Food Phenolics, Pros and Cons: A Review

Phenolic compounds like simple phenols, flavonoids, and phenolic acids are commonly in foods of plant origin. Several studies, including animal and epidemiological investigations, have demonstrated that phenolic compounds in foods possess positive attributes such as anticarcinogenesis, antioxidant potential, antiviral activity, antimicrobial activity, and antimutagenic activity. However, other studies have shown that the same phenolics have negative attributes such as carcinogenic activity and antinutritional activity, as well as imparting negative attributes to foods. This review summarizes the information about food phenolics and presents the most current knowledge with respect to its role in human health, food attributes, and toxicity among others.     

Phenolics and related substances in alcohol-free beers

 The present study examines and compares the phenolic compositions of several commercially available alcohol-free and standard beers. In general, the values for the contents of the phenolic components in the alcohol-free beers are lower than the values for the standard beers; this is attributable to differences in the duration of fermentation and the yeast strains employed in brewing alcohol-free beers (e.g., the case of tyrosol) and to losses brought about by the dealcoholization processes employed (e.g., p-coumaric acid, caffeic acid, vanillic acid, etc.). The values for the other low-molecular-weight compounds considered, such as 5-(hydroxymethyl)furfural and tryptophol, are also lower in the alcohol-free than in the standard beers. Received: 16 July 1999     

Effect of oxygen reduction during malaxation on the quality of extra virgin olive oil (Cv. Carboncella) extracted through “two-phase” and “three-phase” centrifugal decanters

Quality and composition of virgin olive oil (VOO) are strictly dependent on complex processes that take place during the olive fruit crushing and malaxation of the olive paste. In this work, modulation of O₂ levels within malaxation chambers (R1: unmodified atmosphere; R2: oxygen: 12.73–4.64 kPa from the beginning to the end of malaxation; R3: 10.46–2.27 kPa; R4: 9.87–0.69 kPa) in two continuous “two-phase” and “three-phase” oil extraction plants was performed. Combined effects on the biosynthesis of nutritionally bioactive molecules and aroma volatiles and on the resulting sensory properties of the produced oils were investigated. Results showed that the type of oil extraction plant markedly affected the level of the phenolic compounds in the oil (and the related sensory attributes of bitter, pungency, astringency and bitter and pungency persistence). Reduction of O₂ concentration in the malaxing chamber, while having a minor impact on the presence of phenolic compounds, significantly affected the formation of all the examined volatiles. Particularly, lowered levels of oxygen hindered the formation of lipoxygenase derived volatiles weakening odours and flavours of artichoke, fresh fruity, and fresh cut grass.     

Phenolic compounds in plants and agri-industrial by-products: Antioxidant activity,occurrence, and potential uses

Phenolic compounds, ubiquitous in plants are an essential part of the human diet, and are of considerable interest due to their antioxidant properties. These compounds posses an aromatic ring bearing one or more hydroxyl groups and their structures may range from that of a simple phenolic molecule to that of a complex high-molecular weight polymer. Flavonoids, which bear the C₆–C₃–C₆ structure, account for more than half of the over eight thousand different phenolic compounds. The antioxidant activity of phenolic compounds depends on the structure, in particular the number and positions of the hydroxyl groups and the nature of substitutions on the aromatic rings. Fruits, vegetables and beverages are the major sources of phenolic compounds in the human diet. The food and agricultural products processing industries generate substantial quantities of phenolics-rich by-products, which could be valuable natural sources of antioxidants. Some of these by-products have been the subject of investigations and have proven to be effective sources of phenolic antioxidants. When tested in edible oils, and in fish, meat and poultry products, phenolic-rich extracts have shown antioxidant activities comparable to that of synthetic antioxidants. Practical aspects of extraction and production of sufficient amounts of natural antioxidants from most of these sources remain to be elucidated.     

