The proteolytic activity of the crude enzyme extracts of Baltic cod (Gadus morhua) alimentary tract

The crude enzyme extract from Baltic cod alimentary tract had maximum activity of aspartic proteinases towards haemoglobin at pH 2.0 and 3.4, and of serine proteinases with casein as the substrate at pH 8.3 and 10.4. With bovine myofibrils as the substrate the proteolysis at pH 5.0-8.0 was maximum at the lowest and highest pH values. the optimum temperature for the proteolytic activity at pH 3.4 and 10.4 was 30–45°C and at pH 8.3 it was 40–50°C. Heating the crude extract for 10 min at pH 3.4,8.3, and 10.4 in the absence of the substrate had no effect on the activity of the acid and alkaline proteinases up to about 35–40°C. the stability at higher temperature decreased gradually and total inactivation occurred at 55–60°C. In the pH range 5.5–7.5 the proteolytic activity against bovine myofibrils was low at 0°C but brought about significant loss of myosin heavy chain at 20°C.     

Use of bacterial extracts to enhance amino acid breakdown in dry fermented sausages

The effect of the intracellular cell-free extracts (ICFEs) of two bacterial strains (Lactobacillus sakei GO and Bacillus pumilus) on the amino acid catabolism and the sensory properties of dry fermented sausages, was investigated. Extracts were added to sausages alone or in combination with a protease, papain. Amino acid breakdown was monitored by the changes in free amino acids, ammonia and amine content during the ripening process. A 15% decrease in the content of free amino acids was observed in sausages added with the ICFE from L. sakei GO. Furthermore, the extract of L. sakei GO significantly reduced (54-68%) the content of the amino acids considered as precursors of the typical ripened flavour, i.e., valine, leucine and isoleucine. Chemical changes were not reflected in a significant improvement of the sensory quality of sausages added with the ICFEs. The potential use of the bacterial ICFEs studied in the present work for the manufacture of dry fermented sausages, and its comparison with the use of fungal extracts, are discussed.     

Assessment of intestinal amino acid availability in cattle by use of the precision-fed cecectomized rooster assay

The digestibilities of amino acids in duodenal digesta of steers were measured using a precision-fed cecectomized rooster assay. Freeze-dried duodenal digesta from steers fed five different diets were utilized. Amino acids present in digesta of steers fed diets supplemented with corn gluten meal were more digestible than those from digesta of steers fed diets supplemented with soybean meal, blood meal, fish meal, or no true protein source. Measurements of amino acid digestibility in the cecectomized rooster were similar to those obtained previously when measured with reference to chromic oxide in steers fitted with duodenal and ileal cannulae, suggesting that the precision-fed cecectomized rooster assay is an appropriate technique for estimating small intestinal digestibility of amino acids in cattle.     

Antioxidant activity of extracts produced by solvent extraction of almond shells acid hydrolysates

The ethyl acetate-soluble fraction generated during acid hydrolysis of almond shells was evaluated for radical-scavenging capacity and protection against fish oil oxidation. The influence of the operational conditions during acid hydrolysis on: (i) the total phenolics produced; (ii) the recovery yield of ethyl acetate solubles; (iii) the phenolic content in the ethyl acetate extracts; (iv) the antioxidant activity of extracts was assessed. A one-at-a-time variation study of the hydrolysis time and sulfuric acid concentration was carried out. For a given temperature and hydrolysis time, the influence of the acid concentration was noticeable; whereas the maximal phenolics production, measured in the hydrolyzate (2.2 g gallic acid equivalents/100 g shells) was achieved with 2% sulfuric acid, the maximal recovery in the organic phase required at least 5% acid. The crude extracts showed DPPH radical-scavenging activities (EC₅₀ < 0.5 g/l) comparable to those of synthetic antioxidants, and protected labile lipid systems, such as fish oils and fish oil-in water emulsions, from oxidation as efficiently as did propyl gallate.     

