UV radiation-induced changes of antioxidant capacity of fresh-cut tropical fruits

The effect of ultraviolet (UV-C) treatment on total phenol, flavonoid, and vitamin C content of fresh-cut honey pineapple, banana “pisang mas”, and guava was investigated. The antioxidant capacity of the fruit also was evaluated by measuring its ferric reducing/antioxidant power (FRAP) and DPPH free radical-scavenging activity. The fresh-cut fruits were exposed to UV-C for 0, 10, 20, and 30 min. Total phenol and flavonoid contents of guava and banana increased significantly with the increase in treatment time. In pineapple, the increase in total phenol content was insignificant, but the flavonoid content increased significantly after 10 min of treatment. UV-C treatment decreased the vitamin C content of all three fruits. In fresh-cut banana, longer treatment time resulted in higher FRAP and DPPH values; these values remained stable throughout the experiment for fresh-cut pineapple. For fresh-cut guava, FRAP and DPPH values were stable until 30 min, after which a significant increase in FRAP values occurred.

Industrial relevance

UV irradiation processing of fresh-cut fruits leads to increase in antioxidants, polyphenols, and flavonoids. Hence, apart from the application of UV for microbial safety at industrial levels, this novel technology can also be exploited for enhancement of health promoting compounds for benefit of consumers.     

Ozone-induced changes of antioxidant capacity of fresh-cut tropical fruits

The effect of ozone treatment on total phenol, flavonoid, and vitamin C content of fresh-cut honey pineapple, banana ‘pisang mas’, and guava was investigated. The fresh-cut fruits were exposed to ozone at a flow rate of 8 ± 0.2 ml/s for 0, 10, 20, and 30 min. The antioxidant capacity of the fruits was evaluated by measuring the ferric reducing/antioxidant power (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging activity. Total phenol and flavonoid contents of pineapple and banana increased significantly when exposed to ozone for up to 20 min, with a concomitant increase in FRAP and DPPH values. The opposite was observed for guava. Ozone treatment significantly decreased the vitamin C content of all three fruits. The study shows promising results for enhancing antioxidant capacity of some fresh fruits by ozone treatment although the positive effect is compromised by a reduction in vitamin C content.Industrial relevanceThe preservation of antioxidant properties, storage stability and safety is of utmost importance in the minimally processed fresh food industry. Ozone has been looked into as an alternative sanitizing technology in the fresh produce industry. The results of this study indicate that ozone can be used in the minimally processed fresh food industry to enhance the antioxidant status of fresh-cut fruits.     

Functional potential of tropical fruits with respect to free bioactive amines

The profile and levels of 10 bioactive amines were determined in five tropical fruits, among them, pineapple, guava, papaya, mango and passion fruit. The amines were extracted from the Brazilian fruits with 1 N HCl and analyzed by ion-pair HPLC, post-column derivatization with o-phthalaldehyde and fluorimetric detection. Five amines were found in the fruits (spermidine, spermine, putrescine, serotonin and agmatine). Total amines levels varied from 0.77 mg/100 g in mango up to 7.53 mg/100 g in passion fruit. Spermidine was detected in every fruit whereas putrescine and spermine were found in most of them. Agmatine was detected in some samples of pineapple, papaya and passion fruit and serotonin was present in pineapple and passion fruit. Passion fruit is a good source of the polyamines spermidine and spermine (3.05 and 2.43 mg/100 g, respectively) and, therefore, could play an important role in growth, health, antioxidant activity and membrane permeability. Papaya is a good source of serotonin (0.99 mg/100 g), which has been associated with enabling the gut to mediate reflex activity and also with decreasing the risk of thrombosis. Histamine, a peripheral vasodilator, and the vasoconstrictors tyramine, tryptamine and phenylethylamine, as well as cadaverine were not detected in any of the fruits analyzed. Due to the diversity of amines in these fruits, they can provide different functional properties and, therefore, can be used for different nutritional needs.     

Phytochemical and antioxidant characterization of the fruit of black sapote (Diospyros digyna Jacq.)

