Exopolysaccharide influence on acid gel formation

K. Yoanidu1, P. Boyanova2*, P. Panayotov2

1Department Industrial Microbiology, The Stephan Angeloff Institute of Microbiology, Bulgarian Academy of Sciences, 26 Acad. G. Bonchev, 1113 Sofia,

2Department of milk and milk products, Faculty of Technology, University of Food Technologies, 26 Maritza, 4000 Plovdiv, Bulgaria

(Manuscript received 12 February 2017; accepted for publication 16 April 2017)

Abstract. Turbidimetric monitoring of milk coagulation was conducted in situ. Milk gel was produced by acidification with the use of three strains of starter culture. These strains were characterized by various acidification rate and exopolysaccharides (EPS) production. The concentrations of EPS affect mostly the pH of gel formation (5.53 – low EPS – producing strain; 5.33 – medium EPS – producing strain; 5.46 – high EPS – producing strain) whereas the time of gel formation depends on the various rate of acidification of all three strains.

Variability of individual coagulation ability and qualitative composition of milk from Kalofer Longhaired goats

G. Kalaydzhiev1*, A. Vuchkov2*, T. Angelova1, D. Yordanova1, V. Karabashev1, J. Krastanov1, D. Dimov2, N. Oblakov3, S. Laleva1, Y. Popova1

1Agricultural Institute, 6000 Stara Zagora, Bulgaria
2Departmet of Animal Science, Faculty of Agronomy, Agricultural University, 12 Mendeleev, 4000 Plovdiv, Bulgaria 3Freelance scientific advisor

Abstract. The growing scientific interest in the coagulation ability of milk in leading countries in Europe and in the world, is the premise for the research carried out by us in this direction. In this study 49 individual milk samples of goats from the autochthonous breed Kalofer Longhaired were examined for coagulation ability and qualitative composition of the milk. Analysis of individual coagulation ability was made in the dairy lab of Agricultural Institute, Stara Zagora through Computerized Renneting Metter – Polo Trade, Italy. The studied phenotypic parameters defining the dynamics of the qualitative composition of milk are with average values, respectively: fat – 4.15%, protein – 3.34%, dry non-fat substitutes (DNS) – 8.84%, lactose – 4.84% and pH – 6.62. The average values of exponents are rennet clotting time (RCT) – 11.47min, curd firming time (CR) – 0.86min, and curd firmness – 27.16 mm. Coagulation ability of the milk of Kalofer Longhaired goat have good technological properties for the production of traditionally identical milk products.


Monitoring of milk acid coagulation by rotational viscometer

P. Boyanova, P. Panayotov, B. Milenkov, H. Dinkov

Abstract. In the following work possibilities to monitor the acid coagulation dynamics by rotational viscometer are discussed. There is established suitable speed of rotation of the cylinder, in line with the delicate structure of the gel. The time to achieve the isoionic point in the acid coagulation of milk can be determined by changing the viscosity. The obtained results give grounds to assert that the viscometers cannot be used alone for the detailed monitoring of acid coagulation. Viscometers can be used as the reference method for monitoring changes of dynamic viscosity of milk during acid coagulation and determining the point of gelation. To establish the parameters of acid coagulation dynamics titratable acidity (°T), pH and lactic acid accumulation on milk (%) were followed.


Study on the level of generated vacuum in the teat cup milking chamber as a factor for assessing liner suitability

V. Vlashev, G. Dineva

Abstract. In the article is studied the impact of the generated vacuum in the teat cup milking chamber of the milking clusters for milking cows manufactured by the companies De Laval, Spaggiari and Gea Farm Technologies . New milking liners as well as ones with hours worked resources have been examined. The survey was conducted by a Device for Integrated Diagnostics of Milking Machines . The resulting data are presented in graphic and tabular form.


