Application of Differential Scanning Calorimetric Method for Assessing and Monitoring Various Physical and Oxidative Properties of Vegetable Oils

Differential scanning calorimetry (DSC) can be a powerful instrumental technique for analyzing oils and fats systems but has tended not to be well understood and used in the field of oils and fats. The main purpose of this project is to develop various techniques based on DSC to study the physical and chemical properties of vegetable oils. High-performance liquid chromatography (HPLC), gas-liquid chromatography (OLC), oxidative stability instrument (OS1), and various standard chemical analyses were used in this investigation to complement the DSC methods. This work is a systematic study of vegetable oils' melting and crystallization profiles by using DSC. The investigation began with the successful comparison of the DSC thermal curves of 17 different vegetable oils. Thorough investigations in this work were also directed towards obtaining basic information about the relationship between thermal profiles and chemical compositions of 17 different vegetable oils. Thereafter, the effects ofDSC scanning rate variation were studied. Scanning rates were found to affect melting/crystallization profile, melting (and/or crystallization) offset (and/or onset) and peak. temperatures, and peak. enthalpies of all vegetable oils. In this study, DSC was utilized to monitor the oxidation of heated oils during deep-fat frying and microwave heating. A statistical comparative study was carried out on the DSC and standard chemical methods. The results revealed that there is good correlation (P < 0.01) between the DSC method and other standard chemical methods. In another study, a new calorimetric technique was developed to determine three important quality indices in deep-fat frying industry namely, total polar compounds (TPC), free fatty acid (FFA) content and iodine value (IV) of heated oils using the DSC cooling profiles. The studies have shown that all DSC methods developed were comparable to the standard American Oil Chemists' Society (AOCS) methods. A simple and efficient DSC technique to determine the oxidative stability of vegetable oils was described. The isothermal DSC technique for direct determination of the oxidative stability of vegetable oils has been built and a comparative study to OSI was demonstrated. The results indicated that there is good correlation (P < 0.01) between the DSC oxidative induction time (To) and OSI values. Isothermal calorimetry was then employed as a general analytical method where the Arrhenius kinetic data for the lipid oxidation of vegetable oils were obtained by measurement of the DSC To at various temperatures. The present study also developed a simple method for measuring the antioxidant activity in RBDPOo using isothermal DSC technique. Generally, this project concluded that DSC appears to be a useful method in determining various physical and chemical parameters of vegetable oils, and it may have the potential to replace the laborious, time- and chemical-consuming standard methods. The various methods developed here can be applied in the oils and fats industry

Discrimination of orange beverage emulsions with different formulations using multivariate analysis.

BACKGROUND: The constituents in a food emulsion interact with each other, either physically or chemically, determining the overall physico-chemical and organoleptic properties of the final product. Thus, the main objective of present study was to investigate the effect of emulsion components on beverage emulsion properties. RESULTS:In most cases, the second-order polynomial regression models with no significant (P > 0.05) lack of fit and high adjusted coefficient of determination (adjusted R(2), 0.851-0.996) were significantly fitted to explain the beverage emulsion properties as function of main emulsion components. The main effect of gum arabic was found to be significant (P < 0.05) in all response regression models. CONCLUSION:Orange beverage emulsion containing 222.0 g kg(-1) gum arabic, 2.4 g kg(-1) xanthan gum and 152.7 g kg(-1) orange oil was predicted to provide the desirable emulsion properties. The present study suggests that the concentration of gum arabic should be considered as a primary critical factor for the formulation of orange beverage emulsion. This study also indicated that the interaction effect between xanthan gum and orange oil showed the most significant (P < 0.05) effect among all interaction effects influencing all the physicochemical properties except for density

Physico-chemical stability of astaxanthin nanodispersions prepared with polysaccharides as stabilizing agents

The emulsification and stabilization ability of four selected polysaccharides, namely, gum Arabic, xanthan gum, pectin and methyl cellulose, in the preparation of water-dispersible astaxanthin nanoparticles using the emulsification-evaporation technique was investigated in this study. The chemical and molecular structure of polysaccharides had significant effects (p < 0.05) on the physicochemical properties of the prepared astaxanthin nanodispersions. Among all prepared nanodispersions, sample produced and stabilized using gum Arabic showed the smallest average particle size (295 nm) and highest physical stability. The observed considerable degradation of astaxanthin in the resulting nanodispersions during processing (24–70% w/w) and storage at 10 °C for 30 d (86–96% w/w) illustrated the limited chemical stability of polysaccharide-stabilized nanodispersions

Developing a three component stabilizer system for producing astaxanthin nanodispersions.

