Fatty acids,volatile compounds and microbial quality preservation with an oregano nanoemulsion to extend the shelf life of hake (Merluccius hubbsi) burgers

Hake (Merluccius hubbsi) is the most important fish of Argentinean industry. The preservative effects of an oregano essential oil (EO) nanoemulsion (NE) on hake burgers (FB) during 15 days at 4 °C were studied. Fatty acids determined by gas chromatography coupled with mass spectrometry (CG-MS), volatile compounds determined by solid phase microextraction (SPME) coupled with CG-MS, total volatile basic nitrogen (TVBN), and microbial count was measured. ANOVA and DCG tests were performed. After 14 days, significant differences were detected among samples (P ≤ 0.05). FB with EO (EO-FB) and FB with NE containing EO (NEEO-FB) had the highest content of EPA (eicosapentaenoic acid) (191.82 and 198.42 g kg⁻¹) and DHA (docosahexaenoic acid) (107.97 and 110.87 g kg⁻¹, respectively). Also, NEEO-FB had the lowest microbial count (7 log CFU g⁻¹). The incorporation of the oregano essential oil into a nanoemulsion improves the preserving activity in hake fish burgers.     

页岩储层保护用O/W纳米乳液的制备

针对钻井液滤液侵入页岩储层极易导致严重的水敏损害及液相圈闭损害问题,采用两步稀释法研备出粒径极小、分散性好且长期稳定的页岩储层保护用水包油(O/W)纳米乳液。选取Gemini季铵盐型表面活性剂GTN、Tween80与正丁醇三者复配作为表面活性剂组分(记为S+A),通过室内实验研究了水相中NaCl质量分数对NaCl溶液/(S+A)/正辛烷体系微乳液特性的影响,考察了微乳液相转变温度(PIT)、制备方法及其微观构型等因素对采用两步稀释法制备的纳米乳液粒径的影响,同时对纳米乳液体系的失稳机理进行研究。结果表明,NaCl溶液/(S+A)/正辛烷体系微乳液中NaCl的加入可以显著提高表面活性剂组分的乳化效率,改变微乳液微观构型,使PIT显著降低;当剂油体积比(R_os)为7:3时,通过调节双连续微乳液的PIT接近实验乳化温度,采用两步稀释法制备的O/W纳米乳液粒径最小且分布范围最窄;NaCl溶液/(S+A)/正辛烷体系纳米乳液主要失稳机理为奥氏熟化;纳米乳液具有良好的储层保护作用。     

酪蛋白酸钠稳定的海藻油纳米乳液制备及表征

本文研究了酪蛋白酸钠稳定的平均粒径小于100 nm的海藻油乳液(O/W)的一般性质及环境因素对其稳定性的影响。采用微射流高压均质结合溶剂(乙酸乙酯)辅助蒸发法制备了海藻油含量1%的乳液(EAE-nano),用微射流高压均质法制备海藻油含量10%的乳液(AE-nano)作为对照。将AE-nano稀释10倍后与EAE-nano对比观察,AE-nano为乳白色,而EAE-nano呈半透明状。用动态光散射技术研究了EAE-nano的一般性质;以及加入0~500 mmol/L的Na Cl、在3.0~7.0的范围调节p H值、用沸水加热处理等环境因素对乳液物理稳定性的影响。在p H为7.0时,EAE-nano的平均粒径为76.8±0.5 nm,AE-nano的平均粒径为180.9±2.1 nm;EAE-nano比AE-nano对于Na Cl、p H值的变化、加热处理等环境压力有更好物理稳定性。用微射流高压均质结合溶剂辅助蒸发法制备的酪蛋白酸钠稳定的食品级乳液,在饮料的生产和疏水性生物活性物质的包封等应用方面显示出很高的潜在应用价值。     

深海鱼油纳米乳制备方法研究

研究了深海鱼油纳米乳的制备方法,并对制备的纳米乳的理化性质进行了分析。以深海鱼油为油相,采用表面活性剂复配法从Span-20、Span-80、Tween-20、Tween-80中筛选合适的乳化剂。结果表明:以Span-80和Tween-80体积比为19∶81的混合液作为乳化剂,以无水乙醇为助表面活性剂;当V(混合表面活性剂)∶V(深海鱼油)∶V(蒸馏水)=8∶2∶20时,所制备纳米乳为O/W型,其表观澄清透明,粒径范围在725 nm之间,多分散系数(PDI)范围在0.150.25之间。用三相图表示纳米乳的成乳范围。稳定性试验表明所制备的纳米乳离心后能保持稳定,但对高温不耐受,需25℃以下保存。     

柠檬酸银纳米乳液的合成与表征

为了制备纳米层级有机酸银乳液，并考察其在制备纳米导电银膜方面的应用，在聚乙烯吡咯烷酮（PVP）存在的条件下，于水中通过硝酸银与柠檬酸钠反应，合成了柠檬酸银纳米乳液。将柠檬酸银纳米乳液涂布在PET片基上，并用抗坏血酸（Vc）水溶液对其进行还原，制备了纳米导电银膜。通过红外光谱仪、热分析仪、X射线衍射仪、激光粒度仪、紫外．可见光分光光度计、扫描电镜（SEM）等，对柠檬酸银纳米乳液，以及导电银膜性能进行了测试和表征。发现PVP保护的柠檬酸银乳液，粒度分布均匀。SEM观察表明，柠檬酸银呈长径比为5：1的棒状生长，直径约为20nm。银膜的UV-Vis吸收峰位于430nm，表明其具有纳米结构，表面电阻为2.42kΩ/cm。     

A Systematic Review on Nanoencapsulation Natural Antimicrobials in Foods: In Vitro versus In Situ Evaluation,Mechanisms of Action and Implications on Physical-Chemical Quality

