From lesser‐known to super vegetables: the growing profile of African traditional leafy vegetables in promoting food security and wellness

There are hundreds of traditional leafy vegetables and wild food plants of horticultural and nutritional significance in Africa. These lesser‐known crops and wild food plants that are highly adapted to harsh growing conditions thrive with little care and are available when other sources of food fail or are out of season. They are rich in micronutrients and are often the cheapest sources of many essential vitamins and minerals in many localities. Many of them are very important functional foods in African traditional diets and are rich in nutraceuticals, including polyphenols, tannins, flavonoids and flavonols, that exert demonstrable antioxidant, free radical scavenging and enzyme inhibition activities and have antimicrobial properties that provide scientific justification and possible mechanisms for their use in the management of a wide range of ailments, including diet‐related, non‐communicable diseases such as diabetes, hypertension and cardiovascular diseases. African traditional leafy vegetables are invaluable in promoting food security and wellness in Africa on account of their availability and affordability, their great nutritional value, chemotherapeutic and health‐promoting properties and other unique qualities. Long recognised by the rural populace as quality food items, they are becoming more popular even with the more affluent urban elites. There is the need to develop improved management practices for these super vegetables to promote their cultivation and boost their exploitation for food security and wellness in Africa. © 2018 Society of Chemical Industry     

Effects of Nonthermal Plasma Technology on Functional Food Components

Understanding the impact of nonthermal plasma (NTP) technology on key nutritional and functional food components is of paramount importance for the successful adoption of the technology by industry. NTP technology (NTPT) has demonstrated marked antimicrobial efficacies with good retention of important physical, chemical, sensory, and nutritional parameters for an array of food products. This paper presents the influence of NTPT on selected functional food components with a focus on low‐molecular‐weight bioactive compounds and vitamins. We discuss the mechanisms of bioactive compound alteration by plasma‐reactive species and classify their influence on vitamins and their antioxidant capacities. The impact of NTP on specific bioactive compounds depends both on plasma properties and the food matrix. Induced changes are mainly associated with oxidative degradation and cleavage of double bonds in organic compounds. The effects reported to date are mainly time‐dependent increases in the concentrations of polyphenols, vitamin C, or increases in antioxidant activity. Also, improvement in the extraction efficiency of polyphenols is observed. The review highlights future research needs regarding the complex mechanisms of interaction with plasma species. NTP is a novel technology that can both negatively and positively affect the functional components in food.     

Chemical,biochemical, and biological significance of polyphenols in cereals and legumes

Polyphenols in cereals and legumes have been receiving considerable attention largely because of their adverse influence on color, flavor, and nutritional quality. These compounds belong to the flavonoid and tannin groups and are mostly located in the seed coat or pericarp of the grains. The pearl millet flavonoids have been identified as C‐glycosylflavones by the combined use of paper chromatography and UV spectroscopy. Although nontoxic, physiological and nutritional significance of these compounds occurring in high amounts in the pearl millet grain are still not clearly understood. In view of aesthetic quality, bleaching of the millet grains in acidic solution is recommended. A large proportion of current assays involves spectrophotometry of tannin or its chromogen and tannin‐protein interaction. Sorghum and legume tannins have been characterized as condensed tannins. Several factors such as plant type, age of the plant or plant parts, stage of development, and environmental conditions govern the polyphenol contents in plants. Polyphenols are known to interact with proteins and form tannin‐protein complexes leading to either inactivation of enzymes or making proteins insoluble. These are implicated in decreasing the activities of digestive enzymes, protein and amino acid availabilities, mineral uptake, vitamin metabolism, and depression of growth. Polyphenols are known to cause certain ultrastructural changes in the different parts of experimental animals. A correlation between dietary tannins and occurrence of esophageal cancer has been established. Bird resistance and seed germination in food crops have been correlated to high contents of polyphenols. The antinutritional activity of polyphenols can be reduced by removing polyphenols from the grains by chemical treatments or removing pericarp and testa by pearling. Treatment of alkaline reagents and ammonia can remove 90% of the polyphenols. Supplementation of polyphenols‐rich diet with protein can alleviate the growth‐depressing effect of polyphenols.     

