Alterations of vitamin C, total phenolics, and antioxidant capacity as affected by processing tomatoes to different products

This study was conducted to investigate the antioxidant vitamin C, the polyphenol content, and the hydrophilic antioxidant capacity of tomato juice, baked tomatoes, tomato sauce, and tomato soup. During the production of tomato juice and during the preparation of the other tomato products, samples were taken after different times, respectively, after each particular production step. High-performance liquid chromatography was used to determine the content of vitamin C. The total phenolics content was analyzed spectrophotometrically by using the Folin-Ciocalteu method. The hydrophilic antioxidant capacity was measured by using three different methods: the Trolox equivalent antioxidant capacity assay, the ferric reducing antioxidant power test, and the photochemiluminescence assay. The vitamin C contents of the tomato products decreased during the thermal processing of tomatoes. In contrast, the total phenolics concentration and the water soluble antioxidant capacity increased.     

Processing strawberries to different products alters contents of vitamin C, total phenolics, total anthocyanins, and antioxidant capacity

Strawberries were processed to juice, nectar, wine, and puree. For investigation of the antioxidant capacity as well as the contents of ascorbic acid, total phenolics and total anthocyanins, samples were taken after different stages of production to determine the effects of processing. The content of vitamin C was measured spectrophotometrically. The total phenolic content was analyzed by using the Folin-Ciocalteu method, and the amount of total anthocyanins was determined by using the pH-differential method. Two different methods-the trolox equivalent antioxidant capacity assay and the ferric reducing antioxidant power test-were used to determine the hydrophilic antioxidant capacity. This study showed the decrease of all investigated parameters within processing strawberries to different products. The content of ascorbic acid decreased with production time and processing steps, especially during heat treatment. The investigations on total phenolics in strawberry products proved fining to be a mild method to clarify berry juices and wines without removing high amounts of total phenolics. Fermentation did not lead to heavy losses of total phenolics, probably due to polymerization and condensation of monomer phenolics such as anthocyanins. Total anthocyanins and the hydrophilic antioxidant capacity decreased while using high temperatures. Anthocyanins also decreased considerably during the processing of wines, mainly caused by fermentation and pasteurization.     

Influence of cultivar, harvest time, storage conditions, and peeling on the antioxidant capacity and phenolic and ascorbic acid contents of apples and pears

Apple and pear fruits are important sources of secondary plant metabolites and one of the major sources of dietary phenolics consumed all year round. The aim of this work was to identify the main variables influencing phenolic content and antioxidant capacity in apples. Higher phenolic and antioxidant contents were observed in some varieties (such as the Delbar Estival apple and Durondeau pear). Storage conditions were important. Our results also showed that fruits should be consumed rapidly after purchase and with their peel. After one week of domestic storage, the ascorbic acid content was found to decrease by 75%. Peeling led to a more than 25% decrease in total phenolics and ascorbic acid. The harvest time (at normal ripeness) had only a limited impact, but significant year-to-year variations were observed. In conclusion, well-chosen and well-stored apples and pears may contribute to an antioxidant-rich diet if consumed rapidly and with their peel.     

Lycopene, vitamin C, and antioxidant capacity of tomato juice as affected by high-intensity pulsed electric fields critical parameters

The effects of high-intensity pulsed electric field (HIPEF) treatment variables (frequency, pulse width, and pulse polarity) on the lycopene, vitamin C, and antioxidant capacities of tomato juice were evaluated using a response surface methodology. An optimization of the HIPEF treatment conditions was carried out to obtain tomato juice with the highest content of bioactive compounds possible. Samples were subjected to an electric field intensity set at 35 kV/cm for 1000 micros using squared wave pulses, frequencies from 50 to 250 Hz, and a pulse width from 1 to 7 micros, in monopolar or bipolar mode. Data significantly fit (P < 0.001) the proposed second-order response functions. Pulse frequency, width, and polarity significantly affected the lycopene, vitamin C, and antioxidant capacities of HIPEF-treated tomato juice. Maximal relative lycopene content (131.8%), vitamin C content (90.2%), and antioxidant capacity retention (89.4%) were attained with HIPEF treatments of a 1 micros pulse duration applied at 250 Hz in bipolar mode. Therefore, the application of HIPEF may be appropriate to achieve nutritious tomato juice.     

