制鞋工业中用于抑菌处理的甘油一酸酯(英文)

以甘油与不同偶数脂肪酸为原料合成了一系列甘油 酸酯(MAGS):甘油一辛酸酯(MAGC8∶0),甘油一癸酸酯(MAGC10∶0),甘油 2 乙基乙酸单酯(MAG2Eth C6∶0)和甘油一月桂酸酯(MAGC12∶0),测定其抑菌效果。这些材料以乙醇溶液的形式应用于衬里材料上。酵母菌(白色念菌和近平滑假丝酵母)的实验证明这两种酵母菌对MAGC8∶0和MAGC10∶0敏感。在100～150mg/L的浓度范围内MAGC8∶0和MAGC10∶0抑制微生物生长。纤维霉菌特别受到MAGC8∶0(100mg/L)溶液的抑制。当这一浓度的MAGC8∶0溶液应用于被测材料时,黑曲霉、点状毛霉、赭绿青霉具有抵抗性。实验证明,各种MAGS对不同种类可造成霉菌病的真菌微生物的防霉效果不同。     

8种单体多酚对葡萄酒微生物的抑菌活性比较

酚类化合物不仅能赋予葡萄酒丰富的色泽、风味和抗氧化活性,还能抑制葡萄酒微生物的生长。为了比较不同多酚化合物抑菌能力的大小,用牛津杯测试法研究了不同质量浓度(2、5、10 g/L)单体多酚(儿茶素、表儿茶素、没食子酸、表没食子儿茶素没食子酸酯(epigallocatechin-3-gallate,EGCG)、鞣花酸、杨梅酮、槲皮素和山奈酚)对引起葡萄酒病害的代表菌种:乳酸菌、醋酸菌和酵母菌的抑制作用。结果表明:在8种供试多酚中,杨梅酮、槲皮素和EGCG抑菌能力相对较强;黄烷-3-醇类化合物对醋酸菌和酵母菌的抑制能力比乳酸菌更强,没食子酸则恰好相反;山奈酚对所有供试菌株都没有抑菌能力。多酚能在一定程度上抑制葡萄酒微生物的生长繁殖。     

固定化脂肪酶催化醇解天然奶油合成含硫风味酯的研究

以无水奶油为脂肪酸来源,固定化脂肪酶TL IM为催化剂,无溶剂体系下催化3-甲硫基丙醇与无水奶油反应制备3-甲硫基丙酯。采用十七酸甲酯为内标,GC-FID监测反应过程中转化率的变化,并分析脂肪酶对不同碳链脂肪酸的选择性。结果显示:酶解前8h,脂肪酶对C4-C14脂肪酸选择性优势明显,随着反应的进行,对短链脂肪酸选择性逐渐变小,而对C16-C18脂肪酸选择性增加;当反应温度为50℃,脂肪酶添加量为5wt%,3-甲硫基丙醇与无水奶油的摩尔比3∶1,反应时间为8h时,产物中3-甲硫基丙酯的浓度分别为:丁酸3-甲硫基丙酯29.75mg/m L、己酸3-甲硫基丙酯15.32mg/m L、辛酸3-甲硫基丙酯7.22mg/m L、癸酸3-甲硫基丙酯21.32mg/m L、十二酸3-甲硫基丙酯26.64 mg/m L、十四酸3-甲硫基丙酯77.62mg/m L,C4-C14总转化率为71.16%。     

反胶束体系中脂肪酶催化合成单月桂酸甘油酯

研究了在二-(2-乙基己基)琥珀酸酯磺酸钠(AOT)/异辛烷反胶束体系中,奶酪香精脂肪酶催化三月桂酸甘油酯和甘油反应制备单月桂酸甘油酯,并研究了反胶束体系的基本特性。结果表明:随着AOT质量浓度的增加,反胶束体系的增溶水量(W_0)、“水池”直径及黏度增加;最佳工艺条件为反应温度55℃、振荡器转速180 r/min、AOT质量浓度0. 1 g/m L、含水量0. 05 m L/m L、脂肪酶用量50 mg/m L、缓冲液pH 7. 5、底物摩尔比(甘油与三月桂酸甘油酯摩尔比) 3∶1、反应时间10h,此时体系中单月桂酸甘油酯的质量分数为84. 4%;当AOT质量浓度和含水量较小时,反胶束体系的W_0增加可促进酶催化反应的进行,但是当W_0和体系相对黏度继续增加,单月桂酸甘油酯的质量分数反而降低。     

