Books by Stavros I . Lalas
Papers by Stavros I . Lalas
Annals of Nutrition and Metabolism, 2012
Vitamin E (VE) or α-tocopherol (a-toc) is the major fat soluble antioxidant in the human body, si... more Vitamin E (VE) or α-tocopherol (a-toc) is the major fat soluble antioxidant in the human body, since it protects cellular membranes and other lipids against oxidative damage as it reduces the formation of hydroperoxides (1). VE is easily oxidized in the air molecule, so must be protected from pro-oxidant elements which could affect its chemical integrity and decrease its physiological benefits (2)(3). Encapsulation constitutes a promising approach to preserve VE native properties over time and increase its concentration in aqueous media. Microencapsulation reduces reactivity with the environment (water, oxygen, light), decreases the evaporation or the transfer rate to the outside environment, promotes handling ability, masks taste and enhances dilution to achieve a uniform distribution in the final product when used in very small amounts(4).Liposomes have been studied as sustained delivery systems. β-lactoglobulin (β-Lg) has been studied extensively and has shown to bind a variety of hydrophobic molecules including fat soluble vitamins in vitro (5). The aim of this study was the preparation and characterization of β-lg-liposome formulation and the determination of VE encapsulation efficiency, in order to develop a new more efficient carrier for VE in aqueous media.
Contemporary Food Engineering, 2008
Grasas y Aceites, 1998
Resumen Se separaron semillas de tomate de la pulpa seca y posteriormente se trituraron y extraje... more Resumen Se separaron semillas de tomate de la pulpa seca y posteriormente se trituraron y extrajeron con éter de petróleo en caliente. El aceite extraído se desgomó, neutralizó y decoloró, y luego se determinaron las características físicas y químicas de los aceites ...
Grasas y Aceites, 1997
Page 1. Grasas y Aceites Vol. 48. Fase. 5 (1997), 267-272 267 ^B^^^BÍ ESTIGACIÔN Characterization... more Page 1. Grasas y Aceites Vol. 48. Fase. 5 (1997), 267-272 267 ^B^^^BÍ ESTIGACIÔN Characterization of crude and purified pumplcin seed oil By John Tsaknis, Stavros Lalas and Evangelos S. Lazos* ... 51, 1382-1383. 5. Lazos, ES, Tsaknis, J. and Bante, M. (1995). ...
Food Biophysics, 2015
The development and evaluation of a phospholipidsterol-protein membrane resembling system contain... more The development and evaluation of a phospholipidsterol-protein membrane resembling system containing βlactoglobulin (β-Lg) has been studied. Liposomes have been successfully employed for the protection, controlled release and site specific delivery of sensitive molecules, such as enzymes and vitamins. β-Lg (the major whey protein of ruminant species) was selected as model protein due to its ability to bind lipophilic molecules (i.e. phospholipids). Different techniques were used for the encapsulation studies (Differential Scanning Calorimetry, SDS polyacrylamide gel electrophoresis, Fourier Transform Infrared spectroscopy). Quantitation of encapsulation was estimated by Fluorescence spectroscopy. The stability study was carried out by turbidity measurements. The shape and size of the formulations prepared were assessed by Scanning Electron Microscopy and Dynamic Light Scattering. The developed system revealed a high encapsulation percentage of β-Lg, homogeneous and small shape and a very promising stability behavior. The characteristics obtained suggested that it is a very promising delivery system.
Journal of The Air & Waste Management Association, 2010
Cloud point extraction (CPE), a promising and simple technique for the separation of organic comp... more Cloud point extraction (CPE), a promising and simple technique for the separation of organic compounds using surfactants (Genapol X-080 [oligoethylene glycol monoalkyl ether] and PEG 8000 [polyethylene glycol with molecular weight of 8000]), was used to recover polyphenols from wine sludge (wine production waste). The effect of various parameters such as surfactant concentration, temperature, and pH on the percentage of phenol recovery and phase volume ratio during phenol separation from wine sludge was investigated, and the derived optimum parameters were used as the basis for the selection of CPE conditions. When a two-step CPE with a total of 4% v/v of Genapol X-080 (pH ϭ 3.5, temperature ϭ 55°C, and time ϭ 30 min) or 10% v/v of PEG 8000 (pH ϭ 2.5, temperature ϭ 55°C, and time ϭ 30 min) was applied the phenol recovery values achieved were 75.8 or 98.5%, respectively. Phenols recovered from wine sludge using the above surfactants maintained high antiradical activity as determined by the 1,1-diphenyl-2-picrylhydrazyl method.
