# D-Limonene: Promising and Sustainable Natural Bioactive Compound
## 7 Application: Nanotechnology and D-Limonene
### Applications  
#### 7.2.1 Food  
As a natural compound with excellent antimicrobial activity, D-limonene has the potential to be used in food preservation but, if it is added directly, it will affect the quality of the food itself; nanoencapsulation is one of the feasible ways to overcome this problem. Nanoencapsulation not only improves the physicochemical properties of the active substance and prevents them from interacting with the food matrix but also increases the passive cellular absorption mechanism, reducing mass transfer resistance and improving antimicrobial activity, possibly due to its subcellular size. [199].  
Nanocapsulated D-limonene can improve the shelf life of food. For example, the nanoemulsion coating prepared using deionized water, propylene glycol, D-limonene, and sodium alginate had good particle size uniformity (3-5 nm) and resulted in better inhibition of _L. monocytogenes, S. enterica,_ and _E. coli_ than unencapsulated D-limonene, with 50%, 90%, and 87.5% reductions in the MBCs, respectively, and it reduced the rate of water and weight loss during storage of bananas, inhibited pectinase activity, and extended shelf life [200] and [PERSON] et al. [201] found the materials made from D-limonene encapsulated in liposomes exhibited good inhibitory activity against both bacteria and fungi and it significantly extended the shelf life of blueberries.  
In addition, the biobased composites made of D-limonene and \(\beta\)-cyclodextrintrin have excellent heat resistance, which could prevent the loss of D-limonene during high-temperature processing and have potential applications in the preparation of reactive food packaging films [202]. Edible biopolymer (pullulan/carrageenan) functional composite films prepared by [PERSON] et al. [203], with the addition of copper sulfide nanoparticles and D-limonene, exhibited enhanced tensile strength and UV-blocking function, as well as a degree of antibacterial activity. The new fragrant starch-based films prepared with D-limonene exhibited significantly lower hygroscopicity and water solubility, as well as significantly higher tensile strength and, because of the addition of D-limonene, they exhibited effective antimicrobial activity and a pleasant aromatic odor, thus favoring their use for the preservation of some foods with special odors [204]; [PERSON] et al. [205] prepared a composite film made of polyvinyl alcohol/chitosan combined with D-limonene that had good biodegradability and light transmission and the addition of D-limonene (5% \(w/w\)) enhanced the barrier capacity and mechanical properties of polyvinyl alcohol/chitosan films and improved their antibacterial activity against _E. coli_ and _S. aureus_, which prolonged the shelf life of mangoes at room temperature. In addition, fish-gelatin-chitosan-edible films supplemented with D-limonene exhibited better antimicrobial activity and D-limonene addition effectively improved their ductility, as well as their water vapor and light barrier properties [206].  
Although the above-mentioned D-limonene-loaded nanocarriers overcome the defects in the physicochemical properties of D-limonene, there is still a lack of research on the possible modes and mechanisms of their antimicrobial action.