Comparison of hot air‐drying and freeze‐drying on the physicochemical properties and antioxidant activities of pumpkin (Cucurbita moschata Duch.) flours

Abstract

Freeze-drying and hot air-drying were applied in the preparation of pumpkin flours to investigate the effects of drying methods on the antioxidant activities and physicochemical properties. The antioxidant activities of methanol extracts from pumpkin flours were studied in terms of total antioxidant activity, reducing power, free radical scavenging, superoxide anion radical scavenging and metal chelating activities. Hot air-dried pumpkin flour showed stronger antioxidant activities than freeze-dried flour. The percentage inhibition of peroxidation in linoleic acid system by 15 mg mL )1 extracts from hot air-dried and freeze-dried pumpkin flours was found to be 92.4% and 86.1% after 120 h of incubation, respectively. Hot air-dried pumpkin flour exhibited higher reducing power, free radical scavenging and metal chelating activities than freeze-dried flour. This study also indicated that freeze-drying significantly reduced the browning and preserved the redness of pumpkin flours. Hot air-drying reduced the oil absorption capacity, water absorption and porosity of pumpkin flours, while it markedly increased the water solubility and bulk density.

Comparison of the Nutritional, Physico-chemical and Anti-nutrient Properties of Freeze and Hot Air Dried Watermelon (Citrullus lanatus) Rind

“…This increase in the solubility can be attributed to the increased degradation of starch during hot air drying. Similar results were obtained by 16 in the drying of pumpkin. The solubility of the samples was found to vary significantly.…”

Total phenolics, antioxidant capacity, colour and drying characteristics of date fruit dried with different methods

“…Although non-thermal freeze drying is often considered to be the best drying method for preserving heat sensitive compounds, the results show that higher total phenolic content and antioxidant capacity were obtained with thermal methods for date fruit. Que et al (2008) reported that hot air dried pumpkin flour contained higher total phenolic content and antioxidant activity than freeze dried sample, possibly due to production of Maillard products. The increase in antioxidant capacity as a result of drying might be caused by the formation of new antioxidant compounds (Albanese et al, 2013).…”

“…cause more phenolics to be extracted. In addition, the increase in phenolic content could be explained by the formation of Maillard reaction products, which would cause new phenolic compounds to form from precursors during thermal treatments (Que et al, 2008;Sultana et al, 2012). The highest phenolic content in microwave-dried dates might be because of the high temperatures reached in the during microwave treatment, which could cause greater cell disruption and lead to rupturing that releases phenolic compounds.…”

Effect of Drying on the Antioxidant Capacity and Concentration of Phenolic Compounds in Different Parts of the Erythrina americana Tree

“…This could be due to the conditions of the drying process, which may influence the antioxidant activity and TPC. Other studies have reported that the drying method, temperature and time of the treatment, type of extraction, and interactions among the different antioxidant reactions could be responsible for the difference in responses of the phenolic compounds to the Folin-Ciocalteu method (Balasundram et al 2006;Que et al 2008;Vega-Gávez et al 2009). …”