香蕉单宁的提取、结构及功能研究进展

单宁作为植物多酚家族的一员,具有抗氧化、抗肿瘤和抗炎症等生理活性,被广泛应用于食品、医药和制革等行业中。香蕉是“世界四大水果”之一,被证明含有丰富的单宁,但鲜有关于香蕉单宁近年来研究进展的总结。因此,本文对香蕉单宁的提取、结构及功能研究进展进行系统性综述。目前,关于香蕉单宁提取工艺的研究主要围绕溶剂提取法、超声波辅助提取法、微波辅助提取法和酶辅助提取法展开,化学结构研究包括对其分子质量分布、聚合度范围、主要化学组成、结构单元及其连接方式的阐明,而功能活性研究则集中在评价香蕉单宁的抗氧化、抗菌、降血脂、降血糖、降低农药对机体毒性、结合金属离子和吸收紫外线等方面的作用。最后,对香蕉单宁今后的研究方向趋势提出展望,以期为扩大其在食品行业中的应用提供一定的理论指导。     

Natural phenolic antioxidants electrochemistry: Towards a new food science methodology

Natural phenolic compounds are abundant in the vegetable kingdom, occurring mainly as secondary metabolites in a wide variety of chemical structures. Around 10,000 different plant phenolic derivatives have been isolated and identified. This review provides an exhaustive overview concerning the electron transfer reactions in natural polyphenols, from the point of view of their in vitro antioxidant and/or pro‐oxidant mode of action, as well as their identification in highly complex matrixes, for example, fruits, vegetables, wine, food supplements, relevant for food quality control, nutrition, and health research. The accurate assessment of polyphenols’ redox behavior is essential, and the application of the electrochemical methods in routine quality control of natural products and foods, where the polyphenols antioxidant activity needs to be quantified in vitro, is of the utmost importance. The phenol moiety oxidation pathways and the effect of substituents and experimental conditions on their electrochemical behavior will be reviewed. The fundamental principles concerning the redox behavior of natural polyphenols, specifically flavonoids and other benzopyran derivatives, phenolic acids and ester derivatives, quinones, lignins, tannins, lignans, essential oils, stilbenes, curcuminoids, and chalcones, will be described. The final sections will focus on the electroanalysis of phenolic antioxidants in natural products and the electroanalytical evaluation of in vitro total antioxidant capacity.     

Bioactive Natural Constituents from Food Sources—Potential Use in Hypertension Prevention and Treatment

Prevention and management of hypertension are the major public health challenges worldwide. Uncontrolled high blood pressure may lead to a shortened life expectancy and a higher morbidity due to a high risk of cardiovascular complications such as coronary heart disease (which leads to heart attack) and stroke, congestive heart failure, heart rhythm irregularities, and kidney failure etc. In recent years, it has been recognized that many dietary constituents may contribute to human cardiovascular health. There has been an increased focus on identifying these natural components of foods, describing their physiological activities and mechanisms of actions. Grain, vegetables, fruits, milk, cheese, meat, chicken, egg, fish, soybean, tea, wine, mushrooms, and lactic acid bacteria are various food sources with potential antihypertensive effects. Their main bioactive constituents include angiotensin I-converting enzyme (ACE) inhibitory peptides, vitamins C and E, flavonoids, flavanols, cathecins, anthocyanins, phenolic acids, polyphenols, tannins, resveratrol, polysaccharides, fiber, saponin, sterols, as well as K, Ca, and P. They may reduce blood pressure by different mechanisms, such as ACE inhibition effect, antioxidant, vasodilatory, opiate-like, Ca²⁺ channel blocking, and chymase inhibitory activities. These functional foods may provide new therapeutic applications for hypertension prevention and treatment, and contribute to a healthy cardiovascular population. The present review summarizes the antihypertensive food sources and their bioactive constituents, as well as physiological mechanisms of dietary products, especially focusing on ACE inhibitory activity.     

