M. Zeki Durak

An evaluation of Fourier transforms infrared spectroscopy method for the classification and discrimination of bovine, porcine and fish gelatins.

The objective of this research was to develop a rapid spectroscopic technique as an alternative method for the differentiation and authentication of gelatin sources in food products by using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra combined with chemometrics. Clear discrimination and classification of all the studied gelatin sources (bovine, porcine, and fish) were achieved by hierarchical cluster and principle component analysis (PCA). Amide-I (1700-1600 cm(-1)) and Amide-II (1565-1520 cm(-1)) spectral bands were used in a chemometric method. Moreover, ATR-FTIR spectral data successfully discriminated pure bovine gelatin from mixture of bovine and porcine gelatins, which is very important for the food industry. The method that we adopted could be beneficial for rapid, simple and economic determination of both gelatin presence and its origin from food products such as yogurt, ice cream, milk dessert or other gelatin containing products such as pharmaceuticals and cosmetics.

Development of a fermented ice-cream as influenced by in situ exopolysaccharide production: Rheological, molecular, microstructural and sensory characterization

This study aimed to investigate the role of in situ exopolysaccharide (EPS) production by EPS(+)Streptococcus thermophilus strains on physicochemical, rheological, molecular, microstructural and sensory properties of ice cream in order to develop a fermented and consequently functional ice-cream in which no stabilizers would be required in ice-cream production. For this purpose, the effect of EPS producing strains (control, strain 1, strain 2 and mixture) and fermentation conditions (fermentation temperature; 32, 37 and 42 °C and time; 2, 3 and 4h) on pH, S. thermophilus count, EPS amount, consistency coefficient (K), and apparent viscosity (η50) were investigated and optimized using single and multiple response optimization tools of response surface methodology. Optimization analyses indicated that functional ice-cream should be fermented with strain 1 or strain mixture at 40-42 °C for 4h in order to produce the most viscous ice-cream with maximum EPS content. Optimization analysis results also revealed that strain specific conditions appeared to be more effective factor on in situ EPS production amount, K and η50 parameters than did fermentation temperature and time. The rheological analysis of the ice-cream produced by EPS(+) strains revealed its high viscous and pseudoplastic non-Newtonian fluid behavior, which demonstrates potential of S. thermophilus EPS as thickening and gelling agent in dairy industry. FTIR analysis proved that the EPS in ice-cream corresponded to a typical EPS, as revealed by the presence of carboxyl, hydroxyl and amide groups with additional α-glycosidic linkages. SEM studies demonstrated that it had a web-like compact microstructure with pores in ice-cream, revealing its application possibility in dairy products to improve their rheological properties.

Production and characterization of a new biodegradable fenugreek seed gum based active nanocomposite film reinforced with nanoclays

In the present work, fenugreek seed gum (FSG)/clay nanocomposite films were prepared with nanoclays (Na+ montmorillonite [MMT], halloysite [HNT] and Nanomer® I.44 P [NM]) at different amounts (0, 2.5, 5.0 and 7.5g clay/100g FSG) by solution casting method and characterized. Increasing amount of nanoclay significantly (P<0.05) improved oxygen barrier and thermal properties of the biodegradable films. Agar diffusion tests revealed that FSG based nanocomposite films exhibited strong antimicrobial properties against foodborne pathogens namely Listeria monocytogenes, Escherichia coli O157:H7, Staphylococcus aureus and Bacillus cereus independently of clay type and concentration. In the case of mechanical properties, nanoclay incorporation up to 5% provided higher (P<0.05) tensile strength (TS) properties while elongation at break (EB) values of the films significantly (P<0.05) decreased in the presence of clay in the film matrix. SEM micrographs showed that especially lower levels (up to 5%) of nanoclay reinforcements provided a homogeneous and smooth film structure. In conclusion, FSG based nanocomposite films reinforced with nanoclays up to 5% showed a precious potential to be used in antimicrobial food packaging applications.

