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| Author(s): |
Natalia Silva Matias
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2016-02-02 |
| Examining board members: |
Susana Marta Isay Saad;
Helena Maria André Bolini Cardello;
Inar Alves de Castro;
Cynthia Jurkiewicz Kunigk;
Carmen Silvia Favaro Trindade
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| Advisor: | Susana Marta Isay Saad |
| Abstract | |
The aim of this study was to assess the effect of the total or partial replacement of milk (M-x1) by soy extract (S-x2), and/or WPI combined with inulin (PI-x3) in synbiotic apple ice cream formulations on the viability and survival of L. acidophilus La-5 and B. animalis Bb-12 through in vitro simulated gastrointestinal (GI) conditions and to monitor cells morphological changes during gastrointestinal stress in one of the formulations, as well as investigating technological features (overrun, meltdown rate, instrumental hardness) and sensory acceptability. For this purpose, an experimental design for simple mixtures (simplex-centroid) was used including an axial point, using different proportions of x1, x2, x3. Eight formulations of synbiotic apple ice cream were studied during frozen storage for up to 84 days. The ice creams showed to be satisfactory vehicles for La-5 and Bb-12 (populations around 7.5 log cfu/g), even after the whole storage period (84 days/-18°C). In all formulations, the propidium monoazide qPCR (PMA-qPCR) analysis evidenced that probiotics could resist to the in vitro GI assay, with significant survival levels, achieving survival rates exceeding 50%. Additionally, scanning electron microscopy images evidenced cells with morphological differences, suggesting physiological changes in response to the induced stress during the in vitro assay. A linear and a special cubic models were obtained for the overrun and hardness parameters showing that factors milk, soy extract, and whey protein isolate + inulin strongly influenced these technological parameters. However meltdown rate was slightly affected by the factors studied. The special cubic model showed that the binary (S-PI) and tertiary (M-S-PI) interactions resulted in higher hardness values. For this specific parameter, combination of the factors is recommended to be 3.7% milk, 1.3% soy extract, and 5.0% PI. The sensory acceptability mean scores ranged from 5.6 to 8.0. The overall acceptability of the ice cream produced only with PIn was lower when compared to milk based ice cream (M), even though a high frequency of scores was observed in the scale area comprising the opinions \"liked slightly\" (score 6) and \"liked extremely\" (score 9) for all ice cream formulations evaluated. Although all formulations provided resistance to the probiotic strains under GI stress, the variation found in La-5 and Bb-12 survival suggests that GI tolerance is indeed affected by the choice of the food matrix. The results also showed that, besides being a nutritious food, the ice cream formulations that had the partial replacement of milk powder could assure consumers a functional product with low content of lactose, whereas ice creams with no milk powder offer a lactose-free functional food. (AU) | |
| FAPESP's process: | 11/12981-0 - Development of synbiotic apple ice-cream and effect of ingredients on probiotics survival in the product and in vitro, using culture-independent techniques |
| Grantee: | Natalia Silva Matias |
| Support Opportunities: | Scholarships in Brazil - Doctorate |