Predicting the Nutritional and Rancidity Properties of Dehydrated Catfish (Clarias gariepinus ) Using Response Surface Methodology.

Catfish (Clarias gariepinus), the most popular fish species cultivated in Nigeria is rich in nutrients but highly perishable thus, it requires processing for preservation. In order to determine the optimal dehydration parameters, the combined effects of brine concentration [3.0, 6.0, and 9.0% (w/v)], brining time (30, 60, and 90 min), and drying temperature (90, 110, and 130°C) were investigated to predict the nutritional and rancidity properties of the dehydrated catfish using response surface methodology (RSM). The study showed that brine concentration, drying temperature, and the interaction of brine concentration and brining time significantly (P<0.05) influenced the nutritional and rancidity properties of dehydrated catfish. However, the optimal process parameters: 7.83% brine, 90 min, and 110.38°C produced dehydrated catfish of high protein content (60%), low moisture (6.0%), free fatty acid (1.2%), thiobarbituric acid (0.10 mg malondialdehyde/kg), and total volatile nitrogen (10.0 mg nitrogen/100 g) with no detectable levels of peroxide value, indicating good nutritional quality and lower lipid oxidation for shelf stability. RSM models with a high range of predictive R2 (77~88%) were obtained at the set conditions showing the RSM potential as a feasible tool in this regard. The dehydration technique employed in this study is effective for high nutrient retention, especially the protein content, which could ameliorate the problem of malnutrition especially where fresh fish is not accessible, simple in operation and economical to encourage commercial applications with a potential for food security.

Proximate, Phytochemical, and In Vitro Antimicrobial Properties of Dried Leaves from Ocimum gratissimum.

Ocimum gratissimum is a common plant in the tropics and has been used in food and medicine. Its usage in food and medicine could be attributed to its phtyochemical and antimicrobial properties. In this study we investigated the proximate, phytochemical, and antimicrobial attributes of air dried leaves of O. gratissimum. The aqueous extract was found to contain phtyochemicals with alkaloid and saponin present in appreciable amounts. The proximate analysis (crude protein and crude fibre content were 15.075% and 17.365%, respectively) showed that the leaf could be a good source of protein and fibre. The aqueous ethanolic extract of the leaf exhibited activity against a wider range of organisms when compared to the aqueous extract at the investigated concentrations. Aqueous ethanolic extracts of O. gratissimum leaf was active against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus cereus and the aqueous extract of the leaf was active against P. aeruginosa.

Enhancing Sensory Perception of Plant Based Nutraceutical Drinks by Combining Plants from Different Sources: A Preliminary Study of Tea and Ginger Blend.

Tea-ginger drink was selected for evaluation due to its nutraceutical potential. Panelists rated preference for drinks prepared from tea, ginger, and tea+ginger powder for colour, taste, and aroma. The obtained data were evaluated using analysis of variance, principal component analysis, and agglomerative hierarchical clustering. Also the colour preference scores were evaluated against instrumental colour measurements. The ginger drink had lower rating for colour preference and the tea drink had lower ratings for aroma and taste preference. However, the tea-ginger drink led to enhanced colour, aroma, and taste ratings. The colour preference was found to have highest correlation coefficient with the hue and chroma of the drinks [r(58)=-0.583, P<0.05 and r(58)=0.566, P<0.05]. This study suggests that a sensory quality deficiency in a particular plant based drink could be compensated for by blending the drink with another plant based drink. This approach could help improve the uptake of plant based nutraceutical drinks.

Multiresponse Optimization and Prediction of Antioxidant Properties of Aqueous Ginger Extract.

The influence of extraction temperature, powder concentration, and extraction time on the antioxidant properties of aqueous ginger extract was investigated. The possibility of estimating the antioxidant properties of the extract from its absorbance and colour properties was also investigated. Results indicated that powder concentration was the most significant factor to consider in optimizing antioxidant extraction. However, temperature and time still influenced the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity while extraction temperature influenced the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of the extract. Using the total phenol content, total flavonoid content, ABTS radical scavenging activity, and DPPH radical scavenging activity of the extract, the multiresponse optimization condition for extraction of antioxidant based on the experimental range studied is 96°C, 2.10 g/100 mL, and 90 min. The absorbance of the ginger extract at 610 nm could be exploited for rapid estimation of its total flavonoid and polyphenol with a R2 of 0.713 and 0.753, respectively.

Optimization and prediction of antioxidant properties of a tea-ginger extract.

A response surface approach was used to investigate the effects of temperature, concentration, and time on the antioxidant properties (total flavonoid (TF), total phenol (TP), peroxide scavenging activity (PS), iron chelating activity (IC), DPPH radical-scavenging ability (DPPH), ABTS assay (ABTS)) of aqueous extract of tea-ginger (2:1) powder. Color indices, pH, and redox potential of the tea-ginger powder were also measured and used as independent variables for the prediction of antioxidant properties of the extract using ordinary least square (OLSR), principal component (PCR), and partial least square (PLSR) regression. The R (2) values for TP, TF, ABTS, and PS response surface models were 0.8873, 0.9639, 0.6485, and 0.5721, respectively. The OLSR, PCR, and PLSR were able to provide predictive models for DPPH, TP, and TF of the tea-ginger extract (P < 0.05). The PLSR gave the most parsimonious model with an R (2) of 0.851, 0.736, and 0.905 for DPPH, TP, and TF, respectively.