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.     

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.     

Evaluation of markers for the traceability of potato tubers grown in an organic versus conventional regime

Identification of parameters discriminating organic and conventional produce should help prevent misconduct and could provide a firm basis for comparative assessment of the two types of produce. In this report, we compare for selected markers organically versus conventionally grown tubers in four separate field trials. Within each field trial, organic and conventional tubers were subjected to the same pedoclimatic conditions as they were grown in adjacent plots. In all sites and in both cultivars tested, irrespective of environment, organic tubers exhibited a significant enrichment in ¹⁵N‰ when compared to their conventional counterparts. Also, the sum of all samples from the four sites (organic versus conventional) showed higher δ¹⁵N‰ (7.17 ± 48% versus 3.36 ± 38%; means ± CV%; n = 39; P < 0.001); furthermore, setting as threshold value for assignment in the organic group the lowest δ¹⁵N observed for organic samples (i.e. + 4.3‰), only 15% of conventional tubers were misclassified. On the other hand, further parameters selected on the basis of reports of alterations as a consequence of agricultural technique—ascorbic acid, protein content and dry matter—did not show consistent trends of variation throughout the four field trials. We conclude that, as opposed to other relevant parameters, ¹⁵N enrichment appears as a promising discriminative marker. Copyright © 2007 Society of Chemical Industry     

Grain mineral concentrations and yield of wheat grown under organic and conventional management

On the low‐P soils in southeastern Australia, organic crops differ from conventional ones primarily in the use of relatively insoluble, as opposed to soluble, P fertilisers and in the non‐use of herbicides. As organic management, particularly elimination of soluble fertilisers, is often claimed to enhance grain mineral concentrations, we examined grain from wheat on paired organic and conventional farms in two sets of experiments: (1) four pairs of commercial crops (1991–1993); and (2) fertiliser experiments on one farm pair where nil fertiliser was compared with 40 kg ha^?1 of P as either relatively insoluble reactive phosphate rock or more soluble superphosphate (1991 and 1992). All wheat was grown following a 2–6 year legume‐based pasture phase. Both conventional management and the superphosphate treatment greatly increased yields but reduced colonisation by mycorrhizal fungi. While only minor variations occurred in grain N, K, Mg, Ca, S and Fe concentrations, conventional grain had lower Zn and Cu but higher Mn and P than organic grain. These differences were ascribed to: soluble P fertilisers increasing P uptake but reducing mycorrhizal colonisation and thereby reducing Zn uptake and enhancing Mn uptake; dilution of Cu in heavier crops; and past lime applications on the organic farm decreasing Mn availability. These variations in grain minerals had nutritional implications primarily favouring the organic grain; however, organic management and, specifically, elimination of soluble fertilisers did not induce dramatic increases in grain mineral concentrations. In addition, organic management was coupled with yield reductions of 17–84 per cent due to P limitation and weeds. The impact of large regional variations in the characteristics of organic and conventional systems on the general applicability of the results from this study and other similar studies is discussed. Copyright © 2004 Society of Chemical Industry     

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).     

Determination of ascorbic and dehydroascorbic acid in lean and fatty fish species by high-performance liquid chromatography with fluorometric detection

Ascorbic acid (AA) and dehydroascorbic acid (DHAA) were analysed in fish muscle by high performance liquid chromatography (HPLC) coupled with fluorescence determination using 4,5-dimethyl-o-phenilenediamine (DMPD) as a derivative agent. The use of the DMPD in combination with isobutanol extraction eliminated many matrix interferences and increased significantly the specificity and sensitivity of the method. A strong pH dependence in the derivatization reaction was also demonstrated. Satisfactory results in terms of sensitivity, stability and reproducibility were obtained. The analyses demonstrated that the relative ratio of AA and DHAA in post-mortem fish muscle differs among fish species and seems to be related with the susceptibility to oxidation.     

