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Öğe Characterization of nutty flavor in Cheddar cheese(Elsevier Science Inc, 2004) Avsar, YK; Karagul-Yuceer, Y; Drake, MA; Singh, TK; Yoon, Y; Cadwallader, KRThe objectives of this study were to determine the volatile components responsible for the sensory perception of nutty flavor in Cheddar cheese. Cheddar cheeses with and without nutty flavors were selected by descriptive sensory analysis. Volatile aroma components from Cheddar cheeses with and without nutty flavors were isolated and characterized using solvent extraction with high vacuum distillation, dynamic headspace analysis, gas chromatography-olfactometry, and gas chromatography-mass spectrometry. More than 50 aroma-active compounds were detected in Cheddar cheeses. Consistent differences were observed between nutty and not nutty Cheddar cheeses. Strecker aldehydes were detected in higher amounts in Cheddar cheeses with nutty flavors compared with Cheddar cheeses without nutty flavors. Strecker aldehydes, dimethyl sulfide, and propionic acid were evaluated in young and aged Cheddar cheese models for nutty flavor by descriptive sensory analysis. Dimethyl sulfide and propionic acid did not contribute to nutty flavor in Cheddar cheese. The addition of Strecker aldehydes to young (<4 mo old) Cheddar cheese models resulted in nutty/malty flavor perceived by sensory analysis. When Strecker aldehydes were incorporated into aged (>9 mo old) Cheddar cheese models, nutty flavor perception increased. Strecker aldehydes contribute to nutty flavor in aged Cheddar cheese.Öğe A comparative study on the milk yield and milk composition of two different goat genotypes under the climate of the eastern Mediterranean(Tubitak Scientific & Technological Research Council Turkey, 2004) Keskin, M; Avsar, YK; Biçer, O; Güler, MBMilk yields and milk compositions of 2 different goat breeds with high milk yields, the Damascus (Shami) goat and the German Fawn x Hair goat crossbred (B-1), were monitored during lactation in order to evaluate their performance under Eastern Mediterranean conditions as an alternative to the Hair goat which has a low milk yield and shorter lactation period. The milk yield was recorded by the ICAR A4 method at 28-day intervals throughout the 240 days of lactation. After weaning on the 60th day of lactation, milk samples were collected at 28-day intervals and were analysed for different milk components. The results showed that there was no significant difference between the milk yields and gross compositions of these 2 goat breeds (P > 0.05). The average milk yield, and total solids, protein, fat, lactose and ash contents were 347.6 +/- 19.05 and 316.8 +/- 35.61 1, 12.2 +/- 0.16 and 12.4 +/- 0.28 (%), 3.5 +/- 0.07 and 3.4 +/- 0.11 (%), 4.3 +/- 0.12 and 4.1 +/- 0.23 (%), 3.6 +/- 0.08 and 4.2 +/- 0.11 (%), and 0.77 +/- 0.02 and 0.72 +/- 0.03 (%), for the Damascus and the crossbred, respectively. It was concluded that the breeding of both the Damascus and the crossbred should be encouraged in the Mediterranean region of Turkey in order to increase goat milk production since both breeds had higher milk yields than that of the Hair goat as reported in the literature.Öğe Effects of flavorings, storage conditions, and storage time on survival of Staphylocloccus aureus in Surk cheese(Int Assoc Food Protection, 2005) Masatcioglu, TM; Avsar, YKThe objectives of this study were to determine the cumulative effects of flavorings (chili pepper, thyme, mint, cumin, nutmeg, allspice, clove, cinnamon, black pepper, salt, and hot red pepper paste), storage conditions, and storage time on the survival of Staphylococcus aureus in Surk cheese and to monitor the associated chemical changes. Surk cheese, a traditional Turkish cheese, was produced by heating diluted nonfat yogurt and adding flavorings to the resultant acid-heat card. The cheese was later inoculated with S. aureus, shaped conically, and stored aerobically for mold growth and anaerobically in olive oil for 30 days at room temperature. The moisture content of aerobically stored cheese decreased over time and led to increases in total solids, salt, salt-in-moisture, and ash content during ripening (P < 0.05). The presence or absence of the flavorings had no significant effect, whereas storage conditions and storage duration decreased the survival of S. aureus (P < 0.05).