Lactobacillus reuteri-fortified camel milk infant formula: Effects of encapsulation,in vitro digestion,and storage conditions on probiotic cell viability and physicochemical characteristics of infant formula

Lactobacillus reuteri fortified camel milk infant formula (CMIF) was produced. The effect of encapsulation in different matrices (sodium alginate and galacto-oligosaccharides) via spray drying, simulated infant gastrointestinal digestion (SIGID), and storage conditions (temperature and humidity) on the viability of L. reuteri in CMIF and the physicochemical properties of CMIF were evaluated. Compared with free cells, probiotic cell viability was significantly enhanced against SIGID conditions upon encapsulation. However, L. reuteri viability in CMIF decreased after 60 d of storage, predominantly at higher storage humidity and temperature levels. At the end of the storage period, significant changes in the color values were observed in all CMIF, with a reduction in their greenness, an increase in yellowness, and a wide variation in their whiteness. Moreover, pH values and caking behavior of all CMIF stored at higher temperature (40°C) and humidity [water activity (a_w) = 0.52] levels were found to be significantly higher than the samples stored under other conditions. Over 30 d of storage at lower humidity conditions (a_w = 0.11 and 0.33) and room temperature (25°C), no significant increase in CMIF lipid oxidation rates was noted. Fourier-transform infrared spectroscopy analysis showed that, compared with the other storage conditions, CMIF experienced fewer changes in functional groups when stored at a_w = 0.11. Microscopic images showed typical morphological characteristics of milk powder, with round to spherical-shaped particles. Overall, camel milk fortified with encapsulated L. reuteri can be suggested as a promising alternative in infant formula industries, potentially able to maintain its physicochemical characteristics as well as viability of probiotic cells when stored at low humidity levels (a_w = 0.11) and temperature (25°C), over 60 d of storage.     

我国首例由丁酸梭菌引起婴儿E型肉毒中毒实验室诊断研究

目的对一起疑似婴儿肉毒中毒进行实验室诊断研究。方法对1例疑似婴儿肉毒中毒病例的粪便、食用过的食品和生活环境涂抹共计30份标本/样品进行梭菌分离鉴定及肉毒毒素检测,对分离菌株进行产毒试验。结果将患儿粪便标本培养物上清液腹腔注射小鼠后可致小鼠出现典型肉毒毒素中毒表现(竖毛、呼吸困难并出现典型的蜂腰、四肢麻痹),继而死亡,且培养物上清液经胰酶处理后毒性增强,表现为小鼠出现中毒及死亡时间较未处理组明显缩短。但培养物上清液经100℃加热处理后再次染毒动物,小鼠未出现中毒和死亡。混合型肉毒毒素诊断血清及单价抗E型肉毒毒素诊断血清可对小鼠起到保护作用。从患儿的粪便标本中分离到G~+芽胞杆菌,该菌在哥伦比亚血平板上呈不规则半透明扁平菌落,边缘根状生长,并携带E型肉毒毒素产毒基因,16S rRNA将其鉴定为丁酸梭菌,产毒试验结果显示该菌株可产E型肉毒毒素。结论该起婴儿中毒事件是由感染产E型肉毒毒素的丁酸梭菌引起。     

毛细管区带电泳-间接紫外检测法测定婴儿配方奶粉中的胆碱

目的建立毛细管区带电泳-间接紫外检测法测定婴儿配方奶粉中胆碱含量的新方法。方法用5 mmol/L乙酸提取婴儿配方奶粉样品中的胆碱,涡旋混匀、9000 r/min离心,上清液经0.45μm醋酸纤维素滤膜过滤后进样。用未涂覆熔融石英毛细管75μm×70 cm(有效长度:60 cm)作为分离柱。以10 mmol/L磷酸二氢钠+20 mmol/L磷酸+7 mmol/L 4-甲基咪唑为分离缓冲体系。分离电压为28 k V,进样压力及时间为0.5 psi、10 s,检测波长为214 nm。结果胆碱的校正峰面积与质量浓度在8.7~86.8 mg/L范围内间线性关系良好,相关系数为0.9997、检出限为2.6 mg/L、定量限为8.7 mg/L,方法的日内和日间精密度分别为1.9%和3.9%(n=7)。3个质量浓度添加水平的平均加标回收率分别为98.8%、95.2%及97.6%,相应RSD分别为0.8%、0.9%及0.6%(n=5)。用本法分析了10件婴儿配方奶粉样品,均获满意结果。结论本方法简单、无需有机溶剂,适用于婴儿配方奶粉中胆碱的常规检测。     