Natural antimicrobials (NA) have stood out in the last decade due to the growing demand for reducing chemical preservatives in food. Once solubility, stability, and changes in sensory attributes could limit their applications in foods, several studies were published suggesting micro-/nanoencapsulation to overcome such challenges. Thus, for our systematic review the Science Direct, Web of Science, Scopus, and Pub Med databases were chosen to recover papers published from 2010 to 2020. After reviewing all titles/abstracts and keywords for the full-text papers, key data were extracted and synthesized. The systematic review proposed to compare the antimicrobial efficacy between nanoencapsulated NA (nNA) and its free form in vitro and in situ studies, since although in vitro studies are often used in studies, they present characteristics and properties that are different from those found in foods; providing a comprehensive understanding of primary mechanisms of action of the nNA in foods; and analyzing the effects on quality parameters of foods. Essential oils and nanoemulsions (10.9–100 nm) have received significant attention and showed higher antimicrobial efficacy without sensory impairments compared to free NA. Regarding nNA mechanisms: (i) nanoencapsulation provides a slow-prolonged release to promote antimicrobial action over time, and (ii) prevents interactions with food constituents that in turn impair antimicrobial action. Besides in vitro antifungal and antibacterial, nNA also demonstrated antioxidant activity—potential to shelf life extension in food. However, of the studies involving nanoencapsulated natural antimicrobials used in this review, little attention was placed on proximate composition, sensory, and rheological evaluation. We encourage further in situ studies once data differ from in vitro assay, suggesting food matrix greatly influences NA mechanisms.     

南极磷虾油灵芝孢子油纳米乳复合物提高小鼠的免疫功能

本文研究了乳化溶剂蒸发法制备的南极磷虾油与灵芝孢子油纳米乳复合物对小鼠免疫功能的作用效果。将350只健康雌性小鼠随机分为5批(N=70),每批随机分为7组(n=10),阴性对照组、纳米乳复合物与非纳米乳复合物低(0.25 g/kg·bw)、中(0.50g/kg·bw)、高(1.50g/kg·bw)剂量组,分别相当于人体推荐摄入量的5、10、30倍。经口灌胃30d,每日1次。检测受试物对小鼠各项免疫指标的影响。结果表明,与阴性对照组相比,纳米乳复合物低、中剂量组提高小鼠脾淋巴细胞转化能力分别为35.72%(p0.05)、157.13%(p0.01),高剂量组增强小鼠迟发性变态反应效果为32.41%(p0.05);中剂量组促进小鼠抗体生成细胞增殖效果为21.12%(p0.05),低、中、高剂量增强小鼠产生血清溶血素的效果依次为:63.22%(p0.01)、77.64%(p0.01)、55.31%(p0.01);中、高剂量组增强小鼠NK细胞的活性效果分别为58.92%(p0.01)和134.83%(p0.01),且经纳米乳化后效果优于单纯的复合物。南极磷虾油与灵芝孢子油纳米乳复合物对小鼠具有提高免疫力的作用。     

柑橘精油纳米乳的制备及对金黄色葡萄球菌的抑制活性研究

以抑菌圈直径试验筛选出的对金黄色葡萄球菌抑制效果较好的3种柑橘(佛手柑、甜橙、蜜柚)精油为油相,以吐温80为乳化剂,去离子水为水相,通过相转变法制备纳米乳。结果表明,3种柑橘精油纳米乳的配方:精油质量分数为6%、吐温80质量分数为24%、去离子水质量分数为70%,此条件下制备的纳米乳平均粒径为10~20 nm,粒径分布较均匀。抑菌圈直径试验和最小抑菌浓度试验表明,将3种柑橘精油制备成纳米乳,其抑菌活性均得到提升,其中佛手柑精油纳米乳表现出最强的抑制金黄色葡萄球菌效果,最小抑菌浓度和最小杀菌浓度均为3.75 mg/mL,抑菌活性为纯精油的2.5倍。扫描电镜结果显示,相对于纯精油,佛手柑精油纳米乳对菌体结构的破坏更显著,说明佛手柑精油纳米乳对食源性病菌金黄色葡萄球菌具有良好的抑制作用。     

Optimization of β-casein stabilized nanoemulsions using experimental mixture design

The objective of this study was to determine the effect of changing viscosity and glass transition temperature in the continuous phase of nanoemulsion systems on subsequent stability. Formulations comprising of β-casein (2.5%, 5%, 7.5%, and 10% w/w), lactose (0% to 20% w/w), and trehalose (0% to 20% w/w) were generated from Design of Experiments (DOE) software and tested for glass transition temperature and onset of ice-melting temperature in maximally freeze-concentrated state (T(g) ' & T(m) '), and viscosity (μ). Increasing β-casein content resulted in significant (P < 0.0001) increases in viscosity and T(m) ' (P= 0.0003), and significant (P < 0.0001) decreases in T(g) '. A mixture design was used to predict the optimum levels of lactose and trehalose required to attain the minimum and maximum T(g) ' and viscosity in solution at fixed protein contents. These mixtures were used to form the continuous phase of β-casein stabilized nanoemulsions (10% w/w sunflower oil) prepared by microfluidization at 70 MPa. Nanoemulsions were analyzed for T(g) ' & T(m) ', as well as viscosity, mean particle size, and stability. Increasing levels of β-casein (2.5% to 10% w/w) resulted in a significant (P < 0.0001) increase in viscosity (5 to 156 mPa.s), significant increase in particle size (P= 0.0115) from 186 to 199 nm, and significant decrease (P= 0.0001) in T(g) ' (-45 to -50 °C). Increasing the protein content resulted in a significant (P < 0.0001) increase in nanoemulsion stability. A mixture DOE was successfully used to predict glass transition and rheological properties for development of a continuous phase for use in nanoemulsions.