Browsing by Author "Hesari, J."

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The Effect of Ultrasound Treatment on Microbial and Physicochemical Properties of Iranian Ultrafiltered Feta-Type Cheese
(Elsevier Science inc, 2018) Jalilzadeh, A.; Hesari, J.; Peighambardoust, S. H.; Javidipour, I
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 0157: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 0157: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.
The Effect of Whey Protein Concentrate Based Edible Coatings Containing Natamycin Orlysozyme-Xanthan Conjugate on Microbial Properties of Ultrafiltrated White Cheese
(Tarbiat Modares University, 2019) Jalilzadeh, A.; Hesari, J.; Peighambardoust, S.H.; Jodeiri, H.; Javidipour, I.
In this research, the effects of whey protein concentrate based edible coatings containing different concentrations of natamycin and lysozyme–xanthan gum conjugate were investigated. For this purpose, Escherichia coli O157:H7 (as an indicator for gram negative bacteria and also resistant to commercial pasteurization), Staphylococcus aureus (as an indicator of gram-positive bacteria), and Penicillium chrysogenum were inoculated to ultrafiltrated white cheese surface and the microbial properties of cheese samples were evaluated during 28 days storing.The results showed that all coated treatments significantly reduced the growth of Penicillium chrysogenum. Natamycin-containing coatings have been more effective in reducing the mold population than lysozyme-xanthan-containing coatings. Coated samples containing 600 ppm lysozyme-xanthan reduced E. coli O157: H7 growth 2.09 log compared to control samples.Also, the growth rates of Staphylococcus aureus were lower in all samples treated with lysozyme-xanthan than control sample. The lowest growth rate of Staphylococcus aureus was observed in the coated sample containing 600 ppm lysozyme-xanthan on 28th day, with a microbial population of 2.60 logarithms. Unlike other treatments, the growth rate of Staphylococcus aureus in the sample coated containing 600 ppm lysozyme-xanthan was descending over 28 days.The results of this study showed that whey protein based edible coating can be used as a carrier of natamycin and lysozyme-xanthan in optimal concentration, for increasing the microbial quality of UF cheese. © 2019 Tarbiat Modares University. All Rights Reserved.
Extension Shelf Life of Cheese: a Review
(Asian Network for Scientific Information, 2015) Jalilzadeh, A.; Tunçtürk, Y.; Hesari, J.
Cheese is a versatile nutrient-dense dairy product and susceptible to physical, chemical and biochemical spoilage. As a nutrient dense dairy product, cheese is a good source of protein, minerals particularly calcium and phosphorus which are essential components in most highly consumed foods. Therefore, extension shelf life of this dairy food is very important. This review focuses mainly on techniques used in extension shelf life of cheese. According to literatures, the main methods for cheese shelf life extension are addition of preservative, modified atmosphere (MAP), high pressure, active coating, edible coating and combination of them. Several studies have done on almost all categories of cheeses including soft fresh cheese, soft ripened cheese, surface mould ripened cheese, semi-soft cheese, hard cheese and very hard cheeses. © 2015 Academic Journals Inc.