【作者】 陈德慰；

【导师】 张慜；

【作者基本信息】 江南大学 ， 食品科学， 2007， 博士

【摘要】 大闸蟹(中华绒螯蟹,Eriocheir sinensis)香气独特,味道鲜美,在我国的饮食文化中有着重要的地位。本论文以阳澄湖大闸蟹为实验原料,针对产业的需求,系统分析了熟制大闸蟹的组成、非挥发性风味成分和挥发性风味成分,研究了高品质冷冻熟制大闸蟹的生产技术。分析了大闸蟹的氨基酸、脂肪酸和矿物质组成,采用氨基酸分值和n-3/n-6等主要指标评价其营养价值:大闸蟹蟹肉中含有18.9%的蛋白质和0.9%的脂肪,蟹肉是个高蛋白、低脂肪的肉类产品。蟹肉的蛋白质含量占了蟹的可食用部分的总蛋白质含量的80%,而蟹膏的脂肪含量占总脂肪的90%以上。大闸蟹是个很好的锌、铁、铜和磷等矿物质元素的来源。在大闸蟹蟹肉蛋白质的氨基酸组成中,含量最高的氨基酸是谷氨酸(151 mg/g),然后是天冬氨酸(99 mg/g),精氨酸(99mg/g),赖氨酸(81 mg/g),亮氨酸(77 mg/g),丙氨酸(69 mg/g)和甘氨酸(64 mg/g),而组氨酸,半胱氨酸,胱氨酸和色氨酸等氨基酸的含量相对较低。在蟹肉中没有限制性氨基酸,必需氨基酸的组成很平衡。蟹肉是个高质量的蛋白质原料。大闸蟹蟹膏中总共鉴定出26种脂肪酸。单不饱和脂肪酸含量最高,约一半(49.81%)都是单不饱和脂肪酸,饱和脂肪酸和多不饱和脂肪酸的含量大致差不多,分别是24.91%和23.87%。其中油酸(18:1)是含量最高的脂肪酸,含量高达30.96%,其次是棕榈油酸(16:1),棕榈酸(16:0)和亚油酸。同时大闸蟹中含一定量的奇数碳链脂肪酸和支链脂肪酸。蟹膏中的n-3和n-6多不饱和脂肪酸分别占总脂肪酸的7.44%和16.43%,n-3/n-6的比值是0.45,n-6/n-3是2.2。大闸蟹是个高n-3多不饱和脂肪酸含量的食品。采用味道强度值(TAV)与味精当量(EUC)方法,确定了大闸蟹蟹肉的主要非挥发性风味成分:大闸蟹蟹肉中的葡萄糖和琥珀酸由于含量低,对蟹肉的味道没有直接的影响。游离氨基酸总含量为20.85 mg/g蟹肉,其中含量最高的三种氨基酸分别是精氨酸(6.64 mg/g),甘氨酸(4.97 mg/g)和丙氨酸(3.69 mg/g);游离精氨酸的TAV值最高,为10.3;甘氨酸和丙氨酸的TAV值分别是3.8和6.2,他们对蟹肉的甜味具有重要的贡献,是蟹肉甜味的主要来源。游离谷氨酸的含量为0.62mg/g,TAV值为2.1,谷氨酸对蟹肉的鲜味具有重要贡献。其他游离氨基酸的含量较低,TAV值也远小于1,可以认为那些氨基酸对蟹肉的味道没有直接的影响。蟹肉中含量最高的呈味核苷酸为AMP,其浓度为75.3 mg/100g;然后是IMP,为34.4mg/100g;而GMP的含量低,为2.3 mg/100g。大闸蟹蟹肉的味精当量为4.2gMSG/100g,每克蟹肉的鲜味强度相当于0.042g味精所产生的鲜味,蟹肉的味精当量的TAV值高达140,从而阐明了蟹肉具有非常强烈的鲜味的原因。采用同时蒸馏萃取提取-气相色谱-质谱(SDE-GC-MS)分析大闸蟹(整蟹和蟹肉)的挥发性成分,共分析出94种化合物,其中整蟹86种,蟹肉83种,两者共有76种化合物。包括C5-9的醛,甲基酮,2,3-丁二酮,1-辛烯-3-醇,氨,吡嗪,噻唑和噻唑啉等化合物。其中整蟹中的挥发性化合物的浓度比蟹肉中的高。采用SDE-GC-MS能够很好的提取,分离和鉴定大闸蟹的挥发性成分。采用风味剖面感官分析方法对新鲜的熟制大闸蟹蟹肉和蟹膏的香气成分进行了分析:蟹肉的气味最主要特征是具有强烈的肉香气味,同时伴随着介于轻微和明确程度的温和的腥味、青和甜,以及非常轻微的泥土、氨和油脂气味,几乎没有烤味、酸味和油脂氧化后产生的哈味。而蟹膏的的气味最主要特征是具有显著的腥味和油脂气味,同时伴随着介于轻微和明确程度青、甜以及泥土的气味,同时具有轻微的肉味,以及非常轻微氨的气味,几乎没有烤味、酸味和油脂氧化后产生的哈味。采用顶空-固相微萃取-气相色谱-质谱(HS-SPME-GC-MS)结合气相色谱-嗅觉测量方法(GC-O)分析蟹肉的主要气味活性化合物组成:在熟制大闸蟹蟹肉中“鱼腥、蟹肉”、“青甜、鸡蛋”和“土豆”三种气味特征的强度比较强,而“硫臭”、“焦甜”和“青”的气味强度特征中等,“肉”、“氨”、“青”、“泥土”和“腥”等气味比较弱;熟制蟹肉中主要风味化合物分别是三甲胺、甲硫醚、3-甲硫基丙醛、1-辛烯-3-酮、二甲基三硫、1-辛烯-3-醇、苯甲醛和2-乙酰基噻唑。研究熟制大闸蟹在冷冻加工和贮藏过程中风味、质构、脂肪酸组成等品质指标的变化规律,通过采用不同的预处理方法(三聚磷酸盐、柠檬酸、抗氧化剂等处理),不同的冷冻方式(缓慢冻结、速冻以及液氮冷冻),获得高品质冷冻熟制大闸蟹的生产技术条件:采用液氮喷淋冷冻方法,大闸蟹蟹肉的肌肉组织产生低温断裂,减少了由于蛋白质变性造成的质构老化变韧现象,因而经冷冻贮藏后,并没有形成纤维感,可以有效的保持其质构特点:采用柠檬酸结合特丁基对苯二酚(TBHQ)处理的样品,可以抑制挥发性盐基氮的形成与增加,抑制脂肪的氧化,更好的保持其感官品质;根据测定的玻璃化温度结果,提出高品质的冷冻熟制大闸蟹的最佳贮藏温度应该保持在-45℃以下贮藏。更多还原