Consumption of fruits and vegetables has been associated with a healthy state which has been attributed, in part, to their antioxidant capacity. Characterization of the bioactive compounds with antioxidant activity found in fruits cultivated in the tropic is limited. Thus, the objective of the present work was the characterization of phytochemicals and antioxidants of the fruit of black sapote (Diospyros digyna Jacq.). HPLC-DAD-Mass Spectrometry (HPLC-MS) analyses were used to identify and quantify phenolics, carotenoids and tocopherols. Total soluble phenolic content was 247.8 mg GAE/100 g fw (fresh weight). Important phenolics identified were sinapic acid, myricetin, ferulic acid, and catechin. Total carotenoid content was 399.4 ??g of ??-carotene/100 g fw, and ??-carotene and lutein were the main carotenoids identified. ??-Tocopherol concentration was 672.0 ??g/100 g dry weight. Antioxidant capacity as measured by the DPPH and FRAP assays was higher in the hydrophilic than in the lipophilic extract, and it is thought to be due mainly to the phenolic content of this fruit. Results suggest that the fruit of black sapote has an antioxidant capacity comparable to other important fruits, and its inclusion in the diet is therefore recommended.     

Phytochemical and antioxidant characterization of mamey (Pouteria sapota Jacq. H.E. Moore & Stearn) fruit

Phytochemical compounds in fruits and vegetables have gained great importance in the last few years because of the increasing evidence suggesting their antioxidant and prevention of chronic diseases. Carotenoids, phenolics, flavonoids, and vitamins E and C, are among these phytochemicals. Several fruits have been characterized so far for their antioxidant and health properties but there is still limited information on fruits from the tropic. Therefore, the objective of this study was the characterization of mamey fruit (Pouteria sapota Jacq. H. E. Moore & Stearn) with regard to their antioxidant capacity and phytochemical profile. Phenolics, carotenoids and ??-tocopherol were quantified and identified by HPLC-DAD-Mass Spectrometry (LC-MS), and DPPH and FRAP assays were used to evaluate antioxidant capacity. Hydrophilic extracts of mamey fruit showed higher antioxidant capacity than the lipophilic portion. Total soluble phenols content was 28.5 mg GAE/100 g fw, being p-hydroxybenzoic acid as the main phenolic that was identified. Total carotenoid content was 1127.9 ??g ??-carotene/100 g fw with ??-carotene being the main contributor, in addition to lutein, and violoxanthin. Concentration of ??-tocopherol was 360.0 ??g/100 g fw. Results of this study suggest that mamey fruit is a good source of carotenoids and its inclusion in the diet is recommended.     

Comparison of the antioxidant activity of two Spanish onion varieties

Phenol content and antioxidant activity of two Spanish onion varieties, namely white onion and Calçot de Valls, have been studied. White onions contained higher phenol content than Calçot onions, with values which ranged from 2.57 ± 0.51 to 6.53 ± 0.16 mg gallic acid equivalents/g dry weight (GAE/g DW) and 0.51 ± 0.22 to 2.58 ± 0.16 mg GAE/g DW, respectively, depending on the solvent used. Higher phenol content was associated with higher antioxidant capacity. White onion extracts had the highest antioxidant activity at 86.6 ± 2.97 and 29.9 ± 2.49 μmol Trolox/g DW for TEAC and FRAP assays, respectively, while the values for the Calçot variety were 17.5 ± 0.46 and 16.1 ± 0.10 μmol Trolox/g DW.     

Antioxidant stability of small fruits in postharvest storage at room and refrigerator temperatures

Strawberries (Fragaria ananassa), raspberries (Rubus idaeus) and red currants (Ribes rubrum), as well as two drupes, cherries (Prunus avium), and sour cherries (Prunus cerasus), were subjected to two storage temperatures (4 °C and 25 °C) and phytochemicals concentrations (total phenols, flavonoids and anthocyanins) as well as antioxidant capacity (DPPH, ABTS and FRAP assays) were monitored until the fruit visually spoiled. Red currants and strawberries exhibited the highest initial total phenol (TP) contents (322.40 ± 5.56 and 335.47 ± 6.12 mg GAE/100 g FW, respectively) and maintained the highest TP contents throughout storage at both temperatures. Storage of at 25 °C as opposed to 4 °C, facilitated faster spoilage of analyzed fruits. In addition, most fruits stored at 4 °C, exhibited slightly higher antioxidant activity values at the end of storage according to all three antioxidant activity assays as opposed to fruits stored at 25 °C. The dynamic evolution of antioxidant capacity at both temperatures reflected the transient changes in phytochemical composition of small fruits in storage.     

