Bülent Ergönül

Fatty Acid Compositions of Six Wild Edible Mushroom Species

The fatty acids of six wild edible mushroom species (Boletus reticulatus, Flammulina velutipes var. velutipes, Lactarius salmonicolor, Pleurotus ostreatus, Polyporus squamosus, and Russula anthracina) collected from different regions from Anatolia were determined. The fatty acids were identified and quantified by gas chromatography and studied using fruit bodies. Fatty acid composition varied among species. The dominant fatty acid in fruit bodies of all mushrooms was cis-linoleic acid (18 : 2). Percentage of cis-linoleic acid in species varied from 22.39% to 65.29%. The other major fatty acids were, respectively, cis-oleic, palmitic, and stearic acids. Fatty acids analysis of the mushrooms showed that the unsaturated fatty acids were at higher concentrations than saturated fatty acids.

Immobilization of amyloglucosidase onto macroporous cryogels for continuous glucose production from starch

Poly(methyl methacrylate-glycidyl methacrylate) [Poly(MMA-GMA)] cryogels were synthesized using monomers of methylmethacrylic acid and epoxy group bearing GMA via radical cryopolymerization technique. Synthesized cryogels were used for the immobilization of amyloglucosidase to the cryogel surface using epoxy chemistry. Characterizations of the free and immobilized amyloglucosidase were carried out by comparing the optimum and kinetic parameters of enzymes. For this, pH and temperature profiles of free and immobilized preparation were studied and, it was found that, optimum pH of enzyme was not change upon immobilization (pH 5.0), while optimum temperature of the enzyme shifted 10 °C to warmer region after immobilization (optimum temperatures for free and immobilized enzyme were 55 and 65 °C, respectively). Kinetic parameters of free and immobilized enzyme were also investigated and Km values of free and immobilized amyloglucosidase were found to be 2.743 and 0.865 mg/mL, respectively. Vmax of immobilized amyloglucosidase was found to be (0.496 µmol/min) about four times less than that of free enzyme (2.020 µmol/min). Storage and operational stabilities of immobilized amyloglucosidase were also studied and it was showed that immobilized preparation had much more stability than free preparation. In the present work, amyloglucosidase immobilized poly(MMA-GMA) cryogels were used for continuous glucose syrup production from starch for the first time. Efficiency of immobilized enzyme was investigated and released amount of glucose was found to be 2.54 mg/mL at the end of the 5 min of hydrolysis. The results indicate that the epoxy functionalized cryogels offer a good alternative for amyloglucosidase immobilization applications with increased operational and thermal stability, and reusability. Also, these cryogels can be used for immobilization of other industrially valuable enzymes beyond amyloglucosidase.

Changes in quality attributes of intermediate-moisture raisins during storage

The aim of this research was to determine the changes in chemical and microbiological qualities of ready-to-eat intermediate-moisture raisins during storage. Raisins were immersed into hot (98±1°C) glucose solutions (10% w/v and 20% w/v) containing 1% (w/v) potassium sorbate to inhibit mould and yeast growth. Raisins were kept in glucose solutions until the moisture content became 20%, 25% and 30%, respectively. The reconstituted raisins were then stored at ambient temperature (23±3°C) and 50–60% relative humidity for 8 months in polyethylene/polyamide (PE/PA) packaging material. The changes of moisture content, water activity, pH values, total titratable acidity, total sugar contents, Hunter L, a and b color values, total mesophylic aerobic bacteria counts, and mould and yeast counts were determined during storage at 2-month intervals. The results of chemical analysis showed that changes in the total titratable acidity, total mesophylic aerobic bacteria, and mould and yeast counts of the products were increased significantly (P<0.05). However, the pH values, total sugar contents, and Hunter L, a, and b color values were decreased during the storage period (P<0.05).

Effect of Starter Culture and Packaging on the Chemical, Microbiological and Sensory Quality of Turkish Soudjouck (Sucuk)

Lactobacillus plantarum, Micrococcus aurantiacus, and Pediococcus pentosaceus in different combinations and amounts were used for the production of fermented soudjouck. The effects of starter cultures on total aerobic bacteria, and selected chemical properties of samples were determined. Additionally, the effects of starter culture and packaging on the sensory characteristics of final product were studied. It was found that nitrite and sugar content of samples decreased during ripening, while protein and fat content relatively increased with drying. Mesophilic aerobic bacteria counts increased in the first days of ripening and then decreased, similar trend was also observed for the counts of all three starter cultures. Sensory results showed that reducing amount of starter culture negatively affected and incorporation of glucano delta lactone (GDL) into formula along with starter culture had an adverse effect on the sensory properties. It was demonstrated that vacuum packaging improved the sensory properties; therefore, it should be preferred over normal packaging.