Journal of Agricultural and Food Chemistry, 1999
The oil from Moringa oleifera variety Mbololo seeds from Kenya was extracted using three differen... more The oil from Moringa oleifera variety Mbololo seeds from Kenya was extracted using three different procedures including cold press (CP), extraction with n-hexane (H), and extraction with a mixture of chloroform/methanol (50:50) (CM). The oil concentration ranged from 25.8% (CP) to 31.2% (CM). The density, refractive index, color, smoke point, viscosity, acidity, saponification value, iodine value, fatty acid methyl esters, sterols, tocopherols (by HPLC), peroxide value, and E 1cm 1% at 232 and 270 nm and the susceptibility to oxidation measured with the Rancimat method were determined. The oil was found to contain high levels of unsaturated fatty acids, especially oleic (up to 75.39%). The dominant saturated acids were behenic (up to 6.73%) and palmitic (up to 6.04%). The oil was also found to contain high levels of -sitosterol (up to 50.07%), stigmasterol (up to 17.27%), and campesterol (up to 15.13%). R-, γ-, and δ-tocopherols were detected up to levels of 105.0, 39.54, and 77.60 mg/kg of oil, respectively. The induction period (at 120°C) of M. oleifera seed oil was reduced from 44.6 to 64.3% after degumming. The M. oleifera seed oil showed high stability to oxidative rancidity. The results of all the above determinations were compared with those of a commercial virgin olive oil.
A method is being proposed in order to discriminate bottled wines of different varieties when no ... more A method is being proposed in order to discriminate bottled wines of different varieties when no other information is known. The advantages of the method consist in the fact that anyone who wants to certify the variety, which is written on the label or the area of origin, can use such a technique to achieve the conformity. Additionally, the method can be easily applied by laboratories equipped with a GC. The differentiation has been achieved by using only seven of the total extracted volatiles, mainly higher alcohols and higher alcohol esters, namely 3-methyl-1-butanol, 2,3-butanediol, ethyl lactate, 3-methyl-1-butyl acetate, 2-phenylethanol, phenyl ethyl acetate and p-hydroxy phenyl ethanol. These key compounds are not relevant to a single variety. The proposed method does not take into account variables such as the year of vintage and fermentation procedures (agitation, temperature).
Vitamin E (VE) or α-tocopherol is the major fat-soluble antioxidant in the human body. It is a se... more Vitamin E (VE) or α-tocopherol is the major fat-soluble antioxidant in the human body. It is a sensitive, easily oxidized in the air, molecule, so it must be protected from pro-oxidant elements which could affect its physiological benefits. Encapsulation constitutes a promising approach to maintain VE native properties over time and increase its concentration in aqueous media. Liposomes have been studied as sustained delivery systems, being biodegradable, non-toxic and non-immunogenic. A new liposome/β-lactoglobulin formulation has been developed and characterized as a possible stable delivery system for VE. β-lactoglobulin (β-Lg) has been selected due to its property to bind a variety of hydrophobic molecules. The aim of this study was the preparation and characterization of β-Lg-liposome formulation and the determination of VE encapsulation efficiency, in order to develop a new more efficient carrier for VE in aqueous media.
Two Greek red wines (Syrah and Cabernet) were artificially aged with different wood chips (white ... more Two Greek red wines (Syrah and Cabernet) were artificially aged with different wood chips (white oak, red oak, Turkey oak, chestnut, Bosnian pine, cherry, common juniper, common walnut, white mulberry, black locust and apricot). The influence of each wood species was tested for up to 20 days. The optimum duration for the extraction of total polyphenols was 20 days (Syrah) or 10 days (Cabernet) when chips of white oak, chestnut, cherry, white mulberry, black locust and apricot where used. Resveratrol and catechin concentrations ranged within the limits previously reported in literature. A high antioxidant activity was established after 10 days of artificial aging. The sensory evaluation showed that the best results were produced by the apricot chips after 5 days (Syrah) or black locust and apricot after 5 days (Cabernet). Colour was seen to increase with both time of aging and number of wood chips added.