Antioxidant capacity, vitamin C, phenolics, and anthocyanins after fresh storage of small fruits.

Fresh strawberries (Fragaria x ananassa Duch.), raspberries (Rubus idaeus Michx.), highbush blueberries (Vaccinium corymbosum L.), and lowbush blueberries (Vaccinium angustifolium Aiton) were stored at 0, 10, 20, and 30 degrees C for up to 8 days to determine the effects of storage temperature on whole fruit antioxidant capacity (as measured by the oxygen radical absorbing capacity assay, Cao et al., Clin. Chem. 1995, 41, 1738-1744) and total phenolic, anthocyanin, and ascorbate content. The four fruit varied markedly in their total antioxidant capacity, and antioxidant capacity was strongly correlated with the content of total phenolics (0.83) and anthocyanins (0.90). The antioxidant capacity of the two blueberry species was about 3-fold higher than either strawberries or raspberries. However, there was an increase in the antioxidant capacity of strawberries and raspberries during storage at temperatures >0 degrees C, which was accompanied by increases in anthocyanins in strawberries and increases in anthocyanins and total phenolics in raspberries. Ascorbate content differed more than 5-fold among the four fruit species; on average, strawberries and raspberries had almost 4-times more ascorbate than highbush and lowbush blueberries. There were no ascorbate losses in strawberries or highbush blueberries during 8 days of storage at the various temperatures, but there were losses in the other two fruit species. Ascorbate made only a small contribution (0.4-9.4%) to the total antioxidant capacity of the fruit. The increase observed in antioxidant capacity through postharvest phenolic synthesis and metabolism suggested that commercially feasible technologies may be developed to enhance the health functionality of small fruit crops.     

Antioxidant capacities,phenolic compounds,carotenoids, and vitamin C contents of nectarine,peach, and plum cultivars from California

Genotypic variation in composition and antioxidant activity was evaluated using 25 cultivars, 5 each of white-flesh nectarines, yellow-flesh nectarines, white-flesh peaches, yellow-flesh peaches, and plums, at the ripe (ready-to-eat) stage. The ranges of total ascorbic acid (vitamin C) (in mg/100 g of fresh weight) were 5-14 (white-flesh nectarines), 6-8 (yellow-flesh nectarines), 6-9 (white-flesh peaches), 4-13 (yellow-flesh peaches), and 3-10 (plums). Total carotenoids concentrations (in microg/100 g of fresh weight) were 7-14 (white-flesh nectarines), 80-186 (yellow-flesh nectarines), 7-20 (white-flesh peaches), 71-210 (yellow-flesh peaches), and 70-260 (plums). Total phenolics (in mg/100 g of fresh weight) were 14-102 (white-flesh nectarines), 18-54 (yellow-flesh nectarines), 28-111 (white-flesh peaches), 21-61 (yellow-flesh peaches), and 42-109 (plums). The contributions of phenolic compounds to antioxidant activity were much greater than those of vitamin C and carotenoids. There was a strong correlation (0.93-0.96) between total phenolics and antioxidant activity of nectarines, peaches, and plums.     

Oxygen radical absorbance capacity (ORAC) and phenolic and anthocyanin concentrations in fruit and leaf tissues of highbush blueberry

