IMEKO Event Proceedings Search

   

Page 253 of 977 Results 2521 - 2530 of 9762

Pelvan. E., Olgun, E., Karadağ, A., Alasalvar, C.
Comprehensive identification of polyphenols in different hazelnut products

The aim of this study was to identify the polyphenolic profiles of hazelnut products (natural hazelnut, roasted hazelnut, hazelnut skin, and cold press hazelnut oil).
Within the scope of the study, polyphenolic profiles of hazelnut products were analysed tentatively. Q-Exactive LC/MS/MS (orbitrap) was used to tentatively identify the new polyphenolic compounds in hazelnut products and 32 compounds were detected, of which 16 were identified for first time in hazelnut products. The majority of polyphenols were detected in hazelnut skin, while epicatechingallate was the only phenolic compound detected in hazelnut oil. As a result, the present study suggests that hazelnut skin is a good source of polyphenols and can be used as source of functional ingredients.

Karadag, A., Hermund, D. B., Alasalvar, C., Jacobsen, C.
Oxidative stability and microstructure of granola bars enriched with fish oil and algal antioxidants

In this study, the ability of Icelandic brown algae (Fucus vesiculosus) extracts inhibiting lipid oxidation in granola bars fortified with fish oil- in-water emulsion was investigated. It was also explored whether addition of the algal extracts affected the physical microstructure of the fish oil droplets in granola bars. The oxidative stability of the bars stored at 20°C was evaluated over a period of 10?week by measuring the development of peroxides, the change in fatty acid composition and volatile compounds by GC-FID and DHS GC-MS. The physical microstructure was visualized by microscopy including, SEM, ESEM and CLSM. All extracts, except water extract at low concentration, reduced lipid oxidation storage when added at a concentration of 0.5 or 1?g extract/100?g fish oil emulsion. Ethanol (EE) and acetone extracts (AE) were found to be most efficient antioxidants. The concentration dependent antioxidant efficacy of these two extracts was among others related to an improved incorporation of the fish oil-in-water emulsions in the bars, high total phenolic content, high radical scavenging activity together with high interfacial affinity of phenolic compounds and probably regeneration of tocopherol. Furthermore, the microstructure of granola bars prepared with EE and AE showed fewer oil pools and more ordered oil droplets. This study showed the application potential of F. vesiculosus extracts as a natural antioxidant in low-moisture foods such as granola bars.

Ritzoulis, C.
Towards some common protocols for the extraction of hydrocolloids from plant sources: Challenges and emerging opportunities

Isolation and purification of hydrocolloids (thickeners and emulsifiers) from plant sources can be typically broken down into three distinct stages: The preparation of a food matrix for the extraction of the hydrocolloids; the extraction event itself; and the purification of the product. These procedures, as used today, are naturally differentiated from one source to another, due to the differing challenges involved in different plant materials. Moreover, the sequence of the processing can lead to end products with substantial differences in composition and properties.
However, the need for interlaboratory collaboration, for application on other plant matrices, for demo actions, and for the scaling-up of the production of such novel materials press the need for standarized products. A close examination of this group's existing work on a range of plant substrates (including okra fruit, orchid root, qunce seed, grapes, winery waste, and olive processing waste) as sources of hydrocolloids, highlights patterns of optimal routes for the extraction of such materials, irrespective of the initial plant source. These trends and their relation to the conposition and properties of the final products are discussed in terms of their potential to set-up standard protocols for the extraction of emulsifiers and thickeners from plant sources.

Mourtzinos, I., Prodromidis, P., Makris, D., Biliaderis, C. G., Moschakis, T.
Optimization of a green method for the recovery of natural colorants from onion solid wastes: application in a yogurt product

The valorization of onion (Allium cepa) wastes, a 450,000 tonnes/year waste in Europe, by a non-conventional method is presented. The outer dry layers of the onion bulb, which constitute the main waste of onion, is a source of valuable polyphenols such as flavonoids and anthocyanins. Polyphenols of onion leaves were extracted using eco-friendly solvents, such as water and glycerol. 2-hydroxypropyl-β-cyclodextrin was also used as a co-solvent for the augmentation of the extraction, as cyclodextrins (CD’s) are known to enhance the extraction of polyphenols in water by forming water-soluble inclusion complexes. The process was optimized by implementing a central composite (Box-Behnken) experimental design and response surface methodology (RSM), taking into consideration the following independent variables: glycerol concentration (Cgl), CD concentration (CCD) and temperature (T). The assessment of the extraction model was based on two responses: the total pigment yield (YTPm) and the antiradical activity (AAR). LC-MS analysis was also employed in order to identify biophenols and colourants of the obtained extracts. The main biophenols found were quercetin and quercetin derivatives and the main colorant was cyanidin 3-O-glucoside. The extract was also tested as a food colourant in a yogurt matrix. The chemical stability of the extract was determined by measuring the absorbance at 523 nm at different pH, time and thermal treatments. Changes in the colour of extract solutions and yogurt product were also monitored using a colorimeter. Onion leaf extract was found to be a stable colourant and can be proposed as an alternative to synthetic coloring agents.

