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1、第三节第三节 食质量地的仪器测定食质量地的仪器测定 第三节 食质量地的仪器测定1. 质构仪质构仪第三节 食质量地的仪器测定1. 质构仪质构仪第三节 食质量地的仪器测定1. 质质构构仪仪 运运用用：面面粉粉/面面团团、烘烘焙焙食食品品、面面条条、米米饭饭、乳乳制制品品、休休闲闲食食品品、水水产产畜畜牧牧及及其其加加工工制制品品、蔬蔬菜菜、包包装装资资料、凝胶料、凝胶测试测试等。等。 数数据据：硬硬度度、酥酥脆脆性性、胶胶着着性性、黏黏聚聚性性、韧韧性性、屈屈服服点点、纤纤维维强强度度、弹弹性性、延延展展性性、回回复复性性、弹弹性性、黏着性、咀嚼度、凝胶黏着性、咀嚼度、凝胶强强度等。度等。 测测试
2、试规规范范：AACC 美美国国谷谷物物化化学学协协会会 、AOAC 美美国国与与欧欧洲洲凝凝胶胶协协会会 、BS 英英国国国国家家规规范范 、ASTM 美国美国资资料料实验协实验协会会 等。等。质构仪lBack Extrusion反向挤出lForward Extrusion 正向挤出lBend 弯曲折断lCompression紧缩lStress relaxation应力松弛lCreep A B蠕变lPenetration穿透插入lShear剪切lStickiness test A B黏性lTension拉伸质构仪-TPA testTexture profile analysis (TPA，质地
3、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-二次紧缩实验.SZCZESNIAK, A. S. (1963). C
4、lassification of textural characteristics. J. Food Sci, 28, 385-389.BOURNE, M. C. (1978). Texture Profile Analysis. Food Technol., 32 (7), 62-66, 72.lTPA is based on the recognition of texture as a multi-parameter attribute. For research purposes, a texture profile in terms of several parameters det
5、ermined on a small homogeneous sample may be desirable. lThe 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 sens
6、ory evaluation of those parameterslThe 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
7、secondary (or derived) parameters of fracturability (brittleness), chewiness and gumminess lSZCZESNIAK, A. S. (1966). Texture Measurements. Food Technol., 20, 50, 55-58.质构仪-TPA testlTPA test第三节 食质量地的仪器测定1. 质构仪质构仪-参数参数Hardness(硬度)lHardness is defined as the maximum peak force during the first compres
8、sion cycle (first bite) and has often been substituted by the term firmness.lBrittleness, crunchiness, and crumbliness, which are a similar concept, can be measured as the ease with which the material fractures under an increasing compression loadlIn general, the smaller the deformation under a give
9、n 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lAdhesiveness is defined as the negative force area for th
10、e 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 contactl i.e. the total force necessary to pull the compression plunger away from the sample. For materials with a high adhe
11、siveness 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lSpringiness (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
12、start of the second bite.Cohesiveness凝聚性，黏聚性lCohesiveness is defined as the ratio of the positive force area during the second compression to that during the first compression.lCohesiveness may be measured as the rate at which the material disintegrates under mechanical action. Tensile strength is a