Fatty acid composition of certified organic,conventional and omega-3 eggs

The objective of this study was to compare the fatty acid composition of commercially available conventional, certified organic, and omega-3 eggs. Egg components were assessed, and the fatty acid composition of yolk lipids was determined by gas chromatography. Organic egg yolk contained a higher percentage of palmitic and stearic acids than did conventional yolk (P < 0.05) with no differences observed in the monounsaturated or polyunsaturated fatty acid compositions. Compared with organic and conventional eggs, omega-3 egg yolk contained lower percentages of myristic and palmitic acids, and higher omega-3 fatty acids. In a sub-analysis of conventional egg types, the percent of stearic acid in “cage” egg yolk was significantly lower (P < 0.05) than those of “barn-laid” and “free-range” eggs. “Cage” eggs had a significantly lower percentage (P < 0.05) of arachidonic acid than had “barn-laid” eggs. Consumption of omega-3 eggs has the potential to confer health benefits through the increase in intake of omega-3 fatty acids. With regard to organic or conventional methods of production, the small differences in saturated fatty acids observed in the present study are unlikely to have any significant metabolic effect on the consumer.     

Extraction and quantification of major carotenoids in processed foods and supplements by liquid chromatography

A simple, fast and robust method with minimum steps, small sample size and amounts of solvents was developed to determine major carotenoids contents in processed foods, tablets and gel capsules. The method involves dispersion of the sample in hot water (60 °C) with added butylated hydroxytoluene (BHT) in ethanol to minimize oxidation, followed by extraction with chloroform and analysis by liquid chromatography. Chromatographic parameters were: a C30 column protected with a C18 guard cartridge; gradient elution at the rate of 1.0 mL/min starting with 100% methanol (A) and ending with 40:60 (v/v) methanol/isopropanol (B); detection set at 450 nm for carotenoids, and 325 nm for retinol, retinyl acetate and retinol palmitate. The method exhibited: (i) high degree of repeatability (%rsd); (ii) linear calibration curves (r² ? 0.9998); (iii) low detection; and quantification limits. The method was validated with standard reference material 2383 for trans-β-carotene; and tested for α-, and β-carotenes, lutein, zeaxanthin, cryptoxanthin, trans-retinol in processed foods, tablets and gel supplements.     

Antioxidant activity and profiles of common fruits in Singapore

Thirty-eight types of fruits commonly consumed in Singapore were systematically analysed for their hydrophilic oxygen radical absorbance capacity (H-ORAC), total phenolic content (TPC), ascorbic acid (AA) and various lipophilic antioxidants. Antioxidant composition and concentration varied widely across different fruits. Many of the tropical fruits tested were high in antioxidants. Amongst all fruits tested, sapodilla (Manilkara zapota) had the highest H-ORAC and TPC whilst guava had the highest AA per gram fresh weight. Papaya, red watermelon and cantaloupe had the highest β-cryptoxanthin, lycopene and β-carotene per gram fresh weight, respectively. On the other hand, durian and mangosteen were high in tocopherols and tocotrienols, respectively. Based on consumption data, Chinese Singaporeans appear to have a higher intake of carotenoids and tocopherols rich fruits compared to the US population. As fruits are a rich source of diverse antioxidants, efforts to promote consumption of a variety of fruits should be continued for public health benefits.     

Effect of an organic and conventional rearing system on the mineral content of hen eggs

In this study, the effect on mineral content of eggs from organic and conventional-housing systems was investigated. For this, random samples of 12 eggs were collected in both housing systems. Egg shells and edible portions were analysed for ash, Ca, P, Mg, Fe, Zn and Cu contents.The P and Zn contents of the edible egg portion were lower in the organic eggs than in conventional eggs. Mg content of the eggshell was higher in organic eggs while Zn content showed a marked decrease. As far as Ca, Fe and Cu values were concerned, these did not differ between the eggs from organic and conventional systems.The results showed considerable differences in mineral content between the eggs from the hens reared in organic and conventional systems.     

Comparison of high-performance liquid chromatography and spectrofluorimetry for vitamin C analysis of green beans (Phaseolus vulgaris L.)

