乳酸菌对腌干鱼制品脂质氧化抑制机理研究

Salted dried fish is a well-accepted traditional food in China. It is rich in unsaturated long-chain fatty acids that are highly susceptible to oxidation during processing. Lipid hyperoxidation is therefore one of the primary causes of quality deterioration in salted dried fish, such as negatively affects on sensory quality and nutritional content of the fish product, and even generates toxicants which could bring about health threats to consumers. Thus, safety and effective inhibitory measures should be taken. Lactic acid bacteria(LAB) are identified as Generally Recognized as Safe Foods(GRAS), with antioxidant function, but its mechanism of inhibitory effect on lipid oxidation is unclear. Therefore, this research intends to screen the LAB by metagenomics from fatty salted fish during processing which could inhibit lipid oxidation. The regularity of lipid oxidation during processing is studied using lipidomics, then LAB has been inoculated to fatty fish. The influences of LAB on lipid oxidation including inhibition of oxidation products and key enzyme; its impact on target lipids are also assessed. Moreover, combined with the content and structure of expolysaccharides(EPS) and activity changes of antioxidant enzymes(SOD, GSH-Px and Cat enzymes), the mechanism of inhibitory effect of LAB on lipid oxidation of salted dried fish is clarified. Therefore, the study will provide a basic theory for producing salted fish with safety and high quality, as well as promote the development of salted dried fish processing industry in our country, which is of important significance.

腌干鱼是深受欢迎的传统食品，因富含长链多不饱和脂肪酸，加工过程脂质容易氧化过度，导致感官劣变、营养损失、产生毒性化合物而导致安全问题，需要采取安全有效的措施加以抑制。乳酸菌被认为是公认安全食品（GRAS），具有抗氧化性，但其抑制食品脂质氧化的机理尚不明确。因此，本研究拟运用宏基因组学等技术筛选具有抗氧化活性的乳酸菌，利用脂质组学等技术先分析多脂海水鱼在腌干加工过程中的脂质氧化规律，再将菌株接种至腌干鱼加工过程中，研究菌株抑制脂质氧化产物生成、关键酶活力的能力以及抑制作用靶向脂质，并结合胞外多糖含量、结构及抗氧化酶活力变化，阐明其抑制机理。本研究为生产安全优质腌干鱼提供基础理论和技术，对促进我国腌干鱼加工业的发展，具有重要的意义。

本项目研究乳酸菌对传统水产制品腌干鱼加工中脂肪氧化的抑制机理，解决由此导致的安全问题。以渔获量较高的红肉鱼蓝圆鰺和白肉鱼带鱼这两种高脂鱼为对象，首先从氧化指标、脂肪酸及极性脂质（PL）和甘油三酯（TAG）等研究两种鱼腌干加工中的脂质氧化规律，主要采用气相色谱-质谱联用（GC-MS）及电喷雾三重四极杆质谱仪（ESI-MS/MS）。接着运用宏基因组MiSeq测序结合传统方法从腌干鱼中筛选出3种安全、有效、天然的抗氧化剂——乳酸菌，再从抗氧化酶及胞外多糖研究抑制脂质氧化的机理，最后接种到腌干鱼中，探讨其对产品脂质的影响。结果：腌干加工中带鱼的初、次级氧化程度都比蓝圆鲹强，干燥为关键阶段。加工对蓝圆鰺脂肪酸的影响要略高于带鱼，分别有7种及5种脂肪酸皆在干燥阶段变化极显著。两种鱼的多种PL的含量在加工中的变化相反，变化极其显著（p < 0.001）的PL，蓝圆鰺比带鱼多；大部分甘油磷脂含量的显著变化出现在腌制，而溶血磷脂则全部从干燥开始发生显著性增加（p < 0.05）。原料中的TAG总含量，蓝圆鰺远高于带鱼，4种含量较高的TAG在两种鱼中一致，且组成差别不大，但加工中蓝圆鲹的TAG含量出现显著性减少（p < 0.05），带鱼则相反。与脂质氧化显著相关（p < 0.05或p < 0.01）为多种含EPA/DHA的脂质。测序获得341355条序列，带鱼的细菌多样性略高于蓝圆鲹，多样性在加工中均呈现下降，蓝圆鲹的优势菌是弧菌科和葡萄球菌科，而带鱼的优势菌则另含链球菌科。筛选了抗氧化活性较高的乳酸菌PP、LP和L21，经16SrDNA鉴定为戊糖片球菌、植物乳杆菌和干酪乳杆菌。干酪乳杆菌（L21）抗氧化能力最强，其胞外多糖（EPS）含量最高，且由甘露糖、鼠李糖、葡萄糖和半乳糖等4种单糖组成；接种3种乳酸菌至腌干鱼中进行发酵，与未接种样品对比，主要脂肪酸的百分含量差异并不显著（p > 0.05）。乳酸菌对带鱼几乎所有PL含量的影响皆比蓝圆鰺显著；乳酸菌对蓝圆鲹中的TAG的影响远小于带鱼。本研究为生产安全优质腌干鱼提供基础理论和技术，对促进我国腌干鱼加工业的发展，具有重要的意义。