The effect of food additives and cooking on the antioxidant properties of purslane

Abstract

Purpose This paper aims to study the effect of cooking and food additives, such as lemon juice and vinegar, on phenols and flavonoids contents and antioxidant activity of purslane. Design/methodology/approach The Folin–Ciocalteu method was used to determine total phenols content (TP), while total flavonoid content (TF) was determined by the aluminum chloride method. Two methods were used for determination of antioxidant activity: DPPH (1, 1-diphenyl-2-picrylhydrazyl) assay to determine radical scavenging activity, and ferric-reducing antioxidant power (FRAP) to measure the reducing power. Findings According to the results, leafs had higher values of TP, TF and antioxidant activity than aerial parts. Both lemon juice and vinegar retracted antioxidant properties of leafs. TP and TF of leaves showed deterioration after treatment with lemon by 58% and 21.8%, respectively, and FRAP and radical scavenging activity decreased by 75.8% and 74.5%, respectively (p < 0.001). Also, TP, TF, FRAP and DPPH radical scavenging activity decreased in leaves by 82.2%, 30.5%, 87.8% and 90.9%, respectively, after treatment of leaves with vinegar. TF increased after cooking in studied parts, where no significant statistical difference was observed in TP and antioxidant activity (DPPH assay and FRAP) of cooked aerial parts. Adding lemon juice after cooking increased antioxidant properties of purslane (p < 0.001). Originality/value Purslane has antioxidant activity because it is rich in polyphenols and flavonoids. Effects of food additives and cooking were studied using different measurements. According to the authors’ knowledge, this is the first work that studied the effect of food additives on antioxidant properties of purslane.

Phytochemical Composition and Antioxidant Activity of Portulaca oleracea: Influence of the Steaming Cooking Process

“…In a previous work comparing the raw, boiled, and blanched P. oleracea , it was observed that the raw sample had a higher TPC value (23 mg GAE/g DE) compared to the values of the cooked samples (boiled 19 mg GAE/ g DE and blanched 10 mg GAE/g DE) [ 23 ]. In another study, Naser Aldeen et al obtained slightly higher values for cooked than raw purslane (13.13 mg GAE/g DE and 12.75 mg GAE/g DE, respectively) [ 24 ].…”

“…A previously reported value in an ABTS assay for raw purslane was 102.7 µmol TE/g DE, lower than that obtained in our study [ 43 ]. In another work on aerial parts of Portulaca oleracea , the cooking process with lemon juice as additive increased the antioxidant activity compared to raw samples in the DPPH assay [ 24 ]. The decrease in antioxidant activity observed after the steaming process is in agreement with the decrease in phenolic content ( Table 2 ).…”

“…The impact of cooking treatment on vegetables can cause changes in nutritional composition and levels of bioactive compounds [ 21 ]. Studies on the effects on cooking have been carried out in Portulaca oleracea , observing differences according to the type of cooking, but mainly focus on boiling and bleaching, or cooked with some food additives such as lemon juice or vinegar [ 22 , 23 , 24 ].…”

Nutritional Value, Chemical Composition and Cytotoxic Properties of Common Purslane (Portulaca oleracea L.) in Relation to Harvesting Stage and Plant Part

“…Other valuable components of purslane edible parts include minerals, such as calcium, potassium and phosphorus, macronutrients such as proteins and carbohydrates [5], as well as tocopherols, carotenoids and ascorbic acid [6,7]. Moreover, phenolic compounds and oleracein derivatives of extracts of purslane leaves have been attributed with antioxidant properties [8], while their content may be affected by cooking and food additives [9]. P. oleracea is tolerant under stress conditions, such as heat, drought and salinity stress, a trait that could be useful within the ongoing climate change context and provide alternative solutions to farmers in climate-affected regions [10].…”