Sclerocarya birrea (Marula), An African Tree of Nutritional and Medicinal Uses: A Review

Sclerocarya birrea (Anacardiaceae) is a popular African wild tree distributed in many African countries where the leaves, stem bark, root, and fruits are used in food and traditional medicine; the fruit is rich in ascorbic acid. The fruit juice contains sesquiterpene hydrocarbon, which are terpenes found in plants that are reported to have bacteriostatic properties. The fruit contains a hard brown seed. The seed encloses a soft white kernel rich in oil and protein. The oil contains oleic, palmitic, myristic, and stearic acids; the kernel protein contains amino acids, with a predominance of glutamic acid and arginine. The extracts from different parts showed high total phenolic compounds and radical-scavenging capacities and antioxidant activities. Sclerocarya birrea is widely studied with regard to its antidiabetic, anti-inflammatory, analgesic, antiparasitic, antimicrobial, and antihypertenisve activities.     

Phenolic composition of Flacourtia indica, Opuntia megacantha and Sclerocarya birrea

The phenolic acid composition of the peel and pulp of the fruits of Flacourtia indica (Burm. f.) Merr., Opuntia megacantha (L.) Mill and Sclerocarya birrea (A. Rich.) Hochst., from Zimbabwe, were analysed using traditional colorimetric as well as HPLC methods. The total phenolics, flavanoids and condensed tannin levels varied with species. Sclerocarya birrea pulp had the highest total phenolics, flavanoids and condensed tannins, i.e., 2262 μg GAE/g, 202 μg catechin/g and 6.0% condensed tannins, respectively. Flacourtia indica pulp contained the least total phenolics, flavanoids and condensed tannins 334 μg GAE/g, 41 μg catechin/g and 1.4%, respectively. There were no significant differences in the total phenolics between the peels and the pulps of the individual fruits. However, significant differences were noted in the flavanoids and the condensed tannins between the peels and pulps of the fruits assayed. Ferulic acid, caffeic acid and vanillic acid were the dominant phenolic acids in the three fruits. There were differences between the phenolic acids in the peels and the pulps of the fruits.     

热压制盐与真空制盐之优劣比较分析

本文通过对热压制盐原理的阐述和对国内曾经使用过的热压制盐得失剖析,提出将真空制盐和热压制盐两者结合采用,既能充分利用真空制盐电站余热,达到汽电平衡,又能发挥热压制盐的优势．更好地实现节能。     

Natural antioxidants and antioxidant capacity of Brassica vegetables: A review

Dietary antioxidants, such as water-soluble vitamin C and phenolic compounds, as well as lipid-soluble vitamin E and carotenoids, present in vegetables contribute both to the first and second defense lines against oxidative stress. As a result, they protect cells against oxidative damage, and may therefore prevent chronic diseases, such as cancer, cardiovascular disease, and diabetes. Brassica vegetables, which include different genus of cabbage, broccoli, cauliflower, Brussels sprouts, and kale, are consumed all over the world. This review focuses on the content, composition, and antioxidant capacity both lipid- and water-soluble antioxidants in raw Brassica vegetables. The effects of post-harvest storage, industrial processing, and different cooking methods on stability of bioactive components and antioxidant activity also are discussed.     

Emerging Role of Phenolic Compounds as Natural Food Additives in Fish and Fish Products

Chemical and microbiological deteriorations are principal causes of quality loss of fish and fish products during handling, processing, and storage. Development of rancid odor and unpleasant flavor, changes of color and texture as well as lowering nutritional value in fish can be prevented by appropriate use of additives. Due to the potential health hazards of synthetic additives, natural products, especially natural antioxidants and antimicrobial agents, have been intensively examined as safe alternatives to synthetic compounds. Polyphenols (PP) are the natural antioxidants prevalent in fruits, vegetables, beverages (tea, wine, juices), plants, seaweeds, and some herbs and show antioxidative and antimicrobial activities in different fish and fish products. The use of phenolic compounds also appears to be a good alternative for sulphiting agent for retarding melanosis in crustaceans. Phenolic compounds have also been successfully employed as the processing aid for texture modification of fish mince and surimi. Thus, plant polyphenolic compounds can serve as potential additives for preventing quality deterioration or to retain the quality of fish and fish products.     

