Analysis of the changes of volatile flavor compounds in a traditional Chinese shrimp paste during fermentation based on electronic nose,SPME-GC-MS and HS-GC-IMS

Traditionally fermented shrimp paste has a long fermentation period and is susceptible of external factors,which leads to unstable quality and limits its development and application.Therefore,the purpose of this study is to analyze the flavor changes in the shrimp paste fermentation process and screen out the key volatile aroma components in the shrimp paste to control the flavor quality of the shrimp paste products.The overall odor profile was detected by the electronic nose.A total of 106 volatile flavor compounds in the shrimp paste samples at different fermentation stages were identified by solid-phase microextraction-gas chromatography-mass spectrometry(SPME-GC-MS)and headspace-gas chromatography-ion mobility spectrometry(HS-GC-IMS).The main aroma components alcohols,aldehydes,pyrazines and other substances in the fermentation process showed an overall upward trend.A total of 17 key volatile aroma components in shrimp paste at different fermentation stages were identified by the relative aroma activity value(ROAV)method.The combination of electronic nose,SPME-GC-MS and HS-GC-IMS could comprehensively reflect the changes of volatile components in shrimp paste at different fermentation stages,which helps to further understand the mechanism of shrimp paste flavor formation and provides a basis for the regulation of the flavor quality of shrimp paste products.

Characterization of aroma profiles and aroma-active compounds in high-salt and low-salt shrimp paste by molecular sensory science

Flavor characteristics of raw shrimp,high-salt and low-salt shrimp paste were evaluated and compared by sensory analysis,headspace-gas chromatography-ion mobility spectrometry(HS-GC-IMS)and solid-phase microextraction-gas chromatography-mass spectrometry(SPME-GC-MS).In addition,aroma profiles and aroma-active compounds in these three samples were analyzed by solvent-assisted flavor evaporation-gas chromatography-olfactometry-mass spectrometry(SAFE-GC-O-MS).Results of sensory evaluation revealed that these three samples showed significant differences in sensitivity to the W2W,W2S,W1S and W1W sensors of the electronic nose(p<0.05),which represent organic sulfides,alkane aromatic compounds,short chain alkanes,and sulfides,respectively.Assessment of sensory parameters indicated tha high-salt shrimp paste had a strong roasted and meaty aroma,while low-salt shrimp paste showed an umami aroma more similar to raw shrimp.A total of 118 volatile compounds were identified using the three afore-mentioned gas chromatography methods.Among them,37 aroma-active compounds were detected by GC-O.High-salt shrimp was shown to contain more acids,aldehydes and heterocyclic compounds,which resembled cheese,roasted and meaty aromas.In contrast,low-salt shrimp paste contained more esters,which was similar to the umami aroma profile of raw shrimp.Interestingly,pyrazines were only produced in fermented shrimp paste samples,suggesting that they were produced during the fermentation process and they may contribute unique roasted and meaty aromas,which were important for the overall aroma characteristics of shrimp paste.

Physiochemical Properties, Volatile Compounds and Sensory Evaluation of Chili Sauce Shrimp Paste from Different Regions in Indonesia

Chili sauce shrimp paste (CSSP) is an exotic traditional sauce prepared using mainly fresh chili and shrimp paste well known as sambal terasi (Indonesia) and sambal belacan (Malaysia and Brunei). This study aims to evaluate CSSP from different regions in Indonesia on physiochemical properties, volatile compounds, and sensory evaluation. Evaluation in free amino acid (FAA) and volatile compounds were analyzed using HPLC and GC-MS. CSSP had no significant (p > 0.05) on proximate (except for moisture), salinity, pH, microbial counts and the redness index (a*/b*) compared to control. The identified volatiles can be grouped into hydrocarbon, carbonyl, sulfur, alcohol, nitrogen, fatty acid, and ester compounds. The CSSP A, B, C, D, and E (control) contained 9, 21, 12, 29, and 6 volatile compounds respectively. The total FAA ranged from 44.32 to 67.03 g/100 g, and histidine (his) was found as the most abundant in each CSSP. The rheological properties (yield stress, viscosity, and consistency) of CSSP and control values were significantly, except for CSSP B. The intensities perceived of saltiness, sweetness, and bitterness were greatly varied among CSSP. Although there is no correlation between sweetness and bitterness this is indicated by the negative correlation.

