蛋白酶制剂对发酵牛肉酱风味物质的影响

以复合蛋白酶、木瓜蛋白酶、胰蛋白酶、风味蛋白酶分别酶解牛肉,得到牛肉酶解液,将4种牛肉酶解液分别和大曲混合后兑盐水发酵,比较不同蛋白酶制剂对发酵牛肉酱风味物质的影响。结果表明,添加复合蛋白酶组的总酸、氨基酸态氮和总氮含量分别为1.67 g/100 g、1.11 g/100 g和1.53 g/100 g,优于其他3种酶制剂组。添加复合蛋白酶和风味蛋白酶组的牛肉酱基质检出有机酸7种,提高了丙酸、酒石酸、苹果酸和琥珀酸的含量。在风味物质种类及含量方面,添加复合蛋白酶组检出67种,在酯类、醇类及酸类的种类和含量上比添加其他酶制剂组略有优势。     

蓝圆鲹蛋白水解条件的优化

确定了中性蛋白酶、木瓜蛋白酶单酶酶解蓝圆缪蛋白的适宜条件，比较了单酶与双酶的复合酶解效果，利用正交试验确定了双酶复合酶解的最佳水解条件。结果表明：木瓜蛋白酶和中性蛋白酶同时加入酶解蓝圆碜蛋白的效果最好，最佳的水解条件下的酶解液中氨基酸态氮含量可达2．48g／L、氮回收率为91．27％。     

羊骨汤不同酶解方式对其成分的影响

将羊骨以1：1的骨水比于0．05MPa高压2．0h后，再以不同的酶、酶浓度和酶解时间酶解骨汤，分析水解度（DH）、肽链长度（PCL）及游离钙含量的变化，并各筛选最优方案。结果表明：①游离钙含量最高：中性蛋白酶，酶浓度1500U／L，酶解6h；②DH最高：胰蛋白酶，酶浓度1：100，酶解6h；③PCL值最低：胰蛋白酶，酶浓度1：125，酶解6h；PCL值最高：碱性蛋白酶，酶浓度1500U／L，酶解8h。     

耐盐酵母菌对鳕鱼骨酶解液风味的改善作用

以鳕鱼骨为原料制备酶解液,研究发酵时间、发酵温度、加盐量对酶解液氨基酸态氮含量和感官品质的影响。利用电子鼻结合顶空固相微萃取(HS-SPME)和气相色谱-质谱联用仪(GC-MS)分析酶解液发酵前、后挥发性风味物质。结果表明,酶解液的最佳发酵温度为35℃、发酵时间12 h、加盐量15%。在此发酵条件下,酶解液的氨基酸态氮含量为0.2685 g/100 mL,氨基酸总量为6177.28 mg/100 g,其中鲜味氨基酸谷氨酸和天冬氨酸含量较高。通过电子鼻主成分分析(PCA)可以很好地区分发酵前、后酶解液的风味。用SPME/GC-MS检测发酵后酶解液中香气活性化合物明显增加,从发酵液中共检测到18种香气活性化合物,其中醇类6种、醛类4种、吡嗪类3种、酮类2种、呋喃类2种、酚类1种。     

骨肉酶解工艺条件研究

为了进行猪骨肉的综合利用,本实验以猪骨为原料,研究木瓜蛋白酶、中性蛋白酶和胰蛋白酶的水解效果以及最适蛋白酶的酶解温度、pH、酶用量、料液比和酶解时间对骨肉蛋白水解度和总氮回收率的影响。结果表明：胰蛋白酶为最佳骨肉水解酶,胰蛋白酶水解猪骨的最佳工艺参数为：酶解时间为5h、酶解温度60℃、pH8、酶用量5000U／g原料、料液比为1：5。     

