发酵香肠源抗氧化肽的稳定性

研究发酵香肠抗氧化肽在生产加工及胃肠消化过程中的稳定性。以1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基清除活性、Fe~(2+)螯合活性和2,2’-联氮双(3-乙基苯并噻唑啉-6-磺酸)(2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid),ABTS)总抗氧化能力为指标,考察温度、pH值、食品配料、金属离子以及模拟胃肠消化对抗氧化肽活性的影响。结果表明,高温和酸碱性环境中自由基清除率下降明显(P0.05),Fe~(2+)螯合率增加,但增幅较小;NaCl和糖类有利于提高抗氧化肽的自由基清除活性,对Fe~(2+)螯合活性有抑制作用;添加量在国标允许范围内时,NaNO_2对抗氧化肽活性影响不大;相比于K+,抗氧化肽对Cu2+更为敏感;模拟胃肠道消化结束后,DPPH自由基清除活性完全丧失,但Fe~(2+)螯合活性增强至消化前的1.4倍,ABTS阳离子自由基清除率稳定在40%左右,总游离氨基酸含量逐渐增加。     

草鱼鱼皮不同分子量肽段体外抗氧化性能的研究

采用碱性蛋白酶对草鱼皮进行水解,并将水解产物通过截留分子量为10、5和3 k Da的超滤膜,得到10、5~10、3~5和3 k Da四种不同分子量肽段组分。主要研究了粗蛋白水解产物经截留后不同分子量肽段的体外抗氧化活性及其功能,结果表明相同浓度下3~5和3 k Da肽段组分在清除1,1-二苯基-2-三硝基苯肼(DPPH)和2,2'-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐(ABTS)自由基方面比蛋白水解产物或其它肽段组分的效果显著(p0.05),而10 k Da肽段组分与Fe2+螯合能力最强。然而,与还原型的L-谷胱甘肽相比,10、5~10、3~5 k Da肽段组分具有较弱的清除超氧阴离子自由基能力,肽的氨基酸序列在其抗氧化活性中起到关键作用。结果表明,3 k Da肽段组分可作为功能性天然抗氧化剂添加到保健食品中。     

玉米醇溶蛋白抗氧化肽耐消化性研究

主要研究了玉米蛋白水解物的抗氧化性和耐消化性.通过(胃蛋白酶1h,胰蛋白酶2h)两阶段消化实验,探讨了抗氧化玉米水解物的耐消化性,以ABTS+ ·自由基清除能力和Cu2+螯合能力为抗氧化指标,并利用高效凝胶排阻色谱(HPSEC)来测定消化产物的分子量分布.研究表明,分子量小于500Da的产物几乎占总消化产物的70%,经过胃蛋白酶消化,ABTS+·自由基清除能力下降了近20%(P<0.05),但在随后的胰蛋白酶消化过程中活性逐步提高,最后完全恢复;Cu2+螯合能力具有与ABTS+·自由基清除能力相似的变化趋势.虽然玉米水解产物的抗氧化性随着阶段性消化而发生改变,但仍然可以作为一种较好的自由基稳定剂、金属螯舍荆和人体健康促进剂应用于食品体系.     

大米蛋白体外消化产物抗氧化活性的研究

为了研究大米清蛋白、球蛋白、醇溶蛋白和谷蛋白体外消化产物的抗氧化活性,用Osborne法从大米粉中提取大米四种蛋白。采用胃-胰蛋白酶分步酶解,选择DPPH·,ABTS+·,·OH自由基清除能力和Fe2+金属离子螯合能力四个指标对消化产物的抗氧化活性进行综合评价。与市售的大豆肽比较,大米四种蛋白经模拟体外消化后具有良好的抗氧化活性。其中醇溶蛋白的消化产物抗氧化活性最好,DPPH·,ABTS+·,·OH自由基清除能力和Fe2+金属离子螯合能力的半抑制浓度分别为30.88 mg/m L、27.61 mg/m L、5.43mg/m L、0.18 mg/m L。大米四种蛋白酶解产物的Fe2+螯合能力半抑制浓度均小于1 mg/m L,具有良好的Fe2+螯合能力。研究结果表明大米四种蛋白的体外消化酶解物具有不同大小的抗氧化活性,分子量集中在181~1000 Da范围内,是一种易于被人体吸收的抗氧化肽。     

