Showing report on Seeds
Nuts in the botanical sense are produced by some families of the order Fagales. These families are the Juglandaceae (walnut and pecan nut), the Fagaceae (chestnut), and the Betulaceae (hazelnut). In the culinary sense, the term nut is applied to a wider variety of dried seeds and fruits and to any large, oily kernel found within a shell. These nuts belong to the Fabaceae (peanut), the Rosaceae (almond) and the Anacardiaceae (pistachio) families. Other nuts found in the composition table are Brazil nut, cashew nut, macadamia nut and pines.
The highest total polyphenol contents (Folin assay) are found in chestnut (2.8 g/100 g), walnut (1.6 g/100 g), pecan nut (1.3 g/100 g), pistachio (867 mg/100 g), peanut (420 mg/100 g), hazelnut (291 mg/100 g) and almond (192 mg/100 g). Proanthocyanidins have been estimated by the direct phase HPLC in some of these nuts: hazelnut (491 mg/100 g), pecan nut (477 mg/100 g), pistachio (226 mg/100 g) and almond (176 mg/100 g). Lower contents were reported for walnut (60 mg/100 g), roasted peanut (10.6 mg/100 g) and cashew nut (2.0 mg/100 g). Catechins commonly associated to proanthocyanidins are also present. (+)-Catechin and (-)-epigallocatechin were detected in pecan (7.2 and 5.6 mg/100 g), pistachio (3.5 and 2.1 mg/100 g), hazelnut (1.2 and 2.8 mg/100 g) and almond (1.3 and 2.6 mg/100 g). (-)-Epicatechin and (-)-epicatechin 3-O-gallate were detected in cashew nut (0.9 and 0.2 mg/100 g). Catechins were not detected in brazil nut, macadamia nut, peanut, pine and walnut (305).
Ellagitannins and ellagic acid are the main polyphenols in walnut. High quantities of ellagic acid and valoneic acid dilactone are quantified after acid hydrolysis of ellagitannins, respectively 252 and 197 g/100 g in common walnut (Juglans regia) and 146 and 90 mg/100 g in Japanese walnut (Juglans ailanthifolia). Walnut moreover contains pedunculagin (306, 307, 308). High quantities of ellagic acid and gallic acid are also detected in chestnut (respectively 735.44 mg/100 g and 479.78 mg/100 g).
Juglone, as a characteristic walnut compound, is quantified in dehulled walnut (11.75 mg/100 g).
Pulses are edible legumes harvested for their dry seeds. They all belong to the Fabaceae family. Bean is the name for the common bean (Phaseolus vulgaris L.) and for other related large plant seeds species such as broad bean (Vicia faba L.), adzuki bean (Vigna angularis), lima bean (Vigna lunatus), mung bean (Vigna radiata) or climbing bean (Vigna umbellata). The common beans in the composition table are separated in ‘black’, ‘white’, and ‘other’ beans. This last category regroups several cultivars with color variability from cream to brown. Lentil (Lens culinaris) is a brushy annual plant grown for its lens-shaped seeds. Pea is the small edible round green bean which grows in a pod on the vine Pisum sativum. Other seeds from other species, most of them, round, are also called peas: pigeon pea (Cajanus cajan L.), chickpea (Cicer arietinum L.) and cowpea (Vigna unguiculata spp.).
Polyphenols in pulses are principally concentrated in the seed coat (309). The seed coat contains proanthocyanidins, flavonols, flavanones and hydroxycinnamic acids. Black seed coats also contain anthocyanins. Cotyledons mainly contain hydroxycinnamic acids. However, most studies only give content values for total polyphenols (Folin assay) or total proanthocyanidins (Vanillin assay). High total polyphenol contents (Folin assay) have been determined in adzuki bean and lentil (respectively 8.9 and 6.5 g/100 g in whole seeds) and lower contents in broad bean and dried pea (respectively 33 and 16 mg/100 g in dehulled seeds). The values determined for common bean are intermediate, from 47 mg/100 g in dehulled white bean to 1.6 g/100 g in whole black bean. Proanthocyanidin contents varying between 144 and 1875 mg/100 g have been reported for various beans (310, 311, 312, 313, 314, 315, 316). However, these values were essentially determined by spectrophotomectric methods. They are not reported in the composition table due to poor standardization of these methods, which cannot be used to compare proanthocyanidin contents in different plant species (317).
