Konstantinos Petrotos

Osmotic concentration of liquid foods

Vast amounts of liquid food are industrially concentrated in order to reduce storage, packaging, handling and transportation costs. Vacuum evaporation is the predominant method used by the food industry to produce liquid food concentrates, despite serious drawbacks (poor product quality, high energy demand). This paper describes the research efforts to develop alternative techniques that could be applied on an industrial scale to overcome the disadvantages of currently used concentration methods. A major part of these attempts is focused on the application of osmotic membrane techniques, namely direct osmosis, membrane distillation and osmotic distillation.

A study of the direct osmotic concentration of tomato juice in tubular membrane - module configuration. I. The effect of certain basic process parameters on the process performance

Abstract A novel tubular module was used to investigate the direct osmosis concentration process in the case of tomato juice. This module, was constructed, according to given specifications, by PCI UK and consisted of an external stainless steel shroud accommodating, internally, a set of two identical RO membrane tubes having no support lengthwise and properly sealed at their ends. The process performance was measured in terms of water permeation flux and its response to changes of the process parameters was experimentally assessed and established. The process parameters which were investigated in the course of this study were: the kind of osmotic medium, the viscosity of osmotic medium, the osmotic medium concentration, the juice temperature, the juice flow rate, the juice concentration and the membrane thickness. Sodium chloride brine was found to be the best osmotic medium, among the six which were tried, and this was due to its very low viscosity. The above parameter appears to be of paramount importance regarding the effectiveness of an osmotic medium. Higher osmotic medium concentrations yielded to higher osmotic permeation rates. Increasing the juice temperature was found to markedly increase the permeation flux. However, only a slight enhancement of flux was observed by increasing the juice flow rate. Moreover, higher juice concentrations up to approximately 12° Brix led to a lowering of the osmotic flux. Finally, as far as the membrane thickness was concerned, a strong trend was revealed for exponential increase of permeation by shifting towards lower membrane thicknesses. This trend however needs to be further investigated as an inadequate number of experimental points were obtained due to lack of additional membranes.

Olive Mill Wastewater Treatment

The cultivation of olive trees and the production and use of olive oil has been a well-known and established practice in the Mediterranean region for more than 7000 years. The consumption of olive oil is rapidly increasing worldwide, due to its high dietetic and nutritional value. According to the IOOC (2004), the production of olive oil increased from 1.85 million tons in 1984 to 3.17 million tons in 2003 (70% increase) (Table 8.1). There are approximately 750 million productive olive trees worldwide, 98% of them located in the Mediterranean region, where more than 97% of olive oil is produced. The three major olive oil producers worldwide are Spain, Italy, and Greece, followed by Turkey, Tunisia, and to a lesser extent Portugal, Morocco, and Algeria. The data presented in Figure 8.1 reflect the importance of the olive oil sector in the Mediterranean area and consequently the magnitude of the problems related with the disposal of large amounts of wastes produced during olive oil production. The traditional press extraction method as well as the continuous three-phase decanter process, which is most widely used for the production of olive oil, generate three products: olive oil (20%) and two streams of waste: a wet solid waste (30%) called ‘‘crude olive cake’’ or ‘‘olive husk’’ and an aqueous waste called ‘‘olive mill wastewater’’ or ‘‘olive mill effluent’’ or ‘‘alpechin’’ (50%). The solid waste (crude olive cake) is the residue that remains after the first pressing of the olives and is a mixture of olive pulp and olive stones. At present, olive husk is processed in seed oil factories in order to extract the small amount of oil remaining in the waste. Both crude and exhausted olive cake can be used as solid fuels (due to their high heating

Salinity effect on nutritional value, chemical composition and bioactive compounds content of Cichorium spinosum L.

