【作者】 朱学伸；

【导师】 周光宏；

【作者基本信息】 南京农业大学 ， 食品科学， 2007， 硕士

【摘要】 宰后乳酸积累、pH下降在“musele”到“meat”这个过程中是一个非常重要的指标。所以屠宰后肌肉的变化及其对以后肉品质的影响是肉类科学研究的核心内容。在肉的成熟期间，乳酸的变化尚不清楚。有必要了解冷却肉乳酸含量及影响因素的变化情况。本论文包括三部分，第一部分建立了冷却肉中乳酸含量的反相高效液相色谱分析方法。第二部分主要是研究了不同类型肌肉4℃成熟条件下成熟期间pH、乳酸含量以及游离氨基酸的变化。第三部分研究了不同包装方式对肌肉4℃成熟条件下pH、乳酸含量、游离氨基酸含量及肉品质变化的影响。为了测定肉中乳酸含量，建立了肉中乳酸提取以及反相高效液相色谱测定的方法。冷却猪肉用1 moL·L^-1高氯酸水溶液匀浆去除蛋白质及脂肪后，5000 g离心，并过0.25μm纤维素膜，然后以高效液相色谱反相柱分离，通过紫外检测器检测。该测定方法回收率为95.5％～102.3％，相对标准偏差为3.2％～5.7％，日内测定CV为1.09％，日间测定CV为1.28％。该方法应用于冷却猪肉乳酸含量测定获得较好的效果。研究了类型类型冷却肉分别处于4℃成熟期间pH和乳酸含量及游离氨基酸含量的变化。结果表明肌肉类型不同，宰后物质代谢有显著不同。鸡胸肉乳酸含量从11.3mmoL·kg^-1提高到24.7 mmoL·kg^-1，鸡腿肉乳酸含量则则从6.9 mmoL·kg^-1提高到9.4 mmoL·kg^-1，相应鸡胸肉pH从6.76下降到5.79，鸡腿肉pH从最初6.83下降到6.13，在3h后成熟期间保持稳定。伴随成熟游离氨基酸含量显著提高，但在肌肉缓冲能力的作用下，pH保持稳定。对猪背最长肌分别进行普通托盘和真空包装两种处理，研究了4℃成熟期间pH和乳酸含量、菌落总数、色泽、汁液流失和煮制损失的变化。结果表明普通托盘包装的肉汁液流失低，L^*较高，但微生物菌落总数增长较快。真空包装可有效抑制微生物菌落总数增长，但汁液流失较高、肉色L^*较低。两种包装方式下猪背最长肌煮制损失没有显著差别，并且pH和乳酸在冷却成熟期间亦无显著变化，伴随成熟游离氨基酸含量显著提高。更多还原

【Abstract】 It is well known that the chain of events that leads to the conversion of muscle to meat is complex, and one of the most important post-mortal changes in muscles is a decrease in pH value due to the production of lactic acid within 24 h after slaughter. The fall in pH during the post-mortem reaction sequence is a function of the amount of acid formed. Although it is recognized that As a result of post-mortem metabolism, glycogen and ATP levels decline, and lactic acid accumulates in the muscle, little is known about changes of lactic acid content in the muscles during aging later in our country. Three parts were included in this paper: （1）A reversed-phase high performance liquid chromatographic （RP-HPLC） method was established to determine lactic acid in chilled meat. （3）Effect of Broiler body part on pH, Lactic acid and free amino acid were investigated. Pectoralis muscles and broiler Biceps femoris muscles from chicken carcasses were conventionally packaged respectively and stored at 4℃. （3）Effect of packaging methods on meat color, purge loss, cooking loss, colony forming unit, pH and Lactic acid were investigated.A reversed-phase high performance liquid chromatographic （RP-HPLC） method was established to determine lactic acid in chilled meat. The solution of samples pretreated with the solution of 1 moL·L^-1 perchloric acid （PCA） was separated through RP-HPLC.The recovery rate was 95.5%-102.3%, and relative standard deviation was 3.2%-5.7%, The CV within-day and between-day was 1.09% and 1.28% respectively. The method was successfully used in the analysis of chilled pork.Effect of body part on pH, Lactic acid and free amino acid were investigated. Broiler breast muscles and broiler leg muscles from chicken carcasses were conventionally packaged respectively and stored at 4℃. Results indicated that broiler breast muscles pH fell from 6.76 down to 5.79, while leg musle fell from 6.83 to 6.13, and concentration of lactic acid in broiler breast muscle rase from 11.3 mmoL·kg^-1 to mmoL·kg^-1, while lactic acid in leg muscle rase from 6.9 mmoL·kg^-1 to 9.4 mmoL·kg^-1, but a larger amount of free amino acid increases remarkably at the period of ageing. Effect of packaging methods on meat color, pH, Lactic acid purge loss, cooking loss and colony forming unit were investigated. Longissimus dorsi steaks from pork carcasses were vacuum packaged and conventionally packaged respectively. Results indicated that Meat pH and concentration of lactic acid varied little during aging at 4℃for both vacuum and conventionally packaged steaks. Conventionally packaged steaks had lower purge loss, and higher L* value, but a larger number of bacteria than vacuum packaged steaks at the later period of ageing. Vacuum packaging can improve the shelf life of pork but a negative effect on meat quality, such as purge loss and color. However, cooking loss has no significant difference. A larger amount of free amino acid increases remarkably at the period of ageing.更多还原