【作者】 董秀萍；

【导师】 朱蓓薇； 董英；

【作者基本信息】 江苏大学 ， 食品科学， 2010， 博士

【摘要】 海珍品由于营养丰富,需求量不断增大。但是高压、低温、高盐的特殊生存环境,使海珍品具有特殊的组织结构和生理特性。因此,系统研究海珍品的加工特性,建立海珍品质构控制技术,并开发海珍品活性多肽,对丰富海珍品加工理论具有重要意义。本文针对海参、扇贝及牡蛎三种海珍品在加工过程中的特殊性,重点研究海参、扇贝在热加工过程中以及牡蛎在真空冷冻干燥过程中,其组成、组织结构及质构特性的变化；同时,针对原料富含蛋白质的特点,研究海参及牡蛎抗氧化活性肽。主要研究工作如下：(1)为明确热加工过程中海参体壁胶原蛋白结构的变化情况,分别采用紫外光谱和SDS-PAGE分析60-100℃加热过程中酶促溶性胶原蛋白(PSC)的变化。结果表明：随着温度的升高,海参体壁胶原蛋白的三螺旋结构逐渐被打开,导致其在232 nm附近紫外吸收强度逐渐增加；电泳检测α链基本完全降解所需时间逐渐缩短,各加热温度下基本完全降解的时间为60℃-8 h、70℃-6 h、80℃-1.5 h、90℃-0.83 h及100℃-0.33 h。(2)基于胶原分子在固体表面自组装的特性,采用原子力显微镜考察不同因素对海参体壁PSC溶液聚集状态的影响。结果表明：在乙酸缓冲溶液(pH 2.7)、磷酸盐缓冲溶液(PBS,pH 7.2)或超纯水中,随着PSC浓度的增加,聚集程度均逐渐加剧,最终形成堆积结构或片状聚集体。在40-80℃下加热30 min后,PSC在乙酸缓冲溶液中的聚集度增加,温度超过80℃聚集度逐渐下降；80℃加热0.5-2.0 h时,聚集现象比较明显。(3)为了明确海参体壁的热加工特性,采用组织学方法及显微技术考察其结构的变化,并运用质构仪分析嫩度(剪切力)、硬度、弹性、咀嚼性及回复性等指标。结果表明：温度越高海参体壁质量损失率达到平衡所需时间越短,分别为60℃-5.0 h、70℃-3.0 h、80℃-1.5 h、90℃-1.0 h及100℃-0.5 h；温度超过60℃时,海参体壁出现吸水现象,温度越高出现吸水的时间点越早,分别为70℃-24.0 h、80℃-6.0 h、90℃-3.0 h及100℃-2.0 h；采用100℃以上的高温对海参进行加工时,海参体壁的吸水能力明显提高,在相同发制时间(36 h)下,以获得2倍左右质量的水发海参为基准,温度越高,所需时间越短,分别为105℃-35 min、110℃-25 min、115℃-20 mmin和120℃-10 min；加热过程中,海参体壁胶原纤维组织结构会呈现变细、溶胀、凝聚和溶出等变化,温度越高发生聚集所需时间越短,分别为60℃-8.0 h、80℃-1.5 h及100℃-0.5 h；热加工到一定时间和温度后,海参体壁的剪切力和硬度分别降至1000 g和2000 g以下时,回复性明显下降,组织开始变得软烂,无法继续加工,此时参数为70℃-34 h、80℃-20 h、90℃-8 h、100℃-4 h、105℃-2.5 h、110℃-1.5 h及120℃-1 h。(4)依据海参体壁在热加工中胶原蛋白结构变化和质构特性分析,结合感官评定,得到海参体壁热加工控制曲线,建立了海参体壁热加工控制区域。曲线分别为海参体壁失水平衡曲线A、海参体壁吸水起始曲线B、海参体壁高温热加工控制曲线B’,及海参体壁热加工临界曲线C(C’)。加工水发类海参产品时,可以选择介于B和C,或B’和C’曲线之间的加工区域内的适宜加工参数。(5)为明确扇贝柱在热加工中的质构特性,研究了热加工中扇贝柱肌原纤维蛋白的变性情况,并采用光学显微镜观察肌纤维组织结构的变化,并运用质构仪分析嫩度(剪切力)、硬度、弹性、咀嚼性、回复性等指标。结果表明：温度越高,扇贝柱肌原纤维蛋白基本完全变性(变性率≥90%)所需时间越短,分别为60℃-240min、70℃-30 min、80℃-20 min、90℃-7 min及100℃-3 min,此时扇贝柱达到熟化状态；在不同温度下,随着加热时间的延长,扇贝柱肌纤维组织结构均呈现弯曲—舒展—断裂的变化趋势,发生明显断裂的参数为60℃-360 min、70℃-150 min、80℃-90 min、90℃-50 min及100℃-20 min,此时扇贝柱由熟化变为过熟状态。热加工到一定时间和温度后,扇贝柱均会出现组织松散,无法进行加工的情况,此时参数为60℃-390 min、70℃-360 min、80℃-240 min、90℃-90 min及100℃-40 min。(6)依据扇贝柱在热加工中蛋白质变性情况和质构特性分析,结合感官评定,得到扇贝柱热加工控制曲线,建立了扇贝柱热加工控制区域。扇贝柱热加工制品质构控制适宜加工区域为60℃-(4-6)h、70℃-(30～50)min、80℃-(20～90)min、90℃-(7～50)min及100℃-(3～20)min。(7)为确定牡蛎干制和后续复水过程中特性的变化,研究直接冻干牡蛎(Fresh+FD组)和预煮处理后冻干牡蛎(Boiled+FD组)的干燥比、复水比、复水率及组织结构的差异,并与自然干燥牡蛎(Fresh+ND组)进行对比。结果表明：冷冻干燥有利于保持牡蛎原有的组织结构,使其具有更好的复水效果。(8)采用高温处理和酶解相结合的方式制备海参胶原蛋白肽,并考察其抗氧化活性。结果表明：海参体壁明胶和胶原蛋白肽均具有一定的DPPH自由基清除能力(SC50值分别为9.31mg/mL和7.64mg/mL)、羟自由基清除能力(SC50值分别为0.97mg/mL和0.37mg/mL)和脂质过氧化抑制能力(IC50值分别为>20mg/mL和8.56 mg/mL),但胶原蛋白肽的抗氧化能力要明显强于明胶。(9)分别选用木瓜蛋白酶、中性蛋白酶和碱性蛋白酶对牡蛎进行水解,使用超滤膜对牡蛎水解液进行分级,获得具有不同分子质量的牡蛎肽,并考察其抗氧化活性。结果表明：牡蛎肽的抗氧化活性与分子质量分布范围有关,其中分子质量在3 kDa以下的肽组分有较强的抗氧化活性,且碱性肽组分具有更强的清除DPPH自由基的能力。更多还原

【Abstract】 Precious marine products are nutritious, and the demand is increasing in resent years. The high pressure, low temperature and salty living environment result in their unique histological structure and physiological properties. It will be of great significance for enhancing the processing theory of precious seafoods to carry out a systematic research on the processing characteristics of precious seafoods, set up a texture control technique of precious seafoods, and develop bioactive peptides from precious seafoods.In view of the special processing characteristics of sea cucumber, scallop and oyster, we investigated the changes of chemical composition, histological structure as well as texture properties of sea cucumber and scallop during the heating process and of oyster during the vacuum freeze drying process in the present study. Meanwhile, antioxidant peptides were prepared from sea cucumber and oyster due to their abundant protein. The main research contents were summarized as