Öğe Factors affecting the adsorption of buchnericin LB, a bacteriocin produced by Lactocobacillus buchneri(Urban & Fischer Verlag, 2002) Yildirim, Z; Avsar, YK; Yildirim, MBuchnericin-LB adsorbs to gram-positive but not to gram-negative bacteria. The tested gram-positive bacteria were species of Lactobacillus, Pediococcus, Leuconostoc, Enterococcus, Lactococcus, Listeria, Bacillus, Staphylococcus; gram-negative bacteria belonged to the genera Salmonella, Escherichia, Yersinia and Pseudomonas. Buchnericin-LB adsorption depended on pH but not on time and temperature. Also some anions of salts and lipoteichoic acid reduced or inhibited its adsorption. Treatment of cells and cell walls of sensitive bacteria with detergents, organic solvents or enzymes did not affect subsequent binding of buchnericin-LB. Treatment with buchnericin-LB caused sensitive cells to lose high amounts of intracellular K+ ions and UV-absorbing materials and became more permeable to o-nitrophenol-beta-D-galactopyranoside. Buchnericin-LB (640-2560 AU/ml) decreased the colony forming units (99%) and absorbance values of Listeria monocytogenes and Bacillus cereus. These results indicate that the mode of action of buchnericin-LB is bactericidal and its lethal effect is very rapid.Öğe Identification and quantification of character aroma components in fresh Chevre-style goat cheese(Wiley, 2003) Whetstine, MEC; Karagul-Yuceer, Y; Avsar, YK; Drake, MAChevre-style goat cheeses were characterized by descriptive sensory analysis as exhibiting sweet dairy flavors as well as a characteristic waxy/animal flavor. Aroma-active compounds (> 80) with high intensities identified by gas chromatography/olfactometry and gas chromatography/mass spectrometry included 2,3-butanedione (buttery), 1-octen-3-one (mushroom), o-aminoacetophenone (grape), lactones (coconut, peach), octanoic acid (sour/waxy), as well as 4-methyl and 4-ethyl octanoic acids (waxy/animal). Subsequent sensory analysis with model cheese systems confirmed that 4-methyl and 4-ethyl octanoic acids were responsible for the characteristic waxy/animal flavor.Öğe Use of retentate powder in the production of white-brined cheese by the direct recombination system. 1. Effect of different protein levels an the ripening behaviour(A V A Agrarverlag, 2001) Avsar, YK; Yildirim, M; Yildirim, ZIn this study, a white-brined cheese with different protein content (similar to 12.5, 14.0, 15.5 or 17.0%) but the same total solids (similar to 40%) was produced by the direct recombination system, using retentate powder, skim-milk powder and anhydrous milk fat. For cheese-making, cheese milk composition was adjusted to the equivalent to that of cheese. During a 30 day of ripening period, changes in the gross composition, nitrogen fractions and ripening indices of cheese samples were monitored at 10 day intervals. It was found that there was no significant effect of the protein level on the final composition of the experimental cheese although a fluctuation in the composition of the cheese samples was observed during the early days of ripening. Results also showed that it was possible to produce a white-brined cheese with a defined composition. Owing to the limited syneresis and the use of milk powders, considerable amounts of whey protein nitrogen (0.17 to 0.26%) and lactose (1.6 to 5.9%) were retained in the experimental cheese at the end of the ripening. For this reason, whey proteins should be excluded in the calculation of ripening degree. In addition. increasing the protein content appeared to hinder the proteolysis.Öğe Use of retentate powder in the production of white-brined cheese by the direct recombination system. 2. Effect of different protein levels on the rheological properties(Volkswirtschaftlicher Verlag, 2002) Avsar, YK; Yildirim, Z; Yildirim, MIn this study, the effect of protein contents on the textural properties of white-brined cheese produced by the direct recombination system (DRS) using retentate powder was investigated. The total solids and fat content of cheese was kept same, but the samples differed in protein content (12.5, 14.0, 15.5 and 17.0%, respectively). A compression test was applied and elasticity modulus, yield stress and yield strain were obtained from force-time curves. Samples were analysed for a period of 30 d at 10 d intervals. Increasing the protein content up to a certain level (14.0%) increased the elasticity modulus and yield stress. However, beyond that level (i.e. 15.5 and 17.0%) no effect of additional protein was observed suggesting that after a critical level is reached the additional protein increased the viscous component of the cheese rather than the elastic one. Unlike the other parameters, the protein levels did not affect the yield strain since this parameter is closely related to pH and proteolysis. Yield stress and yield strain values decreased, and the cheese samples became considerably shorter during maturation as an indication of breakdown of the bonds holding the structure.
