基于不同乳糖浓度的乳蛋白浓缩物发酵特性研究

利用保加利亚乳杆菌和嗜热链球菌复合发酵剂对乳蛋白浓缩物(milk protein concentrate,MPC)进行发酵,研究了不同乳糖浓度下MPC的发酵特性。结果表明,乳糖浓度影响MPC发酵进入稳定期的时间与pH值,随着乳糖浓度的升高,MPC发酵物的最终pH值下降(pH值范围4.14～4.59);微流变学研究表明,随乳糖浓度升高,MPC发酵物的宏观黏性因子减小,而固液平衡值和流动性指数增大;质构特性研究表明,MPC发酵物的持水力随乳糖浓度升高而逐渐升高,胶着性、弹性则呈现先增大后减小的趋势,而硬度、黏力不受影响;气相色谱-质谱联用分析结果显示,酸类化合物和酮类化合物是MPC发酵物中的主要挥发性物质,随乳糖浓度的增加,酸类化合物含量减少,而2,3-丁二酮、3-羟基-2-丁酮等乳糖代谢物的含量增加。本研究结果旨在为进一步了解MPC的发酵特性并拓宽MPC在不同发酵乳制品中的应用提供基础数据。     

耐高温阻燃布的研制

探讨了一种以聚丙烯腈预氧化纤维为原料的耐高温阻燃布的设计与生产方法。这是一种高密织物 ,是阻燃防护服的理想面料。     

湖南湘西百合营养及淀粉理化特性研究

为探讨湖南湘西食用百合(BJBH)的品质特性,本试验系统分析其主要营养成分,生、熟百合质构特性,全粉与精制淀粉的膨胀势和凝胶质构及淀粉理化特性。结果表明:在研究变幅内,BJBH的蛋白、淀粉及膳食纤维等主要成分含量表示出不同;煮熟后其质构特性变化主要是由大分子物质(淀粉、膳食纤维)吸水膨胀引起;全粉和淀粉膨胀势分别为6.2和14.5 g/g,纤维素等不溶性多糖是导致两者凝胶质构显著不同的主要因素;BJBH淀粉颗粒粒径集中分布在9.09~34.57μm,平均粒径19.28μm;衍射类型属B型,相对结晶度为54.4%;DSC曲线中TO、TP、TC和ΔHgel分别为54.0、63.2、75.0℃和13.3 J/g;淀粉颗粒酶解速率先快后慢,72 h后分解速率趋于稳定;淀粉颗粒的吸水速率先减慢后升快,在相对湿度为100%时吸水量约为215 mg/g。     

干酪质地及流变学特性的研究进展

介绍了有关干酪的成分及工艺过程对质地和流变学特性影响的研究。在干酪成分中，蛋白质是影响产品流变学特性的主要因素，酪蛋白空间形成的网状结构构成了干酪流变学的基础。在加工过程中，pH、温度、钙浓度、蛋白水解等所有对干酪成分分子产生变化的因素都可能使干酪的流变学特性和质地发生变化。因此，干酪流变学特性的研究对更好地控制质地，生产出质优价廉的干酪，具有重要的意义。最后，研究状况进行了展望。     

Surface texture of foods: perception and characterization

Surface texture is generally accepted as a key sensory factor of food materials and has great impact on consumers' perception and expectation of a food product. However, no authentic definition has been given in the literature for the term surface texture. Its real meaning is often rather confusing, varying from case to case and from person to person. A general consensus is that surface texture is a multi-parameter sensory factor composed of those surface-related features which can be perceived by visual, tactile handfeel, and tactile mouthfeel senses. A list of such surface-related features has been produced in this review, and of those, topographical properties are probably the most intensively investigated features in literature and are discussed in detail in this paper. The surface texture of a food can be characterized by either sensory panel tests or by physical instrument tests. The former uses panellists (trained or untrained) for sensory assessment, while the latter applies physical techniques to characterize the surface. While sensory tests are widely used for studies on consumers' perception and preference of foods, instrumental characterization uses one or few parameters to define a surface (either qualitatively or quantitatively). Physical techniques used for surface characterization are categorized into two groups: surface contacting and non-surface contacting. The former include tribometer, surface force apparatus, contact profilometry, atomic force microscopy, friction force microscopy, etc. Non-surface contacting techniques include gloss metre, fiber optic reflectometer, angle-resolved light scattering apparatus, surface glistening points method, electron microscopy, confocal laser scanning microscopy, etc. The principles and application examples of these techniques were discussed in this review.     

