Table 1.

Sources, compositions, structures, and outstanding characteristics of five polysaccharides for edible packaging application.

Polysaccharides		Sources	Molecular Structure Characteristics	Functional Advantages
Cellulose		Major: wood and cotton Minor: certain peels, husks, bagasse, algae, vegetables, tunicates fungi, invertebrates, and bacteria [16,24,25]	Comprise anhydroglucose units connected by β-glycosidic bonds Contains numerous hydroxyl groups [26]	Good chemical stability, gelation, and film-forming properties Good mechanical properties, and barrier capacities to oxygen and lipids Renewable, biodegradable, biocompatibility Soluble dietary fiber and food additive [13,16,27] □ Compared with ordinary cellulose, nanocellulose has a higher elastic modulus, tensile strength, crystallinity, lower coefficient of thermal expansion, large specific surface area, high reactivity, and small size effects [28]
Hemicellulose	Xylan	Major: hardwoods, gramineous plants Minor: certain crops and their processing by-products [29,30,31,32]	Composed of (1→4) bonds connected to the main chain of β-D-pyranose units and different side groups connected by (1→2) and/or (1→3) bonds Contains numerous hydroxyl groups [29,30,32]	Good gelation, and film-forming properties Good mechanical and gas barrier properties (But these properties are slightly worse than those of cellulose) Renewable, biodegradable, biocompatibility Soluble dietary fiber and food additive [16,29,30,32]
	Glucomannan	Softwoods, tubers and seeds of Amorphophallus konjac plants [30,31,33]	Composed of D-glucopyranosyl and D-mannopyranosyl connected by β-(1→4) bonds Contains numerous hydroxyl groups [16,30,31]
Starch	Amylose	Major: corn, rice, wheat, cassava, and potatoes [34,35] Minor: banana, mango, breadfruit [34,35], oca [36], jackfruit and lotus seeds [37], and pineapple stems [38]	Composed of α-D glucose connected by α-(1→4) glycosidic bonds; has no branched structure or only a small amount of branched structures connected by α-(1→6) glycosidic bonds Only hydrophobic hydrogen atoms inside the helix structure, and hydrophilic hydroxyl groups outside it [16,39,40,41]	Good mechanical properties, oxygen barrier property, and processability Renewable, biodegradable, recyclable, biocompatibility Low processing cost Food additive [15,42,43] □ Gelatinize, regenerate, swell, and a certain proportion of starch aqueous solution behaves as non-Newtonian fluid (The above characteristics are not available in polysaccharides such as cellulose, hemicellulose, chitosan and alginate); and semi-permeable to carbon dioxide [41,44,45,46] □ Worse gelation, film-forming properties, and transparency if compared to cellulose, hemicellulose, chitosan, and polysaccharide gums [15,16]
	Amylopectin		The main chain is composed of α-D-(1→4) glycosidic bonds, and the side chain is composed of α-(1→6) glycosidic bonds; the structure is more complex and arranged radially in a concentric form Contains numerous hydroxyl groups [44,47,48]
Chitosan		Major: the shells of crustaceans such as shrimps, crabs, insects Minor: the cell walls of lower plants, bacteria, and fungi [49]	Composed of N-acetyl-D-glucosamine and D-glucosamine (occupies a larger proportion, generally > 55%) connected by β-(1→4) glycosidic bonds Contains numerous amino and hydroxyl groups, and a few acetylamino [16,50,51]	Good gelation, film-forming properties and processing suitability Good mechanical, oxygen and lipids barrier, and adsorptive properties (The tensile strength and swelling power of chitosan films prepared at higher drying temperatures and solute concentrations improved relatively) Renewable, biodegradable, biocompatibility Food additive [51,52,53,54] □ The high specific surface area, large aspect ratio, and small size effect of nano-chitosan can further improve the biological activity, biocompatibility, and adsorption properties of ordinary chitosan [55,56] □ Good antioxidant activity; and excellent antimicrobial activity, with effective inhibition of most gram-negative and -positive bacteria and fungi (These properties differ from those of cellulose, hemicellulose and starch) [57,58]
Polysaccharide gums	Pectin	Major: fruit and vegetable processing residues such as citrus peel, apple peel, sweet potato residue, and beet residue [59] Minor: the peels of passion fruit [60], lime [61], dragon fruit [62], fig [63], grapefruit [64], pomegranate [39], lemon [65], and hawthorn [66]; and sunflower heads without seeds [67], Premna microphylla Turcz leaves, and Creeping fig seeds [68]	An acidic heteropolysaccharide composed of D-galacturonic acid and other neutral sugars; the fine structure of the domain has not yet been fully clarified [15] Contains numerous hydroxyl and carboxyl groups [63,66] Complex metal ions such as Fe2+ or Cu2+; enhance the activity of antioxidant enzymes such as superoxide dismutase and catalase [63,66]	Better gelling and film-forming properties than cellulose and starch Better water-retaining properties and transparency than cellulose and starch Good oxygen and lipids barrier properties (Their products have oil-, grease-, and odor-proofing capabilities and can effectively slow down the oxidation of food lipids) Renewable, biodegradable, biocompatibility Soluble dietary fiber and food additive (e.g., water sacrificial agent) [15,16,60,69,70,71] □ Pectin and its derivatives extracted from the peel of certain fruits (e.g., fig, lemon, apple, and hawthorn) have antioxidant and antimicrobial activities; furthermore, pectin has a weak antibacterial effect, but its degradation products (especially pectin enzymatic hydrolysis products) have an obvious inhibitory effect on common foodborne pathogens such as Staphylococcus aureus, Escherichia coli, and Vibrio parahaemolyticus [63,65,66,72,73] □ Alginate exhibit polyanion behavior in an aqueous solution and have a certain amount adhesion [16,74] □ The commonly used agar for packaging is agarose, and its molecules can interact through hydrogen bonds to form a continuous and firm network structure [71]
	Alginate	Major: cell wall and intercellular mucilage of brown algae such as Laminaria, Kelp, Durvillaea potatorum, and Sargassum Minor: some Pseudomonas, nitrogen-fixing bacteria, and other bacteria that can produce mucous capsules [15,16,74,75,76]	A long-chain linear copolymer connected by β-D-mannuronic acid and α-guluronic acid, according to (1→4) bonds Contains numerous -COO- groups Its products usually include sodium alginate, potassium alginate, calcium alginate, zinc alginate, and magnesium alginate [16,74,76,77,78]
	Carrageenan	Cell walls of marine red algae, such as Eucheuma, Chondrus, Gigartina, Gelidium, and Hypnea [15,79]	A linear galactosan composed of sulfated or non-sulfated galactose and 3,6-dehydrated galactose alternately connected by α-(1→3) and β-(1→4) glycosidic bonds Divided into seven types (e.g., κ, ι, λ, γ, ν, ξ, and μ-type) according to the different binding forms of sulfate esters Contains numerous hydroxyl groups [15,79]
	Agar	Marine red algae, such as ferns, asparagus, laver, Gelidium, and Gracilaria [80]	A galactose polymer composed of agarose and agaropectin Agarose is a non-ionic polysaccharide without sulfate (salt) and comprises 3,6-dehydration-α-L-galactose and β-D-galactose residues alternately connected by (1→3) glycosidic bonds Contains numerous hydroxyl groups [15,69,80]