*4.1. Applications of Cellulose*

Cellulose is commonly applied in food packaging (e.g., fruits, vegetables, and oils) as edible films, coatings, and emulsions to protect the sensory qualities of foods and extend their shelf lives (Table 4). Rhimi et al. [98] added cypress seed extract to an HPMC matrix and prepared edible composite films using the casting method, and then applied them in olive oil packaging (as shown in Figure 3). The results indicated that compared with pure HPMC films, the tensile strength of the composite films was significantly improved (up to 15.13%) and the WVP was reduced (24.66% at most), which slowed down the oxidation of olive oil during 23 days storage. The lowest WVP, greatest opacity, and highest antioxidant capacity of the composite films were obtained with the highest extract concentration. Therefore, the peroxide value of olive oil sealed with composite films (containing 2% *w*/*v* extract) after accelerated storage for 11 days was 10 times lower than when sealed with pure HPMC films.

It is also noteworthy that cellulose is usually added to other edible materials as a reinforcing or toughening agent to improve the properties of composites. In the blends with collagen and whey protein, methylcellulose was responsible for the increase in tensile strength, water vapor barrier, and thermal properties. While, the prepared methylcellulosebased edible materials (Figure 4) could maintain their integrity for months, be completely biodegraded in 10 days in soil (Figure 5), and when immersed in hot or cold water showed total solubilization in around 30 s upon manual shaking [91]. The edible packaging has immense potential applications in soluble sachets for powdered foods, as well as oil containers and capsules for instant foods (Figure 6). Furthermore, the addition of cellulose nanocrystals to soybean protein could improve the tensile strength and barrier properties (the static water contact angle increased, and the moisture content, WVP, and reduced oxygen permeability) of the edible composite film, and enable the film to obtain ultraviolet light-shielding performance on the premise of appropriate transparency [184]. In addition, the creaming stability and ability to form an elastic gel-like network of beeswax-in-water (O/W) Pickering emulsions could be improved by blending with cellulose nanofibrils/carboxymethyl chitosan. Meanwhile, the complex edible films cast by modified emulsions had good tensile strength (5.0 MPa at a strain of 2.2%) and low WVP (<2 × <sup>10</sup>−<sup>7</sup> <sup>g</sup>·h−1·m−1·Pa−1), and could inhibit the growth of *S. aureus* and *E. coli*, a promising application for antiseptic and fresh-keeping packaging for berry fruits [185].

**Figure 4.** Scanning electron microscopy images (×2000) and physical photos of different edible films. (**A**) Collagen film; (**B**) Whey protein film; (**C**) Methylcellulose film; (**D**) Collagen/whey protein blend film; (**E**) Collagen/methylcellulose blend film; (**F**) Whey protein/methylcellulose blend film. (Adapted with permission from Filipini [91]; published by John Wiley and Sons, 2020).

**Figure 5.** Biodegradability in the soil of different edible films. (**A**) Collagen film; (**B**) Whey protein film; (**C**) Methylcellulose film; (**D**) Collagen/whey protein blend film; (**E**) Collagen/methylcellulose blend film; (**F**) Whey protein/methylcellulose blend film. (Adapted with permission from Filipini [91]; published by John Wiley and Sons, 2020).

**Figure 6.** Prototype photos of different edible packaging. From (**A**–**G**) are methylcellulose sachets containing soybean oil, salt, whey protein, powdered coffee, powdered juice, rice, and cookies, respectively; (**H**) Whey protein/methylcellulose edible sachet containing oil; (**I**) Whey protein edible film for the coffee capsule. (Reproduced with permission from Filipini [91]; published by John Wiley and Sons, 2020).
