枯草杆菌碱性蛋白酶水解玉米皮蛋白

以枯草杆菌碱性蛋白酶对玉米皮进行水解,制取玉米蛋白水解液,结果,该酶水解的最佳工艺条件为：在浓度5％的玉米皮中加2．67％酶制剂,pH7.5,55度反应1h,制得的蛋白水解液中,蛋白质溶出率为89．3％,水解度为9．0％。     

菊糖芽孢乳杆菌利用麸皮水解液发酵生产D-乳酸

考察菊糖芽孢乳杆菌YBS1-5利用麸皮的水解液发酵生产D-乳酸的性能。首先研究了不同蛋白酶对麸皮中蛋白组分的水解效率,优选酸性蛋白酶并对其进行水解工艺的优化,最终其水解液中的含氮量为4.6 g/L,水解效率为85.8%。对酸性蛋白酶的水解液残渣进行稀酸预处理后,利用纤维素酶对其进行酶解。通过批次补料酶解,水解液中的还原糖质量浓度达141.2 g/L,其中葡萄糖质量浓度为138.1 g/L、木糖质量浓度为1.4 g/L。利用麸皮的蛋白酶水解液和纤维素酶水解液替代葡萄糖和酵母粉发酵制备D-乳酸。在96 h内,D-乳酸产量达99.5 g/L,生产速率达1.04 g/(L·h),转化率89.1%。     

微波水解制备鱼蛋白的研究

采用微波水解的方法制备鱼蛋白水解液,结果表明:微波可以明显增加蛋白质回收率,正交实验得到微波酸解的最适条件,即HCl浓度4 mol·L-1、微波功率450w、作用时间为30min,其水解液的蛋白质回收率可达到91.02％,相当于酶解的效果,且腥苦昧较小。     

酶解魔芋飞粉制备高F值寡肽最佳工艺条件的研究

目的:为了得到高F值寡肽,需要对蛋白质进行水解。方法:采用酶法水解魔芋飞粉制备高F值寡肽。通过对蛋白质水解度的测定,确定了碱性蛋白酶和链霉蛋白酶的最佳酶解条件:碱性蛋白酶加酶量0.1%,底物浓度3.75%,pH9.0,水解温度45℃,时间5h;链霉蛋白酶加酶量0.03%,pH8.0,水解温度50℃,时间7h。酶解液再经过凝胶层析分离纯化后可用于制备高F值寡肽。     

米糠蛋白抗氧化活性肽的制备

以水解度(DH％)和对DPPH自由基清除率为指标,筛选出制备米糠蛋白抗氧化活性肽的最适蛋白酶.研究最适蛋白酶的酶解条件,探讨底物浓度、蛋白酶的加入量、pH值、酶解时间等因素对水解度(DH％)和DPPH自由基清除率的影响;在单因素基础上采用Box-Behnken响应曲面中心组合设计法,对酶解米糠蛋白的工艺进行优化.试验结果表明,在加酶量13970.82 U/g,时间3.05h,底物浓度4.97％的水解条件下,米糠蛋白的水解度能够达到23.67％,活性肽对DPPH自由基清除率达到64.26％.     

胃蛋白酶和木瓜蛋白酶水解核桃蛋白工艺研究

以核桃粕为原料,以水解度为考察指标,研究胃蛋白酶和木瓜蛋白酶对核桃蛋白的水解作用.结果表明：木瓜蛋白酶为酶解核桃蛋白最佳酶,其最佳酶解条件为底物浓度4％、酶质量分数5％、酶解 pH 值为7．0、酶解温度50℃、酶解时间4 h;在该条件下,木瓜蛋白酶酶解核桃蛋白水解度可高于25．76％.     

响应曲面法制备蛹虫草子实体酶解液的研究

为了将蛹虫草开发成为便于人们食用的产品形式,本实验以不同的酶对蛹虫草进行水解得到蛹虫草酶解液.以水解度和酶解液中腺苷含量为目标,确定选用木瓜蛋白酶.以水解度为响应指标,应用响应曲面法对蛹虫草酶解条件进行优化,根据Box-Behnken中心组合实验设计原理,选取酶解温度、酶解时间、加酶量三因素三水平进行中心组合实验,响应曲面分析结果表明水解最佳条件为:酶解温度60.92℃,酶解时间11.85 h,加酶量1.02％,此条件下蛹虫草的水解度达到最大.水解度验证值61.27％与预测值60.76％接近,说明建立模型正确.     

