Effect of consecutive steeping on antioxidant potential of green,oolong and black tea

After water, tea is considered to be one of the most consumed drinks worldwide. To get the maximum benefit from the whole‐leaf teas, the manufacturers provide instruction that these teas can be steeped 2–3 times over 6–8 h. In this study, the effect of consecutive steeping on radical‐scavenging ability of whole leaf green tea (unfermented), oolong tea (partially fermented) and black tea (fully fermented) was determined. Green tea showed the highest level of antioxidant activity, total phenolic and flavonoid content followed by oolong tea and black tea irrespective of the number of steeping done. The result also demonstrated that re‐steeping reduced the antioxidant potential of teas. Moreover, it was revealed that green tea is the best candidate for re‐steeping followed by oolong and then black tea.     

Chemical,antioxidant and antibacterial study of Brazilian fruits

In this study, the antioxidant capability, total phenolic content and antimicrobial activity of ethanolic extracts of seven fruits from the Brazilian Atlantic Forest were evaluated. The conditions for the extraction of crude phenolics from the fruits were determined using an experimental factorial design. Total phenolic content, 1,1‐diphenyl‐2‐picrylhydrazyl radical (DPPH^?) scavenging activity and β‐carotene‐linoleic acid couple oxidation assays were used to evaluate the antioxidant properties of the extracts. In addition, antimicrobial activity was screened using two Gram‐negative bacteria (Escherichia coli and Klebsiella pneumoniae) and one Gram‐positive bacterium (Staphylococcus aureus). All native fruits assayed in this study have high potential as natural antioxidant sources. Among the seven fruits evaluated, Jabuticaba and Uvaia had the highest antioxidant activity in the DPPH^? and of β‐carotene‐linoleic acid coupled oxidation assays. In the biological assay, K. pneumoniae was the most sensitive microorganism to the fruit extracts, and the Jabuticaba extract had a slight inhibitory effect against this Gram‐positive bacterium.     

Screening of medium composition for the free radical‐scavenging properties by Antrodia cinnamomea

The effects of nutritional conditions on the scavenging capacity on superoxide anion radical and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free radical of ethanolic extracts from filtrates of Antrodia cinnamomea were investigated in shake‐flask cultures. Culture medium significantly affected inhibition of superoxide anion generation and DPPH free radical scavenging activity. In contrast, both scavenging capabilities on superoxide anion radical and DPPH free radical were found to be greatly affected by varying the carbon source, the nitrogen source, the growth factors or the trace elements. The maximal inhibition of superoxide anion generation could be obtained when the culture medium compositions were: xylose, ammonium oxalate, nicotinic acid, NaH₂PO₄ and CuSO₄; while a maximal DPPH free radical scavenging activity could be achieved when the medium composition setting as: fructose, peptone, nicotinic acid, KH₂PO₄ and CaCl₂ (the scavenging effects on superoxide anion radical and DPPH free radical were increased to 96.3 ± 0.3% and 29.0 ± 1.0%, respectively). We proved that controlling the culturing conditions and modifying the composition of the medium can dramatically enhance the scavenging ability on superoxide anion radical and DPPH free radical of A. cinnamomea.     

In vitro study on antioxidant activities of peanut protein hydrolysate

Peanut protein was hydrolysed with a commercial protease, Alcalase 2.4L, and the resulting hydrolysate was investigated for its antioxidant activities, including the ability to inhibit the autoxidation of linoleic acid, the scavenging effect on the 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) free radical, the reducing power and the inhibition of liver lipid oxidation. As compared with the peanut protein, peanut protein hydrolysate showed strong inhibition of the autoxidation of linoleic acid, to scavenge DPPH free radical and showed strong reducing power. Moreover, peanut protein hydrolysate also displayed noticeable inhibition of liver lipid autoxidation and lipid oxidation induced by H₂O₂ or Fe²⁺ in vitro. All these effects of the sample were concentration‐dependent. These results suggest that peanut protein hydrolysate could be a suitable natural antioxidant and may be a health food for humans. Copyright © 2006 Society of Chemical Industry     