 A spectrofluorimetric method and a chromatographic method [high-performance liquid chromatography – ultraviolet (HPLC-UV) detection] were compared for vitamin C analysis of green beans. For HPLC-UV, the determination was performed before [ascorbic acid (AA)] and after reduction with dithiothreitol [AA + dehydroascorbic acid (DHAA)]; for spectrofluorimetry, DHAA was determined after oxidation with activated charcoal. The fluorimetric determination of DHAA before oxidation was also carried out, and showed good precision but poor accuracy (very high recovery percentages). HPLC-UV showed better linearity and sensitivity, while spectrofluorimetry was more precise. Both methods were suitable for green bean samples, and the choice of which one to use depends on the particular interest of the analysis: spectrofluorimetry may be preferable when the total content of vitamin C is required, but not for individual analysis of each form. HPLC-UV is more suitable when the interest of the analysis is the ascorbic acid form as a deterioration index of vegetable products. Received: 29 March 1999 / Revised version: 12 May 1999     

Comparing the fatty acid composition of organic and conventional milk

During a 12-mo longitudinal study, bulk-tank milk was collected each month from organic (n = 17) and conventional (n = 19) dairy farms in the United Kingdom. All milk samples were analyzed for fatty acid (FA) content, with the farming system type, herd production level, and nutritional factors affecting the FA composition investigated by use of mixed model analyses. Models were constructed for saturated fatty acids, the ratio of polyunsaturated fatty acids (PUFA) to monounsaturated fatty acids, total n-3 FA, total n-6 FA, conjugated linoleic acid, and vaccenic acid. The ratio of n-6:n-3 FA in both organic and conventional milk was also compared. Organic milk had a higher proportion of PUFA to monounsaturated fatty acids and of n-3 FA than conventional milk, and contained a consistently lower n-6:n-3 FA ratio (which is considered beneficial) compared with conventional milk. There was no difference between organic and conventional milk with respect to the proportion of conjugated linoleic acid or vaccenic acid. A number of factors other than farming system were identified which affected milk FA content including month of year, herd average milk yield, breed type, use of a total mixed ration, and access to fresh grazing. Thus, organic dairy farms in the United Kingdom produce milk with a higher PUFA content, particularly n-3 FA, throughout the year. However, knowledge of the effects of season, access to fresh grazing, or use of specific silage types could be used by producers to enhance the content of beneficial FA in milk.     

A comparison of flavonoids,carotenoids and vitamin C in commercial organic and conventional marinara pasta sauce

BACKGROUND: Characterising the levels of key phytochemicals in foods commonly consumed in the Western diet is critical for database development, estimating intake and assessing the potential health benefits associated with the consumption of these products. This paper describes a market‐basket evaluation of the key flavonoids, carotenoids and vitamin C in commercial organic (five brands) and conventional (five brands) marinara pasta sauces. RESULTS: Levels of ascorbic acid ranged from undetected up to 6.87 mg per 100 g fresh weight. The levels of total vitamin C in six of the ten samples were significantly lower than the amount listed on the Nutrition Facts Panel (P < 0.001 or P < 0.01). The contents of total vitamin C, flavonoids and lycopene were not statistically different between organic and conventional samples. Conventional pasta sauces demonstrated a significantly higher level of all‐trans‐β‐carotene (P < 0.05). CONCLUSION: This suggests that any beneficial differences in levels of flavonoids, carotenoids and vitamin C gained through cultivation practices are not measurable at the consumer level in processed tomato products. Additionally, the results point to a large disparity between the actual vitamin C content of these products and the content listed on the Nutrition Facts Panel. Copyright © 2007 Society of Chemical Industry     

Screening and HPLC methods for carotenoids in sweetpotato, cassava and maize for plant breeding trials

