Showing papers in "Journal of the Science of Food and Agriculture in 2001"

Phenolic compounds and related enzymes as determinants of quality in fruits and vegetables

Abstract: Phenolic secondary metabolites play an important role in plant-derived food quality, as they affect quality characteristics such as appearance, flavour and health-promoting properties. Their content in foods is affected by many factors that influence phenolic stability, biosynthesis and degradation. In terms of their biosynthesis the key enzyme phenylalanine ammonia-lyase (PAL) is especially relevant, as it can be induced by different stress (environmental) conditions. In addition, polyphenol oxidases (PPO) and peroxidases (POD) are the main enzymes responsible for quality loss due to phenolic degradation. The different factors affecting phenolic-related food quality are reviewed. These include internal (genetic) and environmental (agronomic) factors, technological treatments applied during postharvest storage of fruits and vegetables, as well as processing and storage of the processed products. The different strategies that are required to either maintain or enhance the phenolic-related quality of foods are critically reviewed. Genetic modification designed to decrease polyphenol oxidases or peroxidases is not always a feasible method, owing to side problems related to the growth and defence of the plant. Agronomic treatments can be used to enhance the phenolic content and pigmentation of fruits and vegetables, although the information available on this topic is very scarce and even contradictory. Some postharvest treatments (cold storage, controlled or modified atmospheres, etc) can also improve phenolic-related quality, as well as new processing methods such as irradiation (gamma, UV), high-field electric pulses, high hydrostatic pressures and microwaves. Les composes phenoliques, metabolites secondaires des plantes, jouent un role dans la qualite des fruits, au niveau de l'apparence, de la flaveur et des qualites nutritives. L'enzyme cle de leur biosynthese est la phenylalanine ammonium-lyase, regulee par les facteurs environnementaux. La polyphenol oxydase et la peroxydase sont responsables des degradations donc des pertes de qualite. Les differents facteurs internes (genetiques) et externes (agronomiques) affectant la qualite des produits vegetaux sont etudies. Les differentes mesures envisageables (modification genetique, traitements chimiques ou physiques apres recolte) pour modifier le contenu en compose phenoliques et donc la qualite des produits vegetaux sont etudies.

Flaxseed as a functional food source

Abstract: Flaxseed is emerging as one of the key sources of phytochemicals in the functional food arena. In addition to being one of the richest sources of α-linolenic acid oil and lignans, flaxseed is an essential source of high-quality protein and soluble fibre and has considerable potential as a source of phenolic compounds. The implications of diets containing flaxseed or its components for human nutrition and disease prevention are analysed in this paper. Results of the first meta-analysis examining the relationship between intake of flaxseed or its components and risk reduction of disease in humans is presented. Some areas of potential opportunities and impact of using flaxseed or its components in the diet are highlighted. Les graines de lins sont une source de produits fonctionnels: outre leur richesse en acide α-linolenique et en lignanes, elles contiennet des proteines vegetales de haute qualite, des fibres solubles et de nombreux compose phenoliques. Les effets d'un regime alimentaire enrichi en graines de lins ou en ses composants est etudie ici, chez l'homme. les etudes epidemiologiques montrent un effet cardioprotecteur et anticarcinogene.

Organic agriculture: does it enhance or reduce the nutritional value of plant foods?

Abstract: The possible differences between organic and conventional plant products are examined from the view of possible effects on human health. It is concluded that nutritionally important differences relating to contents of minerals, vitamins, protein and carbohydrates are not likely, primarily since neither of these are deficient in typical first world diets, nor are present levels of pesticide residues in conventional products cause for concern. However, there is reason to believe that contents of many defence related secondary metabolites in the diet are lower than optimal for human health, even for those where too high levels are known to be harmful. High biological activity resulting in adverse effects on growth of animals and children may be directly linked with promotion of longevity. There is ample, but circumstantial, evidence than on average organic vegetables and fruit most likely contain more of these compounds than conventional ones, allowing for the possibility that organic plant foods may in fact benefit human health more than corresponding conventional ones. The authors define testable scientific hypotheses, which should be further investigated to provide more definitive answers to the question.

Antioxidant activity of fresh and processed edible seaweeds

Abstract: The antioxidant activity of aqueous/organic extracts of processed and raw edible seaweeds was determined using three methods, namely (a) free radical (DPPH·) scavenging, (b) ferric-reducing antioxidant power (FRAP) and (c) inhibition of copper-catalysed in vitro human low-density lipoprotein (LDL) oxidation. Scavenging activity correlated well (r = 0.73) with the corresponding total polyphenolic content measured by the Folin–Ciocalteu procedure and expressed as phloroglucinol equivalents (PGE). Of the seaweeds tested, Fucus showed the highest antioxidant activity in two of the test methods used (1 g (dry matter) had a DPPH· activity and a FRAP value equivalent to those 0.18 and 0.07 mmol of Trolox respectively) and the highest total polyphenolic content (41.4 gPGEkg−1 dry matter). The antioxidant activity and the content of phenolic compounds decreased with processing and storage in the seaweeds tested. In addition, Fucus showed good efficiency in the in vitro inhibition of LDL oxidation. © 2001 Society of Chemical Industry

Evidence for health benefits of plant phenols : local or systemic effects?

