Antioxidant activity and profiles of common fruits in Singapore

Thirty-eight types of fruits commonly consumed in Singapore were systematically analysed for their hydrophilic oxygen radical absorbance capacity (H-ORAC), total phenolic content (TPC), ascorbic acid (AA) and various lipophilic antioxidants. Antioxidant composition and concentration varied widely across different fruits. Many of the tropical fruits tested were high in antioxidants. Amongst all fruits tested, sapodilla (Manilkara zapota) had the highest H-ORAC and TPC whilst guava had the highest AA per gram fresh weight. Papaya, red watermelon and cantaloupe had the highest β-cryptoxanthin, lycopene and β-carotene per gram fresh weight, respectively. On the other hand, durian and mangosteen were high in tocopherols and tocotrienols, respectively. Based on consumption data, Chinese Singaporeans appear to have a higher intake of carotenoids and tocopherols rich fruits compared to the US population. As fruits are a rich source of diverse antioxidants, efforts to promote consumption of a variety of fruits should be continued for public health benefits.     

Effects of gallotannin treatment on attachment, growth, and survival of Escherichia coli O157:H7 and Listeria monocytogenes on spinach and lettuce

Food-borne illness outbreaks are increasingly associated with fresh produce. Their high prevalence may reflect the lack of methods to effectively remove pathogenic bacteria from the surface of fruits and vegetables. This study evaluated the effect of antimicrobial gallotannins on attachment, growth, and survival of food-borne pathogens on green leafy vegetables. Spinach leaves and interior leaves of lettuce harboring high and low cell counts of background microbiota, respectively, were washed with tap water with and without added gallotannins. To account for the variability among organisms, green leafy vegetables were inoculated with strain cocktails of Escherichia coli O157:H7 and Listeria monocytogenes. Cell counts of L. monocytogenes were significantly reduced by the gallotannin treatment. Lower cell counts after storage for 8?days at 4?°C demonstrated antimicrobial effects of gallotannins retained on the surface of green leafy vegetables. Gallotannin treatments with 1?g/L did not inhibit E. coli O157:H7 but hindered their attachment to filter paper by up to 94?%. The addition of gallotannin-containing extracts from mango (Mangifera indica L.) kernels to the washing water did neither alter color nor texture of bagged fresh-cut products. In conclusion, gallotannin treatment significantly reduced surface contamination of green leafy vegetables with L. monocytogenes and reduced the attachment of cells of E. coli O157:H7.     

Effect of blanching on the antioxidant properties of some tropical green leafy vegetables

Eight popularly consumed green leafy vegetables in Nigeria namely: Structium sparejanophora, Amarantus cruentus, Telfairia occidentalis, Baselia alba, Solanum macrocarpon, Corchorus olitorus, Vernonia amygdalina, and Ocimum gratissimum were blanched in hot water for 5 mins. The antioxidant properties of the fresh and blanched green leafy vegetables were subsequently determined. The total phenol, ascorbic acid and the antioxidant potentials as typified by reducing property and free radical scavenging activity was also determined. The results of the study revealed that blanching cause a significant (P<0.05) increase in the total phenol [fresh (0.1–0.3 g/100 g), blanched (0.2–0.6 g/100 g)] content of the green leafy vegetables except in Amarantus cruentus and Vernonia amygdalina where there was no change. Conversely, there was a significant (P<0.05) decrease in the vitamin C [fresh (43.5–148.0 mg/100 g), blanched (15.8–27.3 mg/100 g)], reducing property [fresh (0.5–1.5 absorbance), blanched (0.1–0.6 absorbance)] and free radical scavenging ability [fresh (20.0–51.4%), blanched (16.4–47.1%)] of the blanched green leafy vegetables except in Structium sparejanophora, where there was no change in the reducing property (0.6 absorbance) and free radical scavenging ability (59.8%) of the blanched vegetable. In view of this it could be concluded that blanching of vegetables though makes green leafy vegetables more palatable and less toxic, however it reduces their antioxidant properties drastically.     