The Flavor and Antioxidant Activity Change Pattern of Shrimp Head Paste During Fermentation

To study the changes of volatile compounds and antioxidant activity of fast fermented shrimp head paste during the fermentation processing,Penaeus vannamei boone head was used as the raw material,and compound starter was added for fermen-tation.During the 14 days of fermentation,the changes of free amino acids,volatile flavor compounds and main components were determined by SPME-GC-MS and electronic nose.The oxidation-resistance changes of water extract at different fermentation stages were evaluated.The results showed that the total free amino acids increased from original 2320 to 5640 mg(100 mL)^(−1).SPME-GC-MS analysis found that aldehydes,pyrazine compounds increased from 10.80%,1.94%to 24.35%,13.63%respectively during the fermentation process.The HO·scavenging ability of shrimp head paste increased from 52%to 86%.Our results showed that the shrimp paste produced from shrimp head fermentation could obtain good flavor and possess certain antioxidant activity of aquatic fermented condiment.

Genotoxic Potential of Shrimp Pastes (Belacan) Extracts Using <i>Umu</i>Test

This study was conducted to observe the genotoxic effects of aqueous, methanol, hexane and dichloromethane extracts of “belacan” (shrimp paste) taken from three local districts in Melaka, Malaysia (Kelemak, Batang Tiga & Pantai Puteri). The umu test which was used as the screening test was conducted with and without the presence of metabolic activation system. Without the presence of metabolic activation system, aqueous extracts from Kelemak showed mutagenicity activity at 5 mg/ml with IR (Induction Rate) = 1.52 ± 0.57 and the methanol extracts showed mutagenic activities at 0.625 mg/ml and 5 mg/ml, which the IR was the highest at 5 mg/ml (2.08 ± 0.09). On the other hand, samples from Batang Tiga, Melaka showed mutagenic effects at all five concentrations for the dichloromethane extract, with IR = 2.09 ± 0.64 as the highest value at 1.25 mg/ml. Methanol extracts also showed positive results at 1.25 mg/ml and 2.5 mg/ml with IR = 1.70 ± 0.33 and IR = 2.12 ± 0.51 respectively, and aqueous extract at 0.625 mg/ml with IR = 1.54 ± 0.48 and 5 mg/ml with IR = 1.74 ± 0.50. There was a significant difference of the mean values of IR between the four different types of “belacan” extracts from Batang Tiga (p < 0.05). All four “belacan” extracts from Pantai Puteri, Melaka did not show any mutagenic effect. With the presence of metabolic activation system, there was no mutagenic effect observed in all four extracts from the three districts. Further study to analyze the contents in the food samples should be done in the future to determine the possible contents in the food samples that might be responsible for the mutagenic activities.

低盐紫苏虾酱制备工艺优化及其挥发性风味物质分析

本研究以东方白虾和紫苏为原料,通过传统制备结合添加曲种协同发酵的方法制备了低盐紫苏虾酱,研究了紫苏添加量、盐添加量、发酵时间和曲种接种量对低盐紫苏虾酱配方的影响。利用Box-Behnken得到的最佳工艺预测方案并基于实际生产条件对预测工艺条件进行修正,结果表明,加曲协同发酵能有效降低盐的添加量,即固定虾的添加量300 g,当紫苏添加量35%、盐添加量10%、曲种接种量3.5%,在32℃发酵时间5 d条件下,制备的低盐紫苏虾酱感官评分达到87.94;挥发性风味物质相对含量占97.82%,其中酯类6种,醇类11种,酸类9种,醛类5种;氨基酸态氮、盐分、蛋白质、水分和灰分等含量均达到SC/T 3602-2016行业标准要求,其中盐分含量为106 mg/100 g,低于GB/T 23789-2009国家标准中对于盐分含量不高于120 mg/100 g的要求,与市场上的产品相比具有低盐、高蛋白的特点。本研究的配方产品属于低盐食品,既保留了虾酱鲜醇适口的特点,又揉入了微辛淡甜的紫苏芳香。

