Review of the effects of various pretreatment and drying techniques on the qualities of dried pomegranate (<i>Punica granatum</i> L.) arils

Buhle Maphosa; Alemayehu Ambaw; Umezuruike Linus Opara; Buhle Maphosa; Alemayehu Ambaw; Umezuruike Linus Opara

doi:10.48130/TIH-2023-0026

Figures (6) Tables (6)

Figure 1.
A visual representation of the drying processes of solid materials.
Figure 2.
A typical breakdown of the material balance throughout the drying process for pomegranate aril.
Figure 3.
A classification of the numerous pretreatment techniques utilized in the drying process for pomegranate aril.
Figure 4.
This image depicts a sample of wild pomegranate arils being dried in a solar tunnel drier. Reprinted from Thakur et al.^[102].
Figure 5.
Illustration of dried pomegranate arils that have been dried using different methods. (a) Freeze drying, (b) vacuum drying, and (c) hot air drying. Adapted from Ozay-Arancioglu et al.^[97].
Figure 6.
Different types of storage bags for dried pomegranate arils. (a) Aluminum-laminated polyethylene pouches, (b) vacuum-sealed aluminum-laminated polyethylene pouches, (c) gunny bags and (d) transparent polyethylene pouch. From Thakur et al.^[144], modified.

Nutrient	Value	Unit
Water	77.9	g
Energy	346	kJ
Protein	1.67	g
Total lipid fat	1.17	g
Ash	0.53	g
Total dietary fiber	4	g
Total sugar	13.7	g
Calcium	10	mg
Phosphorus	36	mg
Magnesium	12	mg
Iron	0.3	mg
Potassium	236	mg
Sodium	3	mg
Zinc	0.35	mg
Vitamin C	10.2	mg
Vitamin K	16.4	µg
Vitamin E	0.6	mg
Vitamin B-6	0.075	mg
Total choline	7.6	mg
Folate	38	µg
Adapted from United States Department of Agriculture (Agricultural Research Service), FoodData Central^[52].

Table 1.

The nutritional composition of 100 g of pomegranate arils.

Pretreatment method	Pretreatment	Drying technique	Key findings	Reference
Blanching	Water blanching at 90 and 100 °C	Hot air oven drying	Blanched samples had a shorter drying time.	[24]
	Water blanching at 80 °C	Hot air oven dryer	Blanched samples had higher phytonutrient retention than unblanched samples.	[69]
	Blanching using 0.1% citric solution at 80 ± 2 °C	Cabinet tray dryer	Drying process was shorter for blanched samples and there was a higher rate of bioactive compounds.	[57]
Sulphuring	1% potassium metabisulphide	Solar drying Cabinet tray dryer Freeze dryer	Fruit of cv. Ganesh 1% potassium metabisulphide was of the highest quality and the highest acceptance.	[23]
Blanching and Sulphuring	Hot water blanching 85 °C and 0.2% potassium metabisulphate	Mechanical dryer Solar dryer	Keeping quality of mechanically dried arils was higher than the solar-dried arils.	[70]
	Steam blanching, potassium metabisulphide and 0.3% Sulphur fumigation	Cabinet tray dryer	The highest dried aril quality was obtained from the combination of steam blanching and 0.3% Sulphur fumigation.	[71]
	Steam blanching, sulphuring at 0.3%	Vacuum dryer Hot oven dryer Sun drying Poly-tent house drying Room drying	Sun drying had the highest moisture content reduction and the highest overall acceptance.	[72]
	Hot water blanching 85 °C, potassium metabisulphite varying from 0.25% to 1%	Hot air oven dryer	The best treatment was blanching in hot water at 85 °C for 1 min and then dipping the arils in 0.25% potassium metabisulphite.	[70]
	Steam blanching, sulphuring	Sun drying Cabinet dryer	Blanching reduced drying time. Cabinet drying of blanched samples without sulphuring was considered optimum for anthocyanins.	[73]
Acidic solution	2%, 3% and 4% citric acid	Cabinet tray dryer	3% acidic treatment was found to be the most acceptable.	[56]
Microwave	100 and 200 W.	Hot air oven dryer	200 W pretreatment resulted in minimum energy utilization and drying time.	[74]
	100 and 200 W	Hot air oven dryer	200 W had the highest drying rate.	[75]
Osmotic treatment	Sugar syrup, freezing at minus 18 °C	Open sun drying, Solar tunnel dryer, Cabinet tray dryer	Osmotic treatment and cabinet tray dryer produced dried arils with better physicochemical and sensory qualities.	[63]
	• 100% pomegranate juice • 50% pomegranate and 50% chokeberry juice • 50% pomegranate and 50% apple • 50% apple and 50% chokeberry • 75% apple and 25% chokeberry	Freeze drying Convective pre-drying vacuum microwave finish drying Vacuum-drying and freeze drying	Pomegranate and chokeberry concentrated juice improved the quality of the dried arils.	[12]
	Sucrose solution	Hot air oven drying	Pretreatment increased the drying time of the samples.	[64]

Table 2.

