Effect of extrusion cooking and simulated in vitro gastrointestinal digestion on condensed tannins and radical scavenging activity of type II and type III whole grain sorghum

The effect of extrusion cooking and simulated in vitro gastrointestinal digestion on proanthocyanidins in type II and III tannin sorghums was studied. Extrusion cooking was performed at different feed moisture levels (2 L h^?1, 3 L h^?1, 5 L h^?1 and 8 L h^?1), with a barrel temperature of 150 °C followed by in vitro gastrointestinal digestion. Extrusion cooked samples had lower total phenols, tannin content and radical scavenging properties than unprocessed tannin sorghum flour. For extrudates, there was progressive increase in total phenols and tannin content with increase in feed moisture. Extrusion cooked samples had increased proportion of dimers and decreased oligomers in the two tannin sorghums. Gastric and duodenal digests of the extrudates contained high proportions of monomers and dimers and some oligomeric proanthocyanidin species. Undigested porridges, gastric and duodenal digests inhibited radical‐induced oxidative DNA damage. Extruded tannin sorghum may have health‐promoting potential in relation to combating chronic diseases associated with oxidative stress.     

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.     

Antioxidant effect of a crude phenolic extract from sorghum bran in sunflower oil in the presence of ferric ions

Whole grain condensed tannin sorghum, its bran and a crude phenolic extract (CPE) prepared from the bran were evaluated for total phenols (TP), condensed tannins (CT) and antioxidant activity (AA). Antioxidant effect of the CPE from the sorghum bran was evaluated in sunflower oil in the presence of ferric ions by measuring peroxide values (PVs) and anisidine values (AVs) during storage at 65 °C, in comparison with tertiary butyl hydroquinone (TBHQ). Sorghum bran contained three times more TP and AA, and seven times more CT than the whole grain. The CPE had highest levels of TP, CT and AA. Sunflower oil with CPE had lower PVs and AVs compared to control samples. Oil samples with TBHQ had PVs lower than, but AVs similar to samples containing CPE. In the presence of ferric ions, the CPE was less effective in reducing PVs, but was more effective than TBHQ in reducing AVs.     

The effect of feed moisture and temperature on tannin content,antioxidant and antimicrobial activities of extruded chestnuts

This study focuses on the effect of extrusion processing on tannin reduction, phenolic content, flavonoid content, antioxidant and anitimicrobial activity. Extrusion temperature (120 and 140 °C) and feed moisture (25% and 28%) were used on the tannin content, antioxidant and antimicrobial activities. Extrusion cooking reduced tannin content up to 78%, and improved antioxidant activity from 12.89% to 21.17% in a concentration dependant manner without affecting its antimicrobial activity that varied from 250 to 500 mg. The time–kill assay confirmed the ability of extruded chestnut to reduce Pseudomonas aeruginosa count below detectable limit that reduced the original inoculum by 3log10 CFU/mL. Overall, the results showed that extrusion cooking might serve as a tool for tannin reduction and could improve the antioxidant and antimicrobial properties of chestnut, which might be helpful for chestnut related products in the food industry.     

Antioxidant properties of solid-state fermented adlay and rice by Phellinus linteus

Phellinus linteus (Berkeley & Curtis) Teng (Hymenochaetaceae) was inoculated into cooked grains, and new products were formed after the colonisation of fungal mycelia. Our objective was to evaluate the antioxidant properties of ethanolic and hot water extracts from fermented products [Phellinus-fermented adlay (PFA) and rice (PFR)] as compared to uninoculated controls [polished adlay (PA) and rice (PR)]. PFA and PFR were more effective than were PA and PR in antioxidant activity by the conjugated diene method, reducing power, scavenging ability on 1,1-diphenyl-2-picrylhydrazyl radicals and chelating ability on ferrous ions. Total phenols were the major antioxidant components found in both extracts (1.31–9.10 mg/g). Flavonoid contents were in the range of 0.07–1.26 mg/g. Total phenols and flavonoids of two extracts were associated with antioxidant properties. Based on the results obtained, Phellinus-fermented products possessed effective antioxidant properties.     