Effects of edible plant polyphenols on gluten protein functionality and potential applications of polyphenol–gluten interactions

Expanding plant‐based protein applications is increasingly popular. Polyphenol interactions with wheat gluten proteins can be exploited to create novel functional foods and food ingredients. Polyphenols are antioxidants, thus generally decrease gluten strength by reducing disulfide cross‐linking. Monomeric polyphenols can be used to reduce dough mix time and improve flexibility of the gluten network, including to plasticize gluten films. However, high‐molecular‐weight polyphenols (tannins) cross‐link gluten proteins, thereby increasing protein network density and strength. Tannin–gluten interactions can greatly increase gluten tensile strength in dough matrices, as well as batter viscosity and stability. This could be leveraged to reduce detrimental effects of healthful inclusions, like bran and fiber, to loaf breads and other wheat‐based products. Further, the dual functions of tannins as an antioxidant and gluten cross‐linker could help restructure gluten proteins and improve the texture of plant‐based meat alternatives. Tannin–gluten interactions may also be used to reduce inflammatory effects of gluten experienced by those with gluten allergies and celiac disease. Other potential applications of tannin–gluten interactions include formation of food matrices to reduce starch digestibility; creation of novel biomaterials for edible films or medical second skin type bandages; or targeted distribution of micronutrients in the digestive tract. This review focuses on the effects of polyphenols on wheat gluten functionality and discusses emerging opportunities to employ polyphenol–gluten interactions.     

Enhancement of Attributes of Cereals by Germination and Fermentation: A Review

The nutritional quality of cereals and the sensorial properties of their products are sometimes inferior as compared to other sources of food which is due to the lower protein content and starch availability, the presence of determined antinutrients (phytic acid, tannins, and polyphenols) and the coarse nature of the grains. To ameliorate the nutritional qualities of cereals, they are processed in a number of ways. This review summarizes the enhancement in the nutritional value as well as the functional characteristics of cereals due to germination and fermentation treatment. The protein concentration increases and the amino acid profile is balanced by germination and fermentation. The antinutritional factors are reduced increasing the mineral availability from the cereals. Germination enhances the quality of nutrients and bioactive compounds of cereals thereby increasing the content in proteins, amino acids, sugars, and vitamins. The functional properties of cereals is enhanced due to generation of biofunctional substances, increase in protein solubility, in vitro protein digestibility and lowering of glycemic index.     

Natural astringency in foodstuffs — A molecular interpretation

The structures of plant polyphenols (vegetable tannins) are briefly reviewed. Their interactions with proteins, polysaccharides, and the alkaloid caffeine are discussed at the molecular level, and these fundamental properties are related to the quality of astringency that polyphenols possess. The various ways in which astringency may be modified and ultimately lost are outlined in relation to the aging of red wines, the formation of nonbiological hazes in beers and lagers, and the ripening of fruit.     

Bioactive Components and Health-Promoting Properties of Yuzu (Citrus ichangensis × C. reticulate)

Yuzu (Citrus ichangensis × C. reticulate) fruit is an important functional food that possesses several health-promoting properties. It has been widely used in commercial medical products, healthy foods, and cosmetics in many countries. Yuzu is a rich source of wide variety of non-nutritive compounds, such as flavonoids, anthocyanins, phenolic acids, carotenoids, and tannins; as well as nutritive compounds such as sugars, proteins, vitamins, fibers, and minerals. Yuzu fruit (juice, peel, and seeds) and its bioactive compounds have been demonstrated to have numerous functional properties, such as antioxidant, anti-inflammatory, anticancer, antiplatelet, angiogenesis, and antimicrobial properties, both in vitro and in vivo. These diverse applications provided by the yuzu fruit (juice, peel, and seeds) and its bioactive compounds are of great industrial importance. This review summarizes the composition, nutritional values, and functional properties of yuzu fruit, and their biological activity in relation to their potential impact on human health.     

