RESUMO
AIM: To characterize four novel autochthonous bifidobacteria isolated from monkey faeces and a Bifidobacterium lactis strain isolated from chicken faeces by evaluating their technological and biological/functional potential to be used as probiotics. Different stressors, including food process parameters and storage, can affect their viability and functionality. METHODS AND RESULTS: The resistance to frozen storage, tolerance to lyophilization and viability during storage, thermal, acidic and simulated gastric resistance, surface hydrophobicity and antimicrobial activity against pathogens were studied. Bifidobacterium lactis Bb12 and INL1 were used as reference strains. The results obtained demonstrated that the new isolates presented strain-dependent behaviour. Good results were obtained for thermal resistance, frozen storage at -80°C and lyophilized powders maintained at 5°C. Cell viability during refrigerated storage was higher when the strains were resuspended in milk at pH 5·0 than at 4·5. The surface hydrophobicity ranged between 7 and 98% depending on the strain. The simulated gastric resistance was improved for the strains incorporated in cheese. Regarding antimicrobial activity, bifidobacteria isolated from monkey presented higher inhibitory capacity than the reference strains. CONCLUSION: This research provides a deeper insight into new strains of bifidobacteria isolated from primates and chicken that have not been previously characterized for their potential use in dairy products and confirm the most robust stress tolerance of B. lactis. SIGNIFICANCE AND IMPACT OF THE STUDY: The possibility of expanding the available bifidobacteria with the potential to be added to a probiotic food necessarily implies characterizing them from different points of view, especially when considering unknown species. For monkey isolates (which showed higher antimicrobial activity against pathogens), more in-depth knowledge is needed before applying strategies to improve their performance. On the contrary, the chicken isolate B. lactis P32/1 showed similar behaviour to the references B. lactis strains; therefore, it could be considered as a potential probiotic candidate.
Assuntos
Bifidobacterium , Probióticos , Animais , Bifidobacterium/isolamento & purificação , Bifidobacterium/fisiologia , Queijo/microbiologia , Galinhas , Fezes/microbiologia , Haplorrinos , Concentração de Íons de Hidrogênio , Viabilidade MicrobianaRESUMO
The effect of high pressure homogenization (HPH) with respect to a traditional heat treatment on the inactivation, growth at 8°C after treatments, and volatile profile of adventitious Leuconostoc strains isolated from Cremoso Argentino spoiled cheeses and ingredients used for their manufacture was evaluated. Most Leuconostoc strains revealed elevated resistance to HPH (eight passes, 100 MPa), especially when resuspended in skim milk. Heat treatment was more efficient than HPH in inactivating Leuconostoc cells at the three initial levels tested. The levels of alcohols and sulfur compounds increased during incubation at 8°C in HPH-treated samples, while the highest amounts of aldehydes and ketones characterized were in heated samples. Leuconostoc cells resuspended in skim milk and subjected to one single-pass HPH treatment using an industrial-scale machine showed remarkable reductions in viable cell counts only when 300 and 400 MPa were applied. However, the cell counts of treated samples rose rapidly after only 5 days of storage at 8°C. The Leuconostoc strains tested in this work were highly resistant to the inactivation treatments applied. Neither HPH nor heat treatment assured their total destruction, even though they were more sensitive to the thermal treatment. To enhance the inhibitory effect on Leuconostoc cells, HPH should be combined with a mild heat treatment, which in addition to efficient microbial inactivation, could allow maximal retention of the physicochemical properties of the product.
Assuntos
Queijo/microbiologia , Manipulação de Alimentos/métodos , Temperatura Alta , Leuconostoc/fisiologia , Pressão , Contagem de Colônia Microbiana , Contaminação de Alimentos/análise , Microbiologia de Alimentos , Conservação de Alimentos/métodos , Tecnologia de Alimentos/métodos , Humanos , Leuconostoc/crescimento & desenvolvimento , Leuconostoc/metabolismo , Viabilidade Microbiana , Fatores de TempoRESUMO
Temperate bacteriophages Ñ iLp84 and Ñ iLp1308, previously isolated from mitomycin C-induction of Lactobacillus paracasei strains 84 and CNRZ1308, respectively, were tested for their resistance to several physical and chemical treatments applied in dairy industry. Long-term survival at 4 °C, -20 °C and -80 °C, resistance to either thermal treatments of 63 °C, 72 °C and 90 °C, high pressure homogenization (HPH, 100 MPa) or classic (ethanol, sodium hypochlorite and peracetic acid) and new commercial sanitizers, namely A (quaternary ammonium chloride), B (hydrogen peroxide, peracetic acid and peroctanoic acid), C (alkaline chloride foam), D (p-toluensulfonchloroamide, sodium salt) and E (ethoxylated nonylphenol and phosphoric acid), were determined. Phages were almost completely inactivated after eight months of storage at 25 °C, but viability was not affected at 4 °C, -20 °C or -80 °C. Both phages tolerated well HPH treatments. Phage iLp1308 showed higher thermal resistance than Ñ iLp84, but neither resisted 90 °C for 2 min. Best chemical inactivation was accomplished using peracetic acid or biocides A, C and E, whereas biocides B and D were completely ineffective. These results help to improve selection of chemical agents and physical treatments to effectively fight against phage infections in dairy plants.
Assuntos
Bacteriófagos/química , Bacteriófagos/efeitos dos fármacos , Desinfetantes/farmacologia , Lactobacillus/virologia , Esterilização/métodos , Bacteriófagos/crescimento & desenvolvimento , Contaminação de Alimentos/prevenção & controle , Microbiologia de Alimentos , Temperatura Alta , Pressão , Inativação de Vírus/efeitos dos fármacosRESUMO
High-pressure homogenization (HPH) is one of the most promising alternatives to traditional thermal treatment of food preservation and diversification. Its effectiveness on the deactivation of pathogenic and spoilage microorganisms in model systems and real food is well documented. To evaluate the potential of milk treated by HPH for the production of Crescenza cheese with commercial probiotic lactobacilli added, 4 types of cheeses were made: HPH (from HPH-treated milk), P (from pasteurized milk), HPH-P (HPH-treated milk plus probiotics), and P-P (pasteurized milk plus probiotics) cheeses. A strain of Streptococcus thermophilus was used as starter culture for cheese production. Compositional, microbiological, physicochemical, and organoleptic analyses were carried out at 1, 5, 8, and 12 d of refrigerated storage (4 degrees C). According to results obtained, no significant differences among the 4 cheese types were observed for gross composition (protein, fat, moisture) and pH. Differently, the HPH treatment of milk increased the cheese yield about 1% and positively affected the viability during the refrigerated storage of the probiotic bacteria. In fact, after 12 d of storage, the Lactobacillus paracasei A13 cell loads were 8 log cfu/ g, whereas Lactobacillus acidophilus H5 exhibited, in P-P cheese, a cell load decrease of about 1 log cfu/g with respect to the HPH-P cheese. The hyperbaric treatment had a significant positive effect on free fatty acids release and cheese proteolysis. Also, probiotic cultures affected proteolytic and lipolytic cheese patterns. No significant differences were found for the sensory descriptors salty and creamy among HPH and P cheeses as well as for acid, piquant, sweet, milky, salty, creamy, and overall acceptance among HPH, HPH-P, and P-P Crescenza cheeses.