《食品质地仪器测定》PPT课件.ppt

,第三节 食品质地的仪器测定,第三节 食品质地的仪器测定,1. 质构仪,第三节 食品质地的仪器测定,1. 质构仪,第三节 食品质地的仪器测定,1. 质构仪 应用：面粉/面团、烘焙食品、面条、米饭、乳制品、休闲食品、水产畜牧及其加工制品、蔬菜、包装材料、凝胶测试等。 数据：硬度、酥脆性、胶着性、黏聚性、韧性、屈服点、纤维强度、弹性、延展性、回复性、弹性、黏着性、咀嚼度、凝胶强度等。 测试标准：AACC（美国谷物化学协会）、AOAC（美国与欧洲凝胶协会）、BS（英国国家标准）、ASTM（美国材料试验协会）等。,质构仪,Back Extrusion反向挤出 Forward Extrusion 正向挤出 Bend 弯曲（折断） Compression压缩 Stress relaxation应力松弛 Creep A B蠕变 Penetration穿透（插入） Shear剪切 Stickiness test A B黏性 Tension拉伸,质构仪-TPA test,Texture profile analysis (TPA，质地剖面分析) is an objective method of sensory analysis pioneered in 1963 by Szczesniak , who defined the textural parameters first used in this method of analysis. Later in 1978 Bourne adapted the Instron to perform TPA by compressing standard-sized samples of food twice-二次压缩试验. SZCZESNIAK, A. S. (1963). Classification of textural characteristics. J. Food Sci, 28, 385-389. BOURNE, M. C. (1978). Texture Profile Analysis. Food Technol., 32 (7), 62-66, 72.,TPA is based on the recognition of texture as a multi-parameter attribute. For research purposes, a texture profile in terms of several parameters determined on a small homogeneous sample may be desirable. The test consists of compressing a bite-size piece of food two times in a reciprocating motion that imitates the action of the jaw and extracting from the resulting force-time curve a number of textural parameters that correlate well with sensory evaluation of those parameters,The mechanical textural characteristics of foods that govern, to a large extent, the selection of a rheological procedure, and instrument can be divided into the primary parameters of hardness, cohesiveness, springiness (elasticity), and adhesiveness, and into the secondary (or derived) parameters of fracturability (brittleness), chewiness and gumminess SZCZESNIAK, A. S. (1966). Texture Measurements. Food Technol., 20, 50, 55-58.,质构仪-TPA test,TPA test,第三节 食品质地的仪器测定,1. 质构仪-参数,Hardness(硬度),Hardness is defined as the maximum peak force during the first compression cycle (first bite) and has often been substituted by the term firmness.,Brittleness, crunchiness, and crumbliness, which are a similar concept, can be measured as the ease with which the material fractures under an increasing compression load In general, the smaller the deformation under a given load, the lower the cohesiveness and the greater the ability to fracture of the product.,Fracturability 酥脆性，易碎性、脆性、脆度 (originally called brittleness) is defined as the force at the first significant break in the TPA curve.,Adhesiveness黏着性，黏附性,Adhesiveness is defined as the negative force area for the first bite and represents the work required to overcome the attractive forces between the surface of a food and the surface of other materials with which the food comes into contact i.e. the total force necessary to pull the compression plunger away from the sample. For materials with a high adhesiveness and low cohesiveness, when tested, part of the sample is likely to adhere to the probe on the upward stroke.,Springiness（恢复性，弹性，回弹）,Springiness (originally called elasticity) is related to the height that the food recovers during the time that elapses between the end of the first bite and the start of the second bite.,Cohesiveness凝聚性，黏聚性,Cohesiveness is defined as the ratio of the positive force area during the second compression to that during the first compression.,Cohesiveness may be measured as the rate at which the material disintegrates under mechanical action. Tensile strength is a manifestation of cohesiveness. If adhesiveness is low compared with cohesiveness then the