食品質(zhì)地儀器測定

1、 第三節(jié) 食品質(zhì)地的儀器測定 1. 質(zhì)構(gòu)儀質(zhì)構(gòu)儀 第三節(jié) 食品質(zhì)地的儀器測定 1. 質(zhì)構(gòu)儀質(zhì)構(gòu)儀 第三節(jié) 食品質(zhì)地的儀器測定 1. 質(zhì)構(gòu)儀質(zhì)構(gòu)儀 n 應(yīng)用：面粉應(yīng)用：面粉/面團(tuán)、烘焙食品、面條、米飯、乳制品、休面團(tuán)、烘焙食品、面條、米飯、乳制品、休 閑食品、水產(chǎn)畜牧及其加工制品、蔬菜、包裝材料、凝膠閑食品、水產(chǎn)畜牧及其加工制品、蔬菜、包裝材料、凝膠 測試等。測試等。 n 數(shù)據(jù)：硬度、酥脆性、膠著性、黏聚性、韌性、屈服點、數(shù)據(jù)：硬度、酥脆性、膠著性、黏聚性、韌性、屈服點、 纖維強(qiáng)度、彈性、延展性、回復(fù)性、彈性、黏著性、咀嚼纖維強(qiáng)度、彈性、延展性、回復(fù)性、彈性、黏著性、咀嚼 度、凝膠強(qiáng)度等。度、凝

2、膠強(qiáng)度等。 n 測試標(biāo)準(zhǔn)：測試標(biāo)準(zhǔn)：AACC（美國谷物化學(xué)協(xié)會）、（美國谷物化學(xué)協(xié)會）、AOAC（美國（美國 與歐洲凝膠協(xié)會）、與歐洲凝膠協(xié)會）、BS（英國國家標(biāo)準(zhǔn)）、（英國國家標(biāo)準(zhǔn)）、ASTM（美國（美國 材料試驗協(xié)會）等。材料試驗協(xié)會）等。 質(zhì)構(gòu)儀 l Back Extrusion反向擠出 l Forward Extrusion 正向擠出 l Bend 彎曲（折斷） l Compression壓縮 l Stress relaxation應(yīng)力松弛 l Creep A B蠕變 l Penetration穿透（插入） l Shear剪切 l Stickiness test A B黏性 lTens

3、ion拉伸 質(zhì)構(gòu)儀-TPA test Texture profile analysis (TPA，質(zhì)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 sampl

4、es of food twice-二次壓縮試驗. 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. l TPA is based on the recognition of texture as a multi-parameter attribute. For research purpose

5、s, a texture profile in terms of several parameters determined on a small homogeneous sample may be desirable. l 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 num

6、ber of textural parameters that correlate well with sensory evaluation of those parameters l 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,

7、 springiness (elasticity), and adhesiveness, and into the secondary (or derived) parameters of fracturability (brittleness), chewiness and gumminess l SZCZESNIAK, A. S. (1966). Texture Measurements. Food Technol., 20, 50, 55-58. 質(zhì)構(gòu)儀-TPA test lTPA test 第三節(jié) 食品質(zhì)地的儀器測定 1. 質(zhì)構(gòu)儀質(zhì)構(gòu)儀-參數(shù)參數(shù) Hardness(硬度) lHardn

8、ess is defined as the maximum peak force during the first compression cycle (first bite) and has often been substituted by the term firmness. l Brittleness, crunchiness, and crumbliness, which are a similar concept, can be measured as the ease with which the material fractures under an increasing co

9、mpression load l 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 酥脆性酥脆性，易碎性、脆性、脆度，易碎性、脆性、脆度 (originally called brittleness) is defined as the force at the first significant break in the TPA

10、curve. Adhesiveness黏著性，黏附性 l 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 l i.e. the total force necessa

11、ry 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（恢復(fù)性，彈性，回彈） l Springiness (originally called elasticity) is related to the height th

12、at 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 lCohesiveness is defined as the ratio of the positive force area during the second compression to that during the first compression. l Cohesiveness may be measure

13、d 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. l Cohesiveness is usually tested

14、 in terms of the secondary parameters chewiness and gumminess. Gumminess膠黏性、 lGumminess is defined 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） l Chewiness is defined as the

15、product of gumminess springiness (which equals hardness cohesiveness springiness) and is therefore influenced by the change of any one of these parameters. l Chewiness, tenderness and toughness are measured in terms of the energy required to masticate a solid food. They are the chracteristics most d

16、ifficult to measure precisely, because mastication involves compressing, shearing, piercing, grinding, tearing and cutting, along with adequate lubrication by saliva at body temperatures. l It should be understood that the same product cannot exhibit both chewiness and gumminess, unless as a solid i

