Abstract
The present study aimed to develop pretreatments and dehydration strategies for onions to retain the structure so that improved rehydration could be achieved with better quality attributes and shelf life. Effect of osmotic treatment at NaCl concentrations of 5, 10, 15 and 20 % for the duration of 60, 120, and 180 min and hydrocolloid coating (5, 10, 15 and 20%) on onion slices was studied. Osmotic pretreatments with 10% NaCl for 120 min followed by dipping in 5% gum Arabic solution were found optimum in increasing the total soluble solids content in onion slices for further effective dehydration. The pretreated onions were dried at temperatures of 50, 60, and 70°C using a tray dryer (air velocity of ∼1.5 m/s), drying kinetics and dried onion quality were evaluated. The results revealed that osmotic pretreatment and higher drying temperatures significantly increased the drying rate and decreased drying time for onion slices. However, the drying temperature of 60°C was optimum for reducing the drying time with better retention of ascorbic acid (62%), and pyruvic acid (77%) with a nearly 2-fold increase in total phenolics and total flavonoids compared to fresh onions. A positive change in color attributes and rehydration ratio was observed for osmo-hydrocolloid-treated and dried onion slices. Scanning electron microscopic images of fresh onion slices showed elongated well-arranged cells whereas in dried onions, cell walls were disrupted due to the sudden expulsion of moisture from the onion cells. The microstructure of osmo-hydrocolloid pretreated and dried onion cells showed less structural damage due to the protective effect of hydrocolloid coating and an increase in the solid content during osmotic treatment. Prospects of the current research could focus on exploring different hydrocolloids with innovative drying techniques to further enhance the nutritional and structural retention in dehydrated onions and the potential application of these strategies to other vegetables.
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Claims 9
Claim · model-written summary
A 10% NaCl osmotic pretreatment for 120 minutes followed by 5% gum Arabic increased onion total soluble solids optimally.
- Taxon
- onion
Allium cepae0 - Treatment
- 10% NaCl for 120 min followed by dipping in 5% gum Arabic solutione0
- Outcome
- total soluble solids contente0
- Direction
- increasinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Osmotic pretreatments with 10% NaCl for 120 min followed by dipping in 5% gum Arabic solution were found optimum in increasing the total soluble solids content in onion slices for further effective dehydration.”
Claim · model-written summary
Osmotic pretreatment and higher drying temperatures significantly increased onion slice drying rate.
- Taxon
- onionAllium cepae0
- Treatment
- osmotic pretreatment and higher drying temperaturese0
- Outcome
- drying ratee0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“osmotic pretreatment and higher drying temperatures significantly increased the drying rate and decreased drying time for onion slices.”
Claim · model-written summary
Osmotic pretreatment and higher drying temperatures significantly decreased onion slice drying time.
- Taxon
- onionAllium cepae0
- Treatment
- osmotic pretreatment and higher drying temperaturese0
- Outcome
- drying timee0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“osmotic pretreatment and higher drying temperatures significantly increased the drying rate and decreased drying time for onion slices.”
Claim · model-written summary
Drying at 60°C retained 62% of onion ascorbic acid.
- Taxon
- onionsAllium cepae0
- Treatment
- drying temperature of 60°Ce0
- Outcome
- retention of ascorbic acide0
- Direction
- better retentione0
- Value
- 62%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“drying temperature of 60°C was optimum for reducing the drying time with better retention of ascorbic acid (62%), and pyruvic acid (77%) with a nearly 2-fold increase in total phenolics and total flavonoids compared to fresh onions.”
Claim · model-written summary
Drying at 60°C retained 77% of onion pyruvic acid.
- Taxon
- onionsAllium cepae0
- Treatment
- drying temperature of 60°Ce0
- Outcome
- pyruvic acide0
- Direction
- better retentione0
- Value
- 77%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“drying temperature of 60°C was optimum for reducing the drying time with better retention of ascorbic acid (62%), and pyruvic acid (77%) with a nearly 2-fold increase in total phenolics and total flavonoids compared to fresh onions.”
Claim · model-written summary
Drying at 60°C nearly doubled onion total phenolics and total flavonoids relative to fresh onions.
- Taxon
- onionsAllium cepae0
- Treatment
- drying temperature of 60°Ce0
- Outcome
- total phenolics and total flavonoidse0
- Direction
- increasee0
- Value
- nearly 2-folde0
- Comparator
- fresh onionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“drying temperature of 60°C was optimum for reducing the drying time with better retention of ascorbic acid (62%), and pyruvic acid (77%) with a nearly 2-fold increase in total phenolics and total flavonoids compared to fresh onions.”
Claim · model-written summary
Osmo-hydrocolloid treatment improved dried onion color attributes and rehydration ratio.
- Taxon
- onionAllium cepae0
- Treatment
- osmo-hydrocolloid-treatede0
- Outcome
- color attributes and rehydration ratioe0
- Direction
- positive changee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A positive change in color attributes and rehydration ratio was observed for osmo-hydrocolloid-treated and dried onion slices.”
Claim · model-written summary
Drying disrupted onion cell walls.
- Taxon
- onionsAllium cepae0
- Treatment
- driede0
- Outcome
- cell walls were disruptede0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in dried onions, cell walls were disrupted due to the sudden expulsion of moisture from the onion cells.”
Claim · model-written summary
Osmo-hydrocolloid-pretreated dried onion cells showed less structural damage.
- Taxon
- onionAllium cepae0
- Treatment
- osmo-hydrocolloid pretreated and driede0
- Outcome
- structural damagee0
- Direction
- lesse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The microstructure of osmo-hydrocolloid pretreated and dried onion cells showed less structural damage due to the protective effect of hydrocolloid coating and an increase in the solid content during osmotic treatment.”
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