有机介质中酶催化合成月桂酸甾醇酯

初步研究了不同脂肪酶在有机溶剂中对月桂酸甾醇酯的催化效果,最终选定Novo435脂肪酶为催化剂,正己烷为溶剂,反应温度40℃,酶用量为底物质量的15%,底物摩尔配比为3∶1（月桂酸∶甾醇）,反应时间为24h,酯化率达到36.5%。     

LIPASE-CATALYZED ACIDOLYSIS OF CORN OIL WITH CONJUGATED LINOLEIC ACID IN HEXANE

Lipase-mediated acidolysis of corn oil with conjugated linoleic acid (CLA) was studied in hexane. The largest extent of incorporation was obtained using a weight ratio of CLA to corn oil of 1:7 (1:2.22 mole ratio). Commercial immobilized lipases from Rhizomucor miehei and Candida antarctica effectively catalyzed interesterification. Of the total acylglycerols in the products, triacylglycerols constituted >90%. For both immobilized enzymes, CLA residues were esterified mainly at the sn-1,3 positions.     

THE CONTENT OF SOME ORGANIC ACIDS IN BEER AND OTHER FERMENTED MEDIA

The acid content of a range of ales and lagers has been measured for some organic acids related to the Krebs cycle, and found to vary widely. Acetate, pyruvate, lactate, succinate, pyroglutamate, malate and citrate were present in all cases and α-ketoglutarate was usually detected. α-Hydroxyglutarate was recognized in a number of beers. The effect of the acids on the pH of beer is assessed. The strain of yeast which is used markedly influences the levels of all acids except pyroglutamate and the conditions of yeast propagation have a substantial influence on the extent of acid accumulation. During the fermentation of wort and synthetic media the extent of organic acid excretion is proportional to the extent of fermentation, but the nature of the acids which are excreted varies during the fermentation period. In synthetic media, nitrogen source is shown to have a substantial effect on the accumulation of organic acid. Pyruvate and acetate levels vary inversely towards the end of fermentation, suggesting that yeast converts pyruvate to acetate.     

LIPASE-CATALYZED SYNTHESIS OF STRUCTURED LIPIDS IN POLAR SOLVENTS

The effect of acetone on structured lipid synthesis by Lipozyme IM60 in n-hexane was studied. Transesterification of tristearin with capric, lauric, myristic, palmitic and oleic acids was performed individually and in combinations at equal mole ratios. Higher incorporation of oleic acid was observed with the addition of acetone when compared to other fatty acids. Incorporation of capric acid decreased with increase in acetone concentration. The overall activity of enzyme decreased in acetone compared to n-hexane.     

LIPASE-CATALYZED PRODUCTION OF STRUCTURED LIPIDS VIA ACIDOLYSIS OF FISH OIL WITH CAPRYLIC ACID

Structured lipids containing eicosapentaenoic and docosahexaenoic acids were manufactured in a batch reactor by lipase-catalyzed acidolysis of fish oil with caprylic acid. The following free lipases (Lipase AP, Aspergillus niger ; Lipase P, Pseudomonus sp. ; Lipase AY, Candida rugosa ; Lipase AK, Pseudomonas fluoresescens ; Lipase F, Rhizopus oryzae ; Lipase D, Rhizopus delemar ) were screened under selected reaction conditions. The conditions were enzyme load 5%, substrate mole ratio 1:6 (fish oil: caprylic acid), and reaction temperature of 50C. Lipase AK had the highest activity and was suitable for production of structured lipids from fish oil. The optimal mole substrate ratio of fish oil to caprylic acid for Lipase AK was 1:6 to 1:8. The time course of the reaction at different enzyme loads demonstrated that 40% incorporation of caprylic acid could be obtained for Lipase AK in 5 h with 10% enzyme load. Addition of water had little effect on the activity of the lipase. Lipase AK and Lipozyme IM were further compared under the same conditions, in which Lipase AK had a slightly higher incorporation of caprylic acid, similar acyl migration of caprylic acid from sn-1,3 positions to the sn-2 position, and a slightly lower selectivity towards docosahexaenoic acid.     

REACTION CONDITIONS IN VITRO AFFECT RATE OF LIPASE-CATALYZED HYDROLYSIS OF OLIVE OIL

An in vitro procedure that approximates many of the conditions prevailing in the human duodenum was further refined and used to study the effect of dietary fibers on the rate of lipase-catalyzed hydrolysis of olive oil. Increasing bile salt concentration over the range of 2–8 mM caused a marked increase in the rate of lipid hydrolysis, both in the presence and absence of red wheat bran. Stirring speed (20–90 rpm) had no significant effect on the rate of lipolysis in the absence of fiber, whereas in the presence of fiber an increase in stirring speed was often accompanied by an increase in the rate of lipolysis. Fiber inhibition was sometimes observed regardless of stirring speed. Sequence of addition of reactants influenced the rate of lipolysis. Attention to these variables is clearly important if meaningful, reproducible results are desired.     

