香梨与瓦楞纸板跌落碰撞的接触应力分布分析及损伤预测

为了实现香梨果实跌落碰撞时损伤面积的准确评估和预测,本研究采用Prescale感压胶片对香梨与瓦楞纸板不同高度跌落碰撞下的接触应力分布进行测量分析,探讨接触应力分布与损伤面积的关系,确定了最接近损伤面积的应力面积范围。并在此基础上采用有限元模拟方法对香梨碰撞瓦楞纸板的损伤面积进行预测分析。研究结果表明,感压胶片测量的接触应力分布中0.20 MPa范围的应力面积与损伤面积最为接近,相对误差率平均为6.81%。当该应力范围应用于有限元模拟的损伤面积预测时,香梨损伤面积的预测值略高于实际损伤面积,损伤预测的相对误差率平均约为13.29%,显著提高了预测精度,实现了有限元法对香梨与瓦楞纸板跌落碰撞损伤面积的较准确地预测,为今后香梨机械化作业中减损设计提供了研究基础。     

鲜切苹果品质保持研究

文研究了不同褐变抑制剂对鲜切苹果PPO活性、褐变度、感官品质的影响。试验结果表明:单一的1.5%L-半胱氨酸、1.0%D-异VC钠、1.0%谷胱甘肽处理均能较好地抑制鲜切苹果褐变。采用0.10%D-异VC钠+0.12%谷胱甘肽+0.13%L-半胱氨酸,浸泡2min的复合处理,可使鲜切苹果的PPO活性、褐变度、感官品质在14d内保持较优水平。     

苹果静压接触应力分布特性的测量分析

为了了解不同成熟度苹果在不同曲率半径位置静压时的接触应力分布特性,本文采用Prescale感压胶片对苹果静压接触应力分布进行了测量分析和Hertz公式理论计算,并探讨了Hertz公式关于接触应力面积计算的精度以及修正方法。研究结果表明,苹果静压接触应力分布轮廓为近椭圆形,不同应力呈高低相间的不连续分布,低应力(≤0.2 MPa)主要在边缘分布,高应力(0.5 MPa)只有零星分布,可忽略不计。当压力100 N以上时,两种成熟度苹果的应力面积有显著性差异。随着曲率半径增大,相同压力水平下苹果的应力面积因成熟度不同而表现出不同程度的增大趋势。接触应力面积的Hertz公式计算值与感压胶片测量值存在不同程度偏差,当引入λ=1.5780-0.0042F修正Hertz公式的等效弹性模量E*,可明显提高苹果静压接触应力面积的理论计算精度。     

混浊苹果汁加工过程中的的酶促褐变及其防止的研究

将几种可用于食品的防褐变剂在苹果破碎时加入,考察了它们对苹果浆和苹果鲜榨汁的防褐变效果及它们之间的协同作用.半胱氨酸、抗坏血酸、曲酸、氯化钠和氯化钙都是较好的防褐变剂.在所测试条件下,抗褐变的能力(褐变抑制率)为0.1%的抗坏血酸＞0.1%的偏重亚硫酸钠＞0.1%的曲酸＞0.1%的氯化钙＞0.005%半胱氨酸＞0.1%氯化钠.它们抗褐变能力都表现为浓度依赖型,特别是抗坏血酸.柠檬酸在所测试条件下没有抗褐变效果.0.044%NaCl+0.0125%Vc的组合较经济且可使果汁40min不变色.果浆脱气可减缓其褐变;减小果汁及果浆与空气的接触面也可防止褐变.     

马齿苋提取物对鲜切苹果褐变的影响

酶促褐变是影响鲜切果蔬品质及商业价值的关键问题之一。为探究马齿苋提取物在果蔬保鲜方面的应用价值,以鲜切苹果为研究材料,采用质量分数0.05%马齿苋提取物溶液浸泡鲜切苹果5min,在(4±1)℃存放8d。以鲜切苹果的褐变指数、多酚氧化酶(polyphenol oxidase,PPO)活力、苯丙氨酸解氨酶(phenylalanine ammonia-lyase,PAL)活力、过氧化氢酶(catalase,CAT)活力、过氧化物酶(peroxidase,POD)活力、丙二醛(malondiadehyde,MDA)含量、抗坏血酸含量以及DPPH自由基清除能力为评价指标,分析马齿苋提取物对鲜切苹果褐变及贮藏品质的影响。结果表明:与蒸馏水对照组相比,马齿苋提取物溶液处理能有效抑制鲜切苹果的褐变程度,在降低POD、PPO和PAL活力方面也有明显效果,能够在保证膜完整性的基础上减少细胞膜出现的损伤。相关性分析表明:鲜切苹果的褐变指数与CAT活力、抗坏血酸含量、DPPH自由基清除能力呈现极显著负相关(P<0.01),与MDA含量、PPO活力、POD活力、总酚含量呈极显著正相关(P<0.01)。马齿苋提取物溶液处理的鲜切苹果抗褐变效果较好,同时贮藏后鲜切苹果的抗氧化能力也有一定提高。     

鲜切苹果抗褐变研究

研究了不同褐变抑制剂对鲜切苹果PPO(多酚氧化酶)活性、褐变度、感官品质的影响。试验结果表明单一的1.5%L-半胱氨酸、1.0%D-异VC钠、1.0?TA-2Na处理均能较好地抑制鲜切苹果褐变。采用0.10%D-异VC钠 0.12?TA-2Na 0.13%L-半胱氨酸,浸泡2min的复合处理,可使鲜切苹果的PPO活性、褐变度、感官品质在14d内保持较优水平。     

