Juan Fernández-Bolaños

Steam-explosion of olive stones: hemicellulose solubilization and enhancement of enzymatic hydrolysis of cellulose

Olive stones (whole stones and seed husks in fragments) were processed by steam-explosion under different experimental conditions of temperature and time, 200-236 degrees C for 2-4 min, with or without previous acid impregnation with 0.1%, H2SO4 (w/w). This paper examines the solubilization of hemicelluloses and their molecular weight distribution. The subsequent enzymatic hydrolysis of the solid residue, using a preparation of cellulase, was also studied. The maximum yield of the pentosan recovered in the water solution was 63% pentose in the starting material for seed husk treated at 200 degrees C for 2 min (log R0 3.24) prior to acid-impregnation, or at 215 degrees C for 2 min (log R0 3.69) without acid, compared to 39% of the potential yield for whole stones pre-impregnated with acid under more severe conditions (at log R0 = 4.07). This indicates that the autohydrolysis of hemicellulose in seed husks when compared to whole stones is enhanced. The molecular weight distribution of profile sugars showed that the depolymerization of hemicelluloses is a function of the severity of the treatment. Steam-explosion improved the accessibility of the cellulose and increased the enzymatic hydrolysis yield after steam-explosion with respect to material without steam explosion (ball-milled material), although little increase in the extent of saccharification occurred when the alkali-soluble lignin was removed. Only when the substrate was post-treated with Na-chlorite was the enzymatic hydrolysis improved, the water-insoluble residue being almost completely hydrolyzed in 8 h of incubation.

Characterization of the lignin obtained by alkaline delignification and of the cellulose residue from steam-exploded olive stones

The lignocellulosic by-products (whole stones and seed husks) obtained from pitted table olive and olive oil processing (respectively) were pretreated under various conditions of steam-explosion, with respect to pressure and time and with a dilute solution of sulfuric acid and without previous acid impregnation. The two materials exhibited considerable difference in behavior. The pre-impregnation of whole stones with low level of acid prior to steam treatment was necessary to improve the fractionation and the autohydrolysis of hemicellulose, while the results with seed husks were similar both with and without an acid catalyst. The lignins recovered from water-washed solid residue by alkaline-extraction followed by acidification were characterized. These lignin preparations from whole stones contained a very high amount of fat and almost no neutral sugars. The results also showed that these lignin preparations were guaiacyl-syringyl lignin, similar to exploded hardwood lignin, with an extensive cleavage of the β-aryl-ether linkage. The effect of treatment severity on the major physical properties of cellulose was also investigated. The cellulose fraction derived from steam-exploded whole stones was rapidly depolymerized as severity increased, leading to a degree of polymerization of 180, at a severity of log R0 = 4.07. In seed husks, under similar severity conditions, depolymerization of cellulose was much slower, and only reached a value of 821 (at log R0 = 4.07) or a value of 600 at log R0 = 4.34 without acid impregnation. The cellulose derived from both steam-exploded materials was moderately crystalline, the relative crystallinity index values of seed husks being higher than those of whole stones. The results indicated that the cellulose from seed husks was more protected than that of the whole stones in the steam-explosion process, and could be used to produce a cellulose with different properties and applications depending on severity and on the different treated material.

New Phenolic Compounds Hydrothermally Extracted from the Olive Oil Byproduct Alperujo and Their Antioxidative Activities

The application of a novel process based on the hydrothermal treatment of olive oil waste (alperujo) led to a final liquid phase that contained a high concentration of simple phenolic compounds. This study evaluated the effects of time (15-90 min) on the composition of the phenolic compounds isolated at a fixed temperature of 160 °C. Phenolic compounds were extracted with ethyl acetate. Both qualitative and quantitative HPLC analyses of the extracts showed variation of the concentrations of phenolic compounds with time. In addition, new phenols that were not present in the untreated control have been characterized. The antioxidant activities of different phenolic extracts was measured by various assays conducted in vitro: antiradical capacity (using DPPH and ABTS radicals), ferric reducing power (P(R)), inhibition of primary and secondary oxidation in lipid systems, and other tests, such as inhibition of tyrosinase activity. The results show that the phenolic extracts inhibited oxidation in aqueous and lipid systems to a significantly greater extent than the untreated control, and they performed as well as or better than vitamin E in this capacity.

Synthesis of Hydroxytyrosyl Alkyl Ethers from Olive Oil Waste Waters

The preparation of a new type of derivatives of the naturally occurring antioxidant hydroxytyrosol is reported. Hydroxytyrosyl alkyl ethers were obtained in high yield by a three-step procedure starting from hydroxytyrosol isolated from olive oil waste waters. Preliminary results obtained by the Rancimat method have shown that these derivatives retain the high protective capacity of free hydroxytyrosol.

Effects of Hydroxytyrosol and Hydroxytyrosol Acetate Administration to Rats on Platelet Function Compared to Acetylsalicylic Acid

Virgin olive oil (VOO) contains the polyphenols hydroxytyrosol (HT) and hydroxytyrosol acetate (HT-AC). This study investigated the antiplatelet effect of HT and HT-AC in healthy rats and compared their effects to acetylsalicylic acid (ASA). All compounds were administered orally for 7 days. HT and HT-AC inhibited platelet aggregation in whole blood, with a 50% inhibitory dose (ID50) of 48.25 mg/kg per day for HT, 16.05 mg/kg per day for HT-AC, and 2.42 mg/kg per day for ASA. Platelet synthesis of thromboxane B2 was inhibited by up to 30% by HT and 37% by HT-AC; the ID50 of this effect for ASA was 1.09 mg/kg per day. Vascular prostacyclin production was inhibited by up to 27.5% by HT and 32% by HT-AC; the ID50 of this effect for ASA was 6.75 mg/kg per day. Vascular nitric oxide production was increased by up to 34.2% by HT, 66% by HT-AC, and 64% by ASA. We conclude that HT and HT-AC administered orally inhibited platelet aggregation in rats and that a decrease in thromboxane synthesis along with an increase in nitric oxide production contributed to this effect.