17、t becomes a semisolid during sensory mastication. Such a transition is practically never accomplished during instrumental TPA evaluation. l Thus, it is incorrect to quantify and report chewiness and gumminess in TPA of solid or semisolid products. l Chewiness should be reported for solids and gummin

18、ess for semisolids. Stringiness 筋性筋性 Stringiness is the distance the product is extended during decompression before 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 p

19、ortion of the curve. lAlthough this parameter is not built into the TPA macro and results files，the flexibility is available to include this parameter if you so desire. lThe units of this parameter would be in distance e.g. mm. Initial Modulus l Initial Modulus is derived as Initial Stress / Initial

20、 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 . l Initial Strain is the strain calculated at the 1.5 second point of the curve. l The Initial Strain can only be calculated if ST

21、RAIN is available and hence PRODUCT HEIGHT can be derived. l 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. 第三節(jié) 食品質(zhì)地的儀器測定 2. 流變儀流變儀 ? 流變儀可以進(jìn)行各種壓縮、流變儀可以進(jìn)行各種壓縮、 拉伸、插入、剪斷

22、等測定，拉伸、插入、剪斷等測定， 還可以完成幾乎所有流變性還可以完成幾乎所有流變性 質(zhì)的力學(xué)測定。質(zhì)的力學(xué)測定。 第三節(jié) 食品質(zhì)地的儀器測定 3. 布拉班德粉質(zhì)儀布拉班德粉質(zhì)儀 主要用于各種粉質(zhì)的品質(zhì)鑒主要用于各種粉質(zhì)的品質(zhì)鑒 定，如面粉、玉米粉、綠豆定，如面粉、玉米粉、綠豆 粉等。粉等。 第三節(jié) 食品質(zhì)地的儀器測定 3. 布拉班德粉質(zhì)儀布拉班德粉質(zhì)儀 由調(diào)粉器和動力測定計組成。測定原理是把小麥粉和水用調(diào)由調(diào)粉器和動力測定計組成。測定原理是把小麥粉和水用調(diào) 粉器的攪拌臂揉成一定硬度的面團(tuán)，并持續(xù)攪拌一段時間，粉器的攪拌臂揉成一定硬度的面團(tuán)，并持續(xù)攪拌一段時間， 并自動記錄在揉面攪動過程中面團(tuán)阻

23、力的變化。并自動記錄在揉面攪動過程中面團(tuán)阻力的變化。 1攪拌槽 2測力計 3軸承 4連桿 5緩沖器 6指示盤 7記錄儀 8恒溫水槽 9循環(huán)管 10循環(huán)電機(jī) 11滴管 第三節(jié) 食品質(zhì)地的儀器測定 3. 布拉班德粉質(zhì)儀布拉班德粉質(zhì)儀 n 數(shù)據(jù)分析數(shù)據(jù)分析 粉質(zhì)儀得出的面團(tuán)阻力曲線叫粉質(zhì)儀得出的面團(tuán)阻力曲線叫粉質(zhì)曲線粉質(zhì)曲線。 第三節(jié) 食品質(zhì)地的儀器測定 3. 布拉班德粉質(zhì)儀布拉班德粉質(zhì)儀 n 數(shù)據(jù)分析數(shù)據(jù)分析 第三節(jié) 食品質(zhì)地的儀器測定 3. 布拉班德粉質(zhì)儀布拉班德粉質(zhì)儀 n 數(shù)據(jù)分析數(shù)據(jù)分析 吸水率吸水率(water absorption)：小麥粉形成硬度為：小麥粉形成硬度為500B.U.的面的

24、面 團(tuán)所需要的加水量。強(qiáng)筋粉吸水率大，弱筋粉吸水率小。團(tuán)所需要的加水量。強(qiáng)筋粉吸水率大，弱筋粉吸水率小。 面團(tuán)形成時間面團(tuán)形成時間(dough development time)：從揉面開始達(dá)到：從揉面開始達(dá)到 最高黏度的時間。最高黏度的時間。 面團(tuán)穩(wěn)定度面團(tuán)穩(wěn)定度Stab(stability)：阻力曲線中心線最初開始上升：阻力曲線中心線最初開始上升 到到50020B.U.到下降到到下降到50020B.U.所需要的時間，越長說所需要的時間，越長說 明面團(tuán)加工穩(wěn)定性越好。明面團(tuán)加工穩(wěn)定性越好。 第三節(jié) 食品質(zhì)地的儀器測定 3. 布拉班德粉質(zhì)儀布拉班德粉質(zhì)儀 n 數(shù)據(jù)分析數(shù)據(jù)分析 面團(tuán)衰落度面團(tuán)衰

