应用激光共聚焦显微镜观察光动力技术对单增李斯特菌菌膜的灭活作用

以亚甲基蓝(methylene blue,MB)为光敏剂,采用光催化专用氙灯光源(光功率密度为200mW/cm2),通过激光共聚焦扫描显微镜(confocal laser scanning microscope,CLSM)观察法探讨了光动力杀菌技术(anti-microbial photodynamic technology,APDT)对单增李斯特菌(Listeria monocytogenes,LM)菌膜(biofiLM,BF)的灭活作用。结果表明,MB-APDT处理的LM BF经过SYTO9/PI染色后在CLSM下观察,灭活效果区分明显。这一效果由平板菌落计数法得到进一步证实。光照20min,当MB的浓度低至0.1μg/mL时,APDT对于生长8h的BF失活率达到99.7%;当MB浓度为50μg/mL时,几乎全部LM BF失活。当MB浓度为1μg/mL时,光照5min即可使约99.6%生长8h的LM BF失活,也可使约78.7%生长36h的BF失活;当光照时间为30min时,生长8h LM-BF失活率达到99.97%,而生长36h BF失活率也达到99.94%。MB-APDT对LM BF的灭活效果主要取决于MB浓度和光照时间,且杀伤作用非常显著。     

姜黄素介导的光动力技术对鲜切马铃薯的杀菌效果

本文运用光动力技术（Photodynamic technology,PDT）对鲜切马铃薯进行非热杀菌,实验选用姜黄素为光敏剂,420 nm LED蓝光为激发光源。探究了光照功率、光照时间、孵育时间以及光敏剂浓度等因素对鲜切马铃薯表面大肠杆菌、金黄色葡萄球菌杀菌效果的影响,并确定最优杀菌条件。结果表明,该技术对大肠杆菌的最优杀菌条件分别为:光照功率40 W、光照时间20 min、孵育时间15 min、姜黄素浓度30 μmol/L;金黄色葡萄球菌的最佳杀菌条件分别为:光照功率40 W、光照时间10 min、孵育时间15 min、姜素浓度30 μmol/L。与对照组相比,光动力技术处理后的大肠杆菌与金黄色葡萄球菌菌落总数分别为降低3.60与5.23 lg CFU/mL。     

贮藏条件对从江红曲孢子活力的影响

以孢子萌发率为评价指标,研究光照、贮藏温度、氧化还原电位、金属离子及低浓度乳酸对从江红曲孢子活力的影响。结果表明:2℃低温贮藏、黑暗、添加400μg/mL的Vc、添加1%的乳酸均有利于从江红曲霉孢子活力的保持,其中添加400μg/mL Vc的活性最高,孢子萌发率达74.22%;强光、紫外线、0.1%H_2O_2处理下,从江红曲孢子萌发率均显著降低。     

植物乳杆菌CGMCC 1.103对米曲霉沪酿3.042孢子生长的影响研究

由于植物乳杆菌CGMCC1.103对寄牛曲霉及黄曲霉产生黄曲霉毒素B1有抑制作用,通过将植物乳杆菌CGMCC1.103与米曲霉沪酿3.042混合接种后的孢子活菌计数与酶活的变化来探讨植物乳杆菌CGMCC 1.103对米曲霉沪酿3.042孢子生长的影响,研究将2种菌混合发酵生产豆瓣以控制其黄曲霉毒素B1含量的可行性.     

用米浆水培养酱油酿造用曲霉菌的研究

文章考察了用米浆水替代制曲配料用水来制备酱油生产用米曲霉、黑曲霉及红曲霉的制曲效果。以麸皮、豆粕为原料,以1∶0.8的比例添加不同pH值的米浆水配料,选用AS 3.042米曲霉、AS 3.350黑曲霉、AS 3.972红曲霉为菌种,在33℃条件下恒温制曲。结果表明:对于米曲霉和黑曲霉,用浸米时间为24～72h的米浆水配料,均可以获得与对照组相当的成曲的蛋白酶活、糖化酶活和孢子数;而对于红曲霉,米浆水对提高成曲的酶活力、孢子数无显著贡献。     

生孢梭菌孢子生长与失活模型的统一化研究

为探讨预测微生物生长和失活的预测模型统一化问题,研究将生孢梭菌孢子热失活“镜像化”曲线用描述微生物生长的Gompertz 模型和Baranyi 模型进行模拟,并通过标准预测误对两种模型进行比较。实验表明：两种模型都能较好的模拟生孢梭菌孢子热失活,但t 检验分析差异不显著,标准预测误比较表明Gompertz 模型优于Baranyi 模型。建议用Gompertz 模型统一描述生孢梭菌孢子生长和失活情况。     

