Residues of grape (Vitis vinifera L.) seed oil production as a valuable source of phenolic antioxidants

Phenolic compounds of seven grape seed samples originating from mechanical seed oil extraction were identified and quantified by HPLC–DAD before (intact seeds) and after (press residue) the oil recovery process. Total amounts of all identified compounds ranged from 4.81 (‘Cabernet Mitos’) to 19.12 g/kg (‘Schwarzriesling’) of defatted dry matter (DM; ‘Schwarzriesling’) for integral grape seeds, whereas their content in the press residues ranged from 2.80 (‘Cabernet Mitos’) to 13.76 g/kg of defatted DM (‘Spätburgunder’). This is the first study presenting comprehensive data on the contents of individual phenolic compounds comprising all polyphenolic subclasses of press residues from grape seed oil production also covering the determination of the antioxidant activities of each subclass (Folin–Ciocalteu, FRAP and TEAC assays). Additionally, the effects of different solvents on the yields of phenolic compounds were determined. Maximum yields were obtained using methanol/0.1% HCl (v:v), water [75 °C] and a mixture of ethanol and water [3:1; v:v], respectively, whereas pure ethanol resulted in poor polyphenol extraction. The results of the present study confirm the press residues of grape seed oil production still to be a rich source of polyphenolics with strong antioxidant activity.     

A beetroot juice shot is a significant and convenient source of bioaccessible antioxidants

The total antioxidant capacity (TAC) and total polyphenol (TP) content of a beetroot juice shot (70 mL) was examined following in vitro digestion. TAC was assessed using the ferric reducing antioxidant power (FRAP) assay and TP content was measured using the Folin Ciocalteu (FC) method (measured as gallic acid equivalents (GAE) before and after an in vitro digestion procedure with simulated gastric (GAS) and duodenal (DUO) phases. The beetroot shot had a high TAC (697.9 ± 1.6 μmol/70 mL) and TP content (68.4 ± 0.3 mg GAE/70 mL). FRAP values increased approximately 3-fold after GAS (2361.2 ± 20.9 μmol/70 mL) and remained high following DUO (1740.3 ± 21.1 μmol/70 mL). TP content increased 5-fold following GAS (341.6 ± 4.8 mg GAE/70 mL) and remained 3.3-fold higher following DUO (223.2 ± 5.4 mg GAE/70 mL). The beetroot shot delivers a high amount of bioaccessible antioxidants and may be a cost effective and convenient method of increasing antioxidant status.     

Critical assessment of voltammetry for rapid screening of antioxidants in marine algae

Voltammetric methods of analysis represent an attractive option for rapid screening of large numbers of plant samples in the search for novel antioxidants. However, the technique has not found widespread use as compared to established methods such as the DPPH and Folin–Ciocalteu assays. In this study we provide a critical assessment of voltammetric methods compared to the DPPH and Folin–Ciocalteu assay by conducting antioxidant assays using these methods in a study of 99 crude samples of marine algae. Thirty samples showed the presence of antioxidants via the voltammetric assay compared with 20 samples for the DPPH assay and 16 via the FC assay. Through a detailed interpretation of the results the study suggests that voltammetric methods can identify potential antioxidants in crude samples with a higher degree of confidence than DPPH or the FC method alone and represents a viable screening method for marine algal samples.     

The contribution of fruits and vegetables to dietary intake of polyphenols and antioxidant capacity in a Mexican rural diet: Importance of fruit and vegetable variety

There is mounting evidence of the health-protective role of the consumption of fruits and vegetables, which are the major contributors to dietary polyphenol intake. Lack of knowledge about the consumption of phytochemicals in the Mexican diet makes it difficult to evaluate their health significance. The aim of this study was therefore to estimate the contribution of fruit and vegetable consumption to dietary polyphenol intake and dietary antioxidant capacity in a rural population in Mexico. Despite a low intake of fruits and vegetables (< 400 g/day) in the Mexican rural diet, the mean daily intake of dietary polyphenols (> 800 mg/day) and dietary antioxidant capacity (1000-2000 ??mol trolox equivalents/day) from fruits and vegetables was similar to those determined in the Spanish Mediterranean diet. Local fruits and vegetables consumed in the Mexican rural diet are rich in polyphenols with antioxidant properties and are important source of bioactive compounds and dietary fibers. Fruit and vegetable intake needs to be promoted and lifestyle and environmental factors enhanced to improve the health status of obese Mexican rural populations.     