Astaxanthin nanodispersions were prepared using Polysorbate 20 (PS20), sodium caseinate (SC) and gum Arabic (GA), solely or in combinations, as stabilizer system, through a solvent-diffusion process. The interactions among these three surface active compounds, in the formation, physicochemical and stability characterization of produced nanodispersions were studied by applying a simplex centroid mixture design. Quadratic or special cubic regression models were fitted for variations of all studied responses as function of significant (p 0.70). Multiple-response optimization predicted that by using 29% (w/w) PS20, 6% (w/w) GA and 65% (w/w) SC as a three component stabilizer system, an astaxanthin nanodispersion could be produced with the most desirable physicochemical characteristics and highest physicochemical stability. At this optimum stabilizer components proportions, the corresponding predicted response values for mean particle size, polydispersity index (PDI) and total astaxanthin loss were predicted to be 114.6 nm, 0.261 and 680 mg/L, respectively. The optimum astaxanthin nanodispersions also showed 2.06% and 1.05% particle size growth at 25 °C and 5 °C, 4.56% and 1.29% PDI growth at 25 °C and 5 °C, and 20% (w/w) astaxanthin loss at 25 °C after 8 weeks of storage. The absence of significant (p > 0.05) differences between the experimental and predicted values of the response variables confirmed the adequacy of the fitted models

Effects of storage temperature, atmosphere and light on chemical stability of astaxanthin nanodispersions.

Astaxanthin, as a functional lipid, can be incorporated easily into different water-based food formulations in the form of a nanodispersion. In this study, astaxanthin nanodispersions were produced using different stabilizer systems, namely, polysorbate 20 (PS20), sodium caseinate (SC), gum arabic (GA) and an optimum combination of these three stabilizers (OPT). Since astaxanthin is sensitive to oxidative damage, its degradations kinetics in the prepared nanodispersion systems were investigated as a function of storage temperature, atmosphere and light. The results showed that astaxanthin degradation followed a first-order kinetic and, in most cases, astaxanthin was more stable in optimum-formulated three-component-stabilized nanodispersions as compared to nanodispersion systems stabilized by individual stabilizers. In addition, high storage temperature and intense illumination significantly (P < 0.05) increased the degradation of astaxanthin, while oxygen-free conditions significantly (P < 0.05) reduced the astaxanthin degradation rate

Chemical stability of astaxanthin nanodispersions in orange juice and skimmed milk as model food systems.

Solubilising astaxanthin in nanodispersion systems is a promising approach to incorporate astaxanthin into water-based food formulations. In this research, the chemical stabilities of astaxanthin nanodispersions diluted in orange juice and skimmed milk as model food systems and in deionised water as a control were evaluated. The nanodispersions displayed significantly (p < 0.05) better stability in food systems compared to the control. The effects of stabilisers and dilution factor were also studied. In skimmed milk and deionised water, the type of stabiliser had a significant effect (p < 0.05) on astaxanthin degradation during storage. In vitro cellular uptake of astaxanthin from diluted astaxanthin nanodispersions in selected food systems was also evaluated. The cellular uptake of astaxanthin nanodispersions in skimmed milk was significantly higher (p < 0.05) than that of astaxanthin nanodispersions in orange juice and deionised water. High in vitro cellular uptake of astaxanthin from the prepared astaxanthin nanodispersions can be achieved via incorporation into protein-based foods such as milk

Effects of selected polysorbate and sucrose ester emulsifiers on the physicochemical properties of astaxanthin nanodispersions.

