首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 62 毫秒
1.
《Journal of dairy science》2019,102(12):10934-10946
Modification of milk and cheese fat to contain long-chain n-3 fatty acids (FA) by feeding microalgae (ALG) to dairy cows has the potential to improve human health, but the subsequent effect on the sensory attributes of dairy products is unclear. The objective was to determine the effect of feeding dairy cows different amounts of ALG that was rich in docosahexaenoic acid (DHA) on milk and cheese FA profile, cheese sensory attributes, and cow performance. Twenty Holstein dairy cows were randomly allocated to 1 of 4 dietary treatments in a 4 × 4 row and column design, with 4 periods of 28 d, with cheddar cheese production and animal performance measurements undertaken during the final 7 d of each period. Cows were fed a basal diet that was supplemented with ALG (Schizochytrium limancinum) at 4 rates: 0 (control, C), 50 (LA), 100 (MA), or 150 g (HA) of ALG per cow per day. We found that both milk and cheese fat content of DHA increased linearly with ALG feed rate and was 0.29 g/100 g FA higher in milk and cheese from cows fed HA compared with C. Supplementation with ALG linearly reduced the content of saturated FA and the ratio of n-6:n-3 FA in milk and cheese. Supplementation with ALG altered 20 out of the 32 sensory attributes, with a linear increase in cheese air holes, nutty flavor, and dry mouth aftertaste with ALG inclusion. Creaminess of cheese decreased with ALG inclusion rate and was positively correlated with saturated FA content. We also observed a quadratic effect on fruity odor, which was highest in cheese from cows fed HA and lowest in LA, and firmness and crumbliness texture, being highest in MA and lowest in HA. Supplementation with ALG had no effect on the dry matter intake, milk yield, or live weight change of the cows, with mean values of 23.1, 38.5, and 0.34 kg/d respectively, but milk fat content decreased linearly, and energy-corrected milk yield tended to decrease linearly with rate of ALG inclusion (mean values of 39.6, 38.4, 37.1, and 35.9 g/kg, and 41.3, 41.3, 40.5, and 39.4 kg/d for C, LA, MA, and HA, respectively). We conclude that feeding ALG to high-yielding dairy cows improved milk and cheese content of DHA and altered cheese taste but not cow performance, although milk fat content reduced as inclusion rate increased.  相似文献   

2.
Skin tests of the nondialyzable fraction of lactose were performed on patients with a clinical diagnosis of cow's milk allergy. The yields of brownish-colored residue, allergens (ALG), were 0.006% from reagent grade lactose (ALG 1) and 0.011% from lactose used in a commercial infant food formula (ALG 2). The ALG was separated into four fractions by chromatography on Sephadex G-75. The highest incidences of positive skin reaction among the four ALG 1 and ALG 2 fractions were 8/9 and 8/12 respectively. The ALG fractions were identified as a sugar protein complex and the protein moiety of ALG contained high amounts of glutamic acid (or glutamine), threonin, asparagic acid (or asparagine) and proline.  相似文献   