纳他霉素水溶液生物稳定性研究

为更好地在食品中应用纳他霉素,研究温度、光照、pH 值和无机盐对纳他霉素水溶液生物稳定性的影响。结果表明：在不超过100℃时,纳他霉素水溶液具有较强的生物稳定性,但经121℃处理,生物稳定性显著降低,在121℃条件下热处理15min 后,抑菌活性残留率为62.15%,处理30min 后完全失活。纳他霉素水溶液对紫外照射非常敏感,90min 后完全失活;对日光灯照射比较敏感,10d 后完全失活。在pH4～8 之间,纳他霉素水溶液比较稳定。NaCl、MgSO4 和CuSO4 对纳他霉素水溶液的生物稳定性影响不显著(P ＞ 0.05),而FeCl3 和MnSO4对其生物稳定性影响显著(P ＜ 0.05)。     

酱油酿造中米曲霉与风味酵母协同制曲的研究

本文通过添加一株嗜盐产香酵母菌(鲁氏酵母)与米曲霉协同制曲,探讨制曲过程中酶系、各项理化指标及风味与酵母代谢调控的相关性。动态监测制曲过程中酵母菌落数、米曲霉孢子数、酶系活力、理化指标的变化规律及采用GC-MS对成曲进行挥发性成分分析。结果表明,当酵母的添加量为1.5×106个/g曲料,米曲霉接种量为0.15%(m/m)时,米曲霉孢子数无明显变化,中性蛋白酶活与对照组相当,36 h时达到3100 U/g,α-淀粉酶活较对照组降低了22%,糖化酶活与对照组相比增加了7%,氨肽酶活、酸性羧肽酶活与对照组无明显差异。制曲结束时对照组与添加酵母氨基态氮和还原糖含量基本相近,有机酸含量低于对照。添加酵母和对照组成曲中分别检测出32种,23种挥发性风味物质。综合分析知,接种一定量的酵母菌协同制曲并未对米曲霉生长及酶系产生显著影响,但改善了曲料的风味品质。     

黄酒米曲霉菌种的培养研究

米曲霉培养条件对种曲质量有较大影响,文章以米曲霉为菌种,研究了培养时间和加水量与种曲产孢子数的关系。     

不同波段的光照对无菌牛奶中光敏剂降解的影响

在油脂光照氧化过程中起催化作用的光敏剂在不同可见光照波段下有着不同的吸收特性。光敏剂对光照的吸收量越大,光敏剂降解得越迅速。研究不同可见光光照波段对无菌牛奶中光敏剂核黄素与原卟啉降解的影响,确定出这两种光敏剂降解最为迅速的光照波段。实验结果表明核黄素在400~500nm、原卟啉在500~600nm光照波段下降解迅速。因此,牛奶在这两个光照波段下氧化变质可能更为迅速。     

Riboflavin photo-transformation of genistein and changes in radical scavenging activities of photo-transformed genistein derivatives

Genistein was treated with riboflavin photosensitization and the radical scavenging activities of mixtures of genistein and riboflavin were determined using DPPH and ABTS assays. For a period of light irradiation of 100 min, the initial concentration of genistein decreased by 79.1% for riboflavin photosensitization. New peaks were formed and the peak areas increased for a mixture of riboflavin photosensitized genistein. Genistein derivatives were tentatively identified as trihydroxy isoflavones or genisteins with an additional hydroxyl groups. The radical scavenging abilities of photo-sensitized genistein derivatives were significantly (p<0.05) increased, based on DPPH and ABTS results, compared to samples without visible light irradiation for 100 min of photosensitization. Riboflavin photo-transformation can enhance antioxidant activities in isoflavone aglycones.     

