Mustafa Tahsin Yilmaz

RP-HPLC–DAD analysis of phenolic compounds in pomace extracts from five grape cultivars: Evaluation of their antioxidant, antiradical and antifungal activities in orange and apple juices

Phenolic compounds, related to antioxidative and antifungal properties of ethanolic extracts from five commercial grape cultivars (three red and two white) grown in Turkey were determined. A reversed-phase high performance liquid chromatography (RP-HPLC) procedure was developed, and a total 18 different phenolic compounds were identified. Total phenolic contents of the extracts were determined using Folin-Ciocalteau method. Antioxidant activities of the extracts were evaluated by using DPPH radical scavenging and phosphomolybdenum methods. All extracts exhibited strong antioxidant and antiradical activity. Phenolic compounds and antioxidant activities of the extracts were variety dependent. Antifungal activities of the pomaces and extracts were screened by both in vitro agar-well diffusion assay and antifungal activity in apple and orange juices in situ using Zygosaccharomyces rouxii and Z. bailii. Antifungal activities revealed that the pomaces and extracts of Gamay and Kalecik karasi could be more effective antifungal agents than those of Emir, Narince and Okuzgozu grape cultivars.

Temperature Dependency of Steady, Dynamic, and Creep-Recovery Rheological Properties of Ice Cream Mix

In this study, effect of processing temperature (5, 15, 25, and 35xa0°C) on the steady, dynamic, and creep recovery rheological properties of the ice cream mix (ICM) was investigated. It was found that processing temperature significantly affected all rheological parameters of the ICM sample. The flow behavior of the ICM sample was fitted to the Ostwald de Waele model. The magnitude of storage modulus (G′) was higher than that of loss modulus (G″) indicating that ICM sample had weak gel-like structure. Modified Cox–Merz rules were satisfactorily applied to the ICM sample to observe relationship between steady and dynamic shear properties. Additionally, Burger model was used to characterize the viscoelastic properties of the ICM sample. The gel strength (S) value was also calculated, and a decrease was observed with the increase of temperature. Arrhenius equation satisfactorily described the temperature dependency of the rheological parameters such as apparent viscosity at 50xa0s−1 (η50), consistency coefficient (K), the instantaneous shear modulus of the Maxwell unit (G0), permanent deformation (J∞), and S values that may be predicted by using established equations depending on the temperature. The increase in processing temperature caused a decrease in resistance of the mixture subjected to the deformation, which is very important for production of high quality ice cream.

Steady, Dynamic, Creep, and Recovery Analysis of Ice Cream Mixes Added with Different Concentrations of Xanthan Gum

Different xanthan gum concentrations (0–0.8xa0%) were tested, and the rheological properties of ice cream mixes were characterized as linear viscoelastic solids. Ostwald de Waele was successfully used to fit the steady shear data of ice cream mixes exhibiting a pseudoplastic flow (R2u2009>u20090.982). The samples with xanthan gum were characterized as strong gel-like macromolecular dispersions with G′ much greater than G″ but without a cross-point in the whole range of frequency applied. Cox–Merz rule was not applicable to the ice cream mixes. Steady and dynamic rheology of the ice cream mixes changed with increasing xanthan gum concentration. Besides, the four-component Burger model consisted of the association in series of the Maxwell model and the Kelvin–Voigt model was used to characterize the viscoelasticity. It was also found that the final percentage recovery parameters; JSM, J∞, JKV, and %R (compliance of Maxwell spring and dashpot, Kelvin–Voigt element and R, respectively) of the ice cream mixes were dramatically changed by the xanthan gum concentration, increasing the internal structure parameters G0, G1, η0, and η1 (elastic moduli of Maxwell and Kelvin–Voigt springs and corresponding dashpot viscosities, respectively).

Effect of ultrasound treatment on steady and dynamic shear properties of glucomannan based salep dispersions: optimization of amplitude level, sonication time and temperature using response surface methodology.