Protective effects of phenolic constituents from Cytisus multiflorus,Lamium album L. and Thymus citriodorus on liver cells

The present study investigated the antioxidant and cytoprotective effects of purified ethanolic extracts of Cytisus multiflorus, Lamium album L. and Thymus citriodorus plants. These extracts showed high antioxidant activity in DPPH and reducing power assays. Using a model of chemical stress induced by potassium dichromate (DK) in human hepatoblastoma HepG2 cells, 50 μg/mL of C. multiflorus, L. album and T. citriodorus extracts decreased the rate of reactive oxygen species (ROS) production by 35%, 26% and 20%, respectively, when exposed to 25 μM of DK. This effect was also observed for the treatment of cells with individual polyphenolic compounds determined in the extracts, or with mixtures prepared with individual polyphenolic compounds simulating the phenolic composition of the extracts. Additionally, the purified ethanolic extracts and the prepared polyphenolic mixtures showed a cytoprotective effect against DK-induced toxicity. The overall results emphasize the contribution of polyphenols in antioxidant and cytoprotective properties of the studied plants.     

Sweet cherry: Composition,postharvest preservation,processing and trends for its future use

BackgroundSweet cherries (Prunus avium L.) are a nutritious fruit which are rich in polyphenols and have high antioxidant potential. Most sweet cherries are consumed fresh and a small proportion of the total sweet cherries production is value added to make processed food products. Sweet cherries are highly perishable fruit with a short harvest season, therefore extensive preservation and processing methods have been developed for the extension of their shelf-life and distribution of their products.Scope and approachIn this review, the main physicochemical properties of sweet cherries, as well as bioactive components and their determination methods are described. The study emphasises the recent progress of postharvest technology, such as controlled/modified atmosphere storage, edible coatings, irradiation, and biological control agents, to maintain sweet cherries for the fresh market. Valorisations of second-grade sweet cherries, as well as trends for the diversification of cherry products for future studies are also discussed.Key findings and conclusionsSweet cherry fruit have a short harvest period and marketing window. The major loss in quality after harvest include moisture loss, softening, decay and stem browning. Without compromising their eating quality, the extension in fruit quality and shelf-life for sweet cherries is feasible by means of combination of good handling practice and applications of appropriate postharvest technology. With the drive of health-food sector, the potential of using second class cherries including cherry stems as a source of bioactive compound extraction is high, as cherry fruit is well-known for being rich in health-promoting components.     

National Food Control Systems: A Review

This article reviews literature on national food control systems (NFCS). The major objectives of NFCS, their main components, and current issues relating to NFCS are discussed. Common problem areas and the actions taken by countries to improve their system are analysed. The review shows that elements of NFCS suffer from certain limitations, such as obsolete food laws, duplication of work, lack of resources, and poor organisation, which make the system ineffective. NFCS have been established to various extents in both developed and developing countries; however, most countries have not used management techniques in developing and implementing their food control programme. Since NFCS face a number of challenges, it is important for both developed and developing countries to strengthen their food control systems to meet these challenges.     

National Food Control Systems: A Review

This article reviews literature on national food control systems (NFCS). The major objectives of NFCS, their main components, and current issues relating to NFCS are discussed. Common problem areas and the actions taken by countries to improve their system are analysed. The review shows that elements of NFCS suffer from certain limitations, such as obsolete food laws, duplication of work, lack of resources, and poor organisation, which make the system ineffective. NFCS have been established to various extents in both developed and developing countries; however, most countries have not used management techniques in developing and implementing their food control programme. Since NFCS face a number of challenges, it is important for both developed and developing countries to strengthen their food control systems to meet these challenges.     

Nutritional compositions and health promoting phytochemicals of camu-camu (myrciaria dubia) fruit: A review

Camu-camu (Myrciaria dubia) fruits are promising sources of various bioactive compounds such as vitamin C, phenolic compounds and carotenoids. Camu-camu fruits are also good sources of potassium, iron, calcium, phosphorous and various kinds of amino acids such as serine, valine and leucine. Therefore, the presence of different bioactive compounds in camu-camu fruits could be used to retard or prevent various diseases such as cardiovascular and cancer. This is an update report on nutritional compositions and health promoting phytochemicals of camu-camu fruits. This review reveals that camu-camu fruits might be used as functional foods or for nutraceutical purposes.     

