Changes in apoptosis factors and activation of caspase-3 in tilapia muscle during storage

The activation of the apoptosis pathway in tilapia muscle during postmortem storage was studied. Changes in caspase-3 activity, ATP content, cytochrome c levels, and ratio of Bcl-2/Bax levels of tilapia muscle were observed during postmortem storage at 20°C. Caspase-3 activity was found to be significantly increased at first, followed by a decrease (P < 0.05); the highest caspase-3 activity was observed at 1 h. The ATP content decreased significantly (P < 0.05), and almost exhausted after 10 h storage. The cytochrome c level in the cytosol showed a significant increase after 5 h of storage (P < 0.05), while the mitochondrial cytochrome c levels showed a decrease. The Bcl-2/Bax ratio was stable from 0–5 h, followed by a rapid decreased at 10–20 h and a significant increased after 20 h (P < 0.05), suggesting that the apoptosis process occurred until 20 h of postmortem storage. Thus, we concluded that the availability of ATP and the increase in cytosolic cytochrome c levels are essential for the activation of caspase-3, and that the former partly limits caspase-3 activity.     

罗非鱼的工厂化育苗与越冬技术实验

详细介绍了利用电厂余热水对罗非鱼进行产卵、孵化、育种的全过程,从而达到提前出苗的目的,对我省罗非鱼的产业化发展必将起到积极的推动作用。     

罗非鱼油的制取工艺及其氧化防止方法

以罗非鱼的鱼内脏为研究对象 ,采用钾盐蒸煮法从罗非鱼内脏中提取鱼油的工艺条件和纯化不饱和脂肪酸 (PUFA)的方法 ,对精制鱼油的氧化性及人工合成抗氧化剂 (TBHQ)、VE、茶多酚 3种抗氧化剂对鱼油的抗氧化性能进行了研究 .通过正交试验及对比试验 ,结果表明 ,从罗非鱼内脏中制取鱼油的最佳工艺条件 :水解温度 70～ 80℃ ,水解时间 4 0min ,KNO3用量 6 g/dL ,盐析时间 10min ;采用低温 钾盐乙醇法纯化鱼油PUFA的效果比尿素包埋法好 ;TBHQ、VE、茶多酚 3种抗氧化剂对鱼油抗氧化作用以茶多酚效果最好     

调味罗非鱼片的HACCP质量管理体系

依据危害分析与关键控制点(HACCP)理论与方法,对调味罗非鱼片生产中的各种危害进行详细的分析,提出了产品加工中实施HACCP计划时原料及各加工工序的危害因素,确立了生产过程的关键控制点,并建立了卫生操作程序、监控方法和纠偏措施以及验证程序,以确保产品达到国家卫生标准。     

罗非鱼骨胶原钙螯合肽的酶解制备

本研究以罗非鱼骨胶原蛋白为原料酶解制备具有良好钙螯能力性的活性肽。以钙螯合活性为指标,将罗非鱼骨架经过脱肉、脱钙等前处理获得的罗非鱼骨胶原蛋白通过木瓜蛋白酶酶解制备得到罗非鱼骨胶原蛋白肽,通过单因素及正交试验对制备罗非鱼骨胶原螯合肽的酶解工艺进行优化。同时对最优条件下酶解获得的罗非鱼骨胶原钙螯合肽的分子量及氨基酸组成进行分析。结果表明,最优酶解工艺条件为:酶解时间4.5 h,pH 6.5,酶解温度62℃,酶底比0.6%。罗非鱼骨胶原钙螯合肽是一类小分子功能活性肽。同时通过对比罗非鱼骨胶原钙螯合肽及其钙-肽螯合物氨基酸组成,发现胱氨酸、天冬氨酸、丝氨酸、谷氨酸、甘氨酸、组氨酸和赖氨酸等氨基酸对活性肽的钙螯合能力起到重要作用。     

罗非鱼蛋白酶解制取鱼露及其抗氧化研究

目的:以罗非鱼为原料,采用生物酶解技术加工传统产品鱼露,提高产品质量,缩短加工时间。方法:采用枯草杆菌碱性蛋白酶(E1)、风味酶(E2)酶解罗非鱼蛋白,制取富含多肽的酶解物;并以酶解物为基本原料制备调味品鱼露。通过对自由基的清除作用,研究其抗氧化作用。结果:采用生物酶解技术生产罗非鱼鱼露,产品色泽好,风味浓,营养高,有良好的抗氧化性。结论:与传统技术生产鱼露比较,生产时间短,工艺条件容易控制,产品质量稳定,该研究为罗非鱼到深加工提供了理论基础。     

利用响应面法优化酶解罗非鱼制备抗氧化肽的研究

采用响应面分析法以·OH清除率和DPPH清除率为研究指标,分析了加酶量、酶解时间、料液比和酶解温度各因素对Protamex蛋白酶酶解罗非鱼制备抗氧化肽的影响,得到了多因素方程来说明各因素之间的相互作用规律,以及多因素对·OH清除率和DPPH清除率的影响,其中料液比对·OH清除率影响最大,酶解时间对DPPH清除率影响最大...     