酪蛋白抗氧化肽的胃肠消化稳定性研究

目的:研究酪蛋白抗氧化肽的活性在模拟胃肠消化过程中的稳定性。方法:采用脱脂乳粉为原料提取酪蛋白,经酶解,初步分离得到酪蛋白抗氧化肽。以氧自由基清除能力(ORAC)和2,2′-联氮-双-(3-乙基苯并噻错啉-6-磺酸)(ABTS)自由基清除率为抗氧化指标,采取单因素试验,体外模拟胃肠消化模型研究酪蛋白抗氧化肽的胃肠消化稳定性。结果:酪蛋白抗氧化肽经胃蛋白酶消化后其抗氧化活性显著降低,而在随后的模拟肠消化中抗氧化活性逐渐回升至消化前的水平。在模拟胃消化阶段,胃液pH对于酪蛋白抗氧化肽的抗氧化活性没有显著影响,酶与底物比(E/S)越小,酪蛋白抗氧化肽活性保留得越多;在模拟肠消化阶段,底物浓度越大,其活性恢复得越缓慢。结论:酪蛋白抗氧化肽在模拟胃肠消化过程中的稳定性研究,为日常膳食中生物活性肽的合理搭配提供了理论依据。     

远东拟沙丁鱼抗氧化肽的分离纯化及结构解析

通过动物蛋白酶和风味酶联合水解,采用超滤等膜分离技术制备远东拟沙丁鱼蛋白多肽,得到不同分子质量区间的多肽样品F1(100~3000 u)、F2(3000~10000 u)和F3(大于10000 u)。以DPPH、ABTS和羟基自由基清除能力为检测指标,测定各组分的抗氧化活性,结果显示:组分F1的抗氧化活性最强。进一步对远东拟沙丁鱼蛋白多肽F1进行分离。以ABTS自由基清除能力为筛选指标,采用强阴离子、反向色谱柱YMC-pack-OSD-AQ进行逐级分离收集,筛选出2个具有抗氧化活性较强的肽段(b-f1和b-f6)。采用ESI MS/MS测定其氨基酸结构,结果显示:b-f1的分子质量均为436 u,其氨基酸序列是Arg-Phe-Asp(RFD)或Trp-Thr-Met(WTM);b-f6的分子质量为700 u,其氨基酸序列为Phe-Ala-His-Asp-Asp-Pro。b-f1和b-f6对ABST自由基清除能力分别为(81.22±4.12)%和(76.35±3.32)%。     

铁离子螯合亲和层析分离抗氧化活性核桃肽

采用铁离子螯合亲和层析方法分离出具有不同抗氧化活性的核桃肽,并探讨核桃肽的抗氧化活性与铁结合能力的关系。结果表明,核桃肽在酸性条件(pH 5.5)下与铁的结合能力最强,随着pH逐渐升高,结合能力下降。磷酸氢二钠对吸附到铁亲和层析柱上核桃肽的洗脱效果最好,通过阶段洗脱,得到铁结合能力逐渐增强的核桃肽组分(F1、F2和F3)。对其总还原能力和2,2-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐(ABTS)自由基清除能力进行测定,发现其抗氧化能力为F3>F2>F1(P<0.05)。结果表明,核桃肽的铁结合能力越强,其抗氧化活性越高。     

鲨鱼皮明胶水解肽的制备、分离纯化与抗氧化活性研究

目的:基于鲨鱼皮明胶水解肽的抗氧化活性,制备、分离纯化高活性的抗氧化多肽。方法:分别使用5种商业蛋白酶水解鲨鱼皮明胶,测定其水解产物的DPPH自由基清除能力、ABTS自由基清除活性以及对Fe2+诱导卵黄脂蛋白多不饱和脂肪酸过氧化反应的抑制作用;利用SP-Sephadex C-25阳离子交换色谱、Sephadex G-50凝胶过滤色谱和C18反向高效液相色谱(HPLC)对酸性蛋白酶的水解产物进行分离纯化。结果:酸性蛋白酶水解产物具有最佳的抗氧化活性;利用SP-Sephadex C-25、Sephadex G-50和C18-HPLC对酸性蛋白酶的水解产物进行分离纯化,所得洗脱组分E2具有最强的清除DPPH自由基活性。经过ESI质谱分析,其多肽组分的主要分子质量为1356u。结论:本研究制备并分离纯化得到高活性的抗氧化多肽,为将来的生产应用提供理论依据。     