鲜切马铃薯褐变抑制的研究

为了提高鲜切马铃薯的品质,本文通过单因素试验和正交试验分别研究了焦亚硫酸钠、柠檬酸、L-半胱氨酸、CaCl_2、异抗坏血酸钠、EDTA-2Na对马铃薯在鲜切过程中的酶促褐变影响。单因素试验结果表明:抑制马铃薯褐变的试剂的最佳浓度分别是焦亚硫酸钠0.10%,柠檬酸0.20%,L-半胱氨酸0.10%,CaCl_20.10%,异抗坏血酸钠0.10%,EDTA-2Na0.10%;正交试验结果表明:当选取柠檬酸、L-半胱氨酸、CaCl_2、异抗坏血酸钠作为抑制剂和以鲜切马铃薯的最低褐变度为目标值时,经过试验并将其结果进行参数优化获得其最佳方案是:柠檬酸0.40%+L-半胱氨酸0.15%+异抗坏血酸钠0.30%+CaCl_2 0.40%。以此方案进行试验验证,测得样品的平均褐变度仅为0.071,表明该方案可有效抑制马铃薯的酶促褐变,保证鲜切马铃薯的新鲜品质。     

浓缩苹果汁中5-HMF和还原糖含量变化及其与浓缩汁褐变关系研究

以“澳洲青苹”的浓缩苹果汁为实验材料,研究不同程度褐变的浓缩苹果汁在贮藏过程中5-HMF和还原糖与浓缩苹果汁的褐变关系。结果表明,在贮藏过程中,不同程度褐变的苹果浓缩汁5-HMF含量变化趋势不同,轻度、中度程度褐变的苹果浓缩汁5-HMF含量先上升后下降;而重度褐变的浓缩苹果汁先下降后上升,再上升。不同程度褐变的浓缩苹果汁5-HMF含量出现的峰值差别较大,中度程度褐变的浓缩苹果汁5-HMF含量的峰值最大,轻度褐变的最小。不同程度褐变的苹果汁还原糖含量的变化趋势差别不大,而苹果浓缩汁色差值(DE)都呈上升趋势,但其增加值不同,重度褐变的色差值(DE)的增加值最大,轻度褐变的最小。     

三种天然食品添加剂对鲜切苹果褐变抑制效果的研究

为研究大豆分离蛋白、海藻酸钠和壳聚糖三种天然食品添加剂对鲜切苹果褐变的抑制作用，通过单因素及响应面试验筛选确定三者复合的最佳条件，初步探讨了其对鲜切苹果褐变程度、可溶性醌含量、多酚氧化酶（polyphenol oxidase,PPO）和过氧化物酶（peroxidase,POD）活性的影响。结果表明，由2.08%大豆分离蛋白、1.45%壳聚糖和2.00%海藻酸钠制得的复合抗褐变剂对鲜切苹果褐变程度的抑制效果最佳。鲜切苹果经复合抗褐变剂处理后在4℃条件下储藏，相比对照组褐变程度降低了40%，且鲜切苹果储藏期内PPO和POD酶活性被显著降低，同时可溶性醌含量的积累被抑制。因此，该复合抗褐变剂可有效延缓鲜切苹果酶促褐变的发生，起到提高鲜切苹果的外观品质和商品性的作用。     

响应面法优化“黄元帅”苹果浓缩汁防褐变工艺研究

针对"黄元帅"苹果浓缩汁贮藏期间易褐变的难题,以可溶性固形物含量为70.25%的浓缩苹果汁为实验原料,利用响应面分析法优化苹果浓缩汁制备及贮藏过程中的防褐变工艺,在单因素实验的基础上,以柠檬酸添加量、L-抗坏血酸添加量、L-半胱氨酸添加量和不同热烫温度为影响因子,苹果浓缩汁的褐变抑制率为响应值,通过BoxBenhnken中心组合设计原理,模拟得到二次多项式回归方程的预测模型,确定最佳防褐变工艺为:柠檬酸添加量0.12%、L-半胱氨酸添加量0.15%,热烫90℃,10min处理对苹果汁的褐变抑制率达到93.22%,与预测值相符。因此,采用RSA法优化得到的护色条件参数准确、可靠,具有实用价值,为苹果浓缩汁褐变调控提供理论依据。     

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.     

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.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the     

Chinese CTP Market

According to Printing and Printing Equipment Industries Association of China（PEIAC）＇s statistics to the plate manufucturer in China, in 2013, the actual offset plate production has reached 346 million square meters in China. Among them, the CTP production volume was 245 million square meters, up by 11% than that of last year; the total sales of the CTP plate was 239 million square meters, up by 13%.     

Preparatory Work of Print China 2015 is Going Smoothly

正Held at Guangdong Modern International Exhibition Center,Print China 2015 will cover 7exhibition halls,besides the original Hall No.3,4,5,6,7,the newly built F zone of Hall 3 will be used too.The total area will be140,000 square meters.Hall 3:Offset and large printing equipment,package printing equipment,post press     

INFOPRINT 2014 was Successfully Held in Dongguan

Sponsored by Printing and Printing Equipment Industries Association of China （PEIAC） and organized by Print China magazine, the Seventeenth Beijing International Printing Information Conference （INFOPRINT 2014） was successfully held on 11th Dec. 2014 at Dongguan Exhibition International Hotel.