Microbial composition, including the incidence of pathogens, of goat milk from the bergamo region of italy during a lactation year.
Sixty samples of raw goat milk intended for Caprino cheese-making were collected from ten farms in the Bergamo area over a 6-month period. Analyses of main microbial groups, somatic cell count (SCC) and pH were performed to determine the effect of origin (farm) and lactation period (April - September) on microbial composition and the incidence of pathogens in milk. Overall mean values were: standard plate count (SPC), 5.0 x 10(4) cfu/ml; yeasts, 2.5 x 10(2) cfu/ml; coliforms, 91 x 10(2) cfu/ml; Escherichia coli, 2.9 cells/ml: enterococci, 1.1 x 10(2) cfu/ ml; lactococci, 3 4 x 10(3) cfu/ml; lactobacilli, 3.0 x 10(3) cfu/ml; halotolerant bacteria, 8.2 x 10(3) cfu/ml; spores of mesophilic aerobic bacteria, 11 cfu/ml; SSC, 9.9 x 10(5) cells/ml; pH, 6.63. Moulds and spores of sulphite-reducing clostridia were found intermittently. Neither Salmonella spp. nor Listeria monocytogenes was detected, while Esch. coli O157: H7 was isolated from one milk sample (an incidence of 1.7%). Staphylococcus aureus was discovered at a level > 10(2) cfu/ml in 26 samples (43%) with an overall mean of 12 x 10(3) cfu/ml, whereas coagulase-negative staphylococci were found in 54 samples (90%) with an overall mean of 1.3 x 10(3) cfu/ml. Of Staph. aureus strains, 23% proved to be enterotoxinogenic with a prevalence of enterotoxin C producers. Staph. caprae was the coagulase-negative species most frequently isolated; none of the coagulase-negative staphylococci strains synthesized any of the enterotoxins tested for. Sample source was the major factor affecting the microbial composition of goat milk: significant differences (P < 0.01) were observed among samples from different farms for SPC, coliforms, lactococci, lactobacilli and halotolerant bacteria. Period of lactation had a significant effect (P < 0.025) on SCC and pH. SPC correlated well with coliforms, lactococci and lactobacilli; SSC did not reveal positive interactions with any microbial groups or pH.
Foschino
Roberto
R
Università degli Studi di Milano, Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Milano, Italy. Roberto.Foschino@unimi.it
Invernizzi
Alessandro
A
Barucco
Roberto
R
Stradiotto
Katia
K
D000818:Animals; D001419:Bacteria / Q000254:growth & development* / Q000302:isolation & purification; D002452:Cell Count / Q000662:veterinary; D015169:Colony Count, Microbial / Q000662:veterinary; D005260:Female; D015511:Goat Diseases / Q000453:epidemiology* / Q000382:microbiology; D006041:Goats; D006863:Hydrogen-Ion Concentration; D015994:Incidence; D007558:Italy / Q000453:epidemiology; D008413:Mastitis / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D008892:Milk / Q000382:microbiology*; D015003:Yeasts / Q000254:growth & development / Q000302:isolation & purification