Determination of the effects of refrigerated storage and packaging method on the instrumental textural attributes of fresh-cut carrot slices

In this research fresh-cut carrot slices were packaged by three different techniques (passive modified atmosphere packaging, modified atmosphere packaging and vacuum packaging), stored at 4±1 °C for 9 days and instrumental textural attributes (hardness and toughness) of carrot samples were determined at three-day intervals. As a result of the study, it was found that hardness values of the samples which were passive modified atmosphere packaged and vacuum packaged significantly increased during storage (P<0.05).

Instrumental Textural Properties of Mesir Paste Kept at Different Temperatures

Traditional mesir paste bar samples were kept at different temperatures (4 ± 1°C, 20 ± 1°C, or 30 ± 1°C) and their textural properties were determined by conducting instrumental texture profile analysis. Total sugar content of mesir was 85 g/100 g sample, whereas the inverted sugar amount was 79 g/100 g. Saccharose content of mesir was 10 g/100 g. It was determined that temperature significantly affected the textural attributes of mesir paste samples (P < 0.05). Hardness of mesir paste kept in a refrigerator was 2241 N, whereas it was 273 N and 8.24 N for the samples kept at ambient temperature and 30 ± 1°C, respectively.

Effect of holding period prior to storage on the chemical attributes of Starking Delicious apples during refrigerated storage

In this research, the effects of three different holding periods (6, 12 and 24 hours) prior to storage on the quality attributes of Starking Delicious apples were investigated during storage of 8 months at 0.5 ± 1.0 oC. Changes in weight loss, flesh firmness, pH values, soluble dry matter amount, titratable acidity values, ascorbic acid contents, and total and reducing sugar content were determined. According to the results, the holding period showed statistically significant changes in the quality attributes of the apples (p < 0.05).

Survival of Salmonella typhimurium NRRL E4463 in Sauerkraut during Fermentation

In this research, the survival characteristic of Salmonella typhimurium NRRL E4463 in sauerkraut during fermentation was investigated. Salmonella typhimurium strains were inoculated in sauerkraut, and counts were determined on the 0, 1st, 2nd, 4th, 6th and 7th days of the fermentation. It was observed that the initial count of Salmonella typhimurium was 6.61 log cfu/g on the inoculation day, and it declined to <1.0 log cfu/g on the 7th day of the fermentation. During this period, lactic acid bacteria counts of the Salmonella-inoculated sauerkraut were 5.41 log cfu/g and 7.43 log cfu/g on the 0 and 7th day of the fermentation, whereas these values were 1.36 log cfu/g and 6.57 log cfu/g for the control sample, respectively.

Instrumental textural properties of plain helva kept at different temperatures

Traditional plain helva samples were stored at different temperatures (4±1 °C, 22±2 °C or 35±1 °C) and their textural properties were determined by conducting texture profile analysis. Also the general chemical composition of the samples was determined. According to the data obtained, total sugar content of samples was 41.56 g/100 g, whereas average protein, water and fat amounts were 18.63 g/100 g, 0.29 g/100 g and 37.84 g/100 g, respectively. It was determined that storage at different temperatures significantly affected the instrumental textural attributes of plain helva samples (P<0.05). Hardness of plain helva kept at 4±1 °C was 4.33 N, whereas it was 4.26 N and 9.10 N for the samples kept at ambient temperature (22±2 °C) and 35±1 °C, respectively. Temperature also significantly affected the chewiness, gumminess and cohesiveness scores of the samples (P<0.05).

Several quality attributes of beef and turkey meat doner kebabs produced by traditional or continuous process

The chemical, microbiological and sensory properties of doners produced by traditional or continuous processes were investigated. The production method (traditional or continuous) did not affect microbiological quality (p < 0.05). Doners produced by traditional process had generally better sensory properties than those produced by continuous process. Continuous process produced turkey meat doners with lesser fat content (p < 0.05), higher moisture content (p < 0.05). Even though, doners produced by the traditional process were given higher ratings by the sensory panel than those produced by the continuous process, the difference might not have any practical importance. Given the higher production capacity, continuous process is expected to replace traditional process in the years to come.