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| Author(s): |
Marina Padilha
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2013-05-28 |
| Examining board members: |
Susana Marta Isay Saad;
Gisele Monteiro de Souza
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| Advisor: | Susana Marta Isay Saad |
| Abstract | |
This study aimed to evaluate the survival of probiotic strains incorporated into petit-suisse cheese in the product stored for up to 28 days and under in vitro gastrointestinal tract simulated resistance assay, using culture-independent and culture-dependent methods. Furthermore, sensory acceptability and instrumental texture of the cheeses studied were evaluated. Experimental design involved the evaluation of three trials of petit-suisse cheese, as follows: PC = probiotic cheese (with the ABT-4 culture, containing Lactobacillus acidophilus LA-5, Bifidobacterium animalis subsp. lactis BB-12, and Streptococcus thermophilus, as starter culture), SC = synbiotic cheese, containing both the probiotics and the prebiotics (with the ABT-4 culture + inulin and fructooligosaccharides), and CC = control cheese (containing only the starter culture of Streptococcus thermophilus). Cheeses were stored at 4°C and the microbial counts in the products, as well as the in vitro survival assays were conducted weekly up to the 28th day. The probiotic counts in the product and in the in vitro assays were conducted through culture-independent (qPCR) and dependent methods. Additionally, the presence of contaminants was monitored and the sensory acceptability and instrumental texture of the products were evaluated during storage at 4°C. The petit-suisse cheeses presented L. acidophilus LA-5 and B. animalis BB-12 populations above 7 log CFU/g, up to the 28th day of storage. For SC, a higher L. acidophilus LA 5 population stability during the shelf-life and a higher B. animalis BB-12 in vitro survival up to 14 days of storage (p < 0.05) were observed. BB-12 presented mean survival rates decreasing from 88.0% (day 1) to 59.6% (day 28) in SC and from 80.0% (day 1) to 59.8% (day 28) in PC. In contrast, for L. acidophilus LA-5, the mean survival rates decreased from 49.1% (day 1) to 36.8% (day 28) in SC and from 61.6% (day 1) to 39.2% (day 28) in PC, which presented higher survival rate on days 1 and 14 (p < 0.05). The addition of probiotics in petit-suisse cheese influenced texture parameters significantly, leading to decreased hardness (p < 0.05), which probably contributed for the higher acceptability scores of both cheeses supplemented with probiotics (> 5.9), compared to the control product (< 5.3). Additionally, there was a positive influence of the prebiotic mixture on the SC acceptability (score = 6.8) on day 21 of storage (p < 0.05). Regarding the methods used for the enumeration of microorganisms, the results for the qPCR and the conventional method were quite similar. However, a trend towards overestimating microbial populations with the qPCR method was observed. For the in vitro survival assays, we observed similar results for the qPCR method with Propidium Monoazide (PMA) and the conventional method for B. animalis subsp. lactis BB-12 and a Pearson correlation coefficient of 0.92, whereas for L. acidophilus LA-5, the results were promising, especially in the quantification of viable, but not cultivable cells. The results suggest that the synbiotic cheese was the most favorable in terms of stability and probiotics survival, besides presenting the highest acceptance at 21 days of storage. Regarding quantification methods, molecular techniques have proved to be more suitable, particularly with PMA, but an optimization is required. (AU) | |
| FAPESP's process: | 11/05203-1 - Probiotic and symbiotic petit-suisse: technological features and use of culture-independent methods for the evaluation of probiotic survival in the product and in vitro essays |
| Grantee: | Marina Padilha |
| Support Opportunities: | Scholarships in Brazil - Master |