ABSTRACT
ABSTRACT: The milk bar is an emerging style of retail business that mainly produces pasteurized milk (PM) and other dairy products on-site in many large cities of the People's Republic of China. To date, no data about veterinary drug residues in PM samples produced from milk bars have been reported. The objective of this study was to investigate the safety of PM from a total of 182 PM samples collected from milk bars from 10 provincial capital cities and to analyze the residues of seven classes of 61 veterinary drugs. First, the chemical components were screened with test kits, and then the positive samples were further confirmed by ultraperformance liquid chromatography-tandem mass spectrometry. The results showed that 15 (8.24%) samples were screened positive for veterinary drugs, and six drugs in 11 (6.04%) samples were confirmed. The veterinary drugs detected were penicillin G (2.20%), tetracycline (1.10%), tylosin (1.10%), amoxicillin (0.55%), oxytetracycline (0.55%), and gentamicin (0.55%), with maximum residue levels of 3.4, 11.9, 28.2, 3.0, 26.9, and 63.5 µg kg-1, respectively. Veterinary drug residues were detected as positive in 7 of 10 cities, with the highest detection rate as 14.29% in Urumqi. No positive samples were found in the cities of Nanjing, Tianjin, and Nanning. All detected drug levels were far below the maximum residue levels regulated by China, the European Union, and the Codex Alimentarius Commission. This suggests that the overall veterinary drug residues in PM in milk bars reached the safety code of the country. However, potential risks still exist, and continuous attention should be paid to guarantee the safety of this milk product in the future.
ABSTRACT
A total of 138 lactobacillus strains were obtained from the traditional fermented foods of minority nationalities or infant faeces, respectively. The lactobacillus strains were screened for anticancer effects and probiotic potential. The results showed that 10 strains exerted anti-proliferative activity and higher adhering capability on HT-29 cells. They were then screened for resistance to biological barriers (acid and bile salts), and the four most promising strains were selected. Further analysis revealed that the 4 strains (cell walls and cytoplasm extracts) displayed the high anti-proliferative activity and the large extent of DNA strand breakage in individual cells. Through the selected procedure, cell walls that were extracted from X12, M5 and K14 strains induced apoptosis in HT-29 cells. Further investigation confirmed that apoptosis-inducing ability of cell wall extracts was attributed to the breakdown of mitochondrial membrane potential, which is a known initiation of apoptotic mitochondrial pathway. Cell walls from X12, M5 and K14 strains, were determined to be less harmful to noncancerous Vero cells than to human colon cancer HT-29 cells. These findings suggested that X12, M5 and K14 strains opposing the ability to induce HT-29 cells apoptosis, and cell wall extracts were involved in this apoptosis induction.
