复合酶法脱除生姜皮的新工艺研究

对传统生姜去皮工艺进行改进,研究复合酶解法去除生姜皮的新工艺条件。试验以去皮效果为评价指标,通过单因素试验初步确立复合酶复配比例、料液比、酶浓度、酶解温度、时间及p H,再通过正交试验对生姜去皮的最佳酶解工艺进行优化。试验结果表明,生姜去皮的最佳酶解工艺条件为:果胶酶与纤维素酶的复合比例为1∶2.5(g/g),料液比(生姜∶酶解液)为1∶3(g/m L),酶浓度为0.40%,酶解温度为40℃,酶解p H值为4,酶解时间为50 min。     

双酶法提取蓝靛果果渣中花色苷酶解条件的研究

为研究从蓝靛果果渣中酶法提取花色苷的工艺参数,通过单因素和正交试验确定纤维素酶、果胶酶单独水解和双酶复合水解条件.结果表明:采用纤维素酶水解的最佳条件为:温度30℃,时间120 min,固液比1:8,酶用量10 mg/g,pH 4.5;采用果胶酶水解的最佳条件为:温度50℃,时间120 min,固液比1:6,酶用量8 mg/g,pH4.0.采用双酶复合水解比单独使用纤维素酶花色苷提取率提高3.05倍,比单独使用果胶酶花色苷提取率提高1.53倍;先使用纤维素酶再使用果胶酶,花色苷提取率比先使用果胶酶再使用纤维素酶提高1.06倍.     

复合酶辅助浸提绿茶多酚工艺条件优化

采用纤维素酶+果胶酶的复合酶法在较适温度下辅助浸提绿茶多酚,以茶多酚浸提率为考察指标,通过单因素和正交实验优化了酶添加量、料液比、浸提温度和浸提时间等四个浸提条件因素,确定了最佳浸提工艺条件为:纤维素酶和果胶酶分别添加0.3%,料液比1∶40 g/m L,浸提温度50℃,浸提时间45 min;在此条件下茶多酚浸提率可达21.36%,明显高于传统水提法的茶多酚浸提率17.41%。     

纤维素酶及果胶酶法提取紫薯花色苷的工艺优化

紫甘薯花色苷含量丰富,性质稳定,是良好的天然色素来源。利用纤维素酶及果胶酶辅助提取紫薯花色苷,对2种酶的提取条件进行了优化。经过单因素及正交试验,确定了纤维素酶解辅助提取花色苷的最佳工艺为:p H为6.0、温度为30℃、加酶量0.25 g/g、固液比1:55、提取时间1.75 h,此条件下提取花色苷的得率为24.8 mg/100 g;果胶酶辅助提取花色苷的最佳工艺为:p H为6.0、温度为40℃、加酶量0.5 g/g、料液比为1:60、酶解时间2 h,此条件下提取花色苷得率为28.6 mg/100 g;果胶酶辅助提取花色苷的效果优于纤维素酶。     

复合酶处理对金童5号黄桃去皮效果的影响

对复合酶法黄桃(金童5号)酶解去皮工艺进行研究,在单因素试验基础上,以m(果胶酶质量)∶n(纤维素酶质量)=1.5∶1配制复合酶,以酶解液质量浓度、pH值、温度、时间为试验因素,选用L16(45)正交表优化黄桃复合酶法去皮的工艺.结果表明:在酶质量浓度为0.55 g/L、pH值为3.5、酶解温度为45℃的条件下,经45 min酶解后,黄桃去皮率达到100％,色泽金黄,外形光滑,质量安全,营养成分保存率达到96％以上.     

嫩竹酶促糖化工艺研究

为了提高在饮料或果酒酿造中的附加值,用纤维素酶、果胶酶、淀粉酶等对嫩竹液进行糖化处理,以期提高其出汁率.研究表明通过酶解可以大幅度提高嫩竹液的可溶性固形物含量,最佳工艺为:纤维素酶6000U/100 g、果胶酶2000U/100 g联合在pH为4.25、45℃～50℃作用50 min后,再用2 500U/100 g的淀粉酶在60 ℃、pH6下作用90 min;在最佳工艺条件下嫩竹中的可溶性固形物含量可达15%以上,是对照组的2.2倍.     