Soil salinization is an increasing problem for many areas throughout the world that renders prohibitive vegetables and crop production in general. In the present study, Cichorium spinosum L. plants were grown under saline conditions in order to evaluate chemical composition and bioactive compounds content of their leaves. Salinity increase resulted in significant changes of macro and micro-nutrients content (nutritional value, sugars, fatty acids, minerals, ascorbic acid and tocopherols), whereas the concentration of phenolic compounds was not significantly affected. Chicoric and 5-O-caffeoylquinic acid were the most abundant phenolic acids. In contrast, antioxidant activity and mineral composition were beneficially affected by mid-to-high and high salinity levels. In conclusion, C. spinosum can be cultivated under saline conditions without compromising the quality of the final product, especially in semi-arid areas where irrigation water is scarce and/or of low quality due to high content of NaCl (coastal areas or areas where underground water is saline).

A study on the kinetics of olive mill wastewater (OMWW) polyphenols adsorption on the commercial XAD4 macroporous resin

Abstract The commercially available macroporous resin XAD4 was evaluated for its capacity to adsorb the polyphenols contained in olive mill wastewater (OMWW). The adsorption was performed in the mode of fixed packed bed contactor. The effects of OMWW flow rate, temperature, dilution and pH on the resin adsorption capacity were investigated. Polyphenols concentration decreased with time. The pattern of the total polyphenols concentration dependence on time was found similar in all cases. The pattern included a very steep section for roughly the first 2 h of the operation, followed by a second section of decreasing gradient down to a final asymptotic equilibrium limit. Neither the time required for approaching the equilibrium nor the magnitude of the equilibrium concentration was substantially affected by the OMWW temperature. The increase of OMWW flow rate affected markedly the speed of approaching the equilibrium but not its position. The variation of the total polyphenols concentration showed that higher...

The Effects of an Olive Fruit Polyphenol-Enriched Yogurt on Body Composition, Blood Redox Status, Physiological and Metabolic Parameters and Yogurt Microflora

In the present study we investigated the effects of an olive polyphenol-enriched yogurt on yogurt microflora, as well as hematological, physiological and metabolic parameters, blood redox status and body composition. In a randomized double-blind, crossover design, 16 (6 men, 10 women) nonsmoking volunteers with non-declared pathology consumed either 400 g of olive fruit polyphenol-enriched yogurt with 50 mg of encapsulated olive polyphenols (experimental condition—EC) or 400 g of plain yogurt (control condition—CC) every day for two weeks. Physiological measurements and blood collection were performed before and after two weeks of each condition. The results showed that body weight, body mass index, hip circumference and systolic blood pressure decreased significantly (p < 0.05) following the two-week consumption of yogurt regardless of condition. A tendency towards significance for decreased levels of low density lipoprotein (LDL) cholesterol (p = 0.06) and thiobarbituric acid reactive substances (p < 0.05) following two weeks of polyphenol-enriched yogurt consumption was observed. The population of lactic acid bacteria (LAB) and production of lactate in yogurt were significantly enhanced after addition of olive polyphenols, contrary to the population of yeasts and molds. The results indicate that consumption of the polyphenol-enriched yogurt may help individuals with non-declared pathology reduce body weight, blood pressure, LDL cholesterol levels and lipid peroxidation, and promote growth of beneficial LAB.

Chemical Composition and Yield of Six Genotypes of Common Purslane (Portulaca oleracea L.): An Alternative Source of Omega-3 Fatty Acids

Common purslane (Portulaca oleracea L.) is an annual weed rich in omega-3 fatty acids which is consumed for its edible leaves and stems. In the present study six different genotypes of common purslane (A-F) were evaluated for their nutritional value and chemical composition. Nutritional value and chemical composition depended on genotype. Oxalic acid content was the lowest for genotype D, whereas genotypes E and F are more promising for commercial cultivation, since they have low oxalic acid content. Genotype E had a very good antioxidant profile and a balanced composition of omega-3 and omega-6 fatty acids. Regarding yield, genotype A had the highest yield comparing to the other genotypes, whereas commercial varieties (E and F) did not differ from genotypes B and C. This study provides new information regarding common purslane bioactive compounds as affected by genotype and could be further implemented in food industry for products of high quality and increased added value.