Flavonoid content and antioxidant activity of vegetables from Indonesia

Extracts from 11 vegetables of Indonesian origin were screened for flavonoid content, total phenolics, and antioxidant activity. The flavonols myricetin, quercetin, and kaempferol and flavones luteolin and apigenin were quantified by HPLC. Flavonoid content in mg/100 g fresh weight (fw) was apparently initially reported for Cosmos caudatus H.B.K. (52.19), Polyscias pinnata (52.19), Pluchea indica Less. (6.39), Nothopanax scutellarius (Burm.f.) Merr (5.43), Talinum triangulare (Jacq.) Willd. (3.93), Pilea melastomoides (Poir.) Bl. (2.27), and Etlingera elatior (Jack) R.M.Sm (1.18). The flavonoid content of the vegetables studied were mainly quercetin and kaempferol and ranged from 0.3 to 143 mg/100 g fw, with the highest level found in Sauropus androgynus (L) Merr. C. caudatus H.B.K. had the greatest total phenols among the vegetables analysed, with 1.52 mg GAE/100 g fw. P. indica Less. and C. caudatus H.B.K. had the highest antioxidant activity as measured by ferric cyanide reducing power, DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) scavenging, and inhibition of linoleic acid oxidation. Therefore, S. androgynus (L) Merr, C. caudatus H.B.K., and P. pinnata were identified as potentially rich sources of dietary flavonoids and antioxidants.     

Effect of alkaline pretreatment and cooking on protein fractions of a high-tannin sorghum cultivar

A high-tannin sorghum cultivar (Karamaka) was used to study the effect of soaking in distilled water or 0.05%, 0.10% and 0.20% NaOH for 8 h, and soaking in distilled water or NaOH followed by cooking, on proximate composition, tannin content and protein fractions. Results showed that soaking the sorghum grains in water or NaOH for 8 h caused a slight increase in crude protein, whilst the tannin content significantly (p ? 0.05) decreased. The highest drop in tannin content was observed after soaking sorghum in 0.20% NaOH for 8 h at ambient temperature. Combining soaking and cooking further lowered the tannin content of sorghum, with a maximum reduction of 83.9%. Soaking in NaOH and cooking caused significant (p ? 0.05) increases in the albumin and globulin fractions, accompanied by a significant reduction in the glutelin fraction. This readjustment of sorghum protein fractions would indicate improvement in the quality of sorghum proteins.     

Effects of reducing phytate content in sorghum through genetic modification and fermentation on in vitro iron availability in whole grain porridges

Improved iron availability from sorghum porridges will benefit many malnourished communities in rural Africa, where there is a high prevalence of iron deficiency. This research compared the efficacy of reducing sorghum phytate content by genetic modification (GM) and natural lactic acid fermentation on in vitro iron availability in porridges. GM low phytate, non-tannin (38% phytate reduction) and tannin (36% phytate reduction) sorghums and their null controls were processed into thick unfermented and fermented porridges. The inhibitory effect of the tannins seemed to prevent any increase in in vitro iron availability, regardless of the level of phytate reduction. Only the additive effect of GM in combination with fermentation in reducing the phytate content appeared to cause a substantial increase in in vitro iron availability in the GM fermented porridge (30%) made from the non-tannin line, compared to the GM unfermented porridge (8.9%) or the fermented porridge (17.6%) of the control sorghum. This could be of nutritional significance.     