食盐添加量对虾酱理化性质和细菌多样性的影响

为探究食盐添加量对虾酱发酵的影响,分析4种食盐添加量(质量分数为10%、15%、20%、25%)虾酱(分别记为C10、C15、C20、C25)的感官评价、理化指标和细菌群落。结果表明,C15虾酱的气味、滋味和整体接受度评分最高。随着发酵的进行,虾酱中的总挥发性盐基氮(total volatile basic nitrogen,TVB-N)值和氨基酸态氮(amino acid nitrogen,AAN)含量的增长趋势与食盐添加量呈负相关;丙二醛(malondialdehyde,MDA)含量呈波动上升的趋势,发酵结束时,C15虾酱的MDA含量最低;不同虾酱pH值变化不明显,组间无显著差异(P>0.05)。C10和C15虾酱的细菌多样性及丰度显著低于C20和C25虾酱(P<0.05)。C10虾酱中主要优势菌属为四联球菌属和葡萄球菌属;C15虾酱中主要优势菌属为四联球菌属;C0(未发酵虾酱)、C20和C25虾酱以红杆菌科未知属、Planktotalea、潘多拉菌属为优势菌属。利用Kruskal-Wallis秩和检验在5组虾酱中筛选出10种显著差异菌属。Pearson相关性分析表明,C10虾酱中不动杆菌属、枝芽胞杆菌属、unclassified_f_Bacillaceae与TVB-N值呈正相关。C15虾酱中桃色杆菌属与TVB-N值和AAN含量分别呈显著负相关和正相关。C20虾酱中亚硫酸盐杆菌属、红色杆菌属、鲁杰氏菌属、Planktotalea与TVB-N值和MDA含量呈正相关。C25虾酱中亚硫酸盐杆菌属、鲁杰氏菌属、嗜海鞘属、Planktotalea与AAN含量、TVB-N值和MDA含量呈正相关。综上所述,低盐虾酱组(C10和C15)与高盐虾酱组(C20和C25)相比,导致其理化性质差异的关键微生物是不动杆菌属、分枝杆菌属、红色杆菌属、Planktotalea、亚硫酸盐杆菌属和嗜海鞘属。本研究揭示了食盐添加量对虾酱理化性质和细菌群落的影响,可为减盐虾酱的研发和工业化生产提供一定的理论基础。

我国市售虾酱产品品质分析与评价

为了解我国市售虾酱产品的品质现状,探究不同品种虾酱之间的品质差异,采集了32种市售虾酱,进行了感官评价和水分、盐分、蛋白质、氨基酸态氮等理化指标的检测,对品质相关数据进行了统计分析和主成分分析,并进一步采用电子鼻和气相–离子迁移谱(GC-IMS)对气味进行了分析。结果表明,市售虾酱色泽和质地差异相对较小,而气味差异较大。理化指标中,市售虾酱的氨基酸态氮含量变异系数为33.91%,离散程度最大。在主成分分析中,提取到3个主成分,累计方差贡献率达82.32%,表明能够涵盖虾酱品质的基本信息,水分、氨基酸态氮、气味是影响虾酱综合品质的关键指标。电子鼻聚类热图表明,在欧式距离4.03处可将32种虾酱聚为4类,原料是影响聚类的主要因素。对海银虾、蜢子虾和白虾3种原料的虾酱进行GC-IMS分析,共鉴定出63种挥发性成分,主要是醇类。研究结果可为虾酱产品品质评价与生产工艺改进提供参考。

不同香辛料对低盐虾酱中微生物群落和理化性质的影响

为开发新型虾酱产品,扩展虾酱市场,分别将生姜、肉桂和紫苏添加到低盐虾酱中进行发酵。测定添加不同香辛料的低盐虾酱的理化指标,并利用高通量测序技术,探究香辛料的添加对虾酱中微生物多样性和群落组成差异的影响。结果表明,4种虾酱的水分和盐分质量分数范围分别为51.34%~61.77%和15.61%~17.71%。与对照虾酱相比,香辛料添加使虾酱的pH值和氨基酸态氮含量相对较低。肉桂和生姜的添加明显降低了挥发性盐基氮含量,分别降低了30.41%和10.28%,而紫苏的添加使挥发性盐基氮升高了9.98%。与对照虾酱相比,紫苏虾酱的真菌和细菌多样性都高,而肉桂和生姜的添加,使虾酱中细菌群落的丰富度降低,真菌群落的丰富度升高。差异菌群分析表明,生姜和肉桂的添加使虾酱中的四联球菌属、节担菌属的相对丰度较高,而使葡萄球菌属的相对丰度分别降低了99.32%和98.14%。紫苏虾酱中青霉属和曲霉属相对丰度较高。Pearson相关性分析表明,葡萄球菌属、节担菌属、红酵母属和青霉属与理化指标存在显著相关性,说明这些菌属在虾酱中发挥着重要作用。香辛料的添加改变了低盐虾酱中的微生物组成,丰富了虾酱种类,提高了虾酱的安全性。

