Global Stability Index方法在大骨鸡保质期预测中的应用

目的:建立了基于全面稳定性指数(global stability index,GSI)理论预测庄河大骨鸡保质期的新方法。方法:基于恒温加速实验,测定大骨鸡于4、10、20、30℃储藏温度下的感官、汁液流失率、菌落总数和挥发性盐基氮变化规律,建立大骨鸡GSI保质期预测模型。结果:计算得到的GSI值满足零级动力学模型。活化能和指前因子分别为25.52 kJ/mol和11027。GSI实验值和预测值相对误差绝对值在10%范围内。通过GSI模型预测,获得大骨鸡在4、10、20、30℃下的保质期分别为5.9、4.7、3.2、2.3 d。结论:建立的GSI预测模型在4~30℃储藏温度范围内能够有效预测大骨鸡的新鲜度。     

全面稳定性指数理论在河豚保质期预测中的应用

目的 建立一种基于全面稳定性指数(global stability index,GSI)理论预测河豚保质期的新方法.方法 基于恒温加速实验,测定河豚在0、4、7和10℃储藏温度下的感官、菌落总数、挥发性盐基氮和K值变化规律,建立河豚GSI保质期预测模型.结果 计算得到的GSI值满足零级动力学模型.阿伦尼乌斯方程活化能和...     

化学反应动力学模型预测米糠的保质期

将米糠置于不同温度下进行储藏实验,探讨在保质期内,不同储藏温度对米糠酸价(AV)和过氧化值(POV)影响,以温度-AV/POV之间的一级化学反应动力学模型为基础,建立温度与保质期的关系式,预测米糠在不同储藏温度下的保质期。结果表明:米糠保质期(t)与储藏温度(T)之间存在对数关系,对数方程为:lnt=-0.031 3T+4.959 2。根据对数方程,代入不同的温度T,可推算预测相应的米糠保质期。     

不同储藏温、湿度条件下小麦粉脂肪酸值的变化

在6种温度(10、15、20、25、30、35℃)和3种相对湿度(55%、70%、85%)组合情况下进行小麦粉储藏试验。在90 d的储藏过程中,每10 d取一次样测定脂肪酸值。结果表明:55%RH和70%RH条件下,储藏温度越高,脂肪酸值增长速率也越大,且相同储藏时间的小麦粉脂肪酸值也越大。在85%RH的条件下,10℃和15℃下储藏的小麦粉脂肪酸呈直线上升趋势,20、25、30、35℃下储藏的脂肪酸在储藏初期都呈上升趋势,然后均出现不同程度地下降,储藏温度愈高,下降速度愈大;另外,分别在55%RH、70%RH和85%RH条件下,就储藏温度和储藏时间对脂肪酸值的影响进行了方差分析,并建立了脂肪酸值与储藏温度和储藏时间关系的回归方程。     

可食用膜制备及在酱牛肉保鲜中应用的研究

分别以大豆蛋白和牛骨胶原蛋白为原料制成复合可食膜Ⅰ、Ⅱ对酱卤肉制品进行杀菌、真空包装等处理,通过测定TBA值、TVB-N值、菌落总数、感官指标,研究其在不同温度(35、20、4℃)下的保质期。实验结果:在35℃条件下,Ⅰ、Ⅱ组的保质期分别为40、50d,对照组为30d;在20℃条件下,Ⅰ、Ⅱ组的保质期分别为120、140d,对照组为80d;4℃条件下,Ⅰ、Ⅱ组的保质期分别为200、210d,对照组为140d。实验结果表明,经过大豆蛋白复合可食膜、牛骨胶原蛋白复合可食膜处理后,酱卤肉的保质期均优于对照组,牛骨胶原蛋白可食膜的保质、保鲜效果优于大豆蛋白可食膜。     

玉米储藏真菌早期预测的研究

对玉米储藏水分和温度的变化与真菌生长关系进行了研究,建立了1种玉米储藏真菌危害早期预测的方法。将水分为12.2%、12.9%、13.5%、13.9%、14.7%、15.7%的玉米样品分别置于10、15、20、25、30、35℃6个温度下储存180 d,每10 d取样检测真菌生长情况。结果表明,12.2%水分玉米在6个实验温度下未检出真菌生长。12.9%水分玉米在30℃和35℃高温条件下储藏半年,储藏后期有少量真菌检出,但对储藏品质影响较小,基本可保证储藏安全。13.5%水分的玉米在25℃及以下和13.9%水分玉米在20℃条件下储藏半年是安全的。14.7%和15.7%水分玉米在20℃及以上储藏均有真菌生长检出,水分越升高,真菌生长逐渐加快。15℃以下低温储藏对真菌生长有一定抑制作用。对不同水分玉米的储藏温度与真菌生长起始时间进行了幂函数拟合,得到了玉米储藏水分、温度与真菌起始生长时间的预测关系曲线,通过此曲线可对高水分玉米短期安全储藏期进行预测。     