Abstract: Plant phenols are mostly products of the phenylpropanoid pathway and comprise a large variety of compounds: cinnamic acids, benzoic acids, flavonoids, proanthocyanidins, stilbenes, coumarins, lignans and lignins. They are strong antioxidants and might prevent oxidative damage to biomolecules such as DNA, lipids and proteins which play a role in chronic diseases such as cancer and cardiovascular disease. Plant phenols may interfere with all stages of the cancer process, potentially resulting in a reduction of cancer risk. Only flavonols have been investigated in observational studies. Five out of seven studies showed an inverse association of flavonol intake with subsequent cardiovascular disease (CVD). A protective effect against cancer was only found in one out of four studies. Thus the epidemiological evidence does not yet allow a firm decision on the involvement of flavonols in the aetiology of either CVD or cancer. The epidemiology of flavonols points to a systemic effect. The epidemiology of tea, as a rich source of various phenols, shows inconsistent data for colon cancer, which also does not support a local effect of plant phenols. The absorption and bioavailability of plant phenols have been inadequately studied. Dietary flavonoids were thought to be poorly absorbed because of their presence as β-glycosides (conjugates of sugars). However, conjugation with glucose enhanced human absorption. Flavonoids and other plant phenols are extensively metabolised by colonic bacteria: the ring structure is cleaved, giving a range of phenolic acids which are then absorbed. Human studies showed that only about 1% of a well-absorbed flavonoid was excreted with an intact flavonoid backbone into urine. Major questions to be answered are whether the effective concentrations found in in vitro systems really reflect physiological concentrations. Les phenols vegetaux sont principalement produits par la voie des phenylpropanoides: Il y a une grande variete de composants: les acides cinammique et benzoique, les flavonoides, proanthcyanidines, stilbenes, coumarines, lignanes et lignines. Ce sont des antioxydants, qui auraient des activites cardioprotectrices et anticarcinogenes. Toutefois, les donnees sur l'absorption et la biodisponibilite ne sont pas entierement connues. Il reste a savoir si les concentrations actives dans les systemes in vitro refletent vraiment celles existant dans les conditions physiologiques.

Diferulates as structural components in soluble and insoluble cereal dietary fibre

Abstract: Cell wall cross-linking can have a substantial effect on the properties of the wall. To estimate cross-linking (between arabinoxylans) in cereal fibres, dehydrodiferulate levels were measured in soluble and insoluble dietary fibre (SDF and IDF) isolated from whole grains of maize (Zea mays L), wheat (Triticum aestivum L), spelt (Triticum spelta L), rice (Oryza sativa L), wild rice (Zizania aquatica L), barley (Hordeum vulgare L), rye (Secale cereale L), oat (Avena sativa L) and millet (Panicum miliaceum L). After saponification of the cereal fibres the extracts were investigated for dehydrodimers of ferulic acid using GLC–MS and GLC–FID. From most cereal IDF the whole spectrum of dehydrodiferulic acids (DFAs) (8-5′-, 8-8′-, 5-5′-, 8-O-4′- and 4-O-5′-coupled) could be identified. The absolute contents of total DFAs ranged between 2.4 and 12.6 mg g−1. With the exception of 4-O-5′-coupled DFA, the whole range of DFAs was also detected from cereal SDF but only in amounts of 40–230 µg g−1. It was estimated that arabinoxylans of cereal IDF contain 8–39 times more diferulates than arabinoxylans of cereal SDF (where measurement of DFA levels in SDF was possible). In cereal IDF, 8-5′-coupled dimers dominated, whereas in cereal SDF, 8-8′-coupled dimers were relatively enhanced and often became the major dimers. © 2001 Society of Chemical Industry

HPLC flavonoid profiles as markers for the botanical origin of European unifloral honeys

Abstract: The HPLC phenolic profiles of 52 selected unifloral honey samples produced in Europe were analysed to detect possible markers for the floral origin of the different honeys. Lime-tree (five markers), chestnut (five markers), rapeseed (one marker), eucalyptus (six markers) and heather (three markers) honeys had specific markers with characteristic UV spectra. In addition, the flavanone hesperetin was confirmed as a marker for citrus honey, as well as kaempferol for rosemary honey and quercetin for sunflower honey. Abscisic acid, which had been reported to be a possible marker for heather honey, was also detected in rapeseed, lime-tree and acacia honeys. Ellagic acid in heather honey and the hydroxycinnamates caffeic, p-coumaric and ferulic acids in chestnut, sunflower, lavender and acacia honeys were also detected. The characteristic propolis-derived flavonoids pinocembrin, pinobanksin and chrysin were present in most samples in variable amounts.

Lycopene content differs among red‐fleshed watermelon cultivars

Abstract: Lycopene, a carotenoid, has antioxidant properties that may reduce the incidence of certain cancers. Watermelon (Citrullus lanatus (Thunb) Matsum & Nakai) is a natural source of lycopene, with a reported average content of 48.7 µg g−1 fresh weight based on samples taken from retail produce. This study demonstrated the variability of lycopene content in 11 red-fleshed watermelon cultivars grown at one location, representing seedless, open-pollinated and hybrid types, and in commercially shipped hybrid and seedless melons, representing seasonal production periods. Tristimulus colorimeter a* and chroma values were positively correlated with lycopene values, but linear or quadratic regressions of colorimeter data against lycopene values were not significant. Tristimulus colorimeter readings from cut melons were compared to amounts of lycopene extracted from the same melons. Lycopene content varied widely among cultivars, with four cultivars having mean values greater than 65.0 µg g−1 fresh weight. Seedless types sampled tended to have higher amounts of lycopene (>50.0 µg g−1 fresh weight) than seeded types. Watermelon lycopene content changed for some cultivars with production season. Published in 2001 for SCI by John Wiley & Sons, Ltd

