UPV Digital RepositoryUPV-DRUniversity of the Philippines Visayas
 

Masters Theses

Permanent URI for this collectionhttps://hdl.handle.net/20.500.14583/12

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2017 - 20193

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Committee Member: search.filters.committeemember.Nillos, Mae Grace G.

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    Antioxidative activities and lactic acid bacteria composition of fermented frigate tuna at different salt-fish ratio
    Ortizo, Rhessa Grace G. (University of the Philippines Visayas, 2019-06)
    The antioxidative activities and lactic acid bacteria (LAB) composition of fermented frigate tuna (Auxis thazard), locally known as tinabal, at different salt-fish ratios were investigated. Fresh frigate tuna were degutted and cleaned before the addition of salt at different salt-fish ratio (w/w), (1:3), (1:4), (1:5), (1:6), and then fermented at ambient temperature. Samples were taken on day 0, 1, 4, and 7 for the pH determination, total titratable acidity measurement, and the different antioxidant activity assays that include testing for radical scavenging activity of ABTS+, ferric reducing power, hydrogen peroxide and singlet oxygen radicals. Isolation of lactic acid bacteria (LAB) for bacterial identification was also conducted as well as the measurement of the degree of hydrolysis for peptide profile analysis of fermented product. Results show that the LAB viable count in the fermented samples increased, and the pH levels decreased with increasing % titratable acidity during the 7 days of fermentation. Isolated LAB and LAB-like species with gram positive, catalase negative, and non-spore forming properties were presumptively identified as Lactobacillus casei, Lactobacillus fermenti, Lactobacillus delbrueckii subsp. delbrueckii, Pediococcus pentosaceus, Leuconostoc spp., Enterococcus faecalis and Streptococcus spp. In this study, the free amino acids due to hydrolysis increased with fermentation time for the different salt-fish ratios and DH was influenced by the length of fermentation. The ethanolic extracts from F3 (1:6) sample showed strong antioxidative activities against ABTS+ radical, while sample Fl (1:4) showed high reduction of ferric ions, and sample F2 (1:5) exhibited high antioxidative activities against 1O2 radical which is the major cause of damage to bioactive compounds that leads to oxidative stress in fermented products. Results further revealed that tinabal could be a potential source of natural antioxidants for industrial uses. In addition, presence of important LABs in F2 (1:5) indicated that this fermented product could serve as a good source of LAB for applications to other fermented products as starters for improved product quality. In particular, tinabal fermented with F2 salt-fish ratio (1:5) has potential to be a functional food product that could benefit the consumers.
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    Isolation of Hyaluronic acid from yellowfin tuna (Thunnus albacares) eyeball
    Sumogod, Angeleca A. (College of Fisheries and Ocean Sciences, University of the Philippines Visayas, 2019-06)
    Hyaluronic acid (HA) is commonly extracted from terrestrial and bacterial sources. However, due to the risk associated with either animal- and/or bacterial- derived contaminants and the laborious production processes that tend to compromise the quality of HA, research studies have recently shifted to the exploration of the presence of this polymer in marine resources and the enhancement of the protocols for HA production. Hence, this study focused on the isolation of HA from yellowfin tuna eyeballs. Results of the study showed that the optimum conditions for the isolation of HA from yellowfin tuna eyeballs are as follows: pretreatment of the raw material (acetone, formaldehyde and sodium acetate solution) prior to water extraction and incubation of the mixture for 24 h; tissue hydrolysis for a maximum of 6 h; a 3% CPC: 3M NaCl concentration for recovery and fractionation; and the use of 1:3 v/v supernatant: ethanol ratio for alcoholic precipitation. These results are expected to help maximize the benefits of the utilization of the tuna processing wastes in the country. Likewise, these findings may open a new opportunity for more cost-effective production of a valuable bioactive compound from marine source.
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    Semiparametric and parametric modelling of vibro species abundance production system
    Dequito, Angel Queenee D. (College of Fisheries and Ocean Sciences, University of the Philippines Visayas, 2017-09)
    Vibrio species that cause white spot disease and vibriosis are known to be influenced by environmental factors. In this study, the changes in the abundance of presumptive Vibrio species from a biofloc shrimp production system with respect to physicochemical and biological parameters were evaluated. Parametric and nonparametric modelling techniques were used to identify and predict changes in Vibrio abundance in relation to alkalinity, ammonia, dissolved oxygen, nitrite, pH, salinity, temperature, transparency, and phytoplankton and zooplankton densities. Abundance was found to be highly correlated with alkalinity, pH, and phytoplankton density as revealed by both parametric and semiparametric models. Generalized additive model (GAM, a semiparametric model) is the best model based on Aikaike’s Information Criterion (AIC) values in which 41.2% of the variability in the dependent variable can be explained by the predictors compared to ordinary linear regression and negative binomial models (parametric models) with 16.04% and 14.5% respectively. Prediction on the abundance can help prevent bacterial diseases in shrimp as this will provide an insight to the farmer about when to and which water parameters or predictors can be controlled. Thus, it is important to consider the use of semiparametric modelling approach as a tool for fish health management and to prevent losses in aquaculture.