牦牛骨蛋白的酶解条件研究

以蛋白质水解度为评价指标,辅以固形物溶出率,比较了中性蛋白酶、菠萝蛋白酶和木瓜蛋白酶对牦牛骨蛋白的水解效果,研究了酶用量、料液比(底物浓度)、酶解时间对水解度的影响,采用正交试验对酶解条件进行了优化。结果显示,木瓜蛋白酶是牦牛骨蛋白水解的适宜催化剂。在一定条件下,样品水解度随酶用量和酶解时间的增加而增大,底物浓度过低或过高均不利于原料中蛋白质的酶解。木瓜蛋白酶水解牦牛骨蛋白最佳条件为:酶解温度60℃,酶解时间8 h,酶用量3500 U/g蛋白质,料液比1:25(g:m l)。     

复合酶法水解香菇工艺的研究

【目的】高效提取香菇中的功能性成分,进一步开发利用香菇的食用价值。【方法】以香菇为原料,在单因素试验和正交试验的基础上,研究了复合酶法(纤维素酶、木瓜蛋白酶和5-磷酸二酯酶)水解香菇的工艺条件。【结果】第一步为纤维素酶和木瓜蛋白酶共同水解,加酶量分别为0.2%和0.4%,水解温度55°C,水解时间3 h,初始pH 5.5;第二步为5-磷酸二酯酶水解,加酶量为0.2%,水解温度70°C,水解时间2 h,初始pH 7.0。用此法得到的香菇水解液水解度为39.48%,游离氨基酸得率10.25%,5-核苷酸得率0.768%,多糖得率8.67%。【结论】此香菇水解液富含呈鲜味物质和其它营养物质,可进一步深加工为香菇调味品。     

响应面法优化豆粕固态发酵工艺的研究

采用SAS 9.1.3中的响应面分析法（中心组合一致精度设计）对影响豆粕固态发酵中蛋白质水解的四个主要因素（料水比,加酶量,发酵时间,接种量）进行了优化,考察了各因素及其交互作用对大豆蛋白水解度的影响。通过模拟二次多项式回归预测模型并建立了影响因素与响应值（水解度）之间的函数关系,即回归方程,根据回归方程寻优得出,当料水比1：1.00,加酶量2.55％,发酵时间65h,接种量1.00％时水解度可达13.3％,且比优化前提高了56％。     

Morphometric and enzyme histochemical behaviour of the kidney of young rats before and after unilateral nephrectomy.

Four week old male Wistar rats were unilaterally nephrectomized, and one, two, four, fourteen, and twenty-eight days after the operation the remaining kidneys were removed for morphological examination--including measurement of diameters of the tubules--and for histochemical investigation of enzymatic activities in the nephrons. The following enzymes were examined: succinate DH, lactate DH, alpha-glycerophosphate DH, isocitrate DH, glucose-6-phosphate DH, cytochrome oxidase, adenosine triphosphatase, alkaline and acid phosphatases. In comparison with kidneys of control animals of the same age and sex, the hypertrophy of the remaining kidney was found to be, even in these young rats, entirely due to enlargement of preexisting nephrons. The measurements have indicated that the hypertrophy was most distinct between the second and fourth day after uninephrectomy. Four weeks after the operation the diameters of proximal and distal tubules were about 21% and 18% respectively bigger in the uninephrectomized animals than in the corresponding controls. This increase in size was accompanied by some changes in intensity of enzymatic staining reactions; after an initial diminishment, a graduate increase in activity of almost all the observed tubular enzymes was found; this seems to be the expression of the functional compensation by the remaining kidney.     

Morphometric and enzyme histochemical behaviour of the kidney of young rats before and after unilateral nephrectomy

Summary Four week old male Wistar rats were unilaterally nephrectomized, and one, two, four, fourteen, and twenty-eight days after the operation the remaining kidneys were removed for morphological examination—including measurement of diameters of the tubules—and for histochemical investigation of enzymatic activities in the nephrons. The following enzymes were examined: succinate DH, lactate DH, α-glycerophosphate DH, isocitrate DH, glucose-6-phosphate DH, cytochrome oxidase, adenosine triphosphatase, alkaline and acid phosphatases. In comparison with kidneys of control animals of the same age and sex, the hypertrophy of the remaining kidney was found to be, even in these young rats, entirely due to enlargement of preexisting nephrons. The measurements have indicated that the hypertrophy was most distinct between the second and fourth day after uninephrectomy. Four weeks after the operation the diameters of proximal and distal tubules were about 21% and 18% respectively bigger in the uninephrectomized animals than in the corresponding controls. This increase in size was accompanied by some changes in intensity of enzymatic staining reactions; after an intial diminishment, a graduate increase in activity of almost all the observed tubular enzymes was found; this seems to be the expression of the functional compensation by the remaining kidney. Paper dedicated to Professor Dr. Drs. h. c. W. Bargmann (Kiel) in honour of the 70th anniversary of his birthday.     

