The agar RCPB pH5 has been considered a good alternative for counts of Bifidobacterium in yoghurt. However, during the refrigerated storage of yoghurt it is extremely difficult to count this microorganism due to the size of the colonies, which are so small they require the aid of a stereoscope to count them. Another agar, MRS-LP, has been also recommended for counts of Bifidobacterium in the presence of yoghurt bacteria. This study evaluated the supplementation of RCPB pH5 agar with dehydrated liver extract and the salts KH2PO4, K2HPO4, FeSO47H2O, MnSO4H2O and MgSO47H2O, aiming at improving the differentiation of Bifidobacterium in yoghurt after refrigerated storage, and also evaluated the selective count of Bifidobacterium in yoghurt using the agar MRS-LP. The agar MRS-LP presented the same cell recovery as non-fortified RCPB pH5 agar, used as a standard medium, thus being considered a good option for counts of Bifidobacterium in yoghurt. The fortified RCPB pH5 also presented the same recovery as the standard RCPB pH5 medium, however, the addition of dehydrated liver extract to the RCPB pH5 agar considerably increased the size of the Bifidobacterium colonies after refrigerated storage, making differentiation of the colonies much easier and reliable when compared to the standard non-fortified RPCP pH5. The addition of the salts (KH2PO4, K2HPO4, FeSO47H2O, MnSO4H2O and MgSO47H2O) had no influence on the performance of the RCPB pH5 agar.

Much attention has been paid to the use of Bifidobacterium sp. in yoghurts due to their excellent therapeutic and nutritional properties. However, in order to present health properties, it is recommended that each commercial product should indicate the minimum daily amount required for it to confer health benefit(s) based on in vitro and human studies. Besides the inherent low growth of Bifidobacterium sp in milk, there is a need for a reliable method for counting Bifidobacterium sp in the presence of yoghurt bacteria. This study evaluated the use of the media M-MRS, MRS-NNLP and RCPB pH5 aimed at counting the number of Bifidobacterium animalis subesp. lactis in the presence of Streptococcus thermophilus and Lactobacillus delbrueckii subsp bulgaricus after yoghurt fermentation. The M-MRS medium was not selective, allowing for the growth of L. delbrueckii subsp bulgaricus. MRS-NNLP medium presented a good selectivity for B. animalis Bb12 with a slight reduction in the cell count of this microrganism when compared it to the standard MRS medium in pure culture. MRS-NNLP medium was considered a good option to enumerate B. animalis Bb12 although the reduction found in pure culture due to the low difference between the counts. The medium RCPB pH5 presented differentiated growth of B. animalis Bb12 in relation to the yoghurt bacteria and a cell recovery equal to that of the standard MRS, being considered the best option to enumerate Bifidobacterium sp in the presence of yoghurt bacteria.

O objetivo desta pesquisa foi estudar a vida-de-prateleira de produto elaborado com garapa, parcialmente clarificadaestabilizada, e suco de maracujá (5%). A mistura foi adicionada de antioxidante, conservante e espessante em concentrações pré-estabelecidas. Após pasteurização, o produto foi resfriado, embalado em garrafas de polietileno tereftalato (PET) e armazenado sob refrigeração pelo período de um mês. Foram realizadas determinações microbiológicas (Contagem Padrão, Contagem de Bolores e Leveduras, Coliformes Totais e Fecais), físico-químicas (pH, ºBrix, acidez, relação Brix/Acidez, teor de ácido ascórbico, turbidez), e sensoriais. Os resultados da análise sensorial, considerados os mais relevantes para a pesquisa, indicaram que o produto (mistura de garapa parcialmente clarificadaestabilizada com suco de maracujá) pode ser elaborado e comercializado por até quinze dias sob refrigeração, pois as condições do processo permitiram a manutenção da qualidade microbiológica e sensorial. O teor de ácido ascórbico manteve-se em bom nível até o final da estocagem, com perda de apenas 20% em relação ao teor adicionado. PALAVRAS-CHAVE: CANA-DE-AÇÚCAR; MARACUJÁ; SUCO DE FRUTA; ANÁLISE SENSORIAL.

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