Folate Content and Composition of Vegetables Commonly Consumed in China

Abstract: Folate deficiency increases the risk of chronic diseases, including neural tube defects (NTDs) in infants, megaloblastic anemia, cardiovascular disease, and some cancers in adults. China is the most NTDs prevalent area in the world. Folate deficiency in China can be reduced by proper supply of fresh leafy green vegetables but little is known about the folate content and vitamers in the vegetables commonly consumed by Chinese population. The purposes of this study were first to analyze most commonly consumed important vegetables that contribute to folate intake in the Chinese population and second to estimate the significance of selected vegetables as a source of dietary folate intake. Folate content and vitamers forms in vegetables were analyzed using a valid liquid chromatography method. Monoenzyme treatment was used for leafy green and some fruit vegetables, and dienzyme treatment for some root vegetables. Total folate content in commonly consumed vegetables ranged from 14.78 to 145.54 μg/100 g in edible portion with an average of 61.99 μg/100 g. The highest folate content (>140 μg/100 g) was found in pak choi and spinach. Total folate contents in leafy vegetables, fruit vegetables, and root vegetables were in the range of 17.22 to 145.54 μg/100g, 18.14 to 86.04 μg/100g, and 14.78 to75.81 μg/100g, respectively. The considerable variations in folate content were found in different types of vegetables commonly consumed by Chinese population. Leafy vegetables are a better source of folate than fruit and root vegetables commonly consumed by Chinese population. Practical Application: Data from this research would facilitate to accurately establish the actual folate intake by Chinese population. Our folate composition data on vegetables can be incorporated into the national food databases. Availability of such data is essential for estimating folate intake and defining an optimal level for fortification program in China.     

Evaluation of Free Radical Scavenging Activity and Antioxidant Potential of a Few Popular Green Leafy Vegetables of Malaysia

In this study, phenolic contents and antioxidant activity of five popular green leafy vegetables of Malaysia—Kangkung, Kucai, Di Huang Miao, Ubi Keledek, and Yaw Mak Choy—were evaluated. Methanol, acetone, and distilled water were the solvent systems used for extraction. The antioxidant capacity of the extracts was evaluated using ferric reducing antioxidant potential assay and the free radical scavenging capacity was evaluated using the DPPH· radical-scavenging assay. The total flavonoids, flavonols, and tannins were also quantified. The efficacy of the three solvents used for extraction differed significantly for both the levels of antioxidants and free radical scavenging activity. In general, methanol was the best of the three solvents for extraction of antioxidants. The results of this study will be useful for health conscious consumers, and they will provide a basis for future exploration of these green leafy vegetables as potential sources of natural antioxidants for food and nutraceutical applications.     

Use of bacterial strains antagonistic to Escherichia coli for biocontrol of spinach: A field trial

To counteract global food safety hazards related to raw consumption of ready-to-eat leafy vegetables, a method to improve bacterial status using antagonistic bacteria was studied under field conditions. This is the first study to identify potential Escherichia coli antagonists from the native microbiota on leafy green vegetables and evaluate their effect in an industrial field production setting. Bacterial strains were isolated from different types of leafy green vegetables and selected upon their effect against E. coli in vitro, and out of 295 tested bacterial strains, 37 showed an antagonistic effect. Four of those antagonistic strains were coated in separate treatments onto spinach seeds and planted in the field. Both seeds and plants were analyzed by Illumina MiSeq next generation sequencing (NGS), and it was seen that the microbiota of the plants contained lower relative abundance of plant and human pathogenic genera. Higher β-diversity was observed for the samples treated with Bacillus coagulans LMG P-32205 and B. coagulans LMG P-32206 compared to control, indicating that those strains have induced substantial changes in the native microbiota of the leaves. A reduction of Escherichia-Shigella was seen for two of the isolates (Pseudomonas cedrina LMG P-32207 and Pseudomonas punonenis LMG P-32204) as the seeds developed into plants. Seeds inoculated with two of the strains (B. coagulans LMG P-32205 and B. coagulans LMG P-32206) had increased levels of Lactobacillaceae, and treatment with B. coagulans LMG P-32206 resulted in lower levels of Pantoea (from 31.4 to 12.2%).These results encourage the usage of bacterial antagonists as part of a global solution to reduce the risk of human pathogens on leafy green vegetables.     