SENSORY CHARACTERISTICS OF POTASSIUM LACTATE AND SODIUM CHLORIDE IN A MODEL SYSTEM

The objective of this study was to assess the sensory characteristics of potassium lactate (PL) in combination with salt (NaCl) in a model system at common usage levels for meat systems. Using a gelatin-based (3%) model system containing various concentrations of potassium lactate (0%, 1%, 2%, and 3%) and sodium chloride (0%, 0.5%, 1%, 1.5%, 2%, 2.5%, and 3%), a sensory panel (10) selected for salt sensitivity (0.08% threshold or less) scored the intensity of saltiness and bitterness of each treatment combination using a scale of 0 = none and 15 = intense. As salt concentration increased, saltiness increased and bitterness decreased; as PL increased, saltiness and bitterness increased. At 2% salt, the bitterness of PL was masked; however, salt concentrations below and above 2% were less effective in bitterness reduction.     

苦瓜主要品质性状的遗传变异、相关和通径分析

对23份苦瓜材料的10个品质性状进行了研究。结果表明,苦瓜维生素C、还原糖、有机酸、果瘤、果色、果刺和苦味遗传变异系数大,遗传力高;水分含量遗传变异系数很小;风味遗传变异系数较小,遗传力低。苦瓜4个内在营养品质之间相关性小,而4个外观品质性状之间关系密切。两个味觉品质与4个内在营养品质之间相关性小,但与4个外观品质之间关系密切。内在营养品质与外观品质之间有一定关系。通径分析提出通过降低果实的苦味和有机酸含量来提高风味品质;通过水分含量和果瘤两性状的直接选择来实现对维生素C的间接选择。     

三个小黑麦花粉株系的染色体组成分析与抗白粉病鉴定

对来自小黑麦与小麦杂种的３个花粉株系,ＤＨ２２０－４,ＤＨ２２０－５和ＤＨ２２０－１４进行了形态性状观察,染色体组成分析和抗白粉病鉴定。经过染色体形态和数目观察、原位杂交、Ｃ－分带、同工酶等电聚焦和贮藏蛋白的ＳＤＳ－聚丙烯酰胺凝胶电泳分析,证明其中两个株系,ＤＨ２２０－４和ＤＨ２２０－５是６Ｒ／６Ｄ代换系,另一个株系ＤＨ２２０－１４是１Ｒ／１Ｄ代换系。经人工接种鉴定,两个６Ｒ／６Ｄ代换系高抗白粉病。从而进一步证明黑麦的６Ｒ染色体上存在抗白粉病的基因。同时还对小麦遗传背景下异源染色体的识别及６Ｒ染色体的利用价值等问题进行了讨论。     

EFFECTIVENESS OF RINSES IN ALLEVIATING BITTERNESS AND ASTRINGENCY RESIDUALS IN MODEL SOLUTIONS1,2

A two‐part study determined the effectiveness of gum‐based rinses with or without oil for alleviating residuals of a bitter (0.8 g/L caffeine solution) and an astringent (1g/L alum solution) stimuli in serial responses using a sip and spit method. In Experiment 1, rinsing with deionized water was compared to rinsing with 0.3% xanthan gum in water alone or with 5% corn oil and 0.55% carboxymethyl cellulose (CMC) in water alone or with 5% or 10% corn oil. The 0.3% xanthan gum and 5% corn oil mixture resulted in the highest stimulus intensity difference before and after rinsing, whereas 0.55% CMC had a value of nearly zero for residual effect. Results of a two‐alternative forced choice test used in Experiment 2 indicated that both were equally effective for reducing bitterness residuals, but 0.55% CMC solution resulted in the lowest (p=0.007) residual effect for astringency. Therefore, the 0.55% CMC rinse was considered an effective interstimulus rinse to use for assessing both bitterness and astringency in model solutions.     

Clinical bitterness masking test for phantogeusia

It is difficult to determine the reason why a patient complains of a bitter taste when their mouth is empty. We examined a new diagnostic test using a bitterness masking substance. The bitterness masking substance, 'Benecoat BMI-60' (hereafter BMI-60), is a masking substance specific to the taste cells' bitterness receptors. After patients gargled with BMI-60 solutions, the phantom sensation of bitterness was masked in some patients, but was not masked in others. Bitter substances in saliva seemed to be masked by BMI-60, but bitterness did not seem to be masked when the locus of the phantom sensation was within the peripheral nerve and/or the brain. The bitterness masking test is useful for diagnosis of the phantom sensation of bitter taste.     