Phenolic and antioxidant composition of by-products from the cider industry: Apple pomace

Eleven different cider apple pomaces (six single-cultivar and five from the cider-making industry) have been analysed for low molecular phenolic profiles and antioxidant capacity. The Folin index ranged between 2.3 and 15.1 g gallic acid per kg of dry matter. Major phenols were flavanols, dihydrochalcones (phloridzin and phloretin-2′-xyloglucoside), flavonols and cinnamic acids (chlorogenic and caffeic acids). The group of single-cultivar pomaces had higher contents of chlorogenic acid, (-)-epicatechin, procyanidin B2 and dihydrochalcones, whereas the industrial samples presented higher amounts of up to four unknown compounds, with absorption maxima between 256 and 284 nm. The antioxidant capacity of apple pomace, as determined by the DPPH and FRAP assays, was between 4.4 and 16.0 g ascorbic acid per kg of dry matter, thus confirming that apple pomace is a valuable source of antioxidants. PLSR analysis gave reliable mathematical models which allowed to predict the antioxidant activity of apple pomace as a function of the phenolic profile. The variables with the higher modelling power were phloridzin > procyanidin B2 > rutin + isoquercitrin > protocatechuic acid > hyperin.     

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

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

Isolation and evaluation of the radical-scavenging activity of the antioxidants in the leaves of an edible plant, Mallotus japonicus

The antioxidative properties of a hot water extract of the leaves of Mallotus japonicus were evaluated. The extract had a high phenolic content and strong antioxidative activity, compared with green tea, rooibos tea, and red wine. Six phenolic compounds were isolated as antioxidative components by HPLC. They were identified as mallotinic acid, mallotusinic acid, corilagin, geraniin, rutin, and ellagic acid. These antioxidative compounds were subjected to DPPH radical-scavenging, superoxide radical-scavenging, and hydroxyl radical-scavenging assays, and compared with other antioxidative compounds. Four of the compounds, mallotinic acid, mallotusinic acid, corilagin and geraniin, exhibited much stronger antioxidative activity than gallic acid, rutin, ellagic acid, quercetin, and chlorogenic acid, and were as active as epigallocatechin gallate (EGCG), a strong antioxidant in green tea. Mallotus japonicus leaves are an excellent source of strong natural antioxidative materials.     

Bergamot: A source of natural antioxidants for functionalized fruit juices

Bergamot is a common Italian citrus fruit, cultivated almost exclusively to produce essential oils; the juice is considered a waste product, which represents a serious environmental and economic problem for the industries. The aim of this study was to re-evaluate bergamot juice through its chemical characterization and its use to enrich and fortify fruit juices. To investigate this, apples and apricots were used for the laboratory-scale production of fruit juice, following both the traditional industrial recipe and those with the addition of bergamot juice at 10% or 20%, together with or in order to replace the synthetic additives normally used in the industrial process (ascorbic acid and citric acid). The ascorbic acid content and the antioxidant activity were measured during the different steps of juice production and after storage at 37 °C for 15 days to evaluate juice shelf-life. Apricot and apple juices fortified with bergamot juice showed a significant increase in their antioxidant properties and a decreased reduction in ascorbic acid content after the typical production steps. All of the results obtained support the hypothesis that the addition of bergamot juice to juices preserves their ascorbic acid content from thermal degradation and contributes to enhance the antioxidant activity, ensuring a product much richer in antioxidants and ascorbic acid. A preliminary consumer test encouraged the production of bergamot fortified fruit juices. Finally, this is the first time that isorhoifolin and rutin have been detected in bergamot juice.     

In vitro antioxidant activity and phenolic profiles of tropical fruit by-products

Peel and seeds of red-skinned passion fruit, mango, longan, rambutan, white-flesh and red-flesh dragon fruit were screened for their in vitro antioxidant activity, and determination of a detailed profile of phenolic compounds. Rambutan peel and mango seed extracts exhibited the highest total phenolic content and antioxidant activities (DPPH, ABTS and FRAP values). By using UPLC-QTOF-MS/MS analysis, the profiles of soluble and bound phenolics in the fruit by-products were obtained. Ellagic acid, geraniin, quercetin hexoside, gallic and galloyshikimic acid were predominant in rambutan peel, whereas, mangiferin, ellagic acid and galloy(di)glucoside were the major phenolic compounds in mango seed. Main phenolic compounds in longan peel were ellagic acid, galloyldiglucoside, and gallic acid, while in dragon fruit peel this was isorhamnetin glycoside, isorhamnetin glucorhamoside. Meanwhile, rutin and quercetin hexoside were predominant in passion fruit peel. These findings contribute significantly to the database of phenolic profiles of by-products of tropical fruits.     

