Table 2.

Parameters of lyophilization and the properties of selected freeze-dried products.

Dried Material	Material Size and Form	Freezing Parameters	Shelf Temperature	Pressure of the Chamber	Drying Time	Properties of Material	Ref.
Abalone	Cylindrical disks (2.5 cm diameter and 0.7 cm height)	−40 °C	−45, −30, −20, −10, −5, 0, 10, and 15 °C	100 Pa	72 h	The increase of a shelf temperature in the range of −45–15 °C caused an increase of the apparent density of dried abalone from 372.9 to 472.1 kg/m3 and a decrease of apparent porosity from 0.733 to 0.664.	[93]
Apple	Cylindrical disks (2.5 cm diameter and 0.7 height)	−40 °C	−45, −30, −20, −10, −5, 0, 10, and 15 °C	100 Pa	72 h	The increase of a shelf temperature in the range of −45–15 °C caused an increase of apparent porosity from 0.876 to 0.910.	[93]
	Semi-circular slices (55 mm in length, 2.2–2.5 mm thick)	−25 °C	−25 °C at 1st step drying, 40 °C at 2nd drying	20 Pa at 1st step drying, 5 Pa at 2nd drying	24 h	The moisture content was negatively correlated with hardness of freeze-dried apples. The application of freeze-drying resulted in a lower springiness compared to that of the air-drying method. Additionally, the color difference ΔE of freeze-dried apples (11.37) was lower than that obtained for air-dried apples (21.11).	[116]
	Puree—layer with thickness of 4 mm	−40 °C	20 °C	63 Pa	26 h	The apple puree freeze-dried at 20 °C absorbed less water than air-dried samples. The application of freeze-drying method enabled the obtainment of powder with a slightly lower hygroscopicity than after microwave-drying.	[130]
Banana	Cylinders with diameter of 20 mm and 8 mm height	−35 °C (48 h), tempered for 1 h in liquid N2	Product temperature from −50 to −8 °C	3–300 Pa	24 h	The values of the bulk density of the banana decreased after freeze-drying from 1900 kg·m−3 to values lower than 400 kg·m−3. The values of bulk density increased (about ~30%) as the temperature of process was increased from −50 to −8 °C. The porosity of freeze-dried banana was the highest at the low temperature of −50 °C (~0.9).	[95]
Carrot	Cylinders with diameter of 20 mm and 8 mm height	−35 °C (48 h), tempered for 1 h in liquid N2	Product temperature from −50 to −5 °C	3–300 Pa	24 h	The values of bulk density of carrot tissue decreased after freeze-drying from 1750 kg·m−3 to values lower than 250 kg·m−3. The bulk density values increased (about ~40%) as the temperature of process was increased from −50 to −8 °C. The porosity of freeze-dried carrot was reduced by about 10% after drying at higher temperatures.	[95]
Coffee solutions	Layer with thickness of 20 mm	1 set: −40 °C at 1 °C/min 2 set: fluctuation of temperature between −40 and −20 °C	−40 °C at the primary drying, 20 °C at the secondary drying	10 Pa	18 h	Samples freeze-dried with temperature oscillations (−20 and −40 °C) had larger pores than material frozen at −40 °C. Temperature fluctuations during freezing promoted large crystal formation and resulted in a higher total porosity by, on average, 18%. The application of freezing cycles led to faster reconstruction rates.	[131]:
Dragon fruit	Pieces with thickness of 1 cm	−40 °C fast freezing (an air blast freezer and a contact plate freezer)	−5 °C at the primary drying, 30, 40, and 50 °C at the secondary drying	40 Pa	50 h at 30 °C, 55 h at 40 °C, 60 h at 50 °C	The apparent densities of freeze-dried dragon fruits were 0.16, 0.19, and 0.08 g × cm−3 at the drying temperatures 30, 40, and 50 °C, respectively. The hardness of dried fruit decreased from 9.26 to 4.33 N and crispness increased from 6.83 to 10.56 with the increase of the heating temperature.	[115]:
