姜黄素光动力对牡蛎脂质氧化水解酶的影响

本文探究了姜黄素光动力对牡蛎脂质氧化水解酶的影响,旨在从酶的角度阐明姜黄素光动力减缓牡蛎脂质氧化水解的机理。通过检测牡蛎内源酶活性,筛选新鲜牡蛎中产脂质氧化水解酶的菌株、利用16S rDNA进行菌种鉴定,结合Illumina MiSeq高通量测序技术对新鲜牡蛎中的产酶菌株进行分析。结果表明:姜黄素光动力能够降低内源性脂肪氧合酶(LOX)、脂肪酶(Lipase)、磷脂酶A₁(PLA₁)、磷脂酶A₂(PLA₂)、磷脂酶D(PLD)的活性;同时获得了1株分泌脂肪酶的菌—假单胞菌(Pseudomonas)、2株分泌磷脂酶C的菌株—肠杆菌(Enterobacteriaceae)和嗜麦芽寡养单胞菌(Stenotrophomonas);且姜黄素光动力能够减少这些菌株的数量(P<0.05),从而减少外源酶的数量。因此,姜黄素光动力可以通过降低牡蛎内源酶活性、减少外源酶数量来减缓牡蛎脂质的氧化水解。     

Construction,stability and photodynamic germicidal efficacy of curcumin nanoemulsion stabilised with Maillard conjugate of Wpi-Rha

Curcumin has excellent antioxidant and antibacterial properties. The poor solubility and easy degradation limit its application. The present investigation was aimed to prepare curcumin nanoemulsions (Cur-Ne), employing homogeneous and ultrasonication for the encapsulation of curcumin to overcome these problems. Cur-Ne stabilised using whey protein isolate and rhamnose conjugate (Wpi-Rha) was prepared by Maillard reaction. Furthermore, the processing (i.e. ionic strength, heat and freeze-thaw) and storage stability of Cur-Ne were evaluated. Moreover, the bactericidal capacity of Cur-Ne combined with photodynamic therapy (PDT) technology was estimated. Cur-Ne was prepared successfully with the droplet size of 185.97 ± 6.65 nm, polydispersity index (PDI) of 0.21 ± 0.01, zeta potential of −35.17 ± 0.15mV and entrapment efficiency of 97.0 ± 0.07%. Meanwhile, Cur-Ne was stable at different storage and processing conditions. In addition, the DPPH and ABTS radical scavenging rates of Cur-Ne were 84.86 ± 0.24% and 99.63 ± 0.48%, respectively. At the adding amount of 5 μL of Cur-Ne, the Cur-Ne could deactivate the Escherichia coli and Staphylococcus aureus with the antibacterial rate of 99.05 ± 0.13% and 99.11 ± 0.18%, respectively. Curcumin loaded in nanoemulsion and combined with PDT provide new ideas for food storage and sterilisation.     

不同酶水解对鸡蛋清蛋白降解和潜在致敏性的影响

酶水解是降低食物过敏原致敏性的一种常用手段,本文分别利用胃蛋白酶、木瓜蛋白酶、中性蛋白酶和碱性蛋白酶水解鸡蛋清蛋白,通过三羟甲基氨基甘氨酸-十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（Tricine-SDS-PAGE）,并结合水解度（邻苯二甲醛法）分析监测蛋清蛋白的酶解过程,进一步利用制备的兔抗蛋清蛋白多克隆抗体血清和鸡蛋过敏患者血清池评估酶解产物的抗原性和致敏性。结果表明:木瓜蛋白酶和碱性蛋白酶能够有效的水解蛋清蛋白,并且所得酶解产物的抗原性和致敏性较低,其中,木瓜蛋白酶水解蛋清蛋白后产物的抗原性降低了59.23%,致敏性降低了4.91%;碱性蛋白酶水解蛋清蛋白后产物的抗原性降低了57.61%,致敏性降低了4.55%。因此,木瓜蛋白酶和碱性蛋白酶对鸡蛋清蛋白降解及致敏性降低方面均有显著影响。      

复合酶降解高温蒸煮玉米秸秆研究

利用复合酶在其最优条件下降解高温蒸煮玉米秸秆,确定复合酶降解最优条件:0.8g底物(蒸煮秸秆0.6144g)加入30mlpH4.8柠檬酸缓冲液,调pH4.8,121℃灭菌20min,待冷却,无菌操作下加入20mg纤维素酶、10mg木聚糖酶、6mgβ–葡聚糖酶、1.3mg果胶酶,在50℃、100r/min条件下酶解16h,降解率为70.03%。此法降解率已非常接近玉米秸秆理论降解率(约74%),对玉米秸秆降解研究具有一定参考价值。     