脉冲强光对黄曲霉菌孢子的杀菌效果、微观结构及动力学的影响

脉冲强光是一种新兴的非热杀菌技术。为研究和预测脉冲强光对黄曲霉菌孢子的杀菌作用,在强度2.86,1.60,1.08,0.93 W/cm2脉冲强光下对固体培养基中黄曲霉菌孢子处理1~60 s,并对处理前、后孢子的微观形态进行扫描电镜分析。运用Log-linear模型、Weibull模型和Weibull+tail模型对杀菌致死曲线进行动力学分析。研究表明,随着照射强度增加和时间的延长,脉冲强光对黄曲霉菌孢子的杀菌效果增强。初始菌落数为5.15 lg(CFU/mL)的孢子在2.86 W/cm2下处理19 s可被全部杀死。电镜照片显示脉冲强光处理后孢子细胞结构崩溃。Weibull模型和Weibull+tail模型较Log-linear模型能更好地拟合脉冲强光处理黄曲霉菌孢子的杀菌曲线(R2>0.95)。其中Weibull+tail模型能更加精确地拟合杀菌动力学过程(R2=0.9727)。     

Deactivation of tannin in high tannin milo by treatment with urea

Experiments were conducted to determine the effectiveness of urea in deactivating tannin in high tannin milo. High tannin milo (Pioneer B 815, 3.4 +/- .3% tannin) was reconstituted with aqueous urea solutions to give combinations of 26, 30, and 34% moisture with 2, 3, and 4% urea (percentage of urea per dry weight of milo). All treatments were maintained at 25 degrees C and were effective in deactivating tannin with no differences among moisture or urea content. The average rate of tannin deactivation was 68 +/- 2% d-1. Temperature affected rate of tannin deactivation in milo reconstituted to 30% moisture and 3% urea when stored at 25 or 60 degrees C. Rate of tannin deactivation was 44 +/- 5 and 89 +/- 18% d-1 at 25 and 60 degrees C, respectively. Tannin in high tannin milo can be deactivated rapidly and completely by reconstitution with aqueous urea. These studies demonstrate that tannin is deactivated completely under conditions where urea is an effective preservative of high moisture milo.     

Novel approach to decontaminate food-packaging from pathogens in non-thermal and not chemical way: Chlorophyllin-based photosensitization

This study was focused on the possibility to inactivate main food pathogens, their spores and biofilms on the surface of packaging material polyolefine by Na-chlorophyllin (Na-Chl)-based photosensitization and to compare efficiency of this treatment with conventional antimicrobials.Data indicate that Bacillus cereus and Listeria monocytogenes were effectively inactivated (7 log) by Na-Chl (7.5 × 10⁻⁷ M)-based photosensitization in vitro and on the surface of packaging. Meanwhile to achieve adequate inactivation of thermo-resistant strains, spores or biofilms the higher Na-Chl concentration and longer illumination times had to be used. Comparison of different surface decontamination treatments reveal that photosensitization is much more effective against B. cereus and L. monocytogenes attached on the surface than washing with water or 200 ppm Na-hypochlorite.Our data support the idea that photosensitization may serve in the future for the development of human and environment friendly, non-thermal surface decontamination technique.     

Effect of gamma irradiation and heat treatment on the artificial contamination of maize grains by Aspergillus flavus Link NRRL 5906

Maize (Zea mays L.) is one of the main crops, which is easily susceptable to Aspergillus flavus infection resulting in huge losses worldwide. This study was carried out to investigate the effect of combining heat and irradiation treatments in controlling the fungal growth in maize grains. Surface disinfected maize grains were artificially contaminated with spores of Aspergillus flavus Link NRRL 5906, and then exposed to gamma radiation with doses of 3.0, 4.0 and 5.0 kGy. The samples were additionally heat treated at 60 °C for 30 min. The heat and irradiation treatments showed a synergistic effect on controlling Aspergillus flavus growth. The heat treatment reduced the required radiation dose of about 0.5–1.0 kGy when 4.0 kGy or 5.0 kGy irradiation was used. The combined heat and irradiation treatment of moisture reduced the average CFU by 8 log cycles when 4 kGy or 5 kGy irradiation was used and by 7 log cycles when 3 kGy irradiation was used. The heat treatment of moisture alone reduced the average CFU by only by 0.8 log cycles. Combining irradiation with heat treatment to reduce the required radiation dose is very useful especially when there is a concern over biological side effects of irradiation.     

pH值及乳酸菌对米曲霉固态制曲过程的影响

考察了在固态培养条件下,不同的初始pH值及乳酸菌对米曲霉固态制曲过程的影响。以豆粕和麸皮(质量比为55∶45)为原料,1∶0.6的料水比,0.3%～0.5%的接种量接入沪酿3.042米曲霉种曲,33℃下制曲,定时取样测定固体曲的蛋白酶活力及孢子数。结果表明:适当偏酸性的环境有利于成曲蛋白酶的提高,培养基初始pH调节为6.5时米曲霉中性蛋白酶活力获得最大值(4 080±61)U/g干基,较对照组提高33%～37%;添加1.0%～2.0%乳酸菌,也同样起到改善米曲霉制曲过程的效果。     

