Avaliação do perfil lipídico e caracterização de compostos fenólicos de diferentes cultivares de noz-pecã [Carya illinoinensis (Wangenh) K. Koch]

Abstract

The state of Rio Grande do Sul is a large producer of pecan nut due to edaphoclimatic factors that significantly contribute to its cultivation, in addition to incentives that the government offers to small and medium producers as a source of extra income. Pecan is increasingly present on the table of consumers, contributing to a healthy diet, consisting of lipids, vitamins, minerals, proteins and compounds beneficial to the body, such as phenolic compounds, whose consumption has been correlated with lower probabilities of development of several diseases due to its antioxidant action. Pecan husks are widely used in teas due to their high antioxidant power. The objective of this work is to evaluate, in the nuts and shells of nine cultivars (Barton, Chickasaw, Imperial, Importada, Jackson, Melhorada, Mohawk, Pawnee and Shawnee) from the state of Rio Grande do Sul, the total lipid content, the profile of fatty acids, the antioxidant capacity, the content of total phenolic compounds and the identification and quantification of individual phenolic compounds. The lipids were determined using the Bligh-Dyer method and the fatty acids by GC-FID (gas chromatography with flame ionization detector), and these analyzes were carried out only on walnuts. Total phenolic composition by Folin-Ciocalteu, individual quantification by LC-DAD-MS/MS (liquid chromatography coupled to diode array detector and triple quadrupole mass spectrometer) and antioxidant capacity by ORAC method (radical absorption capacity) of oxygen) were performed for both walnuts and shells. The cultivar Imperial had the lowest content of total lipids (51.15%) and the cultivar Importada the highest content (63.18%). The major fatty acid found in all cultivars was oleic, ranging from 60.75 in cultivar Melhorada to 81.21% in cultivar Shawnee, followed by linoleic fatty acid with variation from 10.44 to 29.20% in cultivars Shawnee and Improved respectively, and palmitic with a variation of 5.31 to 7.90%, in the cultivars Mohawk and Improved respectively. The total phenolic compounds ranged in walnuts from 12.82 g equivalent in gallic acid (GAE).kg-1 (Barton) to 22.07 g GAE.kg-1 (Mohawk) and in shells from 75.48 g GAE.kg. -1 (Mohawk) to 239.92 g GAE.kg-1 (Pawnee). By LC-DAD-MS/MS, about 20 compounds were identified and quantified in the walnuts without hydrolysis and 15 compounds when hydrolyzed, as for the shells, also 20 compounds were identified and quantified without the application of hydrolysis and 17 compounds when hydrolyzed. The classes of phenolics that stand out both in nuts and in hydrolyzed or non-hydrolyzed shells are hydroxybenzoic and hydroxycinnamic acids, and flavonoids, with the major compounds gallic acid, ellagic acid, 4-hydroxybenzoic acid and protocatechuic acid. The antioxidant capacity varied in walnuts from 11.33 μmol equivalent in Trolox (TE).g-1 (Barton) to 150.80 μmol TE.g-1 (Pawnee) and in the shells from 53.38 μmol TE.g-1 (Mohawk) at 180.77 μmol TE.g-1 (Shawnee). Given the above, the present work brings out relevant information about the variability of lipid content, fatty acid profile, phenolic composition and antioxidant activity of nuts and their shells, from different pecan cultivars sold in the state of Rio Grande do Sul , also contributing with data of great value to the pecan industry and emphasizing the benefits of consuming this fruit and using the peel as potential antioxidants in the food industry. The information about the lipid percentage that each cultivar presents may help in the correct choice of certain cultivars for the oil industry or in the choice of nuts with lower lipid contents for application in bakery or confectionery products, in order to prevent rancidity of the products.