13、 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.lCohesiveness is usually tested in terms of the secondary parameters chewiness and gumminess.Gumminess胶黏性、胶着性lGumminess is define
14、d as the product of hardness cohesiveness.lGumminess is a characteristic of semisolid foods with a low degree of hardness and a high degree of cohesiveness.Chewiness咀嚼性lChewiness is defined as the product of gumminess springiness (which equals hardness cohesiveness springiness) and is therefore infl
15、uenced by the change of any one of these parameters.lChewiness, 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, te
16、aring and cutting, along with adequate lubrication by saliva at body temperatures.lIt 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 durin
17、g instrumental TPA evaluation. lThus, it is incorrect to quantify and report chewiness and gumminess in TPA of solid or semisolid products. lChewiness should be reported for solids and gumminess for semisolids.Stringiness 筋性筋性Stringiness is the distance the product is extended during decompression b
18、efore separating from the compression probe. lIt 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.lAlthough this parameter is not built into the TPA macro and results files，the flexibility
19、is available to include this parameter if you so desire. lThe units of this parameter would be in distance e.g. mm.Initial ModuluslInitial 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
20、.5 seconds to 1.5 seconds divided by the Contact Area .l Initial Strain is the strain calculated at the 1.5 second point of the curve. lThe Initial Strain can only be calculated if STRAIN is available and hence PRODUCT HEIGHT can be derived.lInitial Modulus is not a parameter from the original Textu
21、re Profile Analysis work but instead has developed from looking more closely at the portion of the curve before fracture.第三节 食质量地的仪器测定2. 流变仪流变仪 ?流流变变仪仪可可以以进进展展各各种种紧紧缩缩、拉拉伸伸、插插入入、剪剪断断等等测测定定，还还可可以以完完成成几几乎乎一一切切流流变变性性质的力学测定。质的力学测定。第三节 食质量地的仪器测定3. 布拉班德粉质仪布拉班德粉质仪主主要要用用于于各各种种粉粉质的的质量量鉴定定，如如面面粉粉、玉玉米米粉粉、绿豆豆粉等
22、。粉等。第三节 食质量地的仪器测定3. 布拉班德粉质仪布拉班德粉质仪由由调粉粉器器和和动力力测定定计组成成。测定定原原理理是是把把小小麦麦粉粉和和水水用用调粉粉器器的的搅拌拌臂臂揉揉成成一一定定硬硬度度的的面面团，并并继续搅拌拌一一段段时间，并自并自动记录在揉面在揉面搅动过程中面程中面团阻力的阻力的变化。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 食质量地的仪器测定3. 布拉班德粉质仪布拉班德粉质仪 数据分析数据分析粉质仪得出的面团阻力曲线叫粉质曲线。粉质仪得出的面团阻力曲线叫粉质曲线。 第三节 食质量地的仪器测定3.
23、布拉班德粉质仪布拉班德粉质仪 数据分析数据分析第三节 食质量地的仪器测定3. 布拉班德粉布拉班德粉质仪质仪 数据分析数据分析吸吸 水水 率率 (water absorption)： 小小 麦麦 粉粉 构构 成成 硬硬 度度 为为500B.U.的的面面团团所所需需求求的的加加水水量量。强强筋筋粉粉吸吸水水率率大大，弱筋粉吸水率小。弱筋粉吸水率小。面面团团构构成成时时间间(dough development time)：从从揉揉面面开开场场到达最高黏度的到达最高黏度的时间时间。面面团团稳稳定定度度Stab(stability)：阻阻力力曲曲线线中中心心线线最最初初开开场场上上升升到到50020B.