Effects of Holding Methods and Time on the Vitamin Contents of Five Tropical Leafy Vegetables

Five tropical leafy vegetables, Pterocarpus soyauxii (“oha”), Pterocarpus santalinodes (“nturukpa”), Gongronema latifolium (“utazi”), Corchorus olitorius (“ahihiara”) and Amaranthus hybridus (“green”) were held for four days at ambient condition using three different popular local methods used in the Southeastern states of Nigeria. Each leafy vegetable was divided into three lots. Lots I and II were unwrapped while lot III was wrapped with broad cocoyam leaves. The three lots were held under a shade. In addition, lot II was regularly taken outside to the open at nights where it was exposed to cool air and early morning dews. The vitamin contents of each leafy vegetable lot were analysed initially and on daily basis for four days. The beta carotene and ascorbic acid contents ranged respectively from 4.88 – 9.84 μg and 105.62 – 278.65 mg per 100 g of the leafy vegetable. The five leafy vegetables are fair sources of thiamin, riboflavin and niacin. There were losses in the vitamins as holding time increased, regardless of the holding method employed. The rate of loss of vitamins was highest in Lot I (the unwrapped leaves that were kept in a shade both day and night). The rate of loss of vitamins was lowest in Lot III (the wrapped leafy vegetables).     

Ultrasound-assisted extraction and antioxidant activity of phenolic and flavonoid compounds and ascorbic acid from rugosa rose (<Emphasis Type="Italic">Rosa rugosa</Emphasis> Thunb.) fruit

The present study aimed to extract total phenolic compounds (TPC), total flavonoid compounds (TFC), and ascorbic acid (AA) from the fruit of rugosa rose (Rosa rugosa Thunb.) by ultrasound-assisted extraction (UAE), and to evaluate their antioxidant activities. UAE significantly increased the extract yield compared with that obtained using the conventional method. TPC, TFC, and AA were extracted, depending on the extraction conditions (temperature, time, and ethanol concentration), in the range of 50.73–96.69, 15.93–31.88, and 3.06–6.08 mg/g, respectively. TPC and TFC were effectively extracted at a relatively high temperature (50 °C) than AA was (30 °C). The solvent condition used to extract TPC, TFC, and AA was 50% ethanol. The UAE condition for the highest antioxidant activity was obtained 30 °C, 30 min, and 50% ethanol, which were the same condition for the highest AA extraction. Among the extracts, AA showed a strong correlation with antioxidant activity at p-value of 0.001.     

A comparative assessment of total phenolic content,ferric reducing-anti-oxidative power,free radical-scavenging activity,vitamin C and isoflavones content in soybean with varying seed coat colour

Reports concerning anti-oxidative properties of yellow, green and black soybean seeds available in the literature are insufficient and limiting. In the present investigation, mature seeds of 18 genotypes, 6 from each type of soybean i.e. yellow, green and black, were assessed for total phenolic content (TPC), ferric reducing-anti-oxidative power (FRAP), 2,2-diphenyl-1-picrylhydrazine (DPPH) free radical-scavenging activities (FRSA). Isoflavones and vitamin C, the antioxidants, were also determined in all the soybean genotypes. Significant genotypic variation was observed for TPC, FRAP, FRSA, isoflavones and vitamin C within each type of soybean. Maximum genotypic variation (7.27-fold) was observed for TPC in black soybean. Average FRAP value of yellow soybean was significantly (p < 0.05) lower than black and green soybeans. Average FRSA in black soybean was significantly higher than yellow and green soybean group. Average total phenolic content and isoflavones levels were not significant across different types of soybean. Correlation studies indicated significant (p < 0.05) positive correlation between FRSA and TPC in black soybean. Our results suggest that antioxidant constituents other than isoflavones contribute significantly to the FRSA in black soybean genotypes.     

