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Raw banana juice is turbid, viscous and gray in colour. This work was initiated to optimize the enzymatic clarification process of banana juice using response surface methodology. Banana juice was treated with pectinase at various enzyme concentrations (0.01-0.1%), temperatures (30-50°C) and time (30-120 min) of treatment. The effect of these enzyme treatments on filterability, clarity, turbidity and viscosity of the juice were studied by employing a second order central composite design. The coefficient of determination, R 2 values for filterability, clarity, turbidity and viscosity were greater than 0.900. Statistical analysis showed that filterability, clarity, viscosity and turbidity were significantly (p < 0.05) correlated to enzyme concentration, incubation temperature and incubation time. Enzyme concentration was the most important factor affecting the characteristics of the banana juice as it exerted a highly significant influence (p < 0.01) on all the dependent variables. An increase in time and/or concentration of enzyme treatment was associated with an increase in filterability and clarity, and decrease in turbidity and viscosity. Based on response surface and contour plots, the optimum conditions for clarifying the banana juice were: 0.084% enzyme concentration, incubation temperature of 43.2°C and incubation time of 80 min.

Antioxidative activity and total phenolic compounds of root, leaf and petiole of four accessions of Centella asiatica (L.) Urban, namely CA 01, CA 05, CA 08 and CA 11, were evaluated. Antioxidative activity of the extracts was measured using the ferric thiocyanate (FTC) method and thiobarbituric acid (TBA) test. The antioxidative activities were then compared with that of α-tocopherol (natural antioxidant) and butylated hydroxytoulene or BHT (synthetic antioxidant). The results showed that CA 01 and CA 05 had the highest antioxidative activities among the accessions tested. Results also showed that both leaf and root of C. asiatica had high antioxidative activity, which was as good as that of α-tocopherol. The total phenolic content, determined according to the Folin-Ciocalteu method, varied from 3.23 to 11.7 g/100 g dry sample, and showed strong association (r2=0.90) with antioxidative activity. The results suggest that phenolic compounds are the major contributors to the antioxidative activities of C. asiatica.

Effect of Arabic gum, xanthan gum and orange oil contents on ζ-potential, conductivity, stability, size index and pH of orange beverage emulsion ABSTRACTThe main and interaction effects of main emulsion components namely Arabic gum content (13-20%, w/w, x1), xanthan gum content (0.3-0.5%, w/w, x2) and orange oil content (10-14%, w/w, x3) on beverage emulsion characteristics were studied using the response surface methodology (RSM). The physicochemical properties considered as response variables were: ζ-potential (Y1), conductivity (Y2), emulsion stability (Y3), size index (Y4) and pH (Y5).The results indicated that the response surface models were significantly (p < 0.05) fitted for all response variables studied. In contrast with ζ-potential and pH, the independent variables had the most significant (p < 0.05) effect on size index. Regression models describing the variations of the responses variables showed high coefficient of determination (R2) values ranging from 0.866 to 0.960. The main effect of Arabic gum followed by its interaction with orange oil was observed to be significant (p < 0.05) in most of response surface models. Therefore, the concentration of Arabic gum should be considered as a critical variable for the formulation of orange beverage emulsion in terms of the emulsion characteristics studied.The overall optimum region resulted in a desirable orange beverage emulsion was predicted to be obtained by combined level of 10.78% (w/w) Arabic gum, 0.24% (w/w) xanthan gum and 12.43% (w/w) orange oil. No significant (p > 0.05) difference was found between the experimental and predicted values, thus ensuring the adequacy of the response surface models employed for describing the changes in physicochemical properties as a function of main emulsion component contents.

The physico‐chemical characteristics of roselle from Malaysia were studied. The parameters analysed included size, weight, pH, titratable acidity, soluble solids, anthocyanin contents, organic acids and sugars. Succinic and oxalic acids were the predominant organic acids found in roselle while glucose was the major sugar present. The present study was also conducted to determine and quantify the most biologically effective natural antioxidants present in roselle. Ascorbic acid, β‐carotene and lycopene, were separated, identified and quantified by HPLC. The amounts of ascorbic acid, β‐carotene and lycopene contents were 141.09mg/100g, 1.88mg/100g and 164.34μg/100g, respectively. The individual anthocyanin in roselle was characterised by TLC and HPLC. Delphinidin‐3‐sambubioside and cyanidin‐3‐sambubioside were the main anthocyanin present in roselle.