【作者】 徐为民；

【导师】 周光宏； 徐幸莲；

【作者基本信息】 南京农业大学 ， 食品科学， 2008， 博士

【摘要】 南京板鸭是我国特有传统肉制品,也是世界著名的腌腊肉制品,历史悠久、风味独特,在国内及东南亚地区享有很高的声誉。但时至今日,落后的传统工艺和手工作坊的生产方式严重影响了南京板鸭的可持续发展。究其原因,主要是对南京板鸭传统加工工艺的科学发展观的认识不足,有关南京板鸭加工的科学理论研究极少,导致生产工艺的改进和工艺参数的优化缺少理论指导。本课题通过板鸭加工过程中,脂类物质的变化规律、内源脂肪酶类的特性、风味成分动态变化等多方面的系统研究,分析脂类风味前体物质变化与风味形成之间的相关性,探索南京板鸭风味形成的机理,为南京板鸭风味研究、风味的调控、传统工艺改进和参数优化提供理论依据。具体研究内容和结果如下:1、南京板鸭生产过程中脂类物质变化的研究分别选择南京板鸭传统工艺过程中的原料、干腌、湿腌、排坯、风干第5天、风干第10天和风干第15天(成品),共7个工艺点,每工艺点随机抽6只板鸭,取股二头肌和皮下脂肪作为样品,用于本研究的各项测定。脂类物质含量的研究显示,加工过程中三酰甘油脂含量变化很小,游离脂肪酸和磷脂的含量显著上升;股二头肌肌内脂肪、皮下脂肪中磷脂含量分别下降41.27%和53.39%,二者的游离脂肪酸与磷脂、甘油酯含量之间R~2分别为0.82/0.42和0.87/0.81,均表明游离脂肪酸增加主要来自于磷脂的水解。建立了一种磷脂组分快速准确的测定方法;通过磷脂组分和磷脂脂肪酸组成的研究表明,高度不饱和性和富含花生四烯酸(20:4)是磷脂显著特点,其中卵磷脂(PC)、脑磷脂(PE)是磷脂的主要组分;磷脂分子中不饱和程度越高的脂肪酸,越容易水解,同时越易氧化分解,其中花生四烯酸水解贡献超过50%,成为南京板鸭独特风味最重要的影响因子。2、南京板鸭原料中肌内主要磷脂组分研究建立了一种鸭肉原料PC和PE主要分子种准确鉴定的方法,采用固相萃取法提取板鸭肌内磷脂,以高效液相色谱法在正相半制备硅胶柱(WatersμPorosil300mmx7.8mmi.d,10gm)上分离制备得到PC和PE,再应用液相色谱-质谱联用技术,在反相柱(symmetry C18,250 mmx4.6 mm i.d,5μm)上分离不同分子种,通过电喷雾电离质谱(ESI-MS)分析鉴定PC和PE的主要分子种组成,其主要脂肪酸组成的结果与气相色谱/质谱(GC/MS)分析结果大致相近。结果显示,肌内磷脂中PC测到10个分子种,其中C18:1/C16:0占54.92%、C20:4/C16:0占7.15%;PE测到11个分子种,其中C18:0/C20:4占50.72%;从微观分子结构的角度,证明了磷脂的高度不饱和性和富含花生四烯酸是其易于分解氧化的内在原因,其中PE多不饱和脂肪酸的比例明显高于PC,对南京板鸭风味形成具有更重要作用。3、南京板鸭生产过程中脂肪酶和磷脂酶的活力变化研究通过板鸭加工过程中各工艺点股二头肌样品中酸性脂肪酶、中性脂肪酶和磷脂酶活力的测定,研究了其变化趋势。结果显示,板鸭在腌制过程中,这三种酶的活力呈逐渐上升的趋势,而在排坯和风干过程中,酶活性逐渐下降,但仍保持一定活力,表明在板鸭加工周期内,脂肪酶类在脂质水解中仍起了比较重要的作用。相关分析表明,板鸭加工过程中,盐含量及水分含量与这三种酶活性之间具有显著的相关性,分别在0.7533-0.9716之间。4、南京板鸭生产过程中脂类物质氧化的研究通过对过氧化值、硫代巴比妥酸(TBARS)值、羰基值和双烯值等氧化指标的测定,研究了南京板鸭加工过程中各工艺点肌内脂质的氧化变化。结果显示,板鸭肌内脂质的过氧化值、TBARS值、羰基值和双烯值在加工过程中均呈逐渐上升的趋势,表明脂质氧化程度逐渐增加。结果还显示,腌制过程对板鸭TBARS值、羰基值和双烯值影响显著,而过氧化值则在风干过程中变化最为显著,表明盐度及水分活度对脂肪氧化进程均有较显著的影响。5、南京板鸭生产过程中挥发性风味成分组成及其变化的研究选择板鸭加工过程中各工艺点股二头肌样品,采用固相微萃取法和GC/MS系统分离和鉴定风味成分。结果显示,在原料、干腌、湿腌、排坯、风干5天、10天和15天的样品中分别检测到33、68、18、31、43、57和54种风味化合物,这些成分可归类为十一类,其中醛类、酮类、醇类、烃类物质含量较高;南京板鸭主成分分析显示,第一主成分主要由2种醛、1种酸和1种醇组成,第二主成分主要由2种醛、1种酮和1种烯等组成,二者总计解释了南京板鸭风味成分变化总方差的85.0%,这些成分大多来自于脂肪的氧化分解产物。更多还原

【Abstract】 Nanjing dry-cured duck is a peculiarly traditional meat product of china, and also one of the most famous dry-cured meat products in the world. Nanjing dry-cured duck, with a long production history and a unique flavor, is enjoying a high reputation in china or southeast Asia. Up to now, the laggard traditional processing technology adopted in small-scale workshops has influenced the sustainable development of dry-cured duck seriously. The main reason is the deficiency in theory research, and the poor understanding on the scientific meaning of the traditional processing technology of dry-cured duck. This lead no theory can be used in optimizing the duration and parameters in practice.The aim of this research is to investigate the forming mechanism and pathways of flavorsubstances originated from lipid by studying the changes of lipid as a main precursor of flavors, the characteristics of endogenesis lipase and analyzing the flavor substances of Nanjing dry-cured duck during the processing; elucidate the role of lipid in formation of flavors; provide a theory basis for studying and