VARIOUS DIETARY FIBERS DECREASE THE RATE OF LIPASE-CATALYZED HYDROLYSIS OF OLIVE OIL IN VITRO

An in vitro method was used to evaluate the effect of different types of dietary fiber on the initial rate of hydrolysis of olive oil catalyzed by porcine pancreatic lipase. Lipolysis was measured at pH 6.5 and 37C while stirring at 20 rpm. Excellent recoveries of added known amounts of oleic acid were obtained in control and fiber-containing samples. Dietary fibers tested (all 3% by weight unless otherwise noted) were: red wheat bran, white wheat bran, oat bran, soyfiber, sugarbeet fiber, chitin, chitosan, cellulose, pectin-LM and psyllium seed (1.5%). All inhibited lipolysis (35–85%) except cellulose and pectin. The contribution of aqueous extracts of the insoluble fibers to the total inhibitory properties of the fibers were: 0% for the two wheat brans; 100% for oat bran, chitin, chitosan and sugarbeet fiber; and 63% for soyfiber.     

钛白在CA丙酮溶液中的分散

ＴｉＯ２在ＣＡ丙酮溶液中的分散效果．直接影响到原液的增白、过滤性和可纺性．本文在对比多种分散方式下，选用胶体磨配制ＴｉＯ２浆液，其分散性高，显微镜下观察其粒径较匀，电镜显示其粒径较小，均在５ｕｍ以内，符合烟用二醋纺丝要求．且制法简单，快速。     

LIPASE-CATALYZED ACIDOLYSIS OF ALGAL OILS WITH CAPRIC ACID: OPTIMIZATION OF REACTION CONDITIONS USING RESPONSE SURFACE METHODOLGY

Lipase-assisted acidolysis of algal oils, arachidoinc acid single cell oil (ARASCO), docosahexaenoic acid single cell oil (DHASCO) and a single cell oil rich in both docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA, n-6) known as OMEGA-GOLD, with a medium-chain fatty acid (capric acid) was studied. Response surface methodology was used to obtain a maximum incorporation of CA into algal oils. The process variables studied were the amount of enzyme (2–6%), reaction temperature (35–55C) and incubation time (12–36 h). The amount of water added and mole ratio of substrate (algal oil to CA) were kept at 2% and 1:3, respectively. All experiments were conducted according to a face-centered cube design. Under optimum conditions (12.3% of enzyme; 45C; 29.4 h), the incorporation of CA was 20.0% into ARASCO, 22.6% into DHASCO (4.2% enzyme; 43.3C; 27.I h) and 20.7% into the OMEGA-GOLD oil (2.5% enzyme, 46.6C; 25.2 h).     

醋酸乙烯酯-丙烯酸丁酯乳液共聚的研究

乳液聚合是生产高聚物的重要方法。本文用半连续乳液聚合的方法合成醋酸乙烯酯丙烯酸丁酯乳液,探讨了乳化剂、引发剂等因素对乳液聚合及乳液性质的影响。     

泰国有机食品认证启示

综述了关于中泰两国有机食品认证、生产方面的区别，以及泰国有机食品生产现状，最后对我国有机食品的发展提出了建议。     

FORMATION OF PYRIDINES FROM THERMAL INTERACTION OF GLUTAMINE OR GLUTAMIC ACID WITH A MIXTURE OF ALKADIENALS IN AQUEOUS AND OIL MEDIA

A mixture of alkadienals containing equimolar concentrations of (t,t)-2, 4-heptadienal, (t,t)-2, 4-nonadienal, and (t,t)-2, 4-decadienal was heated at 180C with glutamine or glutamic acid in the ratio of individual 2,4-alkadienals to amino acid of 1:1:1:1 in aqueous and oil media where glutamine could generate free ammonia readily but glutamic acid could not. When the mixture of three alkadienals was reacted with glutamine, the total amounts of alkylpyridines were much higher in the oil systems even though some alkylpyridines, such as 3-butylpyridine, 3-pentylpyridine, and 4-pentylpyridine, could only be found in the aqueous systems. In the interaction of the mixture of three alkadienals with glutamic acid, only three 2-alkylpyridines including 2-ethylpyridine, 2-butylpyridine, and 2-pentylpyridine, which could be formed directly from the corresponding alkadienals, were produced under both conditions.     

