The processes of oil production play an important role in defining the final physical and chemical properties of vegetable oils, which have an influence on the formation and characteristics of emulsions. The objective of this work was to investigate the correlations between oils’ physical and chemical properties with the stability of conventional emulsions (d > 200 nm) and nanoemulsions (d < 200 nm). Five vegetable oils obtained from different production processes and with high proportion of unsaturated fatty acids were studied. Extra virgin olive oil (EVOO), cold-pressed rapeseed oil (CPRO), refined olive oil (OO), refined rapeseed oil (RO) and refined sunflower oil (SO) were used in this study. The results showed that the physicochemical stability of emulsion was affected by fatty acid composition, the presence of antioxidants, free fatty acids and droplet size. There was a significant positive correlation (p < 0.05) between the fraction of unsaturated fatty acids and emulsion oxidative stability, where SO, OO and EVOO showed a significantly higher lipid oxidative stability compared to RO and CPRO emulsions. Nanoemulsions with a smaller droplet size showed better physical stability than conventional emulsions. However, there was not a significant correlation between the oxidative stability of emulsions, droplet size and antioxidant capacity of oils.

The combination of two emulsifiers, lecithin and hydroxypropyl methylcellulose (HPMC), into emulsions is an interesting strategy to design fat replacers in food matrices. The objective of this study was to investigate the effect of HPMC type and concentration on the formation, stability, and microstructure of conventional emulsions and nanoemulsions. Two different types of HPMC with low and high content of methyl and hydroxypropyl groups (HPMC-L and HPMC-H) were evaluated. The results showed that the molecular structure and concentration of HPMC play a major role in the viscoelastic behaviour, the gelation temperature, and the strength of gel formed. The firmness and work of shear of HPMC solutions increased significantly (p < 0.05) with increasing concentration. HPMC-L illustrated a more stable gel structure than the HPMC-H solution. Nanoemulsions showed lower moduli values, firmness, and work of shear than conventional emulsions due to the influence of high-pressure homogenization. A combination of lecithin and HPMC improved the physical and lipid oxidative stability of the emulsions, presenting a lower creaming index and thiobarbituric acid reactive substances (TBARS). In conclusion, HPMC-L at 2% w/w could be a suitable type and concentration combined with lecithin to formulate a saturated fat replacer that could mimic butter technological performance during food manufacturing operations.

Extra virgin olive oil-in-water nanoemulsions stabilised with synthetic or clean label surfactants (Tween 20 or soy lecithin) was prepared using high-pressure homogenisation (HPH). The effect of HPH pressure and the number of cycles were assessed through response surface methodology to optimise homogenisation processing parameter. Mean droplet diameter (MDD), polydispersity index (PDI), thermal stability and oxidation stability of the resulting emulsions were evaluated. The results showed that the formation and stability of nanoemulsions can be affected by the homogenisation processing parameters (pressure and cycles) and the properties of surfactants (interfacial tension, viscoelasticity and molecule structure). Although MDD and PDI of Tween 20 stabilised nanoemulsions were influenced by homogenisation pressure and cycles, there was not a significant effect on lecithin-stabilised nanoemulsions. A homogenisation pressure of at least 400 bars produced Tween 20 stabilised nanoemulsion (MDD < 200 nm), whereas lecithin-stabilised nanoemulsion were obtained after high-speed homogenisation without using HPH. HPH at 400 bars for 1 cycle produced nanoemulsions with greater physical stability when using either Tween 20 or lecithin. Tween 20 stabilised nanoemulsion showed significantly higher (p < 0.05) thermal stability and lipid oxidative stability than lecithin-stabilised nanoemulsion. Following an optimisation study using regression modelling, the optimal homogenisation parameter for MDD of Tween 20 stabilised emulsion was found at pressure of 764 bars with 1 cycle, while lecithin-stabilised emulsion was found at pressure of 3 bars with 2 cycles. Overall, this study has important implications for optimising nanoemulsion production for potential application in the food industry.

Biscuits contain high proportion of saturated fats, which could lead to an adverse health effect. The objective of this study was to study the functionality of complex nanoemulsion (CNE), which stabilised with hydroxypropyl methylcellulose and lecithin when used as a saturated fat replacer in short dough biscuits. Four biscuits formulations were studied including a control (butter), three formulations where 33% of the butter was replaced with extra virgin olive oil (EVOO), with CNE, and with the individual ingredient of the nanoemulsion added separately (INE). The texture properties, microstructure, and quantitative descriptive analysis with a trained sensory panel of the biscuits were evaluated. The results showed that CNE and INE gave place to doughs and biscuits with significantly higher (p < 0.05) hardness and fracture strength values than the control. The doughs made of CNE and INE showed significantly less oil migration during the storage than EVOO formulations, which confirmed by the confocal images. The trained panel did not find significant differences in crumb density and hardness on the first bite among CNE, INE and the control. In conclusion, nanoemulsion stabilised with HPMC and lecithin can work as a saturated fat replacer in short dough biscuits, providing satisfactory physical characteristics and sensory attributes.

Biscuits contain high proportions of saturated fats, which could lead to an adverse health effect. The objective of this study was to study the functionality of a complex nanoemulsion (CNE), stabilised with hydroxypropyl methylcellulose and lecithin, when used as a saturated fat replacer in short dough biscuits. Four biscuit formulations were studied including a control (butter) and three formulations where 33% of the butter was replaced with either extra virgin olive oil (EVOO), with CNE, or with the individual ingredients of the nanoemulsion added separately (INE). The biscuits were evaluated by texture analysis, microstructural characterisation, and quantitative descriptive analysis by a trained sensory panel. The results showed that incorporation of CNE and INE yielded doughs and biscuits with significantly higher (p < 0.05) hardness and fracture strength values than the control. The doughs made of CNE and INE showed significantly less oil migration during the storage than EVOO formulations, which was confirmed by the confocal images. The trained panel did not find significant differences in crumb density and hardness on the first bite among CNE, INE and the control. In conclusion, nanoemulsions stabilised with hydroxypropyl methylcellulose (HPMC) and lecithin can work as saturated fat replacers in short dough biscuits, providing satisfactory physical characteristics and sensory attributes.