Antimicrobial and antioxidant activities of different propolis samples from north‐western Algeria

The aim of this study was the investigation of antimicrobial and antioxidant activities of different ethanolic extracts of propolis (EEP) collected from north‐western Algeria. Total polyphenols and flavonoids contents of extracts were measured. The UV absorption spectrum showed and confirmed their polyphenols constituents. All EEPs exerted antibacterial activity against Gram‐positive bacteria, but no effect on Gram‐negative bacteria. The minimum inhibitory concentration (MIC) of EEPs ranged from 0.01% to 2.6% v/v. The antioxidant activity was measured using ferric‐reducing power (FRAP), 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) free radical‐scavenging and ESR methods. Propolis TIA‐2 and MOH‐MAS samples showed the highest antioxidative capacity, after 35 min, while TIA‐1, NED‐TL and SFS‐SBA samples showed the highest antioxidative potential of measured EEPs, after 3 min. TIA‐2 sample showed the highest antibacterial, antioxidant activity and highest DPPH free radical‐scavenging activity as well as the highest polyphenols and flavonoids content, compared with other propolis samples.     

Slicing increases antioxidant capacity of fresh‐cut lotus root (Nelumbo nucifera G.) slices by accumulating total phenols

Slicing is an abiotic stress during fresh‐cut lotus root slices (FLS) preparation. To evaluate the potential ability of slicing to induce antioxidant capacity (AC) in FLS, fresh lotus roots were sliced into 0.4 cm thick slices and stored at 7 °C for 7 days using intact root segments as control. Results showed slicing induced 68.3% higher phenylalanine ammonia‐lyase (PAL) activity and parallel 130.5% more total phenol (TP) accumulation after 7 days storage compared to control. AC values in FLS assayed by FRAP and ABTS^●+ were 41.5% and 93.8% more than those in control samples at the end of storage, respectively. Such increases in AC values were mainly attributed to TP accumulation as a positive correlation existed between AC and TP. However, slicing significantly accelerated FLS browning by increasing the polyphenol oxidase (PPO) activity during storage. Nevertheless, FLS was still marketable with the maximum browning index of 1.9 after 7 days storage.     

Antioxidant capacity and total phenolic content of selected plants from Turkey

A total of 28 different plants from different regions of Çanakkale, Turkey, were investigated for their antioxidant capacity and total phenol contents to find new potential sources of natural antioxidants. The antioxidant capacity of methanolic extracts prepared from various parts of plants was evaluated by both trolox equivalent antioxidant capacity (TEAC) and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assays, while the total phenolics were determined using the Folin‐Ciocalteu method. The TEAC values of plant extracts ranged in a large scale from 1472.36 to 17.61 μmol of trolox equivalents per g dry weight (dw), and EC₅₀ values (concentration at which 50% radical scavenging occurred) varied from 0.174 to 42.475 mg dw of plant, while the total phenol content of plant extracts ranged between 117.20 and 1.27 mg of gallic acid equivalents per g dw. There was a positive linear correlation between the TEAC and total phenols of plant materials (r = 0.916). The extracts of Hypericum perforatum, Arbutus andrachne and Paliurus spina‐christii showed higher antioxidant activities (both TEAC and DPPH assays). However, there was no clear relationship between TEAC and EC₅₀ values (r = 0.477) of plant extracts.     

