This study was carried out to investigate the quality of raw milk after the decision of the dairies to collect the milk every two days and not daily as it has been performed till the year 2005. In ...wider central Slovenian production area we collected in winter and summer season 203 raw milk samples obtained from farm bulk milk tanks, collecting points and transportation tanks at the entrance to the dairy was studied. The total bacterial count, the number of coliforms, psychrotrophic micro-organisms, coagulase-positive staphylococci, yeasts and moulds were analysed using standard methods. The presence of mould species and production of aflatoxins were studied as well. The total bacterial count was higher than 100 000 cfu/ml in 48 (23.6%) out of all tested samples. Its mean value in all milk samples was 4.5 log10 cfu/ml1. The mean numbers of coliform bacteria, psychrotrophic micro-organisms, yeasts and moulds together, and coagulase-positive staphylococci were 2.1 log10 cfu/ml, 3.7 log10 cfu/ml, 2.3 log10 cfu/ml and 1.97 log10 cfu/ml, respectively. Nobeden izmed izoliranih sevov iz rodu Aspergillus, ki je kazal značilno rast na gojišču AFPA, ni na gojiščih YES in YGC z metil-β-ciklodekstrinom tvoril aflatoksina M1.
The presence of pathogenic and some indicator micro organisms was studied in 40 samples of cheese comprising 14 curd samples, 13 samples of soft ripened salted or non-salted cheese and 13 samples of ...semi-hard cheese manufactured at five small dairy-processing plants. The mean number of coagulase-positive staphylococci in all tested samples was 2.5 × 104cfu*g–1, while the number of E. coli bacteria was 1.4 × 106cfu g–1. In 20.0% out of 40 samples tested, the number of coagulase-positive staphylococci exceeded the prescribed regulations, particularly in soft cheese (12.5%) and curd (7.5%). About 17.5% of samples were contaminated with E. coli in higher concentrations than national valid regulations allowed. The number of E. coli was mostly exceeded in soft cheese and curd in 12.5% and 5.0% of all examined samples, respectively. One sample of semi hard cheese was contaminated with sulphite-reducing clostridia. Proteus was detected in 3 samples (7.5%) and L. grayi in 1 (2.5%) sample. Salmonela and L. monocytogeneswere not detected. According to the valid regulations 9 (22.5%) samples in our investigation did not reach the adequate microbiological quality. Both, yeasts and moulds were isolated from 60% of tested cheese samples with average concentrations of 5.8 × 104 cfu g–1 and 2.0 × 104 cfu g–1, respectively. The genera Geotrichum (91.9%), Moniliella (5.4%) and Aspergillus (2.7%) were the most frequently isolated strains from examined cheese samples. The Aspergillus strains did not belong to the species A. flavus or A. parasiticus and did not produce aflatoxins.
The microbiological quality of 98 samples taken at some critical control points during the milking and processing of 14 semi-hard cheese made from raw cow milk by individual Slovenian producers was ...studied. The sampling points were: swabs from cows’ udders, milking machines inner surfaces before and after milking, fresh raw and mixed milk from vats, whey immediately after curdling, brine, cheese after one month of ripening and after the following month of being kept vacuum packed at 6 °C. The high number of micro-organisms on the inner surfaces of washed milking machines before milking revealed ineffective cleaning (washing) by about 60% of cheese producers. There were no seasonal differences in the number of micro-organisms, except that the number of coliforms was higher in spring. The average of total number of micro-organisms was 4.9·105 cfu/ml in raw milk and 5.5·106 cfu/ml in mixed milk from a vat (raw fresh milk mixed with milk kept for about 18–24 hours at room temperature), which did not grow significantly during cheese-processing. The number of coliforms in raw and mixed milk was in the range of 3.4·105 cfu/ml and fell to 5.4·104 cfu/ml in whey. The average number of enterococci, aerobic spore-forming micro-organisms, yeasts and moulds, lactobacilli, lactococci, proteolytic and lipolytic micro-organisms in milk and in whey were in the same logarithmic range of about 2.2·104, 310, 3.5, 31.2·104, 2.1·106, 6.2·103 and 1.7·104 cfu/ml of the sample, respectively. Listeria spp. was isolated from 5.3% (cows’ udders, milking machine, milk and whey), while none of the examined samples were positive to the presence of Salmonella spp. and Campylobacter spp. Proteus was present in 7 (7%) cases of milk and whey. Clostridia were detected in 10 (10%) samples (swabs, raw