甘蓝型油菜籽水分解吸等温线及热力学性质

为了提高油菜籽储藏期间的稳定性,延长其保质期。采用静态称量法对油菜籽在20、30、40℃温度条件下的解吸特性进行研究,将实验数据用5种常见数学模型进行拟合并对最佳模型进行解析。采用净等量吸附热(q_(st))、扩张压力(Φ)、微分熵(ΔS)、净积分焓(q_(in))、净积分熵(ΔS_(in))以及焓熵互补等特征参数对其热力学性质进行描述。结果表明,油菜籽等温线属于Type Ⅱ类曲线,油菜籽的平衡含水率与水分活度呈正相关,一定水分活度下,平衡含水率与温度呈负相关;描述水分活度与平衡含水率关系最佳模型为GAB模型,不同温度条件下模型决定系数R~2的平均值为0.993 7,卡方x~2的范围为1.396 5×10~(-5)～0.778,残差平方和RSS最低值为4.189 6×10~(-6);较高Φ值能提高干燥速率,储藏过程中,较低Φ值能延长物料保质期;对ΔS_(in)与平衡含水率的关系分析得到最低ΔS_(in)值,在20、30、40℃条件下,籽粒内结合水和单分子层吸附水分子最稳定的平衡含水率分别为5.03%、4.92%以及4.88%。     

不同储藏温、湿度对稻谷霉菌生长的影响及生长预测模型的建立

实验以粮仓中安全水分稻谷为研究对象,探究稻谷在不同储藏温、湿度中的霉菌生长规律,采用Logistic方程拟合稻谷霉菌在不同储藏条件下的生长动力学模型,并对模型的适用性进行评价。结果显示,在20℃及以下,霉菌数量增长缓慢,稻谷处于安全状态;25℃时,43%和75%的湿度为安全储藏条件;30℃时,仅43%的湿度为安全储藏条件;40℃时稻谷霉菌数量变化较小。Logistic方程所拟合出的各个储藏条件中霉菌生长方程的决定系数R~2为0.987±0.017,适用于描述稻谷中霉菌的生长曲线。结合B_f和A_f值,同一温度下,环境相对湿度越高,模型的准确性越低;在10～30℃范围内,随着温度的升高,模型准确性下降。     

冷鲜排骨中热杀索丝菌生长预测模型初步研究

选取0℃、5℃、10℃、15℃和20℃作为储藏冷鲜猪肉排骨的试验温度,对其中的热杀索丝菌进行定量研究,并建立热杀索丝菌的生长动力学模型。试验结果表明,利用Gompertz模型拟合0℃～20℃下热杀索丝菌的生长,相关系数R2均大于0.99,计算得到总的偏差因子和准确因子分别为1.13和0.91;利用平方根模型拟合了温度与最大比生长速率和延滞期的关系,二者都呈现了良好的线性关系,表明该平方根模型描述的温度与最大比生长速率和延滞期的关系可行;由此建立的0℃～20℃范围内冷鲜猪肉排骨中热杀索丝菌的生长预测模型有比较好的预测效果。     

浓缩乳储藏特性和保质期预测

以冷冻浓缩乳（储藏温度为-18℃）和冷藏浓缩乳（储藏温度为2℃）在储藏期内不同时间段作为研究对象,通过描述性感官评价,理化、微生物、毒素、卫生指标测试,酸稳定性和热稳定性实验,研究冷冻浓缩乳和冷藏浓缩乳储藏期特性,并预测其保质期。结果表明,在储藏期内冷冻浓缩乳随着时间的延长,感官评价属性总体接受度下降,保质期预测为24个月;冷藏浓缩乳随着储藏时间的延长,酸度、嗜冷菌、酵母菌数量逐渐增多,保质期预测为0.5个月。本文分析冷冻和冷藏浓缩乳储藏特性及预测保质期,旨在为后续优化生产工艺和提升浓缩乳品质等方面提供科学的理论依据。     

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.     

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.