宰后冷却工艺对白条鸡肉品质的影响

采用L9(34)正交试验探讨宰后预冷温度、预冷时间、分割车间停留时间对白条鸡肉保水性的影响,采用L9(34)正交试验探讨预冷温度、预冷时间、次氯酸钠加入量对白条鸡胴体表面菌落总数以及大肠菌群的影响。结果表明：通过控制预冷温度、预冷时间及分割车间停留时间,可以提高白条鸡肉的保水性、减少血冰的生成量;通过控制预冷温度、预冷时间及次氯酸钠加入量,可以有效减少白条鸡胴体表面的菌落总数,抑制大肠菌群的生长繁殖。各因素对保水率、失水率的影响程度均为预冷温度＞预冷时间＞分割车间停留时间;提高保水性的最佳工艺条件为预冷温度(15℃,8℃)、预冷时间35min、分割车间停留时间30min;控制失水率的最佳工艺条件为预冷温度(10℃,4℃)、预冷时间30min、分割车间停留时间40min。各因素对感官质量(血冰)的影响程度为预冷温度＞分割车间停留时间＞预冷时间,控制血冰的最佳工艺条件为预冷温度(10℃,4℃)、预冷时间30min、分割车间停留时间25min。各因素对菌落总数、大肠菌群的影响程度为预冷温度＞次氯酸钠加入量＞预冷时间,最佳工艺条件为预冷温度(10℃,4℃)、次氯酸钠加入量80mg/kg、预冷时间30min。     

Performance of a groove-type photobioreactor for hydrogen production by immobilized photosynthetic bacteria

The biofilm technique has been proved to be an effective cell immobilization method for wastewater biodegradation but it has had restricted use in the field of photobiological H₂ production. In the present study, a groove-type photobioreactor was developed and it was shown that a groove structure with large specific surface area was beneficial to cell immobilization and biofilm formation of the photosynthetic bacteria on photobioreactor surface as well as light penetration. A series of experiments was carried out on continuous hydrogen production in the groove-type photobioreactor illuminated by monochromatic LED lights and the performance was investigated. The effects of light wavelength, light intensity, inlet glucose concentration, flow rate and initial substrate pH were studied and the results were compared with those obtained in a flat panel photobioreactor. The experimental results show that the optimum operational conditions for hydrogen production in the groove-type photobioreactor were: inlet glucose concentration 10 g/L, flow rate 60 mL/h, light intensity 6.75 W/m², light wavelength 590 nm and initial substrate pH 7.0. The maximum hydrogen production rate, H₂ yield and light conversion efficiency in the groove-type photobioreactor were 3.816 mmol/m²/h, 0.75 molH₂/molglucose and 3.8%, respectively, which were about 75% higher than those in the flat panel photobioreactor.     

Development of a simple bio-hydrogen production system through dark fermentation by using unique microflora

In order to ensure efficient functioning of hydrogen fermentation systems that use Clostridium as the dominant hydrogen producer, energy-intensive process such as heat pretreatment of inoculum and/or substrate, continuous injection, and control of anaerobic conditions are required. Here, we describe a simple hydrogen fermentation system designed using microflora from leaf-litter cattle-waste compost. Hydrogen and volatile fatty acid production was measured at various hydraulic retention times, and bacterial genera were determined by PCR amplification and sequencing. Although hydrogen fermentation yield was approximately one-third of values reported in previous studies, this system requires no additional treatment and thus may be advantageous in terms of cost and operational control. Interestingly, Clostridium was absent from this system. Instead, Megasphaera elsdenii was the dominant hydrogen-producing bacterium, and lactic acid-producing bacteria (LAB) were prevalent. This study is the first to characterize M. elsdenii as a useful hydrogen producer in hydrogen fermentation systems. These results demonstrate that pretreatment is not necessary for stable hydrogen fermentation using food waste.     