accommodating the flavor, improving the processing technology, optimizing the parameters and realizing the industrial production of Nanjing dry-cured duck. The contents and results are as follows:1. Studies on the changes during the processing of Nanjing dry-cured duckExperimental dry-cured duck were processed by traditional processing technology . A tatle of seven points, which were raw duck, end of dry- cured, end of marinated, end of piled, 5 days of air-drying, 10 days of air-drying, 15 days of air-drying （finished product）, were selected during this progress. Biceps femoris and subcutaneous fat were taken from 6 ducks of each point randomly as samples. Then they were used to analyze the changes of contents of lipid, triacylglycerol, phospholipids, free fatty acids and relative indices. Results showed that: triacylglycerol contents in lipid of biceps femoris and subcutaneous fat did not change significantly during processing. While the phospholipids contents in lipid of biceps femoris and subcutaneous fat changed significantly during processing. About 41.27% and 53.39% of the total phospholipids in biceps femoris and subcutaneous fat were hydrolyzed during processing of dry-cured duck. PC and PE were major component of intra-muscle phospholipids of dry-cured duck. The relativity analyze showed that R² of phospholipids and triacylglycerol contents with free fatty acids contents were 0.82/0.42,0.87/0.81,respectively. Results analysis showed that, the main source of free fatty acids was phospholipids. Phospholipids were the main precursor of flavor substances. Analysis of free fatty acids showed that, the proportion of saturated and monounsaturated fatty acids in biceps femoris and subcutaneous fat increased during processing, among which the proportion of monounsaturated fatty acids increased more strongly; the proportion of polyunsaturated fatty acids decreased during processing. These indicated that the polyunsaturated fatty acids were the key fatty acids in lipid oxidation during processing of dry-cured duck. Changes of arachidonic acid contents were gently, which indicate arachidonic acid played an important role in flavor formation of dry-cured duck.2.Research on types of molecular species of phospholipids in raw duck of Nanjing dry-cured duckA method based on high performance liquid chromatography-mass spectrometry （LC-MS） for analysis of the main molecular species of phosphatidylcholine（PC） and phosphatidylethanolamine （PE） in Nanjing salted duck muscle was established. The intramuscular phospholipids was fractionated using solid phase extraction column（NH₂）, then PC and PE was separated from the phospholipid extraction on a normal phase semi-preparative silica gel column（WatersμPorosil 300mm×7.8mmi.d,10μm） by high performance liquid chromatography（HPLC）.The compositions of their molecular species were identified by reverse phase liquid chromatography- electrospray ionization mass spectrometry in positive ion mode using solvent A（methanol/ chloroform, 17.5/1,V/V） and solvent B（acetonitrile/water,1/1,v/v）as