Oxidative stability of olive oil after food processing and comparison with other vegetable oils

The use of olive oil showed an important protection of meat and potatoes when compared with other vegetable oils, with sunflower oil samples being oxidised after 60 min of processing at 180 °C. Olive oil samples were not oxidised, independently of the olive oil quality used. Shelf life was longer for extra-virgin olive oil containing samples and this fact was positively correlated with their higher phenolic content. The radical-scavenging activity of extra-virgin olive oil was higher than for other olive oil samples and was also positively correlated with the phenolic content of the oil. Seed oil antioxidants showed little capacity in delaying the oxidative degradation of seed oils and meat processed with them. However, tocopherol content and the identity of tocopherols present in the oil were shown to have a more important role in the oxidative stability of seed oils than the fatty acid composition.     

Screening,determination and quantification of major antioxidants from Balanophora laxiflora flowers

In this study, antioxidant phytochemicals of Balanophora laxiflora flowers were detected by online HPLC–DPPH method. Accordingly, five phytochemicals including 1-O-(E)-caffeoyl-β-d-glucopyranose (1), 1-O-(E)-p-coumaroyl-β-d-glucopyranose (2), caffeic acid (3), 1,3-di-O-galloyl-4,6-(S)-hexahydroxydiphenoyl-β-d-glucopyranose (4), and 1-O-(E)-caffeoyl-4,6-(S)-hexahydroxydiphenoyl-β-d-glucopyranose (5) were isolated using the developed screening method. Of these, compounds 1 and 5 were found to be major bioactive phytochemicals, and their contents were determined to be 10.8 mg and 9.5 mg per gramme of crude extract, respectively. In addition, compared with (+)-catechin, a well-known antioxidant, compounds 4 and 5 exhibited stronger DPPH radical and superoxide radical scavenging activities than (+)-catechin. These results demonstrated that the flower extracts of B. laxiflora have excellent antioxidant activities and thus have great potential as a source for natural health products.     

Ice cream supplemented with grape juice residue as a source of antioxidants

Grape juice residue was incorporated into ice cream at 2.5%, 5.0% and 10.0% to obtain a product with functional characteristics. The chemical composition, colour, total phenolic compounds, antioxidant capacity and sensory acceptance of the ice creams were analysed at day 0 and after 40 days of storage. Ice creams containing grape juice residue had a higher concentration of phenolic compounds and antioxidant activity compared to the control samples. Consumers’ acceptance was similar for all products. At the end of storage, the polyphenol content and antioxidant activity had decreased. Grape juice residue has potential as a natural source of antioxidants to develop new products.     

Effect of extrusion process on antioxidant activity, total phenolics and β-glucan content of extrudates developed from barley-fruit and vegetable by-products

The aim of this study was to determine the effects of extrusion processing variables on antioxidant activity (AA), total phenolic content (TP) and β-glucan content (BG) of extrudates. Products were prepared by extrusion cooking of barley flour, barley flour–tomato pomace and barley flour–grape pomace blends. Antioxidant activity as measured by the DPPH method was 43.17 ± 0.362, 27.57 ± 0.120 and 82.23 ± 0.785% while TPs, expressed as ferulic acid equivalents, were 5.29 ± 0.126, 4.66 ± 0.023 and 9.15 ± 0.015 mg g⁻¹ dry sample in the extracts obtained from barley flour, tomato and grape pomaces, respectively. Extrusion cooking decreased AA and TP of barley, barley–tomato pomace and barley–grape pomace extrudates. Temperature and screw speed had significant ( P  <   0.05) effect on BGs of barley flour and barley–grape pomace extrudates. However, BG of tomato pomace blend extrudates had significantly ( P  <   0.05) influenced from pomace level only. Results indicated that the content of β-glucan is higher in barley flour than in extrudates of barley flour and pomace blends.     

Changes in phenolic profile and antioxidant activity during production of diced tomatoes

Tomatoes and tomato-based products are rich in antioxidants such as carotenoids, vitamin C and polyphenols. The industrial processing of diced tomatoes involves heat treatments in which these antioxidant compounds may be potentially affected. In this study, we evaluate the effect of each separate step in the dice-making process. Three technological processes were investigated: Hot, Cold and Cold treated with calcium salt (CaCl₂). Four stages were monitored in each process: (1) fresh tomatoes; (2) peeled tomatoes; (3) diced tomatoes; and (4) final product after sauce addition. The main tool for minimising or counteracting the eventual processing damage was the strategy of ‘reconstitution’, achieved by adding a sauce rich in seeds and peels with high levels of antioxidants and phenolics to the diced tomatoes. Different analyses were carried out in order to evaluate the effect of each processing step. First, total polyphenols (TP) were evaluated using Folin–Ciocalteau (F–C) assay and antioxidant activity using ABTS⁺ and DPPH assays. Flavonols, flavanones, hydroxycinnamic and phenolic acids were then quantified using liquid chromatography/electrospray ionisation tandem mass spectrometry (HPLC–ESI–MS/MS). The combination of principal component analysis (PCA) and analysis of variance (ANOVA) revealed that each processing step induces alterations in the antioxidant and phenolic profile, and in particular sauce addition and calcium treatment significantly affected the levels of antioxidants and phenolics during the dice-making process.     