Fluctuations in the phenolic content and antioxidant capacity of dark fruit juices in refrigerated storage

The changes in total phenol content and antioxidant capacity were monitored in six industrial dark fruit juices during 29-day refrigerated storage. The initial total phenol values ranged from 1302.1 mg/L GAE (strawberry) to 1919.8 mg/L GAE (black currant) with a mean of 1573.3 mg/L GAE. All juices exhibited fluctuations in TP values with a marked increase after 48 hours in refrigerated storage, and a greater overall TP content in 5/6 studied juices after 29 days. Antioxidant capacity was evaluated using the DPPH radical scavenging assay and cyclic voltammetry (CV) and expressed as Trolox equivalent antioxidant capacity (TEAC). Black currant juice exhibited the highest TEAC values according to both CV (2.42 mM Trolox) and the DPPH assay (5.68 mM Trolox), while cranberry juice antioxidants exhibited the greatest storage stability and the smallest antioxidant capacity decrease on day 29, 20% (CV) and 15% (DPPH assay). At the end of 29-day storage 5/6 juices exhibited a significant loss in antiradical activity and all 6 juices exhibited a significant loss in TEAC derived from CV measurements. Significant linear correlation was observed between the results of CV measurements and the DPPH antiradical activity (r² = 0.62).     

Antioxidant capacity, phenolic content and vitamin C in pulp, peel and seed from 24 exotic fruits from Colombia

Twenty-four exotic Colombian fruits were evaluated for antioxidant activity and total soluble phenolics (TP) (edible part, seed and peel) and ascorbic acid content (edible part). The antioxidant activities were evaluated by ABTS (free radical-scavenging capacity) and FRAP (ferric reducing antioxidant power) methods. The ABTS, FRAP, TP and ascorbic acid values in the edible part were 3.25 to 175 ??M Trolox equiv/g fresh weight (FW), 6.29 to 144 ??M Trolox equiv/g FW, 15.7 to 1018 mg gallic acid equiv/100 g FW, and 0.53 to 257 mg ascorbic acid/100 g FW respectively. There were positive correlations between antioxidant activity (assessed by both ABTS and FRAP) and TP and ascorbic acid with the FRAP and ABTS methods. The edible part of banana passion fruits (P. tarminiana and P. mollisima) exhibited the highest values of antioxidant activity and total phenolics, while the highest level of ascorbic acid was recorded in the edible part of guava apple and cashew. The seeds with the highest values of antioxidant activity and total phenols were cashew, algarrobo, arazá and coastal sapote, while the peel of coastal sapote and algarrobo had the highest values of antioxidant activity and total phenolics. To the best of our knowledge, this paper reports the first evaluation of pulp, seed and skin of Colombian tropical fruits with a view to their knowledge utilization for the development of novel functional food products.     

Phytochemicals,vitamin C and sugar content of Thai wild fruits

The objective of the present study was to generate information about the potential health-enhancing properties of selected Thai wild fruits. Nineteen varieties of wild fruits, collected from the natural forest in north-eastern Thailand, were analysed for phytochemicals, anti-oxidant activity, vitamin C and sugar content. The results showed that Diospyros decandra Lour. exhibited the highest content of total phenolic compounds (215 mg GAE/g) and total flavonoid content (187 mg RE/g). Terminalia chebula Retz. had higher anti-oxidant activities than other fruits, as measured by 1,1-diphenyl-2-picrylhydrazyl radical scavenging (99% inhibition) and ferric reducing/anti-oxidant power assays (63 mmol FeSO₄/g). The sum of sugars (sucrose, glucose, fructose and galactose) ranged from 33 to 430 mg/g fresh weight, being dominated by glucose (ranging from 7.5 to 244 mg/g) and fructose (ranging from 5.3 to 193 mg/g). The highest content of vitamin C was found in Phyllanthus emblica Linn. (2.2 mg/g). Thai wild fruits, which were investigated in this study, have been shown to be a novel rich source of phytochemicals.     