Effects of storage condition and domestic cooking on the quality and nutrient content of African leafy vegetables (Cassia tora and Corchorus tridens)

BACKGROUND: The main objective of this research was to determine changes in nutrient content of two African leafy vegetables, Cassia tora and Corchorus tridens, on cooking and storage under different temperature conditions, i.e. room storage (20 °C), refrigerated storage (4 °C) and frozen storage (?18 °C). RESULTS: The leafy vegetables were analysed for moisture, colour (Hunter L, a, b), texture, total chlorophyll, ascorbic acid, dehydroascorbic acid and total phenolics. Results indicated that the degradation of ascorbic acid was highest as a result of frozen storage, followed by room temperature storage. The dehydroascorbic acid content was correspondingly high in frozen stored leafy vegetables, whereas it was undetectable in the room temperature and refrigerated stored materials. The total phenolic content of the leaves increased with storage time while the total chlorophyll content decreased under all storage conditions. Domestic cooking resulted in significant additional losses of ascorbic acid following storage under all temperature conditions, with only 1–10% retention in the leaves and 50–60% retention in the cooking water. The green colour of the leafy vegetables was retained best under refrigerated and frozen storage, while the peak force and toughness of the leaves increased upon storage under all conditions. The moisture content of the leafy vegetables did not show any significant difference on storage. CONCLUSION: This study is one of few to report nutrient content changes on the same raw material stored under various temperature conditions and cooked domestically. Refrigerated storage resulted in the highest retention of ascorbic acid and green colour in the leafy vegetables. Copyright © 2009 Society of Chemical Industry     

Home-grown school feeding: promoting local production systems diversification through nutrition sensitive agriculture

The consumption of some non-staple crops such as legumes and dark, green leafy vegetables can address common deficiencies in key nutrients such as vitamin A and iron; however, limited markets and supply chain development impede their production and accessibility to consumers. This study investigates the pathways to promote agricultural production and dietary diversity for a local market intervention called Home-Grown School Feeding (HGSF). School feeding menus from 24 districts across 10 regions in Ghana during the 2014–15 school year were analysed in terms of food groups and several individual foods. The menus were then compared with food groups produced by households during the past year or consumed in the past seven days using data collected from a household survey. Greater inter-food group diversity in the menus was associated with higher production levels for tubers and dark, leafy green vegetables in the South and cereals in the North. A correspondence between the frequency in which a food group appeared in a menu and the share of households who consumed foods from the food group was also noted. Key issues, such as optimizing supply chains, enabling farm linkages and supporting diverse nutrient rich food groups, that underlie the success of Home-Grown School Feeding and other agricultural policies with similar goals of promoting production and dietary diversity are highlighted through commodity specific examples. The findings of this study may help strengthen operational linkages between agriculture production and nutrition for HGSF and other similar interventions.     

Antioxidant capacity and chemical constituents of Chinese jujube (Ziziphus jujuba Mill.) at different ripening stages

Chinese jujube (Ziziphus jujuba Mill.) is admired for its high nutritional value and has been commonly used in traditional Chinese medicine for its remarkable health functions. The antioxidant capacity (AOC) and the other qualitative parameters of jujube were measured at ripening stages of green maturity (GM), white maturity (WM), halfred maturity (HM), and red maturity (RM). AOC was screened with DPPH radical scavenging activity, Trolox equivalent antioxidant capacity, and reducing power. Jujube showed a significant (p<0.05) increase in the total soluble solids and titratable acidity, and firmness have no change of all maturity stages, while ascorbic acid showed a significant (p<0.05) declining trend. At stage of GM, the total phenolic content (TPC), total flavonoid content (TFC), and AOC in peel were the highest, and then rapidly decreased after WM. Meanwhile TPC and AOC in pulp reached a peak value in WM then declined, but TFC declined slowly during maturity.     