【Abstract】 Chinese mitten crab (Eriocheir sinensis) is a traditional savory food in China with delicious taste and unique pleasant aroma. In this paper, flavor of the crab was analyzed and the freezing technology was obtained.Chinese mitten crab was analyzed for proximate composition, minerals, amino acids and fatty acid composition, and also evaluated for the nutritional quality. The yields of crab meat and edible viscera were 24.2% and 9.2% respectively. The crab meat contained 18.9% crude protein. About 80% of the protein lied in crab meat portion, while about 90% of fat lied in viscera. Chinese mitten crab was an excellent source of minerals, particularly zinc, iron, copper and phosphorous. The crab protein contained high amounts of glutamic acid (151 mg/g), aspartic acid (99 mg/g), arginine (99 mg/g), lysine (81 mg/g) and leucine (77 mg/g); and it was a high quality protein with well-balanced essential amino acid compositions. Twenty six fatty acids were found in crab oil. The monounsaturated fatty acids were dominating with a percentage of 49.81. Oleic acid (18:1) was the dominant fatty acid, followed by palmitoleic acid (16:1), palmitic acid (16:0) and linoleic acid (18:2n-6); and the percentages were 30.96, 14.32, 14.22 and 11.91 respectively. The ratio of n-6/n-3 polyunsaturated fatty acids (PUFAs) values was 2.2; and it’s an n-3 PUFAs rich food in usual diet. In short, the results showed that Chinese mitten crab must be a nutritious food.The non-volatile taste active compounds, including soluble sugars, succinic acid, free amino acids and flavour 5’-nucleotides in the meat of Chinese mitten crab were analyzed, and their taste impacts were evaluated by taste active values (TAVs) and equivalent umami concentration (EUC) methods in this study. The total free amino acid content of crab meat was 20.85 mg/g. Arginine, glycine and alanine were the major free amino acids, accounting for more than 70% of the total free amino acids. 5’-Adenosine monophosphate (AMP) was the main flavour 5’-nucleotide (75.3 mg/100g), followed by 5’-inosine monophosphate (IMP) (34.4 mg/100g) and 5’-guanosine monophosphate (GMP) (2.3 mg/100g). Arginine, glycine, alanine, glutamic acid, IMP and AMP were of high TAV greater than one, and they had strong taste impacts on the crab meat flavour. Glycine and alanine contributed to the major sweet taste, while glutamic acid, IMP and AMP contributed to the strong umami taste. As the TAVs of soluble sugar, succinic acid and bitter free amino acids were lower than one, those compounds are likely to have insignificant impact on the taste of the crab meat. The EUC was 4.2 g MSG/100 g crab meat, which meant that the umami taste of the crab meat was very intense.Volatile compounds in Chinese mitten crab (whole crab and crab meat) were investigated. Samples were extracted by simultaneous distillation-extraction (SDE) and then analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). A total of 94 volatile compounds were identified and quantified in this study. 