蛋白酶处理对鸡骨泥营养组成的影响

研究了蛋白酶处理对鸡骨泥营养组成的影响。研究结果表明,木瓜蛋白酶适合用来水解鸡骨泥以提高游离氨基酸及钙的含量,其最优水解条件为:60℃,pH 6.5条件下,取浓度为50%的粗鸡骨泥,按照加酶量3000 U/g加入木瓜蛋白酶,水解5 h后,鸡骨泥水解液中游离氨基酸及游离钙含量分别可以达到2.0365 mg/g和0.9856 mg/g。适当微波加热预处理可以改善木瓜蛋白酶对粗鸡骨泥的水解作用。     

钦州牡蛎酶解条件的优化研究

本文以钦州牡蛎为原料,以氨基酸态氮的含量为指标,通过对比实验来确定牡蛎酶解的酶种,并在单因素实验的基础上,通过正交实验来优化酶解工艺条件。结果表明:在胰蛋白酶、胃蛋白酶、木瓜蛋白酶、复合风味酶、复合蛋白酶5种酶中,胰蛋白酶为牡蛎酶解理想蛋白酶,根据单因素实验的结果,确定了通过4因素、3水平正交实验来优化酶解的条件,其结果为:pH 8.5,温度45℃,酶用量350 U/g,底物浓度22%,在该条件下得到的酶解液的氨基氮含量最高,每克底物水解产生氨基酸态氮14.19mg。     

甲鱼生物饮料加工技术研究

研究了采用枯草杆菌蛋白酶酶解甲鱼的条件。正交试验分析结果表明:酶解甲鱼的最佳条件是酶用量(E/S)144mg/kg,温度45℃,pH值为7.0时酶解4h,甲鱼酶解液的氨基酸态氮含量由0.0369g/kg增加到0.2265g/kg,增加了6倍;游离氨基酸由51.1g/kg增加到503.3g/kg,增加近10倍。但酶解液中含有大量苦味氨基酸和苦味多肽成分,经接入30g/kg嗜热链球菌(S.t)和保加利亚杆菌(L.b)于42℃发酵4h后,酶解液中苦味天冬氨酸在发酵后减少了近10倍,酶解液风味得到明显改善,苦味基本消失并产生了特殊的发酵香味。甲鱼生物饮料配方是:甲鱼酶解发酵过滤液80g/kg,麦芽糖浆30g/kg,蔗糖45g/kg,稳定剂3g/kg,固形物含量为750g/kg的浓缩果汁80g/kg,酸味调节剂和香精适量。     

黄鳍金枪鱼头蛋白酶解条件的研究

确定了中性蛋白酶、木瓜蛋白酶、风味酶两两组合双酶水解金枪鱼头蛋白的最佳组合,利用正交试验探讨了酶浓度、温度、水解时间对双酶水解效果的影响,确定了最佳的水解条件。结果表明:木瓜蛋白酶和中性蛋白酶双酶同时水解金枪鱼头蛋白的效果最好;最佳水解条件下水解液的氨基酸态氮含量为126.53mg/100mL,氮回收率为80.2%;水解液氨基酸分析表明,水解液的氨基酸总量为4.12g/100mL,其中必需氨基酸占36.04%,游离氨基酸为0.81g/100mL。     

混合菌种发酵鸡骨泥香精基料工艺条件优化

为充分开发鸡骨的利用价值，该研究以鸡骨泥酶解基料为原料，使用植物乳杆菌和戊糖片球菌对其进行发酵处理，分析不同菌种配比、发酵温度、发酵剂接种量和发酵时间对发酵液氨基酸态氮含量、多肽含量、游离氨基酸含量以及感官评分的影响，采用单因素实验和响应面实验对发酵过程工艺条件进行优化。结果表明，发酵温度对发酵效果的影响最显著，其次是发酵剂接种量，最后是发酵时间，优化后最佳发酵温度为33℃,发酵剂接种量为6%,发酵时间为49 h。经过验证实验，得到氨基酸态氮含量为0.222 1 g/100 g,多肽含量为2.784 g/100 g,总游离氨基酸含量为67.79 mg/100 g。该研究建立的发酵工艺可为酶解发酵工艺提供技术参考，为肉制品副产物的资源化利用提供一定的理论依据。     

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.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

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.     

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.     

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.