Table 1.

Halochromic composite films based on red cabbage anthocyanin: physical and mechanical changes.

Biopolymer/ Polymer	Application	pH Values/Color Change	Main Results after RCAs Incorporation			References
			Physical Properties	Mechanical Properties
				TS	EAB
Bacterial cellulose membrane	Intelligent packaging film for milk	pH = 1–14, color variation from red to purple, gray, and then to yellow	Significant increase in water solubility and swelling index	↓	↑	[19]
Sago starch	Intelligent packaging film	pH = 1–13, clearly color changes between pH 4, 9 and 13	Decrease in moisture content	_	_	[67]
Ethylene-vinyl acetate/ZnO/Fe-MMT nanoparticles	Smart packaging film	pH = 2–12, red to yellow	_	_	_	[66]
Green banana starch/gelatin/alginate	Intelligent packaging film for sheep meat	pH = 2–13	Decrease in thickness, swelling Index and WVP	_	_	[56]
ASK Gum/CMC·Na	Intelligent packaging film	pH = 3–10 (pink to green) (pH = 3 (rose–bengal), pH = 4–6 (purple), pH = 7 (bluish black), pH = 8–9 (atropurpureus), and pH = 11 (aquamarine))	Increase in WVP and light transmission, transparency; increase in OP value with increases in RCA content from 5 to 15%	↓	↑	[41]
Corn starch	Intelligent packaging film	pH = 1–10, color variation from pink to purple and blue depending on the pH variations	Increase in thickness and water solubility	↔	↔	[54]
Bovine gelatin	Smart packaging film	pH = 1–14	No effect on thickness and WVP; decease in moisture content; increase in water solubility (alcoholic extract)	Alcoholic extract: (↔); Aqueous extract: (↑)	Alcoholic extract: (↑); Aqueous extract: (↔)	[64]
Bovine gelatin	Smart packaging film	pH = 2–12, purple, blue, and finally green at pH 8–12	No effect on the thickness	_	_	[50]
KGM/O-ChNCs	Smart packaging film	pH = 2–12, the color changed from pink–red to green	No significant effect on thickness; increase in water solubility and WVP; Decease in light transmittance	↓	↓	[52]
Hydroxypropyl methylcellulose	Intelligent packaging film	pH = 2–9	No effect on thickness; changes in the light barrier properties	↓	↑	[51]
CBO-loaded chitosan capsules	Smart packaging film for fish	pH range of 6–8	No effect on the thickness	↓	↑	[53]
Bacterial cellulose nanofibers	Intelligent packaging film	pH = 2–10, color change in the BCA label at pH 2 and 3 (dark red) and pH 4–10 (dark violet), and in the BCDA label from bright red to dark blue	Increase in moisture absorption	↓	↑	[57]
Dual-modified cassava starch	Intelligent packaging film	pH = 2–12	_	_	_	[68]
Chitosan/oxidized–chitin nanocrystals	Smart packaging film for hairtail and shrimp	pH = 3–10, color variations (red–pink–purple–blue–green) in different pHs	No effect on thickness; significant decrease in WVP, OP values, and light transmittance	↓	↑	[39]
Chitosan/PVA	Intelligent packaging film for pork meat	pH = 1–13 (pH = 1 (reddish color), pH ≈ 6 (purple), pH = 7–8 (blue), pH = 9 (sea green), pH ≈ 12 (yellow–green))	_	↑	↑	[65]
Cationic guar gum film/hydroxyethyl cellulose	Smart packaging film for pork meat and soybean milk (SBM)	Pork for 72 h and SBM for 18 h	Decrease in WVP and OP; decrease in light transmittance	(↑) with ≤3% RCA, (↓) with 5% RCA	(↑) with ≤3% RCA, (↓) with 5% RCA	[63]
Chitosan/corn starch	Intelligent packaging film for fish fillet	pH = 2–13 Blue after 16 h, and yellow after 72 h at room temperature	No significant change in WVP	_	_	[45]
PVA	Intelligent electrospun nanofiber mat for packaging date fruit (rutab)	pH = 2–12 At 25 °C: after 72 h (color altered slightly), 72–96 h (violet and purple), after 96 h (purple) At 5 °C: color completely changed to purple after 12–20 days	Increase in moisture adsorption	↓	↑	[58]
PEGDA/LCNF	Intelligent hydrogel	pH = 1–14 pH = 7–14	No significant change in moisture adsorption	_	_	[69]
Cellulose acetate	Intelligent electrospun Nanofiber for health monitor	pH = 1–14	_	_	_	[70]
Zein	Intelligent electrospun fiber	pH = 1–14	_	_	_	[71]
PVA/NaAlg	Intelligent electrospun nanofiber for wound dressing	pH = 4–10	_	_	_	[72]
PVA/sodium carboxymethyl cellulose	Intelligent packaging film for pork meat	Pork for 24 h	Increase in thickness	↓	↑	[55]
Cellulose acetate	Intelligent packaging film	pH = 1–12 (red color at pH 1–2, pink at pH 3, violet at pH 4–6, blue at pH 7–8, green at pH 9–11, and yellow at pH 12)	Increase in thickness and OP; decrease in light transmittance	↓	↑	[47]

CBO: clove bud oil, PVA: polyvinyl alcohol, SBM: soybean milk, KGM: konjac glucomannan, ASKG: Artemisia sphaerocephala Krasch. gum, O-ChNCs: oxidized chitin nanocrystals, CMC·Na: carboxymethyl cellulose sodium, BCA: BC–anthocyanin, BCDA: BC-diluted anthocyanin, PEGDA: poly (ethylene glycol) diacrylate, LCNF: lignocellulose nanofiber, NaAlg: sodium alginate, NA: not affected, WVP: water vapor permeability, and OP: oxygen permeability. The arrows ↑, ↓ and ↔ indicate significant increase and decrease and no significant change, respectively. All figures/tables used in this table are reprinted with permission from their publishers where needed.