Changes in bioactive compounds and antioxidant capacity of fresh-cut cashew apple

In this study, ascorbic acid, total polyphenols and proanthocyanidins of fresh-cut cashew apple were quantified. Antioxidant capacity was determined in whole juice and in polyphenols extracts by three methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and ??-carotene bleaching. Effect of cutting and storage for 24 h at 2 °C, 27 °C and 40 °C on these compounds were also evaluated. Cashew apple presented 163 mg of ascorbic acid per 100 g of fresh weight (FW). Soluble and hydrolysable polyphenols contents were 12.79 mg GAE/100 g FW and 18.53 mg GAE/100 g FW and proanthocyanidins were 9.27 mg/100 g FW. Antioxidant capacity of juice and polyphenols extract was high for DPPH method. Storage temperatures affected bioactive compounds on cut cashew apple. The content of ascorbic acid decreased in all temperatures. Proanthocyanidins were more sensitive to 40 °C than to other temperatures. The content of polyphenols and antioxidant capacity of juice by DPPH assay did not change. However, the reducing power was lower in samples kept at high temperatures. A strong positive correlation between ascorbic acid and FRAP (r = 0.99) and a negative correlation between DPPH and FRAP (r = − 0.79) were observed. No correlations were found between polyphenols and antioxidant capacity indicating the importance of phenolic composition in the extracts. The results confirm the importance of temperature and injury on the quality of cashew apple.     

Antioxidant activity of three edible seaweeds from two areas in South East Asia

Total phenolic content (TPC) and antioxidant activity (AOA) of 50% aqueous methanol extracts of the marine algae, Padina antillarum, Caulerpa racemosa and Kappaphycus alvarezzi were studied. TPC was measured using Folin-Ciocalteu method while 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), ferrous ion chelating (FIC) assay and beta carotene bleaching (BCB) assay were used to study their AOA. P. antillarum was found to have the highest TPC, 2430±208 mg gallic acid equivalents (GAE) per 100 g dried sample and ascorbic acid equivalent antioxidant capacity (AEAC), 1140±85 mg AA/100 g. C. racemosa and K. alvarezzi displayed lower TPC and AEAC. C. racemosa had 144±22 mg GAE/100 g dried sample of TPC and 14.3±2.0 mg AA/100 g of AEAC, while K. alvarezzi had 115±35 mg/100 g dried sample of TPC and 37.8±16.8 mg AA/100 g of AEAC. In addition, P. antillarum displayed the highest reducing power, 15.7±2.6 mg GAE/g and highest chelating ability. C. racemosa and K. alvarezzi exhibited lower reducing power, 0.737±0.423 mg GAE/g and 0.561±0.269 mg GAE/g, and lower chelating ability. However, the AOA of these three seaweeds as assessed by BCB assay were equally high.     

Nutrients and bioactive compounds of Thai indigenous fruits

This study determined the nutritional potential of Thai indigenous fruits in terms of nutrients, bioactive compounds, and antioxidant activities. Three indigenous fruits were collected at two conservation areas in Kanchanaburi province, Thailand. The results showed that Phyllanthus emblica L. exhibited the highest levels of vitamin C (575 ± 452 mg/100 g), total phenolics (TP) (3703 ± 1244 mGAE/100 g), and antioxidant activities, as measured by DPPH, FRAP and ORAC assays. Compared to the other two fruits, Antidesma velutinosum Blume contained higher levels of most nutrients and dietary fibre (15.6 ± 5.9 g/100 g), as well as carotenoids (335 ± 98 μg/100 g) and phytosterols (22.1 ± 3.9 mg/100 g). Spondias pinnata (L.f.) Kurz was high in total phenolics (3178 ± 887 mGAE/100 g) and antioxidant activity. Moreover, high correlations were found between TP and antioxidant activities (r > 0.9). These Thai indigenous fruits are potentially good sources of nutrients, bioactive compounds, and antioxidant activities. Conservation and utilisation should be promoted for food security and consumption as part of a healthy diet.     

