Polymers 2023 , 15 , 1393
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the polymer matrices improves the disposal of composite material [20–22]. Varghese et al. [23] investigated the use of Ceiba pentandra natural fibres in poly(3-hydroxybutyrate- co-3-hydroxyvalerate)-based packaging applications. They found that the incorporation of natural fibres accelerated the degradation of packaging materials, which showed good antibacterial capacity against Staphylococcus aureus and effectively preserved the freshness of strawberries for a longer period. Natural fibres are ecologically friendly but negative packaging aspects include their dominant hydrophilicity and low mechanical properties under humid conditions. Therefore, uses of natural fibres in several packaging applications are limited. Recently, natural fibres have been utilised when the recovery of conventional plastics is not economically feasible, controllable or viable and one-time-use packaging materials are preferrable. Natural fibre-reinforced composites can be reused, unlike card- board boxes. Saraiva et al. [24] developed natural fibre-reinforced composite material from sponge gourd residue and compared its packaging efficacy with that of cardboard boxes. The results showed that the developed natural packaging material was preferable after four cycles of use. This review aimed to investigate advancements in the research, development and utilisation of natural fibre-based composites for food packaging applications. Sources, compositions and recent production techniques of several natural fibres in food packaging were discussed. Physical and chemical modifications of natural fibres that improve their suitability for food packaging were also explored. 2. Natural Fibres in Packaging Natural fibres are abundantly available as biodegradable and renewable natural materials [25] and they have recently received huge attention from the global research community [26,27]. Natural fibres can be divided into three categories by origin: animal- based, mineral based and plant-based [28]. Plant-based natural fibres were the main focus of this review because of their abundant availability at low cost. Plant-based natural fibres are lignocellulosic in nature with their basic constituents including lignin, hemicellulose and cellulose. Animal-based fibres mostly consist of proteins, e.g., wool and silk. Mineral- based fibres are formed as a result of geological processes, such as asbestos and basalt. In plant-based natural fibres, both primary fibres obtained directly from plants and secondary fibres obtained as byproducts after utilisation of primary fibres are used. 2.1. Source and Compositions Natural primary plant fibres include hemp, kenaf, sisal and cotton, while secondary fibres include bagasse, coir, pineapple, agave and oil palm [29–31]. Natural fibres have long been exploited in the preparation and manufacture of ropes and textiles, for example, flax, hemp, cotton lint or sisal. Some fibres have secondary applications in food packaging. Figure 2 shows some of the commonly available natural fibres and their sources, while Table 1 shows the origin and properties of natural fibres. Some of the major varieties of natural fibres are discussed in more detail below.
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