Diagnostična uporaba preverjanja usposobljenosti mlekarskih laboratorijev

The composition of raw milk (RM) is important for milk recording, herd improvement, payment of milk and for quality evaluation. The reliability of routine analytical results is therefore significant. A mistake occurrence could jeopardize the efficiency of results. Milk laboratories (ML) perform the systems of analytical quality assurance. Proficiency tests are carried out usually by 10 RM samples with modified variability of components. At evaluation the system of Euclidian distance (Re=( 2+sd2)0,5) for participants order according to their analytical result reliability is used. Two specificaly modified types (designs) of systematic diagnostical graphs were constructed on the Re basis. The first type of flow diagnostical diagram for RM analysators is based on Shewhart s diagram principles for Re parameter (alternating system of result rendering before and after calibrations). The second type is based on analysator set comparisons before (proficiency test results) and after calibration (success of calibration) by Re. The opposite comparison is possible and valuable as well. It makes possible the diagnosis and incidental co-ordinating of the corrections in the case of the unconformity occurrence. The positive contributions of the developed diagnostic graphics system are expected to: - improvement of estimation of unconformity sources of RM routine analytical results, their origin and character- determination and improvement of incidental result corrections and instrument repairs- improvement of reliability of routine results of RM analyses in general.Sestava surovega mleka (SM) je pomembna za kontrolo proizvodnje, selekcijo, plačevanje in vrednotenje kakovosti mleka. Zanesljivost rutinskih metod je ključnega pomena, ker bi napake ogrozile verodostojnost rezultatov. Mlekarski laboratoriji vpeljujejo sisteme za zagotavljanje kakovosti analitskih postopkov. Preverjanje usposobljenosti se izvaja navadno na 10 vzorcih SM z različno vsebnostjo osnovnih sestavin. Za preverjanje zanesljivosti analitskih rezultatov se pogosto uporablja sistem Evklidskih distanc (Re=( 2+sd2)0,5). Na osnovi Re sta bili zasnovani dve modifikaciji modela diagnostičnih grafov. Prvi tip diagramov poteka za analizo SM temelji na Shewhart ovem diagramu za parameter Re (sistem za določitev rezultata pred in po kalibraciji). Drugi tip temelji na primerjavi serij rezultatov pred in po kalibraciji z uporabao Re. Primerjava omogoča diagnozo in korekcije v primeru neskladja rezultatov. Od razvoja diagnostičnega grafičnega sistema si obetamo izboljšano določitev virov in narave neskladnosti analitskih rezultatov rutinske kontrole sestave SM, izboljšanje in korekcij rezultatov in instrumentov ter izboljšanje zanesljivosti rutinski rezultatov analize SM na splošno

Analyse of relationships between freezing point and selected indicators of udder health state among cow, goat and sheep milk

Milk freezing point (MFP) is important quality indicator. Aim was to analyse the relationships of MFP to selected udder health milk indicators (MIs) by comparison between cows (reference), goats and sheep. Bulk milk samples came from 3 herds of Czech Fleckvieh (B, n 93) and 1 goat herd and sheep flock (White short-haired, W, n 60; Tsigai, C, n 60). Animal nutrition was performed under the typical country conditions. MIs which were investigated: DM, dry matter; SNF, solid non fat; L, lactose (all in %); SCC, somatic cell count (103 ml−1); EC, electrical conductivity (mS cm−1); MFP (°C); Na and K (in mg kg−1). W MFP was −0.5544 ± 0.0293, B −0.5221 ± 0.0043 and C −0.6048 ± 0.0691 °C. The B MFP was related to L (−0.36; P < 0.01), W was not related to L (−0.07; P > 0.05) and C was related to L (0.40; P < 0.01). These facts could be explainable by worse SCC geometric averages for used W (3,646 103 ml−1) and C (560 103 ml−1) milk as compared to B (159 103 ml−1). Only 0.5 and 10.5% of variations in MFP were explainable by variations in DM and SNF in B, 32.7 and 12.8% in W but already 49.4 and 45.0% in C. Higher C values were caused by high MFP variability, 11.8% (C) versus 0.8% (B). There is possible to derive the more reliable MFP qualitative limits for more efficient monitoring rules of milk quality problems in B, W and C

Validation of modified milk reference sample in terms of its suitability for infra-red analysis calibration via evaluation of physical properties

