Li Xuejun, Bickerdike Ralph, Lindsay Emma, Campbell Patrick, Nickell David, Dingwall Alastair, Johnston Ian A
Fish Muscle Research Group, Gatty Marine Laboratory, School of Biology, University of St. Andrews, Fife, Scotland, KY16 8LB, United Kingdom.
J Agric Food Chem. 2005 Aug 24;53(17):6844-50. doi: 10.1021/jf050743+.
A simple HPLC method is presented to quantify the low concentration of hydroxylysyl pyridinoline (PYD) cross-links in Atlantic salmon (Salmo salar L.) muscle. The method involved the extraction of tissue with NaOH prior to hydrolysis, which greatly reduced the amount of protein to be hydrolyzed and made downstream operations easier and more reproducible. The concentration of PYD was 426 pmol g(-)(1) dry mass muscle in post-rigor muscle stored at 0 degrees C and sampled 3 d after death. Hydroxproline (HYP) concentration was determined following NaOH extraction as a measure of collagen content. In post-rigor samples, the alkaline-insoluble HYP fraction comprised 18.3% of the total HYP. Scanning electron microscopy revealed shrinkage of muscle fibers and a retraction of the connective tissue matrix in smoked salmon. PYD concentration was relatively resistant to processing to the smoked product, decreasing by around 11.7%, as compared to a 22.2% decrease in HYP. There was a positive correlation between PYD concentration and the firmness of post-rigor muscle samples as measured by an instrumental texture analyzer, explaining 25% of the total variation. A weaker but still significant correlation was found between PYD concentration and firmness in the smoked product. There was no relationship between fillet firmness and total collagen concentration, although the correlation with HYP in the alkaline-insoluble fraction was significant at the 6% level (P = 0.057). Our results indicate that only 1-3% of collagen molecules are linked by nonreducible mature cross-links in harvest size farmed Atlantic salmon and that PYD concentration is an important raw material characteristic for flesh quality.
本文介绍了一种简单的高效液相色谱法，用于定量分析大西洋鲑（Salmo salar L.）肌肉中低浓度的羟赖氨酸吡啶啉（PYD）交联物。该方法在水解前用氢氧化钠提取组织，这大大减少了待水解的蛋白量，使下游操作更简便且可重复性更高。在0℃储存、死后3天取样的僵硬后肌肉中，PYD的浓度为426 pmol g(-)(1)干质量肌肉。提取氢氧化钠后测定羟脯氨酸（HYP）浓度，作为胶原蛋白含量的指标。在僵硬后样品中，碱不溶性HYP部分占总HYP的18.3%。扫描电子显微镜显示，烟熏三文鱼的肌肉纤维收缩，结缔组织基质回缩。PYD浓度对加工成烟熏产品相对抗性较强，下降约11.7%，而HYP下降22.2%。通过仪器质构分析仪测量，PYD浓度与僵硬后肌肉样品的硬度呈正相关，解释了总变异的25%。在烟熏产品中，PYD浓度与硬度之间存在较弱但仍显著的相关性。鱼片硬度与总胶原蛋白浓度之间没有关系，尽管与碱不溶性部分的HYP的相关性在6%水平上显著（P = 0.057）。我们的结果表明，在收获规格的养殖大西洋鲑中，只有1-3%的胶原蛋白分子通过不可还原的成熟交联键连接，并且PYD浓度是鱼肉品质的重要原料特性。