Flavonoid Profile of Green Asparagus Genotypes

The determination of flavonoid profiles from different genotypes of triguero asparagus and their comparison to those from green asparagus commercial hybrids was the main goal of this study. The samples consisted of 32 commercial hybrids and 65 genotypes from the Huetor-Tajar population variety (triguero). The analysis of individual flavonoids by HPLC-DAD-MS has allowed the determination of eight naturally occurring flavonol derivatives in several genotypes of triguero asparagus. Those compounds included mono-, di-, and triglycosides of three flavonols, that is, quercetin, isorhamnetin, and kaempferol. The detailed analysis of the flavonoid profiles revealed significant differences among the distinct genotypes. These have been classified in three distinct groups as the result of a k-means clustering analysis, two of them containing both commercial hybrids and triguero asparagus and another cluster constituted by 21 genotypes of triguero asparagus, which contain several key flavonol derivatives able to differentiate them. Hence, the triglycosides tentatively identified as quercetin-3-rhamnosyl-rutinoside, isorhamnetin-3-rhamnosyl-rutinoside, and isorhamnetin-3-O-glucoside have been detected only in the genotypes grouped in the above-mentioned cluster. On the other hand, the compound tentatively identified as isorhamnetin-3-glucosyl-rutinoside was present in most genotypes of triguero asparagus, whereas it has not been detected in any of the commercial hybrids.

Dietary fibre content of table olives processed under different European styles: study of physico-chemical characteristics

Some European varieties of olive fruit (Douro, Hojiblanca, Cassanese, Conservolia, Taggiasca, and Thasos), processed under different conditions (black oxidised, fermented in brine or dried by different methods) were analysed, their contents of moisture, fat and dietary fibre being quantified. The percentages of moisture and fat were very different between varieties due to the different processing conditions, although differences between samples of the same variety were much less. The content of dietary fibre was around 12% of the fresh weight, although in dried samples this percentage increased to around 20%. Some physico-chemical characteristics (water holding capacity, cation exchange capacity, and ion retention capacity) were measured. The water holding capacities were related to moisture content, dry samples having the lowest values. Processed olives had very low cation exchange capacity in comparison to other vegetables, exhibiting the same relationship between this characteristic and moisture content. Olive fibre retained more iron than calcium under the assay conditions. © 2000 Society of Chemical Industry

Fibre fraction carbohydrates in Olea europaea (Gordal and Manzanilla var.)

Abstract Olive dietary fibre, Gordal and Manzanilla varieties, has been isolated by chemical (acid and neutral detergent fibre of Van Soest) and enzymatic (soluble and insoluble fibre of Asp) methods. NDF and ADF values were lower than IF. All of the fractions were hydrolysed and the resultant neutral sugars quantified. Glucose was the main component in NDF, ADF and IF, and arabinose was the major one in SF. The content of protein was significantly different between fractions but not between varieties, and the content of cellulose was significantly different between fractions and varieties. The determination of hemicelluloses by the Van Soest method showed a very low precision (cv. > 40%); determined by acid hydrolysis there were significant differences between fractions and varieties.

Isolation and identification of phenolic glucosides from thermally treated olive oil byproducts.

A liquid phase rich in bioactive compounds, such as phenols and sugars, is obtained from olive oil waste by novel thermal treatment. Two groups of fractions with common characteristics were obtained and studied after thermal treatment, acid hydrolysis, and separation by ultrafiltration, chromatography, and finally Superdex Peptide HR. In the first group, which eluted at the same time as oligosaccharides with a low DP (4-2), an oleosidic secoiridoid structure conjugated to a phenolic compound (hydroxytyrosol) was identified as oleuropeinic acid, and three possible structures were detected. In the second group, glucosyl structures formed by hydroxytyrosol and one, two, or three units of glucose or by tyrosol and glucose have been proposed. Verbascoside, a heterosidic ester of caffeic acid, in which hydroxytyrosol is linked to rhamnose-glucose or one of its isomers was also identified. Neutral oligosaccharides bound to a phenol-containing compound could be antioxidant-soluble fibers with bioactive properties.

Activity of glycosidases during development and ripening of olive fruit

ZusammenfassungEs wurde die Aktivität von verschiedenenp-Nitrophenyl-d-glycosidasen während der Entwicklung und Reifung der Oliven in drei Jahren (1987–88; 1988–89, 1989–90) untersucht. Es wurde keine Aktivität in der voll entwickelten Frucht festgestellt. Es wurden die Aktivitätenα-Galactosidase,β-Galactosidase,α-Mannosidase,α-Arabinosidase undα-Xylosidase entdeckt und ihre Molekularmassen durch Gelfiltration-Chromatographie mit Sephadex G-100 bestimmt. Es gibt eine zeitliche Wechselwirkung zwischen der enzymatischen Aktivität und der Abnahme in der Zuckerzusammensetzung in dem Nichtcellulose-Anteil der Zellwand.SummaryWe have studied the activity of variousp-nitrophenyl-d-glycosidases during development and ripening of olive fruit in three seasons (1987–88, 1988–89, 1989–90). Activity was absent in the first phases of ripening but appeared in the completely developed fruit,α-Galactosidase,β-galactosidase,α-mannosidase,α-arabinosidase, andα-xylosidase activities were detected and their relative molecular mass determined by gel filtration chromatography using Sephadex G-100. There is a temporal correlation between enzymatic activity and decrease in non-cellulosic cell-wall neutral sugar composition.