below:(1) To determine the structural changes of collagen from sea cucumber body wall during heating process, pepsin-solubilized collagen (PSC) were purified and the changes were monitored by using ultraviolet (UV) absorption spectra and SDS-PAGE during the heating process ranging from 60℃to 100℃. Results indicated that the triple helical structure of collagen was destroyed by heat, resulting in an increased absorption at 235 nm. The time for complete degradation of a peptide chain of PSC decreased with increasing temperature. It was 8,6,1.5,0.83 and 0.33 h at 60,70,80,90 and 100℃, respectively.(2) Based on the self-assembly characteristics of collagen molecule on solid surface, the effects of different factors on aggregation state of PSC from sea cucumber body wall were investigated by using atomic force microscope (AFM). Results indicated that the aggregation degree of collagen molecule increased gradually with increasing concentration in either acetic acid buffer solution (pH 2.7), phosphate buffer solution (pH 7.2) and ultrapure water, and formed close-packed and sheet-like aggregates finally. After heating for 30 min at 40-80℃, the aggregation degree of PSC increased in acetic acid buffer solution. When the temperature was higher than 80℃, the aggregation degree of PSC decreased. The self-aggregation phenomenon was obvious after heating for 0.5-2.0 h at 80℃.(3) To determine the heat-processing characteristics of sea cucumber body wall, the histological structure was observed by using microhistological techniques, and the shear force, hardness, springness, chewiness and resilience were analyzed by using texture analyser (TA). Results indicated that the higher heating temperature used, the shorter consumption time needed for the mass of sea cucumber body wall reaching a plateau. It was 5.0,3.0,1.5,1.0 and 0.5 h at 60,70,80,90 and 100℃, respectively. When the temperature was higher than 60℃, the sea cucumber body wall began to absorb water. The higher heating temperature used, the shorter consumption time was needed for the appearance of water absorption phenomenon. It was 24,6,3 and 2 h at 70,80,90 and 100℃, respectively. When the sea cucumber was processed at temperature higher than 100℃, the water-absorbing capacity was obviously enhanced. The higher heating temperature used, the shorter time was needed to get the waterishlogged sea cucumber with two-fold mass. It was 35,25,20 and 10 min at 105,110,115 and 120℃, respectively. In the process of heating, the collagen fiber of sea cucumber became thin, swelled, aggregated and dissolved. The higher heating temperature used, the shorter time was needed for the appearance of aggregation phenomenon. It was 8.0,1.5 and 0.5 h at 60,80 and 100℃, respectively. After heating at a certain temperature for a certain period, such as 70℃for 34 h,80℃for 20 h,90℃for 8 h,100℃for 4 h,105℃for 2.5 h,110℃for 1.5 h and 120℃for 1 h, the shearing force and hardness of the sea cucumber body wall fell to less than 1000 g and 2000 g, respectively. When the heating temperature and time were beyond such points, the resilience decreased obviously, and the tissue of sea cucumber became too soft to process.(4) Based on the changes in structure of collagen protein, texture properties and sensory evaluation of sea cucumber body wall, the processing-controlling curves were obtained and the heat processing-controlling area was built up for sea cucumber body wall. The curves included a losing-water-balance curve (A), an absorbing-water-beginning curve (B), a high-temperature processing-controlling curve (B’), and a heat processing-threshold curve (C and C’). When waterishlogged sea cucumber was processed, the processing parameter located in the area between Curve B and Curve C or Curve B’ and Curve C’ should be employed.