全自动氨基酸分析仪测定支链氨基酸粉中牛磺酸的含量

目的建立全自动氨基酸分析仪测定支链氨基酸粉中牛磺酸。方法样品经上样缓冲液(pH 2.2)溶解提取,按照氨基酸分析仪设定的钠体系程序洗脱,用Na型离子交换色谱柱分离,与茚三酮反应液在135℃下反应,生成可在570 nm和440 nm检测到的蓝色物质,采用外标法定量。结果牛磺酸在4.1065~20.5326μg/mL浓度范围内有良好的线性,r~2=0.999,回收率为101.28%,RSD为2.1%,检出限为15 mg/100 g。结论该方法准确可靠,不需要剧毒衍生试剂,适用于支链氨基酸粉中牛磺酸的测定。     

Substitution of fish silage protein and a free amino acid mixture for fish meal protein in a chicken diet

White Leghorn chickens were fed a basal diet with about 550 g kg^?1 of the protein from fish meal. Graded amounts of fish silage protein or an amino acid mixture simulating fish meal protein were substituted for parts of the dietary fish meal protein. In two experiments 150 and 300 g kg^?1 of fish meal protein were replaced by fish silage protein or by an amino acid mixture simulating fish meal. In one experiment graded amounts of 0, 50, 100, 200, 300 and 400 g kg^?1 of fish meal protein were replaced by fish silage protein. Growth and feed efficiency were the same or better when some of the protein was from fish silage. The results showed that replacement of dietary fish meal with fish silage did not reduce the dietary quality of the feed for young growing chickens. It is concluded that it might be advantageous to substitute fish silage for some of the fish meal under the experimental conditions used.     

Isolation and antioxidative activity of amino acid derivatives produced by Leuconostoc mesenteroides

Food Science and Biotechnology - One new phenyl lactic acid derivative, N-(5-amino-2-hydroxy-1-oxopentyl)-tyrosine (2), and three known metabolites [(S)-8-hydroxy-4-hydroxy-phenylpropanoic acid...     

Effects of graded removal of lysine from an intravenously infused amino acid mixture on lactation performance and mammary amino acid metabolism in lactating goats

To investigate responses of milk protein synthesis and mammary AA metabolism to a graded decrease of postruminal Lys supply, 4 lactating goats fitted with jugular vein, mammary vein, and carotid artery catheters and transonic blood flow detectors on the external pudic artery were used in a 4 × 4 Latin square experiment. Goats were fasted for 24 h and then received a 9-h intravenous infusion of an AA mixture plus glucose. Milk yield was recorded and samples were taken in h 2 to 8 of the infusion period; a mammary biopsy was performed in the last hour. Treatments were graded decrease of lysine content in the infusate to 100 (complete), 60, 30, or 0% as in casein. Lysine-removed infusions linearly decreased milk yield, tended to decrease lactose yield, and tended to increase milk fat to protein ratio. Milk protein content and yield were linearly decreased by graded Lys deficiency. Mammary Lys uptake was concomitantly decreased, but linear regression analysis found no significant relationship between mammary Lys uptake and milk protein yield. Treatments had no effects on phosphorylation levels of the downstream proteins measured in the mammalian target or rapamycin pathway except for a tended quadratic effect on that of eukaryotic initiation factor 2, which was increased and then decreased by graded Lys deficiency. Removal of Lys from the infusate linearly increased circulating glucagon and glucose. Removal of Lys from the infusate linearly decreased arterial and venous concentrations of Lys. Treatments also had a significant quadratic effect on venous Lys, suggesting mechanisms to stabilize circulating Lys at a certain range. The 2 infusions partially removing Lys resulted in a similar 20% decrease, whereas the 0% Lys infusion resulted in an abrupt 70% decrease in mammary Lys uptake compared with that of the full-AA mixture infusion. Consistent with the abrupt decrease, mammary Lys uptake-to-output ratio decreased from 2.2 to 0.92, suggesting catabolism of Lys in the mammary gland could be completely prevented when the animal faced severe Lys deficiency. Mammary blood flow was linearly increased, consistent with the linearly increased circulating nitric oxide by graded Lys deficiency, indicating mechanisms to ensure the priority of the mammary gland in acquiring AA for milk protein synthesis. Infusions with Lys removed increased mammary clearance rate of Lys numerically by 2 to 3 fold. In conclusion, the decreased milk protein yield by graded Lys deficiency was mainly a result of the varied physiological status, as indicated by the elevated circulating glucagon and glucose, rather than a result of the decreased mammary Lys uptake or depressed signals in the mTOR pathway. Mechanisms of Lys deficiency to promote glucagon secretion and mammary blood flow and glucagon to depress milk protein synthesis need to be clarified by future studies.     

