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Master's Dissertation
DOI
10.11606/D.11.2002.tde-16072002-150013
Document
Author
Full name
Adriana Furlan Martin
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 2002
Supervisor
Committee
Horii, Jorge (President)
Lacerda, Tais Helena Martins
Oliveira, Antonio Joaquim de
Title in Portuguese
Armazenamento do iogurte comercial e o efeito na proporção das bactérias lácticas.
Keywords in Portuguese
armazenamento de alimento
bactéria láctica
iogurte
Abstract in Portuguese
Os objetivos desta pesquisa foram verificar a proporção entre Streptococcus salivarius subsp. thermophilus e Lactobacillus delbrueckii subsp. bulgaricus em iogurte natural, comercial e os efeitos do armazenamento (dentro do prazo de validade) sobre a proporção das bactérias lácticas componentes do produto, o pH, a acidez e a presença de microrganismos psicrófilos. As amostras de iogurte foram adquiridas por trinta dias consecutivos, num total de 30 amostras, de um mesmo lote, e submetidas às análises de pH, acidez titulável e contagem, em meio TPPY - Eriocromo-ágar, de Lactobacillus sp. e Streptococcus sp. (em UFC/mL). Os resultados mostraram que, durante o armazenamento, ocorreram variações nas características físico-químicas do iogurte, como pH que variou de 4,36, inicialmente, para 4,18, e acidez titulável que variou de 0,73% (em ácido láctico) para 1,17%. Streptococcus salivarius subsp. thermophilus e Lactobacillus delbrueckii subsp. bulgaricus foram encontrados na proporção de 2:1, respectivamente, diminuindo para 1:1 devido, provavelmente, às variações de pH e acidez titulável durante o armazenamento, por trinta dias, que corresponde ao prazo de validade.
Title in English
Effect of the period of storage on the proportion of lactic bacteria in commercial yogurt.
Keywords in English
lactic bacteria
storage of food
yogurt
Abstract in English
The objectives of this research were to verify the proportion of Streptococcus salivarius subsp. thermophilus to Lactobacillus delbrueckii subsp. bulgaricus in commercial natural yogurt and evaluate the effect of the period of storage in some characteristics of the product, such as proportion of lactic bacteria, pH, acidity and presence of psychrophiles microorganisms. Yogurts from the same lot were analysed during a period of 30 consecutive days, within the best before date. One sample a day was analysed for pH, acidity and bacterial count (c.f.u./ml) of Streptococcus sp. and Lactobacillus sp. in broth TPPY-Eriochrome-agar. Results indicated that significant changes on physical-chemical characteristics of the yogurt occured during the storage of the product. The pH decreased from 4.36 to 4.18 and the acidity increased from 0.73% (lactic acid) to 1.17% during the period of storage. The proportion of Streptococcus salivarius subsp. thermophilus to Lactobacillus delbrueckii subsp. bulgaricus during the period of storage varied from 2:1 to 1:1, respectively, probably because of the variations of pH and acidity during these 30 days.
 
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Publishing Date
2002-08-07
 
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