The effects of selected nonionic emulsifiers on the physicochemical characteristics of astaxanthin nanodispersions produced by an emulsification/evaporation technique were studied. The emulsifiers used were polysorbates (Polysorbate 20, Polysorbate 40, Polysorbate 60 and Polysorbate 80) and sucrose esters of fatty acids (sucrose laurate, palmitate, stearate and oleate). The mean particle diameters of the nanodispersions ranged from 70 nm to 150 nm, depending on the emulsifier used. In the prepared nanodispersions, the astaxanthin particle diameter decreased with increasing emulsifier hydrophilicity and decreasing carbon number of the fatty acid in the emulsifier structure. Astaxanthin nanodispersions with the smallest particle diameters were produced with Polysorbate 20 and sucrose laurate among the polysorbates and the sucrose esters, respectively. We also found that the Polysorbate 80- and sucrose oleate-stabilized nanodispersions had the highest astaxanthin losses (i.e., the lowest astaxanthin contents in the final products) among the nanodispersions. This work demonstrated the importance of emulsifier type in determining the physicochemical characteristics of astaxanthin nano-dispersions

Response surface methodology and multivariate analysis of equilibrium headspace concentration of orange beverage emulsion as function of emulsion composition and structure

The influence of emulsion composition (i.e. Arabic gum, xanthan gum and, orange oil) and structural emulsion properties (i.e. average droplet size and apparent viscosity) on equilibrium headspace concentration of beverage emulsions was investigated. Increase in average droplet size led to increase the equilibrium headspace concentration of more hydrophilic volatile compounds (i.e. lower log P) such as ethyl acetate and octanal, but decrease in more hydrophobic volatile compounds such as 3-carene, myrcene and limonene. In most cases, apparent viscosity had significant positive effect on equilibrium headspace concentration. Principle component analysis (PCA) score discriminated the beverage emulsions containing the same orange oil content but different contents of emulsifiers in different classes, thus indicating the significant (p < 0.05) effect of emulsifier fraction on equilibrium headspace concentration. Beverage emulsion containing 22.2% (w/w) Arabic gum, 0.52% (w/w) xanthan gum and 14.21% (w/w) orange oil was estimated to provide the highest equilibrium headspace concentration

Physicochemical properties of beverage emulsion as function of glycerol and vegetable oil contents.

The main objective of present study was to investigate the effect of type and concentration of two emulsion components, namely glycerol (0.5, 1 and 1.5% w/w) and vegetable oil (2, 3 and 4% w/w), on average droplet size, polydispersity index, electrophoretic mobility, pH, cloudiness, density and stability of beverage emulsion. The results indicated that the physicochemical properties of beverage emulsions were significantly (p < 0.05) influenced by the addition of different concentration levels of supplementary emulsion components. The magnitude of all physicochemical properties significantly (p < 0.05) increased with increasing the concentration of glycerol from 0.5 to 1.5% (w/w). On the other hand, the increase in vegetable oil content resulted in significant (p < 0.05) increase in polydispersity index, cloudiness and stability of beverage emulsion; while a significant (p < 0.05) reduction in average droplet size and density was observed with increasing the proportion of vegetable oil in basic emulsion formulation. The addition of glycerol resulted in significant (p < 0.05) increase in average droplet size as compared to the control sample and vegetable oil-contained beverage emulsions. The present observation could be due to the positive effect of glycerol on the viscosity of beverage emulsion, thereby reducing the efficiency of homogenization and emulsification processes. The addition of both supplementary components led to undesirable effect on the homogeneity (i.e. higher PDI) of beverage emulsions. Electrophoretic mobility significantly (p < 0.05) increased as the concentration of glycerol or vegetable oil was increased. The significant (p < 0.05) effect of glycerol or vegetable oil on electrophoretic mobility was found to be pH dependent. The results showed that pH value was significantly increased with increasing glycerol or vegetable oil content, thus increasing the degree of electrophoretic mobility

Palm-based functional lipid nanodispersions : preparation, characterization and stability evaluation.

The objective of the present study was to investigate the effect of high-pressure homogenization conditions, namely pressure (20–80 MPa) and number of cycles (1–3 cycles), on the properties of palm-based functional lipids. Nanodispersions prepared with palm-based functional lipid and Tween 20 were characterized by monitoring their physicochemical and morphological properties. The results showed that high-pressure homogenizer was an efficient emulsification technique producing small emulsion droplets with narrow size distribution. In general, the results showed that different homogenization conditions had significant (p < 0.05) effect on the size distribution of prepared nanodispersions. Average particles ranging from 95 to 130 nm and 140 to 210 nm were obtained for the nanoemulsions containing palm-based tocopherol–tocotrienol and carotenoid, respectively. However, this study indicated that increasing the energy input beyond moderate pressures (20–80 MPa) and cycles (1–3) led to “over-processing” of droplets. The nanodispersions proved to be physically stable and showed good stability during 12 weeks of storage