An improved method for the discrimination of oils and fats is being proposed. The method is based... more An improved method for the discrimination of oils and fats is being proposed. The method is based on the Principal Component Analysis and Discrimination Analysis of the results obtained by determination of the mole percentage of total fatty acids (fatty acid methylesters analysis by GC) and regiospecific distribution of the same fatty acids in positions 1 and 3 of triglycerides (using a regiospecific lipase and analysis by GC of the produced butylesters). Various samples (pure olive oils, various seed oils, mixtures of pure olive oils with seed oils, commercially available foods containing animal fats and/or vegetable oils and, finally, local pure olive oils from different areas of Greece) were subjected to the two transesterification treatments. It was proved that the proposed method has a global discriminating ability of identifying (at level of 5%) olive oil adulteration with various seed oils, discriminating animal fats from vegetable oils and animal fat adulteration with seed oils and, finally, discriminating of olive oils (on the basis of their geographical origin, in a small area like south Greece). Additionally, the introduced method includes a complete database (as a demonstration tool, mainly for olive oil) in order to be used by any concerned laboratory.
Natural antioxidants derived from plant sources attract considerable scientific interest. While c... more Natural antioxidants derived from plant sources attract considerable scientific interest. While classic extraction methods consume high volumes of toxic organic solvents, cloud point extraction requires surfactant not exceeding 15% of the waste volume. In preliminary tests, the suitability of various low hazard surfactants (Span 20, PEG 400, Tween 80 and 20) was explored for separation of phenols and carotenoids from olive mill wastewater and red-flesh orange juice. Tween 80 showed the highest recovery and further applied to the next experiments. The most appropriate surfactant concentrations were 5% (for olive mill wastewater) and 7% (for orange juice) as indicated by recovery % and the rest cloud point extraction parameters (analyte concentration, concentration factor, and phase volume ratio). A double step CPE with 5% + 5% of Tween 80 recovered up to 94.4% of the total phenols from olive mill wastewater, while a 7% + 7% of Tween 80 recovered up to 72.4% of the total carotenoids from orange juice. Evaluation of the final effects and extraction efficiency of single and double step cloud point extraction shows that double step scheme seems to be preferable in both cases. Finally, phenols and carotenoids recovered by Tween 80 maintained high antiradical activity (DPPH test).
This work was dedicated to reporting the full chemical and physical characterisation of Crambe ab... more This work was dedicated to reporting the full chemical and physical characterisation of Crambe abyssinica Hochst. seed oil. The oil from the seeds was extracted using n-hexane. The seeds contain about 30 % oil. Density, refractive index, colour, smoke point, viscosity, acidity, saponification value, iodine value, fatty acid methyl esters, the relative position of fatty acids in C1 and C3 carbon glycerol, sterols, tocopherols, peroxide value, E1%1cm at 232 nm, and the susceptibility to oxidation measured by the Rancimat method were determined. The oil was found to contain high levels of unsaturated fatty acids, especially C22:1 (63.77 %). The dominant saturated acid was C22:0 (2.14 %). The oil was also found to contain high levels of β-sitosterol (51.93 %), campestanol (21.98 %), and brassicasterol (12.35 %). α-, γ-, and δ-Tocopherols were detected up to levels of 7.67, 125.04, and 3.99 mg/kg, respectively. The induction period (at 110 °C and 20 l/h) of the oil was 8.83 h. The relative position of fatty acids in C1 and C3 position was as follows: linoleic 0.45 %, oleic 8.84 %, and erucic 90.72 %. The thermal profile of the oil presented a single peak at −20.94 °C.
1. Oxidative stability study of Greek traditional salads. (2003). I. Tsaknis, S. Lalas and V. Dou... more 1. Oxidative stability study of Greek traditional salads. (2003). I. Tsaknis, S. Lalas and V. Dourtoglou.
The antimicrobial activity of the oil extracted with n-hexane from the seeds of Moringa peregrina... more The antimicrobial activity of the oil extracted with n-hexane from the seeds of Moringa peregrina was tested against Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa, Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Candida albicans, C. tropicalis and C. glabrata. The oil proved effective against all of the tested microorganisms. Standard antibiotics (netilmycin, 5-flucytocine, intraconazole and 7-amino-4-methylcoumarin-3-acetic acid) were used for comparison. The resistance to oxidation of the extracted seed oil was also determined.
