Effects of different drying treatments on total phenol content and antioxidant activity of Portulaca oleracea

Absrtact: Portulaca oleracea was treated by hot air drying, vacuum microwave drying and vacuum freeze drying respectively. The total phenol content, total antioxidant capacity, reduction capacity, DPPH scavenging capacity, hydroxyl radical scavenging capacity and superoxide anion radical scavenging capacity of the methanol extract of Portulaca oleracea powder were determined. The total phenol content and antioxidant capacity of Portulaca oleracea powder were studied by different drying methods. Influence.

The results showed that the content of total phenols in Portulaca oleracea powder prepared by microwave drying equipment was significantly higher than that of vacuum microwave drying and hot air drying.

The total antioxidant capacity, reduction capacity, DPPH and hydroxyl radical scavenging capacity of methanol extract of Portulaca oleracea powder prepared by vacuum freeze-drying method were significantly higher than those of Portulaca oleracea powder prepared by vacuum microwave and hot air drying method (P < 0.05), but the clearance of O-. by vacuum freeze-drying sample and vacuum microwave drying sample was higher than that by vacuum microwave drying method (P < 0.05). There is no significant difference in the removal rate. Considering the product quality and processing cost, the vacuum microwave drying method is more reasonable.

Key words: Portulaca oleracea microwave drying; hot air drying; vacuum microwave drying; vacuum freeze drying; total phenols; antioxidant activity

Portulaca oleracea is an annual fleshy herb of Portulaca oleracea. As a healthy functional vegetable, Portulaca oleracea is rich in polyphenols, flavonoids and polysaccharides. Besides being edible, it has certain medicinal value.

Portulaca oleracea powder can be added to noodles, bread and biscuits as functional ingredients to bring additional nutritional and health benefits to food. Among all kinds of drying methods, vacuum freeze-drying can maximize the nutrition and active ingredients of products, but the cost is relatively high; microwave drying method is fast, but in some cases it will cause the loss of active ingredients in food; the most widely used hot-air drying method is low-cost, but often leads to product quality degradation. Therefore, it is necessary to study the effects of these drying methods on the quality of Portulaca oleracea powder, especially the difference between antioxidant activity and phenolic compounds.

Phenolic compounds widely exist in various fresh fruits and vegetables, and are a kind of natural phytochemicals. The phenolic hydroxyl structure of phenolic compounds in plants can easily be oxidized into quinone structure, which consumes oxygen in the environment. At the same time, phenolic structure has a strong ability to capture free radicals, making phenolic compounds have strong antioxidant and free radical scavenging ability.

Studies have shown that phenolic compounds may have antioxidant, preventive effects on tumors and cardiovascular diseases. At present, there are few studies on phenolic compounds and antioxidant changes in dry powder of Portulaca oleracea. In this study, the total phenolic content and antioxidant capacity of dry powder of Portulaca oleracea produced by different drying methods were compared in order to provide theoretical basis for the actual production and application of dry powder of Portulaca oleracea.