Kefir; is a fermented milk product which is produced by granules containing a wide variety of microorganisms such as lactic acid bacteria, acetic acid bacteria and yeasts. It is traditionally consumed in many countries. It has been shown in many studies that the polysaccharide structure surrounding the granules which is composed mainly of kefiran molecule has antimicrobial effect against various pathogens as well as many health promoting effects. In this study, 24 h fermented kefir was used with two types of kefir granules for production of kefiran extract. One of them is being sold commercially and the other was collected from private households in a different region of Turkey. Kefiran extraction was carried out from matured kefir granules using three different temperatures, 80°C, 90°C and 100°C. Also, the protein contents of the extracted solutions were determined by Bradford method. Protein content of the extract solutions obtained were measured as 0.001 g/ml. The antibacterial effect of 0.05, 0.1, 1 and 2 mg of this extract against several plant pathogenic bacterial strains belonging to genus Pseudomonas, Xanthomonas, Erwinia ve Clavibacter was investigated in vitro for the first time. For this purpose, two methods, disc diffusion method and spreading method were used. The AN and SD kefir supernatants used as the positive controls in the experiments showed an average of 13-17 mm and 10-14 mm inhibition zones on the isolates, respectively, but the antibacterial effect of kefiran extracts was not observed.

During conventional fermentation of milk into yogurt and kefir, changes of antioxidant capacities (DPPH radical scavenging, ferrous chelating, reducing power, hydrogen peroxide/ H2O2 scavenging activity) and total phenolic content were investigated. Both products showed greater phenolic content, DPPH radical scavenging, and reducing power activities than was the case of their unfermented milk forms. But they were unable to scavenge H2O2. Chelating ability of milk increased by yogurt fermentation but decreased by kefir fermentation. In general, antioxidative capacity of milk improved throughout conventional yogurt and kefir fermentations and ripening periods (except chelating ability for kefir and H2O2 scavenging). This study is valuable since it evaluates the antioxidant power of yogurt and kefir produced by traditional fermentation with 5 different antioxidative approaches. In face of rapidly rising consumer demand for safe, healthy, functional but natural foods, revealed results might strengthen importance of conventional fermentation process and highlight the antioxidative contributions of mentioned products

The fermentation is ended with pH 4.6 values in industrial production of kefir. In this study, the incubation temperature, the incubation time and inoculums of culture were chose as variable parameters of kefir. In conventional control systems, the value of pH can be found by trial method. In these systems, if the number of input parameters is greater, the method of trial and error creates a system dependent on the person as well as troublesome. Fuzzy logic can be used in such cases. Modeling studies with this fuzzy logic control are examined in two portions. The first part consists of fuzzy rules and membership functions, while the second part consists of clarify. Kefir incubation temperature between 20 and 25°C, the incubation period between 18 to 22 hours and the inoculum ratio of culture between 1-5% are selected for optimum production conditions. Three separate fuzzy sets (triangular membership function) are used to blur the incubation temperature, the incubation time and the inoculum ratio of culture. Because the membership function numbers belonging to the the input parameters are 3 units, 3x3x3=27 line rule is obtained by multiplying these numbers. The table of fuzzy rules was obtained using the method of Mamdani. The membership function values were determined by the method of average weight using three trapezoidal area of membership functions created for clarification. The success of the system will be found, comparing the numerical values obtained with pH values that should be. Eventually, to achieve the desired pH value of 4.6 in the production of kefir, with the using of fuzzy logic, the workload of people will be decreased and the productivity of business can be increased. In this case, it can be provided savings in both cost and time.

Son yıllarda keçi sütü ile üretilen ürünlere talep artmaktadır. Buna karşın, keçi sütünün inek sütüne kıyasla bileşen ve lezzet farklılıkları keçi sütü ile üretilen ürünlerin özelliklerinde önemli farklılıklara sebep olabilmekte ve ürünün kabul edilebilirliğini etkilemektedir. Bu çalışmada, keçi sütü ile üretilen kefirin antioksidan kapasitesinin, reolojik ve duyusal özelliklerinin inek sütüyle üretilen kefirin, söz konusu özellikleriyle kıyaslanması amaçlanmıştır. Bu çerçevede, inek sütü, keçi sütü ve 1:1 oranında inek ve keçi sütlerinin karışımıyla kefir üretilmiş, fiziko-kimyasal, reolojik ve duyusal analizleri gerçekleştirilmiştir. Bütün kefir örneklerinin reolojik özelliklerinin psödoplastik davranış gösterdiği ve üssel modele uygun olduğu belirlenmiştir. Keçi sütü ile üretilen kefir örneğinin ise görünür viskozite değerleri inek sütü ile üretilen kefirlere kıyasla düşük bulunmuştur. Keçi sütü kefirinin toplam antioksidan kapasitesinin de inek sütü kefirine kıyasla daha yüksek, renkte a ve b değerlerinin ise daha düşük olduğu tespit edilmiştir. Buna karşın, keçi sütü kefirinde, panelistler tarafından daha düşük kıvam ve kefir lezzeti algılanarak tüm izlenim açısından da daha düşük puanlar almıştır. Keçi sütüne %50 oranında inek sütü ilavesi ise, keçi sütünün yarattığı bu durumu etkilemiş ve duyusal özellikleri tamamıyla inek sütü kefirinin duyusal özelliklerine benzerlik göstermiştir. Dolayısıyla, inek sütü karışımı olumlu sonuçlar vermekle birlikte, sadece keçi sütünden kefir üretiminde daha iyi kıvam ve lezzet eldesi için daha ileri çalışmaların yapılması gerektiği sonucuna varılmıştır.

The aim of this study was to investigate the effect of kefir as a probiotic on the performance and health status of calves. Thirty Holstein female calves with 3-day-old were randomly allocated to three treatment groups: Control (without any probiotic), probiotic (a commercial probiotic mixture-3 g/d/calf bacteria-based and 2 g/d/calf yeast-based) and kefir (20 ml/d/calf). The calves were weaned at 56 days of age. The experiment was performed in 70 days. Treatment had no effect (P>0.05) on weaning and final body weight and starter intake. Although differences in weight gain were not significant (P>0.05), there were trend to increase by probiotic treatments during 0-14 days. Probiotic treatments tended to have a positive effect on the population of the fecal lactic acid bacteria at 14 days. The results of the study indicated that kefir as a natural probiotic in calf nutrition may be beneficial during the first weeks of life.

Kefir is a fermented product obtained from goat, sheep and cow milk as a result of lactic acid and ethyl alcohol fermentation. In this study, it was aimed to investigate the possibility of producing an alternative functional kefir product from almond milk. It was enriched with banana and honey to improve its sensory properties. Samples were stored at +4oC for 14 days. The pH and dry matter of samples containing almond milk were lower than those containing cow’s milk. Serum separation increased with the increase of almond milk ratio. The use of banana increased dry matter and viscosity, and decreased serum separation. pH, dry matter and viscosity decreased during storage. The highest L* value was observed in the control kefir produced from 100% cow’s milk, and the lowest in the samples containing honey and banana on the 1st day of storage. It can be said that the addition of honey increases the b* value and the addition of banana decreases the b* value. As almond milk ratio and storage time increased, bacteria counts decreased. The lactococci counts of the samples with banana added (except for the control) were higher than the others. In the samples with banana and honey, a higher increase in yeast count was observed during storage compared to plain kefir (control sample). It can be said that the use of almond milk reduces the general acceptability of kefir. Almond milk can be successfully used in kefir production as a substitute for cow’s milk, if sweeteners, fruit and thickeners are used.