Antioxidant capacity, as measured by oxygen radical absorbance capacity (ORAC), and total phenolic and total anthocyanin contents were evaluated in fruit tissues of 87 highbush blueberry (Vacciniumcorymbosum L.) and species-introgressed highbush blueberry cultivars. ORAC and phenolic levels were evaluated in leaf tissues of the same materials. Average values for ORAC, phenolics, and anthocyanins in fruit were 15.9 ORAC units, 1.79 mg/g (gallic acid equivalents), and 0.95 mg/g (cyanidin-3-glucoside equivalents), respectively. Cv. Rubel had the highest ORAC per gram of fresh weight values, at 31.1 units, and cv. Elliott had the highest values on the basis of ORAC per square centimeter of surface area. In leaf tissue, values for both ORAC and phenolics were significantly higher than in fruit tissue, with mean values of 490 ORAC units and 44.80 mg/g (gallic acid equivalents), respectively. Leaf ORAC had a low, but significant, correlation with fruit phenolics and anthocyanins, but not with fruit ORAC. An analysis of ORAC values versus calculated midparent values in 11 plants from the 87-cultivar group in which all parents were tested suggested that, across cultivars, ORAC inheritance is additive. An investigation of ORAC values in a family of 44 cv. Rubel x Duke seedlings showed negative epistasis for ORAC values, suggesting Rubel may have gene combinations contributing to ORAC that are broken up during hybridization.     

Effect of genotype and storage time on stability of colour,phenolic compounds and ascorbic acid in red raspberry (Rubus idaeus L.) jams

Changes in colour, phenolic composition and ascorbic acid (AA) concentrations in jams made from eight, floricane fruiting, red raspberry genotypes stored for six months at 20°C were investigated. Additionally, the relationship between genotypes and quality parameters was assessed. On average for all genotypes, 83% AA degradation was observed during the first three months of storage. After six months, the concentrations of anthocyanins, total quercetin glycosides and lambertianin C decreased by 80%, 13% and 7%, while ellagic acid conjugates and total phenolics increased by 47% and 8%, respectively. The anthocyanins detected in highest concentrations in fresh jams, that is, cyanidin-3-(2^g-glucosylrutinoside), cyanidin-3-sophoroside, cyanidin-3-glucoside and cyanidin-3-rutinoside showed the highest stability during storage, that is, 28%, 21%, 12% and 11% left after six months of storage, respectively. A significant decrease in colour (lightness, chroma and hue) was also observed during storage. The colour changes of stored jams, however, were much slower than the pigment degradation. On average, lightness, chroma and hue decreased by 13%, 29% and 18% during six months of storage, respectively. The lowest anthocyanin degradation was observed in jams characterised by red-bluish colour and high initial anthocyanin content, that is, ‘Veten’, ‘RU024 01003’ and ‘RU974 07002’ with 72–78% degradation after storage for six months, while the highest losses (82–93%) were observed in jams characterised by saturated red-orange colour, high ellagitanin and low initial anthocyanin contents, that is, ‘Glen Magna’, ‘Malling Hestia’ and ‘Octavia’. The results indicate that the genotypes ‘RU024 01003’ and ‘RU974 07002’ might have the potential to replace ‘Veten’, the main cultivar for jam processing in Norway, as new cultivars for industrial processing provided good cultivation qualities and satisfactory taste and flavour of the products.     

Peroxyl radical scavenging capacity, polyphenolics, and lipophilic antioxidant profiles of mulberry fruits cultivated in southern China

Twenty-seven cultivars of mulberry fruits ( Morus atropurpurea Roxb) were analyzed for their total phenolic content, total anthocyanin content, and peroxyl radical scavenging capacities. The proanthocyanidin contents of the fruit were also quantified using 4-dimethylamino-cinnamaldehyde assay, and characterization was attempted using electrospray ionization mass spectra. The phenolic compounds of mulberry fruits were characterized using HPLC with ESI-MS and diode array detection. Results showed that the content of mulberry fruits varied with different cultivars with total phenolic content, total anthocyanin content, total proanthocyanidin content, and peroxyl radical scavenging capacities ranging from 0.060-0.244, 0.001-0.056, 0.001-0.015, and 0.301-1.728, respectively. Good correlations were observed among the phenolic, anthocyanin, and proanthocyanidin contents and the radical scavenging capacities of mulberry fruits. Mulberry fruits were found to contain low amount of proanthocyanidins. The high total phenolic content of mulberry fruits were mainly contributed by anthocyanins, rutin, and chlorogenic acids. The lipid soluble antioxidants are profiled by an HPLC method developed in-house, and the results of selected mulberry fruits revealed significant amounts of lutein and delta- and gamma-tocopherols but low alpha-tocopherol. Our results provide useful antioxidant nutritional information of a mulberry cultivar that has potential for large scale plantations.     

