The aim of this study was to evaluate the transfer of the most widely used antibiotics in dairy goats from milk to cheese as well as their effect on the cheese-making process and cheese characteristics during ripening. Antibiotic-free milk was spiked individually with 7 veterinary drugs (amoxicillin, benzylpenicillin, cloxacillin, erythromycin, ciprofloxacin, enrofloxacin, and oxytetracycline) at an equivalent concentration of the European Union maximum residue limit. Spiked goat milk was used to make mature Tronchón cheeses, which were analyzed at 0, 30, and 60 d of maturation to determine pH, chemical composition, proteolytic and lipolytic activities, and color and textural properties. A sensory evaluation of 60-d ripened cheeses was carried out. Cheeses from raw antibiotic-free goat milk were made simultaneously to be used as reference. The cheese-making process was unaffected by the presence of most antibiotics evaluated. Only erythromycin and oxytetracycline significantly increased the time required for cheese production (122 ± 29 and 108 ± 25 min, respectively). However, variable amounts of antibiotics, ranging from 7.4 to 68%, were transferred from milk to cheese, with oxytetracycline and quinolones showing the highest retention rates. In general, antibiotic residues present in the cheeses at the beginning of maturation decrease significantly along time. Thus, β-lactams and erythromycin residues were not detectable after 30 d of ripening. However, relatively high concentrations of enrofloxacin (148 ± 12 µg/kg) and ciprofloxacin (253 ± 24 µg/kg) residues were found in the cheeses after 60 d of maturation. The quality characteristics of the Tronchón cheeses were only slightly affected by such substances, with few significant differences in the free fatty acid concentration and color and textural properties of the cheeses. Results herein indicate that the use of goat milk containing antibiotics, such as quinolones, at the European Union maximum residue limit for cheese production could adversely affect the safety of the final products because relatively high concentrations of these substances could be retained in soft and semi-mature cheeses, making it necessary to assess the risk for consumer health. Studies on the partition of the antibiotic substances during cheese-making, using specific technologies, would be convenient to guarantee the safety of cheese and related products.

The Delvotest method detection limits per manufacturer's instructions at a fixed reading time of 3 h for 24 antimicrobial agents were determined in ewe milk by photometric measurement. For each drug, eight concentrations were tested on 20 ewe milk samples from individual ewes. Detection limits, determined by means of logistic regression models, were (microg/kg): 3, amoxycillin; 2, ampicillin; 18, cloxacillin; 1, penicillin "G"; 34, cefadroxil; 430, cephalosporin "C"; 40, cephalexin; 20, cefoperazone; 33, Ceftiofur; 18, cefuroxime; 6100, streptomycin; 1200, gentamycin; 2600, neomycin; 830, erythromycin; 100, tylosin; 180, doxycycline; 320, oxytetracycline; 590, tetracycline; 88, sulfadiazine; 44, sulfamethoxazole; 140, sulfametoxypyridazine; 48, sulfaquinoxaline; 12,000, chloramphenicol; and 290, trimethoprim. Whereas the beta-lactam antibiotics, sulphonamides, and tylosin were detected by Delvotest method at levels equal to those of maximum residue limits, its sensitivity needs to be enhanced to detect aminoglycosides, tetracyclines, streptomycin, chloramphenicol, and trimethoprim residues in ewe milk or to develop an integrated residue detection system for ewe milk with different sensitive microorganisms for each group of antiinfectious agents.

The quality of colostrum of Murciano-Granadina goats was studied to establish the transition period and the time when milk can be marketed. Forty-three dairy goats were used: 19 primiparous (15 single births; 4 multiple births) and 24 multiparous (10 single births; 14 multiple births). Samples were collected every 12h during the first week postpartum. Physicochemical parameters and somatic cell count were determined. Analysis of variance with repeated measures was used to study the effect of different factors: postpartum time, litter size, lactation number, their interactions, and production level on colostrum. Postpartum time had a significant effect on all parameters studied, which decreased along the first week of lactation, whereas lactose, pH, and conductivity increased. Based on these results, colostrum secretion takes place until 36 h postpartum (hpp). In relation to other factors of variation studied, the lactation number influenced most colostrum components, whereas the litter size only affected the pH value, protein and lactose content. The production level influenced only the protein and dry matter contents, with an inverse relationship. Milk produced during the period between 36 and 96 hpp is considered transition milk, which should not be commercialized. Milk collected after 4d postpartum (96 hpp) could be marketed, ensuring that its composition does not present a risk in the dairy industry.

The effects of preservatives (potassium dichromate and sodium azide), heat treatment (untreated and 82 degrees C/10 min), and lactation stage upon the response of the microbial tests (BRT AiM and Delvotest) utilized for the detection of residues of antimicrobial substances in ewe milk were examined. Milk samples were collected from the morning milking of 50 Manchega ewes every 2 wk, from 15 d postpartum until the end of lactation. A total of 2322 samples were analyzed by BRT AiM with prediffusion and Delvotest microbial tests. The specificity of preservative-free milk samples without heat treatment was high (96.3% for BRT and 97.7% for Delvotest), with results improving for those samples thermally treated at 82 degrees C/10 min (99.0% for BRT and 98.7% for Delvotest). Potassium dichromate produced a total inhibition of growth of Bacillus stearothermophilus with both methods. When acidiol was utilized, the specificity of the samples not treated thermally was lower compared with preservative-free milk samples for the BRT AiM (90.2%) and Delvotest (91.0%) methods, improving when the samples were thermally treated, both for BRT AiM (94.8%) and Delvotest (95.3%), given that the presence of the preservative increased the frequency of doubtful results. The lactation stage significantly affected the results of the methods, with a greater frequency of false-positive and doubtful cases toward the end of the cycle, especially in those samples preserved with acidiol. The greater selectivity in both methods was therefore obtained for preservative-free ewe milk samples with prior heat treatment taken at the beginning or in midlactation period.

Traces of antimicrobials in milk are of great concern for public health. The European Union has established maximum residue limits in milk; these, however, by themselves do not guarantee t... HIGHLIGHTS Pasteurization affects the stability of antibiotics in goat's milk only slightly. Antibiotic residues in milk are transferred to fresh cheese at a relatively high rate. Quinolone and mac...

The presence of residues of antimicrobial substances in milk is one of the main concerns of the milk industry, as it poses a risk of toxicity to public health, and can seriously influence the technological properties of milk and dairy products. Moreover, the information available on the thermostability characteristics of these residues, particularly regarding the heat treatments used in control laboratories and the dairy industry, is very scarce. The aim of the study was, therefore, to analyze the effect of different heat treatments (40°C for 10 min, 60°C for 30 min, 83°C for 10 min, 120°C for 20 min, and 140°C for 10 s) on milk samples fortified with three concentrations of nine β-lactam antibiotics (penicillin G: 3, 6, and 12 μg/liter; ampicillin: 4, 8, and 16 μg/liter; amoxicillin: 4, 8, and 16 μg/liter; cloxacillin: 60, 120, and 240 μg/liter; cefoperazone: 55, 110, and 220 μg/liter; cefquinome: 100, 200, and 400 μg/liter; cefuroxime: 65, 130, and 260 μg/liter; cephalexin: 80, 160, and 220 μg/liter; an...