3.
《Journal of dairy science》2019,102(6):5054-5065
This study aimed to evaluate the effects of increasing dietary levels of microalgae (ALG), rich in docosahexaenoic acid (DHA; All-G-Rich, Alltech, Nicholasville, KY), in isolipidic diets, on animal performance, nutrient digestibility, ruminal fermentation, milk fatty acid profile, energy balance, microbial protein synthesis, and blood serum metabolites in mid-lactating dairy cows. Twenty-four Holstein cows [130.3 ± 15.4 d in milk, and 30.8 ± 0.543 kg/d of milk yield (mean ± standard error)] were used in a 4 × 4 Latin square design experiment to evaluate the following treatments: control diet, without addition of ALG; and increasing levels of ALG [2, 4, and 6 g/kg of dry matter (DM)]. The ALG decreased DM intake and increased total-tract DM apparent digestibility. A tendency was observed for a quadratic effect on total-tract NDF digestibility by ALG inclusion, with peak value of the quadratic response at 4.13 g/kg of DM dose. Moreover, ALG increased ruminal pH and decreased acetate and total volatile fatty acid concentrations. Fat-corrected milk and energy-corrected milk were quadratically affected, and a tendency for a milk yield effect was observed when ALG levels increased, whereas maximal yields were observed with intermediate doses. Milk fat, protein, and lactose concentrations were diminished, whereas productive efficiency was improved by the increase of ALG levels. Saturated fatty acid proportions were decreased, whereas polyunsaturated fatty acid proportions were increased when ALG was fed. There was low DHA transfer into milk; however, ALG inclusion decreased C18:0, C18:1 cis-9, C18:2 cis-9,12, and C18:3 cis-9,12,15 proportions, and increased C18:2 cis-9,trans-11, C18:1 trans-9, and C18:1 trans-11 proportions. Gross energy intake was decreased, whereas no effect was observed on digestible, metabolizable, or net energy intake. The ALG inclusion quadratically affected the microbial protein synthesis, with maximal enhancement at 3.24 g/kg of DM dose, and also increased serum cholesterol concentration. Under the conditions of this experiment, the inclusion of ALG in diets for mid-lactating dairy cows decreased feed intake and increased nutrient digestibility, improving productive efficiency and modifying milk fatty acid profile. Estimated intermediate doses (1.22 to 2.90 g/kg of DM) of DHA-rich ALG may be beneficial to milk, fat-corrected milk, and energy-corrected milk yields, and is recommended for dairy cows.  相似文献   

4.
分别运用生物酶法和化学碱法,研究不同质量浓度花青素与大豆分离蛋白(soy protein isolate,SPI)发生共价相互作用后对蛋白结构的影响。采用共价结合率测定和游离巯基含量测定方法对花青素和SPI在不同共价交联方式下的结合强度进行比较,后采用傅里叶变换红外光谱、紫外-可见吸收光谱和荧光光谱对不同共价交联方式下的花青素-SPI共价聚合物的结构及构象进行解析。结果表明:随着花青素添加量的升高,花青素与SPI的结合率逐渐提升,游离巯基含量持续下降。光谱测定显示花青素对SPI的共价交联可以改变蛋白的二级结构,使蛋白多肽链解折叠,并且改变蛋白芳香族氨基酸残基所处的微环境,进而使蛋白的构象发生改变。此外,相较于化学碱法,生物酶法共价交联的花青素-SPI聚合物结合率更高,巯基含量下降更显著,结构及构象的变化更为明显,这表明花青素与SPI在生物酶法处理下,共价结合能力强于化学碱法处理。  相似文献   

5.
Soya protein isolate (SPI)/alginate (ALG)/montmorillonite (MMT)/thymol (THY) nanocomposite films were prepared with a codrying process to enhance the antimicrobial stability. The results showed higher gelation point temperature and more stable gelling network were obtained by the addition of MMT. Better thermal stability and sustained release effect was found in the coblended film containing MMT, in which THY release rate at 25 °C decreased with increasing MMT concentration but increased with temperature at a constant relative humidity. The SPI/ALG/THY, SPI/ALG/THY‐CO and SPI/ALG/THY‐CO‐0.6 (MMT content = 0.6 g g?1 SPI) films effectively inhibited the growth of Escherichia coli by 0.95, 0.91 and 0.70 log cfu mL?1 and of Staphylococcus aureus by 0.94, 0.89 and 0.73 log cfu mL?1, respectively, on the surface of raw sausage, compared to the control film.  相似文献   

6.
Camel milk (CM) set yogurts were formulated with gelatin, alginate (ALG), and calcium (Ca). Titratable acidity, pH, sensory properties, and acceptability of CM yogurts were studied. Twelve treatments were prepared; 3 using gelatin at 0.5, 0.75, and 1% levels and 9 with combinations of ALG and Ca at different levels. Titratable acidity and pH of fresh yogurt were not affected by the addition of gelatin or the ALG and Ca combinations. Trained sensory panel results showed that CM yogurt containing 1% gelatin or 0.75% ALG + 0.075% Ca had the highest intensities for firmness and body. Consumer results indicated that the hedonic ratings of the sensory attributes and acceptability of CM yogurt containing 0.75% ALG + 0.075% Ca were similar to that of cow's milk yogurt. The CM yogurts containing ALG + Ca and flavored with 4 different fruit concentrates (15%) had similar hedonic ratings and acceptability. Addition of 0.75% ALG + 0.075% Ca could be used to produce acceptable plain or flavored CM yogurt.  相似文献   

