缅甸翡翠中"Cr的淡化"及意义

认为缅甸翡翠在形成的过程中存在"Cr的淡化"现象,探讨了该现象在翡翠绿色形成和演化过程中的表现形式及意义.缅甸翡翠中"Cr的淡化"可划分为4个阶段:(1)铬铁矿→钠铬辉石,该阶段是交代反应,形成冠状和柱粒状结构;(2)钠铬辉石→铬硬玉,该阶段是交代-置换反应;(3)铬硬玉→含Cr低的硬玉[ w(Cr2O3)约为0.3%],该阶段是重结晶置换反应;(4)含Cr硬玉进一步淡化,本质上该阶段是第三阶段的延续.缅甸翡翠中"Cr的淡化"受相邻矿物种类、剪切应力所致的后期变质变形机制和强度以及p/t条件和流体等因素的影响.在缅甸翡翠中,"Cr的淡化"贯穿翡翠形成过程的始终.用"Cr的淡化"能很好地解释缅甸翡翠绿色具独特色形、颜色浓淡变化大等特征,对于认识翡翠绿色及其变化、解析以及评价翡翠原石等具有重要意义.     

缅甸食品安全监管体系

缅甸积极参与"一带一路",并与我国签署了"一带一路"合作谅解备忘录, 2019年前4个月中缅贸易额已达37亿美元。中缅食品贸易互补性强,中缅边境食品贸易关系密切,贸易合作尚存巨大潜力。缅甸重视并建立了适合缅甸国情的食品安全监管体系。本研究分析了缅甸食品安全监管机构和职责、法律法规、标准体系、食品监管、贸易信息等,介绍缅甸食品安全监管的经验和做法,为政府部门和社会各界了解缅甸食品安全监管体系提供参考。     

Effect of Food Matrix on Saltiness Perception—Implications for Sodium Reduction

Enhancing sodium release from the food matrix, thus increasing saltiness perception, is a promising strategy to reduce the amount of salt needed in foods. However, the complex nature of the effect of the food matrix on saltiness perception makes it difficult to control saltiness perception when designing food products. The aim of this review is to provide an overview of the food matrix effects on saltiness perception of sodium chloride. The effects are discussed in the order of 3 stages in saltiness perception: release of sodium from food matrix into oral cavity (1st stage), delivery of sodium within oral cavity (2nd stage), and detection of sodium by the taste receptor cells (TRCs) (3rd stage). In the 1st stage, the food matrix affects the initial availability of sodium to be released, and also affects the spontaneous and facilitated migration of sodium from the matrix into the oral cavity. In the 2nd stage, the food matrix affects the availability of sodium and the mixing efficiency of sodium with saliva. The relationship between food matrix and oral processing of food that may affect the sodium release (1st stage) and the delivery (2nd stage) is also discussed. In the 3rd stage, the food matrix affects the physical availability of sodium for the TRCs, the physiological activity of TRCs, and the central activities involved in the perception process. Based on the understanding of complex nature of the matrix effects on saltiness perception discussed in this review, the properties of food matrix may be controlled effectively to enhance saltiness perception and achieve sodium reduction.     

不同产地蓝珀的荧光光谱特征

采用荧光光谱仪对多米尼加、墨西哥、缅甸三个产地蓝珀进行荧光光谱分析,旨在对比不同产地蓝珀的荧光光谱和发光特征.通过实验测试得到了蓝珀样品的光谱曲线及最佳激发光源、测试范围,分析了不同产地蓝珀的峰形、峰位及荧光强度与光谱平滑程度的关系.结果表明:不同产地蓝珀强荧光发射主要发生在可见光的蓝色区域.(1)多米尼加蓝珀的峰形为两个主峰及一个肩峰,分别位于450、474和507 nm附近,其中荧光为蓝色系列的多米尼加蓝珀两个主峰等高,荧光为蓝绿色系列的多米尼加蓝珀样品位于474 nm处主峰强度高于450 nm处;(2)墨西哥蓝珀的最佳激发光源不定,为一个多峰叠加的宽峰,主峰位于439 nm附近.但当样品荧光很强时出现两个分离峰,分别位于415、435 nm;(3)缅甸蓝珀的峰形和峰位与多米尼加蓝珀相似,主峰及肩峰分别位于450、475和508 nm附近,且450 nm主峰强度高于475 nm处,但荧光变弱时,最佳激发光源为399 nm,主峰位于433、451 nm;(4)不同产地蓝珀在相同光源照射条件下所呈现的荧光颜色及强度不同,所表现出的荧光光谱亦有差异.因此,蓝珀的荧光光谱可作为分析其荧光特征的研究手段之一.产生蓝色、蓝绿色荧光的原因,依据前人研究成果及本文的测试数据验证,发现主要是由芳香族化合物产生,初步推测为蒽、二萘嵌苯或其衍生物,不同产地蓝珀的荧光光谱存在差异,可能与引起荧光物质的相对含量及品种不同有关.     