The present study investigated effect of different amplitude levels (40, 70 and 100%), sonication temperatures (40, 50 and 60°C) and exposure times (3, 7 and 11 min) on steady shear properties; apparent viscosity (η), shear stress (σ), consistency coefficient (K), flow behavior index (n) and dynamic shear properties; storage modulus (G), loss modulus (G″), complex viscosity (η(∗)), complex modulus (G(∗)) and loss tangent (tan δ) values of glucomannan based salep solution (SS) and salep drink (SD) samples. In addition, the steady and dynamic shear properties were optimized using ridge analysis in terms of amplitude level, sonication temperature and exposure times levels. Increasing amplitude level and sonication time decreased considerably the η, σ, K, G, G″ and η* values of salep dispersions (SS and SD samples). However, sonication temperature did not have a remarkable effect on these properties.

A novel method to differentiate bovine and porcine gelatins in food products: NanoUPLC-ESI-Q-TOF-MS E based data independent acquisition technique to detect marker peptides in gelatin

We presented a novel nanoUPLC-MS(E) workflow method that has potential to identify origin of gelatin in some dairy products; yoghurt, cheese and ice cream. In this study, the method was performed in two steps. In the first step, gelatin was extracted from these products before the MS-sample preparation. In the second step, tryptic gelatin peptides were separated and analyzed with ultra-performance liquid chromatography and electrospray ionization quadrupole time-of-flight mass spectrometry (nanoUPLC-ESI-q-TOF-MS(E)). The novelty of this setup was that it functioned in a data independent acquisition mode and that alternate low and elevated collision energy was applied to acquire precursor and product ion information. This enabled accurate mass acquisition on the peptide level to identify the gelatin peptides. The marker peptides specific for porcine and bovine could be successfully detected in the gelatin added to the dairy products analyzed, revealing that the detection of marker peptides in the digested gelatin samples using nanoUPLC-ESI-q-TOF-MS(E) could be an effective method to differentiate porcine and bovine gelatin in the dairy products.

Effect of grape pomace extracts obtained from different grape varieties on microbial quality of beef patty.

UNLABELLEDnGrape pomace extracts were obtained from 5 different grape varieties grown in Turkey. The extracts were concentrated to obtain crude extracts; and incorporated into beef patties at 0% (Control), 1%, 2%, 5%, and 10% concentrations to test their antimicrobial effects in different storage periods (first, 12, 24, and 48 h). The numbers of microorganism were generally decreased by the extract concentration during the storage period. All the microorganisms tested were inhibited by the extract concentration of 10% in all the storage periods. Furthermore, the foodborne pathogens including Enterobacteriaceae and coliform bacteria, and the spoilage microorganisms including yeasts and moulds and lipolytic bacteria were also inhibited by 5% of Emir, Gamay, and Kalecik Karasi varieties in beef patties. Considering the results, the extracts of grape pomaces might be a good choice in the microbial shelf life extension of the food products as well as inhibiting the food pathogens as the case of beef patties.nnnPRACTICAL APPLICATIONnGrape pomace consists of seeds, skins, and stems, and an important by-product that is well known to be the rich source of phenolic compounds, both flavonoids and non-flavonoids. These substances have considerable beneficial effects on human health. The use of natural antimicrobial compounds, like plant extracts of herbs and spices for the preservation of foods has been very popular issue because of their antimicrobial activity. Therefore, grape pomace should be added into some food formulations to benefit from their protective effects. In this respect, this study reports the effect of addition of grape pomace extracts obtained from different grape varieties on microbial quality of beef patty. The results obtained in this study may be useful for food industry, which has recently tended to use natural antimicrobial sources in place of synthetic preservatives to prevent microbial spoilage.

