Fatih Tornuk

Recovery potential of cold press byproducts obtained from the edible oil industry: physicochemical, bioactive, and antimicrobial properties.

Physicochemical, bioactive, and antimicrobial properties of different cold press edible oil byproducts (almond (AOB), walnut (WOB), pomegranate (POB), and grape (GOB)) were investigated. Oil, protein, and crude fiber content of the byproducts were found between 4.82 and 12.57%, between 9.38 and 49.05%, and between 5.87 and 45.83%, respectively. GOB had very high crude fiber content; therefore, it may have potential for use as a new dietary fiber source in the food industry. As GOB, POB, and WOB oils were rich in polyunsaturated fatty acids, AOB was rich in monounsaturated fatty acids. Oil byproducts were also found to be rich in dietary mineral contents, especially potassium, calcium, phosphorus, and magnesium. WOB had highest total phenolic (802 ppm), flavonoid (216 ppm), and total hydrolyzed tannin (2185 ppm) contents among the other byproducts. Volatile compounds of all the byproducts are mainly composed of terpenes in concentration of approximately 95%. Limonene was the dominant volatile compound in all of the byproducts. Almond and pomegranate byproduct extracts showed antibacterial activity depending on their concentration, whereas those of walnut and grape byproducts showed no antibacterial activity against any pathogenic bacteria tested. According to the results of the present study, walnut, almond, pomegranate, and grape seed oil byproducts possess valuable properties that can be taken into consideration for improvement of nutritional and functional properties of many food products.

Application of Predictive Inactivation Models to Evaluate Survival of Staphylococcus aureus in Fresh-Cut Apples Treated with Different Plant Hydrosols

In this study, inhibitory effects of bayleaf, rosemary, sage, and thyme hydrosols on the growth of Staphylococcus aureus inoculated on fresh-cut apples were investigated using several sigmoidal models (modified Gompertz, logistic, Richards, Stannard, and Whiting and Buchanan). In addition, these models were compared to describe the inactivation of S. aureus by fitting the experimental data using nonlinear models and various statistical parameters (the mean percentage error, the mean bias error, the root mean square error, the modeling efficiency, and chi-square parameters) as well as determination of coefficient (R2). The modified Gompertz, logistic, and Stannard models exhibited better fits than Richards and Whiting and Buchanan models regarding these statistical parameters. Rosemary and thyme hydrosols were found to be the most efficient sanitizers in reducing the S. aureus numbers. Results demonstrate that predictive models could be utilized for describing the inactivation or survival of S. aureus on fresh-cut apple with the effects of the treatments with plant hydrosols.

Application of Non-linear Models to Predict Inhibition Effects of Various Plant Hydrosols on Listeria monocytogenes Inoculated on Fresh-Cut Apples

In this study, we studied the effects of some plant hydrosols obtained from bay leaf, black cumin, rosemary, sage, and thyme in reducing Listeria monocytogenes on the surface of fresh-cut apple cubes. Adaptive neuro-fuzzy inference system (ANFIS), artificial neural network (ANN), and multiple linear regression (MLR) models were used for describing the behavior of L. monocytogenes against the hydrosol treatments. Approximately 1-1.5 log CFU/g decreases in L. monocytogenes counts were observed after individual hydrosol treatments for 20 min. By extending the treatment time to 60 min, thyme, sage, or rosemary hydrosols eliminated L. monocytogenes, whereas black cumin and bay leaf hydrosols did not lead to additional reductions. In addition to antibacterial measurements, the abilities of ANFIS, ANN, and MLR models were compared with respect to estimation of the survival of L. monocytogenes. The root mean square error, mean absolute error, and determination coefficient statistics were used as comparison criteria. The comparison results indicated that the ANFIS model performed the best for estimating the effects of the plant hydrosols on L. monocytogenes counts. The ANN model was also effective; the MLR model was found to be poor at estimating L. monocytogenes numbers.

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.

