| 1. |
- Galanakis, Charis M., et al.
(författare)
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A study of the recovery of the dietary fibres from olive mill wastewater and the gelling ability of the soluble fibre fraction
- 2010
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Ingår i: LWT - Food Science and Technology. - : Elsevier BV. - 0023-6438. ; 43:7, s. 1009-1017
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Tidskriftsartikel (refereegranskat)abstract
- A novel method of the recovery of a dietary fibre containing material from olive mill wastewater (OMW) was developed. Extraction was based on thermal treatment with mixtures of ethanol and acids, prior to the isolation of the alcohol insoluble residue (AIR). Different mixtures were tested and the extracted residues were characterized. The maximum AIR recovery accounted 64.8 g/100 g OMW dry matter, while the corresponding total fibre content was 5.1 g/100 g of the AIR. Despite the high potassium (8.4 g/100 g) and the low galacturonic acid content (3.3 g/100 g), AIR was able to form gels after a simple isolation and concentration of the soluble fraction. The soluble fibres were exclusively composed of pectin (93.9 and 6.1 mol/100 mol galacturonic acid and arabinose, respectively) with 59 mol/100 mol GalA degree of methylation. The viscoelastic properties of the gels were evaluated as a function of galacturonic acid content, where the gel rigidity and elasticity was found to increase exponentially with this parameter. A further treatment of the pectin material with citric acid during its concentration, allowed the formation of more rigid, but less elastic gels. (C) 2010 Elsevier Ltd. All rights reserved.
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| 2. |
- Galanakis, Charis M., et al.
(författare)
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Clarification of high-added value products from olive mill wastewater
- 2010
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774. ; 99:2, s. 190-197
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Tidskriftsartikel (refereegranskat)abstract
- The objective of the current study is to investigate the clarification of two high-added value products (pectin containing solution and phenol containing beverage) recovered from olive mill wastewater. For this purpose, both liquids were processed with four types of ultrafiltration (100, 25, 10 and 2 kDa) and one nanofiltration membranes under optimum transmembrane pressure. Retention coefficients and performance parameters were monitored for each experiment. The membranes of 25 and 100 kDa showed very satisfying results with regard to the concentration of pectin solutions as they were able to separate it from cations and phenols. The membrane of 25 kDa was also able to partially remove the heavier fragments of hydroxycinnamic acid derivatives and flavonols, and simultaneously to sustain the antioxidant properties of the phenol containing beverage in the permeate stream. Finally, nanofiltration clarified the beverage from cations that passed in the permeate stream, but this process resulted in loss of antioxidant compounds, too. (C) 2010 Elsevier Ltd. All rights reserved.
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| 3. |
- Galanakis, Charis M., et al.
(författare)
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Dietary fiber suspensions from olive mill wastewater as potential fat replacements in meatballs
- 2010
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Ingår i: LWT - Food Science and Technology. - : Elsevier BV. - 0023-6438. ; 43:7, s. 1018-1025
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Tidskriftsartikel (refereegranskat)abstract
- A dietary fiber containing material, named as alcohol insoluble residue (AIR), was recovered from the olive mill wastewater (OMW). It was separated into different fractions (water soluble and insoluble AIR) and characterized with regard to fiber and ion content. Dynamic rheological tests of the water soluble fraction (WSAIR) were conducted in order to examine its gelling ability. Thereafter, AIR as well as WSAIR were utilized as fat replacement in meatballs together or separately with carrot and starch and compared with regard to the total, water and fat loss or oil uptake during frying of the meatballs. Results indicated that AIR could not be considered as a potential fat replacement in meatballs due to the restricted water holding ability. Nevertheless, WSAIR could be utilized together with carrot fibers as additive in low fat meatballs, since it was able to improve the cooking properties of the product, by restricting the oil uptake and thereby giving rise to meatballs with sustained reduced fat content. (C) 2009 Elsevier Ltd. All rights reserved.
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| 4. |
- Galanakis, Charis M., et al.