7.
《Food chemistry》2005,93(4):689-695
In this paper, the characteristics of purified conjugates formed between β-lactoglobulin (β-lg) and a high molecular weight dextran under different dry heating conditions were investigated. SDS–PAGE analyses under non-reducing and reducing conditions showed that glycation of β-lg led to the formation of high molecular weight complexes and induced polymerization of the protein by disulfide bonds. The fluorescence emission spectra did not show changes in λmax, which was indicative of a similar conformation around Trp residues. The conjugate formed at 60 °C, 0.44 aw and 2:1 weight ratio of dextran to β-lg (conjugate 1) exhibited a fluorescence intensity very similar to that of the native protein and was selected to study the influence of glycosylation on the solubility and heat-stability properties. Solubility of conjugate 1 was higher than that of the dry-heated β-lg in the pH range from 3 to 9 and, particularly, around the isoelectric point of the protein. As compared to the native protein, the solubility of the conjugate decreased at pH 4. The glycated β-lg presented lower stability to heating at pH 7.0 than native β-lg, but its thermal stability was higher at pH 5.0 at temperatures above 85 °C.  相似文献   

8.
探究卵白蛋白-白藜芦醇(ovalbumin-resveratrol,OVA-RES)相互作用机理以及RES对OVA潜在致敏性的影响。以OVA和RES为对象,利用荧光光谱法、圆二色谱法研究两者相互作用机理,解析其荧光猝灭类型、结合位点数、热力学参数和二级结构含量等信息,并在此基础上利用体外血清学IgG、IgE结合能力实验评估RES对OVA的潜在致敏性的影响。结果表明,RES可通过动态猝灭的形式猝灭OVA的荧光,且OVA-RES相互作用是以氢键和范德华力为主要作用力驱动的自发过程(ΔH<0、ΔS<0、ΔG<0)。RES可引起OVA氨基酸残基微环境和蛋白质构象的变化,从而使得OVA的潜在致敏性增加。  相似文献   

9.
Sixteen Holstein cows were assigned to 2 groups to evaluate the caloric and metabolic effect of feeding marine algae (ALG) from 3 wk prepartum until 12 wk postpartum. Milk production characteristics and the profiles of hormones and metabolites in the serum were monitored from −7 to 46 d in milk (DIM) and in follicular fluid (FF) from 14 to 46 DIM. All cows received a corn- and grass silage-based partially mixed ration supplemented with concentrate and protein supplement. In the diet of the ALG group, 2 kg of the concentrate was replaced by a concentrate containing ALG (44 g/d of docosahexaenoic acid). Diets were isocaloric (net energy basis) and equal in intestinal digestible protein. The ALG diet increased milk yield (41.2 vs. 38.2 kg/d) and decreased milk fat yield (1.181 vs. 1.493 kg/d) and milk fat content (31.6 vs. 40.7 g/kg). Protein yield (1.336 vs. 1.301 kg/d) was not affected but a tendency toward decreased milk protein content (32.8 vs. 34.7 g/kg) was observed. Marine algae supplementation increased the β-hydroxybutyric acid (BHBA) concentration in FF of the ALG cows compared with that in the controls (0.992 vs. 0.718 mmol/L). The total protein concentration in FF was decreased in ALG (62.9 vs. 67.6 g/L). Plasma and serum metabolites did not significantly differ between treatments except for a tendency toward a lower concentration of urea in the serum of the control compared with ALG (4.69 vs. 5.13 mmol/L). Based on metabolizable energy calculations, a daily energy-sparing effect of 3.48 Mcal was obtained due to milk fat depression (MFD). The concomitant increase in milk yield suggests that at least part of this spared energy is used to stimulate milk production. Theoretically, 3.48 Mcal of ME could lead to an increase in milk yield of 7.43 kg/d, which is higher than the observed 3 kg/d. However, when evaluating nutrient requirements during MFD in early lactation, we calculated that increased milk production is caused by a propionate-saving effect of 2.71 mol in the udder when milk fat is depressed. Concurrent increased BHBA concentrations in FF in the ALG group cannot be attributed to a worsened energy status of the animals because all other indicators contradict any change in energy balance, indicating that BHBA might not be an appropriate metabolic parameter to estimate the energy balance in early lactating dairy cows during MFD.  相似文献   