Routine milk analyses using the efficient indirect infra-red method are important for the milk food chain quality. The reliability of the results depends on the calibration quality. It is important to use a relevant set of reference calibration samples (RCSs). RCSs with right range of values can be prepared using various methods. This paper was aimed to balance the impacts of dilution for decrease of main components in RCSs because of minimal change of matrix interference effects. Cow milk samples (MSs) were diluted (4/1) using distilled water, NaCl solution and a solution with specific composition (SC; because of disturbance in the balance of the milk matrix (NaCl 1.145; KCl 0.849; K2HPO4 1.8463; citric acid 1.7; urea 0.3 g / l)) for reduction in main milk components. Fat (F), crude protein (CP), lactose (L), milk freezing point (MFP), osmolality (OS) and electrical conductivity (EC) were measured in all (original as well as modified) MSs. The lowest MFP and OS were in the original milk −0.5559 °C and 274.5 mOsmol/kg. The MFP was increased to −0.4369 °C and osmolality decreased to 217.83 ­mOsmol/kg by the addition of water. The MFP was decreased (−0.4903 °C) and returned to original milk value by the addition of NaCl solutin. MFP was −0.4788 °C due to SC addition. The decrease was less than for NaCl. The ability of other SC components (K2HPO4, KCl, citric acid and urea) to MFP decrease is less than for NaCl solution. EC was highest for NaCl set 4.69 mS / cm, EC for SC was 4.48 mS / cm (P < 0.001). The original MSs set showed EC 4.27 mS / cm. The SC was the nearest to original MSs in terms of total mineral composition. ECs for both modifications differed (P < 0.001) from original MSs. The procedure is applicable for balance of interference effects of milk matrix because of relevant calibration

Exploratory analysis of dynamics of frequency distribution of raw cow milk quality indicators in the Czech Republic

A consistent link of the raw milk quality (RMQ) to the farmer price is essential. The aim was to analyse the properties of milk quality indicators (MQIs) and propose a new synthetic relative MQI (SQSM) from among various individual MQIs. SQSM could serve for consistent inclusion each quality change into the price. The paper was focused on exploratory analysis (normality (N) testing of files of MQIs). On the basis of the results, the MQIs were divided into two groups without and with necessity of original data transformation (TRN). Log and Box–Cox TRNs were tested in terms of possibilities of the files approach to the normal data frequency distribution (FD). The compositional MQIs deviated less and health and hygienic MQIs more from normal FD in original data (P < 0.05). The TRNs approached the data files to N very markedly in health and hygienic MQIs. The synthesis of various values of MQIs into SQSM was proposed. SQSM values were derived from model file of real data about MQIs and validated for use at farmer milk price modifications by the normality FD test. 33.3% of month SQSM files were normal (P > 0.05), the other were very close to the N with negligible deviations. The useability of the SQSM system for the balancing of raw milk purchase price premiums and penalties was tentatively confirmed

The effects of sample fat value manipulation on raw cow milk composition and indicators

Values of milk indicators (MIs) can be influenced by sampling errors and milk manipulation. This paper estimated the freezing point depression (FPD) and other MIs drifts which can cause fat movement. That is important for: – preparation of reference milk samples (MSs) for proficiency testing and instrument calibrations; – estimation of the impact of milk treatment as centrifugation in dairy plants on FPD. Five MSs (A = original milk; milk with modified fat (F) content; B = less F, C = low F, D = more F, E = high F) were created (gravitation F separation at 4 °C for 12 hours) with the same milk matrix 12× per year. F averages increased by 4.80% (122.1%) from 1.68 to 6.48% due to manipulation. It increased variability of MIs especially for SNF (solids non fat), L (lactose) and CP (crude protein). SCC (somatic cell count) averages increased by 803 (196.8%) from 9 to 812 thousand.ml−1. Correlation (r) F × SCC was 0.85 (P < 0.001). SNF, L and CP averages decreased by 0.47% (5.3%), 0.31% (6.3%) and 0.17% (5.0%). Correlations were −0.78, −0.75 and −0.64 (P < 0.001). Urea decreased along with F increase by 1.05 mg.100ml−1 (2.9%) but with r −0.13 (P > 0.05). Acetone increased by 1.37 mg.l−1 (47.6%) with r 0.21 (P > 0.05). Electrical conductivity decreased by 0.23 mS.cm−1 (6.0%) with r −0.15 (P > 0.05). Alcohol stability was reduced by 0.14 ml (23.3%) with r −0.15 (P > 0.05). FPD, titration and actual acidity were not influenced

Result interpretation of experimental calibration for milk citric acid determination via infra-red spectroscopy (MIR-FT)