Ion Chromatographic Determination of Free Cyanide in Different Classes of Bottled Natural Mineral Water Consumed in Turkey

An ion chromatographic method for the quantitative determination of free cyanide in bottled natural mineral waters were measured in terms of selectivity, linearity, the limit of detection, limit of quantification, repeatability, precision, and accuracy. Chromatographic separation of free cyanide ions was accomplished with an anion-exchange column and detected by pulsed amperometric detection with a silver working electrode. The method was found to be selective, linear (r2 = 0.999) at a concentration range of 0.5 to 134 μg L−1, precise, and accurate. Recovery values of free cyanide in all classes of natural mineral water varied from 65.9 ± 1.6 to 95.2 ± 0.7 at different spiking levels (5–70 μg L−1). Parameters (total dissolved solids, mineral interferences, and added sodium hydroxide) affecting the recovery values were studied in this project. The limit of detection and limit of quantification were found to be 0.295 and 0.983 μg L−1, respectively. The proposed method was applied to 27 different brands of commercially available bottled natural mineral water products sold in Turkish markets. These natural mineral waters were classified as: (i) very low mineral concentration, (ii) low mineral concentration, (iii) intermediate mineral concentration, and (iv) high mineral concentration based on their total dissolved solids contents according to European Union Directive (Directive 80/777/EEC). Levels of free cyanide residues in the samples ranged from > limit of detection to 6.12 μg L−1. The highest average concentration of free cyanide residues was found in the class of “high mineral concentration waters.” However, the determined free cyanide values in all of the tested natural mineral water samples were found to be within the limits of European Union legislation.

Essential Oil Compositions and Bioactivities of Thymus revolutus and Cyclotrichium origanifolium

Abstract Thymus revolutus Celak (Lamiaceae) is an endemic species in Turkey. Cyclotrichium origanifolium (Labill.) Manden & Scheng (Lamiaceae) has been widely used as a flavoring agent in soups and salads, and herbal tea in Turkey. The essential oil (EO) components, antioxidant and antimicrobial activities of the extracts and EOs of T. revolutus and C. origanifolium were examined. The EO compositions were analyzed by GC-MS. Total phenolic contents, flavanols, flavonols and antioxidant activities of the extracts were determined by spectrophotometer. Antimicrobial activity was investigated against 15 microorganisms by agar diffusion method. Carvacrol, thymol, p-cimene and borneol were predominantly found in T. revolutus EO. The C. origanifolium EO contained bicyclo[3.1.l]hepten-3-one, 2,6,6-trimethyl-,(l.α, 2.β, 5.α), pulegone and 2- cylohexen-1-ol, 1-methyl-4-(1-methylethyl),-cis as main constituents. The levels of total phenolic contents, flavanols, and flavonols of T. revolutus and C. origanifolium extracts were 38.68±2.5 and 78.57±0.6 mg gallic acid equivalent/g; 2250.06±328.0 and 610.84±13.3 mg catechin equivalent/100 g; and 1287.35±91.1 and 2712.36±20.9 mg rutin equivalent/100 g, respectively. Antioxidant activities of T. revolutus and C. origanifolium were 48.91±0.2 % and 74.86±0.3 % at 0.1 mg/mL concentration, respectively in the DPPH assay. C. origanifolium EO sat 2 % and 1 % concentrations showed antibacterial activity against tested Gram (+) bacteria but not Mycobacterium smegmatis. Both of the EOs had no inhibitory effects at 0.2 and 0.5 % concentrationson on the 15 tested microorganisms. Gram (+) bacteria found to be more sensitive to the EOs and extracts than Gram (-) bacteria in this study. The EOs and the extracts of T. revolutus and C. origanifolium could be used as natural products in many areas such as food, pharmaceutical, alternative medicine and natural therapy.

Biodiversity and technological properties of yeasts from Turkish sourdough

In this study, yeasts were isolated and characterized from twelve traditional sourdough samples which belongs to Black Sea and Aegean regions of Turkey. Twenty six yeast species were isolated and identified by both 26S rDNA sequencing and FTIR spectroscopy. Saccharomyces cerevisiae (50%), Torulaspora delbrueckii (40%) and Kluyveromyces marxianus (10%) were found in 12 Turkish traditional sourdough samples. S. cerevisiae was found to be the most dominant species in Aegean region while T. delbrueckii was the most frequently isolated species in Black Sea region. Some technological properties of isolated yeast species such as acidity development, resistance to NaCI and potassium sorbate, and yeast effect on bread quality were investigated. Breads were prepared by S. cerevisiae TGM38 strain demonstrated the highest bread volume compared the other yeasts used in the study. This study showed the yeast diversity and technological properties of traditional Turkish sourdough breads fermented by chosen yeast species.