Steady, dynamic and creep rheological analysis as a novel approach to detect honey adulteration by fructose and saccharose syrups: Correlations with HPLC-RID results

In this study, natural honey was adulterated with the addition of adulterants, namely saccharose and fructose syrups at a ratio of 0%, 10%, 20%, 30%, 40% and 50% by weight. Steady, dynamic and creep tests were conducted, revealing that the changes in the flow, viscoelastic and creep behavior of natural honey were clear and remarkable. Syrup addition decreased viscosity (η), storage (G) and loss modulus (G″) values of the control honey samples. Deformation represented by the compliance (J(t)) values was more prominent in the adulterated honey samples. In addition, HPLC-RID analysis was conducted to determine major sugar composition of the adulterated samples. Pearsons correlation test indicated that there were significant (P<0.05; 0.01) correlations between sugar composition and rheology parameters, η (viscosity), K″, K⁎ (intercepts for G″ and complex modulus (G⁎), respectively) and η0 (viscosity of Maxwell dashpot), suggesting that K, K″, K⁎ and η0 could be prominent indicators for presence of saccharose or fructose syrups added in natural honey within the studied concentration levels. These results suggested that use of steady, dynamic and creep analysis would be a novel and potential approach to detect honey adulteration by fructose and saccharose syrups.

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.

Response surface optimization of effects of some processing variables on carcinogenic/mutagenic heterocyclic aromatic amine (HAA) content in cooked patties.

A five-factor Central Composite Orthogonal Design was adopted to study simultaneous effects of some processing variables such as NaCl (0-2%), fat (10-30%), ascorbic acid (0-600 ppm), cooking temperature (150-230°C) and cooking time (5-15 min) on physicochemical properties and heterocyclic aromatic amine (HAA) contents of cooked beef patties. The HAAs analyzed were 2-amino-3-methylimidazo[4,5-f]-quinoline (IQ), 2-amino-3,8-dimethylimidazo[4,5-f]-quinoxaline (MeIQx), 2-amino-3,4-dimethylimidazo[4,5-f]-quinoline (MeIQ), 2-amino-3,4,8-trimethylimidazo[4,5-f]-quinoxaline (4,8-DiMeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP), as quantified by high-performance liquid chromatography with photo-diode array detection (HPLC-UV/DAD). It was found that ascorbic acid decreased; however, fat, cooking temperature and time levels increased the contents of IQ, MeIQx, MeIQ and PhIP. In addition, estimated ridge analysis was conducted to find values of the processing variables that maximize and minimize the five HAA contents, revealing that the results obtained would be useful for meat industry aiming to decrease HAA content in cooked meat products.

Effect of in situ exopolysaccharide production on physicochemical, rheological, sensory, and microstructural properties of the yogurt drink ayran: an optimization study based on fermentation kinetics.

Exopolysaccharide (EPS)-producing starter cultures are preferred for the manufacture of fermented milk products to improve rheological and technological properties. However, no clear correlation exists between EPS production and the rheological and technological properties of fermented milk products such as the yogurt drink ayran. In this study, 4 different strain conditions (EPS- and EPS+ Streptococcus thermophilus strains) were tested as a function of incubation temperature (32, 37, or 42°C) and time (2, 3, or 4 h) to determine the effect of culture type and in situ EPS production on physicochemical, rheological, sensory, and microstructural properties of ayran. Furthermore, we assessed the effect of fermentation conditions on amounts of EPS production by different EPS-producing strains during ayran production. A multifactorial design of response surface methodology was used to model linear, interaction, and quadratic effects of these variables on steady shear rheological properties of ayran samples and in situ EPS production levels. The physicochemical and microbiological characteristics of ayran samples altered depending on incubation conditions and strain selection. Steady shear tests showed that ayran samples inoculated with EPS+ strains exhibited pseudoplastic flow behavior. Production of ayran with EPS- strain (control sample) resulted in the lowest apparent viscosity values (η50), whereas those produced with the combination of 2 EPS+ strains yielded ayran with notably increased η50 values. We concluded that incubation time was the variable with the greatest effect on η50, consistency coefficient (K), and flow behavior index (n) values. In situ EPS production was also affected by these conditions during ayran fermentation in which strain-specific metabolism conditions were found to be the most important factor for EPS production. In addition, these findings correlated the amount of in situ EPS produced with the rheological properties of ayran. Scanning electron microscopy images of the samples showed differences in structural features, revealing a prominent network strand structure in the ayran samples inoculated with the admixture of 2 EPS-producing strains incubated at 37°C for 3 h. These results provide useful information for large-scale production of ayran by the dairy industry.