某蛋白质粉的营养价值评价

目的了解某蛋白质粉的蛋白质营养价值。方法采用化学和生物学方法测定和分析某蛋白质粉的营养价值,并与酪蛋白进行比较。根据国标测定蛋白质粉的化学成分。单笼饲养50～70g的SPF级初断乳Wistar大鼠36只,适应环境后根据体重随机分为3组,分别为无氮组以及含蛋白质10.4%的酪蛋白组和含蛋白质10.5%的蛋白质粉组。按照AOAC（美国官方分析化学师协会）标准给予饲料,根据食物摄入量、体重增加量和饲料中的蛋白质含量计算出蛋白质功效比值（PER）。使用代谢笼,单笼饲养180 g左右的SPF级幼年Wistar大鼠12只,分为无氮组和蛋白质粉组,每天收集每只大鼠的粪便和尿液,测定其中的蛋白质含量,计算出表观消化率（AD）和真消化率（TD）。结果化学方法得出受试蛋白质粉的必需氨基酸（EAA）占其氨基酸总量的41.74%,EAA组成与FAO/WHO模式接近,支链氨基酸（BCAA）含量约占氨基酸总量的20%,蛋白质的氨基酸评分（AAS）、化学评分（CS）为69.1、59.8。生物学方法得出受试蛋白质粉的PER为2.22,蛋白质粉组大鼠的食物利用率（32.93%）与酪蛋白组（33.01%）比较,差异无统计学意义（P〉0.05）。受试蛋白质粉的AD和TD分别为93.90%和94.27%,生物价（BV）为90.45,蛋白质净利用率（NPU）为85.34%。结论受试蛋白质粉的EAA和BCAA含量较高,生长价值与酪蛋白类似,受试蛋白质粉的氨基酸评分、消化率、生物价、蛋白质净利用率等评价指标均高于大豆蛋白,与鱼肉、牛肉等动物性食品的蛋白质营养价值接近,说明受试蛋白质粉的蛋白质营养价值高,是良好的蛋白质来源。

Nutritional evaluation of protein powder

Objective To evaluate the nutritional value of protein powder. Methods The nutri- tional evaluation of protein powder was assayed by chemical analysis and animal experiments, and com- pared with casein. 36 SPF weanling Wistar rats （ body weight （BW） , 50 - 70 g） were fed in separate ca- ges. After adaptation to the environment, they were divided into 3 groups randomly by BW, i. e. , nitrogen- free （N-free） diet group, casein diet group containing 10.4% protein, and protein power diet group con- taining 10.5% protein. They were fed according to the standard of AOAC. The protein efficiency ratio （PER） was calculated, by considering the food intake, BW gain, and feed protein content. 12 SPF infan- cy Wistar rats weighing about 180 g were fed in separate metabolism cages, and they were divided into 2 groups, i. e. , N-free diet group and protein powder diet group. The excrement and urine of every rat were gathered everyday. The protein content was measured, and then the apparent digestibility （AD） and true digestibility （TD） were calculated, Results The amino acid analysis showed that the total essential amino acid in protein powder was high in corresponding with the evaluation model of FAO/WHO, making up of 41.74% of the total amino acids contents. The amino acid score （AAS） and chemical score （CS） of its protein were 69.1 and 59.8 respectively. The rat metabolism and growth experiments showed that the ap- parent digestibility （ AD ）, true digestibility （ TD ）, and net protein utilization （ NPU ） of protein powder were 93.90% ,94.27%, and 85.34%, respectively. Protein efficiency ratio （PER） and biological value （BV） were 2.22 and 90.45. There was no significant difference in these indices between protein powder group and casein group. Conclusion The tested protein powder contains high EAA and BCAA , and its growth value is similar with casein. The AAS, TD, BV, NPU of the tested protein powder were higher than soybean protein, and its nutritional value is close to animal proteins of beef, fish, et al. The results suggested that protein powder had high nutrition value and was a good protein resource.