Citric acid (KC) in milk is indicator of cow energy metabolism. Milk laboratories set up KC determination. A method can be infra-red analyse (MIR-FT). The goal was to develop a relevant method for reference sample preparation for MIR-FT (indirect method, Lactoscope FTIR and MilkoScan FT 6000) calibration. As reference was used a photometric method (c; 428 nm). KC was added (n = 3) into some re­fe­ren­ce milk samples (n = 10, bulk milk). Mean value was 9.220 ± 3.094 mmol . l−1 with variation range from 6.206 to 15.975 mmol . l−1. Recovery c was from 100.8 to 120.2 %. Correlation between c and ­MIR-FT were from 0.979 to 0.992 (P < 0.001). These were lower in the set of native milk samples (n = 7), from 0.751 (Lactoscope FTIR; P < 0.05) to 0.947 (MilkoScan FT 6000; P < 0.001) in comparison to original va­lues from 0.981 to 0.992 (n = 10; P < 0.001). Correlations between calibrated MIR-FT instruments were from 0.958 to 1.0 (P < 0.001). Average recovery for instruments (n = 12) was 101.6 ± 18.1 %. The mean differences between c method and MIR-FT after calibration (n = 4) moved from −0.001 across zero to 0.037 %. Standard deviation of differences was from 0.0074 to 0.0187 % at MilkoScan FT 6000 and from 0.0105 to 0.0117 % for Lactoscope FTIR. Relative variability of differences (MIR-F (filter technology) and FT) for major components fat (T), proteins (B) and lactose (L) in total and minor components KC and free fatty acids (VMK) was estimated to 1.0 and 7.2 and 34.4 %. The KC result is inferior than T, B and L superior than VMK. Autocorrelation (0.042; P > 0.05) of results demonstrated the in­de­pen­den­ce of consecutive measurements. Milk preservation effect amounted 0.2323 (P < 0.001) with bronopol and 0.0339 (P > 0.05) mmol . l−1 with dichromate. It was (3.0 and 0.44 %) practically negligible, redeemable via relevant calibration. The results of proficiency testing in post-calibration period and evaluation of double transport stress effect samples (difference was −0.006 ± 0.071 mmol . l−1 (P > 0.05)) demonstrated the useability for central calibration system. Milk KC results of MIR-FT calibration were good and can be suitable for practical screening

Effect of organic farming on selected raw cow milk components and properties

Organic dairying is an alternative for friendly exploitation of environment. This paper was focused on impacts of organic dairying on milk composition and properties. The conventional (C) cow milk was compared to organic (O) milk. Holstein bulk milk samples (BMSs) from winter and summer season in 4 C and 4 O (n = 32 and 32 BMSs; 2 years) herds were investigated. 6 herds were grazed and 2 C herds were not grazed. Mean O cow milk yield (MY, 305 lactation days) was 7037.3 ± 421.5 and C MY 7015.8 ± 1068.1 kg. Higher values (P < 0.05) in O milk had: log acetone (0.7321 > 0.6048); titration acidity (8.34 > 7.82 ml 0.25 mol.l−1 NaOH); alcohol stability (0.6 > 0.44 ml); time for enzymatic coagulation (150.75 > 115.03 second); whey protein (0.54 > 0.49%); fat/crude protein (1.2 > 1.15); milk fermentation ability (FAM) by titration (31.45 > 22.18 ml 0.25 mol.l−1 NaOH). Lower values (P < 0.05) in O milk had: solids–not–fat (8.64 < 8.73%); urea content (19.91 < 29.03 mg.100ml−1); electrical conductivity (3.66 < 4.08 mS.cm−1); whey volume (32.03 < 34.53 ml); crude protein (3.16 < 3.25%); casein (2.47 < 2.58%); non–protein nitrogen compounds (0.15 < 0.18%); urea nitrogen in non-protein nitrogen ratio (40.81 < 49.0%); casein numbers for crude protein and true protein (78.12 < 79.58 and 81.99 < 84.11%); coli bacteria count in normal and logarithm form (330.56 < 1502.92 CFU.ml−1 and 1.484 < 2.5823); actual yoghurt acidity (4.71 < 4.8). O cows suffered probably from lower energy and nitrogen compounds intake due to feeding under mentioned conditions. O milk could be a little better environment for yoghurt cultivation

Analysis of calibration results for casein determination via indirect method of infrared spectroscopy

Casein measurement is important for cheesemaking and control of dairy cow nutrition. Reference Kjeldahl method is not suitable for routine purposes. Infra-red spectroscopy MIR and MIR-FT use can be a solutin. However, their casein specifity is relatively limited. Aim of the work was to assess the quality of performed calibrations for validation of calibration parameters. A retrospective analysis of MIR and MIR-FT calibrations was performed for estimation of limits their suitable parameters. Mean casein values of reference sample sets varied from 2.49 to 2.7% (2.61 ± 0.155). Mean variation range was 0.561 ± 0.164%. The mean correlation coefficient of calibration (KKK) was 0.974 ± 0.018 (P < 0.001). The mean standard deviation of mean for individual differences (SDID) was 0.03 ± 0.011% (from 0.01 to 0.08). MIR-FT results were slightly better both for calibration and for proficiency testing. The high and low KKKs were higher in the case of accepted calibration as in proficiency testing for MIR-FT and MIR (0.986 > 0.964 and 0.970 > 0.948; 0.982 > 0.947 and 0.947 > 0.911; P < 0.001). The casein number varied from 79.4 to 80.56% in bulk milk samples in three years, its variability was low from 1.4 to 1.5% relatively, which shows on relatively reliable casein analyses by methods MIR and MIR-FT. It does not need to agree fuly for individual milk samples. It is linked more to MIR than MIR-FT. Limits for acceptable calibration parameters were derived: > 0.945 for KKK; 0.048 for SDID and 0.029% for mean difference as maximum