黑曲霉电子束辐照突变菌的遗传毒性评价

依据食品安全性评价中遗传毒性评价的方法,通过对电子束辐照诱变育种黑曲霉突变菌进行Ames试验、小鼠骨髓细胞微核试验、小鼠精子畸形试验研究,评价黑曲霉电子束辐照突变菌的遗传毒性。结果表明,在Ames试验中,黑曲霉突变菌各剂量组无论是否添加S9代谢活化系统,黑曲霉突变菌各剂量组的回变菌落数均未超过自发回变菌落数的2倍,表明黑曲霉突变菌对染色体无致突变作用。在小鼠骨髓细胞微核试验中,黑曲霉突变菌不能引起哺乳动物嗜多染红细胞的微核细胞率显著增加(p>0.05),黑曲霉突变菌对细胞染色体并未造成明显损伤,表明黑曲霉突变菌并无致突变作用。在小鼠精子畸形试验中,黑曲霉突变菌各剂量组的精子畸形率与阴性对照组相比无显著性差异(p>0.05),表明黑曲霉突变菌并未对小鼠的精子产生致畸作用。因此,在本实验条件下,Ames试验、小鼠骨髓细胞微核试验、小鼠精子畸形试验结果均为阴性。表明黑曲霉电子束辐照突变菌属于实际无毒级别,并无遗传毒性作用。     

Reprint of: Novel approach to decontaminate food-packaging from pathogens in non-thermal and not chemical way: Chlorophyllin-based photosensitization

This study was focused on the possibility to inactivate main food pathogens, their spores and biofilms on the surface of packaging material polyolefine by Na-chlorophyllin (Na-Chl)-based photosensitization and to compare efficiency of this treatment with conventional antimicrobials.     

Mechanisms of photochemistry and reactive oxygen production by fullerene suspensions in water

Buckminsterfullerene (C60) is a known photosensitizer that produces reactive oxygen species (ROS) in the presence of light; however, its properties in aqueous environments are still not well understood or modeled. In this study, production of both singlet oxygen and superoxide by UV photosensitization of colloidal aggregates of C60 in water was measured by two distinct methods: electron paramagnetic resonance (EPR) with a spin trapping compound, and spectrophotometric detection of the reduced form of the tetrazolium compound XTT. Both singlet oxygen and superoxide were generated by fullerol suspensions while neither was detected in the aqu/nC60 suspensions. A mechanistic framework for photosensitization that takes into account differences in C60 aggregate structure in water is proposed to explain these results. While theory developed for single molecules suggests that alterations to the C60 cage should reduce the quantum yield for the triplet state and associated ROS production, the failure to detect ROS production by aqu/nC60 is explained in part by a more dense aggregate structure compared with the hydroxylated C60.     

Effect of UV-C irradiation on inactivation of Aspergillus flavus and Aspergillus parasiticus and quality parameters of roasted coffee bean (Coffea arabica L.)

ABSTRACT

This study investigated the antifungal effect of ultraviolet-C (UV-C) against Aspergillus flavus and Aspergillus parasiticus on roasted coffee beans. Also, any changes in the quality of the roasted coffee beans were measured after UV-C irradiation. As UV-C irradiation time increased (0–2 h), the number of surviving A. flavus and A. parasiticus spores significantly (P < .05) decreased. The reduction values of A. flavus in round part, crack part, and whole roasted coffee beans were 2.16, 0.71, and 1.58 log₁₀ CFU g^?1, respectively, and the reduction values of A. parasiticus in round part, crack part, and whole roasted coffee beans were 1.03, 0.37, and 0.72 log₁₀ CFU g^?1, respectively, after 2 h of UV-C irradiation. Field emission scanning electron microscopy showed that the morphology of A. flavus and A. parasiticus spores included expanded wrinkles that were deformed by UV-C irradiation. The Hunter colours were significantly reduced (P < .05). There was no significant change (P > .05) in moisture content, but the pH was significantly decreased (P < .05). Most of the sensory parameters did not change, but there was a significant difference (P < .05) in flavour. Based on this study, 2 h of UV-C irradiation was effective in reducing 90% of A. flavus, but it was not effective against A. parasiticus present on roasted coffee beans. Also, Hunter colour, pH, and sensory parameters (flavour) were changed by UV-C irradiation.