24、U.到到下下降降到到50020B.U.所所需需求求的的时间时间，越，越长阐长阐明面明面团团加工加工稳稳定性越好。定性越好。第三节 食质量地的仪器测定3. 布拉班德粉布拉班德粉质仪质仪 数据分析数据分析面面团团衰衰落落度度(weakness)：曲曲线线从从开开场场下下降降开开场场12 min后后的的下下降降值值，衰衰落落度度值值越越小小，阐阐明明面面团团筋筋力力越越强强。综综合合评评价价值值VV(valorimeter value)：用用面面团团构构成成时时间间和衰落度和衰落度综综合合评评价的目的。价的目的。第三节 食质量地的仪器测定TimeTime（时间时间）TypeType（类类型）型）Va
25、lueValue（值值）00:00:0000:00:00TempTemp（温度）（温度）505000:00:0000:00:00SpeedSpeed（转转速）速）960rpm960rpm00:00:1000:00:10SpeedSpeed（转转速）速）160rpm160rpm00:01:00TempTemp（温度）（温度）505000:04:4200:04:42TempTemp（温度）（温度）959500:07:1200:07:12TempTemp（温度）（温度）959500:11:0000:11:00TempTemp（温度）（温度）505000:13:0000:13:00EndEnd（结结束
26、）束）standard determination method 1 uAACC 76-21.01 和 ICC 国际规范 No.162方法引荐规范方法1STD1进展测定4. 淀淀粉粉粉粉力力测测定定仪仪RVA，rapid viscosity analyser第三节 食质量地的仪器测定4. 淀淀粉粉粉粉力力测测定定仪仪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糊化特征曲线第四节 食质量地评价仪器的选择1. 仪器测定和感官评价的特点仪器测定和感官评价的特点食品物性仪器测定的开展l目的性要强l感官评价l科学分析l
27、方法要科学l首先要明确要评价的感官性质及其内涵-进展分析型评价-确定重要的感官性质l然后用仪器进展各种能够的评价l建立感官与仪器评价之间的相关关系l确定仪器评价方法和目的替代感官评价时仪器测定的分析与选择l以牛肉饼(hamburger)为例阐明l1感宫评价前首先使评审员了解和明确各项感官评价用语的定义(如表3-11所示)。l往往一些评审员在许多情况下，搞不清“硬和“弹性的定义，或将这两者混同。因此，在感官评审前要仔细进展必要的阐明和示范。(2)制定规范实施评价。l感官评价的得分规范如图3-12所示。该方法称为对比得分法。即将2种以上的试样与对照食品(规范食品)相比较，把比较后感到的差别程度，以
28、数值的方式打分评价。在选择规范食品时，留意要预先进展感官检查。其质地的各性质要求比较适中。每次品味实验时，同时摆出一个规范食品和一个试样食品，由5名评审员按图3-12的各工程品评打分，本例对48种试样进展了实验。(3)仪器测定l对以下8个工程进展测定：l水分，肉粒平均直径，离液量(挤压流汤量)，应力松弛，切断实验，咬断剪压)实验(用U形或V形模头剪压试样)，咀嚼实验(即紧缩破坏实验,测硬度、疏松度)，穿孔实验(测最大破坏应力)。(4)相关性分析。l将以上仪器测定值与感官侧定值进展相关性分析(如表3-12所示)，可得到，与各工程感官评价相关性最大的仪器测定工程(按最大相关性顺序取前3位)。l可以
29、看出，与感官工程肉粒感、多筋性相关最大的仪器侧定方法为:刃状压头剪切时的切断功；硬度、固着性和咀嚼口感与穿孔实验的最大应力有很高的相关关系；而油腻感仅与离液量有一定相关，与其它测定工程结果无关。 (5)多元回归分析。l进展多元回归分析找出替代感官评价最适宜仪器测进展多元回归分析找出替代感官评价最适宜仪器测定值组合。定值组合。l肉饼的硬度感受可用咀嚼仪器侧定和水分测定的数肉饼的硬度感受可用咀嚼仪器侧定和水分测定的数值综合断定值综合断定;l而弹性感和固着性觉得只与穿孔实验的最大应力有而弹性感和固着性觉得只与穿孔实验的最大应力有很高相关；很高相关；l疏松感可用穿孔最大应力和切断强度值综合判别；疏松感可用穿孔最大应力和切断强度值综合判别；l咬断性可用硬度值和切断强度值综合判别；咬断性可用硬度值和切断强度值综合判别；l油腻感虽然与仪器测定值相关不太大，但也还可用油腻感虽然与仪器测定值相关不太大，但也还可用离液全量，离液中脂肪量和离液全量，离液中脂肪量和V形压头压切强度三者形压头压切强度三者综合判别。肉粒感用刃状压头切断功和平均肉粒直综合判别。肉粒感用刃状压头切断功和平均肉粒直径综合判别。径综合判别。l可见要替代感官评价，往往需求多种测定仪器综合可见要替代感官评价，往往需求多种测定仪器综合判别。判别。
