浓香型白酒产糖化酶菌株筛选及产酶条件研究

利用透明圈法从浓香型白酒曲房空气中筛选得到1株产糖化酶能力较强的菌株（J8M．53）,液体培养96h后,糖化酶活性可以达到887u／mL。研究发酵条件对该菌株产糖化酶能力影响,结果表明：虽然该菌株产糖化酶的最适初始pH值、培养温度和最佳碳源分别为5℃、30℃和可溶性淀粉,但在pH值为4,培养温度为40℃时酶活依然保持在较高的水平,且菌株对其他各碳源都有一定的利用。该菌株属于好氧菌或者兼性厌氧菌,对氧的需求量较大。另外,该菌株对酒精有一定的依赖性,并具有较强的耐酒精能力,当培养液中酒精浓度6％vol时,菌株的糖化酶活性最高,酒精浓度为12％vol时的糖化酶活性是最大值的74％。     

一株马克斯克鲁维酵母菌的生长及酒精发酵特性分析

该文对一株耐高温的马克斯克鲁维酵母菌株HY32的生长及酒精发酵特性进行了研究.与耐高温酿酒活性干酵母TRADY相比,菌株HY32表现出了极好的耐热能力和较好的耐酒精能力.在37℃、42℃、45℃摇瓶培养10h后,菌株HY32的活菌数分别为2.45× 108个/mL、1.76× 108个/mL和0.92× 108个/mL.将菌株TRADY和HY32按相同的接种量转接到添加了4％vol乙醇的液体培养基中,37℃摇瓶培养6h后,菌株HY32的OD600值是菌株TRADY的1.6倍.随着温度的升高和培养基中乙醇浓度的增加,菌株HY32较TRADY的相对耐酒精能力更好.菌株HY32在高温下仍具有一定的产酒能力.采用葡萄糖酒精发酵培养基进行酒精发酵,菌株HY32在42℃和45℃时发酵72h,酒精产率分别为5.25％vol和4.02％vol.木薯酒精发酵实验结果分析表明,菌株HY32的乙酸乙酯产量是酿酒酵母TRADY的10倍左右,而正丙醇和乳酸乙酯等含量较低.     

酱油增香用耐盐酵母的分离及生长特性分析

从酱醪中分离筛选出2株耐盐产香酵母菌C5、C6,并对其耐盐性及牛长特性进行研究。试验结果表明,2株酵母菌均能耐受24％（w／w）NaCl浓度,其在低盐稀态发酵生酱油的最适生长条件为温度28℃～32℃,pH4．5～5．5,酒精含量O～1．2％vol,葡萄糖或果糖添加量2％-4％（w／w）。此外,结果显示,菌株C5的还原糖消耗能力、酒精耐受性和产酒精能力均强于C6。     

张弓老酒大曲中耐高温酵母菌的分离鉴定及发酵条件优化

为筛选出耐高温的酵母菌,本实验利用传统微生物学分离培养方法,从张弓老酒中高温大曲中共初筛分离出100株酵母菌,进行复筛得到一株能在45 ℃下生长的酵母菌,编号为ZG-3,通过形态学特征观察并结合26S rDNA序列分析确定菌株ZG-3为库德里阿兹威毕赤酵母(Pichia kudriavzevii)。用常规方法对其耐高温和耐乙醇性以及乙醇发酵性能进行测试。研究表明菌株ZG-3的最适生长温度为37 ℃,最高生长温度为45 ℃,乙醇耐受性可达12%,在40 ℃条件下发酵72 h,产酒精4.7% vol。对菌株ZG-3发酵条件进行响应面优化,在最佳发酵下条件,即接种量12%、发酵温度40 ℃、pH为5、葡萄糖浓度140 g/L,发酵72 h,酒精度为5.2% vol。由此可见ZG-3是一株很有应用开发潜力的耐高温耐乙醇的酵母菌。     

苹果白兰地发酵酵母菌株的筛选及其性能研究

以在云责高原上所种植的青苹果为研究对象,从其自然发酵醪中分离得到10株菌种.通过产气能力、耐性试验、产酒精试验三级筛选得到1株适合苹果白兰地发酵的酵母菌,命名为GN-1.结果表明,该酵母菌可耐受16 ％vol乙醇,可耐糖浓度为750 g/L,发酵初始糖度为14°Bx,发酵液的酒精度为8.3 ％vol;该酵母菌发酵性能的试验结果显示,其最适生长温度为34℃,最适生长pH值为4.0～6.0.     

野木瓜酵母菌株抗性及发酵特性评价

以从野木瓜自然发酵过程中筛选出的8株发酵力强、产香好的酵母菌,对其进行抗性（温度耐受性、葡萄糖耐受性、酒精耐受性等）评价。供试菌株中,在NaCl浓度为140 g/L时,有4株菌仍可生长发酵并具耐高渗性,可用于高盐环境发酵中;菌株B7-2、C-4、BL-5的耐高温性较好,在55℃时仍可生长,可用于工业生产的高温环境;所有供试菌株都有很好的SO2耐受性,筛选的5株优良酵母模拟酒精发酵实验中,菌株C-4、B1-3产酒精度高于商品酵母RC212,可以作为优良酵母进一步开发利用。菌株B7-2产酒精度为0,但产香很好,可作为产香酵母在发酵过程中适量添加以增加香味,或者用于面包和无醇饮料的开发。     

植物乳杆菌对pH、酒精浓度和SO2浓度耐受性的研究

通过调整MRS培养基的pH、酒精浓度及SO2浓度,以菌株培养前后的菌密度差(△OD600nm)为指标研究了6株植物乳杆菌(Lactobacillus plantarum)对低pH、高SO2、酒精浓度及三者相互作用的耐受性.结果表明:试验所选取的6株菌都可耐受pH 3.0、75mg/LSO2浓度,其中有5株菌可耐受16％vol酒精浓度,3个因素对菌株生长影响的次序是SO2浓度＞pH＞酒精浓度.     

黑莓果酒发酵菌株的筛选和性能初探

从黑莓自然发酵物中经过三级分离筛选得到1株适宜黑莓果酒发酵的酵母菌,命名为CNBG001。该菌株在麦芽汁中的生长特性为：最适生长温度26℃,最适生长pH范围3．0～5．0,酒精耐受能力可达16％vol,耐SO2能力可达200mg/L,是1株优良的黑莓果酒酿造酵母。     

优良黄酒糖化菌株的选育

对黑曲霉出发菌株AS-3进行了紫外诱变、紫外-氯化锂复合诱变处理,将诱变所得菌株进行耐酸和耐酒精能力测定,筛选得到一株高产糖化酶活力的正向突变株UL-6,发酵培养56h后,产酶活力为15800u/ml,较同批发酵的AS-3提高了73.63%,且该菌株的耐酸、耐酒精性能良好。     

耐高酒精野生酵母菌株的筛选及其特性研究

以从内蒙古各旗县果园的果实和土壤中分离得到的200株酵母菌为出发菌株,经四级筛选最终得到一株酒精耐受力为16%vol的菌株K1-2,并对该菌株的发酵特性与生物学特性进行了研究。结果表明,该酵母菌的最适生长pH值为5.5,最适生长温度为28 ℃,最高可耐受600 mg/L的SO2,在葡萄糖含量为60%的条件下仍可生长。发酵5 d后糖醇转化率可达68.45%,产酒精度为6.4%vol,表明该菌株是一株具有良好酒精耐受性与发酵性能的酵母菌株,除拥有较高的耐SO2与耐高糖能力以外,还具备较强的产酒精能力,有很高的应用价值。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.