The effect of ultrasound treatment on microbial and physicochemical properties of Iranian ultrafiltered feta-type cheese.

Pasteurization failures in the dairy industry have been reported in many previous studies. Hence, ultrasound, as a nonthermal alternative to pasteurization, has been studied in recent years. In this research, retentate of ultrafiltered milk was pasteurized, inoculated with Escherichia coli O157:H7, Staphylococcus aureus, Penicillium chrysogenum, or Clostridium sporogenes, and then treated with ultrasound for 20 min at frequencies of 20, 40, and 60 kHz and intensity of 80%. Microbial and physicochemical properties of the subsequently produced ultrafiltered white cheeses were investigated throughout 60 d of ripening. Sonication at 20, 40, and 60 kHz reduced counts of E. coli O157:H7, S. aureus, P. chrysogenum, and Cl. sporogenes by 4.08, 4.17, and 4.28 log; 1.10, 1.03, and 1.95 log; 1.11, 1.07, and 1.11 log; and 2.11, 2.03, and 2.17 log, respectively. Sonication improved the acidity of ripened cheese, and sonicated samples had lower pH values than control samples at the end of storage. Sonication did not affect fat in dry matter or the protein content of cheese during ripening, but it did accelerate lipolysis and proteolysis; the highest rates of lipolysis index (free fatty acid content) and proteolysis index (water-soluble nitrogen) were observed on d 60 of ripening for samples sonicated at 60 kHz. Sonication did not affect cohesiveness or springiness of cheese samples, but hardness and gumminess increased in the first 30 d and then decreased until 60 d of storage. Furthermore, ultrasound treatment improved organoleptic properties of the cheese. In terms of overall acceptance, samples sonicated at 60 kHz received the highest sensorial scores. Results showed that sonication can improve microbial, physicochemical, and sensorial properties of ultrafiltered white cheese.

Fatty acids, tocopherols, selenium and total carotene of pistachios (P. vera L.) from Diyarbakir (Southeastern Turkey) and walnuts (J. regia L.) from Erzincan (Eastern Turkey).

In this study, 14 well-adapted genotypes of pistachio (Pistachio vera L.) grown in Diyarbakir (Southeastern Turkey) and 15 walnut (Juglans regia L.) genotypes grown in Erzincan (Eastern Turkey) have been studied. Pistachio genotypes contained 8.16-9.33% palmitic acid, 0.54-0.68% palmitoleic acid, 2.35-4.21% stearic acid, 67.81-76.82% oleic acid, 9.42-18:32% linoleic acid, 0.27-0.38% linolenic acid and 0.19-0.33 % arachidic acid. The range of selenium, α-tocopherol, γ-tocopherol, δ-tocopherol, α-tocotrienoid, γ-tocotrienoid and total carotenoid of these promising genotypes were found to be between 11.44 and 190.71 ng/g, 1.36 and 26.93, 36.17 and 170, 0.45 and 2.61, 0.96 and 3.76, 2.33 and 37.72 and 1.01 and 4.93 mg/kg, respectively. Linoleic acid ranging from 43.19% to 53.16% was the most abundant fatty acid in 15 pomologically selected walnut genotypes, followed by oleic and linolenic acids (31.91% and 11.46%, respectively). Their selenium contents ranged between 7.25 and 57.67 ng/g. γ-Tocopherol was the predominant tocopherol in walnut genotypes. Pistachio and walnut genotypes with higher unsaturated fatty acids, tocopherols and selenium contents may be valuable for nutritional breeding efforts.

Effects of frozen storage and vacuum packaging on free fatty acid and volatile composition of Turkish Motal cheese.

Effects of vacuum packaging and frozen storage were studied on the formation of free fatty acids (FFAs), volatile compounds and microbial counts of Motal cheese samples stored for a period of 180 days. The FFA concentration of Motal cheese samples increased throughout the storage period of 180 days. However, the FFA contents of samples stored at -18 °C showed considerably lower values than those of the samples stored at 4 °C. Palmitic (C16:0) and oleic (C18:1) acids were the most abundant FFAs in all the treatments. The volatile compounds detected by headspace solid-phase microextraction (HS-SPME) profile of Motal cheese consisted of 16 esters, 10 acids, 6 ketones, 4 alcohols, 3 aldehydes, styrene, p-cresol and m-cresol. Results showed that storage at -18 °C can limit the excessive volatile compound formation. Samples stored at 4°C with vacuum packaging showed comparatively high concentration of esters, ketones and alcohols. Samples stored without vacuum packaging at 4°C showed 2-nonanone as the most abundant volatile compound toward the end of storage period. Storage at 4°C under vacuum packaging decreased the mold-yeast counts of samples. Frozen storage could be a suitable method for storing the Motal cheese.