不同养殖密度对瓦氏黄颡鱼肌肉中氨基酸组成的影响

目的探讨不同养殖密度对瓦氏黄颡鱼肌肉中氨基酸组成的影响。方法选用初始体重为(25.23±0.09)g的瓦氏黄颡鱼幼鱼600尾进行为期60 d的养殖实验,养殖密度分别设置为M1(20尾/m~3)、M2(40尾/m~3)、M3(60尾/m3)、M4(80尾/m~3)。分析各组瓦氏黄颡鱼肌肉氨基酸组成,以WHO/FAO模式、鸡蛋模式为参考,评价其氨基酸营养价值。结果 M3组瓦氏黄颡鱼肌肉蛋白的赖氨酸、天门冬氨酸、甘氨酸含量及必需氨基酸指数(essential amino acid index,EAAI)、氨基酸评分(amino acid score,AAS)、化学评分(chemical score,CS)、必需氨基酸总量(ΣEAA)、氨基酸总量(total amino acids,TAA)、支链氨基酸/芳香族氨基酸(branched chain amino acid/aromatic amino acids,BC/A)和必需氨基酸总量/氨基酸总量(essential amino acids/total amino acids,E/T)、必需氨基酸总量/非必需氨基酸总量(essential amino acids/total non essential amino acids,E/N)值均显著高于其他组(P0.05);非必需氨基酸总量(ΣNEAA)、儿童非必需氨基酸总量(ΣCE)显著高于M1、M2(P0.05),与M4无显著性差异(P0.05);各类风味氨基酸、ΣBCAA和ΣAAA占氨基酸总量的比例各组无显著性差异(P0.05)。结论养殖密度会对瓦氏黄颡鱼肌肉蛋白氨基酸营养价值产生一定的影响。     

Inhibition of haemoglobin-mediated lipid oxidation in washed cod muscle and cod protein isolates by Fucus vesiculosus extract and fractions

The effects of Fucus vesiculosus extract and fractions towards haemoglobin- (Hb-) catalysed lipid oxidation in washed cod muscle system and cod protein isolates during ice storage were examined. The extract and fractions were characterised in terms of total phlorotannin content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferrous ion-chelating ability and reducing power. Progression of oxidation was followed by determining rancid odour, thiobarbituric acid reactive substances (TBARS), redness and volatile oxidation compounds by gas chromatography (GC). In both washed cod muscle and protein isolates, phlorotannin-enriched ethyl acetate (EtOAc) fraction showed higher inhibitory effect than crude 80% ethanol (EtOH) extract. The addition of oligomeric phlorotannin-rich subfraction (LH-2) separated by Sephadex LH-20 chromatography, completely inhibited the initiation of lipid peroxidation in both systems throughout the entire study period (8 days). Its effectiveness at 300 mg/kg level was comparable to that of 100 mg/kg propyl gallate (PG), a highly effective synthetic antioxidant in muscle foods. Although polymeric phlorotannin-rich subfraction (LH-5) had similar level of TPC and chemical antioxidant activities as oligomeric subfraction LH-2, it was far less efficient in model systems. These results suggest that other factors rather than the intrinsic reactivity toward radicals could be responsible for the inhibitory effect of phlorotannins on lipid oxidation in fish muscle. This study highlights the great potential of oligomeric phlorotannins as novel natural antioxidants in fish and fish products.     