Characterisation and comparison of phenols,flavonoids and isoflavones of soymilk and their correlations with antioxidant activity

To investigate the relationship between bioactive compounds and antioxidant property, total phenolic content (TPC), total flavonoid content (TFC), individual and total isoflavone content of soymilk and their correlations with oxygen‐radical‐absorbing capacity (ORAC), ferric reducing antioxidant power (FRAP) and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging capacity values were evaluated and compared. Results showed that TPC, TFC, isoflavones (including concentration and profiles) and antioxidation activity significantly varied among ten tested soybean cultivars. Significant correlations were established between DPPH and TFC (r = 0.553, P < 0.01), DPPH and TPC (r = 0.753, P < 0.01), FRAP and TFC (r = 0.599, P < 0.01) and FRAP and TPC (r = 0.616, P < 0.01). Positive linear correlations were found between subtotal, total isoflavones and ORAC. Unlike other isoflavone monomers, aglycone isoflavones correlated positively with DPPH and FRAP significantly. DPPH well correlated with FRAP, whereas neither DPPH nor FRAP correlated with ORAC. TPC, TFC, individual and total isoflavone values are potentially useful for soymilk antioxidant activity assessment.     

Antioxidant activity and phenolic content of pressurised liquid and solid–liquid extracts from four Irish origin macroalgae

The efficiency of solid–liquid extraction (SLE) and pressurised liquid extraction (PLE) for the recovery of antioxidant and polyphenols from the Irish macroalgae, Fucus serratus, Laminaria digitata, Gracilaria gracilis and Codium fragile, was assessed using the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays and the Folin–Ciocalteu total phenol content (TPC) assay. Fucus serratus had TPC and antioxidant activities thirty times higher than the other species. Solid–liquid extraction cold water (CW_SLE) had the highest TPC (81.17 μg GAE mg^?1 sample) derived from F. serratus, compared with the TPC of 61.12 μg GAE mg^?1 sample for the corresponding PLE extract. For both SLE and PLE extracts, low TPC levels were observed in L. digitata, G. gracilis and C. fragile. The majority of SLE extracts possessed higher FRAP and DPPH activities compared with their PLE counterparts. This study indicates that the high temperatures and pressures in PLE did not enhance the antioxidant activities relative to conventional SLE extraction.     

Chemical,antioxidant and sensory properties of tomato‐watermelon‐pineapple blends,and changes in their total antioxidant capacity during storage

A conductometric analysis of the effect of condensate of peroxides generated during lipid oxidation in an accelerated stability test was adapted to test the hypothesis that total antioxidant capacity of tomato products would sometimes increase during processing and in storage. Tomato pulp blends made from a mixture of tomato (Lycopersicon esculentum var Roma VF), watermelon (Citrullus vulgaris var Babylack) and pineapple (Ananas comosus var Smooth cayennes) were analysed for basic quality profiles of dry matter, Brix, titratable acidity (TTA) and pH, total reducing sugars, Component antioxidants phytochemicals and total antioxidant capacity. The lowest sensory score (overall impression) of 4.80 ± 2.59 was recorded for tomato juice while, blend TWP 111p had highest score of 6.20 ± 1.99. There was significant difference (P < 0.05) in the basic quality profile of the pulp blends except for TTA values (0.37 ± 0.02 to 0.45 ± 0.05) and 2‐Furfurals (2.47 ± 0.03 to 2.71 ± 0.01). The fresh blend of 50% tomato, 25% watermelon and 25% pineapple had the highest total antioxidant capacity of 3.69 ± 0.52 mg 100 mL^?1 catechin equivalent. The total antioxidant capacity of the stored pulp increased from 2.95 ± 0.13 to 6.22 ± 0.32 mg 100 mL^?1 catechin equivalent in pasteurised TWP 211p blend by 60 days when stored at 40 °C. Total antioxidant status of tomato‐based fruit mix increased during the first 80 days.     