Only limited data is available for individual phenolic compounds. The main flavan-3-ol monomers found in pulses are (+)-catechin, (-)-epicatechin, (-)-epigallocatechin and (+)-gallocatechin. Low quantities are found in beans, lentils, and broad bean. (+)-Catechin 3-O-glucose was quantified in lentil.
The main flavonols in bean are kaempferol 3-O-glucoside or astragalin (respectively 6.6 mg/100, 31 mg/100 g and 40 mg/100 g in black bean, white bean and other beans), and lower amounts of kaempferol 3-O-acetyl-glucoside (respectively 3.4 mg/100, 7.1 mg/100 g and 16.4 in black bean, white bean and other beans) and kaempferol 3-O-xylosyl-glucoside (not detected in black bean, 11 mg/100 g in white bean, 11.5 in other beans). Lentil contains quercetin and myricetin glycosides with principally myricetin 3-O-rhamnoside (0.58 mg/100 g) and quercetin 3-O-rutinoside (0.52 mg/100 g). Lentils additionally contain flavone glycosides with principally apigenin 7-O-apiosyl-glucoside (0.62 mg/100 g).
Anthocyanidins are largely glycosylated. Delphinidin 3-O-glucoside (14 mg/100 g) and pelargonidin 3-O-glucoside (13 mg/100 g) are the main anthocyanins quantified in whole black bean. Several other anthocyanin glucosides have been characterised in red and black beans (318, 319, 320), but no suitable data were available for insertion in the composition table. In black lentil, the major anthocyanin is delphinidin 3-O-(2-O-beta-D-glucopyranosyl-alpha-L-arabinopyranoside) (321). In black cowpea they are delphinidin, cyanidin, petunidin and malvidin 3-O-glucosides (322).
Several hydroxycinnamic (ferulic, sinapic, p-coumaric, caffeic) and hydroxybenzoic acids (4-hydroxybenzoic, vanillic, syringic) are present in pulses in free or bound forms.
Quantitative and qualitative polyphenol profiles in pulses are affected by processing. Polyphenol contents are reduced by soaking/dehulling and during cooking (323, 324, 325, 326). Soaking and dehulling of beans reduced the polyphenol contents (309, 326). During bean cooking, the polyphenol content (Folin assay) was reduced by 90% in seed coat (327), while proanthocyanidins were reduced by 70% (328). In lentils, 29% proanthocyanidins were removed during soaking in water at 30°C during 3 hrs, and the same amount at 100°C during 30 min. Tannin contents were further reduced during cooking (329). In pigeon pea, total polyphenol was reduced by 4-26% after processing and cooking (324).
Germinated legumes are widely consumed around the word. Germination and fermentation have been proposed to improve the nutritive value of legumes (330, 331). During germination, the global level in total polyphenols tends to decrease (323, 324, 325, 326, 330, 331, 332, 333). However, isoflavones which are not detected (or only detected at traces) in raw or cooked seeds, are present in higher amounts in germinated beans (332) or peas (333). In lentil, important structural changes in procyanidin-type compounds were observed during germination (330). Fermentation led to a general increase in the content of several phenolic compounds (330).
Polyphenol content is also affected by storage. After 2 years of storage, the concentration of proanthocyanidins in seed coat was decreased 6 times and that of anthocyanins 4 times (328). HTC (hard to cook) is a textural defect that affects legumes stored under adverse conditions (e.g. tropical conditions). Storage-induced HTC beans contained lower levels of total polyphenols (Prussian blue assay) than the fresh beans, but higher levels of tannins (315). In HTC, the free phenolic acids increased, while the esters, which represented the highest content of phenolic acids in the control samples, decreased (334).