Determining the potential to breed for enhanced antioxidant status in Malus: mean inter- and intravarietal fruit vitamin C and glutathione contents at harvest and their evolution during storage

Vitamin C (L-ascorbate, L-ascorbic acid; L-AA) and glutathione (GSH) are major hydrophilic antioxidants in plants with important roles in stress resistance and nutrition. To evaluate the potential for breeding for enhanced levels of these compounds, a comprehensive screen of the fruit from some 31 apple (Malus) cultivars has been carried out to determine the biodiversity present in the mean inter- and intracultivar concentrations of both the oxidized and reduced forms of these compounds, as well as the impact of storage on their concentrations. It is noted that despite limited variation at harvest, cultivars differed substantially in their ability to maintain L-AA levels during storage, primarily due to the loss of L-AA by "low-vitamin C" cultivars. Generally, cultivars that could maintain their L-AA and GSH pools also had better storage properties. Interestingly, there was also a correlation between fruit vitamin C contents and the harvest date, such that cultivars with the highest vitamin C contents were harvested latest in the season and the lowest contents were found among the early varieties. Correlations with other physiological parameters, however, were too weak to serve as useful predictive tools.     

Changes in water-soluble vitamins and antioxidant capacity of fruit juice-milk beverages as affected by high-intensity pulsed electric fields (HIPEF) or heat during chilled storage

The effect of high-intensity pulsed electric fields (HIPEF) or thermal processes and refrigerated storage on water-soluble vitamins and antioxidant capacity of beverages containing fruit juices and whole (FJ-WM) or skim milk (FJ-SM) was assessed. Peroxidase (POD) and lipoxygenase (LOX) inactivation as well as color changes were also studied. High vitamin C retention was observed in HIPEF and thermally treated beverages, but a significant depletion of the vitamin during storage occurred, which was correlated with antioxidant capacity. HIPEF treatment did not affect the concentration of group B vitamins, which also remained constant over time, but thermally treated beverages showed lower riboflavin (vitamin B2) concentration. With regard to enzyme activity, thermal processing was more effective than HIPEF on POD and LOX inactivation. The color of the beverages was maintained after HIPEF processing and during storage. Consequently, HIPEF processing could be a feasible technology to attain beverages with fruit juices and milk with high vitamin content and antioxidant potential.     

Liquid chromatography, microfluorometry, and dye-titration determination of vitamin C in fresh fruit and vegetables

The vitamin C content of several fresh fruit and vegetables was determined by a liquid chromatographic (LC) method which gave simultaneous separate values for ascorbic acid and dehydroascorbic acid (DHA) and by the official AOAC methods of microfluorometry and dye-titration. The levels of ascorbic acid obtained by LC and dye-titration were in good agreement, except for a few colored products where it was difficult to determine the end point of the titration. The combined values for ascorbic acid and DHA obtained by LC and microfluorometry were in agreement for most produce, but for about one-third of the samples, the values obtained by microfluorometry were significantly higher.     

Ascorbic acid, carotenoids, and visual quality of baby spinach as affected by shade netting and postharvest storage

Baby spinach ( Spinacia oleracea L.) was grown under three types of shade netting (high transmittance, spectrum-altering, and low transmittance) to study the effect on the concentrations of vitamin C (ascorbic acid and dehydroascorbic acid), carotenoids, and chlorophyll and on the visual quality of the leaves. The spinach was sown in April and August and harvested at two growth stages. After harvest, leaves were stored in polypropylene bags at 2 and 10 degrees C. Shading significantly decreased the ascorbic acid concentration of April-sown spinach by 12-33%, but in the August-sown spinach, the response was inconsistent. Concentrations of total carotenoids and total chlorophylls were significantly higher under the nettings in many cases, especially under the spectrum-altering and low-transmittance nettings. Postharvest visual quality and postharvest persistence of the compounds analyzed were not greatly affected by shading. We conclude that these shade nettings are acceptable to use in baby spinach production when it comes to the studied aspects of internal and external quality of the produce.     