Antioxidant activities of mangrove Rhizophora apiculata bark extracts

Depolymerisation of mangrove Rhizophora apiculata bark extracts in the presence of phloroglucinol nucleophiles in ethanol was carried out. The flavan-3-ols and their phloroglucinol adducts were separated using reversed phase liquid chromatography (HPLC). The HPLC analysis of mangrove R. apiculata showed that catechin was the most common component of the flavanoid monomers. The antioxidant activities of these mangrove tannins were evaluated and compared with several commercial tannins by using reducing power, DPPH and ABTS assays with butylated hydroxytoluene, BHT and l-(+)-ascorbic acid as standards. All tannins had reducing power and percentage scavenging activities similar to the (+)-catechin and l-(+)-ascorbic acid standards. In the DPPH assay, >90% of the maximum scavenging activity was attained at 30 μg ml⁻¹. Mangrove tannins had stronger antioxidant activity than the BHT standard in the DPPH assay. The results of the ABTS assay were correlated with the DPPH assay. Scavenging activity in the ABTS assay increased as the tannin concentration increased, up to a plateau at 50 μg ml⁻¹.     

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.     

Influence of PROP taster status on the consumer acceptability of food made from tannin sorghums

BACKGROUND: Condensed tannins in sorghum are powerful antioxidants, beneficial for health. However, tannin sorghums are believed to be unpalatable. The objective was to determine the influence of 6‐n‐propylthiouracil (PROP) taster status on consumer acceptability of food from tannin sorghums. Consumers (n = 194) classified by PROP taster status (super, medium and non) evaluated the appearance, flavour, overall liking and texture of sorghum rice from two tannin‐free sorghums, PAN 8564 and Phofu, and two tannin sorghums, PAN 3860 (82 g catechin equivalents (CE) kg^?1) and NS 5511 (18 g CE kg^?1), with high antioxidant activity. RESULTS: The PROP tasters could distinguish differences among the sorghum cultivars varying in tannin content levels, finding PAN 3860 less acceptable than the other sorghums. The non tasters preferred all the cultivars equally, presumably because they could not detect taste (bitter and astringent) differences between the sorghums. With the exception of appearance, tannin sorghum NS 5511 was generally equally preferred by PROP tasters to tannin‐free sorghums. CONCLUSION: There appear to some tannin sorghums that are palatable, even to PROP tasters, because the level of tannins is below a sensitivity threshold (ca 20 g CE kg^?1). Hence such tannin sorghums could be used to produce acceptable high‐antioxidant activity foods. Copyright © 2009 Society of Chemical Industry     

Antioxidant activity of rye bran alkylresorcinols and extracts from whole-grain cereal products

The antioxidant properties of rye bran alkylresorcinols (C15:0–C25:0) and extracts from whole-grain cereal products were evaluated using their radical-scavenging activity on DPPH and the chemiluminescence method (CL). DPPH radical reduction varied from ∼10% to ∼60% for the alkylresorcinol homologues at concentrations from 5 to 300 μM and was not dependent on the length of the alkyl side chain of the particular homologue. Differences in the EC₅₀ values for the studied compounds were not statistically significant, the values varying from 157 μM for homologue C23:0 to 195 μM for homologue C15:0. Moreover, values of EC₅₀ for all the alkylresorcinol homologues were significantly higher than those for Trolox and α-, δ-, and γ-tocopherols, compounds with well-defined antioxidant activity and used as positive controls. CL inhibition was evaluated for all the tested alkylresorcinol homologues at concentrations of 5 and 10 μM and varied from ∼27% to ∼77%. Similar to the DPPH method, the slight differences in CL inhibition suggest that the length of the alkyl side chain had no major impact on their antioxidant properties. The extracts from whole-grain products were added to the DPPH and CL reaction systems and their antioxidant activities were tested and compared with the total amount of alkylresorcinols evaluated in the extracts. DPPH radical and CL reduction for the whole-grain products varied from ∼7% to ∼43% and from ∼37% to ∼91%, respectively. A clear relationship between DPPH radical and CL reduction levels and the amount of total alkylresorcinols was obtained for whole-grain breakfast cereals, in which the reduction level decreased in the order rye > wheat > mixed > barley. Therefore it may be considered that the antioxidant activity of alkylresorcinols could be of potential importance to the food industry, which is continuously searching for natural antioxidants for the protection of food products during their processing and storage.     