Flax (Linum usitatissimum L.) is a member of the Linaceae family. Flax seeds, also called flaxseed or linseed (linseed also designates the plant), are mainly produced in Canada, the USA and China. Flaxseeds come in two basic types, brown and yellow-golden, with most varieties having similar nutritional values. Flaxseeds can be dried and cold-pressed to produce a vegetable oil known as flaxseed or linseed oil, a yellowish oil used as a nutritional supplement. Grinding of whole flaxseeds breaks their outer skin, and produces a light-coloured powder. Whole flaxseeds are nowadays often added to multi-cereal breads, cereals and baking goods. Flaxseed gum has been used as a food additive for its thickening, emulsifying and gelling properties.
Flaxseed is currently known as the food source the richest in lignans. Lignans account for about 1% of flaxseed meal. Secoisolariciresinol is the major lignan in flaxseed, with contents of 840 mg/100 g in flaxseed meal. Two secoisolariciresinoldiglucoside diastereomers were identified, namely [2R,2′R]-2,3-bis[(4-hydroxy-3-methoxyphenyl)-methyl]-1,4-butanediyl-bis-β-glucopyranoside, and the minor [2R,2′S]-2,3-bis[(4-hydroxy-3-methoxyphenyl)methyl]-1,4-butanediyl-bis-β-glucopyranoside(335). Secoisolariciresinoldiglucoside is esterified to 3-hydroxy-3-methylglutaric acid (HMGA) (336), which can itself also be linked to the flavonol herbacetin diglucoside (HDG). At the same time, the ferulic acid 4-O-glucoside and p-coumaric 4-O-glucoside can be ester-linked to SDG, forming all together complex macromolecules (337, 338, 339, 340). Other lignans present in flaxseed are matairesinol, ,secoisolariciresinol-sesquilignan, cyclolariciresinol and to a lesser extent lariciresinol, hydroxysecoisolariciresinol, and pinoresinol (335). Trace amounts of lariciresinol-sesquilignan, syringaresinol, hydroxymatairesinol, nortrachelogenin and todolactol were also found (271, 298).
Flaxseed contains phenolic acids and flavonoids. Major phenolic acids in flaxseed meal are ferulic and p-coumaric acids. These acids are largely present as glycosides also linked to SDG by ester links in complex macromolecules (337, 340) . The proportion of soluble esters to insoluble bound phenolic acids in defatted flaxseed flour is 9:1 (341). In comparison to other oilseeds, flaxseed appears richer in ferulic acid. Herbacetin (8-hydroxykaempferol), herbacetin 3,7-O-dimethyl ether and kaempferol 3,7-O-diglucoside have been identified in flaxseed but no estimates of their contents are so far available (338, 342)
.Since most lignans and phenolic acids in flaxseed are esterified or glycosylated in complex macromolecules, they must be hydrolysed to be quantified. Basic hydrolysis at a mild temperature hydrolyses the ester bounds and allows the release of p-coumaric acid 4-O-glucoside, ferulic acid 4-O-glucoside, and of the glycosides of the different lignans. Glycosides can be further hydrolysed by b-glycosidases (343) The release of the aglycones of lignans can also be achieved by acid hydrolysis, but in this case a transformation of the aglycone to other compounds, such as anhidrosecoisolariciresinol, can occur, and the quantification of all these compounds is necessary to determine the lignan content (344). Results obtained by both methods were considered acceptable for the database. Content of phenolic acids in flaxseed were determined after basic hydrolysis which liberates phenolic acid 4-O-glucosides.
Lignan contents were found to be strongly dependent on the flaxseed cultivars (345). Secoisolariciresinol and matairesinol contents were not affected by nitrogen supply during growth (346). The content of phenolic acids and flavonoids is also affected by the cultivar, year of growing and growing location (347, 348).
Poppy (Papaver somniferum) is a member of the Papaveraceae family. The seeds are used in many food items such as bagels, muffins and cakes. The seeds can be pressed into poppy seed oil, used in cooking. Poppy is consumed in many parts of Central and Eastern Europe. The sugared, milled seeds are eaten with pasta, or they are boiled with milk and used as filling or topping on various kinds of sweet pastry. Although poppy has narcotic properties, the amount of opiates in poppy seeds is not enough to produce a narcotic effect in cooking or consumption.
Currently, not much data exist on polyphenols in poppy seed or poppy seed oil. Trace amounts of lignans (matairesinol and lariciresinol) have been reported in poppy seed after hydrolysis.