The effect of the addition of an essential oil (EO) preparation (containing a mixture of natural ... more The effect of the addition of an essential oil (EO) preparation (containing a mixture of natural and nature-identical EO) on the performance of dairy ewes of the Chios breed was investigated. Eighty lactating ewes were allocated into 4 equal groups in a randomized block design, each with 4 replicates of 5 ewes housed in the same pen. The 4groups were fed the same total mixed ration allowance, the roughage being a mixture of corn silage, lucerne hay, and wheat straw, and the concentrate based on cereals and oil cakes. Control ewes were fed their daily allowance of total mixed ration without any EO. The other 3groups were supplemented with EO at levels of 50, 100, and 150mg/kg of the concentrated feed, respectively. Individual milk yield was recorded daily and feed refusals were recorded on a pen basis weekly during the first 5 mo of lactation. Milk samples were analyzed for chemical composition, somatic cell count, and urea content. Rumen samples were analyzed for pH, NH3-N content, and protozoa, cellulolytic, hyper-ammonia-producing, and total viable bacteria counts. Results showed that inclusion of EO increased milk production per ewe, the effect being dose dependent [1.565, 1.681, 1.876, and 2.119 L/d (standard error of the difference ± 0.176) for the control, 50, 100, and 150mg of EO/kg of concentrate diets, respectively], and thus improved feed utilization. Although the inclusion of EO did not affect milk composition, it lowered urea concentration and somatic cell count in milk samples at the highest supplementation level compared with the control. Total counts of viable and cellulolytic bacteria and protozoa were not influenced by EO supplementation; however, counts of hyper-ammonia-producing bacteria were decreased at the 2 highest supplementation levels compared with the control group. Rumen pH was not affected by EO supplementation, but rumen NH3-N was reduced at the highest EO supplementation level, and acetate rumen concentrations tended to decrease and propionate to increase in a dose-dependent manner. In conclusion, EO supplementation may improve feed utilization and performance of the high-yielding dairy Chios ewes; however, the underlying mechanisms leading to this improvement merit further investigation.
The possibility to increase the nutritional value of table olives using polyphenols extracted fro... more The possibility to increase the nutritional value of table olives using polyphenols extracted from olive leaves was studied. Leaves were subjected to extraction using water with proportions of 1%, 5% and 10% of leaves and various temperatures and times (room temperature/24 h, 40 °C/10 min and 70 °C/5 min). The antioxidant activity of extracts was determined using the Rancimat method and their content in oleuropein and hydroxytyrosol was determined by HPLC. The extract with the highest antioxidant activity and polyphenol content (10% ratio of olive leaves extracted at room temperature for 24 h) was used for the treatment of debittered table olives. The treated and untreated olives were subjected to determination of their α-tocopherol, oleuropein and hydroxytyrosol content. A 457% increase was observed for oleuropein and 109% for hydroxytyrosol content after treatment. Sensory evaluation of treated table olives showed an increase in bitterness. However, treated and untreated table olives showed equal overall acceptability and overall preference.
Propolis (bee glue) is a well known natural product with healing properties. The chemical composi... more Propolis (bee glue) is a well known natural product with healing properties. The chemical composition of propolis is highly variable and depends mainly on the local flora. Greece is characterized by high biodiversity flora, assuming different propolis composition. In the framework of our continuing work on propolis samples from Greece and all around the world, four propolis samples from Peloponnese and one from the island of Kos were analyzed by GC/MS after silylation. In these samples the diterpenes: totarol, totarolone, abietic acid, imbricataloic acid, isoagatholal, agathadiol, communic acid, junicedric acid, 13-epi-cupressic acid and isocupressic acid have been identified as major constituents while the characteristic propolis flavonoids were either in small amounts or even absent. These findings confirm the presence of conifer trees as propolis plant sources in Greek samples. Diterpenes have been previously found in propolis samples from North-West Greece [2], Crete and Italy (Sicily) [3] while propolis from the temperate zone having Populus spp. as plant sources [1] have large amounts of esters of phenolic acids and flavonoids. All the samples showed significant antibacterial activity against nine Gram-negative and -positive human pathogenic bacteria and three fungi, probably due to the large amounts of diterpenes, while the antioxidative activity of all samples has been assayed as well thorough Rancimat method.
Uploads
Books by Stavros I . Lalas
Papers by Stavros I . Lalas