豌豆多酚的组成、提取和生理活性的研究进展

豌豆多酚是广泛存在于豌豆中的次级代谢产物,主要包括黄酮（白杨素、山奈酚、槲皮素）、酚酸（对香豆酸、芥子酸、阿魏酸）和单宁（儿茶素）3类组分。豌豆多酚的含量、种类及分布取决于豌豆品种,但在其生长过程中又受到环境和诱导因素的影响。豌豆多酚的提取方法由低效的溶剂萃取法,逐步向高效率、高提取率的微波萃取技术转变,其生理活性研究也逐步向分子和细胞水平发展,应用范围逐渐扩展至肉制品、水产品及面制品等产业中。为进一步了解豌豆多酚的化学性质及潜在利用价值,本文对豌豆中多酚的分布,影响豌豆多酚种类和含量的因素,豌豆多酚的分离提取、生理活性及其在食品工业中的应用进行了详细阐述,以期为豌豆多酚的开发与研究提供理论依据。     

Antimicrobial Effects of Quillaja saponaria Extract Against Escherichia coli O157:H7 and the Emerging Non‐O157 Shiga Toxin‐Producing E. coli

Natural alternate methods to control the spread of Shiga toxin‐producing Escherichia coli (STEC) are important to prevent foodborne outbreaks. Quillaja saponaria aqueous bark extracts (QE), cleared by the U.S. Food and Drug Administration as a natural flavorant, contain bioactive polyphenols, tannins, and tri‐terpenoid saponins with anti‐inflammatory and antimicrobial activity. The objective of this study was to determine the effects of commercial QE against E. coli O157:H7 and non‐O157 strains over 16 h at 37 °C and RT. Overnight cultures of 4 E. coli O157:H7 strains and 6 non‐O157 STECs in Tryptic Soy Broth (TSB) were washed and resuspended in phosphate‐buffered saline (PBS, pH 7.2), and treated with QE and controls including citric acid (pH 3.75), sodium benzoate (0.1% w/w), acidified sodium benzoate (pH 3.75) or PBS for 6 h or 16 h. Recovered bacteria were enumerated after plating on Tryptic Soy Agar, from duplicate treatments, replicated thrice and the data were statistically analyzed. The 4 QE‐treated E. coli O157:H7 strains from initial ～7.5 log CFU had remaining counts between 6.79 and 3.5 log CFU after 16 h at RT. QE‐treated non‐O157 STECs showed lower reductions with remaining counts ranging from 6.81 to 4.55 log CFU after 16 h at RT.  Incubation at 37 °C caused reduction to nondetectable levels within 1 h, without any significant reduction in controls. Scanning electron microscopy studies revealed damaged cell membranes of treated bacteria after 1 h at 37 °C. QE shows potential to control the spread of STECs, and further research in model food systems is needed.     

Fruits,Vegetables, and Their Components and Mild Cognitive Impairment and Dementia: A Review

The aim of this review is to evaluate the current literature on the role of fruit and vegetable (F&V) consumption and their components in the prevention of mild cognitive impairment (MCI) and dementia. The components investigated include vitamins C and E, carotenoids, polyphenols, and B vitamins. There is little research evaluating F&V intake and MCI. Studies find inconsistent relationships between F&V and their components and cognitive decline and dementia. Inconsistencies throughout the research on F&V and their components do not allow for strong conclusions to be made at this time regarding their influence on cognitive function. However, F&V should still be considered an important component of a healthy diet.     

Mung Bean: Technological and Nutritional Potential

Mung bean (Vigna radiata (L.) R. Wilczek) has been intensively researched; scattered data are available on various properties. Data on physical, chemical, food processing, and nutritional properties were collected for whole mung bean grains and reviewed to assess the crop's potential as food and to set research priorities. Results show that mung bean is a rich source of protein (14.6–33.0 g/100 g) and iron (5.9–7.6 mg/100 g). Grain color is correlated with compounds like polyphenols and carotenoids, while grain hardness is associated with fiber content. Physical properties like grain dimensions, sphericity, porosity, bulk, and true density are related to moisture content. Anti-nutrients are phytic acid, tannins, hemagglutinins, and polyphenols. Reported nutrient contents vary greatly, the causes of which are not well understood. Grain size and color have been associated with different regions and were used by plant breeders for selection purposes. Analytical methods require more accuracy and precision to distinguish biological variation from analytical variation. Research on nutrient digestibility, food processing properties, and bioavailability is needed. Furthermore, the effects of storage and processing on nutrients and food processing properties are required to enable optimization of processing steps, for better mung bean food quality and process efficiency.     

