Technical note: A simplified procedure for myofibril hydrophobicity determination

A simple and reliable method for the determination of surface hydrophobicity of nonsolubilized myofibrils (from pig M. longissimus dorsi) was developed and validated. This method is based on the interaction of the hydrophobic chromophore bromophenol blue (BPB) with myofibrillar proteins and the separation of free and bound BPB by centrifugation. The titration of bound BPB is performed by absorption spectroscopy, and the amount of bound BPB is considered as an index of protein hydrophobicity. Heating, which is known to increase protein hydrophobicity, was performed in order to validate this method. Fixation of BPB to myofibrils increased with heating time and temperature, strongly suggesting that it may be closely related to protein hydrophobicity.     

绿豆在湿热处理及酶解过程中微量元素的分布分析

采用火焰原子吸收法对绿豆在湿热加工及分步酶解过程中微量元素的分布进行了分析,结果表明,室温下(7~12℃)浸泡对Mg、Zn和Mn的含量没有显著影响,对Fe、Cu和Ca的含量影响显著,但这种影响在浸泡23 h以后,基本与浸泡时间及过程中绿豆状态(皮裂开与否)无关,而热处理会加速Mg、Cu及Ca的流失。在分步酶解中提取出了绿豆中大部分的微量元素,其中淀粉酶酶解工序对各微量元素提取作用最小。与酶解制备饮料工艺相比,传统的“绿豆汁”工艺以及一些只喝绿豆汤而弃其渣的习惯对绿豆和绿豆中的各微量元素利用率不高。     

酰肼介导的抗体定向偶联策略提高免疫层析试纸条检测性能

以酰肼功能团修饰的胶体金作为试纸条的标记材料,利用酰肼基团可特异性地与抗体Fc片段醛基发生亲核加成反应的特性,实现抗体在胶体金纳米粒子（gold nanoparticles,AuNPs）表面的定向偶联。对比于碳二亚胺介导的共价偶联法,酰肼功能团介导的定向偶联需要更少的抗体标记量,更短的偶联时间,酰肼化胶体金免疫层析试纸条（hydrazided gold nanoparticles-based immunochromatographic assay,hAuNPs-ICA）检测玉米赤霉烯酮（zearalenone,ZEN）展示出更好的检测灵敏度;将hAuNPs-ICA检测ZEN加标的玉米样品,结果显示加标回收率介于83.1%～118.0%,批内、批间变异系数为3.9%～13.1%,表明hAuNPs-ICA具有较好的精密度和准确性。     

青钱柳提取物体外抗氧化活性研究

研究青钱柳不同溶剂提取物的体外抗氧化活性。测定了青钱柳不同溶剂提取物对DPPH自由基的清除作用,用化学发光法测定对超氧阴离子自由基(O·2)和羟自由基(·OH)的清除能力,并用烘箱储藏法测定对油脂的抗氧化活性。实验结果表明,醇提物具有较强的清除自由基能力和抗油脂氧化活性。     

Dietary fibre fractions from fruit and vegetable processing waste

Until recently, dietary fibre and its components were regarded as balast substances from vegetal food. These days, they are given increasing attention because of the beneficial physiological effects they may exert on human and animal organisms. Dietary fibre includes a number of components, and each of them displays specific properties. The components of major importance are cellulose, hemicellulose, lignin and pectins. The objective of this study was to determine the amounts of particular dietary fibre fractions in samples containing apple, black currant, chokeberry, pear, cherry and carrot pomace. The results revealed the following pattern: in each pomace sample, pectins occurred in the smallest amounts, and the content of lignin was very high (black currant and cherry pomace) or comparatively high (pear, chokeberry, apple and carrot pomace). The other dietary fibre components were difficult to form into clearly defined groups. Their proportions varied from one pomace type to another.     