10.
In this study, we developed a new effective technology for the extraction of sericin from silk wastewater. Sericin was extracted with 75% (v/v) ethanol to obtain crude powder. The chemical composition of sericin powder, including protein, sugar, ash, and amino acid, was assayed in detail. The molecular weight distribution of sericin was also investigated by gel filtration chromatography, sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), and high performance liquid chromatography (HPLC) analytical methods. The results suggested that sericin represented a family of proteins with wide-ranging molecular weight distribution. The conformation changed in the course of ethanol precipitation was studied by circular dichroism (CD) analysis. Data implied that the major conformation of sericin protein was random coil, which decreased slightly after being treated with ethanol, and the appearance of β-Turn conformation maybe associated with the packing of molecular chains induced by ethanol. Furthermore, sericin was found to inhibit tyrosinase activity when chlorogenic acid was used as a substrate, and had obvious radical scavenging effects with the 2.2-diphenyl-1-picryl-hydrazil (DPPH) assay. Result suggested that sericin might be a valuable ingredient for food.  相似文献   

11.
A novel chitosan–phloroglucinol conjugate was developed by conjugating phloroglucinol onto a chitosan backbone. The chitosan–phloroglucinol conjugate was characterised by 1H nuclear magnetic resonance (NMR), and the NMR spectra confirmed the conjugation. Antioxidant and tyrosinase inhibitory activities of the chitosan–phloroglucinol conjugate were investigated. The chitosan–phloroglucinol conjugate showed strong 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), hydrogen peroxide and ABTS+ radical scavenging activities as well as reducing power compared with those of the unmodified chitosan (P < 0.05). The formation of malondiadehyde (MDA) as an indicator of lipid peroxidation in a linoleic acid emulsion was 30.56 μM in the absence of the chitosan–phloroglucinol conjugate after 4 days incubation, whereas MDA was 4.14 μM in the presence of the chitosan–phloroglucinol conjugate (P < 0.05). The activity was higher than that of ascorbic acid, which is currently used as a food preservative. Moreover, the chitosan–phloroglucinol conjugate inhibited 56.30% tyrosinase activity, which is responsible for browning of foods, and acted as non‐competitive inhibitor. Taken together, the chitosan–phloroglucinol conjugate may have potential for application in functional foods and/or as a food preservative.  相似文献   

12.
对SAPP与葡聚糖(DEX)复合物的乳化活性以及乳化稳定性等功能性质进行系统研究。结果表明,干热反应产物在pH3.0以及pH10.0时保持好的乳化活性;并且在高温、高盐条件下乳化活性变化很小。对反应产物进行差示扫描(DSC)分析,进一步证实蛋白已经与多糖结合反应生成新的化合物,该产物热稳定性很高,比原有蛋白的变性温度提高了几乎两倍。  相似文献   

13.
为探讨桃胶多糖(peach gum polysaccharide,PGP)发挥乳化作用的关键活性结构特征,采用0.1 mol/L三氟乙酸对PGP进行部分酸水解,通过控制水解时间制备得到不同水解度的PGP样品30P、60P、120P和180P,采用高效阴离子交换色谱和高效分子排阻色谱串联多角度激光光散射分析部分酸水解对PGP单糖组成和分子质量的影响,通过水包油(O/W)乳液体系探讨部分酸水解对PGP乳化功能的影响。结果表明:PGP是由阿拉伯糖、半乳糖、木糖、甘露糖、半乳糖醛酸和葡萄糖醛酸组成的一种酸性阿拉伯半乳聚糖,结合有少量蛋白质,重均分子质量为10 980 kU,在0.1 mol/L NaNO3溶液中呈宽分布的柔性卷曲链状;随着酸水解的进行,PGP的糖醛酸和蛋白质含量逐渐升高,分子质量逐渐减小,支化度降低,水解产物的分子构象由柔性线团结构向刚性棒状转变;研究表明,60P O/W乳液较PGP及其他水解产物形成的乳液稳定性明显提高,由此推测60P是PGP发挥乳化功能的关键活性结构特征,即分子质量为1 188 kU,支化度部分降低,糖醛酸和蛋白质缀合物含量较高的柔性链...  相似文献   