Purification of Olive Mill Wastewater Using Microfiltration Membrane Technology

Olive mill wastewater (OMWW), a by-product of the olive oil extraction process, is a severe polluting waste, but also a source of antioxidants; polyphenols, especially hydroxytyrosol. This study aimed at investigating the potential of microfiltration (MF) for separating the polyphenols from OMWW. OMWW treatment consisted of a preliminary centrifugation step, followed by MF for the separation of fats and polyphenols.Two types of ceramic MF membranes were used. MF flux ranged between 78 and 95 kg m -2 h -1 , indicating the applicability of the described process on commercial scale. Better results were obtained with MF membrane of 50 nm pore size, due to its higher porosity compared to the membrane of 200 nm pore size. The optimum operative conditions were transmembrane pressure of 3.5 bar, flow rate of 10 m s -1 , and temperature of approximately 55 °C. A 3-month storage of OMWW prior to treatment resulted in a 20% decrease in permeate flux, indicating that direct processing of the OMWW is necessary. Membrane pollution was not a problem for MF operation and did not affect membrane permeability significantly. Restoring the permeability of water to baseline levels after each use, confirmed the successful cleaning regime applied. The microfiltrate was an excellent antioxidant, which contained useful polyphenols, including hydroxytyrosol, tyrosol, p- coumaric acid, caffeic acid and catechin. Olive oil production is a key economic activity in the Mediterranean region. Olive mill wastewater (OMWW), a by-product of the olive oil extraction process, is a mixture of vegetation water containing soft tissues of the olive fruit, and the water used in the various stages of the oil extraction process, and is considered to be a significant polluting waste in all Mediterranean countries. OMWW constitutes a serious environmental problem in the area, mainly due to its low pH, high solids and organic compounds, high COD content, phytotoxic properties and resistance to biodegradation caused by its phenolic compounds (1, 2). In terms of pollution effect, 1 m

Short communication: Determination of lactoferrin in Feta cheese whey with reversed-phase high-performance liquid chromatography

In the current paper, a method is introduced to determine lactoferrin in sweet whey using reversed-phase HPLC without any pretreatment of the samples or use of a separation technique. As a starting point, the most common HPLC protocols for acid whey, which included pretreatment of the whey along with a sodium dodecyl sulfate-PAGE step, were tested. By skipping the pretreatment and the separation steps while altering the gradient profile, different chromatographs were obtained that proved to be equally efficient to determine lactoferrin. For this novel 1-step reversed-phase HPLC method, repeatability was very high over a wide range of concentrations (1.88% intraday to 5.89% interday). The limit of detection was 35.46μg/mL [signal:noise ratio (S/N)=3], whereas the limit of quantification was 50.86μg/mL (S/N=10). Omitting the pretreatment step caused a degradation of the columns lifetime (to approximately 2,000 samples). As a result, the lactoferrin elution time changed, but neither the accuracy nor the separation ability of the method was significantly influenced. We observed that this degradation could be easily avoided or detained by centrifuging the samples to remove fat or by extensive cleaning of the column after every 5 samples.

Effects of Dietary Grape Pomace Supplementation on Performance, Carcass Traits and Meat Quality of Lambs

Background/Aim: A previous study revealed that the inclusion of grape pomace (GP) in the diet for growing lambs had beneficial effects on the redox status and fecal microbiota. Herein, we investigated the effect of GP inclusion on performance, carcass traits and fatty acid composition of meat. Materials and Methods: In the experimental trial of 55 days, lambs were fed with standard or diet supplemented with GP. Performance, carcass traits and fatty acid profile of quadriceps muscle were assessed. Results: GP inclusion in the diet improved growth performance, since the average daily gain was significantly increased by 2-fold in GP group. Regarding the fatty acid composition of meat, GP inclusion significantly increased the content of long chain n-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid, and reduced the n-6/n-3 ratio compared to the control group. Conclusion: GP supplementation in lamb diet may improve performance and may have beneficial effects on meat quality.