Eggplant	Cubes of 9 mm side	−40 °C	1 set: −30, −15, and 0 °C at 1st step drying, 20 °C at 2nd step drying 2 set: −30 and 0 °C at 1st drying, 20 °C at 2nd step drying	1 set: 10 Pa 2 set: 10, 20, and 40 Pa	1 set: 7–15.3 h 2 set: 14–20.9 h	The loss of antioxidant capacity was 49.9 and 68.6% for freeze-dried samples dried at −30 and 0 °C, respectively. The increase of drying temperature from −30 to 0 °C caused the loss of ascorbic acid from 37.9 to 12.2%. Total polyphenol content—TPC—in dried product was retained at higher pressures. The loss of TPC was 32.5% at 40 Pa and 47.7% at 10 Pa.	[132]:
Garlic	Brick shaped samples (20 × 10 × 10 mm)	−40 °C	−5, −15, and −25 °C	108 Pa	72 h	The decrease of shelf temperature from −5 to −25 °C during the freeze-drying of garlic resulted in a decrease of the apparent density from 469 to 431 kg/m3 and an increase of the shrinkage expansion between 0.44 and 0.52, as well as the true density decreased in the range of 1534–1504 kg/m3.	[94]:
Grapefruit puree	1-cm layer	−45 °C	room temperature, 40 °C	9 Pa	1.5−21 h	The increase of temperature promoted an increase in the porosity of freeze-dried puree (from 0.78 to 0.83) and a decrease in the number of pores formed from 415to 312.	[16]:
Gum Arabic solutions	Layer with a height of 0.5 cm	−40 °C (at 1 °C/min)	−20, −30, and −40 °C at primary during, 20 °C at secondary drying	10 Pa	18 h	The degree of puffing was stronger for samples dried at higher (−20 and −30 °C) compared to lower (−40 °C) temperatures of the shelf. The primary drying temperature did not affect the size of pores and pore distribution for solutions with concentrations of 20, 30, 40, and 50%. The mean pore diameter of 60% freeze-dried gum hydrocolloid system increased from 745 to 973 µm with the increase of shelf temperature from −40 to −20 °C.	[88]:
Kiwi	Whole fruit (without peel)	−40 °C	n/a	12, 20, 42, 85, and 103 Pa	n/a	The increase of pressure in the range of 12–100 Pa resulted in a decrease of L* from 65.3 to 58.3, as well as a* values from −2.7 to −6.8, and the increase of b* from 22.3 to 28.3. The higher pressure affected the increase of penetration force for freeze-dried kiwi fruit from 4.3 to 16.2 N.	[121]:
Lime juice	Sample juice layer with a thickness from 0.3 to 1.1. cm	−30 °C	−61 °C	3 Pa	1–10 h	The freeze-drying of lime juice did not affect acidity (4.10–4.15 g citric ac./100 mL), antioxidant activity (17.5–18.3 mg ascorbic ac./100 mL), and carotenoids content (0.61–0.64 mg ∙100 mL-). Fresh juice and reconstituted freeze-dried juice did not significantly differ in relation to sensory attributes.	[133]:
Loco (Concholepas concholepas) (boiled)	Samples 1 × 1 × 0.5 cm Cubes 0.5 side cm	−25 °C	n/a	6,7 Pa and 9.6·10−4 Pa (AFD- atmospheric freeze-drying)	6.7−12 h	The pore surface of freeze-dried loco obtained at a low pressure was 0.32 m2 pores/m2, while after AFD, this value was half (0.16 pores/m2 material surface). The water absorption capacity of the freeze-dried sample was higher than 1.0 at a low pressure, while at AFD conditions, it was lower than 1.0.	[134]:
Maltodextrin sugar–agar solutions	Cube (10 × 10 × 10 mm) samples	−20, −40, and −80 °C, tempered at −80 °C before drying	Room temperature	10 Pa	48 h	The pore size and thickness of pore membranes of the freeze-dried system were reduced with a decrease of the freezing temperature. The system frozen at −80 °C was more resistant to compression than samples frozen at −40 and −20 °C.	[123]:
Orange puree	Puree, layer with a thickness of 0.5 mm	−45 °C—slow rate: a conventional freezer −38 °C—fast rate—a blast freezer	30, 40, and 50 °C	5 and 100 Pa	25 h at 30 °C, 7 h at 40 °C, 6 h at 50 °C	The color attributes L, C*, and h* of freeze-dried orange puree were affected by working pressure. The lower values of L* and higher C* were characteristic for samples dried at the high pressure of 100 Pa. The lower range of h* values between 80.3 and 82.6 was registered for the samples dried at higher pressure (100 Pa) and the temperature of the shelf below 50 °C. The lower pressure of 5 Pa and a higher temperature of 50 °C created more resistant to fracture a freeze-dried sample. The lower degradation of vitamin C was observed for samples dried at 40 and 50 °C than at 30 °C.	[14]:
Pepper	Samples and puree with layer of 5 mm	−25 °C	20, 40, and 60 °C	63 Pa	290 min (60 °C) 900 min (20 °C)	The red pepper freeze-dried at higher temperature 60 °C was characterized by lower values of L* (lightness =35.5), a* (redness =27.6), and b* (yellowness =23.8) than the sample dried at 20 °C (L* = 39.2, a* = 34.8, and b* = 27.0). Additionally, the increase in drying temperature caused a decrease of the total phenolic content (from 12.6 to 11.8 mg GAE/g d.m.) and antioxidant activity (EC50- concentration required to obtain a 50% antioxidant effect) from 21.7 to 26.1 mg d.m./mL).	[11]:
Potato	Cylindrical disks (2.5 cm diameter and 0.7 height)	−40 °C	−45, −30, −20, −10, −5, 0, 10, and 15 °C	100 Pa	72 h	The increase of a shelf temperature in the range from −45–15 °C caused an increase of apparent density of dried potato from 204.2 to 452.2 kg × m−3 and a decrease of apparent porosity from 0.863 to 0.698.	[93]
Rice (cooked)	The layer of 1.8 mm	−18 °C	90 °C	80 Pa (initial) and 20 Pa (final)	12 h	The freeze-dried rice had a better rehydration capacity than the freshly cooked sample. Freeze-drying caused the extensive breakage of the grains. The extent of breakage was dependent on the cooking method and was lower in freeze-dried parboiled rice (3.6–36.9%) than non-parboiled grain (50%).	[118]:
	n/a	−30 °C for 72 h, tempered for 1 h in liquid N2	n/a	4, 13, and 125 Pa	24 h	The bulk density of freeze-dried rice decreased from ~0.9 to ~0.8 for kernels boiled for 4 min and from ~0.6 to ~0.5 for kernels boiled for longer than 20 min with the decrease of applied pressure from 125 to 4 Pa. The porosity of dried kernels was the highest at low pressures.	[10]:
Strawberry	Whole fruits and slices (5 and 10 mm thick)	−40 °C	30, 40, 50, 60, and 70 °C	n/a	12–48 h	The color of strawberries and the volume reduction of fruits did not change in case of different drying temperatures. The percentage of collapsed samples exceeded 20% at drying temperatures higher than 50 °C.	[99]:
Yellow dates	Halves	−40 °C	−45, −30, −20, −10, −5, 0, 10, and 15 °C	100 Pa	72 h	The increase of a shelf temperature in the range from −45–15 °C caused a decrease of the apparent density of dried dates from 485.1.2 to 205.5 kg·× m−3, as well as an increase of apparent porosity from 0.709 to 0.864.	[93]:

n/a, not available.