双酶法提取赤霞珠酿酒葡萄皮渣白藜芦醇工艺优化及抗氧化性研究

以赤霞珠酿酒葡萄皮渣为原料,研究双酶法（纤维素酶和果胶酶）辅助浸提白藜芦醇工艺的最佳条件及其体外抗氧化活性。通过单因素试验及正交试验考察纤维素酶添加量、果胶酶添加量、酶解温度、酶解时间、液固比对白藜芦醇浸提工艺的影响。结果表明,最佳白藜芦醇浸提工艺为纤维素酶和果胶酶添加量分别为2.5%和1.2%,酶解温度为45 ℃,酶解时间为100 min,液固比为30∶1（mL∶g）。在此优化条件下,白藜芦醇得率为927 μg/g干质量。体外抗氧化试验结果可知,在质量浓度0.1～0.5 mg/mL的范围内,白藜芦醇对DPPH·和·OH的清除作用较好,最大清除率分别达到83.1%和74.0%。     

响应面法优化酥李果汁的酶法提取工艺

目的:研究酶解提取酥李果汁的最佳工艺条件,为李深加工利用提供理论参考。方法:以酥李出汁率为指标,在单因素实验基础上采用响应面试验优化,对单一果胶酶、单一纤维素酶、复合酶（果胶酶和纤维素酶）提取酥李果汁的工艺条件分别进行优化。结果:不同加酶方式中对酥李出汁率的影响因素顺序均为酶解温度>加酶量>酶解pH>酶解时间;果胶酶酶解提取酥李果汁的最佳工艺条件为:加酶量0.45 g/L、酶解温度38 ℃、酶解pH3.8、酶解时间72 min,出汁率提高27.13%;维素酶酶解提取酥李果汁的最佳工艺条件为:加酶量0.55 g/L、酶解温度41 ℃、酶解pH4.2、酶解时间105 min,出汁率提高20.18%;复合酶酶解提取酥李果汁的最佳工艺条件为:果胶酶添加量0.45 g/L、纤维素酶添加量0.55 g/L、酶解温度41 ℃、酶解pH4.0、酶解时间87 min,出汁率提高31.79%。三种加酶方式中,回归模型均能较好地反应相应酶制备酥李果浆的出汁率,所得工艺合理可靠。结论:在酶法提取酥李果汁过程中,果胶酶和纤维素酶的不同添加方式均能有效提高酥李出汁率,其中采用复合酶提取酥李果汁效果最佳。本研究成果为贵州李产品开发提供了一定的技术参考。     

两次压榨与酶解结合提取菠萝果汁工艺技术研究

本文研究了果胶酶和纤维素酶对菠萝出汁率的影响.最适工艺条件为:果胶酶(活力单位为353.13 U/mL)用量为0.05%,纤维素酶(活力单位为10000U/g)用量为0.025%,时间为1 h,温度为35℃.同时对不同提汁工艺对菠萝渣出汁率的影响进行了研究,确定二次压榨与酶处理结合提汁法可以提高出汁率15.94%.     

复合酶法提取石榴皮多糖的工艺研究

对复合酶(纤维素酶、果胶酶和木瓜蛋白酶)提取石榴皮多糖的工艺条件进行研究。以陕西临潼石榴皮为材料,运用正交试验法确定了复合酶的最佳加入量配比。比较了酶解时间、温度、pH以及液料比对多糖得率的影响,通过正交试验确定了最佳酶法提取条件。结果表明复合酶的最佳加入量配比为:纤维素酶120 U/g,果胶酶150 U/g,木瓜蛋白酶90 U/g;提取因素对多糖得率的影响大小为:pH温度时间料液比;最佳酶解提取条件为:浸提时间为120 min、温度为53℃、浸提液pH为4.6、料液比为1:55 g/m L。此条件下石榴皮多糖得率为6.01%。此法可使石榴皮多糖得率比传统水提法提高2倍,是一种提取效率高、温和的多糖提取方法。     

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.