Oxidative stability of mahi mahi red muscle dipped in tilapia protein hydrolysates

The oxidative stability of mahi mahi red muscle dipped in tilapia protein hydrolysates was evaluated. Alkali solubilised tilapia protein isolate was hydrolysed using Flavourzyme to 13% degree of hydrolysis. Whole tilapia protein hydrolysate and ultrafiltered fraction <10 kDa were used as dip solutions. Mahi mahi red muscle was dip treated either for 2 or 4 min and stored at 4 °C. Lipid hydroperoxides (PV), thiobarbituric acid reactive substances (TBARS) and a∗ value were measured at regular intervals. Results showed that dip treatments significantly decreased (p < 0.05) the formation of PV and TBARS over 90 h storage time. There was no significant (p > 0.05) difference between WH and <10 kDa fractions, and between 2 and 4 min treatments. Red colour of treated samples measured as a∗ value decreased with storage time, but was not significantly different from the control. It could be concluded that dip treatment for 2 min in whole tilapia protein hydrolysate may be used as a potential antioxidant treatment for improving oxidative stability of fish fillets.     

Growth Hormone Secretagogue (A233) Improves Growth and Changes the Tissue Fatty Acid Profile in Juvenile Tilapia (Oreochromis niloticus)

Growth hormone (GH) release is a process that is well regulated by several factors, including GH secretagogues. GH can mediate the regulation of the fatty acid level and composition. The aim of this study was to determine the effect of a synthetic GH secretagogue peptide (A233) on the growth and fatty acid composition in tilapia (Oreochromis niloticus). To address this objective, we administrated a diet supplemented with A233 to juvenile tilapia for 60 days. The group fed with a diet supplemented with 600 μg of A233 per kg of feed increased in weight (4.81 ± 0.09 g) and specific growth rate (2.49 ± 0.03%/day) compared to the control diet group (3.63 ± 0.08 g, 2.07 ± 0.04%/day; respectively) (p < 0.001). In the muscle, the total lipids for the control diet group were higher than that in the group fed with 600 μg of A233 per kg feed; however, no differences were detected in the liver. In both tissues, the patterns of fatty acid composition and content were generally similar, with some exceptions. Tilapia fed with 600 μg of A233 per kg of feed showed, in liver and muscle, a significantly higher composition and content of n‐3 polyunsaturated fatty acids (such as 20:5n‐3, 22:5n‐3, 22:6n‐3) and n‐3/n‐6 PUFA than animals fed with the control diet. To our knowledge, this is the first report on the the effects of natural or synthetic GH secretagogues (GHS) on fatty acid composition, implying an increase in the nutritional quality of the tilapia.     

Replacement of Dietary Fish Oils by Alpha-Linolenic Acid-Rich Oils Lowers Omega 3 Content in Tilapia Flesh

A 20-week feeding trial was conducted to determine whether increasing linolenic acid (18:3n-3) in vegetable oil (VO) based diets would lead to increased tissue deposition of 22:6n-3 in Nile tilapia (Oreochromis niloticus). Five isonitrogenous and isoenergetic diets were supplemented with 3% of either linseed oil (LO), a mixture of linseed oil with refined palm olein oil (PO) (LO–PO 2:1) and a mixture of refined palm olein oil with linseed oil (PO–LO 3:2) or with fish oil (FO) or corn oil (CO) as controls. The PO–LO, LO–PO and LO diets supplied a similar amount of 18:2n-6 (0.5% of diet by dry weight) and 0.5, 0.7 and 1.1% of 18:3n-3, respectively. Increased dietary 18:3n-3 caused commensurate increases in longer-chain n-3 PUFA and decreases in longer-chain n-6 PUFA in the muscle lipids of tilapia. However, the biosynthetic activities of fish fed the LO-based diets were not sufficient to raise the tissue concentrations of 20:5n-3, 22:5n-3 and 22:6n-3 to those of fish fed FO. The study suggests that tilapia (O. niloticus) has a limited capacity to synthesise 20:5n-3 and 22:6n-3 from dietary 18:3n-3. The replacement of FO in the diet of farmed tilapia with vegetable oils could therefore lower tissue concentrations of 20:5n-3 and 22:6n-3, and consequently produce an aquaculture product of lower lipid nutritional value for the consumer.