Nisin、乳酸钠和单辛酸甘油酯延长酱油保质期研究

使用3种无害的防腐剂Nisin、乳酸钠(NaL)和单辛酸甘油酯(C8MG),通过L9(34)正交试验对酱油的保鲜效果进行研究.结果表明:使用Nisin 60IU/g(A2),NaLl%(B1),C8MG 0.02%(C2)效果较好.酱油中的酵母菌和霉菌受到良好的抑制,延长酱油的保质期.     

高效液相色谱法同时测定食品中18种食品添加剂

建立高效液相色谱同时测定食品中18种食品添加剂的高通量分析方法。对于不含油脂或油脂含量低的样品采用含抗坏血酸棕榈酸酯的正己烷饱和乙腈-6mol/L HCl溶液-饱和氯化钠混合溶液一次提取净化,对于油脂样品采用含抗坏血酸棕榈酸酯的正己烷饱和乙腈-乙腈饱和正己烷液液萃取。采用Ecosil C18色谱柱(250mm×4.6mm,5μm),乙腈-0.6%乙酸溶液作为流动相,梯度洗脱,用紫外检测器检测,检测波长280nm,外标法峰面积定量。18种食品添加剂在1.0～25mg/L范围内线性良好,相关系数r均大于0.99,样品在10、25mg/kg和50mg/kg三个添加水平的平均回收率为88.9%～99.9%之间,相对标准偏差为2.43%～11.7%(n=6),方法的定量限为10mg/kg。方法简便、准确,适用于食品中18种食品添加剂高通量的检测。     

二氧化氯和羧甲基纤维素联合处理对中华猕猴桃保鲜效果的影响

研究二氧化氯(chlorine dioxide,ClO_2)和羧甲基纤维素(carboxymethyl cellulose,CMC)保鲜处理对中华猕猴桃贮藏期间生理和品质的影响。先将猕猴桃在80 mg/L ClO_2溶液中浸泡10 min后分成6组,然后分别浸泡于质量浓度0. 0、5. 0、10. 0、15. 0、20. 0、25. 0 g/L的CMC溶液中,10 min后沥干,对其贮藏期间腐败率、失重率、色差、硬度、可溶性固形物、可滴定酸、Vc进行测定。结果表明:与对照相比,经80 mg/L ClO_2单独或联合不同浓度的CMC保鲜处理的猕猴桃均能有效抑制果实的呼吸强度,减少果实的失重率和腐败率,保持较好的色泽和硬度,能有效减缓猕猴桃可溶性固形物、可滴定酸、Vc的损耗。尤其是80 mg/L ClO_2联合20. 0 g/L的CMC处理的猕猴桃,保鲜效果最好。该方法成本很低,研究结果可为中华猕猴桃的贮藏保鲜提供一定的理论依据。     

采前喷施保鲜剂对蓝莓贮藏品质的影响

以粉蓝蓝莓为试验材料,通过采前喷施不同保鲜剂(800mg/L纳他霉素、1 000mg/Lε-聚赖氨酸、800mg/L壳聚糖),采后于(0.5±0.5)℃冷藏,研究蓝莓果实生理品质的变化。结果表明:采前不同保鲜剂处理均能降低蓝莓果实的腐烂率,延缓蓝莓鲜果的硬度、可溶性固形物含量、可滴定酸含量及花色苷含量的降低,降低蓝莓鲜果呼吸强度及乙烯生成速率,维持较好的过氧化物酶、过氧化氢酶、脂氧合酶和抗坏血酸过氧化物酶活性,并有效降低蓝莓霉菌及酵母菌的菌落总数。采前喷施800mg/L纳他霉素对蓝莓果实的贮藏效果最好,能有效抑制蓝莓的衰老进程,维持更好的贮藏效果。     