缅甸食用农产品安全法规与进口准入解读

摘 要：（目的）自从缅甸和我国签署《区域全面经济伙伴关系协定》（RCEP , Regional Comprehensive Economic Partnership）以来,区域内的进出口贸易活动渐趋活跃。为促进中缅两国食用农产品从业者的信息交流和贸易发展,给相关出口企业提供政策参考从而避免遭遇不必要的贸易措施。（方法）通过获取国内外官方发布资料,翻译和解读缅甸相关规定。（结果）梳理出了缅甸进口食用农产品的安全法规、政府监管机构和准入要求。(结论) 解读得知缅甸食品、肉制品、水产品、植物产品的进口许可申办要素宗旨是安全无风险,我国的优质农产品和温带水果具备一定出口优势。     

ADSA Foundation Scholar Award: Possibilities and challenges of exopolysaccharide-producing lactic cultures in dairy foods

Exopolysaccharides (EPS) from lactic acid bacteria are a diverse group of polysaccharides exhibiting various functional properties. Two forms of EPS are produced by lactic acid bacteria: capsular and unattached. Capsular EPS does not cause ropiness nor does production of unattached EPS ensure ropiness. The functions of EPS in dairy products are not completely understood. This is for 2 main reasons: the major variations among exopolysaccharides even from the same group of micro-organisms, which makes it difficult to apply information from one EPS to others, and the lack of availability of techniques with the ability to observe the microstructure and distribution of the highly hydrated EPS in fermented dairy products. The introduction of relatively new microscopic techniques such as confocal scanning laser microscopy and cryo-scanning electron microscopy made it possible to directly observe the distribution of fully hydrated EPS in dairy products. Recently, EPS produced by nonropy strains have drawn the attention of the dairy industry. This is because of the ability of some nonropy strains to produce large capsular and unattached EPS that would improve the texture of dairy products without causing the undesirable slippery mouthfeel produced by the ropy strains. Factors affecting functions of EPS are their molecular characteristics and ability to interact with milk proteins. Studying the interaction between EPS and milk proteins is complex because EPS are gradually produced during fermentation, unlike polysaccharides added directly to milk to stabilize the fermented product. The concentration and possibly molecular characteristics of EPS and protein characteristics such as charge and hydrophobicity change during fermentation. Consequently, the interaction of EPS with proteins might also change during fermentation. Exopolysaccharides provide functions that benefit reduced-fat cheeses. They bind water and increase the moisture in the nonfat portion, interfere with protein-protein interactions and reduce the rigidity of the protein network, and increase viscosity of the serum phase. This review discusses the production of capsular EPS and their role in structure formation in fermented milk, the mechanism of ropiness formation, and applications of EPS-producing cultures in reduced-fat cheeses.     

The relative effect of milk base, starter, and process on yogurt texture: a review

Yogurt is a milk curd produced all over the world, obtained by a lactic fermentation of a milk base enriched with milk proteins, and sometimes sugars and thickeners. One of the most important sensorial attributes for yogurt is texture, which could be assessed by sensory or instrumental analysis. A lot of work has been published in studying the contribution of milk base, starter, and process on yogurt texture in order to develop new textures, or simply to reduce fat content, or the level of addition of protein and thickener in milk. However, these studies are limited to only a few factors. The topic of this review was to synthesize the data of literature, with the aim of extracting and classifying factors on the basis of their influence on yogurt texture. Three factors, milk base heating, starter, and yogurt shearing after fermentation, respectively, play a key role in the elaboration of texture. The control of these three parameters allows the improvement of the textural attributes of yogurts by 2 to 15 times.     

The effect of substituting NaCl with KCl on Nabulsi cheese: chemical composition, total viable count, and texture profile

The effect of substituting NaCl with KCl on Nabulsi cheese characteristics was investigated. Nabulsi cheese was made and stored in 4 different brine solutions at 18%, including NaCl only (A; control); 3NaCl:1KCl (wt/wt; B); 1NaCl:1KCl (wt/wt; C); and 1NaCl:3KCl (wt/wt; D). Chemical composition, proteolysis, total viable count, and texture profile analysis were assessed at monthly intervals for 5 mo. No significant effect was found among experimental cheeses in terms of chemical composition or texture profile. Proteolytic activities were higher in cheeses kept in brine solutions that contained higher KCl (B, C, and D) compared with the control. At the end of the storage period, water-soluble nitrogen in Nabulsi cheeses stored in B, C, and D was higher than that in the control cheese (A). In addition, total viable count increased significantly after 1 mo of storage for all salt treatments. Hardness and gumminess generally decreased significantly during storage within the same salt treatment.     

毛霉发酵对豆制品的质构和微观结构的影响

利用质构仪和扫描电子显微镜研究毛霉发酵豆腐的质构和微观结构,通过电泳分析豆腐的蛋白质水解情况,并与未发酵豆腐进行对比。结果表明,与未发酵豆腐相比,发酵豆腐的硬度和黏性增大,内聚性和弹性减小。其微观结构较均匀致密。电泳分析和微结构分析均显示出大分子量的蛋白质在豆腐发酵过程中的降解。