Table 1.

The Strategy Methods of improving the stability of phycocyanin.

Methods	Process conditions	Results	Mechanism	Characteristics	Disadvantages	References
Addition of biopolymers
ι-Carrageenan (combined with high-pressure processing)	Mixed polysaccharide solution and phycocyanin solution, then subjected the samples to high-pressure processing treatment (450 Mpa or 600 Mpa)	The light stability of phycocyanin-carrageenan at pH 7.0 is improved and prevent the attack of oxidizing radicals after high-pressure processing	ι-Carrageenan with highly negatively charged stretch phycocyanin's tertiary structure and maintain secondary structure, which may benefit the stability of phycocyanin	Less damage to its nutrient composition and improve the glycation reaction	Although high pressure can't influence the structure of small molecules (chromophore), phycocyanin aggregates with changes in secondary structures and forms a more compact protein structure	https://www.sciencedirect.com/science/article/pii/S0268005X20305385 Zhang et al. (2021)
Whey protein (combined high-pressure treatment)	Mixed phycocyanin solution and whey protein solution, then subjected the samples to high-pressure processing treatment (450 Mpa or 600 Mpa)	The light stability of phycocyanin-whey improved at pH 5.0 after high pressure treatment	Phycocyanin-whey protein mixture with high-pressure progress may encapsulate the chromophore inside the apoprotein network and prevented the attack from oxidizing radicals	Less damage to its nutrient composition and improve the glycation reaction	Phycocyanin may form a more compact protein structure with the changes in secondary structures	https://www.sciencedirect.com/science/article/pii/S0268005X20305385 Zhang et al. (2021)
Low concentration of whey (0.05–0.1%)	Whey protein was dissolved in phycocyanin solution in 100 mL tubes to obtain whey	Delay the color degradation of phycocyanin at pH 3.0 by light over 5 days	A low concentration of whey protein may help unfold chain tetrapyrroles of phycocyanin through transformation from α-helix to β-sheet and protected its secondary structure from being destroyed by light			https://www.sciencedirect.com/science/article/pii/S0308814619317406 Zheng et al. (2020)
Preservatives (citric acid, sucrose and calcium chloride)	Added preservatives into the phycocyanin solution	Maintaining the stability of phycocyanin in aqueous phase at 35 ± 5 °C for 45 days	Increased the stability of the phycocyanin structure and disrupted the structure of water and decrease protein solubility (salting out)	Adjusted the sensory characteristics of food and extended shelf life	Preservative may damage the human health	https://www.sciencedirect.com/science/article/pii/S1359511307003455 Mishra et al. (2008)
DSP [dithiobis (succinimidyl propionate)]	To 19 ml of phycocyanin (3.0 mg/ml) in 50 mM phosphate buffer saline (PBS) (pH 7.4) was added DSP (4.1, 8.2 and 16.4 mg) dissolved in 1.0 ml of dimethyl sulfoxide (DMSO)	The absorbance at 614 nm of cross-linked phycocyanin (Curve b) was retained at 70% of the original color development in 4 M urea for 8 h	DSP modified the amino groups of lysine to protect the high order structure of phycocyanin	Convenient to handling	Exist potential risks	https://www.sciencedirect.com/science/article/pii/S0143720803002730 Fukui et al. (2004)
Formaldehyde	Added the formaldehyde into phycocyanin solution and dialyzed overnight	Phycocyanin-formaldehyde which may keep stabilize at 100% over 120 min and improve the stability up to 1.53-folds under the light	Covalent crosslinking between the formaldehyde and phycocyanin may prevent the dissociation of phycocyanin into subunits	Convenience in ease of handling, extreme adaptability and broadest reaction specificity	Not suitable for food industry	https://www.sciencedirect.com/science/article/pii/S1359511319317131 Munawaroh et al. (2020)
Oil	Incorporated of EVO oil or sunflower oil at the concentration of 10 g oil/100 g of dough	After cooking, extra virgin olive-phycocyanin mixture maintained about 90% of the originally cyanobacterial biomass.	Tocopherol contained in EVO and sunflower oils was the main responsible for the protective action against phycocyanin degradation	Suitable for all bakery products	Not suitable for other food processing	https://www.sciencedirect.com/science/article/pii/S0023643820317655 Niccolai et al. (2021)
Micelles
SDS micelles	Prepared the aqueous solutions of phycocyanin and SDS	Stabilized phycocyanin against pH-dependent color variation	Attributed to the SDS micelles entrapment of the molecule in the interior and stabilized by hydrophobic interactions, it has the capability of stabilizing a folded conformation at low pH	Don't need a substantial amount of encapsulation material. It can be used in transparent products	SDS may confer an unacceptable detergent taste in food products	https://www.sciencedirect.com/science/article/pii/S0308814617311548 Falkeborg et al. (2018)
Microencapsulation
Electrospraying technique	The capillary diameter was 0.45 mm and a distance between the capillary and the collector was 18 cm; 11% PVA and 2% PC, a feed rate of 50 μLh−1 and an electric potential of 20 kV;	The polymer showed well thermal resistance up to 216 °C	Phycocyanin was surrounded by a barrier (PVA) to protect against light, oxygen, pH, moisture, heat, shear or other extreme conditions	Smaller droplet size with a narrow distribution; High encapsulation efficiency; Without using high temperature or pressure	Low throughput	https://www.sciencedirect.com/science/article/pii/S0960308519301762 Schmatz et al. (2020)
Extrusion technique	Alginate and chitosan were used as coating materials; Under the high pressure, the matrix dispersion through a single or a plurality of pathways directly into the continuous extraction phase	The microcapsules could resistant to the light (light for 40 days), temperature (50 °C), acidic (SGF pH 1.2) and humid (31% relative humidity) environment	Attributed to the hygroscopicity of chitosan, the compact structure of microencapsulation was formed by the interaction of alginate and chitosan and prevented the entry of water	Simple and convenient; Better-controlled microsphere sizes	Involved high pressure	https://www.sciencedirect.com/science/article/pii/S0960308513000734 Yan et al. (2014)
Entrapped into silica matrixes	Encapsulated phycocyanin into hydrogel and controlled the gelation time to homogeneously dispersing it in silica matrix	The photodamage rate constant of phycocyanin in silica is 25 times slower than the phycocyanin in buffer solution	Phycocyanin encaged by Si–O bands, which could restrict the unfolding of phycobilin and protect the linear conformation			https://link.springer.com/article/10.1007%2Fs11164-009-0061-5 Li et al. (2009)
Coated with STMP/STPP cross-linked starches	Sodium trimetaphosphate/sodium tripolyphosphate cross-linked potato, banana, corn, cassava, and breadfruit starches were as wall materials for C-phycocyanin encapsulation	Prolonged antihyperalgesic effects of phycocyanin in vivo	The C-phycocyanin was encapsulated within amorphous chains of cross-linked starches	High availability; Low cost		https://www.sciencedirect.com/science/article/pii/S0141813020332633 Lemos et al. (2020)