Bioactive constituents

Active extracts

Thermoplastic starch films

Valorisation of residues

Green extraction methods

Circular economy

The valorisation of agricultural waste is of growing interest in the context of the circular economy. One potential use of the fractions obtained from lignocellulosic residues is that of the development of packaging materials with circulating resources (Mochane et al., 2021), thus helping to limit the disposal of waste in landfills and to eliminate greenhouse gas emissions while valorising the vegetal residues (Mak et al., 2020). One potential application of these residues is based on both their cellulosic content and bioactive phytochemicals, which could be used for producing packaging materials with improved functions, such as reinforced mechanical properties and antioxidant or antimicrobial activity. Of the agricultural waste, rice straw (RS) is the third-largest residue from agriculture after sugarcane bagasse and maize straw, presenting problematic waste management and non-economic value. Due to its high cellulose content (37 %, Freitas et al. (2022a)), RS is a good source of cellulosic components (microfibres, nanocrystals), which could be used as reinforcing materials for enhancing the filḿs mechanical and barrier properties (Freitas et al., 2021, Freitas et al., 2022a). The lignocellulosic fraction consists of a complex matrix made up of crystalline cellulose microfibrils as the primary fibre component linked to a cementing matrix composed of hemicellulose and lignin (Chen et al., 2011), which have to be removed to obtain the purified cellulose. Several authors (Perumal et al., 2018, Freitas et al., 2022a) incorpo…

2.1. Chemicals

Corn starch (27 % amylose) was supplied by Roquette (Roquette Laisa, Spain). Glycerol, acetic acid, sodium carbonate (Na2CO3) (99.5 % purity), di-phosphorus pentoxide (P2O5), and magnesium nitrate (Mg(NO3)2) were supplied by PanReac Quimica S.L.U. (Castellar del Vallés, Spain). Gallic acid, Folin‐Ciocalteau reagent (2 N), methanol (>99.9 purity), 2,2‐Diphenyl‐1‐picrylhydrazyl (DPPH), sodium chlorite, 2-thiobarbituric acid (>98 % purity), and 1,1,3,3-tetramethoxypropane were purchased from Sigma‐Aldrich (St. Louis, MO, USA). Iodine (99.5 % purity) was obtained by Acros Organics® (Geel, Belgium).

2.2. Obtaining rice straw fractions

Aqueous extract and cellulose fibres were obtained from rice straw (RS), as described in previous studies (Freitas et al., 2020, Freitas et al., 2022a). RS (Oryza sativa L.), J. Sendra var., was obtained from L’Albufera rice fields (Valencia, Spain) and was vacuum dried (0.8 mmbar, 50 ± 2 °C, 16 h), ground using a grinding machine (IKA, model M20, IKA Werke GmbH & Co. KG, Staufen, Germany), and sieved (particles of under 0.5 mm) before the extracti…