Effect of irrigation on changes in the anthocyanin composition of the skin of cv Tempranillo (Vitis vinifera L) grape berries during ripening

Abstract: The impact of water availability on the yield and on the chemical composition in the skins of cv Tempranillo grapes at different phases of berry growth was studied over a 2 year period by determining changes in berry weight, °Brix, titratable acidity, pH and different phenolic compounds. The evolution of phenolic compounds during berry growth followed similar patterns to those reported by previous investigators. Over the 2 year study, concentrations of total phenols and total tannins in the skins were always higher for the non-irrigated than for the irrigated vines, though the differences were not significant on some sampling dates. Total anthocyanin concentrations in 1992 were significantly higher in the non-irrigated than in the irrigated grapes, except at veraison and harvest. In contrast, in 1993, concentrations were higher in the non-irrigated grapes on the first three sampling dates and in the irrigated grapes on the last three sampling dates, but with significant differences only on day 136 after budbreak. In the first year, anthocyanin concentrations for the non-irrigated grapes were higher than for the irrigated grapes, except at harvest, though the differences at harvest were not significant. However, in the second year, concentrations in the berries from the irrigated vines were significantly higher on most sampling dates. In both years, concentrations of the five anthocyanins at harvest were higher for the irrigated treatment, the treatment that produced higher berry weights and crop yields. © 2001 Society of Chemical Industry

Quantitative assessment of antioxidant properties of natural colorants and phytochemicals: carotenoids, flavonoids, phenols and indigoids. The role of beta-carotene in antioxidant functions

Abstract: Reactive oxygen species are potentially damaging molecules. An important function of antioxidants is to intercept harmful triplet states, in order to prevent the formation of singlet oxygen, or to quench singlet oxygen directly. However, antioxidants are also reactive towards other active oxygen species such as the hydroxyl radical, the superoxide anion and the non-excited oxygen ground state in the presence of radical initiators. It is well known that flavonoids and carotenoids show strong antioxidant properties. Polyenes and carotenoids are the best known among the compounds that quench singlet oxygen by efficient energy transfer. A large number of modified, synthetic analogues and derivatives have been synthesised to prepare even better quenchers than the natural carotenoids. Phenols are also excellent chain-breaking antioxidants. Recently, many indigoid dyes (including bacterial indigoids) were studied, with the remarkable result that most, but not all, members of this class of chromophores quench singlet oxygen at the diffusion limit and some of them are excellent radical traps. It has been shown in this study that a quantitative assessment of antioxidant properties of flavonoids, carotenoids, phenols and natural indigoids can be achieved using the following three assays: (1) oxygen pressure dependence; (2) peroxide formation; (3) singlet oxygen quenching. Reactivities towards both excited states and ground state radicals can be properly described by these assays. The remarkable role of β-carotene as an ‘unusual antioxidant’ (Burton GW and Ingold KU, Science224: 569–573 (1984)) in reactions using various oxygen pressures becomes clearer. The so-called ‘pro-oxidant effects’ concern primarily the antioxidant itself and its degradation, since no or very little damage to the substrate occurs in this type of experiment. Three main categories of antioxidants may be classified: (1) excellent antioxidants that perfectly quench excited states as well as ground state radicals (eg actinioerythrol, astaxanthin); (2) good antioxidants that strongly inhibit peroxide formation but are less efficient in quenching excited states (eg flavonols, tocopherols) or lead to considerable degradation of the antioxidant itself (eg β-carotene, lycopene); (3) moderate antioxidants that fail to excel in both reactivities (eg ζ-carotene, flavone). © 2001 Society of Chemical Industry

Intestinal structure and function of broiler chickens on diets supplemented with a mannan oligosaccharide.

Abstract: A study was conducted to evaluate the response of broiler chickens to a commercial synthetic mannan oligosaccharide, Bio-Mos™ (BM), included in sorghum/lupin-based diets at 0.0, 1.0, 3.0 or 5.0 g kg−1 diet. The diets were fed between 7 and 28 days of age, and both the gross response and mechanisms involved were evaluated. The highest level of BM in the diet resulted in longer (P < 0.01) jejunal villi than those observed at other levels of supplementation. The RNA content of the ileal mucosal homogenate was significantly greater (P < 0.05) in chicks raised on diets supplemented with 3.0 and 5.0 g BM kg−1 diet than in other groups. The protein/DNA ratio of the jejunal mucosal homogenate was also higher (P < 0.05) in chicks fed the 1.0 g BM kg−1 diet than in chicks fed the other diets. The protein/RNA and RNA/DNA ratios in ileal homogenates were significantly (P < 0.01) influenced by the presence of BM in the diet. There were significantly greater specific activities of maltase (P < 0.01), leucine aminopeptidase (P < 0.05) and alkaline phosphatase (P < 0.001) in the jejunum as a result of supplementation with BM. Digestive enzyme activities in the ileum were unaffected. L-Tryptophan uptake by jejunal brush-border membrane vesicles was significantly higher (P < 0.01) in chicks raised on the 5.0 g BM kg−1 diet than in the other chicks. The supplement led to minor improvement in body weight but no improvement in feed conversion ratio. These effects were related to changes in digestive enzyme activities and, perhaps, amino acid transport. © 2001 Society of Chemical Industry

Physicochemical properties and application of pullulan edible films and coatings in fruit preservation