Antioxidant activity and dietary fibre of Prensal Blanc white grape (Vitis vinifera) by‐products

Stem and pomace of a white grape (Vitis vinifera) variety, Prensal Blanc, were studied for the first time: general composition and dietary fibre components together with the total soluble polyphenol content and antioxidant activity. Both by‐products present high contents of total dietary fibre (TDF), 790 g kg^?1 d.m. (stem) and 716 g kg^?1 d.m. (pomace). Values of the soluble dietary fibres in relation to TDF differed: 5% (stem) and 14.4% (pomace). Similar values of Klason lignin were found: 229 g kg^?1 (stem) and 278 g kg^?1 (pomace), however, the pomace exhibited more than twice the content of the condensed tannins (168 g kg^?1) with regard to the stem (79 g kg^?1). Notable were the high resistant protein contents of both by‐products. Stem and pomace showed appreciable amounts of total soluble polyphenols (87 g kg^?1 against 35 g kg^?1 respectively). The free radical scavenging capacity of the former by‐products was determined using the 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH) method, obtaining EC₅₀ values of 0.79 g d.m. g^?1 DPPH (stem) and 1.32 g d.m. g^?1 DPPH (pomace). These data shows that both vinification by‐products from the Prensal Blanc variety are a good source of dietary fibre and have antioxidant properties.     

High‐pressure high‐temperature extraction of phenolic compounds from grape skins

This study focused on the use of a non‐conventional extraction technology by employing high‐pressure high‐temperature stirred reactor to extract polyphenols from grape skins. Extraction time (15–330 min) and temperature (30–150 °C) were selected as independent variables, and their effects were studied. A preliminary kinetic study on polyphenols extraction revealed that the second‐order model fitted satisfactorily the experimental results (R² ≥ 0.9798). Total polyphenol yield and total flavonoid (TF) yield, as well as the antiradical power (ARP) of the extracts, were analysed. The use of high‐pressure high‐temperature technology resulted in obtaining extracts rich in polyphenols with high ARP. The highest total polyphenol (60.7 mg_GAE ) and TF (15.1 mg_CE ) yields were obtained at 150 °C for 270 min and 150 °C for 15 min, respectively. HPLC was employed to analyse phenolic compounds. Considerable quantities of single phenolic compounds were extracted. The highest yields of gallic acid, 5‐hydroxymethylfurfural, protocatechuic acid, catechin, vanillic acid, syringic acid, cumaric acid, trans‐resveratrol and quercetin (163.2, 20.0, 69.9, 420.0, 20.6, 603.0, 20.1, 42.4 and 117.1 mg per 100 g_DS, respectively) were found. ARP values were found between 8.45 and 52.17 μg_DPPH .     

Oxidative stability of butter with added phenolics from Lamiaceae herbs and in vitro evaluation of potential cytotoxicity of rosemary (Rosmarinus officinalis L.) extract

This study evaluated the oxidative stability of butter with added phenolics from Lamiaceae herbs. Initially antioxidant activity of crude rosemary, oregano, sage, thyme and marjoram extracts were screened through methods of inhibition of the 1,1‐Diphenyl‐2‐picrylhydrazyl (DPPH) radical, malondialdehyde (MDA) quantification and ferric reducing antioxidant power test. The alcoholic extract of rosemary showed the highest antioxidant activity in both assays for DPPH radical inhibition and MDA quantification. The alcoholic rosemary extract showed no cytotoxicity when assayed using MTT [3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide] reduction method and had dose‐dependent cytoprotective activity at 50 and 250 μg mL^?1. These results suggest that the use of rosemary as natural antioxidant is safe in the concentrations tested. The highest oxidative stability of butter with added alcoholic rosemary extract at temperatures of 60 and 110 °C was obtained with the concentration of 400 mg of phenolic compounds per kg of butter and was reflected at the lowest formation of degraded peroxides from lipids.     

Proximate composition and sensory evaluation of anthocyanin‐rich purple sweet potato (Ipomoea batatas L.) wine

