Fukumoto Lana R, Toivonen Peter M A, Delaquis Pascal J
Food Research Program, Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, 4200 Highway 97, Summerland, British Columbia, Canada V0H 1Z0.
J Agric Food Chem. 2002 Jul 31;50(16):4503-11. doi: 10.1021/jf011415m.
Cut tissues from distinct anatomical locations in iceberg lettuce (Lactuca sativa L.) were subjected to washing in cold (4 degrees C) and warm (47 degrees C) water with or without chlorine to assess their propensity to discoloration during storage. Total protein (Bradford method) and phenolic (TPH; Folin-Ciocalteu method) contents and polyphenol oxidase (PPO; spectrophotometric method using catechol as a substrate), peroxidase (POD; guaiacol substrate), and phenylalanine ammonia-lyase (PAL; phenylalanine substrate) activities were determined in photosynthetic and vascular tissue from outer and inner leaves. Unprocessed photosynthetic and inner leaf tissues had significantly higher (P < 0.05) levels of protein and TPH and PPO and POD activities than vascular and outer leaf tissues. PAL activities (on a fresh weight basis) were similar in all tissues. Changes in browning (light reflectance measurement) and phenolic metabolism in all four tissue types were observed during aerobic storage at 5 degrees C over 10 days. PAL activity increased in all tissues after 1-2 days of storage and then gradually decreased. POD activity also increased steadily for the storage duration. Protein content and PPO activity remained constant. Edge browning (measured with a Minolta Chroma Meter) and TPH increased in all tissues, especially in outer vascular tissue. Cut photosynthetic and vascular tissues washed at 4 and 47 degrees C with and without 100 microg mL(-1) chlorine for 3 min were analyzed during 7 days in storage at 5 degrees C. Enzyme activities and accumulation of phenolics in all tissues washed at 47 degrees C were significantly (P < 0.05) lower compared to controls or tissues washed at 4 degrees C. Chlorine had no additional effect at 47 degrees C but significantly (P < 0.05) reduced browning and accumulation of phenolics in lettuce washed at 4 degrees C. These results showed that inherent differences between tissues affect phenolic metabolism and browning in stored, fresh-cut lettuce.
将来自生菜（Lactuca sativa L.）不同解剖位置的组织块置于含氯或不含氯的冷水（4℃）和温水（47℃）中冲洗，以评估其在储存期间变色的倾向。采用考马斯亮蓝法测定总蛋白含量，福林 - 酚法测定酚类物质（TPH）含量，以邻苯二酚为底物用分光光度法测定多酚氧化酶（PPO）活性，以愈创木酚为底物测定过氧化物酶（POD）活性，以苯丙氨酸为底物测定苯丙氨酸解氨酶（PAL）活性，检测外叶和内叶光合组织及维管组织中的上述指标。未处理的光合组织和内叶组织中蛋白质、TPH含量以及PPO和POD活性显著高于维管组织和外叶组织（P < 0.05）。所有组织中PAL活性（以鲜重计）相似。在5℃有氧储存10天期间，观察了所有四种组织类型的褐变（光反射率测量）和酚类代谢变化。储存1 - 2天后，所有组织中PAL活性均升高，随后逐渐下降。在整个储存期间，POD活性也稳步增加。蛋白质含量和PPO活性保持不变。所有组织的边缘褐变（用美能达色差仪测量）和TPH均增加，尤其是外维管组织。将在4℃和47℃下用或不用100 μg mL(-1)氯冲洗3分钟的切割光合组织和维管组织在5℃下储存7天进行分析。与对照或在4℃下冲洗的组织相比，在47℃下冲洗的所有组织中酶活性和酚类物质积累均显著降低（P < 0.05）。在47℃下氯没有额外作用，但在4℃下冲洗的生菜中，氯显著降低了褐变和酚类物质积累（P < 0.05）。这些结果表明，组织之间的固有差异会影响新鲜切割生菜储存期间的酚类代谢和褐变。
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