模拟胃肠消化对牡蛎低聚肽抗氧化活性的影响

以去壳牡蛎肉为原料通过酶解法制备牡蛎低聚肽,并通过体外模拟消化试验,对比消化前后牡蛎低聚肽分子量分布、DPPH自由基清除能力、羟自由基(·OH)清除能力、ABTS自由基清除能力、氧自由基吸收能力(ORAC)变化,探究牡蛎低聚肽经模拟胃、肠道消化后抗氧化活性的变化。试验结果显示,牡蛎低聚肽的相对分子量主要在1 000 Da以下,胃蛋白酶和胰蛋白酶消化后重均分子量下降不超过8.2%;胃蛋白酶和胰蛋白酶消化后,DPPH自由基清除率降低分别不超过7.9%,8.7%;胃蛋白酶和胰蛋白酶消化后,·OH清除率降低分别不超过9.3%,3.8%;胃蛋白酶消化后,ABTS自由基清除率降低9.2%,胰蛋白酶消化后,ABTS自由基清除率提高3.6%;胃蛋白酶和胰蛋白酶消化后,ORAC值分别提高11.5%,1.3%。胃肠消化对牡蛎低聚肽的抗氧化活性评价各指标均无显著性影响(P＞0.05)。说明牡蛎低聚肽具有较好的综合抗氧化活性和稳定性。     

海洋鱼蛋白低聚肽结构和抗氧化活性的体外消化稳定性

本研究通过体外模拟胃肠道消化海洋鱼蛋白低聚肽,运用高效凝胶过滤色谱、紫外全波长扫描、圆二色光谱表征其消化前后结构变化,测定其消化前后DPPH自由基清除率、ABTS自由基清除能力、铁离子还原能力(FRAP)及氧自由基吸收能力(ORAC)的变化,以探究模拟胃肠道消化对海洋鱼蛋白低聚肽结构及抗氧化活性的影响。分子量分布数据揭示了海洋鱼蛋白低聚肽中分子量为150～1000u的组分为其主要组成部分,所占比例最高可达88.39%;紫外全波长扫描、圆二色光谱扫描表明海洋鱼蛋白低聚肽对胃蛋白酶有很强的抗消化稳定性以及对胰蛋白酶有较好的抗消化稳定性。在浓度1～15 mg/mL范围内,海洋鱼蛋白低聚肽的DPPH自由基清除率与其浓度成正相关,最高为67.86%;ABTS自由基清除能力、FRAP值及ORAC值三个抗氧化指标均显示海洋鱼蛋白低聚肽在消化后其抗氧化活性均有一定程度的提高,其中ORAC值在先胃蛋白酶后胰蛋白酶消化后提高最显著(p0.01)。总之海洋鱼蛋白低聚肽的结构和抗氧化活性均具有抗消化稳定性。     

The Role of Malt and Hop Polyphenols in Beer Quality,Flavour and Haze Stability

Pilot‐scale brewing trials of a 12°P pale lager beer were conducted to look at the effect of a modified dose of hop and malt polyphenols on haze, flavour quality, and stability. Results confirmed that malt polyphenols, and particularly hop polyphenols, in the course of wort boiling, improved reducing activity values and the carbonyl content in fresh and stored beers. Hop polyphenols significantly increased reducing activity and decreased the formation of carbonyls (TBA value) in fresh and stored beer. Reduced content of malt polyphenols, combined with the use of hop CO₂ extract, caused an increase in the TBA value in beer. PVPP stabilized beers tended to be lower in reducing activity. Both malt and hop polyphenols affected the intensity of “harsh taste” in fresh beers and a significant influence from PVPP stabilization of beer was not observed. The staling degree of forced‐aged beers depended on the polyphenol content in the brewhouse. Both hop and malt polyphenols had a positive impact on flavour stability. PVPP treatment of beer had a positive effect on the flavour stability of heat‐aged beers. Polyphenols, especially hop polyphenols, slowed down flavour deterioration during the nine month storage period, but the primary effect was seen during the first four months of storage. Storage trials did not show any unambiguous effects for PVPP stabilization on beer flavour stability. Results confirmed the negative impact of malt and hop polyphenols on haze stability, and PVPP stabilization minimized differences in shelf life prediction values between beers prepared with the modified dose of polyphenols.     