Exploitation of dietary tannins to improve rumen metabolism and ruminant nutrition

Tannins (hydrolysable and condensed tannin) are polyphenolic polymers of relatively high molecular weight with the capacity to form complexes mainly with proteins due to the presence of a large number of phenolic hydroxyl groups. They are widely distributed in nutritionally important forage trees, shrubs and legumes, cereals and grains, which are considered as anti‐nutritional compounds due to their adverse effects on intake and animal performance. However, tannins have been recognised to modulate rumen fermentation favourably such as reducing protein degradation in the rumen, prevention of bloat, inhibition of methanogenesis and increasing conjugated linoleic acid concentrations in ruminant‐derived foods. The inclusion of tannins in diets has been shown to improve body weight and wool growth, milk yields and reproductive performance. However, the beneficial effects on rumen modulation and animal performance have not been consistently observed. This review discusses the effects of tannins on nitrogen metabolism in the rumen and intestine, and microbial populations (bacteria, protozoa, fungi and archaea), metabolism of tannins, microbial tolerance mechanisms to tannins, inhibition of methanogenesis, ruminal biohydrogenation processes and performance of animals. The discrepancies of responses of tannins among different studies are attributed to the different chemical structures (degree of polymerisation, procyanidins to propdelphinidins, stereochemistry and C? C bonding) and concentrations of tannins, and type of diets. An establishment of structure–activity relationship would be required to explain differences among studies and obtain consistent beneficial tannin effects. Copyright © 2010 Society of Chemical Industry     

Effects of artificial lighting on bioactivity of sweet red pepper (Capsicum annuum L.)

Recent studies have shown that artificial light effectively promotes the growth and development of red peppers when light spectra, intensities and duration are controlled. Cited reports deal mostly with studies involving with the growth stages of pepper. Changes in the biochemical status of plants were not studied. Therefore, this study focuses on the changes in the content of some bioactive compounds (polyphenols, flavonoids, tannins, ascorbic acid and antioxidant capacities) after artificial lightening [high‐pressure sodium and light‐emitting plasma (LEP) lamps] during the cultivation of sweet red pepper. The bioactive compounds differ slightly, depending on the source of light. Fluorescence spectra showed higher binding properties of LEP polyphenol extracts to human serum albumin (HSA) than other samples. FTIR peaks were similar in their polyphenols region for all investigated samples.     

Nutrient content,in vitro ruminal fermentation characteristics and methane reduction potential of tropical tannin‐containing leaves

BACKGROUND: Plant tannins as rumen modifiers are better than chemicals or antibiotic‐based modifiers since these compounds are natural products which are environmentally friendly and therefore have a better acceptance with regard to feed safety issues. Tropical plants containing phenols such as tannins were found to suppress or eliminate protozoa from the rumen and reduce methane and ammonia production. The screening of these plants is an important step in the identification of new compounds and feed additives which might contribute to mitigate rumen methanogenesis. The present study was carried out to determine the efficacy of tannins from tropical tree leaves for their methane reduction properties. RESULTS: Activity of tannins, as represented by the increase in gas volume with the addition of polyethylene glycol (PEG)‐6000 as a tannin binder (tannin bioassay) was highest in Ficus bengalensis (555%), followed by Azardirachta indica (78.5%). PEG addition did not alter (P > 0.05) methane percentage in Ficus racemosa, Glyricidia maculata, Leucena leucocephala, Morus alba and Semaroba glauca, confirming that tannins in these samples did not affect methanogenesis. The increase (P < 0.05) in protozoa population with PEG was maximal in Ficus religiosa (50), followed by Moringa oleifera (31.2), Azardirachta indica (29.9) and Semaroba glauca (27.5). There was no change (P > 0.05) in the protozoa population in Autocarpus integrifolia, Ficus bengalensis, Jatropha curcus, Morus alba and Sesbania grandiflora, demonstrating that methane reduction observed in these samples per se was not due to defaunation effect of the tannin. The increase in total volatile fatty acid concentration in samples with PEG ranged from 0.6% to > 70%. The highest increase (%) in NH₃‐N was recorded in Azardirachta indica (67.4), followed by Ficus mysoriensis (35.7) and Semaroba glauca (32.6) leaves, reflecting strong protein binding properties of tannin. CONCLUSION: The results of our study established that in vitro methanogenesis was not essentially related to the density of protozoa population. Tropical tree leaves containing tannins such as Autocarpus integrifolia, Jatropha curcus and Sesbania grandiflora have the potential to suppress methanogenesis. Therefore tannins contained in these plants could be of interest in the development of new additives in ruminant nutrition. Copyright © 2012 Society of Chemical Industry     