Carotenoid and chlorophyll composition of commonly consumed leafy vegetables in Mediterranean countries

Major chloroplast pigments in five leafy vegetables (chicory-Cichorium intybus, cv. ‘Anivip’ and cv. ‘Monivip’, dandelion-Taraxacum officinale, garden rocket-Eruca sativa and wild rocket-Diplotaxis tenuifolia), commonly consumed in Mediterranean countries, have been separated by high-performance liquid chromatography (HPLC) on a reversed-phase column. Three classes of pigments were identified and quantified: xanthophylls (oxygenated carotenoids), carotenes (hydrocarbon carotenoids) and chlorophylls. The contents of the pigments in the analysed leafy vegetables varied significantly. The results indicated that selected leafy vegetables were moderately rich in xanthophylls, primarily lutein (3.87–7.44 mg/100 g fwt). Other xanthophylls were detected in relatively small quantities. The provitamin A carotenoids (α- and β-carotene) were also detected, but α-carotene were not present in chicory cultivars and in dandelion. The ratio of chlorophyll a/b varied from 2.44 to 2.67 depending on the species. The highest content of all the analysed constituents was found in the garden rocket.     

常见蔬菜的黄酮含量及烹饪对其含量的影响

本实验目的在于了解我国辽宁省地区常见蔬菜的黄酮类物质含量及黄酮类物质在不同烹饪方式下的变化情况,为进一步估算膳食中黄酮类物质的摄入水平提供依据。结果表明,叶菜中黄酮类物质含量较高,花、果类和根、茎类次之。萝卜缨、韭菜、芹菜中黄酮类物质含量较高,分别达到39.18,36.26和32.20mg/100g。经过烹饪后,大部分蔬菜中黄酮类物质含量均有所增加,其中,中火炒制的烹饪方式使蔬菜中的黄酮含量增加得较为显著,增加幅度在12.11%～166.38%之间。增加绿叶蔬菜的摄入量,可获得充足的黄酮类物质,采用中火炒制的烹饪方式有利于黄酮类物质的释放。     

Comparison of three chosen vegetables with others from South East Asia for their lutein and zeaxanthin content

Three local leafy vegetables chekup manis (Sauropus androgynus), West Indian pea tree leaves (Sesbania grandiflora (L.) Pers.), and drumstick tree leaves (Moringa oleifera), are consumed by local South East Asian populations and are believed to have beneficial effects on improved vision and prevention of eye diseases. High performance liquid chromatography equipped with photodiode array detection was used to investigate their lutein and zeaxanthin contents, which were compared with those from other commonly found vegetables in the region. It was found that these three leafy vegetables contained significantly higher amounts of lutein namely, 19.5, 28.3, and 24.8 mg/100 g edible fresh leaves, respectively, compared to other vegetables in the region. It was also found that cooking in boiling water increase the extractable lutein content in chekup manis by almost 20%, within 4 min.     

Pesticide residues in leafy vegetables,stalk and stem vegetables from South Korea: a long-term study on safety and health risk assessment

South Korea has a unique food culture. South Koreans enjoy wrapping meat and eating or making kimchi (traditionally fermented Korean food) and eating using raw leafy vegetables, stalk and stem vegetables. Therefore, there is a high chance of being exposed to pesticide residues of vegetables. The objective of this study was to investigate pesticide residues in leafy vegetables, stalk and stem vegetables from South Korea. A total of 8496 samples were mainly collected from Gwangju and Jeonnam area (the largest production region of leafy vegetables, stalk and stem vegetables) in South Korea from 2010 to 2014. A total of 230 pesticides were used for multi-residue analysis of pesticides. Among 8496 samples, 61 different pesticides (1029 times) were detected in 890 samples, of which 118 samples (1.4%) exceeded the Korea maximum residue limits (MRLs). Samples exceeding the MRLs were mostly found in leafy vegetables (brassica lee ssp. namai, leafy lettuce, spinach, perilla leaves, crown daisy, marsh mallow, aster scaber, pimpinella brachycarpa) and Chinese chive. Procymidone, dimethomorph and azoxystrobin were the most frequently found pesticides. A risk assessment of pesticides exceeding the MRLs was evaluated by calculating the estimated daily intake (EDI) and the acceptable daily intake (ADI). The ratio of EDI to ADI was 0.003–30.4%.     