传统发酵豆豉含盐量及盐度对豆豉品质的影响

研究首先对我国目前市场上销售的不同产地有代表性的商品豆豉的含盐量做了调查和分析,含盐量在10.000～15.000 g/100 g之间.其次采用两段式控温后发酵工艺(前期40～42℃,后期28～30℃),厌氧密封发酵10天,对不同盐度(0％,2％,4％,6％,8％,12％,W/W)豆豉后发酵过程中优势微生物:乳酸菌、酵母菌的生长变化和pH值、总酸、氨基酸态氮等成分的变化,以及不同盐度豆豉产品的感官品质进行了研究.结果表明,低盐度(2％,4％,W/W)发酵早期促进乳酸菌的生长,乳酸菌数106～107 cfu/g;后期利于酵母菌的繁殖,酵母菌数达108 cfu/g,并在一定程度上抑制了腐败菌的生长;总酸含量1.3～1.6 g/100 g,氨基酸态氮含量0.7～0.8 g/100 g,感官评价产品品质较好.     

无患子油理化指标和甘三酯结构分析

以福建和浙江两个产地的无患子为原料,对其油脂的主要理化性质、甘三酯组成、VE含量和氧化稳定性进行了研究.结果表明:两个产地的无患子油中不饱和脂肪酸含量均达到80%以上,其中,主要组分油酸(O,C18:1)在50%以上,二十碳一烯酸(Ei,C20∶1)在21%以上,花生酸(Ar,C20:0)7%左右,亚油酸(L,C18:2)7%左右,棕榈酸(P,C16:0)在5%以上;采用胰脂酶水解分析油脂Sn-2位脂肪酸组成分布,可计算出其主要的甘三酯为EiOO、OOO、EiOEi、OOAr、EiOAr;无患子油中VE含量较高,其中来自福建的油中VE含量为26.30 mg/100g(γ-VE占20.78 mg/100g),来自浙江的油中VE含量为30.70 mg/100g(γ-VE占24.26 mg/100g);两个产地的无患子油氧化稳定性均较好.     

Valorization of Olive Pomace Oil with Enzymatic Synthesis of 2‐Monoacylglycerol

2‐Monoacylglycerols (2‐MAG) with a high content of oleic acid at sn‐2 position was synthesized by enzymatic ethanolysis of refined olive pomace oil, which is a byproduct of olive oil processing. Six lipases from different microbial sources were used in the synthesis of 2‐MAG. Immobilized lipase from Candida antarctica gave the highest product yield among the selected lipases. Response surface methodology was applied to optimize reaction conditions; time (4 to 10 h), temperature (45 to 60 °C), enzyme load (10 to 18 wt%), and ethanol:oil molar ratio (30:1 to 60:1). The predicted highest 2‐MAG yield (84.83%) was obtained at 45 °C using 10 (wt%) enzyme load and 50:1 ethanol:oil molar ratio for 5 h reaction time. Experiments to confirm the predicted results at optimum conditions presented a 2‐MAG yield of 82.54%. The purification yield (g 2‐MAG extracted/100 g of total product) was 80.10 and 69.00 for solvent extraction and low‐temperature crystallization, respectively. The purity of the synthesized 2‐MAG was found to be higher than 96%.     

Antimicrobial effects of probiotic bacteria against selected species of yeasts and moulds in cheese-based dips

The antimicrobial properties of selected probiotic bacteria against Aspergillus niger , Penicillium roqueforti , Fusarium spp., Candida albicans and Saccharomyces cerevisiae were examined. Well diffusion and spot and streak methods showed strong inhibition effect of probiotic bacteria and their metabolites against moulds and minimal effect against yeasts. Among the moulds species tested, the inhibitory effect was strongest against Fusarium spp., moderate against Penicillium roqueforti and minimal against A. niger . All strains of Lactobacillus rhamnosus and L. paracasei subsp. paracasei showed maximum inhibitory effect. When probiotic bacteria and yeasts and moulds were co-cultured in broth media, strains of L. rhamnosus showed maximum inhibitory effect, whereas L. paracasei subsp. paracasei , L. acidophilus , Bifidobacterium animalis and Propionibacterium showed moderate inhibitory effect against C. albicans . Saccharomyces cerevisiae was minimally controlled by probiotic bacteria. Pre-grown probiotic bacterial culture metabolites controlled yeasts and moulds more effectively than their freeze-dried or frozen forms. Adding metabolites of probiotic bacteria (5% w/w) showed an effective control against A. niger , Fusarium spp. and C. albicans during the shelf life of 10 weeks at 4 °C and no colonies of yeasts and moulds were formed on the surface of the dip.     