Analytical methods for sweetpotato, cassava and maize were developed. In orange and salmon-fleshed sweetpotatoes, (all-E)-β-carotene predominated and results of spectrophotometric screening and HPLC quantification did not differ significantly. In yellow-fleshed sweetpotato and cassava, however, spectrophotometric screening overestimated the HPLC values because of the presence of several minor carotenoids. Aside from (all-E)-β-carotene, Z-isomers were present in cassava in appreciable amounts. For both crops, extraction with acetone or tetrahydrofuran:methanol (1:1), using a mortar and pestle or a Polytron homogenizer, gave equivalent results. Rehydration of dry maize at room temperature for 30 min or at 85 °C for 5, 10 or 15 min gave equivalent results. Concentrations obtained with the C18 and C30 columns did not differ significantly for zeaxanthin, lutein, β-cryptoxanthin and β-carotene in the all-E-configuration, but their Z-isomers were difficult to locate in the chromatogram obtained with the C30 column. Extraction with tetrahydrofuran:methanol (1:1) gave significantly lower results for zeaxanthin and lutein.     

Is there any difference between the phenolic content of organic and conventional tomato juices?

The present study aims to compare the phenolic and hydrophilic antioxidant profiles of organically and conventionally produced tomato juices. Comparisons of analyses of archived samples from conventional and organic production systems demonstrated statistically higher levels (P < 0.05) of phenolic compounds in organic tomato juices. This increase corresponds not only with increasing amounts of soil organic matter accumulating in organic plots but also with reduced manure application rates once soils in the organic systems had reached equilibrium levels of organic matter. Using principal component analysis, results show that phenolic compounds and hydrophilic antioxidant capacity were responsible for the differentiation between organic and conventional tomato juices. Thus, there appear to be genuine differences in the bioactive components of organic and conventional tomato juices not previously reported.     

The development and release of maize fortified with provitamin A carotenoids in developing countries

Micronutrient deficiencies have been identified as major public health problems affecting a large part of the world's population. Biofortification of staple crops like maize has been proposed as one of the most cost effective and feasible approaches to combat micronutrient deficiencies. Studies have shown that provitamin A from biofortified crops is highly bioavailable and has the capacity to improve vitamin A status of vulnerable groups. Most people in sub-Saharan Africa subsist on maize and many people may benefit from consumption of provitamin A carotenoid biofortified maize, especially women and children. With the exception of transgenic golden rice, biofortified crops have received considerable acceptance by most communities. Negative perceptions associated with yellow maize do not affect orange maize, which is, for example, well-liked in rural Zambia. With proper policy frameworks and full commercialization, provitamin A maize can address the problem of vitamin A deficiencies among poor nations with maize-based diets.     

Detection and quantification of Ochratoxin A in milk produced in organic farms

Dairy cows (as all other ruminants) possess physiological systems for mycotoxins’ detoxification. However, in organic farming practices the detoxification could be impaired because of possible higher contamination of feedstuff, changes in rumen pH and other factors. So the organic milk could be at risk in this respect. The results of an investigation on the presence of Ochratoxin A (OTA) in 63 samples of organic and 20 samples of conventional milk are reported in this paper. The quantification was carried out by means of the HPLC method described by Sørensen and Elbœk (2005). The method has been modified in the purification step so as to shorten the time of analysis and lower the cost of the assay.     

Nutritional bioactive compounds and technological aspects of minor fruits grown in Brazil

Brazil is one of the three major fruit producers in the world. Native and/or exotic Brazilian fruits have great nutritional and economic potential. Eggfruit, blackberry, Brazilian guava, atemoya, bacuri, sweetsop, starfruit, feijoa, cactus pear, fruit of wolf, breadfruit, jaboticaba, jackfruit, rose apple, lychee, mangaba and marolo are already present in the Brazilian diet, but they are not yet industrialized and are minor agricultural products. These fruits are produced and used in the manufacture of handicraft products such as jellies and sweets that are available in free markets, but production is small-scale and without safe operational procedures. These fruits are seasonal with large postharvest losses. Thus, it is necessary to initiate competitive agribusinesses in the producing regions for these fruits to enhance local economies. This review summarizes the major nutritional and bioactive compounds found in these fruits, the technological aspects of their cultivation, and future prospects for introducing consumption of these fruits and their respective products to Brazilian and/or foreign markets.