milk, whey). E. coli was isolated from 12 (12%) samples of swabs, raw and mixed milk, whey and brine. After one month of ripening the average total bacterial count was 9.2·107 cfu g–1 of cheese, of these 6.8·107 represented lactic-acid producers and 2.2·107 represented non-lactic acid producers. The average number of coliforms, enterococci, aerobic spore-forming micro-organisms, yeasts and moulds, lactococci, lactobacilli, proteolytic and lipolytic micro-organisms were 2.0·105, 6.3·106, 280, 960, 2.5·107, 9.8·107, 450 and 9.8·104 cfu g–1 of cheese, respectively. Salmonella spp., Listeria spp., Proteus, sulphite-reducing clostridia and Campylobacter spp. were not detected in cheese samples. E. coli was found in 4 (30%) of samples while coagulase positive staphylococci were present in 9 (64%) of cheese samples. A high number of enterococci (from a min. 3.103 to a max. 15.107 cfu g–1) and coliforms (from a min. 10 to a max. 19.105 cfu g–1) were detected as well. After one month of keeping vacuum-packed ripened cheeses at 6 °C, the number of micro-organisms did not rise significantly, except for the number of yeasts and moulds which grew to 3.6·104 cfu g–1 of cheese. Because of improper milking and processing hygiene conditions, three (21%) of the tested cheese samples did not correspond to the microbiological criteria according to the applicable regulations.
Factors affecting the freezing point of milk in a herd of 200 Black and White cows with the average milk yield of 8 386 kg in the lactation and 8 328 kg in the standard lactation were examinated. ...Over the period of one year (2002) and based upon 1 773 individual monthly collected milk samples with the average contents of 3.91% fat, 3.26% protein, 4.54% lactose, 33.4 mg/100 ml urea and 331000 somatic cells per ml in milk were determined. The average freezing point of milk (n = 1 680) was estimated to be –0.527 ºC, with a range from -0.562 ºC to -0.423 ºC. In 210 (12.5%) samples was higher than -0.515 ºC. The lowest freezing point (-0.532 ºC) was found in the samples collected in the first month after calving and highest (-0.522 ºC) in the samples of 12th month of lactation. The differences between the freezing point of milk after the first and the second calving (-0.530 ºC; P < 0.05) and those after the fifth calving (-0.523 ºC; P < 0.05) were also significant. The samples collected in month from January to April (-0.538 ºC to -0.532 ºC) were significantly lower in comparison to samples collected in May and June (-0.517 ºC and -0.519 ºC). The following statistically significant correlation coefficients between cows' properties, milk composition and the freezing point of milk were found: month of lactation r = 0.233 (P < 0.001); lactation number r = 0.196 (P < 0.001); age of cows (years) r = 0.231 (P < 0.001); month of the year r = 0.0253 (P < 0.001); milk yield per milking day r = -0.106 (P < 0.001); fat corrected milk content (FCM) per milking day r = -0.234 (P < 0.001); lactose % r = -0.530 (P < 0.001); fat % r = -0.351 (P < 0.001); protein % r = 0.058 (P < 0.05); urea mg/100 mL r = 0.091 (P < 0.001) and somatic cell count r = 0.154 (P < 0.001). The sum of effects (month of the year, lactation lenght and fat, protein and lactose content of milk) was found to account for about 70% variability of the total depression of milk freezing point (R2 = 0.698).
For the evaluation of milk quality on the basis of true protein it is essential to use fast, but accurate and precise methods. On the basis of the results of classical analysis by reference methods, ...the reliability of FT-IR technique for proteins, casein and urea is described. The ratio between casein, whey proteins, non-protein nitrogen components and urea content has been set.
U ovome su članku prikazani glavni čimbenici u procjeni mikrobiološkog ispitivanja hrane. Prikazano je nekoliko točaka validacije kvantitativnih i kvalitativnih mikrobioloških metoda. Osim toga, ...definiraju se izrazi "sukladnost" i "istovjetnost" referentne metode s "internom" metodom u smislu akreditacija metoda. Članak opisuje kako evaluirati rutinsku metodu u odnosu na referentne/službene metode s obzirom na rezultate dobivene brojenjem automatskim epifluorescentnim mikroskopom s pomoću uređaja BactoScan 8000 namijenjenog za utvrđivanje bakteriološke kakvoće mlijeka te daje opće upute za usporedbu navedenih metoda. Tu je i pregled aspekata osiguranja kakvoće koji se uzimaju u obzir u primjeni rutinske metode te primjer međulaboratorijske prosudbe vrsnosti uz pomoć epifluorescentne mikroskopske metode koja je uobičajena u laboratorijima za mliječne proizvode.