直接氨基酸法测定乳清粉中氨基酸

本文通过使用氨基酸直接分析法——离子交换色谱-积分脉冲安培法（HPIC—IPAD）对乳清中游离的氨基酸和水解后乳清粉中的氨基酸进行检测分析。结果表明，可以检测到孔清粉中含有游离氨基酸6种，水解以后可以检测到15种氨基酸．而且氨基酸的保留时间（Rt）相对标准偏差（RSD）平均为1．843％，峰面积RSD平均为2．6174％。     

用氨基酸自动分析仪测定婴幼儿配方奶粉中的16种氨基酸

通过盐酸水解——氨基酸自动分析仪法,测定了婴幼儿配方奶粉中的16种氨基酸。结果表明,在12.5～250μmol/L的线性范围内相关系数均达到0.999以上,6组平行样的重复性变异系数均在2.0%以内,16种氨基酸3个浓度梯度的平均回收率均在95.0%～105.1%之间;应用盐酸水解法得到的待测液常温(20～28℃)放置5h及20h后,除Met外其余15种氨基酸5h后的平均损失率均在1%以下,Met的实际平均损失量也分别在5h0.005nmol/20μL和20h0.020nmol/20μL以下。结论说明,利用该法能得到十分理想的分离效果和相对准确的分析结果。     

茶叶中游离氨基酸含量的荧光光度法测定

本文采用邻苯二甲醛(OPA)衍生法，OPA在β-巯基乙醇(β—MCK)存在下与第一级氨基酸迅速反应生成1—硫代—2—烷基异吲哚，此生成物具有荧光，从而利用荧光光度法测定茶叶中的游离氨基酸含量。实验对该法的精密度，准确性以及稳定性均进行探讨。在激发波长Ex为360nm，发射波长Em为420nm时，标准直线方程为Y＝1．3303X 0．2329，相关系数γ＝0．9999。结果表明：茶叶中含有丰富的游离氨基酸，总量为2．7—3.2g／100g，回收率达99．14％。     

天然食用香料浸膏中氨基酸的分析

采用酸水解法和氨基酸自动分析仪测定了茉莉浸膏、杭白菊浸膏、桂花浸膏、酒花浸膏、鸢尾浸膏、树兰花浸膏、枫槭浸膏和树苔浸膏共8类天然食用香料浸膏(共22个样品)中16种氨基酸的含量,如天冬氨酸(Asp)、苏氨酸(Thr)、丝氨酸(Ser)等。研究结果表明,除了茉莉浸膏、酒花浸膏、爱普鸢尾浸膏中未检测到氨基酸外,其他浸膏都含有氨基酸,种类基本相同,但氨基酸的总量均偏低,在5.29~833.54mg/100g之间;杭白菊浸膏中氨基酸的平均总量最高769.13mg/100g,其中拓普杭白菊浸膏氨基酸总量最高,为833.54mg/100g;树兰花浸膏中氨基酸平均总量最少6.135mg/100g,其中烟草树兰花浸膏中氨基酸总量最少,为5.29mg/100g。单因素方差分析结果表明,不同浸膏中氨基酸的含量具有显著性差异;聚类分析结果表明,所测浸膏主要分为两大类,第一大类包括树兰花浸膏、桂花浸膏、枫槭浸膏、树苔浸膏,第二大类是杭白菊浸膏。     