乳酸菌胞外多糖肠道黏附及免疫调节作用研究进展

乳酸菌作为公认的食品级益生菌,在医学、食品科学及人类健康中发挥重要作用。乳酸菌的胞外多糖作为其主要的细胞外分泌物与其相应生物学功能的发挥密切相关。本文旨在从乳酸菌胞外多糖的理化特性和分子结构方面入手探究其调节免疫的机制,并总结乳酸菌胞外多糖在调节胃肠道功能和进入体内后的免疫调节等方面的特性。以期为乳酸菌胞外多糖的研究和应用奠定理论基础。     

磁性纳米材料在食源性致病菌分离中应用的研究进展

食源性致病菌是影响食品安全的主要因素之一。食品中污染的致病菌数量通常较少,加上其基质复杂,常规分析方法常无法直接对致病菌进行高灵敏、高特异的检测。经过生物学修饰和功能化的磁性纳米材料,可特异性地识别食品基质中少量的致病菌,并通过磁场对靶细菌进行快速及高特异性的选择性分离,实现了食品样品中少量致病菌的特异性分离富集,达到了后续分析检测的纯度和数量。本文综述了磁性纳米材料在食源性致病菌分离富集中的研究进展。     

产γ-氨基丁酸乳酸菌的筛选及诱变育种

利用乳酸菌分离培养基从酸菜汁中分离菌株。经过初筛、复筛后得到的菌株Lp-Lw-131有较好的产γ-氨基丁酸(GABA)能力。对菌株进行形态学鉴定和生理生化实验确定该菌为植物乳杆菌,编号为Lp-Lw-131。利用菌株体内的谷氨酸脱羧酶(GAD)将L-谷氨酸钠脱羧转化成GABA,用比色法测定GABA的产量为0.917g/L。以Lp-Lw-131为出发菌株进行紫外线和硫酸二乙酯(DES)诱变,以致死率为标准确定最佳诱变条件为：紫外照射距离30cm,照射时间90s;DES体积分数为25%醇溶液,处理时间20min,诱变后获得一株突变株Lp-Lw-131-34。连续传代10次后遗传性状稳定,平均GABA产量为1.815g/L,是出发菌株的1.979倍。     

柑橘皮渣降解菌的筛选及特性

为有效处理柑橘皮渣,筛选高效降解柑橘皮渣的菌株。本实验从堆肥中分离得到5 株菌株,测定其香精油耐受性,选取两株耐受性较好的菌株测定纤维素酶和果胶酶活力,并进行柑橘皮渣降解实验。结果表明,菌株L207和L702在65 ℃条件下可正常生长,属于耐高温菌株;对柑橘香精油具有较好的耐受能力,其最大耐受体积分数为25.0%;2 株菌株的纤维素酶活力和果胶酶活力分别是对照菌株（Bacillus subtilis L520）的1.31、2.08 倍和12.68、7.30 倍。柑橘皮渣降解实验表明,菌株能快速高效分解纤维素和果胶。16S rDNA基因序列分析鉴定表明菌株L207和L702均属于地衣芽孢杆菌（Bacillus licheniformis）。     

磁场对Q235钢微生物腐蚀行为的影响

采用腐蚀失重法、电化学测量技术和表面分析技术研究硫酸盐还原菌 (SRB) 在外加磁场下对Q235钢的腐蚀行为。结果表明,磁场条件下SRB对Q235钢的腐蚀作用较无磁场条件下减轻,其阻抗值先减小后增大,而无磁场条件下的阻抗值先增大后减小,说明磁场条件下试样表面的生物膜形成滞后。SEM的分析结果显示,磁场条件下Q235钢表面的生物膜均匀致密,并且紧密地黏附在金属表面。清除腐蚀产物后,无磁场条件下的基体表面呈现较多腐蚀孔和腐蚀裂缝,而有磁场条件下的基体表面则相对平整,说明磁场能有效地抑制SRB对Q235钢的腐蚀。     

发酵蔬菜中亚硝酸盐消长规律及调控技术的研究进展

乳酸菌发酵是我国蔬菜加工的传统工艺之一,发酵蔬菜因其独特的风味和丰富的益生菌而深受消费者喜爱。但现代科学研究发现,蔬菜发酵过程中会产生亚硝酸盐积累的问题,不利于消费者健康。本文概述蔬菜发酵过程中亚硝酸盐形成的机理及变化规律,并对降低发酵蔬菜亚硝酸盐含量的研究与应用进行综述。     

婴幼儿辅食中细菌总数及蜡样芽孢杆菌污染情况分析

通过平板菌落计算法和最大近似值（MPN）法检测市售婴儿辅食中细菌总数和蜡样芽孢杆菌污染情况,并对MPN法得到的疑似蜡样芽胞杆菌进行基因间隔序列（ITS）插入性序列分析和形态鉴定。结果表明,101份样品中只有30份样品菌落总数达标,合格率仅为29.7%,部分超标产品的细菌总数达105CFU/g~106CFU/g。市售3种婴幼儿辅食-米粉、奶伴侣和面条中细菌总数及食源性致病菌蜡样芽孢杆菌检出情况不容乐观。