The present work was conducted to investigate the influence of main emulsion components, namely Arabic gum (7-13% w/w), xanthan gum (0.1-0.3% w/w) and orange oil (6-10% w/w) contents on physical stability, viscosity, cloudiness and conductivity of orange beverage emulsion. In this study, 20 orange beverage emulsions were established based on a three-factor central composite design (CCD) involving 8 factorial points, 6 axial points and 6 center points. The main objective of the present study was to determine an optimal concentration level of main emulsion components leading to an optimum orange beverage emulsion with desirable physicochemical properties. In general, all response surface models were significantly (p<0.05) fitted for describing the variability of physical stability, viscosity, conductivity and cloudiness as a nonlinear function of the content of main emulsion components. More than 84% of the variation of physicochemical properties of orange beverage emulsion could be explained as a function of the content of the main beverage emulsion components. In general, the orange oil content appeared to be the most significant (p<0.05) factor influencing all emulsion characteristics studied except for conductivity. From the optimization procedure, the overall optimal region leading to the desirable orange beverage emulsion was predicted to be achieved by the combined level of 13% (w/w) Arabic gum, 0.22% (w/w) xanthan gum and 10% (w/w) orange oil. (C) 2008 Elsevier Ltd. All rights reserved.

The influence of main emulsion components namely Arabic gum (13-20% w/w), xanthan gum (0.3-0.20% w/w) and orange oil (10-14% w/w) on semi-quantitative headspace analysis of target volatile flavor compounds released from a model orange beverage (diluted orange beverage emulsion) was evaluated by using a three-factor circumscribed central composite design (CCCD). For optimization procedure, the peak area of 13 volatile flavor compounds (i.e. ethyl acetate, alpha-pinene, ethyl butyrate, beta-pinene, 3-carene, myrcene, limonene, gamma-terpinene, octanal, decanal, linalool, neral and geranial) were considered as response variables. The response surface analysis exhibited that the significant (p < 0.05) second-order polynomial regression equations were successfully fitted for all response variables except for ethyl butyrate. A satisfactory coefficient of determination (R-2) ranged from 0.831 to 0.969 (>0.8) was obtained for the response variables studied. No significant (p > 0.05) lack of fit was indicated for the reduced models except for the models fitted for limonene and linalool. This observation confirmed an accurate fitness of the reduced response surface models to the experimental data. The multiple response optimizations indicated that an orange beverage emulsion containing 15.87% (w/w) Arabic gum, 0.5% (w/w) xanthan gum and 10% (w/w) orange oil was predicted to provide the minimum overall flavor release. (c) 2007 Elsevier Ltd. All rights reserved.

Optimization conditions of Lipozyme RM IM lipase esterification of capric and stearic acids with glycerol for the production of medium- and long-chain triacyglycerols (MLCT) fat suitable for food applications such as margarine and shortening were investigated. Response surface methodology (RSM) was applied to model and optimize the reaction conditions, namely, the reaction time (8-24 h), enzyme load (5-15 wt.%), and fatty acids/glycerol ratio (3:1-4:1) and represented by Ti, En, and Sb, respectively. Best-fitting models were successfully established for both MLCT yield (R (2) = 0.9507) and residual FFA (R (2) = 0.9315) established by multiple regressions with backward elimination. Optimal reaction conditions were 13.6-14.0 h for reaction time, 7.9-8.0 wt.% for enzyme load, and 3:1 for fatty acids/glycerol molar ratio. Chi-square test showed that there were no significant (P > 0.05) differences between the observed and predicted values of both models. Refined MLCT fat blend had sufficient solid fat at room temperature and made it suitable to use as a hard stock in shortening and margarine production.

The possible relationships between the main emulsion components (namely, Arabic gum, xanthan gum, and orange oil) and the physicochemical properties of orange beverage emulsion were evaluated by using response surface methodology. The physicochemical emulsion property variables considered as response variables were emulsion stability, viscosity, fluid behavior, xi-potential, and electrophoretic mobility. The independent variables had the most and least significant (p < 0.05) effect on viscosity and xi-potential, respectively. The quadratic effect of orange oil and Arabic gum, the interaction effect of Arabic gum and xanthan gum, and the main effect of Arabic gum were the most significant (p < 0.05) effects on turbidity loss rate, viscosity, viscosity ratio, and mobility, respectively. The main effect of Arabic gum was found to be significant (p < 0.05) in all response variables except for turbidity loss rate. The nonlinear regression equations were significantly (p < 0.05) fitted for all response variables with high R-2 values (> 0.86), which had no indication of lack of fit. The results indicated that a combined level of 10.78% (w/w) Arabic gum, 0.56% (w/w) xanthan gum, and 15.27% (w/w) orange oil was predicted to provide the overall optimum region in terms of physicochemical properties studied. No significant (p > 0.05) difference between the experimental and the predicted values confirmed the adequacy of response surface equations.

Solid-phase microextraction (SPME) coupled to gas chromatography has been applied for the headspace analysis (HS) of 12 target flavour compounds in a model orange beverage emulsion. The main volatile flavour compounds studied were: acetaldehyde, ethyl acetate, alpha-pinene, ethyl butyrate, beta-pinene, myrcene, limonene, gamma-terpinene, octanal, decanal, linalool and citral (neral plus geranial). After screening the fibre type, the effect of other HS-SPME variables such as adsorption temperature (25-55 degrees C), extraction time (10-40 min), sample concentration (1-100% w/w), sample amount (5-10 g) and salt amount (0-30% w/w) were determined using a two-level fractional factorial design (2(5-2)) that was expanded further to a central composite design. It was found that an extraction process using a carboxen-polydimethylsiloxane fibre coating at 15 degrees C for 50 min with 5 g of diluted emulsion 1% (w/w) and 30% (w/w) of sodium chloride under stirring mode resulted in the highest HS extraction efficiency. For all volatile flavour compounds, the linearity values were accurate in the concentration ranges studied (r(2) > 0.97). Average recoveries that ranged from 90.3 to 124.8% showed a good accuracy for the optimised method. The relative standard deviation for six replicates of all volatile flavour compounds was found to be less than 15%. For all volatile flavour compounds, the limit of detection ranged from 0.20 to 1.69 mg/L. Copyright (c) 2008 John Wiley & Sons, Ltd.