(5) To determine the heat-processing characteristics of scallop adductor, the denaturation of myofibrillar protein in heating process was investigated. Meanwhile, the changes in muscle fiber structure were studied by using light microscope, and the shear force, hardness, springness, chewiness and resilience were analyzed by using TA. Results indicated that the higher heating temperature used, the shorter consumption time was needed for complete denaturation of myofibrillar protein (denaturation percent≥90%, the adductor muscle become ripen). It was 240,30,20,7 and 3 min at 60,70,80, 90 and 100℃, respectively. The myofibrillar of scallop adductor showed a trend of curving-stretching-breaking change with prolonging heating time at different temperature. When heating temperature was 60,70,80,90 and 100℃, the time for appearance of myofibrillar breakdown was 360,150,70,50 and 20 min, respectively. Under these processing conditions, the adductor muscle became over cooked. When the heating temperature and time were beyond the points such as 60℃for 360 min,70℃for 150 min,80℃for 90 min,90℃for 50 min and 100℃for 20 min, the adductor muscle tissue became too loose to process.(6) Based on the denaturation of protein, texture properties and sensory evaluation of scallop adductor, the heat processing-controlling curves were obtained and the heat processing-controlling areas were built up. When heat-processing scallop adductor was produced, the processing parameters located in the optimum area such as 60℃for 4-6 h,70℃for 30-150 min,80℃for 20-90 min,90℃for 7-50 min and 100℃for 3-20min should be employed.(7) To illustrate the changes in texture properties of oyster in the process of drying and follow-up rehydration, the drying ratio, rehydration ratio, rehydration rate and histological structure of the direct freeze-drying oysters (Fresh+FD group), the pre-cooked freeze-drying oysters (Boiled+FD group) and the natural-drying oysters (Fresh+ND group) were investigated. Results indicated that freeze-drying treatment was favorable to maintain the intrinsic histological structure and better rehydration capacity than the natural-drying treatment.(8) Sea cucumber gelatin peptides were prepared by high-temperature pretreatment followed by enzymatic hydrolysis, and their antioxidant activities were also investigated. Results indicated that both of gelatin and gelatin peptides possessed strong DPPH radical scavenging capacity (SC50 was 0.97 mg/mL and 0.37 mg/mL, respectively), hydroxyl radical scavenging capacity (SC50 was 0.97 mg/mL and 0.37 mg/mL, respectively), and lipid peroxidation inhibitory capacity (IC50 was above 20 mg/mL and 8.56 mg/mL, respectively). Obviously, the antioxidant activity of gelatin peptides was significantly higher than that of gelatin.(9) Oyster meat was hydrolyzed with three proteases including papain, neutrase and alcalase, respectively. The hydrolysates were fractionated using a series of ultrafiltration membranes, and the resultant peptide fractions were evaluated for their antioxidant activity. Results indicated that the antioxidant capacity of oyster peptides was related to the molecular weight distribution and amino acid type, the fractions with molecular mass below 3 kDa showed stronger antioxidant activity. Besides, the alkaline peptides had greater capacity on scavenging DPPH radical.更多还原