Sabrina Cox

An Assessment of the Antioxidant and Antimicrobial Activity of Six Species of Edible Irish Seaweeds

Six species of edible Irish seaweeds; Laminaria digitata, Laminaria saccharina, Himanthalia elongata, Palmaria palmata, Chondrus crispus and Enteromorpha spirulina were screened for potential bioactivity. Extraction of secondary metabolites was carried out using different solvents to determine antioxidant and antimicrobial properties of the dried extracts. The total phenolic contents of dried methanolic extracts were significantly different (p < 0.05). H. elongata exhibited highest phenolic content at 151.3 mg GAE/g of seaweed extract and also had the highest DPPH scavenging activity (p < 0.05) with a 50% inhibition (EC50) level at 0.125μg/ml of extract. H. elongata also had the highest total tannin and total flavonoid contents (p < 0.05) of 38.34 mg CE/g and 42.5 mg QE/g, respectively. Antimicrobial activity was determined using a microtitre method which allowed detection of bacterial growth inhibition at low levels. All methanolic seaweed extracts inhibited the food spoilage and food pathogenic bacteria tested; Listeria monocytogenes, Salmonella abony, Enterococcus faecalis and Pseudomonas aeruginosa, except C. crispus extracts. It was found that dried methanolic extracts of red and green seaweeds had significantly lower antimicrobial activity than the brown species; H. elongata had the highest antimicrobial activity with up to 100% inhibition. In the studied work, the antimicrobial activity of red and green seaweed extracts significantly increased when ethanol and acetone were used as extraction solvents (p < 0.05). Inhibition of E. faecalis with C. crispus extracts increased from 39.28 to 100% when ethanol and acetone were applied as solvents.

Growth Inhibition of Common Food Spoilage and Pathogenic Microorganisms in the Presence of Brown Seaweed Extracts

The possibility of using extracts from brown seaweed, Himanthalia elongata, as a natural antimicrobial agent for food preservation is presented. The effect of different concentrations of seaweed extract on the growth kinetics of four common food spoilage (Pseudomonas aeruginosa and Enterococcus faecalis) and food pathogenic microorganisms (Listeria monocytogenes and Salmonella abony) was examined. Seaweed extract at a concentration of 6% inhibited the growth of all four of the studied organisms. Lower concentrations of seaweed extract prolonged the lag phase and reduced both the exponential growth rate and final population densities of the culture. Suitability of three kinetic models, Baranyi–Roberts, modified Gompertz and logistic, for describing the growth/survival of organisms in the presence of different concentrations of the extract, was evaluated. Root mean square error (RMSE) and correlation coefficient (R2) were used to evaluate the model performance. The R2 value was greater than 0.95 for most of the cases indicating that the models could provide a good fitting to the experimental data. The RMSE and residual sum of squares were very low for all the three models, and no significant difference was observed in the goodness of fit between the three models as indicated by the F test.

Incorporation of Himanthalia Elongata Seaweed to Enhance the Phytochemical Content of Breadsticks Using Response Surface Methodology (RSM)

Optimization of incorporating seaweed into breadsticks was carried out using response surface methodology (RSM). Ten formulations of breadsticks were processed by varying concentrations of seaweed (X1 = 5 to 15% of overall flour concentration) and white flour (X2 = 10 to 30% of overall flour concentration) using a central composite design. The remaining flour concentrations were comprised of wholemeal flour. Predicted models were found to be significant (P < 0.05) for total phenolic content (TPC), DPPH radical scavenging activity, texture and color. Predicted values for each of the responses were in good agreement with the experimental values. Seaweed concentration had most significant effect on phytochemical constituents of the breadsticks with TPC and DPPH activity maximized when 17.07% H. elongata was incorporated into the flour (P < 0.05). An acceptable edible texture and color of breadsticks was also achieved at this concentration. Multiple response optimization demonstrated that phytochemical content of H. elongata breadsticks may be maximized with dried seaweed and white flour concentrations of 17.07 and 21.89%, respectively, in the total flour. Total dietary fiber increased from 4.65 to 7.95% in the optimized sample, representing a 43.65% increase as compared to the control (P < 0.05). A sensory panel evaluated the acceptability of the seaweed breadsticks, as compared to the control, in terms of aroma, color, texture, taste and overall acceptability. There was no significant difference (P > 0.05) between the seaweed breadsticks and the control which shows that such fiber-rich seaweed bakery products are acceptable to consumers and have potential of increasing seaweed consumption among non-seaweed consumers.

Application of Baranyi function to model the antibacterial properties of solvent extract from Irish York cabbage against food spoilage and pathogenic bacteria

Cabbage is a rich source of a number of bioactive compounds such as flavonoids, glucosinolates and their breakdown products which may have antibacterial, antioxidant and anticancer properties. Outer green leaves of York cabbage were extracted with 60% methanol, ethanol or acetone. Antibacterial activities of vacuum dried crude extracts were estimated against a number of Gram-positive and Gram-negative food spoilage and food pathogenic bacteria. The crude extracts showed a broad spectrum of antibacterial activities but 60% methanol extract exhibited the highest antibacterial effect. Complete growth inhibition for Listeria monocytogenes was achieved with an extract concentration of 1.4%, whereas a two-fold concentration was required to achieve a reduction of 75% and 64% for Salmonella abony and Pseudomonas aeruginosa, respectively. For Enterococcus faecalis methanolic extract showed a weak inhibition only (31%). The lower concentrations of methanolic extract from York cabbage prolonged the lag phase and reduced both the exponential growth rate and final population densities of the culture. Survival of the micro-organisms in presence of methanolic extract was mathematically modeled using Baranyi model equations.

Application of response surface methodology for studying the influence of hydrothermal processing on the phytochemical constituents of Irish edible brown seaweed

Abstract We used response surface methodology to investigate the effect of time and temperature of hydrothermal processing (blanching) on the phytochemical content, texture and colour of a semi-dried brown seaweed (Himanthalia elongata). A central composite design was employed with a hydrothermal processing time of 10–30 min and temperature of 60–90°C. Predicted models were found to be significant for total phenolic content, 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, total flavonoids, total condensed tannins, texture and colour. The predicted values for each of the responses were in good agreement with experimental values. Processing time had the most significant effect on phytochemical constituents of H. elongata. An acceptable edible texture and colour of seaweed was also achieved during the blanching procedure. Thus, central composite design and response surface methodology can be used to model phytochemical content, texture and colour of H. elongata while minimising the number of experiments required. Multiple response optimisation demonstrated that the phytochemical content of H. elongata may be maximised by blanching for 20.4 min at 80.5°C.

An Investigation of the Bioactivity of Irish Seaweeds and Potential Applications as Nutraceuticals.

...................................................................................................................... ii Declaration ................................................................................................................. iv Acknowledgements...........................................................................vi Abbreviations list ................................................................................................... viii Table of