Consumption,intake patterns,and exposure

Despite the wide public and scientific interest in antioxidant nutrients and their roles in disease prevention, limited data are available to assess population consumption, individuals’ intake patterns, and trends in exposure. This article reviews data on levels of these nutrients in the food supply, intake patterns from food and supplement use derived from national surveys, and trends in exposure. The food supply and intake data indicate that levels of vitamins E and C and the carotenoids in the diet have increased since the 1970s, but the increases are not consistent among all age groups. Dietary supplements make a major contribution to intakes of vitamins E and C. Nutrient and nonnutrient antioxidants added to the food supply do not contribute appreciably to antioxidant exposure. Groups at high risk of poor dietary intakes of antioxidant nutrients are the poor, tobacco users, nonsupplement users, and the elderly, especially those living alone.     

多酚的功能性质及与蛋白质、多糖相互作用研究进展

多酚是具有多种化学结构的多相分子群,具有很强的抗氧化性、抗菌性以及预防慢性疾病的能力,在食品和医疗领域具有广泛的应用价值。多酚由于含有多个酚羟基基团使其化学稳定性差,生物利用度低,在功能性食品中的应用受到了限制。蛋白质、多酚、多糖相互作用所形成的复合结构能够有效地提高食品的感官品质以及各生物大分子的功能特性。本文对多酚的结构与功能之间的关系,多酚与蛋白质、多糖三者相互作用的机理,多酚对二者功能性质及对改善乳化液性质的影响,进行了综述,以期为多酚在食品工业中的应用提供理论参考。     

12‐Lipoxygenase activity in the muscle tissue of Atlantic mackerel (Scomber scombrus) and its prevention by antioxidants

Lipoxygenase was prepared from Atlantic mackerel muscle using differential centrifugation, ammonium sulphate precipitation and gel permeation (phenyl Sephadex G‐50) column chromatography. The crude lipoxygenase enzyme preparation was characterised by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE), which showed two prominent bands with molecular weights of 119 and 125 kDa. Fractions collected from the chromatography column were tested for enzyme activity by reacting with arachidonic acid and determining the production of hydroxyeicosatetraenoic acid (12‐HETE) using reverse phase HPLC and GC–MS. The 12‐HETE peak was absent from the fresh arachidonic acid control sample and from arachidonic acid treated with heat‐inactivated lipoxygenase. Esculetin, a known inhibitor of lipoxygenase, inhibited the production of 12‐HETE from the reaction of lipoxygenase with arachidonic acid, thus confirming that the enzyme was lipoxygenase. The HETE peak was partially reduced in the presence of antioxidants, namely synthetic butylated hydroxytoluene (BHT) and natural antioxidants vitamins C and E. The presence of lipoxygenase in Atlantic mackerel muscle indicates the possibility that the lipid oxidation mechanism is initiated enzymatically in chilled and frozen stored fillets of mackerel and that this oxidative deterioration could be inhibited by antioxidants (BHT, vitamins C and E) which are used widely in the food industry. © 2001 Society of Chemical Industry