Chemical, technological and in vitro antioxidant properties of mango, guava, pineapple and passion fruit dietary fibre concentrate

The aim of this work was to determine the chemical, technological and in vitro antioxidant properties of co-products from the industrialisation of some tropical exotic fruits, such as mango, pineapple, guava and passion fruit, and to evaluate their potential use as dietary fibre sources for food enrichment. Proximate compositions were determined, as well as the total, insoluble and soluble fibre contents. The water holding, oil holding and swelling capacities were also determined. For the antioxidant activity, three different test systems were used (ABTS, DPPH and FRAP). The dietary fibre content of the co-products varied in a range between 69.1 and 81.5g/100g on a dry matter basis with a good balanced ratio between insoluble dietary fibre and soluble dietary fibre. Phenol recovery was dependent on the fruit type and the solvent system used. Methanol:acetone was a more efficient solvent for extracting phenols than ethanol. There was a good correlation between total phenol content and antioxidant capacity of the fruit extracts. All samples analysed had good antioxidant capacity. The results of this study indicate that exotic fruit fibres obtained as co-products in the process to obtain juice may be considered a good source of natural compounds with significant antioxidant activity.     

Antioxidant capacity of medicinal plants from the Province of Córdoba (Argentina) and their in vitro testing in a model food system

The total phenols content (Folin–Ciocalteau assay) and antioxidant capacity (ferric reducing/antioxidant power – FRAP) of 41 plants from Córdoba (Argentina) were analyzed. Phenol content ranged from 8.2 to 100.2 mg GAE/g. FRAP ranged from 85.2 to 1862.0 μmol of Fe(II)/g. Capparis atamisguea had the lowest values of total phenols content and antioxidant capacity (8.2 mg GAE/g and 85.2 μmol of Fe(II)/g, respectively), while Ligaria cuneifolia exhibited the highest values (100.2 mg GAE/g and 1862.0 μmol of Fe(II)/g, respectively). A significant linear correlation (p < 0.05) was found (0.9125) between phenols content and antioxidant capacity. Results support the idea that these plants may be a good source of natural antioxidants for food applications. Plants from the Asteraceae family (the most representative of the Córdoba flora) were further tested for their DPPH radical scavenging activity. Some plant extracts were tested in a simple food system to investigate to their potential use in foods.     

Effect of solvent and extraction temperatures on the antioxidant potential of traditional stoned table olives “alcaparras”

This paper reports the first approach to the antioxidant potential evaluation of traditional stoned table olives “alcaparras”. This kind of olives are largely produced and consumed in Trás-os-Montes region (Northeast of Portugal). Different solvents and temperature extraction conditions were employed in order to achieve the best method to obtain phenolic compounds and a higher antioxidant activity. The optimum method (water at boiling temperature) was applied on 10 samples from the traditional market. The total phenol content ranged between 5.58 mg gallic acid equivalents (GAE)/g and 29.88 mg GAE/g and effective concentration (EC₅₀) values were in the range 0.36-1.64 and 0.34-1.72 mg/mL for reducing power and radical scavenging effect, respectively. A significantly negative linear regression was observed between the total phenol content found in the samples and its antioxidant activity.     

Determination of free phenolic acids and antioxidant activity of methanolic extracts obtained from fruits and leaves of Chenopodium album

In this study, determination of phenolic acids as well as investigation of antioxidant activity of methanolic extracts from the fruits and leaves of Chenopodium album is described. Extracts were subjected to acidic hydrolysis in order to obtain total free phenolic acids. However, some of phenolic acids were identified and quantified by HPLC-DAD. The results were confirmed by LC-MS equipped with MS-ESI. In addition, Folin–Ciocalteu method was applied to determine the total phenolic contents. The antioxidant activity of C. album extracts was examined by using DPPH and hydroxyl radical-scavenging activity assays. Results revealed that the leaves extract exhibits better performance in antioxidant assays and in the higher total phenolic contents (3066 mg of GAE/100 g) when compared to fruits extract (1385 mg of GAE/100 g). From these results it has been revealed that the methanolic extracts of C. album from fruits and leaves have great potential as a source for natural health products.     