The influence of proteolytic and cytolytic enzymes on starch degradation during mashing

The objective of this research was to investigate the impact of proteolysis and cytolysis on starch degradation over the course of the mashing process. A proteolytic enzyme (Neutrase 0.8L, Novozymes) and a number of cytolytic enzymes (barley β‐glucanase from Megazyme, Shearzyme 500L and Ultraflo Max from Novozymes) were used to test their efficiency on starch degradation during mashing. The proteolytic and cytolytic enzymes had positive effects on the levels of starch‐degrading enzymes and starch solubilization during mashing, resulting in higher levels of wort sugar compared with the control, indicating that proteins and residual non‐starchy polysaccharides limited the digestibility of starch during mashing. Moreover, the proteolytic enzyme showed a significantly greater improvement than the cytolytic enzymes, yielding a 57% increase in β‐amylase, a 173% increase in limit dextrinase, rapid starch solubilization during mashing and a higher percentage of fermentable sugars in resultant wort. The increases in limit dextrinase and β‐amylase promoted by the protease suggest that sufficient proteinaceous inhibitor existed in the wort during mashing to inhibit their activities, leading to the unavailability of β‐amylase and especially limiting dextrinase. Furthermore, Ultraflo Max, which contained a β‐glucanase–xylanase mixture, showed a greater improvement than either the individual β‐glucanase or the xylanase on starch hydrolysis. These findings suggest that β‐glucanase is the major enzyme responsible for the degradation of cell walls, and that the complete hydrolysis of the residual cell walls depends on the synergistic effect of β‐glucanase and xylanase. The results suggest that brewers should adjust the degradation of the cell walls and correct the degree of protein modification in order to obtain the desired wort composition. Copyright © 2014 The Institute of Brewing & Distilling     

高温处理对牛肉蛋白质组分及其降解的影响

以不同高温处理(110,115,121℃分别加热3,6,9,12,15min)的牛背最长肌为研究对象,分析其不同溶解性和不同结构蛋白质的含量,总氮、非蛋白氮、氨基态氮的含量,蛋白质水解指数以及全肌肉蛋白十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)的变化规律。结果表明:水溶性蛋白和盐溶性蛋白均随加热温度的升高和时间的延长而急剧下降,121℃加热15 min后,牛背最长肌中肌浆蛋白含量下降了86.9%,肌原纤维蛋白含量下降了89.88%。总氮和氨基态氮含量均呈先升高后降低的趋势,加热时间对非蛋白氮和蛋白水解指数影响显著(P0.05),200kDa的肌球蛋白重链电泳条带随着加热时间的延长逐渐变淡消失,而44.3kDa的肌动蛋白在整个高温处理过程中均无明显的变化。     

黄曲霉毒素的检测及其降解方法进展

黄曲霉毒素主要是由真菌寄生曲霉和黄曲霉产生的次生代谢产物,具有极强的毒性、致癌性,在自然界中普遍存在。文中论述了不同物质中黄曲霉毒素的检测方法及应用,同时介绍了黄曲霉毒素的降解方法及成果,并对黄曲霉毒素检测及降解技术的发展趋势进行了展望。     

不同菌种发酵对辣木叶蛋白降解的影响

以辣木叶粉为原料,研究自然发酵和7株不同菌株接种发酵过程中理化指标（pH、总酸、蛋白酶活力、蛋白含量、氨基酸态氮含量）的变化规律,并采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）筛选降解辣木叶蛋白的优良菌株。结果表明,发酵过程中pH值随发酵时间延长而降低,总酸含量逐渐上升,蛋白酶活力呈先上升后下降趋势。7株不同菌株中,纳豆芽孢杆菌（Bacillus natto）和棉籽糖乳球菌（Lactococcus raffinolactis）发酵的辣木叶粉在24 h时蛋白酶活力最高,分别为270.58 U/mL和248.34 U/mL,发酵结束时,蛋白含量分别下降20.24 mg/g、21.95 mg/g,氨基酸态氮含量明显高于其他组。SDS-PAGE结果显示,纳豆芽孢杆菌和棉籽糖乳球菌能够降解分子质量70 kDa和35 kDa的两种主要蛋白。因此该研究选出纳豆芽孢杆菌和棉籽糖乳球菌作为发酵降解辣木蛋白的优良菌株。     

