Evaluation of antibacterial activity of essential oils extracted from Thymus satureioides and Mentha pulegium against antibiotic resistance bacteria from raw sheep milk

Aims@#This study evaluated in vitro resistance and susceptibility of Enterobacteriaceae (Escherichia coli and Klebsiella oxytoca strains) and Staphylococci strains, isolated from sheep’s milk, against antibiotics and essential oils from Thymus satureioides and Mentha pulegium.@*Methodology and results@#Antibiotic resistance tests were done using disc diffusion while essential oils were extracted by steam distillation and yields were calculated relative to plant dry matter. Gas chromatography-mass spectrometry (GC-MS) was used to analyze each oil's chemical composition. Amoxicillin + Clavulanic acid (AMC), Cefotaxime (CTX), Cefoxitine (FOX), Nalidixic acid (NA), Gentamicin (CN), Ciprofloxacin (CIP) and Ofloxacin (OFX) were very effective against the E. coli strains tested. Half of the strains were resistant to AMC, 60% to Ticarcillin (TIC) and 80% to Tetracycline (TE). Klebsiella oxytoca was resistant against AMC, FOX and TIC (100%). Antibiotic-resistant testing on Staphylococci strains indicated Staphylococcus capitis and S. chromogenes as the most sensitive. Staphylococcus aureus, S. xylosus and S. cohnii ureal exhibited less resistance to Oxacilin (OX), TE, Pristinamycin (PT), Erythromycin (E) and Penicillin (P). Mentha pulegium resulted in a higher yield of essential oil of 3.2% oil compared to T. satureioides with only 1.85% yield. The monoterpene oxygenated derivatives, monoterpene hydrocarbons and phenols are found in essential oil extracts. Thymus satureioides essential oil had high antibacterial activity even at low concentrations (0.2; 0.55 g/mL). The minimal bactericidal concentration (MBC) values indicate that the essential oils from the plants analyzed had bactericidal effects on all strains tested and are similar to the minimal inhibitory concentration (MIC) values.@*Conclusion, significance and impact of study@#The high antibacterial properties of these medicinal plants, against bacteria isolated from sheep’s milk, provide an opportunity to use these medicinal plants in the breeding sector, as additives and preservatives in the dairy industry.

Milk from different species on physicochemical and microstructural yoghurt properties / Influência do leite de diferentes espécies nas propriedades físico-químicas e micro estruturais do iogurte

ABSTRACT: The aim of the present research was to evaluate differences in chemical properties and physical structure of yoghurt produced with milk from different species (sheep, cow, and goat). For each trial, whole raw sheep (S), cow (C), and goat (G) milk were used to manufacture 4L of yoghurts (Y) from each species (SY, CY, and GY, respectively). The SY demonstrated the greatest (P<0.05) values of total solids, protein, and lipid contents, reflecting on greater (P<0.05) firmness, apparent viscosity and water-holding capacity, and lower (P<0.05) syneresis index than CY and GY. Consequently, SY exhibited a more compact microstructure and homogeneous matrix with fewer pores. Furthermore, CY and GY microstructure contained a greater number of pores, which exhibited greater size heterogeneity than SY. Therefore, based on the evaluated physicochemical and microstructural properties of yoghurt, SY demonstrated the most desirable parameter values for dairy industry representing an alternative substitution for cow's milk yogurt.

RESUMO: O objetivo da presente pesquisa foi avaliar as diferenças nas propriedades químicas e na estrutura física do iogurte produzido com leite de diferentes espécies (ovinos, bovinos e caprinos). Para cada experimento, leite de ovelha cru (S), vaca (C) e cabra (G), foram usados para fabricar 4L de iogurtes (Y) de cada espécie (SY, CY e GY, respectivamente). O SY demonstrou os maiores (P<0,05) valores de sólidos totais, proteína e conteúdo lipídico, refletindo em maior (P<0,05) firmeza, viscosidade aparente e capacidade de retenção de água e menor (P<0,05) índice de sinérese do que CY e GY. Consequentemente, o SY exibiu uma microestrutura mais compacta e uma matriz homogênea com menos poros. Além disso, a microestrutura CY e GY continha um maior número de poros, que exibiam maior heterogeneidade de tamanho do que o SY. Portanto, com base nas propriedades físico-químicas e micro estruturais avaliadas do iogurte, o SY demonstrou os valores de parâmetros mais desejáveis para a indústria de laticínios, representando uma alternativa de produto adequada aos iogurtes à base de leite de vaca.

Isolation, enumeration, molecular identification and probiotic potential evaluation of lactic acid bacteria isolated from sheep milk

Lactic acid bacteria species were molecularly identified in milk from Lacaune, Santa Inês and crossbred sheep breeds and their in vitro probiotic potential was evaluated. The species identified were Enterococcus faecium (56.25%), E. durans (31.25%) and E. casseliflavus (12.5%). No other lactic acid bacteria species, such as lactobacilli, was identified. Most of the isolated enterococci were resistant to gastric pH (2.0) and to 0.3% oxgall. All tested enterococci were resistant to ceftazidime, oxacillin and streptomycin and sensible to clindamycin, erythromycin and penicillin. The resistance to ciprofloxacin, gentamicin, tetracycline and vancomycin varied among tested species. All tested enterococci strongly inhibited (P<0.05) Escherichia coli and Listeria monocytogenes, moderately inhibited E. faecalis and Staphylococcus aureus and did not inhibit Pseudomonas aeruginosa, Salmonella enterica var. Typhimurium and also one E. durans sample isolated from sheep milk. Four samples of E. faecium, one of E. durans and one of E. casseliflavus presented the best probiotic potential...

