Effects of heating on the total phenolic content, antioxidant activities and main functional components of simulated Chinese herb candy during boiling process

The effects of heating (100–140 °C/10–180 min) on functional component contents, total phenolic content (TPC) and antioxidant activities of six simulated Chinese herb candies containing honeysuckle, chrysanthemum, dandelion, liquorice, mulberry leaf and tangerine, respectively were studied, which revealed that TPC and antioxidant activity of candies significantly increased (p < 0.05) with increasing heating temperature (> 130 °C) and time (> 40 min) during boiling process. After heating at 140 °C/180 min, TPC increased 2–3 times compared with that of unheated samples, while 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical and 2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferric reducing antioxidant power (FRAP) increased 2–9, 2–5 and 3–6 times, respectively. Contents of the main functional components including rutin, glycyrrhizic and chlorogenic acids and naringin in herb candies decreased 6–85% after heating, while glycyrrhetinic acid content increased by 60% and 157% upon heating at 130 °C and 140 °C/180 min, respectively. Significant enhancements in TPC and antioxidant activities of candies during boiling process might be attributable to Maillard reaction product formation. These results would be helpful to effectively guide the industrial production of Chinese herb candies, and to maintain their health benefits.