(författare)
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Recovery and preservation of phenols from olive waste in ethanolic extracts
- 2010
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Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley. - 0268-2575 .- 1097-4660. ; 85:8, s. 1148-1155
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The current trend of upgrading undervalued agricultural by-products involves the recovery of natural antioxidants. The purpose of this study was to recover phenols from fresh olive mill wastewater (OMW) with their dispersion in 85 mL ethanol per 100 mL and to investigate the effect of processing parameters on the phenol content and antioxidant capacity of the extracts. Moreover, all these characteristics were monitored over a period of 18 weeks in order to examine their preservation inside the ethanolic medium. RESULTS: Extraction time (30-120 min) was not critical for the process, while a pre-treatment step with the addition of ethanol in lower concentrations (20 mL per 100 mL or less) seems to affect negatively the recovery of the phenols in the final (85 mL per 100 mL) ethanolic medium. A pre-heating step of OMW at 50-60 degrees C as well as 80 degrees C resulted in reduction of the phenol concentrations and antioxidant activities of the extracts, probably due to the generation of enzymatic and non-enzymatic reactions, respectively. Nevertheless, extracts from the heat treated samples generally preserved their phenol characteristics as well as ferric ions reduction ability and indeed increased their radical scavenging activity during storage. CONCLUSION: Extraction of the phenols was mainly governed by their solubilization in the hydro-ethanolic mixture as well as the thermal pre-treatment of OMW. Results can be utilized to optimize the recovery and preservation of phenols from OMW in hydro-ethanolic mixtures. (C) 2010 Society of Chemical Industry
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| 5. |
- Galanakis, Charis M., et al.
(författare)
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The effect of heat processing on the functional properties of pectin contained in olive mill wastewater
- 2010
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Ingår i: LWT - Food Science and Technology. - : Elsevier BV. - 0023-6438. ; 43:7, s. 1001-1008
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to evaluate the effect of prolonged heat processing (180 min at 50-80 degrees C) on the functional and theological properties of pectin, derived from olive mill wastewater (OMW). It was shown that a low temperature blanching of OMW at 60 degrees C, activates endogenous pectin methyl esterase and promotes demethylation, despite the high concentration of phenols. Activation of the enzyme resulted in enhanced solubilization and subsequent partial degradation of pectin. The induced degradation impaired pectin grade and resulted in loss of gelling functionality. An alternative heating process at 80 degrees C resulted in negligible enzyme induced degradation of the pectin and improved gelling properties of the recovered material, despite the lower solubilization of the pectin. The obtained results contribute to a better understanding of the temperature effect on pectin functional properties and can be utilized in order to optimize pectin recovery from OMW. (C) 2010 Elsevier Ltd. All rights reserved.
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| 6. |
- Gekas, Vassilis, et al.
(författare)
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Contact angles of ultrafiltration membranes and their possible correlation to membrane performance
- 1992
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Ingår i: Journal of Membrane Science. - 0376-7388. ; 72:3, s. 293-302
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Tidskriftsartikel (refereegranskat)abstract
- The captive bubble method was used to describe the wetting characteristics of a number of commercial ultrafiltration (UF) membranes. The membranes belonged to one of two homologous (same material, different cut-off) series made by the same manufacturer. One series was made of polysulphone and the other one of cellulose triacetate. The porosimetric characteristics of the membranes have also been measured. The combined data were used to explain the fouling behaviour of the membranes upon ultrafiltration of solutions containing dextran, whey protein concentrate and silicate sols. The cellulose triacetate series is characterized by lower receding contact angle and smaller contact angle hysteresis and shows better flux behaviour (permeate flux during UF and pure water flux recovery at the end of UF) than the polysulphone series. Within the same series the mean permeability pore size shows a better correlation with membrane flux behaviour than with contact angle hysteresis.
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| 7. |
- Gomez, Federico, et al.