Molecular characterization of silver–stearate nanoparticles (AgStNPs): A hydrophobic and antimicrobial material against foodborne pathogens

In this study, silver-stearate nanoparticles (AgStNPs) have been produced from silver nitrate solutions by replacing the nitrate by stearate ions and then reducing by thermal treatment. AgStNPs were characterized by particle size, zeta-potential, ATR-FTIR, contact angle and SEM (scanning electron microscopy) analyses. The mean particle size and zeta potential of AgStNPs were determined to be 69.22±7.30nm and +8.02±0.88mV. ATR-FTIR analysis showed characteristic IR bands of stearate, revealing the two strong peaks at 2848 and 2915cm-1 associated to symmetric (νs(CH2)) and asymmetric (νas(CH2)) stretching vibrations of methylene groups, respectively. On the other hand, the scissoring and rocking modes of methylene group were observed at 1470 and 718cm-1, respectively. Nanomorphological characterization by SEM revealed a layered morphology of AgStNPs. Contact angle measurements demonstrated that a contact angle of water drop on glass coated with AgStNPs was found to be 108.76°, which proved the strong hydrophobic properties of AgStNPs. AgStNPs seemed to be very effective in inhibiting foodborne pathogens (Salmonella Typhimurium, Escherichia coli O157:H7, Staphylococcus aureus, Listeria monocytogenes and Candida albicans). The results suggest the use of AgStNPs as a coating material to reduce biofilm or biofouling formation in terms of achieving appropriate food contact surfaces and higher hygiene/easier sanitation due to their strong hydrophobic and antimicrobial properties.

Determination and Improvement of Microbial Safety of Wheat Sprouts with Chemical Sanitizers

In this study, total aerobic mesophilic bacteria (TAMB), total coliform (TC), yeasts and moulds (YM), and Escherichia coli, Salmonella, and Staphylococcus aureus counts of wheat seeds and sprouts germinated for 9 days under different relative humidity (RH) (90% and 95%) and temperatures (18 °C, 20 °C, and 22 °C) were determined. The disinfection capabilities of sodium hypochlorite (NaOCl) (100, 200, and 400 ppm) and hydrogen peroxide (H(2)O(2)) (3% and 6%) on wheat seeds/sprouts were also investigated. It has been found that native TAMB, TC, YM, and E. coli population significantly increased (p<0.05) with the germination; however, no Salmonella and S. aureus were detected on the seeds and/or sprouts. Again, increasing the temperature and RH resulted in a rapid proliferation of microorganisms. On the other hand, E. coli population could be completely eliminated by the treatment of different concentrations of NaOCl or H(2)O(2) before the germination of wheat seeds. Again, increasing the NaOCl and H(2)O(2) concentrations resulted in additional reductions of TAMB, TC, and YM population; and the highest reductions in sprouts were observed when the seed was soaked in 400 ppm NaOCl for 30 minutes followed by tap water wash and germination for 9 days. Population reduction of 1.46 log colony-forming unit (cfu)/g of TAMB, 1.97 log cfu/g of YM, and 0.84 log cfu/g of TC in sprouts was achieved when compared with the control. The chemical sanitization did not negatively affect the germination capability of the seeds. Therefore, soaking the seeds in 400 ppm of NaOCl for 30 minutes followed by a germination environment of 18 °C and 90% RH was found to be the most appropriate germination condition for wheat sprouts with reduced microbial population.

Effect of xanthan and locust bean gum synergistic interaction on characteristics of biodegradable edible film

The present study was aimed to use different combinations of xanthan (XG) and locust bean gum (LBG) in the biodegradable edible film preparation by benefitting from their synergistic interactions for the first time. Concentrations of LBG, XG and glycerol of the optimized film sample were found to be 89.6%, 10.4% and 20%, respectively. At the optimum point the WVP, TS, E% and EM values of film were found 0.22gmmh-1 m2kPa, 86.97MPa, 33.34% and 177.25MPa, respectively. The optimized film was characterized for its physical, thermal and structural behavior. The scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR) analyses exhibited miscibility and presence of interaction between polymers. In conclusion, XG and LBG interaction was used successfully to get biodegradable films and coatings with improved characteristics.