反式肉桂醛与温和加热结合对复原婴幼儿牛乳中阪崎克罗诺肠杆菌的抑杀作用

研究反式肉桂醛与温和加热结合对复原婴幼儿牛乳中阪崎克罗诺肠杆菌的抑杀作用。将3种阪崎克罗诺肠杆菌的混合菌株(浓度约6.6(lg(CFU/m L)))接种于含有不同质量分数反式肉桂醛(0、0.1%、0.2%、0.3%和0.4%)的复原婴幼儿牛乳样品中,将样品置于25、45、50、55℃培养,并在不同的时间点对样品中存活的阪崎克罗诺肠杆菌涂布计数。为探究反式肉桂醛与温和加热结合的抑杀机制,实验利用LIVE/DEAD?细菌活性检测试剂盒和场发射扫描电子显微镜探究细胞膜完整性及细胞形态。结果表明:0.4%的反式肉桂醛在25℃处理90 min、45℃处理20 min、50℃处理10 min及55℃处理10 min使复原婴幼儿牛乳中阪崎克罗诺肠杆菌总数降低至检出限以下。与反式肉桂醛及温和加热单独作用相比,反式肉桂醛结合温和加热对阪崎克罗诺肠杆菌有显著的抑杀效果(P0.05),并且随温和加热温度的升高及反式肉桂醛质量分数的增加,效果更加明显。温和加热与反式肉桂醛结合会影响细胞膜的通透性并使细胞破碎瓦解。以上结果表明:反式肉桂醛与温和加热结合有潜力在冲调乳粉过程中应用,从而降低阪崎克罗诺肠杆菌的感染风险。     

婴幼儿羊奶粉及米粉中的细菌多样性分析

为探究婴幼儿奶粉和米粉辅食中细菌群落结构,对婴幼儿食品生产质量控制和监管提供理论依据,本研究采用Ion torrent PGM二代高通量测序平台对14个婴幼儿食品样本中细菌16Sr RNA的V4~V5可变区进行了测序分析。测序共获得13805个不同的OTU,隶属于2界、10门、20纲、50目、84科、144属。分析结果表明,婴幼儿羊奶粉样品比米粉样品具有更高的群落多样性,奶粉样品组内差异较米粉样品小。羊奶粉样品中占绝对优势菌群隶属于厚壁菌门(65.58%)和变形菌门(16.01%),在属水平上以链球菌属(24.86%)和乳球菌属(21.44%)为主;而米粉样品中蓝藻菌门(41.79%)占有绝对优势,厚壁菌门(30.99%)和变形菌门(24.48%)次之,推测主要与两种产品的原料不同有关。另外,沙门氏菌(8.75%)、李斯特氏菌(3.61%)等与食源性疾病相关的细菌种类在米粉样品组中普遍存在,经组间差异性分析表明与奶粉样品中相应丰度有统计学差异(p<0.05),提示婴幼儿米粉产品存在潜在的食品安全隐患,其原料和生产加工环节的质量控制亟需引起生产企业和食品监管部门的重视。     

全二维气相色谱-飞行时间质谱测定婴幼儿配方奶粉中的矿物油

目的建立全二维气相色谱-飞行时间质谱(two-dimensional gas chromatography with time of flight mass spectrometry, GC×GC-TOFMS)/氢火焰离子化检测器(flame ionization detector, FID)法测定婴幼儿配方奶粉中矿物油的分析方法。方法样品经过提取皂化、0.3%(质量分数)硝酸银硅胶-分子筛硅藻土混合固相萃取(solidphase extraction,SPE)柱净化处理后,采用全二维气相色谱-飞行时间质谱联用进行检测和分析。结果该法实现了饱和烃类矿物油(mineraloilsaturatedhydrocarbons,MOSH)和芳香烃类矿物油(mineraloilaromatichydrocarbons,MOAH)的在线分离,仪器分析时间仅为34min。MOSH和MOAH的检出限为0.5mg/kg,加标回收率为88.0%～97.2%,相对标准偏差为5.0%～8.3%(n=6)。运用该法对20款配方奶粉进行测定,均未检出MOAH,其中11款检出MOSH,含量为0.5～8.2 mg/kg;奶粉中普遍含有奇数碳的正构烷烃和植物甾醇烯类物质,推断矿物油污染可能来源于油墨和润滑油。结论方法灵敏,进一步提高了定量的准确性,可同时进行定性和定量分析,适合于奶粉中矿物油的检测。样品检测结果表明,婴幼儿配方奶粉中矿物油的污染情况需引起关注。     

Molecular Epidemiology of Enteroaggregative Escherichia coli (EAEC) Isolates of Hospitalized Children from Bolivia Reveal High Heterogeneity and Multidrug-Resistance

