Tocopherol Content and Fatty Acid Distribution of Peas (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.)

The positional distribution of fatty acids (FA) of triacylglycerols (TAG) and major phospholipids (PL) prepared from four cultivars of peas (Pisum sativum L.) were investigated as well as their tocopherol contents. The lipids extracted from these peas were separated by thin-layer chromatography (TLC) into seven fractions. The major lipid components were PL (52.2–61.3%) and TAG (31.2–40.3%), while the other components were also present in minor proportions (5.6–9.2%). γ-Tocopherol was present in the highest concentration, and α- and δ-tocopherols were very small amounts. The main PL components isolated from the four cultivars were phosphatidylcholine (42.3–49.2%), followed by phosphatidylinositol (23.3–25.2%) and then phosphatidylethanolamine (17.7–20.5%). Small but significant differences (P < 0.05) in FA distribution existed when different pea cultivars were determined. However, the principal characteristics of the FA distribution in the TAG and the three PL were evident among the four cultivars; unsaturated FA were predominantly located in the sn-2 position, and saturated FA primary occupied the sn-1 or sn-3 position in the oils of the peas. These results suggest that the regional distribution of tocopherols and fatty acids in peas is not dependent on the climatic conditions and the soil characteristics of the cultivation areas during the growing season.     

Assessment of in vitro antioxidant capacity of the seed coat and the cotyledon of legumes in relation to their phenolic contents

Methanolic extracts of the seed coat and the cotyledon of two varieties of lentils (Lens culinaris L.) and two varieties of dark peas (Pisum sativum L.), were analysed for their antioxidant capacities (EC₅₀), in the form of free radical-scavenging activities. Huge differences have been observed in the antioxidant capacity in the seed coat and the cotyledon in both legumes. The seed coat, in which are located, principally, phenolic compounds with flavonoid structures, presents higher antioxidant activity than the cotyledon in lentils and peas, showing differences in both species but not very large differences between varieties. An analysis of principal components was applied to the results in order to relate the antioxidant capacity of these legumes with their phenolic composition previously established by the authors.     

Correlations of ingredients with sensory attributes in green beans and peas under different storage conditions

The total ascorbic acid contents and the antioxidant capacity in green beans and in peas were measured during deep-frozen storage and compared to storage at 4 °C and 20 °C. In green beans only, the flavonols quercetin and kaempferol were measured. The results were correlated with sensory attributes which were evaluated at the same storage stages. The total ascorbic acid content is a good parameter for the storage time of both vegetables and showed, for peas, a positive correlation with the attribute “sweet taste” and a negative correlation with the attribute “musty” odour. The total ascorbic acid content of green beans was positively correlated with a “squeaky” texture and negatively with a “musty” taste. The flavonol content and the antioxidant capacity were more stable during the storage process and showed less correlation with sensory attributes.     

Occurrence of phenolic compounds in the seed coat and the cotyledon of peas (Pisum sativum L.)

This work determined the phenolic composition of the seed coat and the cotyledon of two varieties of dark peas (Pisum sativum L), Fidelia and ZP-840, by HPLC-PAD and HPLC-MS. High concentrations of glycosides of quercetin, luteolin and apigenin were found in the seed coat of both varieties of peas. Minor concentrations of monomers and dimers of proanthocyanidins were identified. The cotyledon mainly contains hydroxybenzoic and hydroxycinnamic compounds and some of the flavone and flavonol glycosides found in the seed coat. Two conjugated compounds with malic acid, trans p-coumaroyl-malic acid and p-hydroxybenzoyl-malic acid were identified in the cotyledon and in the seed coat, and the stilbene trans-resveratrol-3-glucoside, only in the seed coat. These compounds had not been previously reported in peas. The results obtained allow an overview of the distribution of the phenolic compounds in the seeds of these varieties of peas, and contribute to the knowledge of the implications of these compounds in the dietary intake.     

RADIATION EFFECTS ON SOME PHYSICO-BIOCHEMICAL CHANGES IN PISUM SATIVUM

Effect of irradiation treatment (0.5, 1.0, 2.0 and 4.0 kGy) on fresh pea cultivars was investigated. Results indicated that significant decrease in colour (% transmittance) and ascorbic acid occurred due to storage period. Higher irradiation treatments showed a significant difference in colour retention in both the cultivars. Visual observation indicated no sprouting until 6th days after which sprouting started in both the cultivars irrespective of radiation treatments. At higher irradiation dose (4.00 kGy) sprouts died soon after emergence. Peas irradiated at 2.0-4.0 kGy doses showed rottage after 9-12 days of storage in both the varieties. Higher irradiation doses enhanced the rate of rot compared with lower doses, p-8 was more resistant to rottage than Moon cultivar of pea.     

Correlations between some nitrogen fractions,lysine, histidine,tyrosine, and ornithine contents during the germination of peas,beans, and lentils

The effect of different germination conditions, namely, germination time and total presence or absence of light, on the content of the various nitrogen fractions, three essential protein amino acids (Lys, His, and Tyr) and one non-protein amino acid (Orn), was studied in peas, beans, and lentils. The influence of light during germination on the parameters considered varied according to the legume but on the whole was less important than the influence of germination time in quantitative terms. In all three legumes, prolonging the germination time yielded flours that contained more non-protein nitrogen (NPN) and Orn and less protein nitrogen (PN) and Lys, while the changes in the His and Tyr contents varied with legume type. In addition, changes in the Lys, Tyr, and Orn contents correlated with the changes in the NPN and PN levels in the germinated legumes.     