14.
ABSTRACT: The purpose of this study was to develop a method for applying an extra coating of palm oil and poly‐L‐lysine (POPL) to alginate (ALG) microcapsules to enhance the survival of probiotic bacteria. Eight strains of probiotic bacteria including Lactobacillus rhamnosus, Bifidobacterium longum, L. salivarius, L. plantarum, L. acidophilus, L. paracasei, B. lactis type Bl‐O4, and B. lactis type Bi‐07 were encapsulated using alginate alone or alginate with POPL. Electron microscopy was used to measure the size of the microcapsules and to determine their surface texture. To assess if the addition of POPL improved the viability of probiotic bacteria in acidic conditions, both ALG and POPL microcapsules were inoculated into pH 2.0 MRS broths and their viability was assessed over a 2‐h incubation period. Two bile salts including oxgall bile salt and taurocholic acid were used to test the bile tolerance of probiotic bacteria entrapped in ALG and POPL microcapsules. To assess the porosity and the ability of the microcapsule to hold small molecules in an aqueous environment a water‐soluble fluorescent dye, 6‐carboxyflourescin (6 FAM), was encapsulated and its release was monitored using a UV spectrophotometer. The results indicated that coating the microcapsules with POPL increased the overall size of the capsules by an average of 3 μm ± 0.67. However, microcapsules with added POPL had a much smoother surface texture when examined under an electron microscope. The results also indicated that the addition of POPL to microcapsules improved the average viability of probiotic bacteria by > 1 log CFU/mL when compared to ALG microcapsules at 2 h of exposure to acidic conditions. However, similar plate counts were observed between ALG and POPL microcapsules when exposed to bile salts. This suggests that an extra coating of POPL could be readily broken down by bile salts that are commonly found in the lower gastrointestinal tract (GIT). Upon testing the porosity of the microcapsules, findings suggest that POPL microcapsules were less porous and hold 52.2% more fluorescent dye over a 6‐wk storage period.  相似文献   

15.
Previously, we characterised the presence of ubiquitin and some ubiquitinated proteins (conjugates), which were considered as ubiquitin conjugates in the sarcoplasmic fraction of postmortem skeletal and cardiac muscles using SDS–PAGE and Western blot. In this study, an ubiquitin conjugate around 27 kDa was subjected to identification. The N-terminal amino acid sequence analysis generated by Edman degradation resulted in a 13 amino acid sequence (KIQFTVPLLEPHL), which is similar to that of Protein Phosphatase Inhibitor 1. Based on this result, Western blot analysis was performed by using a polyclonal antibody for Protein Phosphatase Inhibitor 1 and the conjugate was recognised and reacted clearly. Thus, the ubiquitinated protein around 27 kDa is identified as Protein Phosphatase Inhibitor 1.  相似文献   

16.
Steaks, fabricated with hot- (HB) or cold-boned (CB) beef and structured with salt/phosphate (SP), sodium alginate (ALG), or ALG and albumin, were packaged aerobically and anaerobically and displayed at 2°C for up to 30 days to determine effects of boning methods and binders on structured steak properties. Using SP and CB meat resulted in darker (p< 0.05) non-bloomed and bloomed steaks. Adding albumin had little effect on changing color of ALG steaks. Steaks with stronger cohesion (p<0.05) were produced when SP was used. Structured steaks fabricated with CB meat were more tender than those made using HB meat. In addition, steaks made with either meat type exhibited similar binding properties (p<0.05).  相似文献   