Nonthermal Food Processing Alternatives and Their Effects on Taste and Flavor Compounds of Beverages

Food drinks are normally processed to increase their shelf-life and facilitate distribution before consumption. Thermal pasteurization is quite efficient in preventing microbial spoilage of many types of beverages, but the applied heat may also cause undesirable biochemical and nutritious changes that may affect sensory attributes of the final product. Alternative methods of pasteurization that do not include direct heat have been investigated in order to obtain products safe for consumption, but with sensory attributes maintained as unchanged as possible. Food scientists interested in nonthermal food preservation technologies have claimed that such methods of preserving foods are equally efficient in microbial inactivation as compared with conventional thermal means of food processing. Researchers in the nonthermal food preservation area also affirm that alternative preservation technologies will not affect, as much as thermal processes, nutritional and sensory attributes of processed foods. This article reviews research in nonthermal food preservation, focusing on effects of processing of food drinks such as fruit juices and dairy products. Analytical techniques used to identify volatile flavor-aroma compounds will be reviewed and comparative effects for both thermal and nonthermal preservation technologies will be discussed.     

Phenolics from hull of Garcinia mangostana fruit and their antioxidant activities

The air-dried fruit hulls of Garcinia mangostana Linn. were extracted with 70% MeOH, and then partitioned into the n-BuOH fractions. Furthermore, three major phenolic components related to their antioxidant activities were purified by silica gel column chromatography and Sephadex LH-20 and then identified as P₁ (1,3,6,7-tetrahydroxy-2,8-(3-methyl-2-butenyl)), P₂ [1,3,6-trihydroxy-7-methoxy-2,8-(3-methyl-2-butenyl) xanthone] and P₃ (epicatechin) using UV–visible spectrophotometry, IR spectrophotometry and NMR spectroscopy, respectively. The antioxidant activities of three major phenolics were evaluated using different tests, including the free radical scavenging capability and total antioxidant activity in a linoleic acid peroxidation. These three phenolic compounds exhibited different antioxidant activities in these antioxidant tests. The hydroxyl radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capabilities and the activity against linoleic acid peroxidation of P₁ were greater than those of P₂ and P₃, while the superoxide anion radical scavenging activity of P₃ was greater than that of P₁, but was close to that of P₂ or α-tocopherol. An activity-guided isolation and purification process was used to identify the components showing the strong DPPH radical scavenging activity from G. mangostana Linn.     

A Comparative Study of Phenolic Content in Apple Fruits

The ethanol extracts of apple fruits harvested from the cultivars Aldas, Auksis, Ligol, and Lodel grown in Lithuania were analyzed by the high-performance liquid chromatography method. Chlorogenic acid was found to be a predominant component in the apple fruits of all the cultivars, except the cultivar Ligol. (–)-Epicatechin was the major compound in the ethanol extracts of apple fruits obtained from all the cultivars, while the amount of (+)–catechin was lower. The following quercetin glycosides were identified and quantified: hyperoside, isoquercitrin, avicularin, rutin, and quercitrin. Hyperoside was the major quercetin glycoside in apple fruits.     

High-performance liquid chromatography-diode array detector determination and availability of phenolic compounds in 10 genotypes of walnuts

Walnuts contain signi?cant amounts of bioactive compounds such as polyphenols. The aim of the present study was to determine the differences in phenolic composition and polyphenolic in vitro availability of 10 genotypes of walnuts. All analyzed genotypes showed high flavonoid and non-flavonoid phenolic compounds, especially Eureka and Tehama genotypes. Ellagic acid and syringic acid were the mayor non-flavonoids. Regarding flavonoids, catechin and procyanidin B₂ were the most abundant, covering about 98% of total flavonoids. The in vitro digestion showed flavonoids as the most available polyphenols, especially catechin, gallocatechin, and epigallocatechin gallate.