Mantzouridou, F.
How the Design of Experiments (DOE) can reduce the systematic and random sources of variation during the extraction of labile bioactive constituent

Experimentation in academia and industry is widely used to obtain a better understanding of existing or new processes/products, but is very expensive. The Design of Experiments (DoE) approach makes available well established experimental designs to plan, conduct and analyze a systematic series of trials, in which the experimenter deliberately changes the input factors to observe the significant changes in the output responses. In this way, cause-and-effect relationships can be extracted in an efficient and cost effective way.A response of a process, for example, the extraction yield of a labile bioactive constituent, may be highly dependent, apart from the potential design factors, on nuisance factors classified as controllable, uncontrollable (but measurable) and noise factors that are all sources of experimental error. The confusing effects of the random error and the elimination of systematic bias can be greatly reduced by finding the appropriate settings of the experimental design and applying adequate statistical analysis. The main objective of this work is to discuss the principles of DOE - replication, blocking, randomization, analysis of covariance and process robustness studies - that are employed to identify and quantify the sources of errors and decrease their impact to a large extent. Characteristic DOE application examples to extract labile bioactive constituents from natural sources are presented to illustrate how DOE can ensure the validity and reliability of measurements.

Karageorgou, I., Grigorakis, S., Lalas, S., Makris, D. P.
Enhanced extraction of antioxidant polyphenols from Moringa oleifera Lam. leaves using a biomolecule-based low-transition temperature mixture

In this study, the extraction of polyphenols from Moringa oleifera leaves was investigated, using a biomolecule-based low-transition temperature mixture (LTTM), composed of glycerol and sodium acetate. The first step was to optimise LTTM concentration (CLTTM) and the molar ratio (Rmol) of glycerol-to-sodium acetate, by employing a Box-Behnken experimental design. Following this, a kinetic assay was undertaken to assess the effect of temperature. A maximum yield in total polyphenols (YTP = 53.80 mg gallic acid equivalents per g lyophilised material) was achieved using a C LTTM = 80% (w/v) and a Rmol = 6. The extraction followed a second-order model, requiring activation energy (Ea) of 55.71 kJ mol-1. Comparative evaluation using 80% ethanol showed that the LTTM used was significantly more efficient in extracting polyphenols and flavonoids, yielding extracts with higher reducing power. However, results concerning the antiradical activity were contradictory. Liquid chromatography-diode array-mass spectrometry examination of both the LTTM and the hydroalcoholic extracts revealed some qualitative differences, which might indicate selectivity of the LTTM towards relatively polar substances.

Nenadis, N., Stavra, K.
Effect of dehydrogenation or dihydrogenation of Cα-Cβ Bond of hydroxystilbenes to their hydrogen atom donating activity: A DFT approach

In the present study Density functional theory/Becke’s three-parameter hybrid functional combined with the Lee-Yang-Parr correlaOon functional (DFT/B3LYP) was used to examine the effect of Cα-Cβ bond nature (single, double, triple) in the backbone of hydroxystilbenes to their hydrogen atom transfer (HAT) ability. Tested compounds were trans-resveratrol and its derivatives, for which there are some scarce experimental findings, as well as piceatannol and related compounds. For this purpose bond dissociation enthalpy values were computed in the gas phase to study the effect of the structure free from any external influence and in liquid (benzene, water) phase. Benzene was used as a model of a lipid substrate. Simple phenol, which is usually non- reactive, was used as a reference. The double bond, resulting in molecular planarity, was predicted to favor the single hydrogen transfer. The triple bond, resulting in a linear backbone, was predicted to decrease the ease of such transfer. The saturation of the bond, resulting in loss of planarity, was expected to decrease more the activity. The impact of saturation was predicted to be too negative for trans-resveratrol. However, for piceatannol, an improvement of HAT efficiency was proposed only under stepwise HAT. Such a finding was related to the ease of allylic hydrogen atom donation after the formation of the o-quinone.

Çekiç, S. D., Uzunboy, S., Apak, R.
Development of novel DNA-CUPRAC colorimetric probe for determination of hydroxyl radical damage and related antioxidant activity

An unbalance between reactive oxygen species and antioxidants in favour of oxidants may cause health issues. In the study DNA was used as probe material to measure oxidative damage caused by hydroxyl radical (•OH) and potential protective effects of certain water soluble antioxidants. •OH was produced by Fenton method and a modified colorimetric CUPRAC method was developed. The absorbance difference originated from the fact DNA degradation products but not the original DNA was responsive to the CUPRAC reagent.

Kogia F., Andronikopoulos K., Sapalidou G., Angelidis P., Angelidis G.
Using least squares method for minimizing the total energy value measurements error for olive oil and alcoholic beverages with bomb calorimeter

The scope of this paper is to investigate new ways of receiving data for several drinks, so as to be possible to apply the Least Squares Method (LSM) to the measurements. Using LSM in a sufficient number of measurements it is possible to take results with high accuracy. It is found that the ways for taking the measurements, with the appropriate amounts of substrates, give satisfying results and that using LSM it is possible to find the measured values with a measurement error less than 1%.

Ozer, H., Oktay, Basegmez, H. I., Whitaker, T. B., Slate, A. B.
Uncertainty associated with sampling and effect of sampling plan in aflatoxin analysis of dried figs

Aflatoxin test procedure is a multi-stage process and generally consists of three steps; sampling, sample preparation and analytical steps. Because of the uncertainty associated with each step, the true aflatoxin concentration of a bulk dried fig lot can’t be determined with 100% certainty. The sources of error in the aflatoxin test procedure should be determined so that the errors can be effectively reduced.
Studies were developed to measure the variability and distribution among replicated sample aflatoxin test results taken from the same aflatoxin- contaminated lot of dried figs so that a model could be developed to evaluate the risk of misclassifying lots of aflatoxin sampling plan designs for dried figs.

Page 253 of 977 Results 2521 - 2530 of 9762