Protein hydrolysates from Bluefin Tuna (Thunnus thynnus) heads as influenced by the extent of enzymatic hydrolysis

Functional properties and antioxidant activities of protein hydrolysates from tuna (Thunnus thynnus) heads (THPHs), with different degrees of hydrolysis, obtained by treatment with Bacillus mojavensis A21 alkaline proteases and Alcalase, were investigated. Protein content of all freeze-dried THPHs ranged from 73.74 ± 0.5 to 78.56 ± 1.2%. The THPHs had excellent solubility, compared to untreated tuna head proteins and possessed interfacial properties, which were governed by their concentrations. Similarly, at a degree of hydrolysis (DH) of 12 and 15%, > 90% nitrogen solubility was observed at all experimental pH values tested. The emulsifying activity index (EAI) and emulsion stability index (ESI) of both hydrolysates at different DHs decreased (p < 0.05) with increasing DH. At low DH (5%), hydrolysates exhibited strong emulsifying properties. All THPHs produced by the A21 proteases generally showed higher antioxidative activity than that of the Alcalase protein hydrolysates. The highest DPPH radical-scavenging activity (78 ± 2.1% at 3 mg/mL) was obtained with a DH of 15%. The IC₅₀ value for the β-carotene bleaching assay was 0.5 ± 0.03 mg/mL. Alcalase (DH = 12%) and A21 (DH = 15%) protein hydrolysates contained glutamic acid/glutamine and arginine as the major amino acids, followed by lysine, aspartic acid/ asparagine, histidine, valine, phenylalanine, and leucine. In addition, the THPHs had a high percentage of essential amino acids, which made up 50.52 and 50.47%, of the protein hydrolysates obtained by the Alcalase and A21 proteases, respectively. Therefore, THPHs can be used as a promising source of functional peptides with antioxidant properties.     

Cross-adaptation and bitterness inhibition of L-tryptophan, L-phenylalanine and urea: further support for shared peripheral physiology

A previous study investigating individuals' bitterness sensitivities found a close association among three compounds: L-tryptophan (L-trp), L-phenylalanine (L-phe) and urea (Delwiche et al., 2001, Percept. Psychophys. 63, 761-776). In the present experiment, psychophysical cross-adaptation and bitterness inhibition experiments were performed on these three compounds to determine whether the bitterness could be differentially affected by either technique. If the two experimental approaches failed to differentiate L-trp, L-phe and urea's bitterness, then we may infer they share peripheral physiological mechanisms involved in bitter taste. All compounds were intensity matched in each of 13 subjects, so the judgments of adaptation or bitterness inhibition would be based on equal initial magnitudes and, therefore, directly comparable. In the first experiment, cross-adaptation of bitterness between the amino acids was high (>80%) and reciprocal. Urea and quinine-HCl (control) did not cross-adapt with the amino acids symmetrically. In a second experiment, the sodium salts, NaCl and Na gluconate, did not differentially inhibit the bitterness of L-trp, L-phe and urea, but the control compound, MgSO(4), was differentially affected. The bitter inhibition experiment supports the hypothesis that L-trp, L-phe and urea share peripheral bitter taste mechanisms, while the adaptation experiment revealed subtle differences between urea and the amino acids indicating that urea and the amino acids activate only partially overlapping bitter taste mechanisms.     

The influence of sodium salts on binary mixtures of bitter-tasting compounds

In order to study potential mixture interactions among bitter compounds, selected sodium salts were added to five compounds presented either alone or as binary bitter-compound mixtures. Each compound was tested at a concentration that elicited 'weak' perceived bitterness. The bitter compounds were mixed at these concentrations to form a subset of possible binary mixtures. For comparison, the concentration of each solitary compound was doubled to measure bitterness inhibition at the higher intensity level elicited by the mixtures. The following sodium salts were tested for bitterness inhibition: 100 mM sodium chloride (salty), 100 mM sodium gluconate (salty), 100 and 20 mM monosodium glutamate (umami), and 50 mM adenosine monophosphate disodium salt (umami). Sucrose (sweet) was also employed as a bitterness suppressor. The sodium salts differentially suppressed the bitterness of compounds and their binary combinations. Although most bitter compounds were suppressed, the bitterness of tetralone was not suppressed, nor was the bitterness of the binary mixtures that contained it. In general, the percent suppression of binary mixtures of compounds was predicted by the average percent suppression of its two components. Within the constraints of the present study, the bitterness of mixtures was suppressed by sodium salts and sucrose independently, with few bitter interactions. This is consistent with observations that the bitter taste system integrates the bitterness of multi-compound solutions linearly.