Abstract: The effects of water, sorbitol and a sucrose fatty acid ester (SE) on the water sorption behaviour and thermal and mechanical properties of pullulan-based edible films as well as the physiological responses of fruit coated with pullulan have been studied. Incorporation of sorbitol or SE in pullulan films resulted in lower equilibrium moisture contents at low to intermediate water activities (aw), but much higher moisture contents at aw > 0.75; estimates of monolayer values (within 4.1–5.9 gH2O kg−1 solids) were given by application of the Brunauer–Emmett–Teller (BET) and Guggenheim–Anderson–DeBoer (GAB) models. A single glass–rubber transition (Tg), attributed to the polysaccharide component, was detected by calorimetry and dynamic mechanical thermal analysis (DMTA) at a sorbitol level of 15–30% DM. With both tests the strong plasticising action of water and polyol was evident in the thermal curves, and the Tg vs moisture content data were successfully fitted to the Gordon–Taylor empirical model. Multifrequency DMTA measurements provided estimates for the apparent activation energy of the glass transition in the range of ˜ 300–488 kJ mol−1. With large-deformation mechanical testing, large decreases in Young's moduli (tensile and three-point bend tests) were observed as a result of water- and/or polyol-mediated glass-to-rubber transition of the polymeric films. In the moisture content range of 2–8%, increases in flexural modulus (E) and maximum stress (σmax) with small increases in moisture content were found for films made of pullulan or pullulan mixed with 15% DM sorbitol; a strong softening effect was observed when the water content exceeded this range. Addition of sorbitol increased the water vapour transmission rate of the films, whereas addition of SE had the opposite effect. Application of a pullulan/sorbitol/SE coating on strawberries resulted in large changes in internal fruit atmosphere composition which were beneficial for extending the shelf-life of this fruit; the coated fruit showed much higher levels of CO2, a large reduction in internal O2, better firmness and colour retention and a reduced rate of weight loss. In contrast, similar studies on whole kiwifruits showed increased levels of internal ethylene, which caused acceleration of fruit ripening during storage. © 2001 Society of Chemical Industry

Effect of chitosan on incidence of brown rot, quality and physiological attributes of postharvest peach fruit

Abstract: The effect of chitosan (5.0 and 10.0 mg ml −1) on the incidence of brown rot (caused by Monilinia fructicola), quality attributes and senescence physiology of peaches was investigated. It was found that both concentrations of chitosan reduced the incidence of brown rot significantly and delayed the development of disease compared with the control, but were less effective than the fungicide prochloraz. Chitosan-treated peaches were firmer and had higher titratable acidity and vitamin C content than prochloraz-treated or control peaches. Compared to control (water-treated) peaches, chitosan-treated peaches showed lower respiration rate, less ethylene and malondialdehyde (MDA) production, higher superoxide dismutase (SOD) activity and better membrane integrity. Hence it can be concluded that chitosan has the potential to control brown rot, preserve valuable attributes and prolong the shelf life of postharvest peaches, presumably because of its antifungal property and inhibition of the ripening and senescence process of postharvest peaches. © 2000 Society of Chemical Industry

Minerals, phytic acid, tannin and rutin in buckwheat seed milling fractions

Abstract: The composition of common buckwheat (Fagopyrum esculentum Moench) seed milling fractions depends upon the relative abundance of various seed tissues in each. Fancy (light) flour contains mainly central endosperm, while the bran milling fraction has seed coat and some embryo tissues. Phytate, found in protein bodies of embryo and aleurone cells, is the major storage form of phosphorus, potassium, magnesium and some microelements in seeds. Phytic acid (35-38 g kg(-1)) and minerals are concentrated in bran, a milling fraction with high concentrations of phytate-rich tissues. Polyphenolics, including condensed tannins (proanthocyanidins), are also concentrated in bran (11-15 g kg(-1)). Rutin is concentrated in the hull of common buckwheat (0.8-4.4 g kg(-1)). Rutin concentration is low (0.2-0.3 g kg(-1)) in groats of common buckwheat but higher (0.7-0.8 g kg(-1)) in bran containing hull fragments. Rutin is 300-fold more concentrated (81 g kg(-1)) in groats of tartary buckwheat (Fagopyrum tataricum (L) Gaertn) than in groats of common buckwheat. Only small amounts of quercetin were detected. Bran is a concentrated source of phytic acid and tannins, a consideration in consumption of large amounts of buckwheat bran for nutritional or medicinal purposes. (C) 2001 Society of Chemical Industry.

Post‐harvest increase of indolyl glucosinolates in response to chopping and storage of Brassica vegetables

Abstract: Brassica vegetables contain high amounts of glucosinolates, which contribute to the beneficial health effects of their consumption. Processing of such vegetables in domestic food preparation or industrial processing will influence levels of glucosinolates considerably and thus affect their health-protective capacity. This study demonstrates the effects of chopping of raw Brassica vegetables on their glucosinolate composition. Limited breakdown of aliphatic glucosinolates in cabbage was found, whereas unexpected increased levels of indolyl glucosinolates were detected after chopping and storage of cabbage and broccoli under ambient conditions. In chopped white cabbage a 15-fold increase of 4-methoxy- and l-methoxy-3-indolylmethyl glucosinolates was noted after 48h of storage. Chopping and storage of broccoli resulted in a strong reduction of most glucosinolates, except for 4-hydroxy- and 4-methoxy-3-indolylmethyl glucosinolates, which increased 3.5- and 2-fold respectively. The myrosinase-mediated hydrolysis of glucosinolates appears to be counteracted by a post-harvest increase of some indolyl glucosinolates. In this paper we propose a mechanism of stress-induced increase of glucosinolates, which plays an important role besides the well-known breakdown mechanism. L'effet du tranchage sur la composition des choux crus en glucosinolates est etudie. Les taux de glucosinolates d'indole augmentent apres entreposage et tranchage dans le chou et le brocoli. Les glucosinolates totaux dans le chou coupe proviennent probablement de la degradation par la myrosinase d'une part et de la formation des indoles induite par le stress, d'autres part.