Monoacylglycerols derived from butter oil by Penicillium roquefortii in suspension cultures

Structural isomers of monoacylglycerols (monoglycerides, MAGs) were identified and compared after degradation of butter oil by two strains of Penicillium roquefortii and a commercial lipase from P roquefortii (EC 3.1.1.3) at pH 7.0 and 10 °C. The conditions were selected as they were comparable with those used in the manufacture of blue mould‐ripened cheese. The commercial lipase was selected to compare with the fungal strains in terms of acyl migration. Results showed that the main isomers formed by lipolysis with the commercial lipase were sn‐2 MAGs (64 mol%), whilst spores and emerging mycelia of P roquefortii produced mainly sn‐1(3) MAGs (83–90 mol%). The work reported here may lead to further assessment of different MAG structural isomers as natural preservatives in foods and dairy products. © 2002 Society of Chemical Industry     

Influence of a commercial monoacylglycerol on the crystallization mechanism of palm oil as compared to its pure constituents

The effect of a commercial monoacylglycerol (MAG), Myverol™ 18 04-PK (Myverol), on the non-isothermal crystallization mechanism of palm oil (PO) was investigated and compared to the effect of the two main constituents of Myverol, monopalmitin and monostearin. The MAGs were added to PO in concentrations up to 8% and the blends were studied using different techniques (differential scanning calorimetry (DSC), X-ray diffraction (XRD) and polarized light microscopy (PLM)). The DSC crystallization profiles revealed an earlier onset of crystallization along with extra crystallization peaks when MAGs were added to PO. Combined with X-ray results, it could be concluded that the crystallization process of the blends is initiated by the MAGs crystallizing in the α form and then transforming to sub-α. The effect on the non-isothermal crystallization of the PO TAGs is confined to an earlier onset of crystallization, probably through a template effect, and an effect on the crystal structure coarseness.     

Fungal metabolism of butter and shea oils by Penicillium roquefortii in solid state cultures

Monoacylglycerols (monoglycerides, MAGs) were produced from butter oil and shea stearin fraction (shea oil) by two strains of Penicillium roquefortii, FRR 2456 (isolated from a spoilt melon) and Wisbey PJ (a commercial dairy strain), at pH 7.0 at 10 and 25 °C. The system was designed as a model of cheese using modified Czapek medium in solid state cultures. Shea oil with its unique fatty acid profile (stearic, oleic and palmitic acids) was used for comparison with butter oil. Yields of MAGs, which ranged from 3 to 14 g kg^?1 oil, were higher with butter than with shea oil and higher when the spoilage strain FRR 2456 was used. Monoacylglycerols produced by mycelium‐bound lipases from both fungal strains were mainly sn‐1(3) or α isomers (60–70 mol%). Monopalmitin was the major MAG produced from both butter and shea oils. The production and use of MAGs alone or in combination with free fatty acids (FFAs) as food preservatives are discussed. It is implied that sn‐1(3) MAGs together with free fatty acids may be part of a natural antimicrobial system in relatively high‐pH foods such as blue mould‐ripened cheese where growth of foodborne pathogens such as Listeria monocytogenes can be a problem. Copyright © 2003 Society of Chemical Industry     

Development of novel method for screening microorganisms using symbiotic association between insect (Coptotermes formosanus Shiraki) and intestinal microorganisms