The relationship between lipid oxidation and antioxidant content in postharvest vegetables

Abstract

Lipid oxidation is the quality limiting attribute in many vegetables that generates off‐flavors. Lipoxygenases, which catalyze the oxygenation of polyunsaturated fatty acids are key enzymes in this pathway and their presence is believed to be the chief reason for the need for blanching (i.e., inactivation of enzymes) enabling frozen storage. Off‐flavor production in legumes, such as garden peas, is a particular problem, due to high levels of this enzyme found in these seeds.

The lipid oxidation pathway is triggered in response to tissue wounding which occurs during mechanical harvesting of peas in the field. Bruised peas that are not blanched develop strong off‐flavors within a few hours.

A number of studies has shown that antioxidants are consumed during lipid oxidation. Vitamin C (ascorbate) is an antioxidant and also an important micronutrient in peas. It is possible that the level of vitamin C is affected by the progress of lipid oxidation in postharvest peas.     

Assessment of the nutritional quality of raw and extruded Pisum sativum L. var. laguna seeds

Pea (Pisum sativum L. var. Laguna) seeds were submitted to extrusion process at 129, 135 and 142 °C and modifications on the proximate composition and nutritional parameters were evaluated. Peas were a good source of protein (24 g/100 g), amino acids (sulphur amino acids were the limiting ones), dietary fibre (18 g/100 g), carbohydrates (53 g/100 g), energy (330 kcal/100 g), riboflavin and thiamine (0.1-0.2 mg/100 g). Pea seeds also contained non-nutritive compounds such as α-galactosides (4 g/100 g), phytic acid (0.4 g/100 g) and trypsin inhibitor activity (2 TIU/mg). Extrusion cooking caused a slight increase of protein and fat content, whilst it reduced dietary fibre, thiamine and α-galactosides, and led to negligible trypsin inhibitor activity (TIA) levels. The protein quality of pea measured by biological indexes (net protein utilisation, net protein ratio, relative net protein ratio, true protein digestibility and biological value) was not affected by extrusion treatments. Protein quality measured by chemical indexes (chemical score and protein digestibility corrected amino acid score) decreased in processed peas. Among extruded peas, those processed at 135 °C presented the highest chemical indexes. Therefore, the aforementioned condition could be considered adequate for the manufacture of novel pea-derived products with high nutritive value.     

Composition and in vitro digestibility of raw versus cooked white‐ and colour‐flowered peas

Ten pea cultivars (four white‐flowered, Pisum sativum ssp. hortense, and six colour‐flowered, Pisum sativum ssp. arvense) grown in Latvia were analyzed and tested in in vitro experiments, as raw and cooked seeds. The colour‐flowered (CF) had a greater proportion of hulls and a higher acid detergent fibre (ADF) content than white‐flowered (WF) pea seeds (10.7 vs. 8.2% and 92.2 vs. 84.5 g/kg dry matter (DM), respectively). Three out of six CF varieties had a significantly greater amount of protein bound to neutral detergent fibre (NDF) than WF peas. The tannin content was higher in CF than in WF peas (8.46 vs. 0.37 g/kg DM). In vitro protein and amino acid digestibility was about 8% higher in WF than in CF varieties. Cooking decreased the tannin content in CF peas (8.46 vs. 5.51 g/kg DM) but had no effect on in vitro protein digestibility. Heat treatment reduced significantly trypsin inhibitor activity and amount of protein bound to NDF in CF and WF varieties (from 6.50 to 0.52 and from 6.54 to 0.46 trypsin inhibitor units (TIU)/mg DM; from 1.250 to 0.831 and 0.761 to 0.209 g N/100 g NDF, respectively). However, the protein bound to NDF content in pea DM increased in CF and decreased in WF varieties (from 1.525 to 2.145 and from 0.913 to 0.502 g N/kg DM, respectively). Cooking resulted in an increased NDF content over two times in both CF and WF pea seeds (from 122 to 259 and from 120 to 262 g/kg DM, respectively). The results suggest that colour‐flowered pea may be considered as an interesting dietary alternative to white‐flowered pea since cooking removes trypsin inhibitor activity (TIA), decreases tannins, and increases dietary fibre contents.     

Influence of the action of exogenous enzymes on the polyphenolic composition of pea: Effect on the antioxidant activity

The polyphenolic composition of green pea (Pisum sativum, variety Esla) was determined by HPLC-DAD and HPLC-(ESI)MS procedures. The action of the enzymes tannase, α-galactosidase, phytase and viscozyme on pea flours, at a semi-pilot scale, was assayed for the polyphenolic composition. Different modifications in the initial concentration of polyphenolics occur depending on the enzyme, but a general decrease was observed in all of them. Free radical scavenging activity of the methanolic extracts, determined by the DPPH test, was also evaluated. The treatments with phytase, viscozyme, α-galactosidase or tannase produced a decrease in the antioxidant activity when compared to raw peas. The results of the analysis of principal components to examine the relationship between antioxidant activity (EC₅₀) and concentrations of polyphenolics in each of the pea samples showed that the hydroxycinnamic compounds are the most related to antioxidant activity.