Cichorium intybus L – cultivation, processing, utility, value addition and biotechnology, with an emphasis on current status and future prospects

Abstract: Cultivation of chicory plants for various applications, such as utilisation of the root biomass for preparation of a coffee adjuvant, utilisation as a vegetable and, recently, utility of the plants for important phytochemicals, has received global attention. Chicory is widely grown in countries of different geographical locations owing to the economic importance of this crop. This review addresses cultivation, utility, phytochemical studies and pharmacological aspects, with an emphasis on biotechnological developments in recent years and safety evaluation of genetically modified chicory crops. These aspects are dealt with in detail to bring out the current status and future prospects of cultivation and utility of this economically important crop.

Structural and chemical changes in cocoa (Theobroma cacao L) during fermentation, drying and roasting

Abstract: Cocoa seeds and pulp were fermented for 144 h, followed by natural drying. The tegument was removed and the cotyledons were broken into nibs which were roasted at 150 °C for 30 min. Non-fermented material, material fermented for 24, 48 and 72 h, material fermented for 144 h and then dried, and also the roasted nibs, were all prepared for chemical and microscopic analyses. Light microscopy revealed the presence of anionic and cationic residues and of neutral sugars. During fermentation there was a reduction in the cytoplasmic content of phenolic compounds and in the number of protein bodies. The cell wall showed a reduction in anionic residues and a loss of crystallinity. These alterations were maximum after 72 h. Drying and roasting increased the number of damaged cells and reduced the amount of cytoplasmic material. The chemical analyses generally confirmed the microscopy results. The concentration of amino-terminal groups and total free amino acids increased during fermentation (up to 72 h), but returned to the initial values after roasting. The principal chemical changes were related to reducing sugars, free amino acids, proteins and phenols, and PCA was suggested as a useful tool to compare different samples. Microscopic analysis revealed the degradation of protein and phenolic bodies and cellular damage during roasting. © 2000 Society of Chemical Industry

Polypeptide profile and functional properties of defatted meals and protein isolates of canola seeds

Abstract: Laboratory-defatted meals from four types of canola seeds were analysed for protein profile by reducing and non-reducing forms of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). In the absence of a reducing agent (2-mercaptoethanol), four major polypeptide bands (16, 18, 30 and 53 kDa) were prominent in similar ratios in all varieties. In the presence of mercaptoethanol, significant reductions in intensity of the major bands occurred, suggesting that the major polypeptides contained smaller units which were held together by disulphide bonds. Meals from Brassica napus seeds had higher protein solubilities than meals from Brassica rapa seeds. Meals with higher protein solubility values also had higher foaming capacity (FC) values. Generally, the acid-precipitated (pH 4.0) protein isolates (APPIs) had higher FC values than the calcium-precipitated isolates (CPPIs). On the other hand, the CPPIs formed emulsions with higher values of emulsifying activity index (EAI) when compared to the APPIs. The results indicate that variations in functional properties of protein isolates and meals between the four seed types were probably due to differences in protein conformation in aqueous solutions rather than differences in polypeptide composition. © 2001 Society of Chemical Industry

Correlation between antiradical activity and stability of betanine from Beta vulgaris L roots under different pH, temperature and light conditions

Abstract: When the antiradical activity and stability of betanine were studied at pH values of 3.5 and 8.5 and temperatures of 25, 50 and 75 °C, the results showed that the antiradical activity was greater at acidic pH and lower at higher temperatures. At basic pH the activity of betanine correlated well with its stability at the three temperatures assayed, suggesting that the degradation products, betalamic acid (BA) and cyclo DOPA 5-O-β-D-glucoside (CDG), did not contribute to this activity under the experimental conditions used. However, at acidic pH the degradation product, CDG, did seem to contribute to the antiradical activity. Furthermore, at pH 3.5, betanine stability was so great that light conditions had no effect on the antiradical activity. At basic pH, too, light had no effect on betanine activity owing to the high instability of the pigment. © 2001 Society of Chemical Industry

Thermal isomerisation susceptibility of carotenoids in different tomato varieties

Abstract: The susceptibility of predominant tomato carotenoids to thermal isomerisation during typical food preparation is reported for five varieties with distinctively different carotenoid distribution. The tomato varieties used contain distinct amounts of the following predominant carotenoids: all-trans lycopene, all-trans β-carotene, all-trans δ-carotene, all-trans lutein and the poly-cis geometrical isomer of lycopene, prolycopene. The tomatoes were subjected to thermal treatments and unit operations similar to those during food preparation: boiling, addition of vegetable cooking oil, chopping and agitation. The results indicated that, during typical cooking of tomatoes, common factors such as genotypic differences in overall carotenoid composition, the presence of oil and physical changes to tomato tissues did not result in the thermal isomerisation of all-trans lycopene, all-trans δ-carotene, all-trans γ-carotene or prolycopene. Significant amounts of all-trans β-carotene and all-trans lutein, however, were converted to the cis configurations. The presence of vegetable cooking oil did not alter the thermal stability of any carotenoids being evaluated. Examination of samples by electron microscopy indicated that heat treatment imparted changes to the physical ultrastructure of the tomato tissue, such as cell wall and organelle deformation. The observed differences in these carotenoids' relative susceptibility to thermally induced isomerisation reactions might be attributable to their differences in physical state and cellular localisation. Thus, while thermal processing reportedly alters the bioavailability of carotenoids, its effect on the geometrical isomer distribution is selective and limited. These findings are important considerations in our overall effort to gain a better understanding of carotenoid metabolism in vivo and of the physical chemistry of lycopene in vitro. La sensibilite a l'isomerisation thermique des carotenoides de tomate durant la preparation alimentaire est reportee pour 5 varietes de tomates contenant une distribution differente du pigment:all-trans-lycopene, all-trans β-carotene, all-trans δ-carotene, all-trans luteine, prolycopene. Les tomates ont ete soumises a un traitement thermique. Une fraction de all-trans β-carotene et all-trans luteine est convertie en isomere cis, mais pour les autres carotenoides, il n'y a pas d'effet d'isomerisation, meme en presence d'huile vegetale.

