Hasan Yetim

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.

Efficacy of various plant hydrosols as natural food sanitizers in reducing Escherichia coli O157:H7 and Salmonella Typhimurium on fresh cut carrots and apples

In the present study, inhibitory effects of the hydrosols of thyme, black cumin, sage, rosemary and bay leaf were investigated against Salmonella Typhimurium and Escherichia coli O157:H7 inoculated to apple and carrots (at the ratio of 5.81 and 5.81 log cfu/g for S. Typhimurium, and 5.90 and 5.70 log cfu/g for E. coli O157:H7 on to apple and carrot, respectively). After the inoculation of S. Typhimurium or E. coli O157:H7, shredded apple and carrot samples were washed with the hydrosols and sterile tap water (as control) for 0, 20, 40 and 60 min. While the sterile tap water was ineffective in reducing (P>0.05) S. Typhimurium and E. coli O157:H7, 20 min hydrosol treatment caused a significant (P<0.05) reduction compared to the control group. On the other hand, thyme and rosemary hydrosol treatments for 20 min produced a reduction of 1.42 and 1.33 log cfu/g respectively in the E. coli O157:H7 population on apples. Additional reductions were not always observed with increasing treatment time. Moreover, thyme hydrosol showed the highest antibacterial effect on both S. Typhimurium and E. coli O157:H7 counts. Inhibitory effect of thyme hydrosol on S. Typhimurium was higher than that for E. coli O157:H7. Bay leaf hydrosol treatments for 60 min reduced significantly (P<0.05) E. coli O157:H7 population on apple and carrot samples. In conclusion, it was shown that plant hydrosols, especially thyme hydrosol, could be used as a convenient sanitizing agent during the washing of fresh-cut fruits and vegetables.

The effects of nitrite on the survival of Clostridium sporogenes and the autoxidation properties of the Kavurma.

Kavurma is a traditional cooked (fried) meat product manufactured to preserve meat. Some bacterial genera, e.g., clostridia are important in kavurma. The objective of this study was to determine the influence of nitrite and the traditional cooking process on the survival and proliferation of Clostridium botulinum and the autoxidation properties of the kavurma. For this purpose, Clostridium sporogenes having similar characteristics to C. botulinum was used, and the samples were inoculated with 10(6) CFU/g C. sporogenes cells before the traditional cooking. The final products were packaged and stored under refrigeration for 6 months, and then the oxidation parameters (TBA, peroxide and free fatty acid values) and C. sporogenes counts of samples were determined. It was observed that C. sporogenes could survive during the traditional cooking process and storage. However, counts decreased during storage; for example, nitrite containing samples initially had 3.21logCFU/g C. sporogenes and 2.73logCFU/g at the end of storage. While nitrite had a slight antimicrobial effect on clostridia, it significantly reduced the TBA, peroxide and FFA values of the samples. In conclusion, it is suggested that addition of 100ppm of nitrite might be useful in kavurma processing because of its role in limiting oxidation as well as its antimicrobial effect.

Chemical composition and microbiological quality of the doner kebabs sold in Tekirdag market

Abstract The objective of this research was to determine chemical composition and hygienic quality of the doner kebabs sold in the Tekirdag market. In the chemical analysis; pH, moisture, protein, fat and salt contents as well as some minerals, Na, K, Zn, Fe and Cu, were determined. The samples were examined for aerobic plate count (APC), psychrotrophic bacteria, coliforms, mould and yeast, Clostridium perfringens and Salmonella spp. to observe the hygienic quality of the doner samples. The results of chemical analysis showed 5.86–6.03 pH, 61.28–51.67% moisture, 19.04–26.45% protein, 16.23–14.03% fat, 1.94–3.01% ash, and 1.28–2.08% salt values for the raw-cooked doner kebabs respectively. Chicken doner kebabs had higher pH, percentage protein and Cu content compared to beef doners while they had lower values for the percentage salt, Na, Zn, and Fe contents. The microbiological analysis showed 5.68–4.92 cfu/g APC, 5.14-3.48 cfu/g psychrotrophic bacteria, 4.79–2.88 cfu/g coliforms and 4.96–3.55 cfu/g mould and yeast for the raw-cooked doner kebab samples respectively. In general, chicken doner kebabs had higher APC, psychrotrophic bacteria and coliform counts than the beef doners. Although all of the raw kebabs contained presumptive Salmonella spp., 80% of the cooked chicken and 40% of the cooked beef samples also had these pathogens presumptively. Also, 80% of the raw doners, 60% of cooked chicken and 40% of beef samples contained C. perfringens . In conclusion, it could be proposed from the above data that the doner kebabs sold in Tekirdag market had very low hygienic quality; therefore, they would have a potential hazard for public health.

