盐度、碱度对尼罗罗非鱼生长和肌肉品质的影响

在水温(24±1)℃下,将初始体质量(50.00±4.12)g的尼罗罗非鱼放入150 cm×60 cm×40 cm循环可控水族缸内,每箱15尾,每组设置3个平行。将尼罗罗非鱼在盐度(12 g/L)、碱度(23.8 mmol/L NaHCO3)、盐碱(12 g/L和23.8 mmol/L NaHCO3)以及淡水(对照组)水体中分别饲养56 d,比较和测量各组鱼体生长性能指标、肌肉常规营养成分、结合氨基酸和游离氨基酸含量,研究盐度、碱度对罗非鱼生长性能和肌肉品质的影响。试验结果显示,与淡水组相比,改变水体盐度、碱度对鱼体质量增加率、特定生长率和饲料系数均无显著影响(P>0.05)。盐碱组鱼肌肉灰分含量升高,粗蛋白含量下降;粗蛋白含量显著低于其他组(P<0.05);各组水分和粗脂肪含量差异不显著(P>0.05)。各组必需氨基酸量与氨基酸总量比值和必需氨基酸与非必需氨基酸比值分别为40%~41%和66%~69%,各组间差异不显著(P>0.05);处理组中必需氨基酸指数为47.06~59.66,盐碱组>碱度组>盐度组,盐碱组显著高于盐度组和碱度组(P<0.05)。碱度组、盐碱组和盐度组鲜味氨基酸总量分别为淡水组的1.78倍、1.74倍和1.63倍,且碱度组和盐碱组显著高于盐度组(P<0.05);盐碱组甜味氨基酸和游离氨基酸总量显著高于盐度和碱度组(P<0.05)。水体盐度、碱度均可有效改善罗非鱼肌肉营养价值和呈味特征,而碱度对肌肉呈味的影响效果更加明显。

Effects of Salinity and Alkalinity on Growth Performance and Muscle Quality of Nile Tilapia Oreochromis niloticus

Nile tilapia(Oreochromis niloticus)with initial body weight of(50.00±4.12)g were reared in a recirculating aquarium of 150 cm×60 cm×40 cm at a stocking density of 15 individuals per aquarium in salinity(SW,12 g/L),alkalinity(AW,23.8 mmol/L,NaHCO3),salinity-alkalinity(SAW,12 g/L,23.8 mmol/L,NaHCO3)and fresh water(FW as a control)for 56 days with triplication to evaluate the effects of salinity and alkalinity on growth performance and muscle nutrition and flavor quality of Nile tilapia.No significant differences in body weight gain(WG),specific growth rate(SGR)and feed conversion ratio(FCR)were found in the fish in the treated groups compared to the FW group.The tilapia in SAW group had higher muscular ash content and significantly lower muscular crude protein content than the fish in other groups did(P<0.05),without significant difference in muscle moisture and crude fat content among the three groups(P>0.05).The ratio of essential amino acid to total amino acid was varied from 40%to 41%and the ratio of essential amino acid to non-essential amino acid from 66%to 69%,without significant difference among the three groups(P>0.05).The essential amino acid index was found to be ranged from 47.06 to 59.66,significantly lower in the FW group than that in the other groups(P<0.05),significantly higher in the SAW group than those in the SW group and the AW group(P<0.05).The total contents of flavor amino acids in AW group,SAW group,and SW group were 1.78 times,1.74 times and 1.63 times in FW group,respectively,significantly higher in AW group and SAW group than that in SW group;the total contents of flavor amino acids and free amino acids in SAW group were significantly higher than those in SW and AW groups.The findings indicated that increasing salinity and alkalinity resulted in improvement of the muscular nutrient value and flavor characteristics of Nile tilapia,especially alkalinity.