It is becoming increasingly difficult to isolate novel useful microorganisms from the natural environment using conventional screening methods based on pure culture techniques. A novel method for screening microorganisms in symbiotic association with insects was developed. This method involves the following two steps. In the first step, the existence of desired microorganisms that grow well by degrading difficult-to-degrade materials in the gut of insects is detected using the survivability of insects as an indicator. In the second step, the desired microorganisms are selected from the surviving insects. The second step is based on an idea that the guts of insects act as continuous-culture systems whereby microorganisms that cannot degrade diet components are washed out whereas those that can degrade diet components are retained and made to multiply in the gut. Coptotermes formosanus Shiraki was fed with an artificial diet containing phenol as a model of lignin-derived and difficult-to-degrade compound. Each C. formosanus feeding on an artificial diet containing 100 mg/l phenol had different levels of adaptation to the toxicity of phenol. About 20% of C. formosanus fed with an artificial diet containing 100 mg/l phenol died within a few days whereas others survived for more than 10 d. The structure of the intestinal microorganisms of the surviving C. formosanus fed with the 100 mg/l phenol artificial diet gradually changed and was very different from that of the bacterial communities obtained from the enrichment culture of wood-feeding C. formosanus using an artificial medium containing phenol as a sole carbon source. Furthermore, Only three species (as DGGE band) were detected from the gut of wood-feeding C. formosanus, whereas 200 times more phenol-degrading microorganisms were detected in the gut of C. formosanus feeding on a phenol artificial diet. Out of these nine species (as DGGE band) of phenol-degrading microorganisms were isolated. The screening method developed in this study can also be applied to various insects, leading to the isolation of various microorganisms that can degrade difficult-to-degrade compounds.     

Compositional study on rice bran oil after lipase-catalyzed glycerolysis and solvent fractionations

ABSTRACT:  Rice bran oil (RBO) was modified through lipase-catalyzed glycerolysis. After 48 h reaction, the reactant (RBO-G, solved in hexane) containing 0.14 mg/mL of MAG, 0.19 mg/mL of DAG, and 0.93 mg/mL of TAG was obtained. Extending the reaction to 72 h resulted in 0.37 mg/mL of DAG with concomitant reduction in TAG (0.68 mg/mL). Two solvent fractionation methods, independent and sequential fractionation, were performed with acetone and hexane at 0, −8, −14, or −35 °C. The fraction with most unsaturated fatty acids (ΣUFA) was liquid fraction from independent fractionation at −35 °C (−35In) from hexane, showing 88.3%ΣUFA content. Nevertheless, when yield (wt%) was considered, the highest amount of UFA was obtained from 0In (liquid fraction from independent fractionation at 0 °C) with hexane, resulting in 82.3%ΣUFA with 97.9 wt% recovery. Normal-phase HPLC was conducted for the compositional study of RBO-G. Overall, solid fractions from sequential fractionation at 0 °C (0SeSo) and independent fractionation at −35 °C (−35InSo) with hexane contained the high concentration of total MAG and DAG, ranging from 0.94 to 1.35 (mg/mL).     

聚氯乙烯类食品包装材料中三甲基锡向食品模拟物的迁移规律

目的：建立聚氯乙烯类包装材料和食品模拟物中三甲基锡的超高效液相色谱-串联质谱（ultra performanceliquid chromatography-tandem mass spectrometry,UPLC-MS/MS）联用测定方法。用该方法研究聚氯乙烯中的三甲基锡向食品模拟物的迁移规律。方法：聚氯乙烯包装材料样品用乙酸乙酯提取。食品模拟物经阳离子固相萃取柱净化富集,洗脱液水浴条件下氮气吹干,残渣用流动相溶解,旋涡混匀,过0.22 μm微孔滤膜,经C18色谱柱完成分离,MS/MS仪上采用多反应监测正离子模式测定三甲基锡,外标法定量。在设定的不同温度条件下,将聚氯乙烯包装材料浸泡于食品模拟物中,于不同的时间点移取浸泡液,经前处理后测定三甲基锡迁移量。结果：三甲基锡在0.1～100.0 μg/L范围内线性关系良好（相关系数r=0.999 8）,检出限为0.02 μg/L。在1.0、10.0、50.0 μg/L 3 个添加水平范围内的平均回收率为90.6%～97.3%,相对标准偏差不高于6.9%。测定结果显示,三甲基锡迁移量在水模拟物中为0.19～1.65 μg/L、在体积分数10%乙醇模拟物中为0.19～9.89 μg/L、在3 g/100 mL乙酸模拟物中为0.11～9.96 μg/L、在正己烷模拟物中为0.15～3.54 μg/L。结论：建立的阳离子固相萃取-UPLC-MS/MS联用法测定食品模拟物中三甲基锡的方法快速简单、准确有效,三甲基锡在体积分数10%乙醇溶液和3 g/100 mL乙酸溶液迁移量较高,且随温度升高、时间延长,迁移量增加,一定时间后达到迁移平衡。     