Enzymic and in sacco methods to estimate rumen degradation of food protein in cattle

BACKGROUND: Two factorial studies compared enzymic and in sacco methods to estimate degradation of ruminant foods. Enzyme degradation (in vitro = enzyme) was determined from the release of leucine‐equivalent amino acid (LA) crude protein (CP) from sunflower meal (SF), maize gluten meal (MG), distillers' dark grain (DG) and field beans (FB) after their separate incubations with Streptomyces griseus enzyme for 0–24 h. In sacco crude protein (CP) degradation of these foods was estimated during washing (0 h) and rumen incubations in fistulated cows for 2–24 h. The LA data were expressed as g LA per either kg of CP (LACP) or acid‐hydrolysable LA (HLA) of each food and compared with in sacco data. RESULTS: These methods showed comparable degradation with time (P < 0.01). The in sacco and HLA were greater than LACP for all foods except MG where in sacco value was either lower or equal to LACP depending upon the incubation time (P > 0.05 or P < 0.05). Conversely, HLA was significantly (P < 0.01) greater than LACP from 2 h onwards. At 0 h, in sacco values were significantly greater than those of enzyme for SF, DG and FB (P < 0.05) but not for MG. The foods differed significantly for degradation constants (a, b, c) in each method (P < 0.05). CONCLUSIONS: Despite variations between in sacco and enzyme estimates for different foods, the relationships between these estimates suggest that the HLA enzyme method has the potential to estimate food degradation. Copyright © 2007 Society of Chemical Industry     

牡蛎超高压脱壳效果的研究

以脱壳效果和得肉率为评价指标研究了牡蛎超高压脱壳工艺参数,并以牡蛎肉的持水率、pH、质构特性、感官特性、菌落总数和大肠杆菌数为指标评价了超高压脱壳对牡蛎肉品质的影响。结果表明,牡蛎超高压脱壳的最佳条件为压力300MPa、保压时间1min。与手工脱壳、热烫脱壳相比,超高压脱壳处理能改善牡蛎肉的持水性,而对pH、感官品质无显著影响。此外,超高压脱壳同时能部分杀灭微生物,使牡蛎肉达到生食水产品卫生标准。牡蛎超高压脱壳总体效果优于手工脱壳和热烫脱壳,是一种较为理想的脱壳技术。      

Inhibitory effect and mechanism of curcumin-based photodynamic inactivation on patulin secretion by Penicillium expansum

Patulin (PAT) contamination caused by Penicillium expansum growth in postharvest fruit brings safety problems. This study investigated the inhibitory effect and mechanism of curcumin (CUR)-based photodynamic inactivation (PDI) on PAT secreted by P. expansum in vitro using a multifunctional light source instrument. After being treated with photosensitive CUR, the growth of mycelium was completely inhibited on potato dextrose agar medium, and the maximum PAT reduction of 93.06% can be achieved (330.0 J/cm², 300 μM CUR) in liquid medium. The inherent mechanism was that PDI causes the reactive oxygen species accumulation in cells, which destroyed the antioxidant defense system and induced severe oxidative damage, resulting in the loss of cell integrity. Furthermore, mycelial apoptosis caused up-regulation of five genes, including PatB, PatE, PatG, PatI, and PatL, but down-regulated ten genes in the PAT biosynthetic pathway. These findings suggest that CUR-based PDI can inhibit fungal infection and toxin secretion.Industrial relevanceThis study found that photosensitized curcumin can significantly inhibit mycelial growth and the secretion of patulin by Penicillium expansum. Curcumin-based photodynamic inactivation has the feasibility of the application on fresh fruits and vegetables, such as apples or oranges, and can avoided excessive waste of resources in picking, transporting, storing, and selling.     

Evaluation of CO2 absorption and desorption rate in oysters (Cassostrea gigas) using the soluble gas stabilisation method

Soluble gas stabilisation (SGS) is a recently proposed method to extend the shelf life of food. However, no studies have determined the amount of carbon dioxide absorbed in food and particularly in oysters. Thus, the aim of this study was to determine CO₂ absorption and desorption rates in oysters during the solubilisation process. Cooked oysters were placed in the apparatus's chamber, CO₂ was injected into the chamber, and the SGS process started at different pressures, temperatures and gas/product (g/p) ratios. CO₂ absorption and desorption rates were obtained from data of CO₂ concentration in the chamber headspace and calculated by mathematical models. The results showed higher absorption rates under higher pressure, higher g/p ratio and lower temperature (0 °C). The concentration of CO₂ dissolved in the oysters was 21008.45 mg CO₂ kg product^?1. On the other hand, lower desorption rates occurred for the lowest pressure (200 kPa) and lowest gas/product ratio (1:1). For CO₂ desorption from oysters, it was observed that 10 min was enough to desorb a large amount of CO₂ under normal atmosphere.     