Toxicological effect of a fatty acid mixture in rats

The effects of a fatty acids mixture containing nearly 50% odd numbered fatty acids (PC-S?ure) were studied in a subchronic toxicity test in male and female rats. The animals received PC-S?ure in their diet at levels of 0, 1.25, 2.5 and 5% for 13 weeks. Food intake was increased at 5% PC-S?ure level in males. Food efficiency was initially decreased in males and females of this group. Ingestion of PC-S?ure resulted in increases of the urine volume and the urinary lactate dehydrogenase activity in both sexes. Male and female rats fed PC-S?ure showed elevated serum activities of alkaline phosphatase and leucine aminopeptidase and decreases in serum cholesterol and triglycerides. Dietary PC-S?ure elevated the serum creatinine content in males at the two highest levels. A transitory increase in the activity of the serum alanine aminotransferase was observed in females fed 5% PC-S?ure. Increased liver and kidney weights were found in both sexes.     

A liquid medium for growth of the thermophilic campylobacters in a carbon dioxide air mixture as studied by polymyxin-cloth enzyme immunoassay

A new liquid medium containing casein hydrolysate, beef extract, yeast extract, biocarbonate and an erythrocyte digest was developed for growth ofCampylobacter jejuniand other thermophilic campylobacter species. 26 strains, consisting of six Penner serotypes and the 20 most common Lior serogroups, were evaluated and all grew well in this medium at 40°C in an atmosphere of 5% CO₂moist air. Furthermore, this medium allowed growth of these bacteria without exogenous CO₂at 40°C. After incubation for 28h in 5% CO₂or 36h without exogenous CO₂, cultures inoculated with approximately 10²colony forming units (CFU)/ml reached cell densities of 10⁶to 10⁹(mean 10⁸) CFU/ml and produced positive signals in the polymyxin-cloth enzyme immunoassay. This medium therefore has the potential to provide rapid and affordable isolation of these pathogens for a Hazard Analysis Critical Control Point program.     

荧光光度法测定白果中游离氨基酸含量

采用邻苯二甲醛 (OPA)衍生法 ,OPA在β-巯基乙醇 (β-MCE)存在下与游离氨基酸迅速反应生成 1-硫代 - 2 -烷基异吲哚 ,此加成物具有荧光 ,从而利用荧光光度法测定市售白果中的游离氨基酸总量。实验对该法的精密度、稳定性以及准确性均进行探讨。在激发波长EX为 330nm、发射波长EM为 4 70nm荧光条件下 ,标准直线方程为Y =0 .995 0X + 0 .2 0 6 3、相关系数γ=0 .9999,回收率达 99.10 %。结果表明 :白果中含丰富的游离氨基酸 ,其总量达 0 .8- 1.0g/10 0g。     

Evaluation of antioxidative activity of vegetable extracts in linoleic acid emulsion and phospholipid bilayers

The antioxidative effects of vegetable extracts were evaluated using linoleic acid emulsion and liposomal phospholipid suspension systems. First, the antioxidative activities of water, ethanol and 2% metaphosphoric acid extracts of the vegetables were investigated by measuring the rate of oxygen consumption in the peroxidation of linoleic acid initiated by a radical generator, 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH), with a Clark electrode in the absence of metal chelators. Ethanol extracts of moroheiya and perilla exhibited the highest antioxidative activities. Without metal chelators, 12 ethanol extracts and one water extract acted as prooxidants, and this phenomenon could be attributed to the prooxidant action of ascorbic acid in the presence of free transition metal ions. Next, peroxyl radical-scavenging activities of vegetable extracts were examined by adding a metal chelator, diethylenetriaminepentaacetic acid (DTPA), to the linoleic acid emulsion system. The results were compared with their antioxidative activities in phospholipid bilayers by measuring the inhibition of lipid peroxidation in large unilamellar vesicles composed of egg yolk phosphatidylcholine (PC). A good correlation was observed between the antioxidative activities obtained from these two systems. The antioxidative activities in the liposomal phospholipid suspension system correlated with total contents of ascorbic acid and polyphenols in vegetable extracts. © 1999 Society of Chemical Industry