Istraživani su čimbenici koji utječu na točku ledišta mlijeka u stadu od 200 crno-bijelih krava, prosječne proizvodnje mlijeka u laktaciji od 8 386 kg te 8 328 kg mlijeka u standardnoj laktaciji. Na ...temelju jednogodišnjeg istraživanja (2002.) i 1 773 pojedinačna uzorka, dobivene su sljedeće vrijednosti prosječnog sastava: 3,91% masti, 3,26% proteina, 4,54% laktoze, 33,4 mg/100 mL ureje i 331 000 somatskih stanica u mL mlijeka. Prosječna vrijednost točke ledišta mlijeka (n=1 680) iznosila je -0,527 ºC, s rasponom od -0,562 ºC do -0,423 ºC. U 210 (12,5%) uzoraka točka ledišta bila je viša od
-0,515 ºC. Najniža je točka ledišta (-0,532 ºC) u uzorcima prikupljenim prvog mjeseca nakon teljenja, a najviša (-0,522 ºC) u uzorcima prikupljenim dvanaestog mjeseca laktacije. Značajne su i razlike između točke ledišta mlijeka u prvoj i drugoj laktaciji (-0,530 ºC; P<0,05) te nakon petog teljenja (-0,523 ºC; P<0,05). Vrijednosti točke ledišta u uzorcima prikupljenim od siječnja do travnja (-0,538 ºC do -0,532 ºC) bile su značajno niže od uzoraka prikupljenim u svibnju i lipnju (-0,517 ºC i -0,519 ºC). Pri tome su dobiveni sljedeći koeficijenti korelacija između osobina krava, sastava mlijeka i točke ledišta mlijeka: mjesec laktacije r = 0,233 (P<0,001); broj laktacija r=0,196 (P<0,001); dob krava (godine) r=0,231 (P<0,001); mjesec u godini r=0,0253 (P<0,001); količina mlijeka na dan mužnje r=-0,106 (P<0,001); količina mlijeka korigirane masti (FCM) po dnevnoj proizvodnji mlijeka r=-0,234 (P<0,001); laktoza % r=-0,530 (P<0,001); mast % r=-0,351 (P<0,001); protein % r=0,058 (P<0,05); ureja mg/100 mL r=0,091 (P<0,001) i broj somatskih stanica r=0,154 (P<0,001). Zbroj učinaka (mjeseci u godini, trajanje laktacije te udio masti, proteina i laktoze u mlijeku) čini 70% varijabilnosti točke ledišta mlijeka (R2=0,698).
Primjerenost metode automatske epifluorescentne mikroskopije (instrumentom BactoScan 8000) za određivanje ukupnog broja bakterija u sirovom mlijeku provjerena je kao metoda za određivanje kvalitete ...mlijeka proizvođača u svrhu plaćanja po higijenskoj kakvoći. Rezultati određeni BactoScan-om uspoređeni su rezultatima brojanja kolonija na pločama metodom IDF Standard 100 B : 1991. Nakon pretvorbe broja pulsova BactoScana (y) i broja kolonija na pločama (x) u dekadske logaritme izračunata je jednadžba pravca regresije y= 0,916 x + 0,714 i standardna devijacija ostatka sy/x= 0,26 log jedinica. Koeficijent korelacije između dviju metoda bio je r = 0,95 (n = 701). Ponovljivost (preciznost, sr) instrumenta na različitim razinama impulsa varirala je od 0,02 log jedinica do 0,11 log jedinica uz broj kolonija <100.000 m.o./ml. Granica pouzdanosti za P = 0,95 bila je ±0,517 log BSC/impulsa/ml.
Posljedica promijenjenih uvjeta kod proizvodnje mlijeka (primjena strojne muže) su i povrede kemijskih sastojaka mlijeka, osobito mliječne masti te nastanak slobodnih masnih kiselina (proces ...lipolize). Preveliku količina slobodnih masnih kiselina snižava kvalitetu mlijeka, a može biti i pokazateljem kvalitete opreme i tehnologije muže. U pokusu koji smo izveli, testirali smo utjecaj različitih sistema muže na pojedine sastojke mlijeka i na količinu slobodnih masnih kiselina. Ustanovili smo da sistem muže može jako utjecati osobito na količinu slobodnih masnih kiselina u mlijeku