Lutein in patients with cataracts and age-related macular degeneration : a long-term supplementation study

Abstract: Lutein, a non-provitamin A xanthophyll, is widely distributed in fruits and vegetables frequently consumed. In human serum, lutein is transported by lipoproteins and selectively accumulated in certain tissues (eg the retina). Epidemiological studies suggest that high intake and serum levels of lutein are associated with a lower risk of cataracts and age-related maculopathy. Subjects diagnosed with cataracts (CA; n =5) or age-related macular degeneration (ARMD; n =5) agreed to take three lutein capsules per week. Each capsule potentially provided about 12 mg of all-trans-lutein, 3 mg of 13/15-cis-lutein and 3.3mg of α-tocopherol, as revealed by HPLC. Zeaxanthin was not detected. Average supplementation time was 13 months (range 4-20 months) for ARMD subjects and 26 months (range 16-36 months) for CA subjects. Blood samples for carotenoid analysis were collected every 3 months, coinciding with ophthalmological revision. In serum, concentrations of lutein, 13-cis-lutein and two ketocarotenoids increased significantly. Maximum increments were observed at 3-6 months, reaching levels above the 95th percentile of the reference population (>0.44 μmol l -1 ). Ophthalmological evaluation showed an average increment in visual acuity of 0.4, and glare sensitivity also improved. No significant side effects such as hypercarotenemia, carotenodermia or changes in biochemical or haematological profile were observed. Thus, lutein supplementation at achievable dietary levels increased and maintained serum lutein levels, which were associated with an improvement in the visual function of the patients. Des etudes epidemiologiques suggerent que la supplementation en luteine et des taux seriques eleves sont associes a des risques de cataractes et de degenerescences maculaires plus faibles. Des sujets atteints ont ete supplementes par voie orale, a raison de 3 prises par semaine. Chaque prise contient 12mg de luteine all-trans, 3 mg de 13/15-cis- luteine, et 3,3 mg d'α-tocopherol, pas de zeaxanthine. La duree du traitement etant de 13 mois en moyenne pour la cataracte et de 26 mois pour la degenerescence maculaire. Le dosage des carotenoides sanguins a ete effectue tous les 3 mois en meme temps que les controles ophtamologiques.Aucun effet secondaire n'a ete note, et les fonctions visuelles des patients sont ameliorees.

Antioxidative and antimutagenic activities and polyphenol content of pesticide-free and organically cultivated green vegetables using water-soluble chitosan as a soil modifier and leaf surface spray

Abstract: Five green vegetables (qing-gen-cai, Chinese Cabbage, spinach, Welsh onion and green pepper) commonly used in our daily diet were analysed to determine their antioxidative and antimutagenic activities and chemical content of polyphenols. We obtained pesticide-free and organically cultivated (O) vegetables using water-soluble chitosan as a soil modifier and leaf surface spray (as an alternative natural insecticide) in order to investigate biofunctions induced or enhanced by such specialised cultivation practices. In addition, we purchased the same varieties of vegetables cultivated on an adjacent farm in the conventional manner (C) using pesticides and chemical fertilisers in order to examine the differences in biological activities and distribution of constituents responsible for such activities. The antioxidative activity shown by O vegetables was 120% times higher than that shown by C vegetables in the case of spinach and 20–50% higher in the case of Welsh onion, Chinese cabbage and qing-gen-cai. In comparison with C vegetables, the antimutagenic activity shown by O vegetables was higher against 4-nitroquinoline oxide (4NQO) in qing-gen-cai, Chinese cabbage and Welsh onion, against benzo[a]pyrene (BaP) in all five vegetables, against 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in qing-gen-cai, Chinese cabbage and green pepper and against 3-amino-1-methyl-5H-pyrido[4,3-b]indole acetate (Trp-P-2) in spinach only. Among all green vegetable juices tested for flavonoid composition, quercitrin, caffeic acid and baicalein in O vegetables were detected in concentrations 1.3–10.4 times higher than those found in C vegetables, suggesting the influence of different cultivation practices. © 2001 Society of Chemical Industry