Enteroaggregative Escherichia coli (EAEC) is an emerging pathogen frequently associated with acute diarrhea in children and travelers to endemic regions. EAEC was found the most prevalent bacterial diarrheal pathogen from hospitalized Bolivian children less than five years of age with acute diarrhea from 2007 to 2010. Here, we further characterized the epidemiology of EAEC infection, virulence genes, and antimicrobial susceptibility of EAEC isolated from 414 diarrheal and 74 non-diarrheal cases. EAEC isolates were collected and subjected to a PCR-based virulence gene screening of seven virulence genes and a phenotypic resistance test to nine different antimicrobials. Our results showed that atypical EAEC (a-EAEC, AggR-negative) was significantly associated with diarrhea (OR, 1.62, 95% CI, 1.25 to 2.09, p < 0.001) in contrast to typical EAEC (t-EAEC, AggR-positive). EAEC infection was most prevalent among children between 7–12 months of age. The number of cases exhibited a biannual cycle with a major peak during the transition from warm to cold (April–June). Both typical and a-EAEC infections were graded as equally severe; however, t-EAEC harbored more virulence genes. aap, irp2 and pic were the most prevalent genes. Surprisingly, we detected 60% and 52.6% of multidrug resistance (MDR) EAEC among diarrheal and non-diarrheal cases. Resistance to ampicillin, sulfonamides, and tetracyclines was most common, being the corresponding antibiotics, the ones that are frequently used in Bolivia. Our work is the first study that provides comprehensive information on the high heterogenicity of virulence genes in t-EAEC and a- EAEC and the large prevalence of MDR EAEC in Bolivia.     

水提法提取—电感耦合等离子体质谱法测定婴幼儿配方奶粉中的碘

用水提取婴幼儿奶粉中的碘,亚铁氰化钾和乙酸锌盐析法沉淀蛋白,过滤后可以得到澄清处理液。用电感耦合等离子体质谱对提取样液进行测定,130Te作为内标物进行定量分析。该方法简便快捷,检出限为0.10 mg/kg加标回收率为90.8%~109%,相关系数0.999,精密度试验RSD2%。     

婴幼儿配方奶粉中氯丙醇脂肪酸酯的检测方法优化与污染暴露

目的:采用气相色谱-质谱(gas chromatography-mass spectrometry,GC-MS)联用技术,建立同时测定婴幼儿配方奶粉中3-氯-1,2-丙二醇脂肪酸酯(3-monochloropropane-1,2-diol ester,3-MCPDE)、2-氯-l,3-丙二醇脂肪酸酯(2-monochloropropane-1,3-diol ester,2-MCPDE)、1,3-二氯-2-丙醇脂肪酸酯(1,3-dichloropropane-2-ol ester,1,3-DCPE)和2,3-二氯-1-丙醇脂肪酸酯(2,3-dichloropropane-1-olester,2,3-DCPE)含量的分析方法,并对市售50份婴幼儿配方奶粉中4种氯丙醇脂肪酸酯的污染水平进行调查分析和风险暴露评估。方法:婴幼儿配方奶粉经脂肪提取后,依次通过碱水解、硅藻土固相萃取小柱净化、七氟丁酰基咪唑衍生上机,同位素内标法定量。结果:该方法在20～600 ng/mL范围内线性良好(r~2≥0.998 9),检出限为0.005 mg/kg,定量限为0.015 mg/kg,检出限和定量限均以相应的氯丙醇计。0.03、0.075 mg/kg和0.15 mg/kg水平下的加标回收率在82.2%～113.9%之间,相对标准偏差均不大于8.3%。50份奶粉样品中,3-MCPDE检出率为100.0%,含量为0.037～0.208 mg/kg,2-MCPDE检出率为42.0%,含量为ND～0.060 mg/kg,1,3-DCPE和2,3-DCPE均未检出。统计不同月龄婴幼儿氯丙醇脂肪酸酯的平均暴露量,0～6月龄为3.86μg/kg、6～12月龄为2.00μg/kg、12～36月龄为1.07μg/kg。结论:该方法操作简便、准确可靠,适合婴幼儿配方奶粉中4种氯丙醇脂肪酸酯的同时测定。婴幼儿摄入氯丙醇脂肪酸酯的健康风险需引起关注。     

评定高效液相色谱法测定婴幼儿配方乳粉中乳铁蛋白含量的不确定度

目的 对高效液相色谱法测定婴幼儿配方乳粉中乳铁蛋白含量的不确定度进行分析。方法 通过对实验过程中所用标准物质、样品处理过程、测量重复性以及回收率4个方面进行不确定度分析, 建立了不确定度的模型, 计算合成不确定度、扩展不确定度。结果 当乳铁蛋白的含量为64.9 mg/100 g时, 高效液相色谱法测定婴幼儿乳粉中乳铁蛋白含量的合成不确定度为0.023, 扩展不确定度为1.5 mg/100 g, 乳粉中乳铁蛋白含量的测定结果为(64.9±1.5) mg/100 g, (k=2, P=95%)。结论 本次评定揭示了该检测方法对结果影响最大的因素是标准溶液及工作液的制备过程, 因此在此过程中应严格按规范进行操作, 从而使检测结果更加准确可靠。