Development of LLDPE based active nanocomposite films with nanoclays impregnated with volatile compounds

In this study, a novel procedure was performed for grafting of nanoclays (montmorillonite (MMT) and halloysite (HNT)) with essential oil constituents (thymol (THY), eugenol (EUG) and carvacrol (CRV)) using Tween 80 as surfactant and then the nanoclay particles were incorporated into LLDPE pellets (5 wt%) to produce active nanocomposite films using a twin screw extruder. The resulting nanocomposite films were analyzed for antimicrobial and antioxidant capacity as well as thickness, mechanical, color, barrier, thermal properties and surface morphology and molecular composition. Release of the active compounds from the films at the refrigerated and room temperature conditions were also tested. The results showed that the films had strong in vitro antibacterial activity against pathogenic bacteria (Salmonella Typhimurium, Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus and Bacillus cereus) while their effect against lactic acid bacteria (Lactobacillus rhamnosus and Lb. casei) was limited. The lowest and highest DPPH scavenging ability levels were 65.59% and % 87.92, belonged to THY-MMT and EUG-MMT, respectively. Release of active compounds at 24 °C was much more rapid than at 4 °C. CRV-HNT and THY-HNT provided slower release than the other films. SEM results showed that nanoclays were uniformly dispersed in the polymer matrix with exceptional agglomerates. Incorporation of the active nanoclays significantly (P > 0.05) improved tensile strength and elongation of the films. The results confirmed that LLDPE based active nanocomposite films could be successfully produced due to its good interaction with MMT and HNT, activated with THY, EUG and CRV.

Application of plant hydrosols for decontamination of wheat, lentil and mung bean seeds prior to sprouting

It is a requirement for both minimally processed and ready-to-eat fruit and vegetable industry and consumers to decrease use of harmful chemical antimicrobial agents such as chlorinated compounds in fresh product sanitation since they have a number of negative health and environmental effects. In this study, washing treatments with summer savoury, bayleaf and thyme hydrosols that are by-products essential oils were assessed for decontamination of wheat, mung bean and lentil seeds contaminated with Salmonella Typhimurium and Staphylococcus aureus prior to sprout production. Initial levels of S. aureus on wheat, lentil and mung bean were 4.86, 4.24 and 4.23 log colony forming units/g, respectively. Hydrosol treatments reduced S. aureus numbers significantly (P<0.05) depending on treatment time while the pathogen was not detected on mung bean soaked in the thyme hydrosol for 40 min. Sensitivity of S. Typhimurium was higher than S. aureus and thyme hydrosol achieved elimination of Salmonella on all of the see...

Multiple response optimization of the effect of thyme essential oil against Listeria monocytogenes in ground meat at different times and temperatures

The presence of L. monocytogenes is unacceptable in ground beef; therefore, it should be inactivated/ decontaminated in such meat products. In this respect, there are a great number of studies focused on reduction of the number of L. monocytogenes with essential oil applications. The utilization from antimicrobial activity of essential oils and extracts of many plant species have recently become popular for many pharmaceutical and food processing applications (11). Essential oil treatment is one of the effective methods for elimination of L. monocytogenes from food products (40). In the literature, there are a number of references highlighting the inhibitory effect of Thymus vulgaris on L. monocytogenes growth (14, 33, 36). Response surface methodology (RSM) is a useful statistical tool, allowing to improve and optimize processing conditions by finding the experimental relationship between input and output variables that are considered in an experimental design (20). Using an RSM design of experiment, it is possible to determine the relationship between the response and the independent parameters; to develop firstor secondorder mathematical models of responses as a function of the parameters studied; to map a response surface over a particular region of interest and optimize the response, and to select operating conditions to achieve target specifications or customer requirements (6, 23, 32). Like RSM, predictive microbiological models are also widely used in the modeling of food processing to eliminate the complexity of reactions and heterogeneous structure of food products. Among the predictive models used, Baranyi is known to be capable of showing a good fit for growth curves of some pathogenic bacteria, such as Bacillus spp., Brochothrix thermospacta, Clostridium spp., Escherichia coli O157:H7, Staphylococcus spp., Yersinia enterocolitica and Salmonella Typhimurium as well as Listeria monocytogenes under different conditions (2, 4, 16, 38, 45). Multiple response optimization of the effect of thyme essential oil against Listeria monocytogenes in ground meat at different times and temperatures