antioxidants extraction optimization pinelo jafc

Effect of Solvent, Temperature, and Solvent-to-Solid Ratio on the Total Phenolic Content and Antiradical Activity of Extracts from Different Components of Grape Pomace MANUEL PINELO,* MONICA RUBILAR, MARı Á JEREZ, JORGE SINEIRO, AND MARı Á JOSE Ä NU Ä N ˜ EZ Escuela Te ćnica Superior de Ingenierı á, Universidad de Santiago de Compostela, Lope Go ´mez de Marzoa, 15782 Santiago de Compostela, Spain Grape byproduc ts were subjected to an extrac tion process under variou s diff erent experime ntal conditions (namely, solvent type, temperature, solvent-to-solid ratio, time contact, and raw material) in ord er to stu dy the effect of the se condit ion s on the yield of phe nol ic compou nds and the corresponding antiradical activity of extracts. Although the order of decreasing capacity to extract soluble materials was ethanol > methanol > water, methanol was the most selective for extracting phenolic compounds. Temperature and solvent-to-solid ratio were found to have a critical role in extraction efficiency; values of 50 °C (between 25 and 50 °C) and 1:1 (between 1:1 and 5:1) maximized the antiradic al activ ity of pheno lic extra cts. In addit ion, extracts from grape samples previousl y subjected to distillation reached higher antiradical values in comparison to those coming directly from pressing; in both cases, seed extracts showed better results than those of stem when ethanol or water was employed, whereas the opposite occurred in the case of methanol. These differences were attributed to the different phenolic compositions of the considered fractions. KEYWORDS: Gr ape (Viti s vini fera ); pheno lic comp ounds; extraction ; antir adical activ ity; solven t; temperature INTRODUCTION Because world populatio n is in continuous growth and natural resou rces are conseq uentl y limi ted, studies deali ng with the utilization of renewable sources and the design of processes bas ed on the int egr al exploi tat ion of nat ura l pro duc ts hav e attracted great interest in the past several years. The recovery of byproducts from agricultural industries to be converted into val ue- added produc ts is a good exa mpl e. In Eur ope ∼112 million tons of grape was processed by the wine industry in 1998. An estimated 13 wt % of this amount corresponded to the byproduct after pressi ng, consistin g of skins, seeds, and stems, which can be a rich source of phenols (1-3). The interest in these compounds is based on their well-known capacity to scavenge free radicals. The generation of these species plays a remarkable role in the progression of a wide range of diseases such as cancer, atherosclerosis, and inflammation processes (4, 5). Furthermore, these compounds were found to be responsible for li pi d oxidat ion, whic h is a major determinant in the deterioration of foods during processing and storage (6 ). Some phenolic compounds present in natural products showed a higher antiradical activity than the synthetic antioxidants, the utilization of which in the food industry is common and restricted. In Europe, the use of such antioxidants is regulated by Directive 95/2/EC; 3-tert -butyl-4-hydroxyanisole (BHA) is permitted in oils and fats up to 200 mg/kg, whereas 3,5-di- tert -4-butylhy- droxytoluene (BHT) is permitted up to only 100 mg/kg (7 ). In light of these consider atio ns, the viabilit y of phenol ic compounds with antiradical power to be used as food preserva- tives or dietary supplements for disease prevention is ensured. However, the economical feasibility of an industrial process also requires working in such a way that high values of efficiency are attained. Some factors could contribute to reach this aim: (1) optimizing the values of the variables with a direct influence on the pro ces s, (2) corre ctl y cho osi ng the raw mater ial s to extrac t, and (3) subjec tin g the se mat eri als to approp ri ate pretreatment. Extr actio n effi cienc y is commonly a funct ion of proce ss conditions. Previous findings have reported the influence of some variables (e.g., temperatur e, time contact, solvent-to-soli d ratio, etc.) on the phenolic yields capable of being extracted from div ers e nat ural pro ducts such as almond hul ls, pine sawdust, or apple byproducts (8, 9). The positive or negative role of each factor in the mass transfer of the process is not always obvious; the chemical characteristics of the solvent and the diverse structure and composition of the natural products ensure tha t each mat erial -sol vent system shows dif fer ent behavior, which cannot be predicted. * Corr esponding a uthor (telephone +34.981.563100, ext. 16785; fax +34.981.528050; e-mail [email protected]). J. Agric. Food Chem. 2005, 53, 2111−2117 2111 10.1021 /jf048 8110 C CC: $30.25 © 2005 Ameri can C hemical Soci ety Published on Web 02/18/2005

antioxidants extraction optimization pinelo jafc

Documents