86 and 83 compounds were found in whole crab and crab meat, respectively. 76 compounds were found in both, including the 5-9 carbons aldehydes, methyl ketones, 2,3-butadione, 1-octen-3-ol, amines, pyrazines, thialdine and thiazoline, etc. In general, the concentrations of volatile compounds in whole crab were considerably greater than in crab meat, and SDE-GC-MS could be used to extract, separate and identify the volatile compounds in this study.The aroma of crabmeat and edible viscera was analyzed by flavor profile analysis methods. The aroma of crabmeat can be described as an intensive meaty, accompanied by mild sweet, green and fishy attribution, and a very little mud, amino and oily attribution, without roast, acid and rancid note; while the aroma of edible viscera can be described as an intensive fishy and oily note, accompanied by mild sweet, green and mud note, and a very little meaty and amino note, without roast, acid and rancid note.The key odor-active compounds were analyzed by HS-SPME-GC-MC combined with GC-O method. In crabmeat, the‘fishy, crabmeat’,‘sweet, green, egg’and‘potato’notes were intensive, and‘sulfur’,‘roast, sweet’and‘green’notes were mild, and‘meaty’,‘amine’,‘green’,‘mud’and‘fishy’notes were insignificant. The key odor-active compounds were trimethylamine, dimethyl sulfide, 3-(methylthio)-propanal, 1-octen-3-one, dimethyl trisulfide, 1-octen-3-ol, benzaldehyde and 2-acetyl-thiazole.The changes of flavor, texture and fatty acid were analyzed in crab during frozen storage. Using different treatment methods (triphosphate, citric acid and TBHQ) and frozen methods (slow frozen, force-aired frozen and liquid nitrogen frozen), the high quality frozen crab technology was obtained: using liquid nitrogen frozen method to maintain texture: Crack was formed in crabmeat, which reduce texture aging during frozen storage. Using citric acid combined with TBHQ treatment to maintain the sensory attribute, the total volatile base nitrogen was reduced and oxidation was depressed. The best storage temperature should below -45℃according to the obtained glass transition temperature.更多还原