Impact of Pretreatment and Drying Methods on Quality Attributes of Onion Shreds

Abstract

SummaryExperiments were conducted on dry untreated onion shreds (2 mm thickness) or treated with salt (5 % solution) and potassium metabisulphite (0.5 % solution) in convective drier at 50 °C ((46±4) % relative humidity (RH)), 55 °C ((35±4) % RH), 60 °C ((28±4) % RH) and 65 °C ((20±4) % RH), heat pump-assisted convective drier at 35 °C ((32±2) % RH), 40 °C ((26±2) % RH), 45 °C ((19±2) % RH) and 50 °C ((15±2) % RH) and microwave-assisted convective drier at four microwave power levels, i.e. 120, 240, 360 and 480 W. The quality parameters of the dried onion shreds, namely rehydration ratio, colour diff erence, pyruvic and ascorbic acid contents and sensory scores were evaluated. The quality of dehydrated onion shreds was observed to be comparatively be er when treated in heat pump drier at 50 °C, followed by that in microwave-assisted convective drier at 240 W and 50 °C, and last in convective drier at 60 °C. The onion shreds pretreated with potassium metabisulphite retained be er colour of the dried product irrespective of drying methods. Therefore, heat pump drying may be recommended as one of the best drying methods for onion shreds, because it maintains the fi nal product quality, which has practical importance for the food industry.

Optimization of Combined Drying for Lettuce Using Response Surface Methodology

“…; Tunde‐Akintunde ; Sahoo et al . ). For example, Wu and Zhang () utilized the pulsed electric field pretreatment to obtain the optimal parameters of freeze‐drying for potato.…”

“…Dak and Pareek (2014) adopted the microwave-vacuum combined drying technology to obtain effective moisture diffusivity. Meanwhile, different drying methods or pretreatments had a significant effect on drying time, rehydration capacity, shrinkage, color features and consumed energy (Doymaz 2008;Yan et al 2013;Izli et al 2014;Kianoosh et al 2014;Tunde-Akintunde 2014;Sahoo et al 2015). For example, Wu and Zhang (2014) utilized the pulsed electric field pretreatment to obtain the optimal parameters of freeze-drying for potato.…”

Onions: A Source of Flavonoids

“…The main concern in food drying is related to a loss of volatiles and lavors, changes in color and texture, and a decrease in nutritional value associated with the process. Hence, the efect of dehydration on onion quality was studied [115]. Mass production of dried foods is often accomplished through the use of convective dryers.…”

Flavonoids - From Biosynthesis to Human Health

“…The main concern in food drying is related to a loss of volatiles and flavors, changes in color and texture, and a decrease in nutritional value associated with the process. Hence, the effect of dehydration on onion quality was studied [115]. Mass production of dried foods is often accomplished through the use of convective dryers.…”