(författare)
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Changes in the carrot (Daucus carota L. cv. Nerac) cell wall during storage
- 2004
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Ingår i: Food Research International. - : Elsevier BV. - 0963-9969. ; 37:3, s. 225-232
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to examine biochemical changes in cell wall carbohydrates and extensin proteins during long-term storage of carrots (Daucus carota L. cv. Nerac). During the storage period of 6 months, cell wall fractions were isolated from the carrot at various times for carbohydrate and protein analysis. Signs of extensin cross-linking and its concomitant insolubilisation in the cell wall were found after 7 and 12 weeks of storage. During the same period the concentration of galactose and arabinose decreased, while other carbohydrate components as well as the degree of methylesterification remained virtually unchanged. After the 12th week of storage no changes in the extensin or carbohydrates were detected. Oxidative cross-linking between extensin molecules in the cell wall has been implicated in cell wall strengthening and may be part of the mechanism behind the storage-induced firmness of carrots. (C) 2003 Elsevier Ltd. All rights reserved.
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| 8. |
- Gomez, Federico, et al.
(författare)
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Cold acclimation of carrots during storage mechanical properties and antifreezing protein.
- 2003
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Ingår i: Acta horticulturae : technical communications of ISHS. - 0567-7572. ; 599, s. 699-703
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Konferensbidrag (refereegranskat)abstract
- Changes in the composition of carrot cell wall proteins were investigated, associating metabolic changes during long-term storage with changes in mechanical properties. Harvested carrots accumulate an antifreezing protein in their cell walls reaching a maximum level after 12 weeks of storage at 0°C, followed by a gradual decrease. During the same period of time, there is a decrease in the slicing force during the first 7 weeks of storage followed by an increase until the 12th week. The appearance and accumulation of the antifreezing protein suggest that structural changes leading to changes in mechanical properties during the first 12 weeks of storage might be associated with a cold acclimation process.
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| 9. |
- Gomez, Federico, et al.
(författare)
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Factors affecting quality and postharvest properties of vegetables: Integration of water relations and metabolism
- 2004
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Ingår i: Critical Reviews in Food Science and Nutrition. - : Informa UK Limited. - 1040-8398 .- 1549-7852. ; 44:3, s. 139-154
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Tidskriftsartikel (refereegranskat)abstract
- Growing of vegetables in the field, harvesting, handling in the packing house and storage are events in the lifetime of vegetables that arc analysed from the point of view of the complex series of physiological transitions taking place in each of these events. Water is the major factor limiting plant metabolism and plants have developed fascinating mechanisms to cope with this limiting factor. Therefore, water relations (water, pressure and osmotic potential) are used as criteria for discussing plant stress physiology aspects such as osmotic, elastic adjustment and cold acclimation, as well as mechanical stress when the vegetable is harvested and during handling in the packing house. Consequences for the storage potential and quality of the vegetable arc discussed. After harvesting, the postharvest cell has the ability to complete a complex series of physiological transitions that will influence vegetable quality and further processing operations. Metabolic changes in the cytosol, cell membrane and cell wall are described.
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| 10. |
- Gomez, Federico, et al.
(författare)
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Influence of cold acclimation on the mechanical strength of carrot (Daucus carota L.) tissue
- 2004
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Ingår i: European Journal of Horticultural Science. - 1611-4434. ; 69:6, s. 229-234
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the influence of cold acclimation on the mechanical strength of carrot (Daucus carota L.) taproots. Changes in the mechanical strength were monitored when cold acclimation was induced in carrot plants cultivated in a growth chamber under strict climate control and in taproots harvested from field cultivation, where the plants had been exposed to the natural variations in climate. The appearance and accumulation of an antifreeze protein in the cell wall isolated from cold-stored taproots showed that a cold acclimation process is in progress in the harvested taproot derived from carrot plants grown in the field. The force needed to slice the taproots significantly increased during the first 12 weeks of storage, where the higher concentration of the antifreeze protein indicated the highest development of cold acclimation during that period of time. The increase in tissue rigidity during cold acclimation was also shown by the increase of the Young's modulus in taproot tissue from carrot plants acclimated 11 weeks under controlled temperature conditions. After 24 weeks of storage there was a significant increase in slicing force that was accompanied by signs of cell membrane deterioration, as measured by relative electrolyte leakage. Thus, the later increase in tissue strength might be related with a senescence process.
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