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Master's Dissertation
DOI
https://doi.org/10.11606/D.11.2019.tde-20191218-154131
Document
Author
Full name
Maria Isabel Franchi Vasconcelos Gomes
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 1989
Supervisor
Title in Portuguese
Alterações na qualidade do leite pasteurizado pela ação de lipase microbiana
Keywords in Portuguese
ATIVIDADE ENZIMÁTICA
LEITE PASTEURIZADO
LIPASE
MICROBIOLOGIA DE ALIMENTOS
MICRORGANISMOS
PSEUDOMONAS
QUALIDADE
Abstract in Portuguese
Leite pasteurizado, padronizado a 3% de gordura, adquirido em Botucatu, foi transferido assepticamente para um recipiente esterilizado e armazenado a 10°C durante 10 dias. Foram realizadas análises microbiológicas e determinação de ácidos graxos livres (AGL) a cada 48 horas, com o propósito de relacionar o teor de AGL e as contagens de psicrotróficos, lipolíticos e Pseudomonas sp. As amostras (9) foram coletadas a cada 20 dias, durante o período de março a agosto. Em 7 dos 9 experimentos realizados, as contagens de psicrotróficos e lipolíticos atingiram ou ultrapassaram o valor de 106 ufc/ml no 4º dia. A contagem de Pseudomonas sp atingiu 106 ufc/ml a partir do 4º dia em 4 experimentos, nos outros esse valor foi alcançado ou superado no 6º dia. Os valores de AGL excederam 1,3 ueq/ml ao 6º dia em 7 experimentos e nos outros 2, o mesmo valor foi observado no 4º e 8º dias de armazenagem. Observou-se uma correlação positiva e altamente significativa entre o aumento populacional dos três grupos microbianos e a concentração de AGL no leite. Nossos resultados indicam que o leite pasteurizado armazenado a 10°C permanece com níveis aceitáveis de lipólise até o 4º dia.
Title in English
Alterations in the quality of pasteurized milk by microbial lipase action
Abstract in English
Standardized and pasteurized milk, containing 3% of fat, acquired in Botucatu, was asepticaly transferred to a sterilized container and stored at 10°C incubator during 10 days. Microbiological analysis and free fat acids (FFA) determinations were proceeded each 48 hours in order to make correlations amoung the FFA grade and the psychrotrophic, lipolytic, and Pseudomonas counts. The samples (9) were collected each 20 days throughout the period march to august. In 7 of the 9 experiments performed, psychrotrophic and lipolytic bacterial counts reach 106 cfu/ml or higher a t the 4th day. The Pseudomonas counts was 106 cfu/ml in 4 experiments at the 4th day and in the others this value or higher were observed at the 6th day. The concentrations of FFA was higher than 1.3 ueq/ml in 7 experiments at the 6th days and in the other 2 experiments the same value was observed at the 4th and 8th day. Highly significative positive correlation was observed for the population increase of the three microbial groups and the concentration of FFA. Our results show that storage at 10°C keep pasteurized milk with acceptable lipolysis leveIs until the 4th day.
 
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Publishing Date
2019-12-19
 
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