Flavone C-glycoside,phenolic acid,and nitrogen contents in leaves of barley subject to organic fertilization treatments

From the leaves of barley, Hordeum vulgare, one new flavone C-glucoside and three known flavone glucosides were isolated and characterized by (1)H and (13)C NMR and MALDI-TOF-MS. The novel flavone C-glucoside was isovitexin 7-O-beta-[6' "-O-(E)-p-coumaroyl]glucoside (6' "-coumaroylsaponarin), and the known compounds were isovitexin 7-O-beta-[6' "-O-(E)-feruloyl]glucoside, isoorientin 7-O-beta-[6' "-O-(E)-feruloyl]glucoside, and tricin 7-O-beta-glucoside. The sum of all the flavone glycosides and soluble phenolic acids in the leaves decreased with increased rate of plant nutrients given in animal manure and with increased crop yield. All of the major phenylpropanoids showed the same general response to nutrient level. The concentration of nitrogen in the leaves was not directly related to nutrient application or to contents of phenylpropanoids.     

南果梨糖、酸度近红外光谱模型适用的贮藏期研究

为确定南果梨糖、酸度可见-近红外光谱模型对不同贮藏期南果梨的适用性和适用时间,进行了贮藏期间南果梨糖、酸度和光谱变化的方差分析,利用偏最小二乘法（PLS）法建立采后6 d的南果梨糖、酸度模型,并分析所建模型对不同贮藏期间样品的预测性能,试验结果表明：常温条件下采后18 d内南果梨糖、酸含量和光谱的变化趋势一致,而冷藏条件下120 d内糖、酸含量和光谱的变化趋势不完全一致;但采后6 d所建立的糖、酸度模型校正相关系数均高于0.83,模型对常温下采后12 d内、采后冷藏120 d内的样品预测相关系数均在0.80以上,表明模型能满足一定贮藏时期内样品的预测要求,为南果梨近红外分级技术的应用提供了依据。     

Kinetic study of anthocyanins, vitamin C, and antioxidant capacity in strawberry juices treated by high-intensity pulsed electric fields

A kinetic study of anthocyanins, vitamin C, and antioxidant capacity was carried out in strawberry juice treated with high-intensity pulsed electric fields. Samples were subjected to electric field strengths from 20 to 35 kV/cm for up to 2000 mus applying 1 mus bipolar pulses at 232 Hz. The suitability of simple first-order kinetics and an empirical model based on Weibull distribution function to describe changes in experimental data are discussed. In addition, different secondary models relating the antioxidant property retention to the electric field strength and treatment time are given. The Weibull kinetic model was the most accurate ( R (2) adj >or= 0.727) to predict anthocyanins, vitamin C, and antioxidant capacity changes in strawberry juice through the HIPEF treatment time. The combined effect of treatment time and electric field strength on health-related compounds of strawberry juice was successfully predicted (R(2) adj >or= 0.874) through secondary expressions. The proposed models are useful to predict the variation of the antioxidant potential of strawberry juice with the key parameters involved in HIPEF treatments.     

Separation,characterization, and quantitation of benzoic and phenolic antioxidants in American cranberry fruit by GC-MS

A GC-MS method is reported for separation and characterization of widely different amounts of benzoic and phenolic acids as their trimethylsilyl derivatives simultaneously in cranberry. Fifteen benzoic and phenolic acids (benzoic, o-hydroxybenzoic, cinnamic, m-hydroxybenzoic, p-hydroxybenzoic, p-hydroxyphenyl acetic, phthalic, 2,3-dihydroxybenzoic, vanillic, o-hydroxycinnamic, 2,4-dihydroxybenzoic, p-coumaric, ferulic, caffeic, and sinapic acid) were identified in cranberry fruit in their free and bound forms on the basis of GC retention times and simultaneously recorded mass spectra. Except for benzoic, p-coumaric, caffeic, ferulic, and sinapic acids, 10 other phenolic acids identified have not been reported in cranberry before. The quantitation of the identified components was based on total ion current (TIC). The experimental results indicated cranberry fruit contains a high content of benzoic and phenolic acids (5.7 g/kg fresh weight) with benzoic acid being the most abundant (4.7 g/kg fresh weight). The next most abundant are p-coumaric (0.25 g/kg fresh weight) and sinapic (0.21 g/kg fresh weight) acid. Benzoic and phenolic acids occur mainly in bound forms and only about 10% occurs as free acid.     