发酵温度对低盐虾酱中主要风味物质的影响

为探究发酵温度对低盐虾酱中风味物质的影响,分别在10、15、20℃和25℃进行虾酱的自然发酵,分别使用高效液相色谱法、气相色谱法和气相色谱-离子迁移谱测定虾酱中的游离氨基酸、游离脂肪酸和挥发性化合物。结果表明,在低盐虾酱中均检测出17种游离氨基酸和26种游离脂肪酸,10℃发酵的虾酱中呈味氨基酸含量最高,20℃发酵的虾酱中游离脂肪酸含量最高。在低盐虾酱中共鉴定出69种挥发性化合物,包括醇类19种、醛类13种、酮类13种、酯类12种、烯类2种、醚类2种、酸类1种和其他化合物7种。10℃和15℃发酵的虾酱中醇类、酮类的相对含量较高;20℃和25℃发酵的虾酱中氨的相对含量较高。挥发性化合物的主成分分析表明,不同温度发酵的低盐虾酱中挥发性化合物可显著区分。通过正交偏最小二乘判别分析,结合变量投影重要性(variable importance in projection,VIP),共筛选出6种差异挥发性化合物(VIP>1,P<0.05),分别为3-甲基丁醇(单体及二聚体)、乙酸乙酯二聚体、丙烯酸乙酯、2-甲基丁醛二聚体和氨。聚类热图分析表明,10℃和15℃发酵的低盐虾酱风味较相似,20℃和25℃发酵的低盐虾酱风味较相似。该研究结果为推进商品化低盐虾酱的恒温发酵提供了理论参考。

儿茶素对虾滑贮藏和食用品质的影响

为研究儿茶素添加量对虾滑贮藏期间脂肪和蛋白质氧化、微生物侵染程度、色泽以及硬度的影响,以不同时间点样品所含过氧化值(peroxide value,POV)和硫代巴比妥酸(thiobarbituric acid,TBA)值、蛋白质的羰基和巯基含量(质量摩尔浓度)分析儿茶素对虾滑脂肪和蛋白质氧化的抑制作用,以挥发性盐基氮(volatile base nitrogen,TVB-N)值和菌落总数表征微生物对虾滑的侵染程度,以虾滑白度、硬度、pH和感官评分来判断虾滑食用品质的变化。结果显示,儿茶素的添加能够延缓虾滑POV、TBA值、羰基质量摩尔浓度的升高以及巯基质量摩尔浓度的下降,抑制微生物生长繁殖;贮藏期间虾滑的白度值呈先上升后下降的趋势,硬度呈上升趋势,pH无显著变化。结果表明,儿茶素添加量在0.20 g/kg及以上时,能够改善虾滑贮藏期间的品质,具有较好的应用前景。

虾酱中益生菌的筛选及虾肉蛋白发酵饮品的制备与优化

虾肉是营养均衡的高蛋白质食物来源之一,但其嘌呤含量较高,筛选1株嘌呤代谢强的益生菌制成发酵饮品,将减少高嘌呤带来的隐患,同时兼有虾肉的丰富营养及益生菌肠道微生态健康调节功效的优点。该文从虾酱中筛选获得了1株凝结芽孢杆菌,并命名为Bacillus coagulans GH1-1(菌种保藏编号:CGMCC No.24236)。分析显示,该菌株具有较强的抗逆性及肠道存活能力,生长性能良好,培养16 h左右进入稳定期,且嘌呤代谢能力达86.75%。经单因素及正交试验,确定该菌株虾肉发酵饮品最优工艺为:粉碎、无水乙醇脱脂2次、木瓜蛋白酶酶解、活性炭脱腥脱臭后,与柠檬汁进行复配,以3%的接种量,在37℃发酵12 h,再加入1 g/L的甜菊糖苷进行调配,最终得到一款口味酸甜的虾蛋白发酵饮品。该饮品中蛋白质含量达到2.44 g/100 mL,DPPH清除率为80.03%,对黄嘌呤氧化酶的抑制率为66.67%,提示其具有较好的抗氧化及预防高尿酸血症的作用。该研究为虾肉深加工开发提供了一种新的选择,有利于促进虾产业的多元化创新发展。

