Fahrettin Göğüş

WATER ADSORPTION AND DRYING CHARACTERISTICS OF OKRA Hibiscus Esculentus L

ABSTRACT Moisture adsorption characteristics of okra were evaluated at 10, 20, 30° C. Isotherms were found to be of type III. Monolayer moisture contents were evaluated with GAB model. Drying was carried out at 60, 70, 80° C and drying data were analysed to obtain diffusivity values from the period of first felling drying rate. Effective diffusivity increased with increasing temperature. Calculated values of the effective diffusivity showed an Arrhenius type temperature dependence.

Determination of volatile nitrosamines in various meat products using comprehensive gas chromatography-nitrogen chemiluminescence detection.

An optimized method was developed for the extraction, pre-concentration and analysis of nitrosamines (NAs) in various meat products. Values of reproducibility, linearity, limit of detection (LOD) and limit of quantitation (LOQ) for six NA standards (N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodi-n-propylamine, N-nitrosopyrrolidine, N-nitrosopiperidine, N-nitrosodi-n-butylamine) were determined. The LODs using this method were between 1.66-3.86 and LOQs between 6.96-16.71 μg L(-1). The screening of four different types of meat samples (sausage, salami, sucuk and doner kebab) showed that all samples contained levels of various NAs, identified with high confidence using comprehensive gas chromatography (GCxGC) and a fast responding element specific nitrogen chemiluminescence detector (NCD). The sum of the six NAs were highest in the doner kebab samples, being between 0.51-16.63 μg kg(-1) and were lowest in the sausage samples at 0.45-2.93 μg kg(-1). The described method is simple, rapid, selective and sensitive.

Conversion of olive pomace oil to cocoa butter-like fat in a packed-bed enzyme reactor

Refined olive pomace oil (ROPO) was utilized as a source oil for production of cocoa butter-like fat. Immobilized sn-1,3 specific lipase catalyzed acidolysis of ROPO with palmitic (PA) and stearic (SA) acids was performed in a laboratory scale packed-bed reactor. Effect of reactor conditions on product formation was studied at various substrate mole ratios (ROPO:PA:SA; 1:1:1, 1:1:3, 1:3:3, 1:2:6), enzyme loads (10%, 20%, 40%), substrate flow rates (1.5, 4.5, 7.5, 15 ml/min) and solvent amounts (150, 400 ml). The highest yield (10.9% POP, 19.7% POS and 11.2% SOS) was obtained at 40% enzyme load, 1:2:6 substrate mole ratio, 45 degrees C, 7.5 ml/min substrate flow rate, 150 ml solvent and 3h reaction time. The melting profile and SFC of the product were comparable to those of CB. Polarized light microscope (PLM) images showed no drastic changes in polymorphic behavior between CB and product.

Hydroxymethyl Furfural Content of Concentrated Food Products

Thirty-six commercially and traditionally produced samples including seven fruit concentrates based on different fruit sources, seventeen boiled juices, and twelve tomato and paprika pastes were analysed for the determination of the hydroxymethyl furfural (HMF) and soluble solids content. The HMF concentrations of analysed food products showed a wide variability and were in a range between 0.4 and 3500 ppm. The HMF concentrations were found to be in a range of 0.4-4.5 ppm for fruit concentrates, 12.8-3500 ppm for boiled juices, and 0.4-18 ppm for tomato and paprika pastes. The soluble solids contents of food products ranged within the values of 13-66 0Brix for fruit concentrates, 64-79 0Brix for boiled juices, 29-54 0Brix for tomato pastes, and 55-61 0Brix for paprika paste. The HMF contents of the analysed concentrates showed significant differences (p<0.05). The highest HMF concentration was found for the boiled juice samples.

Determination of volatile nitrosamines in grilled lamb and vegetables using comprehensive gas chromatography – Nitrogen chemiluminescence detection

The grilling of meat may generate dangerous levels of mutagenic and carcinogenic nitrosamines (NAs). Meat and vegetable samples underwent a two-step solid-phase extraction before analysis by comprehensive gas chromatography with a nitrogen chemiluminescence detection system (GCxGC-NCD). The GCxGC-NCD method showed high selectivity, sensitivity and equimolarity in its response to six specific NAs. NA contamination of charcoal-grilled lamb at various stages of cooking and with various fat contents and also charcoal-grilled vegetables were investigated. The grilling of lamb on unready charcoal resulted in the formation of considerable quantities of NAs. Grilling lamb on properly prepared, ready charcoal resulted in an increase in total concentrations of six NAs from 0 to 4.51 μg kg(-1) over a period of 16 min. Increasing the fat content of the grilled lamb from 5% to 20% caused a modest increase in total concentrations of the six investigated NAs from 4.51 to 5.30 μg kg(-1).

