Development of Saturated Fat Replacers: Conventional and Nano-Emulsions Stabilised by Lecithin and Hydroxylpropyl Methylcellulose

Abstract

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.

Saturated fat replacement in short dough biscuits with HPMC and lecithin stabilised nanoemulsions

“…The replacement of butter with the CNE led to dough pieces (D-CNE) with significantly higher ( p < 0.05) hardness values than the D-control. Although in a previous study, the authors reported similar firmness values for CNE and butter at similar concentrations 39 . The reduction of the fat content in the system may have hindered some of the main functionalities of fat in a dough system, principally lubrication and aeration 5 .…”

“…Moreover, the rheological properties of the nanoemulsions stabilised by HPMC and lecithin could also explain the spreadability of the dough during baking. In a previous study the rheological behaviour during micro-baking was studied 39 ; at low temperatures (20–40 °C) conventional emulsions and nanoemulsions stabilised by HPMC and lecithin showed a decrease in moduli values, which was related to a weakening effect in the intermolecular hydrogen bonds caused by the increased temperature. Then as temperature increased (40–65 °C), G’ and G” moduli increased, marking the starting point of the gelation temperature, during which the formation of strong hydrophobic interactions between HPMC molecules for the formation of a three-dimensional network took place 39 .…”

“…To then prepare nanoemulsions according to the method described by Kampa et al 39 , HPMC powder (2% w/w) was added to the conventional emulsion, and the mixture was stirred using a magnetic stirrer (ChemLab, Model SS3H) at 200 rpm for 3 h at ambient temperature and left 24 h at 4 °C to allow complete hydration of HPMC. The samples were then processed through a high-pressure homogeniser (HPH) (8.30H, Rannie, APV, Denmark) at 4×10 7 Pa for 1 cycle.…”

“…When the polymer is primarily in the solution phase it has been shown to develop a three-dimensional network that compartmentalises the continuous aqueous phase and immobilises the oil globules, resulting in a dense matrix of stable fat globules 23 . In a previous study, the authors have shown that the combination of lecithin and HMPC had a positive effect on the rheological properties of nanoemulsions, as these showed similar firmness and spreadability values to butter, suggesting that they will respond with a similar behaviour when used in mixing and dough sheeting operations 39 . In addition, these nanoemulsions have shown better physical and lipid oxidative stability of the emulsions during storage, due to (i) the formation of a thicker protective layer of lecithin and HPMC adsorbed in the interface of the oil droplets, and (ii) the formation of a stronger network in the continuous phase 39 , 40 .…”

“…In a previous study, the authors have shown that the combination of lecithin and HMPC had a positive effect on the rheological properties of nanoemulsions, as these showed similar firmness and spreadability values to butter, suggesting that they will respond with a similar behaviour when used in mixing and dough sheeting operations 39 . In addition, these nanoemulsions have shown better physical and lipid oxidative stability of the emulsions during storage, due to (i) the formation of a thicker protective layer of lecithin and HPMC adsorbed in the interface of the oil droplets, and (ii) the formation of a stronger network in the continuous phase 39 , 40 . This structural functionality could help to improve the stability of the fat phase in biscuits formulated with saturated fat replacements made of oils high in PUFA and MUFA.…”