Behaviour of cows in milking parlour

I. Varlyakov, V. Radev, Т. Slavov, N. Grigorova

Abstract. Milking behaviour of 102 dairy, cows (Brown cattle breed – imported from Austria) was studied by computer monitoring system in 3 periods: Period 1(P1) – 60 days after the group formation, Period 2 (P2) – 120 days after P1 and Period 3 (P3) – 120 days after P2. An entrance order in the milking parlour was established, that is preserved over the lactation. Kendall coefficients ranged between 0.373–0.421 (P<0.001), increasing with time after forming the group. The entrance order for milking was mostly influenced by the stage of lactation (r=+0.330, P<0.001) and at the least extent – by the daily milk production (r=0.398, P<0.001). A preference towards the milking side was observed in more than half of cows (50.2%). Their share increase as followed: 40.5% P1, 42.1% P2, and 68.1% – P3. In a herd of 100 cows, three groups are formed with respect to the entrance order for milking: 16% that tended to enter first, 18-25% that are always the last, and the largest, ‘tolerant” group of 50-66%. Highly productive cows are never the majority among those that are first or last to enter for milking.


Study of milk composition in sheep of Pleven black head breed

D. Panayotov, T. Iliev, N. Naydenova, D. Pamukova, M. Simeonov

Abstract. The aim of the study was to investigate somatic cell count and milk composition from Pleven Black head breed of sheep. A total of 96 ewes on first lactation were used belonging to the flock of the village of Komarevo, Pleven district. The studied animals – daughters of six rams from 2 lines, were fed year round in a barn (November-March) and pasture period (April-October). A total of 384 individual milk samples were taken at four selection controls. The milk composition – fat, protein, casei, lactose, solids-non-fat and dry matter was established by Milko-Skan 104 (A/S Foss Elektric, Denmark). The total number of the somatic cells was established by an Ekoscope SCC automated system (Bulteh 2000, Stara Zagora, Bulgaria). The results of this investigation showed that the studied animals had very good milk quality indices. The milk of line 522 animals had significantly higher dry matter, solids-non-fat, fat, protein, casein and lactose content in comparison to those of line 32. For all studied milk indicators the daughters of ram No.33 in line 32 showed the highest average values whereas those of ram No.321 belonging to the same line had the lowest. The average somatic cell count of the milk in the studied animals was very low – 66 254 cells/ml. Minimum variation was established in respect to average SCC values of the milk in both lines but very large between the individual rams.


Identification of Mastitis Pathogens in Rabbit Milk by Near Infrared Spectroscopy and SIMCA Classification Method

S. Atanassova, D. Prakasam, S. Isloor, R.M.Vasu

Abstract. The purpose of this study was to investigate the potential of near infrared spectroscopy combined with multivariate analysis for determination of bacterial species, caused mastitis infection, based on NIR spectra of milk. Experimental mastitis was induced in 12 milking rabbits. The rabbits were infected with Staphylococcus aureus and E.coli bacteria, isolated from mastitis cows by injection of 0.5 ml of bacterial suspension with different concentration into the base of the teats. After the inoculation of bacterial strains into the teats, the infected rabbit milk was collected at different time intervals – 24, 48, 72, 96, 120 and 144 hours. Spectra of diluted milk were collected using a USB4000 visible-near-infrared spectrometer (OceanOptics, USA) over the wavelength range 450–1100nm using transmission through 10mm quvette. The instrument was first set up with healthy milk as reference. Spectra of 37 milk samples from rabbits, contaminated with Escherichia coli, and 28 milk samples from rabbits, contaminated with Staphylococcus aureus, were used in the investigation. Soft Independent Modeling of Class Analogy (SIMCA) was implemented to create models for discrimination of milk according to bacterial infection. SIMCA models correct classified from 81.08 to 100% of milk samples from rabbits, infected with Escherichia coli, and from 89.28 to 100% of samples from rabbits, infected with Staphylococcus aureus, depending on used spectral region and spectral data transformation. Models, based on spectral region from 456 to 960 nm allowed 100% correct identified all samples. The information of SIMCA models was used for investigation of spectral information, related to presence and action of Escherichia coli and Staphylococcus aureus bacteria in milk. The most important spectral region for detection of Escherichia coli infection was found to be 720 – 750nm, and for Staphylococcus aureus infection – from 920 to 960nm, respectively. The results demonstrated that near infrared spectroscopy in combination with multivariate chemometrics technique offers an alternative approach to traditional methods with large potentials for a rapid and reliable identification in microbiology and biodiagnostics.