Structure and rheological properties of acid-induced egg white protein gels

This study compares the rheological properties of acid-induced gels prepared of industrial spray-dried egg white proteins (EWP) with the acid-induced gels prepared of ovalbumin (OA) and whey protein isolate (WPI). Also we aimed to form transparent gels of EWP by means of the cold-gelation process. We showed that it was not possible to prepare cold-set gels because ovotransferrin (OT), present in EWP, was found to interfere with fibril formation. Therefore, we developed a new purification method in which first OT was selectively denatured by a heating step, subsequently precipitated by acidification and removed by centrifugation. Finally, the supernatant was desalted by ultra filtration. This resulted in a preheated EWP preparation, which mainly contains OA (>80%). By removing OT using this new preheat procedure transparent gels were obtained after acid-induced gelation. Fracture properties of various EWP preparations were determined and compared with those of acid-induced gels of OA and WPI. Gels formed from different EWP preparations were weak (fracture stress 1–15 kPa, fracture strain 0.3–0.7), and the networks consisted of thin strands with hardly any additional disulphide bonds formed during the gelation step. In conclusion, the microstructure of the aggregates formed in the first step of the cold-gelation process and the amount of additional disulphide bonds formed during the second step appeared to be the determining factors contributing to the hardness and deformability of acid-induced gels of egg white proteins.     

红薯直链淀粉的分离纯化和检测

以红薯淀粉为原料，在糊化和未糊化条件下采用碱液分散法对原淀粉进行分级，对提纯后的直链淀粉样品进行了分析；采用除去蛋白质和脂类的原淀粉进行浸提，可以大大提高产物的纯度，产品的纯度用其碘络合物的紫外可见光扫描图谱进行了证实。同时测得红薯直链淀粉含量16．12％。     

A fluorescent biosensor based on quantum dot–labeled streptavidin and poly-l-lysine for the rapid detection of Salmonella in milk

Salmonella, as a common foodborne pathogen in dairy products, poses a great threat to human health. We studied a new detection method based on quantum dots (QD). A fluorescent biosensor with multiple fluorescent signal amplification based on a streptavidin (SA) biotin system and the polyamino linear polymer poly-l-lysine (PLL) were established to detect Salmonella in milk. First, Salmonella was captured on a black 96-well plate with paired Salmonella mAb to form a double-antibody sandwich. Second, SA was immobilized on biotin-modified mAb by SA-biotin specific bond. Then, the biotin-modified polylysine (BT-PLL) was bound on SA and specifically bonded again through the SA-biotin system. Finally, water-soluble CdSe/ZnS QD-labeled SA was added to a black 96-well plate for covalent coupling with BT-PLL. The fluorescent signal was amplified in a dendritic manner by the layer-by-layer overlap of SA and biotin and the covalent coupling of biotinylated PLL. Under optimal conditions, the detection limit was 4.9 × 10³ cfu/mL in PBS. The detection limit was 10 times better than that of the conventional sandwich ELISA. In addition, the proposed biosensor was well specific and could be used for detecting Salmonella in milk samples.     

化学计量学在食品工业中的应用

本文从基于因子分析的多元校正方法、多元线性回归、分析信号处理、化学模式识别、人工神经网络等方面对化学计量学在食品工业中的应用作一阐述。     

Determination of carnosine in Black-Bone Silky Fowl (Gallus gallus domesticus Brisson) and common chicken by HPLC

Black-Bone Silky Fowl (Gallus gallus domesticus Brisson) is both consumed as a healthy food and used particularly as a kind of traditional Chinese medicine. Carnosine in the muscles of Black-Bone Silky Fowl was identified by HPLC–MS/PAD. The carnosine content in the meat of Black-Bone Silky Fowl was determined by HPLC and compared with that contained in the meat of White Plymouth Rock, which were bred under the same condition. The results showed that the contents of carnosine in the mixed meat, breast meat and thigh meat of Black-Bone Silky Fowl were all remarkably higher than that in the White Plymouth Rock. These findings indicate that Black-Bone Silky Fowl would be a better chicken breed for carnosine supplement.