Starch properties as affected by sorghum grain chemistry

Abstract: To determine the relationship between sorghum grain polyphenol content, grain structure, and starch properties, starch was isolated from 10 sorghum varieties using an alkali steep and wet-milling procedure. SV2, a tannin-free variety with white pericarp, gave a white starch. Varieties having red or white pericarp and higher polyphenol levels gave pink starches. Hunter colour values (L, a, b) of starches were not correlated with grain polyphenol content. Grain appearance in terms of pericarp colour, or presence or absence of pigmented testa, did not relate to the intense pink colouration of sorghum starches. Starch amylose content was significantly negatively correlated (r = −0.88, p < 0.001) to grain floury endosperm texture. Sorghum starches had higher peak viscosity (PV) in pasting than commercial maize starch. The time taken to reach peak viscosity from the initial viscosity rise was less for sorghum starches than maize starch. However, sorghum starches had a higher rate of shear thinning (Rst) than maize starch. There was a significant positive correlation between grain polyphenol content and starch PV (r = 0.75, p < 0.05). Starch gel hardness was negatively correlated to pasting properties of Rst and paste breakdown (r = −0.78 and −0.77 respectively) at p < 0.01. Peak gelatinisation temperature (Tp) occurred over a narrow range from 66 to 69 °C. Tp was negatively correlated to the floury endosperm portion of the grain (r = −0.77) at p < 0.01. It is concluded that sorghum grain polyphenol content and grain characteristics influence its starch properties. © 2000 Society of Chemical Industry

Pigments in Greek virgin olive oils: occurrence and levels

Abstract: Fifty-two samples of virgin olive oil from various regions of Greece were examined for the presence and levels of chlorophyll and carotenoid pigments using normal phase liquid chromatography and spectrometry. Pheophytin α (Pheo α) was the main pigment in all the oils examined (>10 mg kg−1 in more than 70% of samples). Two pheophytin α derivatives (peaks A and B), eluted close to Pheo α, may potentially be used to examine handling conditions and length of storage of oil until analysis. Analysis of 25 Greek commercial oils obtained from retail stores verified the above observations. Chlorophyll α may be present in a virgin olive oil just after production. Its absence should not be exclusively attributed to cultivar characteristics or extraction conditions, since pheophytinisation occurs rapidly. Lutein content varied between 0.2 and 3.9 mg kg−1 and β-carotene content from 0.4 to 5.1 mg kg−1. The lutein/β-carotene ratio was characteristic (<1) for samples from Koroneiki, the major Greek cultivar for oil production. The total Pheo α (Pheo α + peak A + peak B)/total carotenoid (lutein + β-carotene) ratio ranged between 2 and 11 owing to prevailing green hues. This ratio may be used as an indicator of oil typicality along with other analytical parameters. © 2001 Society of Chemical Industry

Why do we like what we like

Abstract: Why do we find certain foods more pleasurable than others? Interactions of food components with human biology and with social and eating contexts give rise, in some predictable ways, to relatively stable individual food likes. While sensory and consumer research have traditionally focused on measuring existing likes, a better understanding of their basic determinants can provide ideas and tools to better predict and influence how likes may develop and change. The liking for a particular food or set of foods largely reflects the prevailing cultural environment and personal experiences, which generate variation in the opportunities and likelihood for specific biological predispositions and learning processes to operate with regard to particular foods. These learning processes may be largely influenced by the intrinsic orosensory or nutritional attributes of foods themselves, as well as characteristics of the situational contexts in which foods are experienced. Liking is one factor contributing to the desire to eat a food, and ultimately to food selection. Current knowledge of these processes is briefly reviewed, with suggestions of potential implications for understanding and predicting food acceptance and choice. © 2000 Society of Chemical Industry

Amylolysis of maize mutant starches

Abstract: Starches from single and double maize mutants were subjected to enzymatic degradation by porcine pancreatic α-amylase. The maize mutants covered a broad range of macromolecular composition and crystalline structure relative to fractional crystallinity level (from 0.19 to 0.48) and polymorphic type (with various proportions of A-, B- and V-type allomorphs). Regardless of amylose content or crystallinity level, starches with a predominant B-crystalline type were more resistant to amylolysis than others, and initial rates of hydrolysis were lower for B-type than A-type starches. Final hydrolysis extents were less than 35% for predominant B-type starches, 60% for C-type ones and more than 70% for predominant A- or V-type ones. Dangling chains or crystal defects also appeared to increase initial hydrolysis rates, although lower initial rates and final hydrolysis extents were mainly related to the amount of B-type crystallites. Unexpectedly, hydrolysis residues were composed of both amorphous and B-type crystalline regions. These observations suggest that resistance to amylolysis is related to the distribution of B-type crystallites within the granule rather than to the relative proportion of B-type crystallites. Des amidons provenant de mais mutant (simple ou double) sont soumis a une degradation enzymtique par l'α-amylase pancreatique porcine. Les amidons sont de composition et de structure cristalline variables. Les amidons de type B sont plus resistants a l'amylolyse que les autres. Les vitesses initiales d'amylolyse varient en fonction des branchements et des defauts cristallins de l'amidon. La resistance a l'amylolyse est liee a la distribution des cristallites de type B a l'interieur des granules plutot qu'a la proportion des cristallites de type B.

Gas chromatographic analysis of alkylresorcinols in rye (Secale cereale L) grains