Changes in microbial C,N, P and ATP contents,numbers and respiration on storage of soil

The effects of a 7-day incubation (at 25°C and 50% of water-holding capacity, −0.001 MPa) of two soils, from under grazed pastures of high and low P status, on microbial C, N, P and ATP contents, numbers, and respiration were investigated with samples collected in summer and winter. Incubation prior to analysis (i.e. storage or pre-incubation) resulted in a significant (P < 0.05) alteration in most of the properties measured; seasonal effects were often marked with the two soils generally behaving similarly. Microbial numbers and respiration increased during prior incubation of summer samples, but generally decreased in winter samples. Pre-incubation resulted in a decrease in biomass C, as estimated by the chloroform fumigation procedure, but an increase in ATP content. Changes in mineral-N flush and biomass P were smaller and less consistent. Many of the properties measured were still changing after 7 days incubation.     

Eggplant dry matter composition fruit yield and quality as affected by phosphate and total salinity caused by potassium fertilizers in the irrigation solution

Eggplant (Solanum melongena L.) grown under winter conditions in unheated polyethylene covered greenhouse displays unmarketable red color fruit skin. The purpose of this work was to study the effect of potassium (K), phosphate and total salinity levels in the irrigation solution on the quality of eggplant fruit grown at winter and spring seasons. Eggplant was grown in containers filled with basalt erupted tuff scoria. The fertigation solutions were composed of three levels of P: 18, 36, and 54 g P m^‐3, using mono K phosphate (MKP). Each level of P was applied on two levels of total K concentrations, 475 and 920 g K m^‐3 composed of K nitrate, MKP, and K chloride (KCl). The KNO₃ fertilizer was used in all treatments at 150 g N m^‐3. Increasing the KCl concentration increased the average electrical conductivity (EC) in the irrigation solution from 2.3 to 3.9 dS m^‐1, reduced class A fruit number and weight, but had no effect on the skin color. During the cold winter period the intensity of the skin color was weaker than in the normal hot growing period. Increasing the average phosphorus (P) concentration in the irrigation solution throughout the growing season from 36 to 54 g m^‐3 increased the number of fruit per plant, the number of class A fruits but has no significant effect on total fruit yield. Increasing the total electrical conductivity of the nutrient solutions by K fertilizers above 3.8 dS m^‐1 decreased fruit yield and total dry matter in the spring growth period.     

钾对日光温室黄瓜糖、维生素C、硝酸盐及其相关酶活性的影响

以津优1号为试材,设K2O施用量分别为0、300、6009、00、1200.kg/hm2.5个处理,研究了不同施钾水平对黄瓜主要品质和有关酶活性的影响。结果表明,在施K2O.300～900.kg/hm2范围内,随着用量的增加,黄瓜叶片和果实中可溶性糖含量与SPS活性均逐渐升高,而K2O用量达1200.kg/hm2时,二者趋于下降。果实中的可溶性糖含量与叶片和果实SPS活性呈显著正相关;而叶片中糖含量与其SPS活性没有明显的相关性。在K2O用量为300～900kg/hm2时,黄瓜果实的Vc含量高于对照,叶片APX活性降低,而果实中的APX活性提高。黄瓜叶片与果实的硝酸盐含量均随施钾量的增加而逐渐降低,K2O用量在0～900.kg/hm2范围内,黄瓜叶片的NR活性较高,且随着钾肥用量的增加而升高;当K2O用量达到1200.kg/hm2时,NR活性明显下降,果实中的NR活性很低,处理间差异不显著。