17.
Quality and shelf-life of Asian sea bass slices (ASBS) wrapped with chitosan (CS)/CS–epigallocatechin gallate (CE) conjugate composite or CS films and packaged in air or under vacuum during storage at 4 °C were studied. Total viable count was less than permissible limit (6 log·CFU g−1 sample) for ASBS wrapped with CS/CE conjugate composite film under vacuum (ASBS-COMP-VP) after 18 days. Moreover, lower microbial proliferation and volatile base contents were attained in ASBS-COMP-VP sample than other samples during the storage (P < 0.05). At the end of storage, ASBS-COMP-VP sample had lower lipid oxidation than those wrapped with CS film (P < 0.05). Polyunsaturated fatty acid content of ASBS-COMP-VP was retained at higher content at day 18. Therefore, ASBS-COMP-VP had the enhanced shelf-life with high acceptability up to 18 days at 4 °C, while ASBS wrapped with CS film and packaged in air or under vacuum had the shelf-life of 9 and 12 days, respectively.  相似文献   

18.
以天然大豆油脂体替代传统沙拉汁中的油脂,并利用多糖海藻酸钠(ALG)作为稳定剂制备新型沙拉汁。结果表明,通过带负电ALG与带正电油脂体的静电相互作用,提高了天然大豆油脂体在弱酸性条件下的分散性和稳定性,0.35%的ALG可在pH4.5下很好地稳定1.0%油脂体乳液。通过体外模拟小肠内油脂消化过程,发现天然大豆油脂体乳液比吐温80-大豆油乳液的游离脂肪酸释放量低10%左右,且ALG进一步延缓了大豆油脂体初期消化速度。高浓度的ALG(0.5%、0.6%、0.8%、1.0%)可分别提高高浓度油脂体乳液(10.0%、20.0%、30.0%、40.0%)的稳定性。以市售沙拉汁为对照,优化了沙拉汁配方中大豆油脂体与ALG的用量,将质量分数为60.0%的大豆油脂体-ALG的乳液(含40.0%油脂体和1.0% ALG)用于沙拉汁配方中,得到粘度与市售配方匹配,稳定性更佳的沙拉汁。新型沙拉汁配方综合了大豆油脂体和海藻酸钠的双重优点,具有含油量低、脂肪消化慢、营养素天然健康,且储存稳定的特点。  相似文献   

19.
Treatments of chitosan-epigallocatechin gallate (CE) conjugate nanoliposome (CELP) and unencapsulated CE conjugate (UNCE) at different concentrations (0.025  and 0.05 g 100 g−1) on quality and shelf-life of Asian sea bass slices (ASB-S) kept at 4 °C were studied. Total viable count of ASB-S treated with 0.05 g 100 g−1 CELP (SB-CELP-0.05) was less than permissible limit (6 log CFUg−1 sample) within 15 days. Moreover, SB-CELP-0.05 sample had the lowest pathogenic and spoilage bacterial count than remaining samples during the storage (P < 0.05). Lower thiobarbituric acid reactive substances and peroxide values were obtained for SB-CELP-0.05 sample than those treated with 0.05 g 100 g−1 UNCE (SB-UNCE-0.05) at the end of storage (P < 0.05). The result was also advocated by higher polyunsaturated fatty acid content of SB-CELP-0.05 than SB-UNCE-0.05 (P < 0.05). Therefore, CELP efficiently extended ASB-S shelf-life with high consumer acceptability at 4 °C for minimum 12 days, whereas control had the shelf-life less than 6 days.  相似文献   

20.
陈梅  张锋  明津法  高艳菲  左保齐 《丝绸》2012,(6):5-7,30
以甲酸为溶剂,采用静电纺丝方法制备丝素蛋白(SF)与不同相对分子质量的透明质酸(HA)共混纳米纤维,并通过扫描电镜(SEM)、红外光谱(FTIR)、X射线衍射(XRD)和热分析(TG-DTA)研究了SF-HA共混纳米纤维非织造网的形态、结构和性能。结果表明:通过静电纺丝,丝素与低分子量的透明质酸共混纳米纤维直径在100 nm左右,纤维表面光滑,呈圆柱状;高分子量透明质酸的加入使得纤维形态变差,出现严重的粘连现象;透明质酸的加入未对丝素分子构象和结晶结构产生明显影响。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号