Effects of high pressure treatment on the quality and storage of kimchi

The effects of high pressure treatment on the microflora and storage of kimchi were investigated. In a bacterial suspension, numbers of Lactobacillus plantarum were reduced by 6 logs by 500 MPa, at 25 °C for 10 min. Kimchi juice did not alter the rate of inactivation of lactic acid bacteria by high pressure treatment. There was no change in the texture of kimchi subjected to a pressure of 400 MPa, but an increase in cutting force was observed at 600 MPa. When kimchi was pressurized at 400 MPa for 10 min at 25 °C and subsequently stored at 20 °C for 4 weeks, the total number of viable cells stayed at 10³ CFU mL⁻¹. High pressure treatment above 400 MPa prevented excessive acidification that typically occurs during the extended storage of kimchi. The inflation of pouches as a result of accumulated carbon dioxide was also prevented by high pressure treatment. Although colour changes were accelerated by high pressure treatment, this study demonstrates that high pressure treatment can be used to control overripening during the distribution and storage of kimchi products.     

Relationship between Sensory and Instrumental Hardness of Commercial Cheeses

ABSTRACT: The effect of deformation (10% to 90%) and deformation rate (0.2 to 10 mm/s) on both maximum compression force and correlation between sensory and instrumental measurements of hardness were investigated for 26 commercial cheeses. Log-linear regression models were used to model the relationship between deformation rate and maximum compression force and fitted well to the relationship, indicating that maximum compression force is a log linear function of deformation rate. Deformation had a large effect on the correlation between sensory and instrumental hardness, while deformation rate had a small effect. The optimal deformation and deformation rate for the maximum correlation were 70% to 90% and 1.0 mm/s, respectively. This implies that an optimal combination of deformation and deformation rate can be used for maximizing the correlation between sensory and instrumental hardness for cheese products.     

缅甸莫西西玉--一种特殊的动力变质与交代玉石

以缅甸莫西西玉为研究对象，采用镜下分析、X射线粉晶衍射、电子探针、拉曼光谱、红外吸收光谱等分析测试方法，重点对该玉石的成分、玉相和振动光谱特征进行了研究。研究表明，莫西西玉主要由一组分布不均的富铬矿物组成，即铬硬玉[x(Kch)为15％～18％]、富铬氟镁钠闪石[ω(Cr2O3)为4％左右]、钠长石、含铬钠长石[ω(Cr2O3)为1％左右]、钠铬辉石[x(Kch)为62％～65％]及铬铁矿。玉石具典型的糜棱、交代网脉状及交代假象结构。在300-580cm^-1拉曼位移范围内，钠铬辉石和铬硬玉中由Cr-O和Al—O弯曲振动致拉曼谱蜂，其蜂形、蜂位、半高宽及振动频率均存在较明显的差异。研究结果初步证实，莫西西玉属一种典型的由不同期次动力变质与低温热液交代作用形成的玉石。     

Recent Advances in Methods and Techniques for Freshness Quality Determination and Evaluation of Fish and Fish Fillets: A Review

The freshness quality of fish plays an important role in human health and the acceptance of consumers as well as in international fishery trade. Recently, with food safety becoming a critical issue of great concern in the world, determination and evaluation of fish freshness is much more significant in research and development. This review renovates and concentrates recent advances of evaluating methods for fish freshness as affected by preharvest and postharvest factors and highlights the determination methods for fish freshness including sensory evaluation, microbial inspection, chemical measurements of moisture content, volatile compounds, protein changes, lipid oxidation, and adenosine triphosphate (ATP) decomposition (K value), physical measurements, and foreign material contamination detection. Moreover, the advantages and disadvantages of these methods and techniques are compared and discussed and some viewpoints about the current work and future trends are also presented.     

Correlated changes in skeletal muscle connective tissue and flesh texture during starvation and re‐feeding in brown trout (Salmo trutta) reared in seawater

Quantitative and qualitative changes to muscle and collagen were analysed following starvation and re‐feeding of brown trout (Salmo trutta) reared in seawater. Fish were submitted to starvation for 2 months followed by re‐feeding for 1 month and compared with a control group continuously fed. Classical effects of starvation on growth and morphometrics traits were observed with only a partial recovery of these parameters after 1 month of re‐feeding. Muscle composition of starved fish was significantly affected (lower dry matter content and higher post‐mortem pH) compared with control fish and was partially recovered in re‐fed fish compared with continuously fed fish. Muscle structure and composition were affected with thinner muscle fibre and higher connective tissue content for the starved fish but similar thickness of myosepta compared with the control group. No difference was observed after 1 month of re‐feeding. Characteristics of the connective tissue were significantly affected by starvation (more high weight molecular collagen form, higher thermal stability of skin collagen). These differences remained significant after the re‐feeding period. Starved fish showed also higher mechanical resistance of the raw flesh compared with the control group, but no difference in rheological measurements was observed after 1 month of re‐feeding. The changes in texture and their relationships with muscle composition, muscle structure and collagen characteristics are discussed. Copyright © 2004 Society of Chemical Industry