Espécies de bactérias ácido-lácticas foram identificadas em nível molecular em leite das raças ovinas Lacaune, Santa Inês e suas mestiças, e o seu potencial probiótico in vitro foi avaliado. As espécies identificadas foram Enterococcus faecium (56,25%), E. durans (31,25%) e E. casseliflavus (12,5%). Nenhuma outra espécie de bactéria ácido-láctica, como Lactobacillus sp., foi identificada. A maioria dos enterococos isolados foi resistente ao pH gástrico (2.0) e a 0,3% de oxgall. Todos os enterococos testados foram resistentes à ceftazidima, oxacilina e estreptomicina e sensíveis à clindamicina, eritromicina e penicilina. A resistência à ciprofloxacina, gentamicina, tetraciclina e vancomicina variou entre as amostras. Todos os enterococos testados inibiram fortemente (P<0,05) Escherichia coli e Listeria monocytogenes, inibiram moderadamente E. faecalis e Staphylococcus aureus e não inibiram Pseudomonas aeruginosa, Salmonella enterica var. Typhimurium e uma amostra de E. durans isolada de leite de ovelha. Quatro amostras de E. faecium, uma de E. durans e uma de E. casseliflavus apresentaram o melhor potencial probiótico...

Rendimento de coalhada obtida a partir de leite fresco, resfriado e congelado de ovelhas da raça Lacaune e caracterização física do soro obtido / Curd yeld obtained from fresh, cooled and frozen Laucane sheep milk and physical characteristics of the obtained whey

A composição do leite, que pode ser afetada pelo resfriamento ou congelamento, é determinante para o rendimento na fabricação de queijos, sendo um parâmetro muito importante em termos econômicos. O presente estudo teve como objetivo avaliar o efeito do resfriamento e do congelamento do leite, durante sete dias, sobre o rendimento da coalhada produzida a partir de leite de ovelha e sobre as características físicas do soro obtido. Entre janeiro e dezembro de 2011, foram coletadas mensalmente amostras de leite de ovelha, diretamente dos tanques de resfriamento. Uma parte foi submetida à análise no mesmo dia, denominada leite fresco, e as restantes armazenadas até sete dias, uma em refrigeração (5°C - leite resfriado) e outra em congelamento doméstico (-4°C - leite congelado). Determinou-se o rendimento da coalhada e densidade, pH e acidez titulável do soro obtido. Verificou-se diferença significativa (P<0,05) no rendimento da coalhada entre os tratamentos aplicados, sendo que o rendimento obtido com leite resfriado (3,64±0,34L kg-1) e congelado (3,18±0,23L kg-1) não apresentaram diferenças com o de leite fresco (3,38±0,22L kg-1), porém estes tratamentos diferiram entre si. A densidade média do soro obtido (1,025g mL-1) não apresentou diferenças entre os tratamentos aplicados. O pH e acidez titulável do soro foram semelhantes nos tratamentos de leite fresco e congelado, havendo diferenças (P<0,05) com o soro de leite resfriado, que apresentou-se mais ácido. Embora o soro da coalhada obtida a partir de leite resfriado apresente-se mais ácido, o resfriamento e o congelamento do leite ovino, por um período de sete dias, não afetam o rendimento na fabricação de queijos e o soro obtido não apresenta diferença de densidade entre os tratamentos aplicados.

Milk composition that can be affected by cooling or freezing is crucial for the performance of chesese making, and it is an important parameter in economic terms. The objective of this study was to evaluate, during 7 days, the effect of milk cooling and freezing on the yield of the curd produced with the sheep milk and on the physical characteristics of the obtained whey. Between January and December 2011 samples of the sheep milk were collected every month, directly from the bulk tanks. A part of it was subject to analysis in the same day, and the rest was stored for up to 7 days. One of the samples was kept under refrigeration (5°C - cooled milk) and another was kept in a domestic freezer (-4°C - frozen milk). The yield and density of the curd, pH and titratable acidity of the obtained whey was determined. The treatment applied showed a significant difference (P<0.05) in the yield of the curd, whereas the yield obtained with the cooled milk (3.64±0.34L kg-1) and the frozen milk (3.18±0.23L kg-1) showed no differences with the fresh milk (3.38±0.22 L kg-1), but these treatments were not the same. The average density of the obtained whey (1.025g mL-1) did not present differences between the applied treatments. The whey pH and titratable acidity were similar in both fresh and frozen milk treatments, but there was a difference (P<0.05) with the cooled milk, which had a higher acidity. Even though the whey of the curb obtained from the cooled milk is more acid, the cooling and freezing of the sheep milk, for a period of 7 days, do not affect the yield in cheese making, and the obtained whey does not present density differences between the applied treatments.