Antimicrobial activity of some plant extracts and essential oils against foodborne pathogens in vitro and on the fate of inoculated pathogens in chocolate

The efficacy of commercially available plant extracts and essential oils used extensively as flavour ingredients in confectionery products were used as antimicrobials in laboratory media against the following microorganisms: Escherichia coli O157:H7, Salmonella Enteritidis, Salmonella Typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Bacillus cereus. Using the disc diffusion method, inhibition zones in diameter >20 mm were observed by adding 10 μl of each antimicrobial substance on the following microorganisms: lemon flavour applied on E. coli O157:H7, lemongrass essences against S. aureus, plum using a B. cereus strain and strawberry flavour using a L. monocytogenes strain. E. coli O157:H7 strains were the most susceptible microorganisms inhibited by 18 extracts, followed by S. Typhimurium and S. aureus which were inhibited by 17 extracts. Lemon flavour, lemongrass essences, pineapple and strawberry flavour inhibited the foodborne pathogens at the lowest concentration (5 ml/100 ml). Plant extracts and essential oils with potent antimicrobial activities were tested in chocolate held at different temperatures (7 and 20 °C) in dry or humidified environment, which resulted in different a_w values of the product (i.e. 0.340, 0.450, and 0.822), in order to determine their efficacy on the fate of the inoculated pathogens. The most inhibitory action was observed by lemon flavour applied on chocolate inoculated with E. coli cocktail culture after storage at 20 °C for 9 days. Plant extracts tested on chocolate show an enhanced inhibitory effect during storage at 20 °C indicating that their application may provide protection in case of storage at the above temperature or even higher.     

Effect of feeding corn, hull-less or hulled barley on fermentation by mixed cultures of ruminal microorganisms

Increased demands for corn grain warrant the evaluation of alternative grain types for ruminant production systems. This study was conducted to determine the effects of hulled and hull-less barley (Hordeum vulgare L.) cultivars compared with corn (Zea mays L.) as an alternative grain type on fermentation in cultures of mixed ruminal microorganisms. Three continuous fermentors were fed 14 g of dry feed per day (divided equally between 2 feedings) consisting of alfalfa (Medicago sativa L.) hay pellets (40% of dry matter) and 1) ground corn, 2) hulled barley, or 3) hull-less barley concentrate (60% of dry matter) in each fermentor. Following an adaptation period of 5 d, culture samples were taken at 2 h after the morning feeding on d 6, 7, and 8 of each period for analysis. A second run of the fermentors followed the same treatment sequence to provide replication. Culture pH was reduced with corn (5.55) and did not differ between barley cultivars (average pH 5.89). Total volatile fatty acid concentration and acetate to propionate ratio were not different across grain type or barley cultivar with the exception of greater total volatile fatty acid concentrations with hull-less barley. Corn produced less methane (14.6 mmol/d) and ammonia-N (7.3 mg/100 mL) compared with barley (33.1 mmol/d and 22 mg/100 mL, respectively); methane was greater with hull-less barley but ammonia-N concentration was similar between the 2 barley cultivars. Hull-less barley had greater digestibility compared with hulled barley, and corn had reduced digestibility compared with barley. Concentrations of C18:0 were greater and those of C18:1 and C18:2 lesser in cultures fed hulled and hull-less barley compared with corn. Our data indicate that grain type and barley cultivar have an impact on ruminal fermentation. The lesser starch concentration of barley minimized the drop in culture pH and improved digestibility.