ABSTRACT
The use of lms obtained from hydrophobic materials, mainly waxes such as carnauba wax or candelilla wax, is well known since many fruits and vegetables, such as citrics, have been traditionally coated with these kinds of compounds. These are able to reduce the transpiration/respiration rate of fruits and limit the moisture loss while at the same time increasing gloss, thus improving their appearance. Nevertheless, lipid-based lms and coatings exhibit a poor mechanical performance, mainly due to their fragility and low transparency. One method of taking advantage of the benecial properties of lipids while reducing their drawbacks is the formulation of lipid-polymer (protein or polysaccharide) blends to obtain composite matrices, where lipids are embedded in the polymer network. In this way, composite lms may exhibit improved properties in comparison with pure lipid-or pure biopolymer-based lms. In the last few years, the properties of these kinds of lms have been studied by many authors as a function of the lipid characteristics, polymer afnity, component dispersion method, and lm-drying conditions. The obtained results show great differences in the lms’ behavior, depending on the blend considered. The physical state of the lipids, their particle size in the lm-forming dispersion and lm, and the specic lipid-polymer interactions play an important role in the nal properties and functionality of the lm. Indeed, some properties of the polymeric matrix may be improved by lipid incorporation, whereas others can be negatively affected. For instance, biopolymer lms containing lipids show lower water vapor permeability (WVP), as compared with the corresponding lipid-free lm, although oxygen permeability can be enhanced and the lm transparency may be reduced. Likewise, the mechanical properties of the biopolymer matrices containing lipids are positively or negatively affected, depending on several factors, such as the component compatibility, lipid-polymer ratio, and the nal nano-and microstructure of the blend. In this chapter, the effect of lipids on the properties of biopolymer lms has been discussed as a function of the nature of the lipid, the lipid-polymer ratio, and the polymer’s characteristics, through the data reported from different studies. The most recent achievements and trends in the formulation of lipids-biopolymers are also discussed.