The effects of Lactobacillus hilgardii 4785 and Lactobacillus buchneri 40788 on the microbiome,fermentation, and aerobic stability of corn silage ensiled for various times

We evaluated the ability of an inoculant containing a combination of Lactobacillus hilgardii and Lactobacillus buchneri to modify the microbiome and improve the aerobic stability of whole-plant corn silage after various lengths of ensiling. Chopped whole-plant corn at about 33% dry matter (DM) was uninoculated (CTR) or inoculated with L. hilgardii CNCM I-4785 and L. buchneri NCIMB 40788 at 200,000 cfu/g of fresh forage weight each (combined application rate of 400,000 cfu of lactic acid bacteria/g of fresh forage weight; LHLB), L. buchneri NCIMB 40788 at 400,000 cfu/g of fresh forage weight and Pediococcus pentosaceus NCIMB 12455 at 100,000 cfu/g of fresh forage weight, used as a positive control (LB500), L. hilgardii CNCM I-4785 at the application rate used in the LHLB formulation of 200,000 cfu/g of fresh forage weight (LH), or L. buchneri NCIMB 40788 at the application rate used in the LHLB formulation of 200,000 cfu/g of fresh forage weight (LB). Silos were opened after 34 and 99 d of ensiling and analyzed for nutrient composition, fermentation profile, microbiome, and aerobic stability. After 34 d of ensiling, the inoculated silages had greater numbers of culturable lactic acid bacteria, a bacterial community less rich and diverse, greater relative abundance of Lactobacillus, lower relative abundance of Klebsiella, and a greater concentration of propionic acid than uninoculated silages. Inoculation decreased the ratio of lactic acid to acetic acid, except for LB alone. Treatment LHLB resulted in silage with a greater concentration of 1,2-propanediol than LB500 and was the only treatment to have a lower relative abundance of Saccharomycetes compared with uninoculated silage. Treatments LHLB and LB500 improved the aerobic stability compared with CTR, but the individual LH and LB treatments applied at a low dose did not. Whereas LB500 was stable 34 h longer than CTR, LHLB was stable 91 h longer. After 99 d of ensiling, all inoculated silages had markedly greater aerobic stability than uninoculated silage and were stable for more than 360 h. The inoculant containing a combination of L. hilgardii and L. buchneri markedly improved the aerobic stability of corn silage after a relatively short period of ensiling, and such improvements were greater than the ones obtained from inoculation with the combination of L. buchneri and P. pentosaceus. Inoculating with the combination of L. hilgardii and L. buchneri may be helpful to producers that must feed silage shortly after ensiling.     

Effects of pH,Ions, and Thermal Treatments on Physical Stability of Astaxanthin Nanodispersions

In this work, astaxanthin nanodispersions were prepared using selected three component stabilizer system through a solvent-diffusion technique, with the particle size of 98.3 nm. The stability of produced nanodispersions against pH, salts, and heating were then evaluated. The produced nanodispersions exhibited good physical stability under wide ranges of pH (except around isoelectric point), sodium ion concentrations, and relatively high-temperature treatments (up to 60°C). However, formation of large particles was observed in either presence of calcium ions or higher thermal treatments (more than 60°C).     

Temperature during conservation in laboratory silos affects fermentation profile and aerobic stability of corn silage treated with Lactobacillus buchneri,Lactobacillus hilgardii,and their combination