Antioxidant activity of polyphenol and anthocyanin extracts from fruits of Kadsura coccinea (Lem.) A.C. Smith

Polyphenols and anthocyanins were extracted from Kadsura coccinea fruit. The contents of total phenolics and anthocyanins, influences of pH and temperature on anthocyanins, and antioxidant activities of extracts were further analyzed. The results showed that the total phenolic content of peel extracts was superior to that of pulp extracts. The total anthocyanin content of peel extracts was 180 ± 2.91 mg/100 g of fresh peel tissues. K. coccinea anthocyanins were stable below pH 4, whilst high temperature and extended heating time induced their degradation. Metal-chelating capacity (MCC) assay indicated that no ortho-dihydroxy aromatic moiety existed in the B-ring of the anthocyanin molecules, but there might be a catechol group in the B-ring of the polyphenol molecules. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity and reducing power of extracts decreased in the following order: peel polyphenol extracts > anthocyanin extracts > pulp polyphenol extracts. It would be worthwhile to introduce this rare fruit into more countries.     

Determination of polyphenolic content and antioxidant activity of kudingcha made from Ilex kudingcha C.J. Tseng

The total polyphenol content and the antioxidant activity of kudingcha made from Ilex kudingcha C.J. Tseng were determined by Folin–Ciocalteu reagent, and DPPH, FRAP, and TEAC methods, respectively. The crude extract (CE) of kudingcha and its four fractions of chloroform (CfF), ethyl acetate (EaF), n-butanol (nBF), and water (WtF) were prepared and subjected to antioxidant evaluation and analysis by high performance liquid chromatography. The extracts of kudingcha contained large amounts of caffeoylquinic acid (CQA) derivatives, including 3-CQA, 5-CQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA, and showed potent antioxidant activity. The antioxidant activities of CE and its fractions decreased in the order of EaF > nBF > CE > WtF > CfF, according to the DPPH assay and FRAP assay, which were the same, with the exception of the rank order of CfF and WtF, as the TEAC assay. Furthermore, a satisfactory correlation between total polyphenol content and antioxidant activity was observed.     

Flour from 'fruits and vegetables' waste with addition of a South-American pepper (Capsicum baccatum) proposed as food ingredient

The objective of this work was to evaluate the physicochemical properties of previously characterised flours obtained by milling the solid waste from the manufacture of an isotonic drink produced with various fruits and vegetables (FVR) to which powdered pepper fruits (PF) were added. Aqueous extracts were also prepared and encapsulated for protecting their functional compounds and improving their solubility. The encapsulation yields of the spray-drying processes were 90% and 64% for PF and FVR-PF, respectively. The addition of PF to FVR improved antioxidant capacity, stability and appearance, providing reddish colour. FT-IR spectra reflected the addition of PF by changes in the absorbances at wave numbers typical of carotenoids, acylglycerols, chlorophylls and those related to antioxidant capacity. The encapsulated extracts could be applied when solubility is needed in hydrophilic media. The obtained flours with PF addition are suitably cheap, stable functional food ingredients for industrial uses, such as breading or seasoning ingredients.     

Germination as a process to increase the polyphenol content and antioxidant activity of lupin seeds (Lupinus angustifolius L.)

In this work, the effect of germination of lupin seeds (Lupinus angustifolius L., c.v. Zapatón) on bioactive phenolic compounds as well as on the antioxidant activity was studied. Phenolic compounds were analysed by HPLC-PAD-ESI/MS. The antioxidant activity was determined by spectrophotometry, evaluating the free radical scavenging activity of the samples. Germination produced significant changes in flavonoids and non-flavonoid phenolic compounds. In the analysed samples, isoflavones, flavones and dihydroflavonols in free and conjugated forms were identified. The results obtained indicate that germination modifies the quantitative and qualitative polyphenolic composition of lupin (Lupinus angustifolius L.) seeds during the different days of the process, with a significant increase of flavonoids. An increase in the antioxidant activity was also observed as a consequence of the process. Germination was shown to be a good process to increase the phenolic content of lupin seeds as well as their antioxidant activity.