Optimisation of the aqueous extraction conditions of phenols from meadowsweet (Filipendula ulmaria L.) for incorporation into beverages

Meadowsweet was extracted in water at a range of temperatures (60–100 °C), and the total phenols, tannins, quercetin, salicylic acid content and colour were analysed. The extraction of total phenols followed pseudo first-order kinetics, the rate constant (k) increased from 0.09 ± 0.02 min⁻¹ to 0.44 ± 0.09 min⁻¹, as the temperature increased from 60 to 100 °C. An increase in temperature from 60 to 100 °C increased the concentration of total phenols extracted from 39 ± 2 to 63 ± 3 mg g⁻¹ gallic acid equivalents, although it did not significantly affect the proportion of tannin and non-tannin fractions. The extraction of quercetin and salicyclic acid from meadowsweet also followed pseudo first-order kinetics, the rate constant of both compounds increasing with an increase in temperature up until 90 °C. Therefore, the aqueous extraction of meadowsweet at temperatures at or above 90 °C for 15 min yields extracts high in phenols, which may be added to beverages.     

Fingerprint of enological tannins by multiple techniques approach

In this study, six enological tannins (T1–T6) from different source were analysed by selected analytical techniques, including UV–Vis, FTIR, NMR, SEC, LC-MS/MS and electronic nose. Moreover, the samples were tested for their antioxidant activity. Spectra and chromatograms are considered as a fingerprint with a pattern that is distinctive for a given type of sample. In particular, tannins showed the maximum UV–Vis absorbance (λ_max) at 273–280 nm, the inflection point (λ_min) at 247–264 nm, and the ratio λ_max/λ_min was 1.03, 1.35, 1.67, 1.36, 2.15, 2.02 for tannin T1–T6, respectively. The FTIR analysis of tannins showed the presence of most important absorption bands at 1522, 1453, 1380, 1350, 1328, 1286, 1210, 1148 and 1044 cm⁻¹. Besides, SEC and NMR analysis allowed to sort the tannins according to their average DP as follows: T1 > T2 = T4 > T3 > T6 = T5. Based on this multiple techniques approach three condensed tannins (sample T3, T5 and T6) were clearly identified, together with two mixtures of hydrolysable tannins (sample T1 and T2), whereas one sample (T4) showed a peculiar pattern different from the commercial tannin commonly used in enology.     

Polyphenol composition and in vitro antioxidant activity of amaranth,quinoa buckwheat and wheat as affected by sprouting and baking

This study examined the polyphenol composition and antioxidant properties of methanolic extracts from amaranth, quinoa, buckwheat and wheat, and evaluated how these properties were affected following two types of processing: sprouting and baking. The total phenol content amongst the seed extracts were significantly higher in buckwheat (323.4 mgGAE/100 g) and decreased in the following order: buckwheat > quinoa > wheat > amaranth. Antioxidant capacity, measured by the radical 2,2-diphenyl-1-picylhydrazyl scavenging capacity and the ferric ion reducing antioxidant power assays was also highest for buckwheat seed extract (p < 0.01). Total phenol content and antioxidant activity was generally found to increase with sprouting, and a decrease in levels was observed following breadmaking. Analysis by liquid chromatography coupled with diode array detector revealed the presence of phenolic acids, catechins, flavanol, flavone and flavonol glycosides. Overall, quinoa and buckwheat seeds and sprouts represent potential rich sources of polyphenol compounds for enhancing the nutritive properties of foods such as gluten-free breads.     

Nutritional quality and antioxidant activity of marama-sorghum composite flours and porridges

Marama bean, an underutilised legume in southern Africa, is a good source of protein, fat and phenolic compounds, the latter known to have potential health benefits. Marama flours, sorghum meal, marama-sorghum composite flours and porridges were analysed for proximate composition, amino acid composition, energy value, fatty acid composition, total phenolic content and antioxidant activity. Compositing sorghum meal (70%) with marama flours (30%) significantly increased the protein and fat contents in flours and porridges. Energy values of marama-sorghum composite porridges were 11-24% higher than sorghum porridge. Lysine content was 3-4 times higher in marama-sorghum porridges than in sorghum porridge. There was an increase in oleic acid as sorghum meal was composited with marama flour. There was a positive correlation between the total phenolic content and antioxidant activity in all samples. Use of marama flour in sorghum composite flours and porridges improved the nutritional quality and antioxidant activity.     

