Nurcan Koca

High-pressure processing of Turkish white cheese for microbial inactivation.

High-pressure processing (HPP) of Turkish white cheese and reduction of Listeria monocytogenes, total Enterobacteriaceae, total aerobic mesophilic bacteria, total molds and yeasts, total Lactococcus spp., and total Lactobacillus spp. were investigated. Cheese samples were produced from raw milk and pasteurized milk and were inoculated with L. monocytogenes after brining. Both inoculated (ca. 10(7) to 10(8) CFU/g) and noninoculated samples were subjected to HPP in a high-pressure food processor at 50 to 600 MPa for 5 and 10 min at 25 degrees C. Reductions in L. monocytogenes, total aerobic mesophilic bacteria, Lactococcus spp., and Lactobacillus spp. in both pasteurized- and raw-milk cheese samples and reductions in total molds and yeasts and total Enterobacteriaceae counts in raw-milk cheese samples increased with increased pressure (P < or = 0.05). The maximum reduction of the L. monocytogenes count, ca. 4.9 log CFU/g, was obtained at 600 MPa. Because of the highly inhibitory effect of pasteurization, the total molds and yeasts and total Enterobacteriaceae counts for the cheese samples produced from pasteurized milk were below the detection limit both before and after HPP. There was no significant difference in inactivation of L. monocytogenes, total aerobic mesophilic bacteria, Lactococcus spp., and Lactobacillus spp. under the same treatment conditions for the raw milk and pasteurized milk cheeses and for 5- and 10-min treatment times (P > 0.05). No significant change was detected in pH or water activity of the samples before and after HPP. Our findings suggest that HPP can be used effectively to reduce the microbial load in Turkish white cheese.

Effects of spray-drying conditions on the chemical, physical, and sensory properties of cheese powder

Dairy powders are produced to increase the shelf life of fresh dairy products and for use as flavoring agents. In this study, 24 cheese powders produced under 7 different conditions were used to investigate the effects of spray-drying parameters (e.g., inlet air temperature, atomization pressure, and outlet air temperature) on the quality of white cheese powder. Composition, color, physical properties, reconstitution, and sensory characteristics of white cheese powders were determined. The results revealed that the white cheese powders produced in this study had low moisture content ratios and water activity values. High outlet air temperatures caused browning and enhanced Maillard reactions. Additionally, high outlet air temperatures increased wettability and dispersibility and decreased the solubility of white cheese powders. Free fat content was positively correlated with inlet air temperature and negatively correlated with outlet air temperature and atomization pressure. Sensory analyses revealed that white cheese powder samples had acceptable sensory characteristics with the exception of the sample produced at an outlet air temperature of 100°C, which had high scores for scorched flavor and color and low scores for cheese flavor.

Investigating the effects of operating conditions on the exergetic performance of a pilot-scale spray-drying system

In this study, performance of a pilot scale spray drier was evaluated by exergy analysis method. Performance parameters were investigated for the components of the drying system and overall system. Furthermore, the effects of process conditions such as atomisation pressure, inlet and outlet drying air temperatures on the performance of the spray drier were analyzed. While the most effective system component was determined as heater, atomizer was the most important component with the highest improvement potential rate. Results showed that high inlet and low outlet air temperatures caused high effectiveness for overall system performance.

Effects of whey or maltodextrin addition during production on physical quality of white cheese powder during storage

There is an increasing demand for cheese as a food ingredient, especially as a flavoring agent. One of the most important cheese flavoring agents is cheese powder. To obtain an intense cheese flavor, ripened cheese is used as a raw material in cheese powder but this increases production costs. Moreover, use of natural cheese decreases the physical quality of powder because of its high fat content. In this study, we evaluated opportunities to use whey or maltodextrin for improving the physical quality of powders in production of white cheese powder. We produced cheese powders with 3 different formulations-control (CON), whey-added (WACP), and maltodextrin-added (MACP)-and determined the effects of formulation on cheese powder quality. Physical quality parameters such as color, densities, reconstitution properties, free fat content, particle morphology, and sensory characteristics were investigated. The different cheese powders were stored for 12 mo at 20°C and we evaluated the effect of storage on powder quality. Addition of maltodextrin to cheese powder formulations significantly improved their physical quality. The densities and reconstitution properties of cheese powder were increased and free fat content was decreased by use of maltodextrin. The MACP particles were spherical with a uniform distribution and larger particle sizes, whereas CON and WACP particles were wrinkled, irregular shaped with deep surface dents, and variable in size. Although caking was observed in scanning electron micrographs after 12 mo of storage, it was not detected by sensory panelists. The color of cheese powders changed very slowly during storage but browning was detected. The results of this study show that it is possible to use maltodextrin or whey in production of white cheese powder to reduce production costs and improve the physical quality of powders.

High-pressure effects on the microstructure, texture, and color of white-brined cheese.

UNLABELLED White-brined cheeses were subjected to high-pressure processing (HPP) at 50, 100, 200, and 400 MPa at 22 °C for 5 and 15 min and ripened in brine for 60 d. The effects of pressure treatment on the chemical, textural, microstructural, and color were determined. HPP did not affect moisture, protein, and fat contents of cheeses. Similar microstructures were obtained for unpressurized cheese and pressurized cheeses at 50 and 100 MPa, whereas a denser and continuous structure was obtained for pressurized cheeses at 200 and 400 MPa. These microstructural changes exhibited a good correlation with textural changes. The 200 and 400 MPa treatments resulted in significantly softer, less springy, less gummy, and less chewy cheese. Finally, marked differences were obtained in a* and b* values at higher pressure levels for longer pressure-holding time and were also supported by ΔE* values. The cheese became more greenish and yellowish with the increase in pressure level. PRACTICAL APPLICATION The quality of cheese is the very important to the consumers. This study documented the pressure-induced changes in selected quality attributes of semisoft and brine-salted cheese. The results can help the food processors to have knowledge of the process parameters resulting in quality changes and to identify optimal process parameters for preserving pressure-treated cheeses.

