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dc.contributor.advisorOrellana-Feliciano, Lynette E.
dc.contributor.authorSanchez-Leger, Maickol R.
dc.description.abstractPsychrotrophic bacteria levels are one of the most important aspects when processing UHT milk, since these levels will have a negative impact on the shelf-life of the product. To study the incidence of psychrotrophic bacteria Pseudomonas spp. and the Bacillus cereus group, a total of 16 samples were taken: 8 samples of raw milk and 8 samples of milk processed by ultra high temperature (UHT). The bacterias were sampled in specific media for B. cereus group and Pseudomonas spp. In addition, sampling for psychrotrophic bacteria and total psychrotrophic bacteria were done. Alcohol test at 70%, 75%, 80% and 85% were performed in raw milk. No linear correlation was found between the psychrotrophic bacteria and the alcohol test. In 23% of the samples of raw milk, psychrotrophic bacteria levels were higher as 8 x106 CFU/ml. On the other hand, in samples of UHT milk the 63% was positive for the B. cereus group. All microorganisms identification were confirmed by real-time PCR, by identifying the pc-plc gene for B. cereus group and the CarA gene for Pseudomonas spp.en_US
dc.description.abstractLos niveles de bacterias psicrotróficas son uno de los aspectos más importantes a la hora de procesar leche por ultra alta temperatura, debido a que estos niveles van a tener un impacto negativo en el largo de vida útil del producto. Para estudiar la incidencia de bacterias psicrotróficas Pseudomonas spp. y del grupo Bacillus cereus, se tomaron un total de 16 muestras: 8 muestras de leche cruda y 8 muestras de leche procesada por ultra alta temperatura. Se realizó conteo de bacterias en medios específicos para el grupo B. cereus y Pseudomonas spp. También, se realizaron muestreos y conteos de otras bacterias psicrotróficas y bacterias psicrotróficas totales. Se realizaron pruebas de alcohol al 70%, 75%, 80% y al 85% en leche cruda. No se encontró correlación lineal entre las bacterias psicrotróficas y la prueba de alcohol. En el 23% de las muestras de leche cruda, los niveles de bacterias psicrotróficas se encontraban por encima de 8 x106 CFU/ml. Por otro lado, en las muestras de leche ultra alta temperatura, el 63% resultó positiva para el grupo B. cereus. Los resultados fueron confirmados mediante la reacción en cadena de la polimerasa en tiempo real, al identificar el gen pc-plc para el grupo B. cereus y el gen CarA para Pseudomonas spp.en_US
dc.subjectBacetrias psicrotróficasen_US
dc.subjectLeche UHTen_US
dc.subject.lcshRaw milk--Microbiologyen_US
dc.subject.lcshMilk--Heat treatmenten_US
dc.subject.lcshBacillus cereusen_US
dc.titleIncidencia de Pseudomonas spp. y grupo Bacillus cereus, en leche cruda y leche procesada por ultra alta temperaturaen_US
dc.rights.licenseAll rights reserveden_US
dc.rights.holder(c) 2019 Maickol Rafael Sanchez Legeren_US
dc.contributor.committeePlaza, María
dc.contributor.committeePonce, Leyda
dc.contributor.representativeRúa, Armando Science and Technology Programen_US
dc.contributor.collegeCollege of Agricultural Sciencesen_US
dc.contributor.departmentDepartment of Food Science and Technologyen_US

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