酶解香蕉茎干中纤维素的研究进展

本文简单介绍了酶解香蕉茎干中纤维素的研究背景, 对酶解纤维素的研究状况作了综述, 对用纤维素酶把香蕉茎干降解成纤维低聚糖的可能性作了分析, 并对纤维低聚糖的分离方法进行了说明, 对纤维低聚糖的应用前景进行了展望。     

降解南瓜纤维素菌株的分离筛选及酶活测定

目的:筛选出能高效降解南瓜纤维素的菌株,以制备南瓜可溶性膳食纤维。方法:从土壤、腐烂的树叶和水果上分离出具有降解南瓜纤维素的菌株,用刚果红染色透明水解圈进行初筛,然后用CMC-Na、滤纸和南瓜渣为碳源测所有菌株及混合菌株的羧甲基纤维素酶活力,最终选出1株酶活力较高菌株进行下一步实验。结果:共分离到能够有效降解纤维素的共有5株细菌和7株真菌,通过测单菌株和混合菌株的酶活力,表明混合菌株的酶活力最大值比单菌株的酶活力最大值要高3倍之多。结论:混合菌株的酶活力比单株菌酶活力值高,发酵培养72h南瓜渣可溶性多糖降解力最强。     

Small heat shock protein degradation could be an indicator of the extent of myofibrillar protein degradation

The objective of the present study was to evaluate the relationship between small heat shock proteins (sHSP) degradation and tenderness development of beef loins at different ultimate pH (pH_u). A total of twelve loins (M. longissimus dorsi) from steers were obtained at 1 day post mortem. Shear force and proteolysis of each loin were analyzed at 1 and 28 days post mortem. The loins at intermediate pH_u (5.8 to 6.0) showed more variation in tenderness compared to the loins at low pH_u (< 5.8), where few samples were still tough (> 10 kgF) at 28 days. The intact sHSP20 was more pronounced (P < 0.05) in the intermediate pH_u loin compared to the low pH_u counterpart. Further, high correlations between the degradation of both sHSP and myofibrillar proteins were observed (e.g. r = 0.94; degraded sHSP27 and degraded desmin). The result of this study suggests that the extent of sHSP degradation could be an indicator of myofibrillar protein degradation and tenderness.     

北部湾海区几种常见牡蛎基础营养及脂肪酸成分比较分析

目的 比较分析北部湾海区常见的熊本牡蛎、香港牡蛎和近江牡蛎鲜品的基础营养成分及脂肪酸组成.方法 以北部湾海区熊本牡蛎、香港牡蛎和近江牡蛎为实验样品,测定其水分、粗蛋白、粗脂肪和灰分的含量,并用气相色谱-质谱联用法(gas chromatography-mass spectrometry,GC-MS)测定脂肪酸组成及含量...     

姜黄素介导的光动力冷杀菌技术在食品中的研究进展

为及时了解国内外对光动力杀菌的研究现状、热点和发展趋势,为相关研究领域的研究者提供参考,本文采用文献计量学方法对Web of Science核心数据库中收录的2002~2022年光动力杀菌相关研究文献进行统计分析。同时,结合可视化分析软件Citespace对不同国家和地区、机构、作者等进行分析,并对光动力杀菌研究的关键词进行聚类分析和突现分析。通过分析可知,在食品领域,光动力灭菌技术的研究方向主要包括光敏剂的选择和改造、光源的选择和优化以及延长食品货架期等;此外,光动力联合其他冷灭菌技术增强灭菌效果也将成为未来光动力在食品领域的一个研究趋势。

     

用于壳聚糖降解的复合酶制剂产生菌的筛选

以壳聚糖为唯一碳源,结合固态培养基发酵培养,从自然界中筛选得到一株产复合酶的菌株,初步鉴定为曲霉属。该菌产复合酶中以壳聚糖酶、纤维素酶和α-淀粉酶为主,它们的酶活分别为2.206、0.790、3.229U/mL。该复合酶降解壳聚糖的最适温度为50℃,最适pH为5.6,最适时间为4h。通过有机溶剂分级沉淀,发现该复合酶降解壳聚糖的最终产物以聚合度为8～16的壳寡糖为主,表明该复合酶在壳寡糖制备方面具有一定的应用价值。