Table 4.
An overview of various drying technologies used in seaweed processing, adapted with permission from [93]. 2021 Zhu et al.
| Drying Method | Conditions | Seaweed Species | Final Moisture Content (MC)/Ratio (MR) | Results | Drying Kinetics Model | Reference |
|---|---|---|---|---|---|---|
| Dehumidified air assisted tray drying | T: 40 to 70 °C; V: 5 and 7 m/s; DT: 100 to 3000 min |
Eucheuma cottonii | MC: 15% (w.b.) | Higher air temperature and air velocity resulted in faster water removal. Moreover, temperatures below 70 °C resulted in a reasonable seaweed quality | Page model | [101] |
| Solar drying and shade drying | Solar DT: 5 days; Shade DT: 8 days; |
N/A | MC Solar: 24–61% (d.b.); MC shade: 40–48% (d.b.) | Samples dried unevenly. Henderson and Pabis model was adopted | Henderson and Pabis model | [100] |
| Hot air drying | T: 35 to 75 °C; RH: 30%; V: 2 m/s; DT: 120 to 240 min |
Ascophylum nodosum, Undaria pinnatifida | MR: 0.03 | Temperature affected drying time and color significantly. Conventional air drying can be considered adequate for A. nodosum, but not for U. pinnatifida. | Page model | [102] |
| Osmotic dehydration assisted hot air drying | T: 30 °C; RH: 14%; DT: 2 h |
Porphyra columbina | MC: 7.9% (d.b.) | Osmotic dehydration, as a pretreatment for air-dried seaweeds, did not seem to improve the final product quality | Page model | [103] |
| Vacuum drying | T: 40–80 °C; P: 15 kPa; DT: 180 to 800 min |
Pyropia orbicularis | MR < 0.1 | Vacuum drying at 70 °C had the highest total phenolic, carotenoid and phycoerythrin and phycocyanin content, lightness as well as antioxidant capacity. | Weibull model | [104] |
| Sauna treatment assisted solar drying | T: 35–40 °C; RH: 32–80%; DT: 2 days |
Kappaphyccus alvarezii | MC: 35% (d.b.) | Sauna treated seaweed reduced the drying time by 57.9% | Page model | [105] |
| Spray drying | T: 140–180 °C; FFR: 3–5 rpm; |
Sargassum muticum | MC: 1.83–3.83% (d.b.) | Good-quality, stable seaweed powder with acceptable properties was spray dried at 140 °C and 3 rpm, with 4% of maltodextrin. | N/A | [106] |
| Freeze drying | T: −86 °C; DT: 48 h |
Kappaphycus alvarezii | MC: 11% (d.b.) | Freeze drying did not show any benefit to retaining any seaweed chemical compositions | N/A | [107] |
| Ultrasound assisted fluidized bed drying | US: Fre: 26 kHz; P: 170 W; V: 6.7 m/s; DT: 110 min USP: Fre: 20 kHz; P: 500 W; DT: 80 min |
Ascophylum nodosum | MC: 10% (d.b.) | Airborne ultrasound dried recovered the best total phenolic content as well as colour, however, no benefit in reducing drying time. Ultrasound pretreatment had the lowest drying energy consumption. | Page model | [108] |
| Fluidized bed drying | T: 40–60 °C; V: 0.5–1 m/s |
Echium amoenum | N/A | The optimal drying conditions were air velocity of 0.86 m/s at 60 °C in terms of highest bioactive compound content, and minimum drying time. | N/A | [109] |
| Spray drying | Pretreated with USP T: inlet 175 °C/outlet 80 °C |
Gracilaria secundata combined with amaranth protein | N/A | Spray drying can be used as an alternative to freeze-drying when producing conjugates with observed improvement in water holding capacity. | N/A | [110] |
Note: T: drying temperature; V: air velocity; DT: drying time; FFR: feed flow rate; U.: Ulva rigida; P: power; Fre: frequency; US: airborne ultrasound assisted fluidized bed drying; USP: ultrasound pretreatment; MC: moisture content; MR: moisture ratio; N/A: not applicable.