Abstract: A method was established for fast and easy analysis of 5-n-alkylresorcinols in rye grains, considering effects of milling (intact grains versus flour), extraction solvent (ethyl acetate, methanol and acetone), extraction volume per gram of sample (20 and 40 ml) and extraction time (3, 6, 18 and 24h). For intact kernels, extraction of 1 g samples with ethyl acetate (40 ml, 24h) is recommended. The ease of extraction is consistent with the presence of alkylresorcinols in the outer layers of the kernel and their absence in the endosperm. The extracts were analysed (without further purification or derivatisation) by gas chromatography using methyl behenate (C22:0, fatty acid methyl ester) as internal standard. Alkylresorcinols were identified by gas chromatography/mass spectrometry, and the major homologues were found to contain alkyl chains of C17:0, C19:0, C21:0, C23:0 and C25:0. The methodology was then applied to analyse the alkylresorcinol content in 15 rye cultivars grown at two locations in Sweden. Total alkylresorcinol contents varied within the range 549-1022 μg g -1 , and the average percentages of the different alkylresorcinols were: 17:0, 23%; 19:0, 32%; 21:0, 26%; 23:0, 11%; and 25:0, 8%. Une methode d'analyse rapide des 5-n-alkylresorcinols du grain de seigle est presentee. Elle est utilisee pour etudier les effet de la mouture, du solvant d'extraction, de la taille de l'echantillon et du temps d'extraction sur la composition. Pour les grains intacts, l'extraction a partir d'un echantillon d'un gramme avec de l'acetate d'ethyle est recommandee. L'extrait est analyse par chromatographie en phase gazeuse. Les chaines carbonees retrouvees majoritairement sont les C17:0, C19:0, C21:0, C23:0 et C25:0. L'analyse de 15 cultivars suedois donne une teneur en alkylresorcinol variant de 549 a 1022 μg/g.

Content of bioactive compounds in pungent spice red pepper (paprika) as affected by ripening and genotype

Abstract: This work was conducted to investigate changes in the bioactive nutrient content of hot (pungent) paprika as a function of ripening in four of the most important varieties cultivated in Hungary. For the quantitative determination, recent liquid chromatographic (HPLC) methods were applied. Forty carotenoids were separated, with β-carotene and lutein of interest from the biological point of view. The major component of vitamin E was α-tocopherol. Capsaicin, dihydrocapsaicin and nordihydrocapsaicin were the dominant pungency principles. As for vitamin C components, only ascorbic acid could be detected and determined. The results indicated that all the examined compounds were at low level in the mature green fruits, and the onset of climacteric ripening caused their content to grow. In accord with the advance in ripening, carotenoids were being formed even at the overripening stage, while tocopherols, capsaicinoids and ascorbic acid reached their maximum level at the colour break or red stage and then declined. The highest values with regard to carotenoids were estimated in SZ-178 and F0-3 cultivars. The best retention of ascorbic acid was found in SZ-178, which contained 4.86 mg g−1 dry matter in the dry pods. On the other hand, retention of α-tocopherol during ripening and natural drying was found to depend on variety. The highest value for vitamin E was recorded in SZ-178 followed by K-V2, which contained the highest level of α-tocopherol at the red stage of ripening. © 2001 Society of Chemical Industry

Effect of heating temperature, pH, concentration and starch/whey protein ratio on the viscoelastic properties of corn starch/whey protein mixed gels

Abstract: The viscoelastic properties of corn starch (CS) gels were more dependent on heating temperature, while the properties of whey protein isolate (WPI) gels were more dependent on pH. Thus heating temperature (75, 85, 95 °C) and pH (5, 7, 9) were varied to obtain a series of mixed gels with interesting viscoelastic properties. WPI gels showed extensive stress relaxation (SR) indicative of a highly transient network structure, while CS gels relaxed very little in 2000 s. Based on SR results, it appeared that CS/WPI mixed gels with 25 and 50% CS formed compatible network structures at 15% total solids only at pH 9. This supposition was supported by SEM microstructures obtained for dehydrated gels and a synergistic increase in the large-strain fracture stress for these gels. Some synergy was also found for mixed gels at 30% total solids at pH 9, while at pH 7 the mixed gels seemed to contain separate additive WPI and CS networks unlike the case for pH 7 at 15% total solids. In both cases (15 and 30% total solids) the degree of elasticity of the mixed gels decreased as the WPI content increased. Mixed gels (CS:WPI = 0.5) at pH 9 showed increased fracture stress and fracture strain relative to the same gels at pH 7. This suggests that a unique chemical compatibility exists at pH 9 and results in gels that combine the elasticity of CS and the internal stress dissipation of WPI. © 2001 Society of Chemical Industry

Cranberry proanthocyanidins associate with low-density lipoprotein and inhibit in vitro Cu2+-induced oxidation†

Abstract: Antioxidant activity of six fractions of cranberry phenolic compounds was determined by inhibition of Cu 2+ -induced low-density lipoprotein (LDL) oxidation. The phenolic composition of each fraction was determined by high-performance liquid chromatography. The phenolic fractions were mixed with aliquots of modified human serum prior to LDL isolation. The serum was modified to remove very-low-density lipoprotein and chylomicrons that may bind phenolic compounds. Only fractions 5 and 6 that contained proanthocyanidins (PAs) significantly increased the lag time of LDL oxidation, and the lag time for fraction 6 was significantly higher than for fraction 5. The mass distribution of PAs in these fractions was obtained by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, a technique that allows rapid characterisation of the molecular weight distribution in mixtures of oligomeric compounds. Fraction 5 contained trimers through heptamers, whereas fraction 6 contained pentamers through nonamers. In addition, fraction 6 contained PA oligomers with more doubly linked, A-type interflavan bonds. Results indicate that PAs specifically associate with LDL in modified serum and increase the lag time of Cu 2+ -induced oxidation. Differences between fractions 5 and 6 in PA structure and effects on LDL oxidation suggest that the degree of polymerisation and the nature of the interflavan bond influence antioxidant properties. Les activite antioxydantes de 6 fractions phenoliques de canneberge sont determinees in vitro par inhibition de l'oxydation des liporoteines LDL induite par le cuivre. Les fractions contenant la proanthocyanidine ralentissent l'oxydation des LDL. Le degre de polymerisation influence les proprietes antioxydantes des proanthocyanidines.