Antinutritional factors changes occurring in trifoliate yam (Dioscorea dumetorum) tubers after harvest

Studies were conducted on the changes in antinutritional factors occurring during the storage of Dioscorea dumetorum (cv. Yellow) yam tubers. The tubers were harvested and stored under prevailing tropical ambient conditions (19–28 °C, 60–85% RH) for 0, 2, 5, 7, 14, 21, 28, 42 and 56 days. The samples were evaluated for total phenols, tannins, phytic acid, α-amylase inhibitors, trypsin inhibitors and oxalates. Results showed that, during storage, total phenols and tannin contents decreased by approximately 22–28% after 56 days of harvest, due to the hardening phenomenon and sprouting. Phytate and α-amylase inhibitor levels declined, respectively, from 690–416 mg/100 g and 1013–659 AIU/g, while oxalates and trypsin inhibitor contents increased during the first week of storage (days 0–7) and, after this period, they started to decrease progressively. Since sprouting of most tubers was observed after 28 days of storage, the results suggest that post-harvest hardening and sprouting influence antinutritional composition of D. dumetorum tubers.     

Phenolic characterization of commercial enological tannins

Enological tannins are widely used in winemaking process to improve different characteristics of wines. A wide spectrum of enological tannins is now available on the market; however, the tannins’ chemical nature and botanical origin are not always clearly defined in the commercial products. The aim of this work was the chemical characterization of ten commercial plant-derived tanning agents of enological use. Enological tannins were analyzed by spectrophotometry (total phenols, total tannins and gelatin index) and high performance liquid chromatography (HPLC–DAD) (low molecular weight phenolic compounds). In general it was possible to observe important differences in the concentration of total phenols, total tannins and gelatin index values among the commercial products studied. By using HPLC–DAD it was possible to classify different types of tannins (mainly hydrolyzable (gallotannins and ellagitannins), condensed or proanthocyanidic tannins and blends of these groups). Clear differences were evident between the study results and the information on the type of tannin indicated on some of the commercial tannin labels. These discrepancies could lead to technological problems in the winery industry because of the different aims that guide the use of different types of these enological products.     

The influence of fruit ripening on the phytochemical content and biological activity of Capsicum chinense Jacq. cv Habanero

During the past decade, it has been reported that the consumption of certain foods and spices such as pepper may have a positive effect on health. The present study evaluates the influence of fruit ripening on total phenols, flavonoids, carotenoids and capsaicinoids content and antioxidant, hypoglycaemic and anticholinesterase activities of Capsicum chinense Jacq. cv Habanero. The chemical investigation showed a different composition between the two stages of ripening (immature and mature). Generally, the concentration of carotenoids and capsaicinoids increased as the peppers reached maturity, whereas the concentration of phenols declined. The immature fruits showed the highest radical scavenging activity (IC₅₀ of 97.14 μg/ml). On the contrary, the antioxidant activity evaluated by the β-carotene bleaching test showed a significant activity for mature peppers (IC₅₀ value of 4.57 μg/ml after 30 min of incubation). Mature peppers inhibited α-amylase with an IC₅₀ of 130.67 μg/ml. The lipophilic fractions of both mature and immature peppers exhibited an interesting and selective inhibitory activity against α-amylase with IC₅₀ values of 29.58 and 9.88 μg/ml, respectively. Both total extracts of mature and immature peppers inhibited butyrylcholinesterase selectively. The obtained results underline the potential health benefits as a result of consuming C. chinense Habanero and suggest that it could be used as new valuable flavour with functional properties for food or nutriceutical products on the basis of the high content of phytochemicals and found biological properties.