to first-order reaction kinetics in sour cherry and pomegranate juices. A similar degradation pattern was found at the 60 and 80 mg ascorbic acid levels for pomegranate juice. Degradation of sour cherry anthocyanins at the 60 mg ascorbic acid level was fitted to a second-order reaction kinetic, whereas it was a first-order reaction kinetic after a lag period occurred at the 80 mg level. Ascorbic acid, at 80 mg l⁻¹, markedly accelerated the degradation of anthocyanins in sour cherry juice at all the H₂O₂ concentrations studied. In contrast, ascorbic acid, at both 60 and 80 mg l⁻¹, protected the anthocyanins from the degradation by H₂O₂ in pomegranate juice.     

Sunlight-induced photochemical decay of oxidants in natural waters: implications in ballast water treatment

The transport and discharge of ship ballast water has been recognized as a major vector for the introduction of invasive species. Chemical oxidants, long used in drinking water and wastewater treatment, are alternative treatment methods for the control of invasive species currently being tested for use on ships. One concern when a ballasted vessel arrives in port is the adverse effects of residual oxidant in the treated water. The most common oxidants include chlorine (HOCl/OCl-), bromine (HOBr/OBr-), ozone (03), hydrogen peroxide (H2O2), chlorine dioxide (ClO2), and monochloramine (NH2Cl). The present study was undertaken to evaluate the sunlight-mediated photochemical decomposition of these oxidants. Sunlight photodecomposition was measured at various pH using either distilled water or oligotrophic Gulf Stream water for specific oxidants. For selected oxidants, quantum yields at specific wavelengths were obtained. An environmental photochemical model, GCSOLAR, also provided predictions of the fate (sunlight photolysis half-lives) of HOCI/OCl-, HOBr/OBr-, ClO2, and NH2Cl for two different seasons at latitude 40 degrees and in water with two different concentrations of chromophoric dissolved organic matter. These data are useful in assessing the environmental fate of ballast water treatment oxidants if they were to be discharged in port.