香辛料对低盐虾酱中生物胺和风味的影响

为了降低低盐虾酱中生物胺含量,开发多品种的新型风味低盐虾酱,分别制备添加生姜、肉桂、丁香、紫苏4种香辛料的低盐虾酱。采用高效液相色谱测定生物胺含量。基于感官定量描述分析和气相色谱-离子迁移谱技术分别评价风味品质和挥发性风味化合物组成。采用主成分分析和偏最小二乘法判别分析,筛选添加不同香辛料的虾酱中的关键差异化合物,并对其进行热图聚类分析。试验数据结果表明:生姜、肉桂和丁香对生物胺形成均有抑制效果,与对照组相比,总生物胺含量分别降低了67.42%,42.47%和3.72%,而紫苏虾酱中色胺和组胺的含量相较于对照虾酱分别高出121.7%和124.1%。GC-IMS共鉴定出61种挥发性化合物。感官定量描述分析、差异谱图和最邻近欧式距离图均表明,添加紫苏和肉桂,对虾酱原有风味影响较小。通过PLS-DA模型共筛选出19种差异挥发性化合物。热图聚类分析显示,丁香虾酱和生姜虾酱的特征挥发性物质中低级饱和醛含量较高,给虾酱带来刺激气味,而肉桂和紫苏赋予虾酱更多清新香气和烘烤香气。肉桂低盐虾酱是一种安全的新型风味低盐虾酱。

虾皮酱加工过程中脂质氧化及抗氧化研究

以总脂、酸价(acid value,AV)、过氧化值(peroxide value,POV)、总胆固醇含量、甘油三酯含量和丙二醛含量为指标,研究虾皮酱加工过程中的脂质变化。进一步,以AV和POV为评价指标,研究迷迭香、乙二胺四乙酸二钠(disodium EDTA,EDTA-2Na)和维生素E(vitamin E,V_(E))抗虾皮酱脂质氧化的效果。结果表明,虾皮酱制备过程中配料的稀释作用显著降低物料的总脂含量、甘油三酯含量、胆固醇含量和酸价(P<0.05);炒制导致物料的甘油三酯含量和过氧化值显著降低(P<0.05),而胆固醇含量、丙二醛含量和酸价显著升高(P<0.05);杀菌导致物料的酸价显著升高(P<0.05),而对过氧化值的影响不显著(P>0.05)。以物料的AV和POV为响应值,各抗氧化剂对响应值影响程度大小为迷迭香>V_(E)>EDTA-2Na。以1 kg物料为基准,最优复配抗氧化剂的配方为迷迭香0.150 g、EDTA-2Na 0.037 g、V_(E) 0.200 g。

酶解法生产虾酱的工艺探究

毛虾具有特殊的营养价值,不但蛋白质丰富,还含有钙、磷等重要矿物元素,素有“钙库”之称。本文以毛虾为原料,利用酶解法这一新的生产工艺,制作味道更鲜美、更易常温储存及运输的虾酱,通过试验优化酶解反应的温度、时间、pH等条件探究酶解法生产虾酱的最优酶解条件。

虾酱源芽孢杆菌的筛选及其益生特性

从市售农家制作传统虾酱中筛选分离5株芽孢杆菌,经鉴定后命名为解淀粉芽孢杆菌Y11、贝莱斯芽孢杆菌Y12、枯草芽孢杆菌Y13、沙福芽孢杆菌Y32和蜡样芽孢杆菌BI6Y。5株菌都可在10%的盐质量分数下正常生长,具有不同产蛋白酶和脂肪酶的能力以及抑菌特性。其中,蜡样芽孢杆菌BI6Y具有β溶血性,对氯霉素、万古霉素、诺氟沙星不敏感,不适合作为益生菌。其它4株芽孢杆菌具有γ溶血性,对氯霉素不敏感,自聚集率在25%~35%之间,可耐受酸和胆盐;分泌表面活性素surfactin;人工胃肠液处理后的存活率多数集中在50%~70%之间,枯草芽孢杆菌Y13在人工胃液(pH 2.0)的存活率最高为95.3%,沙福芽孢杆菌Y32在人工肠液中的存活率最高为85.1%;其菌体、无细胞提取液、细胞内容物分别具有不同的抗氧化活性,其中无细胞提取液可同时清除1,1-二苯基-2-三硝基苯肼(DPPH)和羟自由基,清除率在40%~60%之间。研究结果表明:除蜡样芽孢杆菌BI6Y外,解淀粉芽孢杆菌Y11、贝莱斯芽孢杆菌Y12、枯草芽孢杆菌Y13、沙福芽孢杆菌Y32具有作为益生菌的潜力。研究结果为基于芽孢杆菌的益生菌产品开发提供了一定理论依据。

