铁棍山药POD特性及褐变抑制研究

Study on Characteristics of Peroxidase in Dioscorea opposita Thunb. cv. Tiegun and Its Browning Inhibition

以铁棍山药为试材,采用分光光度法,研究了与其褐变相关的过氧化物酶(POD)的特性以及抑制剂对POD活力的影响。结果表明:铁棍山药POD对愈创木酚的最适反应pH为5.0,温度为50℃,在80℃下温育5 min基本失活,酶促反应的最佳底物为愈创木酚,且最适浓度为0.04 mol/L,Km值为0.012 mol/L;L-半胱氨酸盐酸盐和抗坏血酸对POD均有很强的抑制作用,柠檬酸对POD的抑制作用次之,植酸对POD的抑制作用再次之,而氯化钠、EDTA-2Na对POD的抑制作用不明显。为抑制由POD引起的鲜切铁棍山药片的褐变,应在较低(<20℃)或较高温度(>70℃)下进行操作,鲜切片的无硫护色剂首选L-半胱氨酸盐酸盐或抗坏血酸,其次是柠檬酸,第三是植酸,护色剂溶液pH值应低于5.0或高于6.4。

In this paper,Dioscorea opposita Thunb.cv.Tiegun was used as experimental materials,and the characteristics of peroxidase related to fresh cut slices browning and the effects of inhibitors on POD activity were studied.The results showed that： The optimum reaction pH of POD for substrate guaiacol in D.opposita.Thunb.cv.Tiegun was 5.0.The optimum reaction temperature was 50℃.Its activity was nearly out when it was incubated for 5min at 80℃.The optimum substrate of enzymatic reaction was guaiacol,and the best concentration was 0.04mol/L and Km was 0.012mol/L.L-cysteine hydrochloride and ascorbic acid had the strongest inhibition effect on POD activity,citric acid had stronger inhibition effect,and the inhibition effect of phytic acid on POD was lower,while NaCl and EDTA-2Na had no significant inhibition effect.So,in order to inhibit fresh cut slices browning which results from POD,fresh cutting and other operations should be done at the lower（〈20℃） or the higher（〉70℃） temperature;L-cysteine hydrochloride or ascorbic acid was the best anti-browning reagent without sulphate for fresh cut slices,the second was citric acid and the third was phytic acid;the pH of anti-browning reagent solution should be lower than 5.0 or higher than 6.4.