Combination of culture-dependent and culture-independent molecular methods for the determination of lactic microbiota in sucuk

In this study, the culture-dependent and culture-independent molecular methods were used for the identification of lactic acid bacteria (LAB) in sucuk a Turkish fermented dry sausage. On the one hand, the PCR-DGGE method targetting the V1 and V3 regions of 16S DNA was applied to DNA that was directly extracted from sucuk samples. On the other hand, rep-PCR fingerprinting was performed for the primary differentiation and grouping of the isolates, and the results were confirmed by sequencing of the 16S rDNA and 16S-23S rDNA intergenic spacer region. As a result of the PCR-DGGE analysis of all the samples, total 8 different lactic acid bacteria were identified, and Lactobacillus sakei, Lactobacillus curvatus and Weissella viridescens were the dominant microbiota among these bacteria. The culture-dependent approach indicated that the majority of the strains belonged to the Lactobacillus genera including Lb. sakei, Lactobacillus plantarum, Lb. curvatus, Lactobacillus brevis, Lactobacillus farciminis and Lactobacillus alimentarius. However, Leuconostoc and Weisella were also detected as minor genera. Again, Lactococcus piscium, Weissella halotolerans, Staphylococcus succinus and the comigrated Staphylococcus piscifermentans/Staphylococcus condimenti/Staphylococcus carnosus group were detected only with the culture-independent method while Lb. plantarum, Leuconostoc mesenteroides and Leuconostoc citreum were identified only by using the culture-dependent method. In the results, it was concluded that the combination of culture-dependent and culture-independent methods was necessary for reliable and detailed investigation of LAB communities in fermented food products.

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.

UNLABELLED Grape 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. PRACTICAL APPLICATION Grape 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.

Sensitivity of three pathogenic bacteria to Turkish cemen paste and its ingredients.

Pastirma is a dry cured meat product which is pasted with cemen. This paste is prepared from ground fenugreek, garlic and red hot pepper (RHPP). In this study, the cemen mix/paste and all its ingredients were tested for their inhibitory effects on Escherichia coli, Staphylococcus aureus and Yersinia enterocolitica. All samples had a varying inhibitory effect against all the bacteria tested during 4 days of storage. Complete cemen paste showed the strongest inhibitory effect on the three pathogens compared to ingredients alone. Fenugreek and RHPP had a bacteriostatic effect while the cemen paste and garlic had a bactericidal effect. S. aureus was the most sensitive bacterium while Y. enterocolitica was the most resistant. The results of this study confirmed the protective effect of cemen paste and garlic in food preservation especially against E. coli, S. aureus and Y. enterocolitica proving safety for public health. Hence it might be concluded that cemen paste is the first hurdle to prevent bacterial contamination, and a low pH (∼4.83) value would also add an additional barrier to secure safety of the product. Finally, it can be suggested that similar studies should be conducted on actual meat systems to confirm these findings.

Diversity and probiotic potentials of lactic acid bacteria isolated from gilaburu, a traditional Turkish fermented European cranberrybush (Viburnum opulus L.) fruit drink

The aim of the present study was to characterize lactic acid bacteria (LAB) strains isolated from traditional fermented gilaburu fruit juice and their probiotic potential. The LAB counts of the fermented gilaburu fruit juice were in the range of 3.92-8.30logcfu/g. Total of 332 isolates belonging to Lactobacillus and Leuconostoc species were characterized from traditional fermented gilaburu juice by genotypic methods. It was also determined that the major LAB strains belong to Lactobacillus plantarum (173 isolates), Lactobacillus casei (52 isolates) and Lactobacillus brevis (24 isolates), while Lactobacillus buchneri, Lactobacillus parabuchneri, Lactobacillus pantheris, Leuconostoc pseudomesenteroides and Lactobacillus harbinensis were the least in isolated LAB strains. In terms of the probiotic potentials, Lb. plantarum strains were able to grow at pH2.5, but 3 of Lb. casei strains, one of each Lb. brevis and Lb. buchneri strains could not grow at the same pH. All selected LAB stains were resistant to bile salt at ≤0.3% concentration. While all the LAB species grew at 15°C, two Lactobacillus hordei strains could also grow at 45°C. The highest cell hydrophobicity degrees were for Lb. casei (G20a) and Lb. plantarum (G19e) as 87.5 and 86.0%, respectively. Listeria monocytogenes and Bacillus cereus were the most sensitive bacteria against the selected LAB strains, while Escherichia coli and Staphylococcus aureus were the most resistant. Again all the isolated LAB species were resistant to three antibiotics; kanamycin, streptomycin and vancomycin. Characterization and probiotic potentials of the LAB isolated from fermented gilaburu (Viburnum opulus) juice were studied first time, and further research needs to be done on their behaviors in similar food formulations as a probiotic.

Quality characteristics of doner kebab made from sucuk dough which is a dry fermented Turkish sausage.

The objective of this study was to determine certain quality characteristics of the raw and cooked doner kebabs made from beef and sucuk dough which is a traditional fermented sausage. The doners were divided into two groups; traditional beef doners and sucuk dough groups, and all the samples were frozen and stored at (-30 ±1 °C) for 60 days to monitor their quality characteristics. All of the raw and cooked doner samples were subjected to chemical and microbiological analysis while only the cooked doners were evaluated organoleptically at 0th, 30th and 60th days of storage. In the chemical analysis; proximate composition (% moisture, % protein, % fat, and % ash), pH and TBA values were determined. The samples were examined for total aerobic plate count (APC), total anaerobes, psychrotrophic bacteria, total coliforms, total staphylococcus/micrococcus count, mould and yeast to observe the hygienic quality of the doner samples. The results of chemical analysis, in general, showed that sucuk doners had higher ash content, pH and TBA values, and all of the doners had higher APC, psychrotrophic bacteria and coliform counts at the beginning compared to 30th and 60th days of storage not only in the raw condition but also in cooked counterparts. The sensory evaluation results indicated that sucuk doners received favorable preferences, therefore, traditional sausage (sucuk) dough application in doner production could be possible without posing any acceptability problems in terms of quality factors compared to traditional beef doners.