probe is likely to remain clean as the product has the ability to hold together. Cohesiveness is usually tested in terms of the secondary parameters chewiness and gumminess.,Gumminess胶黏性、胶着性,Gumminess is defined as the product of hardness cohesiveness. Gumminess is a characteristic of semisolid foods with a low degree of hardness and a high degree of cohesiveness.,Chewiness（咀嚼性）,Chewiness is defined as the product of gumminess springiness (which equals hardness cohesiveness springiness) and is therefore influenced by the change of any one of these parameters. Chewiness, tenderness and toughness are measured in terms of the energy required to masticate a solid food. They are the chracteristics most difficult to measure precisely, because mastication involves compressing, shearing, piercing, grinding, tearing and cutting, along with adequate lubrication by saliva at body temperatures.,It should be understood that the same product cannot exhibit both chewiness and gumminess, unless as a solid it becomes a semisolid during sensory mastication. Such a transition is practically never accomplished during instrumental TPA evaluation. Thus, it is incorrect to quantify and report chewiness and gumminess in TPA of solid or semisolid products. Chewiness should be reported for solids and gumminess for semisolids.,Stringiness 筋性,Stringiness is the distance the product is extended during decompression before separating from the compression probe.,It is not a parameter from the original Texture Profile Analysis work but instead has developed from looking more closely at the adhesiveness portion of the curve. Although this parameter is not built into the TPA macro and results files，the flexibility is available to include this parameter if you so desire. The units of this parameter would be in distance e.g. mm.,Initial Modulus,Initial Modulus is derived as Initial Stress / Initial Strain. Units are in e.g. N/mm. The Initial Stress is calculated as the average force of the points in the range 0.5 seconds to 1.5 seconds divided by the Contact Area . Initial Strain is the strain calculated at the 1.5 second point of the curve. The Initial Strain can only be calculated if STRAIN is available and hence PRODUCT HEIGHT can be derived. Initial Modulus is not a parameter from the original Texture Profile Analysis work but instead has developed from looking more closely at the portion of the curve before fracture.,第三节 食品质地的仪器测定,2. 流变仪 ?,流变仪可以进行各种压缩、拉伸、插入、剪断等测定，还可以完成几乎所有流变性质的力学测定。,第三节 食品质地的仪器测定,3. 布拉班德粉质仪,主要用于各种粉质的品质鉴定，如面粉、玉米粉、绿豆粉等。,第三节 食品质地的仪器测定,3. 布拉班德粉质仪,由调粉器和动力测定计组成。测定原理是把小麦粉和水用调粉器的搅拌臂揉成一定硬度的面团，并持续搅拌一段时间，并自动记录在揉面搅动过程中面团阻力的变化。,1搅拌槽 2测力计 3轴承 4连杆 5缓冲器 6指示盘 7记录仪 8恒温水槽 9循环管 10循环电机 11滴管,第三节 食品质地的仪器测定,3. 布拉班德粉质仪 数据分析,粉质仪得出的面团阻力曲线叫粉质曲线。,第三节 食品质地的仪器测定,3. 布拉班德粉质仪 数据分析,第三节 食品质地的仪器测定,3. 布拉班德粉质仪 数据分析 吸水率(water absorption)：小麦粉形成硬度为500B.U.的面团所需要的加水量。强筋粉吸水率大，弱筋粉吸水率小。 面团形成时间(dough development time)：从揉面开始达到最高黏度的时间。 面团稳定度Stab(stability)：阻力曲线中心线最初开始上升到50020B.U.到下降到50020B.U.所需要的时间，越长说明面团加工稳定性越好。,第三节 食品质地的仪器测定,3. 布拉班德粉质仪 数据分析 面团衰落度(weakness)：曲线从开始下降开始12 min后的下降值，衰落度值越小，说明面团筋力越强。 综合评价值VV(valorimeter value)：用面团形成时间和衰落度综合评价的指标。,第三节 食品质地的仪器测定,standard determination method 1,AACC 76-21.01 和 ICC 国际标准 No.162方法推荐标准方法1（STD1）进行测定,4. 淀粉粉力测定仪（RVA，rapid viscosity analyser）,第三节 食品质地的仪器测定,4. 淀粉粉力测定仪（RVA，rapid viscosity analyser）,测试结果： 峰值黏度 谷值黏度 衰减值 最终黏度 回生值 峰值时间 糊化温度,糊化特征曲线,第四节 食品质地评价仪器的选择,1. 仪器测定和感官评价的特点,食品物性仪器测定的开展,目的性要强 感官评价 科学分析 方法要科学 首先要明确要评价的感官性质及其内涵-进行分析型评价-确定重要的感官性质 然后用仪器进行各种可能的评价 建立感官与仪器评价之间的相关关系 确定仪器评价方法和指标,替代感官评价时仪器测定的分析与选择,以牛肉饼(hamburger)为例说明 （1）感宫评价前首先使评审员理解和明确各项感官评价用语