Is air-drying of plant-based food at low temperature really favorable? A meta-analytical approach to ascorbic acid,total phenolic,and total flavonoid contents

The aim of this work was to review the studies that evaluated the effect of drying temperature on the content of ascorbic acid (AA), total phenolic (TPC), and total flavonoid contents (TFC) in fruits and vegetables, and quantify whether drying at 40 °C is more favorable than at higher temperatures. For the purpose of this study, AA, TPC, and TFC values for 40 °C were compared with those obtained at 50 °C, 60 °C, and 70–80 °C. A meta-analysis was performed using the weighted response ratio calculated for each experiment. Despite the fact that other variables significantly influenced the nutrient content in individual experiments, the meta-analysis provided a general view on the effect of air-drying temperature on the quality of plant-based food products from outcomes of various studies.     

Evaluation of antioxidant potential in selected green leafy vegetables

Green leafy vegetables represent a class of underexploited plants that are stipulated to be rich sources of natural antioxidants. A fundamental study of free radical-scavenging activity in four plant species, namely Trigonella foenum-graecum, Centella asiatica, Sauropus androgynus and Pisonia alba, was carried out by measuring the ability of methanol extracts of these plants to scavenge radicals generated by in vitro systems and by their ability to inhibit lipid peroxidation. The levels of non-enzymatic antioxidants were also determined by standard spectrophotometric methods. Correlation and regression analysis established a positive correlation between some of these antioxidants and the in vitro free radical-scavenging activity of the plant extracts. The conclusions drawn from the study indicate that in vivo studies, isolation and analysis of individual bioactive components will reveal the crucial role that these plants may play in several therapeutic formulations.     

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.     

Spray-Drying of Antioxidant-Rich Blueberry Waste Extracts; Interplay Between Waste Pretreatments and Spray-Drying Process

This study aimed to establish an efficient route for converting blueberry waste material (BWM) into antioxidant-rich powders. Extracts were produced from BWM by an aqueous method using water acidified with citric acid, in the absence or presence of Pectinex Ultra SP-L and Cellubrix. All BWM extracts contained antioxidants including phenolic acids, anthocyanins, and flavonoids (total phenolic content (TPC) 3655–4369 mg gallic acid equivalent (GAE) and total anthocyanin content (TAC) 219–296 mg cyanidin-3-glucoside equivalents (CyGE) per 100 g dry extract). Extractions at 50 °C yielded higher TPC and TAC but lower vitamin C and pectin contents than extractions at 20 °C. Spray-drying BWM extracts produced at 50 °C (no enzymatic treatments) and an encapsulant (alginate or inulin) at an inlet temperature 150 °C and feed temperature 50 °C yielded powders with desired dark purplish blue color, water activity (0.25–0.33), flowability, reconstitution time (23–46 s in water or milk), TPC (25–30 mg GAE/g), TAC (17–20 mg CyGE/g), storage stability, and Bifidobacterium-boosting properties. Enzymatic pretreatments of BWM did not confer any advantages in preserving antioxidants in powder products, suggesting that some intrinsic BWM components (e.g., pectins) may play an important role in the encapsulating process. The use of alginate as the encapsulant/drying aid afforded higher powder yields, superior protection of antioxidants, better stability over a prolonged storage or elevated temperature storage, greater retention of TPC/TAC under simulated gastrointestinal conditions, and greater Bifidobacterium-boosting effects, compared to powders prepared using inulin. Thus, simple aqueous extraction methods and spray-drying technology hold enormous promise for producing antioxidant-rich powders from blueberry processing by-products or waste.