Energy and exergy analyses of spray drying of a fruit puree (cornelian cherry puree)

In this study, a fruit powder was produced from the mixture of cornelian cherry puree (CCP)/maltodextrin by spray drying. The performance of spray drying process and the drying system was evaluated by energy and exergy analyses. Experiments were carried out with an inlet drying air temperature range of 130–160°C, an outlet drying air temperature range of 65–85°C and CCP/maltodextrin ratio was chosen as 60/40, 50/50, and 40/60 (w/w). While the energetic and exergetic efficiencies for the drying process were calculated between 3.2–17.3% and 0.7–4.1%, the exergetic efficiencies of the spray dryer and overall system were found to vary between 27.0–39.1% and 26.7–32.9%, respectively. Results showed that high inlet and low outlet air temperatures caused high effectiveness for drying process. However, maltodextrin concentration of the feed did not have significant effects on the process performance.

Gıda Sanayisinde Ultraviyole Işığın Yüzey Uygulamaları

Gida sektorunde, isil islem uygulanamayan ya da isil islem uygulanmis ancak sonrasinda bulasma olmus gidalarin yuzey dekontaminasyonu her zaman onemini korumustur. Ultraviyole (UV) isik; isil islem alternatifi olarak yuzeylerde rahatlikla kullanilabilen umut verici mikrobiyal dekontaminasyon yontemidir. Son yillarda, dusuk yatirim maliyeti, kolay uygulanabilmesi ve pozitif tuketici imaji gibi cesitli avantajlari sebebiyle UV isin uygulamasi gida endustrisinde gittikce yayginlasmaktadir. Gidalarin ve gidayla temas eden ekipmanlarin yuzey dezenfeksiyonu ile ambalaj dekontaminasyonu basta olmak uzere cesitli yuzey uygulamalarinda kullanilabilmektedir. Bu amacla, hedefe yonelik olarak kesikli ya da surekli sistem calisan UV kabinleri dizayn edilmektedir. Bu sistemlerin kullaniminda, yuzey dezenfeksiyonunu etkileyen faktorlerin bilinmesi ve mikrobiyal inaktivasyon yanisira kalite degisimlerinin de goz onunde bulundurulmasi oldukca onemlidir. Bu derlemede, UV isik uygulamasinin inaktivasyon mekanizmasi ve kullanilan isik kaynaklari hakkinda genel bilgiler verilmekle birlikte, UV isigin gida ve gida ile temas eden ekipman yuzeyleri ile ambalajlarin yuzey uygulamalarinda kullanim olanaklari ve etkileri ile ilgili detayli bilgi verilmesi amaclanmistir. Ayrica, UV isigin yuzey uygulamalarindaki avantajlari, uygulamanin etkinligini sinirlandiran faktorler ile yasal duzenlemeler de ele alinmistir.

Isıl İşlem Görmüş İçme Sütlerinde (Pastörize, UHT ve Laktozsuz UHT Süt) Hidroksimetilfurfural İçeriğinin Belirlenmesi

Isil islem uygulamasi sirasinda gerceklesen Maillard reaksiyonlari (enzimatik olmayan esmerlesme) urun kalitesi acisindan onemlidir. Bu reaksiyonun ara urunlerinden biri olan hidroksimetilfurfural (HMF), uretim ve depolama asamasinda ozellikle sicakliga bagli olarak degisim gostermektedir. Bu arastirmada, piyasadaki farkli yag oranlarina sahip pastorize ve UHT sutlerin toplam HMF miktarlari belirlenmis ve ayrica laktozun hidrolize edilmesinin HMF degeri uzerine etkisi saptanmistir. Bunun yani sira, sutlerin bilesim ve renk degerleri de tespit edilmistir. Toplam HMF degerleri, pastorize sut orneklerinde 1.15-4.78 µmol/L, UHT sut orneklerinde 2.16-12.74 µmol/L, laktozsuz UHT sut orneklerinde ise 27.35-35.73 µmol/L araliginda tespit edilmistir. Her ne kadar isi artisi ile HMF degerlerinde artis tespit edilse de, bu degerler HMF iceren bircok gidaya gore oldukca dusuk bulunmustur. UHT sutlerin yag iceriginin artmasi ile HMF degerlerinde dusuk seviyelerde artis gozlenmesine karsin, en yuksek degerler laktozun hidrolize edildigi laktozsuz UHT sutlerde elde edilmistir. Ayrica, laktozsuz UHT sutlerin kirmizilik degeri daha yuksek bulunmustur.

KINETICS OF TOTAL PHENOLIC CONTENT AND TOTAL COLOR DIFFERENCE DURING LIQUID SMOKING OF KASHAR CHEESE

Since the late 1800s, smoking has been used for giving color, taste, and aroma to foods, as well as for developing new products. Due to health, technical, and economic reasons, one of the widely used smoking techniques preferred by manufacturers is smoking with liquid smoke. In this study, fresh Kashar cheese slices were smoked by immersion in liquid smoke at concentrations (10, 20, 30%), smoking temperatures (20, 30, 40°C) and smoking times (30, 60, 120, 180, 300 s). The appropriate equation and kinetic parameters were determined for the variation of total phenolic content and total color difference. A pseudo-first-order kinetic model was obtained, and activation energy values were calculated as 10.7 kJ/mol and 24.3 kJ/mol, respectively.