The environment temperature and its effect on the temperature of silage is very important for the fermentation and subsequent quality of a silage. Obligate heterofermentative lactic acid bacteria (LAB) inocula, because of their ability to inhibit yeasts, have been developed to prevent the aerobic deterioration of silages. The temperature during silage conservation may also play an important role in the fermentation profile of silages. This study has evaluated the effect of temperature, during the conservation of whole crop corn silage, untreated or treated with different LAB inocula, on the fermentation profile and on the aerobic stability of the silage. Corn was harvested at 42% dry matter and either not treated (control) or treated with Lactobacillus buchneri NCIMB 40788 (LB) at 300,000 cfu/g fresh matter (FM); Lactobacillus hilgardii CNCM I-4785 at 150,000 cfu/g FM (LH₁₅₀); L. hilgardii CNCM I-4785 at 300,000 cfu/g FM (LH₃₀₀); or LB+LH at 150,000 cfu/g FM each. In an attempt to experimentally simulate temperature fluctuations in the mass or at the periphery of a silage bunker, corn was conserved in laboratory silos at a constant temperature (20 ± 1°C; MASS) or at lower and variable outdoor temperatures (PERIPH; ranging from 0.5 to 19°C), and the silos were opened after 15, 30, and 100 d of conservation. Lactic acid, acetic acid, and ethanol contents increased in all the silages over the conservation period. The lactic acid content was higher (+10%) in the silages kept at a constant temperature than those conserved at the lower and variable outdoor temperatures. The acetic acid was higher in the treated silages than in the control ones conserved at a constant temperature for 100 d. Moreover, 1,2-propanediol was only detected in the treated silages after at least 30 d at a constant temperature, whereas only traces were detected in the LB+LH treatment for the other temperature conditions. The yeast count decreased during conservation at a slower rate in PERIPH than in MASS and on average reached 2.96 and 4.71 log cfu/g for MASS and PERIPH, respectively, after 100 d of conservation. The highest aerobic stability values were observed for LH₃₀₀ (191 h) in the MASS silage after 100 d of conservation, whereas the highest aerobic stability was observed in LB+LH (150 h) in the PERIPH silages. After 7 d of air exposure, a pH higher than 4.5 and a higher yeast than 8.0 log cfu/g were detected in all the silages opened after 15 and 30 d of conservation. A pH value close to that of silo opening was detected in the LB, LH₁₅₀, and LH₃₀₀ silages conserved under MASS conditions after 100 d, whereas LB+LH was the most effective under PERIPH conditions. The temperature and its fluctuation during conservation of silage in laboratory silos influenced the fermentation, which in turn had an effect on the quality of silage and on the extent of the effect of LAB inocula.     

Pigmented flower extracts of plant species from the Geraniaceae and Lamiaceae families as natural food colourants: anthocyanin composition,thermal and oxidative stability

This study determined the anthocyanin profile of pigmented flower extracts from some Geraniaceae and Lamiaceae plant species found in South Africa, and their thermal and oxidative stability to assess their potential food application. Anthocyanins in the Geraniaceae (Pelargonium grandiflorum Willd. and Pelargonium × hortorum L.H. Bailey, Pelargonium zonale hybrid) were 3,5-diglucosides of delphinidin, petunidin, pelargonidin, peonidin and malvidin and acetyl-acylated malvidin, delphinidin and petunidin. The Lamiaceae species (Salvia aurea × dolomitica Bae’s blue, Salvia dolomitica Codd and Plectranthus zuluensis T. Cooke) mainly contained rutinosides of pelargonidin, glucosides of petunidin, pelargonidin and p-coumaric acid- and malonyl-acylated delphinidin and malvidin. Lamiaceae pigments had higher thermal and oxidative stability. This could be due to aromatic malonyl-acylated anthocyanin self-association and strong intermolecular interactions with phenolic acids and derivatives. Flowers from Lamiaceae and Geraniaceae have potential application as natural food colourants, but temperature and oxidising conditions must be considered depending on the particular species being used.     

天然花色苷的采集、测定和筛选

就北京地区一些栽培作物和分布在松山、百花山、灵山及河北省雾灵山丰富的野生植物资源进行春、夏、秋三季的天然花色苷材料野外采集，共得到24科50种植物的含有花色苷样品。对这些样品进行花色苷提取，并且对这些花色苷稳定性做了1年的测定和筛选，发现了5种植物资源(紫甘兰、蜀葵、红叶小檗、翠雀、沙参)花色苷的颜色稳定性较好。     

磷脂含量对煎炸油烟点、耐寒性、氧化稳定性 和煎炸稳定性的影响

通过添加大豆卵磷脂,使大豆油、菜籽油和棕榈油中磷脂含量分别为本底值、10、20、30、40、50 mg/kg,测定不同磷脂含量的3种煎炸油的烟点、耐寒性、氧化诱导时间,同时检测3种煎炸油在170℃下煎炸不同食材过程中的感官品质、酸价、过氧化值和极性组分含量的变化,以评价其煎炸稳定性。结果表明:随着磷脂含量的增加,大豆油、菜籽油、棕榈油烟点呈下降趋势,其中棕榈油烟点下降受磷脂影响最大;耐寒性随着磷脂含量增加整体呈下降趋势;氧化诱导时间随磷脂含量的增加呈波动变化趋势;在本试验范围内,磷脂含量对煎炸油煎炸稳定性影响的规律尚不明显。     

蛋白质、多糖和多酚混合体系稳定性研究

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