仿刺参性腺酶解过程风味变化

Changes in the flavor of Apostichopus japonicus gonads during enzymatic hydrolysis

中文关键词: 海参性腺  水解度  电子鼻  GC-MS  风味

英文关键词: Sea cucumber gonads  Degree of hydrolysis  Electronic nose  GC-MS  Flavor

中文摘要:

      生物酶解是提高水产品蛋白质利用率的有效手段，且酶解过程往往伴随肽类、氨基酸、小分子挥发性成分等的生成或反应，进而引起酶解液风味变化。仿刺参(Apostichopus japonicus)性腺富含蛋白质和多种功效成分，具有良好的开发利用前景。为探究仿刺参性腺酶解过程中蛋白质和风味的变化规律，采用中性蛋白酶对其进行酶解，对酶解过程中可溶性蛋白质、氨基酸态氮、游离氨基酸组成、挥发性成分的变化情况进行了检测分析。结果显示，仿刺参性腺匀浆液中可溶性蛋白质和氨基酸态氮的初始含量分别为1.14和0.15 g/100 g，可溶性蛋白质在酶解前30 min内迅速增加，之后基本保持不变，氨基酸态氮含量在前90 min内随时间延长而逐渐增加，90 min后略有下降，90 min时水解度最大，达43.66%。随着酶解时间的延长，酶解液的鲜味有所增强，腥味减弱，甜味和苦味也略有增强。酶解后游离氨基酸含量显著增加(P<0.05)，其中，呈鲜味的谷氨酸含量最高，其次为呈甜味的甘氨酸和丙氨酸。仿刺参性腺酶解过程气味发生明显变化，烃类种类和相对含量均明显增加，二甲基硫醚含量显著降低，这可能是酶解液腥味减弱的主要原因

英文摘要:

      Apostichopus japonicus is highly edible and economically valuable. However, because of their self-dissolving characteristics, live sea cucumbers must be processed immediately after being caught. This species produces by-products totaling approximately 30% of the specimen, including sea cucumber intestines, gonads, respiratory trees, and other tissues. At present, the processing and utilization degree of these by-products is still very inadequate, and some are directly discarded, resulting in environmental pollution. According to some studies, sea cucumber gonads are rich in high-quality proteins, which can be used to develop dietary supplement products. Sea cucumber gonads also contain sea cucumber polysaccharides, sea cucumber saponins, active lipids, and other active components. The phenols and flavonoids components in the gonads of Atlantic sea cucumbers are high and a potential source of natural antioxidants. Residents in some parts of the Pacific, such as New Zealand and the Cook Islands, regularly collect gonads from sea cucumber viscera for cooking or as a protein source for traditional meals. In Japan, sea cucumber gonads are processed into expensive functional pill and powder products. However, the development and utilization of sea cucumber gonads in China are still very low. Biological enzymatic hydrolysis is an effective way to improve the utilization of proteins in aquatic products. The enzymatic hydrolysis process degrades macromolecular proteins into small peptides, which are easy to dissolve and are conducive to human absorption. At the same time, it is often accompanied by the generation or reaction of peptides, amino acids, and volatile compounds, which in turn causes flavor changes in the enzymatic hydrolysate. The gonads of A. japonicus are rich in protein and functional components, with suitable prospects for development and utilization. To explore changes in protein and flavor during the process of enzymatic hydrolysis, neutral protease was used, and the gonads of A. japonicus were hydrolyzed using the enzymatic hydrolysis conditions established in previous research. Changes in soluble protein and amino acid nitrogen in the enzymatic hydrolysis process were detected and analyzed, and the flavor changes were studied to provide a reference for the development of related products of A. japonicus gonads. The soluble protein content was measured using the Biuret method. The amino acid nitrogen content was measured by the formaldehyde colorimetry method referring to GB/T 5009.39-2003. The hydrolysis degree was determined by Cao´s method, previously established in our laboratory. The composition of free amino acids was analyzed using an automatic amino acid analyzer. The odor characteristics of the enzymatic hydrolysate were analyzed using the PEN3 electronic nose, and the sensory evaluation mechanism was designed to describe the flavor at the same time. The relative contents of volatile components during enzymatic hydrolysis were further analyzed by gas chromatography-mass spectrometry (GC-MS). Results showed that the initial soluble protein and amino acid nitrogen contents in the gonads of A. japonicas were 1.14 g/100 g and 0.15 g/100 g, respectively. The soluble protein content increased rapidly within 30 min and then remained constant. The content of amino acid nitrogen gradually increased in the first 90 min and then decreased slightly. The degree of hydrolysis expressed by the changes in soluble protein and amino acid nitrogen during enzymatic hydrolysis reached a maximum at 90 min, up to 43.66%. With the extension of enzymatic hydrolysis time, the umami of enzymatic hydrolysis was enhanced, the fishy smell was weakened, and the sweet and bitter tastes were slightly enhanced. The fresh flavor and sweet taste of enzymatic hydrolysis were also enhanced, consistent with the high glutamate, glycine, and alanine content in free amino acids with the extension of enzymatic hydrolysis time. At the same time, the free amino acid content increased significantly after enzymatic hydrolysis (P<0.05). With the extension of the enzymatic hydrolysis time, the content of free amino acids increased gradually. Glutamic acid is a typical fresh amino acid. TAV(taste activity values) increased from 5.41 to 14.24 at 120 min of enzymatic hydrolysis, significantly contributing to the flavor of the enzymatic hydrolysate. The glutamate content was the highest, followed by glycine and alanine, which also influenced flavor. Moreover, the odor changed significantly during enzymatic hydrolysis. The results of the electronic nose analysis showed that the odor changed significantly after the enzymatic hydrolysis of the gonads of A. japonicus. Through further GC-MS analysis, it was found that the content of fishy substances represented by dimethyl sulfide decreased significantly after enzymatic hydrolysis, and the production of some hydrocarbons, alcohols, and aldehydes gave the enzymatic hydrolysis solution a pleasant smell. The types and relative content of hydrocarbons increased significantly, and the content of dimethyl sulfide decreased significantly, likely responsible for the weak fishy odor of the enzymatic hydrolysate. In this study, the changes in soluble protein and amino acid nitrogen during enzymatic hydrolysis were detected and analyzed, and the flavor changes were studied, providing a reference for the development of gonadal-related products of A. japonicus.