Key findings in pomegranate aril pretreatment and drying studies.

Cultivar	Drying method	Drying time (h)	Drying condition	Initial moisture content (%)	Final moisture content (%)	Key findings	Reference
Wonderful	Freeze dryer	96	−80 °C 5,999.1 Pa	74.7 (w.b.)	−	FD showed a higher color shift (19.6% ± 2,77%) at week 4 compared to hot air drying at week 0.	[94]
Ganesh, Bhagwa and Arakta	Freeze dryer	24−48	−45 °C	79.9 (w.b.) 80.5 (w.b.) 78.9 (w.b.)	9.65−9.9 (w.b.) 9.8−10.2 (w.b.) 9.8−9.9 (w.b.)	Arakta pre-treated with 1% potassium metabisulphide had the highest ascorbic acid concentration (6.81 ± 0.07 mg 100 g⁻¹).	[23]
Assiuty	Freeze dryer	36	−70 °C	−	−	TA (18.80, 2.80 mg 100 g⁻¹), TP (608.09a, 41.26 mg 100 g⁻¹), DPPH (68.91, 0.72%), and ABTS (2,956.59c, 120 mol trolox 100 g⁻¹) were all higher in frozen pomegranate arils than in freeze-dried arils.	[95]
Mollar de Elche		24	−60 °C, 65 Pa,	81.5 (w.b.)	−	FD showed higher anthocyanin content (646 mg kg⁻¹) compared to osmotic drying and conventional drying.	[12]
Hicaznar		36	−20 °C, 100 Pa for 12 h −70 °C, 0.26 Pa	76.96 (w.b.)	10 (w.b.)	Arils dried using FD had the highest magnesium content (96.17 ± 6.95 mg kg⁻¹), manganese content (0.96 ± 0.05 mg kg⁻¹) and zinc content (3.93 ± 0.07 mg kg⁻¹) compared to sun drying, hot air drying and vacuum drying.	[91]
Keben	Freeze dryer	57	−55 °C	77.6 ± 1 (d.b.)	20 ± 1 (d.b.)	FD had lower bioactive recovery during in-vitro gastrointestinal digestion (TPC of 2.92%, ABTS of 6.12% and CUPRAC of 38.85%) compared to vacuum drying, hot air drying and ultrasound-assisted vacuum drying.	[97]
Keben	Vacuum dryer	10.8	55 °C	77.6 ± 1 (d.b.)	20 ± 1 (d.b.)	Vacuum drying had the highest bio accessibility recovery of bioactive compounds at 10.32% compared to HAD, FD and ultrasound-assisted vacuum drying.	[97]
Hicaznar	Vacuum dryer	3.7 4.6 7.8	75 °C 65 °C 55 °C 85,000 Pa	78.1 ± 0.2 (w.b.)	16 (w.b.)	Drying temperatures of 75°C resulted in higher degradation of anthocyanins, phenolic compounds and antioxidant capacity (20.0%, 51.0%, 29.7% ± 0.28% respectively).	[99]
Hicaznar	Vacuum dryer	24	55 °C 3 500 Pa	76.96 (w.b.)	10 (w.b.)	FD had the highest quality attributes such as TAC-1288.73 mg/kg) compared to VD and HAD however, due to physical changes that were undesirable physical changes, VD and HAD are recommended for pomegranate aril drying.	[91]
Wild pomegranates (cultivar- unspecified)	Vacuum dryer	13	42 ± 2 °C	−	−	VD had a higher sensorial overall acceptance (17.1) compared to sun drying (16.2) and room temperature (12.6).	[72]
Bassein	Sun drying	17		−	15.73 (unspecified)	Drying rate of pomegranate arils is affected by tray load and the recommended tray load is 1.25 kg m⁻²	[73]
Wild pomegranates (cv. Unspecified)	Solar poly-tunnel	140	14.9−28.4 °C 48.5%−74% -RH 0.639−0.944 -wind speed	−	−	Arils dried in the solar poly-tunnel had higher ascorbic acid, anthocyanins, and phenol content, 12.7 mg 100 g⁻², 28.12 mg 100 g⁻², and 108.60 mg 100 g⁻² respectively than open sun drying.	[100]
Sefri	Indirect solar dryer	75 10 6 4	40 °C 50 °C 60 °C 75 °C	78 ± 0.1(w.b.)	−	The optimal water activity for drying and storing arils is 0.3684 ± 0.03.	[101]
Wild pomegranates (cv. Unspecified)	Solar tunnel	−	30−45 °C	−	−	Arils from the Karsog location had the highest TSS, sugars, anthocyanin, total phenols and antioxidant activity	[102]
−	Microwave	2.3 1.3 0.7	270 W 450 W 630 W	70.25 ± 0.5(w.b.)	10(d.b.)	Color changes increased from 6.77−13.11 with an increase in microwave power from 270−630 W and were lower compared to arils dried using HAD.	[85]
Hicaz	Microwave	1.2 0.6 0.4	210 W 350 W 490 W	23.93 ± 1.4 (unspecified)	22.2 (unspecified)	Based on quality parameters, a microwave drying power of 350 W was recommended for drying pomegranate arils.
Sweet acid (cv. Unspecified)	Infrared	4.3 2.2 1.6	50 °C 60 °C 70 °C	78 ± 0.2 (w.b.)	9 ± 0.2 (d.b.) 22.2 (unspecified)	Drying time for infrared drying was less than for HAD.	[103]
Hicaz	HAD	24	50, 60, 70 °C at 1.0 m/s air velocity	−	−	To obtain better dried aril quality, 60 °C was recommended for drying pomegranate arils.	[104]
Wild pomegranates (cv. Unspecified)	HAD	16.5	42 ± 2 °C	−	−	Sun drying resulted in a maximum loss of moisture compared to VD, HAD, poly-tent house drying and room drying.	[72]
Wild pomegranates (cv. Unspecified)	HAD	10	62 ± 2 °C	−	−	HAD achieved the highest total soluble solids (39.6°Brix) and drying rate compared to solar drying and open sun drying.	[105]
Keben	HAD	5	55 °C; with 1.3 m s⁻¹ constant air velocity	77.6 ± 1 (d.b.)	20 ± 1 (d.b.)	In comparison to hot air oven drying, ultrasound-assisted vacuum drying and freeze-drying have higher quality characteristics.	[97]
Bassein seedless	HAD	5−6	60 ± 5 °C. Airflow in the dryer was 1.2−1.8 m s⁻¹.	−	8.98 ± 0.091	For the finest preparation of anardana, blanched samples (with sulphur) should be dried in a cabinet.	[73]
Mollar de Elche	Vacuum- microwave	−	240, 360, 480 W and pressure ranging from 4,000−6,000 Pa	80.4 (w.b.)	−	Arils dried using vacuum microwave drying at 240 W had the highest sensorial scores for odour and aroma at 3.1 and 5.6 respectively.	[106]