Honey flavonoids as protection agents against oxidative damage to human red blood cells

Honey phenol extracts separated on the base of their hydrophobicity were evaluated for the antioxidant content and for the ability to inhibit oxidative damage induced by radical species generated in the water phase or in the membrane of human erythrocytes. The water and ether fractions obtained from crude methanol extract of honey exhibited a phenolic content of 5.33 and 2.62 mg caffeic acid equivalents/100 g honey, respectively. These values correlate well with those of total antioxidant power, as assessed by FRAP assay (37.67 vs. 10.65 μmol/100 g honey). Flavonoid contents were 2.57 and 1.64 mg catechin equivalents/100 g honey for ether and water fractions, respectively. Although both honey fractions protect erythrocytes against 2,2′-azobis(2-amidinopropane)dihydrochloride-induced lysis, only the ether fraction was found to be active in inhibiting hemolysis but not methemoglobin and ferrylhemoglobin formation caused by H₂O₂. In addition, the ether fraction prevents tert-butylhydroperoxide-induced lipid peroxidation in whole erythrocytes and in isolated membranes. The significant antioxidant effect against damages induced by both water-soluble and hydrophobic exogenous oxidants suggests that the ether fraction, owing to its lipophilic character, can interact with red blood cell membrane, and the protective effect can be associated with the binding of the flavonoids to the membrane. On the other hand, the water fraction is more hydrophilic than ether fraction and it acts only from the outside of the membrane by scavenging the radicals before they attack the erythrocyte membrane.     

Determination of total phenolic and flavonoid contents in selected fruits and vegetables,as well as their stimulatory effects on mouse splenocyte proliferation

This study selected 13 fruits and vegetables to determine their total phenolic and flavonoid contents and their stimulatory effects on splenocyte proliferation from female BALB/c mice. The highest total phenolic content was observed in mulberry (1515.9 ± 5.7 mg gallic acid equivalents (GAE)/100 g fresh matter (FM)) among four selected fruit species. The highest total phenolic content was observed in a variety of red onions (310.8 ± 4.9 mg GAE/100 g FM) among nine selected vegetable species. The highest total flavonoid content was observed in mulberry (250.1 ± 6.3 mg quercetin equivalents (QE)/100 g FM) among the selected fruits. The highest total flavonoid content was observed in ceylon spinach (133.1 ± 26.2 mg QE/100 g FM) among the selected vegetables. The mulberry, strawberry and red onion demonstrated an immuno-modulatory potential via stimulating splenocyte proliferation. Bitter melon showed a significantly (P < 0.05) negative correlation with splenocyte proliferation. Their immuno-modulatory components are highly correlated with phenolics, including flavonoids. The total phenolic contents in all selected fruits and vegetables significantly correlated with splenocyte proliferation in vitro.     

Characterisation of various grape seed oils by volatile compounds,triacylglycerol composition,total phenols and antioxidant capacity

Grape seed oil (Oleum vitis viniferae) representing a promising plant fat, mainly used for culinary and pharmaceutical purposes as well as for various technical applications, was subject of the present investigation. HS-SPME-GC–MS was applied to study volatile compounds in several seed oil samples from different grape oils. The triacylglycerol (TAG) composition of these oils was analyzed by MALDI-TOF-MS/MS. In addition the total phenol content and the antioxidant capacity (using TEAC) of these oils were determined. The headspace of virgin grape oils from white and red grapes was dominated by ethyl octanoate (up to 27.5% related to the total level of volatiles), ethylacetate (up to 25.0%), ethanol (up to 22.7%), acetic acid (up to 17.2%), ethyl hexanoate (up to 17.4%) and 3-methylbutanol (up to 11.0%). Triacylglycerol composition was found to be dominated by LLL (up to 41.8%), LLP (up to 24.3%), LLO (up to 16.3%) and LOO (up to 11.7%), followed by LOP (up to 9.3%) and LOS/OOO (up to 4.3%). Total phenol content ranged between 59 μg/g and 115.5 μg/g GAE. Antioxidant capacity (TEAC) was analyzed to range between 0.09 μg/g and 1.16 μg/g.