mobile phase to linear gradient elution on Symmetry C₁₈ column （250 mm×4.6 mm i.d,5μm）.The results showed that there were five main molecular species in PC from duck muscle, they were:C_20:4/C_16:0 PC,C_18:1/C_16:0 PC, C_18:2/C_18:0 PC,C_18:2/C_16:0 PC and C_18:1/C_18:0 PC.There were also five main molecular species in PE from duck muscle, which were C_14:0/C_22:4PE.3.Study on changes of lipases and phospholipase during processing of Nanjing dry-cured duckThe changes of acid and neutral lipases activity, phospholipase activity in muscle of dry-cured duck during processing were studied. The results showed that the activities of these three enzymes were increased during the process of curing, but decreased during piled and drying. The co-relationship analysis showed that the contents of salt and water were significantly correlated to the activities of these three enzymes during processing of Nanjing dry-cured duck. 4. Study on lipid oxidation of Nanjing dry-cured duck during processingThe lipid oxidation of muscle of breast and leg in dry-cured duck during processing was studied by determination of the peroxide value, TBARS value, carbonyl compounds and conjugated dienes in this paper. The results showed that the levels of lipid oxidation of dry-cured duck became more serious characterized by the increases in the peroxide value, TBARS value, carbonyl compounds and conjugated dienes are increased during processing. The process of salting affected the TBARS value, carbonyl compounds and conjugated dienes significantly and the peroxide value changed evidently during the process of air-drying.5.Study on Time related components and changes in flavor compounds of Nanjing dry-cured duck during processingNanjing dry-cured ducks were processed based on a traditional processing technology. Samples of Biceps femoris were taken from 6 ducks randomly at each of the key stages of production, i. e., raw duck, end of dry- cured, end of marinated, end of piled, 5 days of air-drying, 10 days of air-drying, 15 days of air-drying. Analysis of flavor compounds showed that, there were 33 compounds at green duck, 68 at the end of dry-salting,15 at end of wet-salting,31 at end of arraying, 43 at 5 days of air-drying, 57 at 10 days of air-drying and 54 at 15 days of air-drying. The flavor compounds were clustered in the following chemical families: sulphur compounds, amine compounds, alcohols, carboxylic acids, hydrocarbon compounds, ketones, esters, aldehydes, aethers, nitrogenous compounds and furans. In the flavor substances of the final product of Nanjing dry-cured duck, the contents of aldehydes, alcohols, hydrocarbon compounds and ketones were 37.78 %, 26.93 %, 18.39 % and 11.72 % of all, respectively. The first principal components were consisting of 2 aldehydes, 1 carboxylic acids and 1 alcohols, the second were consisting of 2 aldehydes, 1 ketones and 1 hydrocarbon compounds and some other flavor compounds. The two principal components explained 85.0 % of t he total variance of the flavors in Nanjing dry-cured duck.更多还原