利用南美白对虾虾头加曲快速发酵制备虾酱的工艺研究

为获得绿色安全、生产周期短、符合大众低盐口味的虾酱,该实验以南美白对虾虾头为主要原料,对加曲虾头酱的快速发酵工艺进行研究。以氨基酸态氮含量和感官评分为指标,通过单因素实验和正交实验确定了加曲发酵虾头酱的最佳工艺,即加盐量10%、发酵温度36℃、加曲量2.5%、发酵时间48 h,此时加曲虾头酱的氨基酸态氮含量达到0.9344 g/100 g,感官评分为82.02分,电子鼻及电子舌表明加曲发酵的虾酱挥发性风味成分有所增加,鲜味、鲜回味增强,咸味降低,品质更优。该研究可为实现虾头高值化利用以及虾酱绿色工业化生产提供理论基础。

基于模糊数学评定与响应面法优化秋葵虾皮辣酱配方

为丰富辣酱类产品,提高秋葵和虾皮的附加值,以秋葵、虾皮、辣椒和豆瓣酱为主要原料,利用模糊数学模型结合响应面法优化秋葵虾皮辣酱的配方。结果表明,秋葵虾皮辣酱的最佳配方为:秋葵干添加量11.0%,虾皮添加量12.0%,干辣椒添加量9.6%,豆瓣酱添加量5.3%,其中干辣椒添加量对秋葵虾皮辣酱的感官评分影响最大,其次是秋葵干添加量和虾皮添加量,最小的是豆瓣酱添加量。此条件下制备的秋葵虾皮辣酱色泽油光鲜亮,香辣浓郁,鲜辣咸甜可口,组织细腻,感官评分为88.17分,与响应面预测值88.79分接近。本研究可为秋葵和虾皮的深度开发及综合利用提供一种新的途径和参考。

响应面法优化南美白对虾即食虾滑的加工工艺

为开发即食虾滑新产品,以南美白对虾为原料,研究不同辅料(金线鱼鱼糜、淀粉、大豆分离蛋白)添加量对虾滑凝胶强度、质构特性、持水性、白度和感官评分的影响。在单因素试验基础上,以感官评分和凝胶强度为响应值,利用响应面法对即食虾滑配方进行优化,结果表明:最适合添加到即食虾滑中的淀粉种类是木薯醋酸酯淀粉,影响即食虾滑产品品质的因素从高到低为金线鱼鱼糜添加量、大豆分离蛋白添加量、木薯醋酸酯淀粉添加量,最终得出即食虾滑的最优配方为:100 g虾仁,虾肉块、虾糜质量比3∶2,添加食盐1%、鸡蛋白粉0.3%、魔芋粉3%、金线鱼鱼糜12.68%、木薯醋酸酯淀粉3.30%、大豆分离蛋白1.14%、谷氨酰胺转胺酶0.3%、虾味剂0.4%、复合磷酸盐0.3%、饮用水8%,该条件下所得即食虾滑的口感爽滑、鲜味十足,感官评分和凝胶强度的综合评价结果最优,分别为90.50分和1 339.87 g·mm,与预测值相近,说明利用响应面法优化南美白对虾即食虾滑加工工艺的方法可靠、可行。

传统虾酱生产技术的研究进展

虾酱是以虾为主要原料,经过研磨、发酵等工艺生产而成的一种传统调味品。该文综述了虾酱的传统生产工艺及现代生产工艺的研究进展,并介绍了虾酱的功能性成分及安全性成分的基本情况及相关研究进展,为虾酱的生产工艺改进以及开展进一步的安全性研究提供理论依据。