Purple sweet potato (PSP) is a special type of sweet potato having high anthocyanin pigment in the root. The starch contents of PSP (root/water homogenised in 1:1 ratio) were enzymatically saccharified [using commercial thermostable enzymes Termamyl^® (0.2%) and Dextrozyme^®GA (1%)] to fermentable sugars, and the filtrate was ameliorated with cane sugar to achieve 20° Brix, for subsequent fermentation into a red wine using 2% yeast (Saccharomyces cerevisiae) as starter culture. The wine had the following proximate compositions: total soluble sugar (TSS), 2.25° Brix; starch, 0.15 g per 100 mL; total sugar, 1.35 g per 100 mL; TA, 1.34 g tartaric acid per 100 mL; phenol, 0.36 g (caffeic acid equivalent) per 100 mL; anthocyanin, 55.09 mg per 100 mL; tannin, 0.64 mg per 100 mL; lactic acid, 1.14 mg per 100 mL; ethanol, 9.33%(v/v); and pH, 3.61. 2, 2‐Diphenyl‐1‐picrylhydrazyl (DPPH) scavenging activity of the wine was 58.95% at a dose of 250 μg mL^?1. Principal component analysis reduced the eleven original analytical and proximate variables (TSS, starch, total sugar, TA, phenol, anthocyanin, tannin, lactic acid, ethanol, pH, DPPH) to four independent components, which accounted for 76.65% variations. Sensory evaluation was carried out by sixteen trained panellists on various attributes such as clarity, colour, viscosity, odour, flavour, spritz and finish. Independent ‘t’ test confirmed that all the sensory attributes of the PSP wine scored closely (within 10% variation) to that of a commercial grape wine. The red wine produced contains essential antioxidants and acceptable sensory qualities.     

Physical properties and antioxidant activity of an active film from chitosan incorporated with green tea extract

An active film from chitosan incorporated with aqueous green tea extract (GTE) was developed. The effects of GTE concentrations including 2, 5, 10 and 20% (w/v) of green tea in the film-forming solution on the film properties were determined by measuring physical properties, total polyphenolic content and antioxidant activity of the active films. Fourier Transform Infrared (FTIR) spectrometry was carried out to observe the potential modifications of the chitosan films when incorporated with GTE. The results suggested that incorporation of GTE into chitosan films improved mechanical and water vapor barrier properties and enhanced polyphenolic content and antioxidant activity of the films. Changes in the FTIR spectra of the chitosan films were observed when GTE was incorporated, suggesting some interactions occurred between chitosan and the polyphenols from GTE. This study showed the benefits of incorporation of GTE into chitosan films and the potential for using the developed film as an active packaging.     

Effects of UV‐C on antioxidant capacity,antioxidant enzyme activity and colour of fresh‐cut red cabbage during storage

Ultraviolet C (UV‐C) irradiation is a widely used nonthermal sterilisation method used to ensure the quality and safety of fresh and fresh‐cut produce. However, research focus of UV‐C has recently shifted from safety of sterilisation damage towards improvements in quality. Red cabbage (Brassica oleracea var. capitata f. rubra) is a widely consumed fresh‐cut vegetable. In this study, the effects of UV‐C irradiation on the antioxidant capacity, antioxidant enzyme activity and colour of fresh‐cut red cabbage were evaluated. The UV‐C decreased the L*, a* and b* values, and it turned the colour darker and increasingly blue. UV‐C increased the activity of four antioxidant enzymes and also stimulated the accumulation of flavonoids, glutathione and ascorbic acids. The antioxidant activity of UV‐C treatment was higher than in the control group. These results suggest that an appropriate dose of UV‐C may improve the antioxidant properties of fresh‐cut red cabbage.     

Effects of ultrasound intensities on a glycin–maltose model system – a means of promoting Maillard reaction

Effects of ultrasound on pH, intermediate products, browning, maltose content, reducing power and antioxidant activity of a glycin–maltose solution were investigated. Results showed that the ultrasonic treatment at the intensity of 17.83 W cm^?2 for 100 min resulted in the increases of the solution’s absorbance at 294 and 420 nm and the antioxidant activity from approximately 0% to 1.06%, 0.30% and 22.53%, respectively. At the same time, 86.93% reduction in maltose was observed. In addition, little 5‐hydroxymethyl‐2‐furaldehyde was found in HPLC analyses. This study indicated that ultrasound, especially at higher intensities, could potentially be employed as a means to promote the Maillard reaction in the glycin–maltose solution.