半咸水和淡水养殖模式下刀鲚肌肉的营养成分

Muscle nutrient composition of Coilia nasus in brackish water and fresh water cultured modes

为了探究半咸水和淡水养殖模式对刀鲚营养积累的影响,采用生化实验的方法分析并比较了半咸水(盐度10~15)和淡水(盐度0.4~1.0)池塘生态养殖模式下刀鲚肌肉的营养成分。结果显示,半咸水组刀鲚肌肉的粗脂肪含量(7.27%)显著高于淡水组(4.30%);半咸水组的刀鲚肌肉的水分含量和灰分含量(72.54%和1.32%)均显著低于淡水组(76.85%和2.06%),二者的粗蛋白含量无显著差异。除了色氨酸和胱氨酸在两种模式间没有显著差异外,其余16种氨基酸在半咸水组中的含量均显著低于淡水组。半咸水组的刀鲚肌肉的TAA、EAA、HEAA、NEAA和DAA均低于淡水组,而EAA/TAA和EAA/NEAA在两种模式之间无显著变化,半咸水组的鲜味氨基酸和氨基酸总量比率(DAA/TAA)(40.32)显著低于淡水组(40.68)。半咸水组的刀鲚必需氨基酸指数(EAAI)(58.59)低于淡水组(72.04),而F值(2.44)高于淡水组(2.35)。在检出的28种脂肪酸中,有11种脂肪酸的含量在两种模式之间有显著差异。在主要的脂肪酸中,半咸水组刀鲚的C16:0、C18:0、C18:1n9c、C22:5n3(DPA)和C22:6n3(DHA)的含量显著高于淡水组,而C18:2n6c和C18:3n3的含量显著低于淡水组。半咸水组的SFA、MUFA和EPA+DHA含量均显著高于淡水组,∑n3PUFA/∑n6PUFA(3.93)显著高于淡水组(2.10)。研究表明,淡水养殖模式刀鲚肌肉蛋白质更有营养价值、味道更为鲜美,但半咸水养殖模式有利于刀鲚体内脂肪的积累以及MUFA(特别是C18:1n9c)的蓄积,半咸水环境的渗透压可能处于刀鲚体内的等渗点附近,这更有利于体内营养物质的积累和鱼体的生长。建议刀鲚养成阶段采用半咸水,销售前强化养殖阶段采用淡水。本实验为探究不同盐度养殖模式下刀鲚体内营养储存特征提供了科学依据。

In order to understand the effect of brackish water and fresh water culture modes on the nutrient accu-mulation of Coilia nasus cultured in pond,the muscle nutritional composition and quality of Coilia nasus ecologic-ally cultured in brackish water(salinity 10-15)and freshwater(0.4-1.0)model were investigated and analyzed by biochemical analysis methods.The results show that the muscle crude fat content(7.27%)of C.nasus cultured in brackish water mode was significantly higher than that of freshwater mode(4.30%),while the muscle moisture(72.54%)and crude ash content(1.32%)of brackish water mode were significantly lower than that of freshwater mode(76.85%and 2.06%,respectively),No significant difference in the crude protein content of muscle was found between two cultural modes.Except that no significant difference in tryptophan and cystine was found between the two cultural modes,the contents of other 16 amino acids of brackish water mode were significantly lower than those of fresh water mode;the total amino acid(TAA),total essential amino acid(EAA),total half-essential amino acid(HEAA),total non-essential amino acid(NEAA),and total delicious amino acid(DAA)con-tents of brackish water mode were significantly lower than those of fresh water mode,and there was no significant difference in the EAA/TAA and EAA/NEAA specific values of C.nasus muscle between two cultural modes,while the DAA/TAA specific value(40.32)of brackish water mode were significantly lower than that of fresh water mode(40.68).The essential amino acid index(EAAI)(58.59)of brackish water mode was lower than that of fresh water model(72.04),while the specific value of branched amino acids to aromatic amino acids(F value)(2.44)of brackish water mode was higher than that of fresh water mode(2.35).In the 28 kinds of fatty acids detec-ted,there was no significant difference in the contents of 11 kinds of fatty acid between two cultural modes.In major fatty acids,C16:0,C18:0,C18:1n9c,C22:5n3(DPA)and C22:6n3(DHA)contents of brackish water group were significantly higher than that of fresh water group,while the C18:2n6c and C18:3n3 contents of brackish water mode were significantly lower than those of fresh water mode.SFA,MUFA and EPA+DHA contents of brackish water mode were significantly higher than those of fresh water mode;∑n3PUFA/∑n6PUFA(3.93)of brackish water mode was significantly higher than that of fresh water model(2.10),this is consistent with the fact that n3PUFA/n6PUFAs of migratory fish muscle is higher in seawater and lower in freshwater.Therefore,the muscle protein of C.nasus cultured in fresh water is more nutritious and delicious,while brackish water culture is beneficial to the accumulation of fat and the retention of the MUFA(especially C18:1n9c)in C.nasus.The osmotic pressure of brackish water may be near the isotonic point of C.nasus,and this is more conducive to the accumulation of nutrients and the growth of C.nasus.It is suggested that brackish water should be used in the commercial fish culture stage of C.nasus and fresh water should be used in the intensive culture stage of C.nasus before the sales.