Table 3.

A summary of the many techniques for drying pomegranate arils.

Model name	Model expression	Reference
Page	MR = exp(-ktⁿ)	[129]
Newton	MR = exp(-kt)	[130]
Henderson and Pabis	MR = aexp(-kt)	[131]
Midili et al	MR = aexp(-ktⁿ) + bt	[132]
Wang and Singh	MR = 1 + at + btⁿ	[133]
Two Term	MR = (aexp(-k₀ t) + bexp(-k₁ t))	[134]
Logarithmic	MR = aexp(-kt) + c	[135]

Table 4.

A summary of the mathematical equations that are most commonly used to model the drying kinetics of pomegranate arils is shown here.

Cultivar	Drying method	Drying parameters	Pretreatment	Suitable drying model	Reference
cv. Hicaz	HAD	55, 65, 75 °C	0.1% citric acid	Page and Modified Page	[57]
cv. Hicaznar	HAD	55, 65, 75 °C	−	Sigmoid	[116]
−	HAD	55, 55, 60 °C	−	Page	[137]
−	HAD	50, 60, 70 °C	−	Page	[85]
	MD	270, 450, and 630 W	−	Page	[85]
cv. Hicaznar	VD	55, 65, 75 °C	Hot water blanching	Page and Modified page	[69]
−	HAD	45, 50, 55, 60, 65, and 70 °C	Microwave	Midili	[75]
cvs. Acco, Herskawitz and Wonderful	HAD	60 °C	Hot water blanching (at 90 and 100 °C, each for 30 s and 60 s)	Logarithmic, Page, Midili for unblanched arils Midili and Page for blanched	[24]

Table 5.

A synopsis of the results of mathematical modeling of the kinetics of drying pomegranate arils.

Drying method	Drying temperature	Packaging material	Storage period (months)	Shelf-life performance	Reference
MC drier Solar cabinet drier Open sun	62−64 °C 50−55 °C 18−24 °C	Aluminum laminated polyethylene pouch, polyethylene pouches and thermoform trays.	6	Aluminum laminated polyethylene pouches were best for packaging.	[105]
Microwave-vacuum drying	38 °C	High-density polypropylene (HDPP) and aluminum laminated polyethylene (ALP).	3−6	Pomegranate arils stored showed that ALP is more protective than HDPP.	[35]
Solar tunnel	30−45 °C	Gunny bags, aluminum laminated polyethylene pouches (ALP) and vacuum-sealed aluminum laminated polyethylene pouches (ALPV).	12	Both refrigerated and ambient storage can securely preserve dried pomegranate samples for 12 months. Best performance was ALP with vacuum and cold storage.	[144]
Hot air dryer	60 °C	Aluminum laminated polyethylene pouch (ALP), polyethylene pouch (PEP), and thermofoam tray (TT) covered in shrinkable polypropylene transparent sheet.	6	Moisture absorbers aid in the preservation of samples.	[100]

Table 6.

A list of the several types of containers used to store dried pomegranate arils.