Effect of Incorporation of Various Food By-products on Some Nutritional Properties of Rice-based Extruded Foods

Various food by-products were incorporated into rice grits and submitted to extrusion cooking to produce fortified extruded food products. The blends of various formulations of durum clear flour (8—20%), partially defatted hazelnut flour (PDHF) (5—15%), fruit waste blend (3—7%) and rice grits were extruded using single screw extruder. Response surface methodology was used to evaluate the effects of process variables, namely the feed moisture content (12—18%), barrel temperature (150—175 °C) and screw speed (200—280 rpm), and change in feed composition on total phenolic content, antioxidant activity, percent starch gelatinization and starch digestibility of the extrudates. Extrusion cooking process significantly increased the level of phenolic compounds and starch digestibility of extruded products. Increasing PDHF and fruit waste content caused increase in total phenolic content and antioxidant activity of the extruded samples, whereas percent starch gelatinization and digestibility values decreased. Moisture content and temperature significantly influenced the total phenolic content, antioxidant activity, percent starch gelatinization and starch digestibility values. In extruded samples, positive correlations were determined between antioxidant activity and total phenolic matter and percent starch gelatinization and the starch digestibility values, respectively.

Pre-treatment and extraction techniques for recovery of added value compounds from wastes throughout the agri-food chain

The enormous quantity of food wastes discarded annually forces a look into alternatives for this interesting feedstock. Thus, food bio-waste valorisation is one of the current imperatives of society. This review is the most comprehensive overview of currently existing technologies and processes in this field. It tackles classical and innovative physical, physico-chemical and chemical methods of food waste pre-treatment and extraction for the recovery of added value compounds and detection by modern technologies and is an outcome of the COST Action EUBIS, TD1203 Food Waste Valorisation for Sustainable Chemicals, Materials and Fuels.

Analysis of roasted and unroasted Pistacia terebinthus volatiles using direct thermal desorption-GCxGC-TOF/MS.

The objective of this study was to determine the effects of roasting time on volatile components of Pistacia terebinthus L., a fruit growing wild in Turkey. The whole fruit samples were pan roasted for 0, 5, 10, 15, 20 and 25min at 200°C. Volatile compounds were isolated and identified using the direct thermal desorption (DTD) method coupled with comprehensive gas chromatography - time of flight mass spectrometry (GCxGC-TOF/MS). The major components of the fresh hull of P. terebinthus were α-pinene (10.37%), limonene (8.93%), β-pinene (5.53%), 2-carene (4.47%) and γ-muurolene (4.29%). Eighty-three constituents were characterised from the volatiles of fresh whole P. terebinthus fruits obtained by direct thermal desorption with α-pinene (9.62%), limonene (5.54%), γ-cadinane (5.48%), β-pinene (5.46%), β-caryophyllene (5.24%) being the major constituents. The type and the number of constituents characterised were observed to change with differing roasting times. Limonene (5.56%), α-pinene (4.84%), 5-methylfurfural (4.78%), 5-hydroxymethylfurfural (5-HMF, 3.89%), dimethylmetoxyfuranone (3.67%) and 3-methyl-2(5H)furanone (3.12%) were identified as the major components among the 104 compounds characterised in the volatiles of P. terebinthus, roasted for 25min. In addition, volatiles of fully roasted P. terebinthus fruits contained furans and furanones (15.42%), pyridines (4.45%) and benzene derivatives (3.81%) as the major groups.

Genetic programming approach to predict a model acidolysis system

This paper models acidolysis of triolein and palmitic acid under the catalysis of immobilized sn-1,3 specific lipase. A gene-expression programming (GEP), which is an extension to genetic programming (GP)-based model was developed for the prediction of the concentration of major reaction products of this reaction (1-palmitoyl-2,3-oleoyl-glycerol (POO), 1,3-dipalmitoyl-2-oleoyl-glycerol (POP) and triolein (OOO). Substrate ratio (SR), reaction temperature (T) and reaction time (t) were used as input parameters. The predicted models were able to predict the progress of the reactions with a mean standard error (MSE) of less than 1.0 and R of 0.978. Explicit formulation of proposed GEP models was also presented. Considerable good performance was achieved in modelling acidolysis reaction by using GEP. The predictions of proposed GEP models were compared to those of neural network (NN) modelling, and strictly good agreement was observed between the two predictions. Statistics and scatter plots indicate that the new GEP formulations can be an alternative to experimental models.

CHOICE OF MODEL GEL SYSTEMS FOR THE FOOD DEHYDRATION STUDIES

ABSTRACT Various solid model gel systems were prepared by using different compositions of agar, starch and microcrystalline cellulose. Model gel systems were air dried and their drying characteristics were defined in some visual terms (change in shape, shrinkage, occurrence of browning reaction, cracking, cross sectional view). Agar showed a high tendency to the shrinkage. Addition of starch decreased the rate of the shrinkage, however caused the cracking in solid model systems. The mixtures of agar, starch and microcrystalline cellulose in proper ratios showed better drying characteristics with their full, non-cracking structures and similar shrinkage characteristics to those of vegetables.