ORGANIC ACIDS PROFILE IN TOMATO JUICE BY HPLC WITH UV DETECTION

A simple method was developed to determine 10 organic acids simultaneously in tomato products using reversed‐phase high‐performance liquid chromatography column with the diode array detector set at 210 nm. After centrifugation and filtration, the samples were passed through an anion exchange resin and the organic acids were released using 0.1‐N HCl. The chromatographic separation was achieved with isocratic analysis in a 20‐min run. The method was reliable and sensitive, the coefficient of determination of the standard calibration curve is 0.9925 ≤ r² ≤ 0.9999 and the limit of detection ranged from 0.08 to 6.00 mg/kg for trans‐aconitic acid and acetic acid, respectively. The limit of quantification ranged from 0.19 to 15.18 mg/kg for trans‐aconitic and acetic acid, respectively. To establish the efficiency of the anion resin, the procedure was applied to a standard solution of a mixture of organic acids. The organic acids recovery ranged from 87.0% ± 1.9 for citramalic acid to 109.9% ± 5.2 for fumaric acid.     

QUALITY EVALUATION OF REFRIGERATED CHICKEN WINGS TREATED WITH ORGANIC ACIDS

The effects of acetic acid (AA), lactic acid (LA), or citric acid (CA) dip treatments on aerobic plate counts (APC), Hunter color values, and sensory evaluation scores of chicken wings stored at 4C were assessed. Chicken wings were immersed in solutions containing 1% individual acids for 10 min. Exposure for 10 min significantly reduced (P < 0.05) APC on the surface of chicken wings for 12 days. AA had greater antimicrobial activity than LA or CA. AA treatment yielded lighter, less red, and less yellow colored wings than untreated controls. Odor scores of chicken wings treated with acids were lower than untreated controls, with AA giving better scores than the other acids during 12 days of storage. Appearance scores of acid‐treated wings were similar to controls throughout storage. Untrained panelists did not observe color differences suggested by Hunter color data. Treatment of chicken wings with 1% AA would be recommended over the other acids due to greater antimicrobial effect and more favorable sensory results.     

ORGANIC ACIDS PROFILE IN TOMATO JUICE BY HPLC WITH UV DETECTION

A simple method was developed to determine 10 organic acids simultaneously in tomato products using reverse‐phase high performance liquid chromatography (HPLC) column with the diode array detector set at 210 nm. After centrifugation and filtration, the samples were passed through to an anion exchange resin and the organic acids were released using 0.1 N HCl. The chromatographic separation was achieved with isocratic analysis in a 20‐min run. The method was reliable and sensitive. The coefficient of determination of the standard calibration curve is 0.9925 ≤ r² ≤ 0.9999 and the limit of detection ranged from 0.08 to 6.00 mg/kg for trans‐aconitic acid and acetic acid, respectively. The limit of quantification ranged from 0.19 to 15.18 mg/kg for trans‐aconitic and acetic acid, respectively. To establish the efficiency of the anion resin the procedure was applied to a standard solution of a mixture of organic acids. The organic acids recovery ranged from 87.0% ± 1.9 for citramalic acid to 109.9% ± 5.2 for fumaric acid.     

米质判定器在粮食感官检验方面的应用

通过对粮食辅助检验中观察所用光源、检验平台及平台背景色等因素进行分析、研究和实验,结合相关感官检验方面的有关参数,找出了适合粮食感官检验所需的光源强度、透视方式、适合不同检验项目的平台背景色,研发出适合进行粮食辅助检验用的米质判定器。米质判定器的推广和应用将为提高我国粮食感官检验水平提供有力的技术支持,可以更好的贯彻优质优价、按质论价政策,促进我国粮食标准与国际粮食检验标准接轨。着重介绍了米质判定器的结构、特点和技术指标及其应用。     

响应面方法在优化微生物培养基中的应用

多种统计优化方法已被成功地运用于微生物培养基优化工作中，本文根据响应面分析法的基本原理，针对响应面方法的优，点、试验设计的方法以及实验数据的处理进行了简述，并结合里氏木霉RutC-30发酵生产纤维素酶培养基成分的确定说明了响应面方法的具体应用。     

DETECTION OF WILD YEASTS IN THE BREWERY EFFICIENCY OF DIFFERENTIAL MEDIA

The efficiency of five differential media in the detection of wild yeasts was compared. On the basis of the types of wild yeast they are able to detect, these differential media were classified into two groups. Group I consists of actidione medium and lysine medium, and is suitable for the detection of non-Saccharomyces wild yeasts. In this group, the lysine medium detected more species and a higher percentage of wild yeasts than the actidione medium. Group II consists of crystal violet medium, SDM, and Lin's medium, and is suitable for the detection of Saccharomyces wild yeasts. In this group, Lin's medium is superior to crystal violet medium and SDM for wild yeast detection. It is suggested that lysine medium and Lin's medium be employed together for the detection of wild yeasts in the brewery.