25、落度(weakness)：曲線從開始下降開始：曲線從開始下降開始12 min后的后的 下降值，衰落度值越小，說明面團(tuán)筋力越強(qiáng)。下降值，衰落度值越小，說明面團(tuán)筋力越強(qiáng)。 綜合評價值綜合評價值VV(valorimeter value)：用面團(tuán)形成時間和衰：用面團(tuán)形成時間和衰 落度綜合評價的指標(biāo)。落度綜合評價的指標(biāo)。 第三節(jié) 食品質(zhì)地的儀器測定 standard determination method 1 uAACC 76-21.01 和 ICC 國際標(biāo)準(zhǔn) No.162方法推薦標(biāo) 準(zhǔn)方法1（STD1）進(jìn)行測定 4. 淀粉粉力測定儀（淀粉粉力測定儀（RVA，rapid viscosity analy

26、ser） 第三節(jié) 食品質(zhì)地的儀器測定 4. 淀粉粉力測定儀（淀粉粉力測定儀（RVA，rapid viscosity analyser） 測試結(jié)果： 峰值黏度峰值黏度 谷值黏度谷值黏度 衰減值衰減值 最終黏度最終黏度 回生值回生值 峰值時間峰值時間 糊化溫度糊化溫度 糊化特征曲線糊化特征曲線 第四節(jié) 食品質(zhì)地評價儀器的選擇 1. 儀器測定和感官評價的特點儀器測定和感官評價的特點 食品物性儀器測定的開展 l目的性要強(qiáng) 感官評價 科學(xué)分析 l方法要科學(xué) 首先要明確要評價的感官性質(zhì)及其內(nèi)涵-進(jìn)行分 析型評價-確定重要的感官性質(zhì) 然后用儀器進(jìn)行各種可能的評價 建立感官與儀器評價之間的相關(guān)關(guān)系 確定儀器評

27、價方法和指標(biāo) 替代感官評價時儀器測定的分析與選擇 l以牛肉餅(hamburger)為例說明 l（1）感宮評價前首先使評審員理解和明 確各項感官評價用語的定義(如表3-11所 示)。 往往一些評審員在許多情況下，搞不清“硬” 和“彈性”的定義，或?qū)⑦@兩者混同。因此， 在感官評審前要認(rèn)真進(jìn)行必要的說明和示范。 (2)制定標(biāo)準(zhǔn)實施評價。 l 感官評價的得分標(biāo)準(zhǔn)如圖3-12所示。該方法稱為 對比得分法。即將2種以上的試樣與對照食品(標(biāo) 準(zhǔn)食品)相比較，把比較后感到的差異程度，以數(shù) 值的形式打分評價。在選擇標(biāo)準(zhǔn)食品時，注意要 預(yù)先進(jìn)行感官檢查。其質(zhì)地的各性質(zhì)要求比較適 中。每次品嘗試驗時，同時擺出一個標(biāo)

28、準(zhǔn)食品和 一個試樣食品，由5名評審員按圖3-12的各項目品 評打分，本例對48種試樣進(jìn)行了試驗。 (3)儀器測定 l對以下8個項目進(jìn)行測定： 水分，肉粒平均直徑，離液量(擠壓流湯 量)，應(yīng)力松弛，切斷試驗，咬斷剪壓)試 驗(用U形或V形模頭剪壓試樣)，咀嚼試驗(即 壓縮破壞試驗,測硬度、疏松度)，穿孔試驗(測 最大破壞應(yīng)力)。 (4)相關(guān)性分析。 l 將以上儀器測定值與感官側(cè)定值進(jìn)行相關(guān)性分析 (如表3-12所示)，可得到，與各項目感官評價相關(guān) 性最大的儀器測定項目(按最大相關(guān)性順序取前3 位)。 l 可以看出，與感官項目肉粒感、多筋性相關(guān)最大 的儀器側(cè)定方法為:刃狀壓頭剪切時的切斷功；硬 度

29、、固著性和咀嚼口感與穿孔試驗的最大應(yīng)力有 很高的相關(guān)關(guān)系；而油膩感僅與離液量有一定相 關(guān)，與其它測定項目結(jié)果無關(guān)。 (5)多元回歸分析。 l 進(jìn)行多元回歸分析找出代替感官評價最適合儀器測進(jìn)行多元回歸分析找出代替感官評價最適合儀器測 定值組合。定值組合。 肉餅的硬度感受可用咀嚼儀器側(cè)定和水分測定的數(shù)值肉餅的硬度感受可用咀嚼儀器側(cè)定和水分測定的數(shù)值 綜合判定綜合判定; 而彈性感和固著性感覺只與穿孔試驗的最大應(yīng)力有很而彈性感和固著性感覺只與穿孔試驗的最大應(yīng)力有很 高相關(guān)；高相關(guān)； 疏松感可用穿孔最大應(yīng)力和切斷強(qiáng)度值綜合判斷；疏松感可用穿孔最大應(yīng)力和切斷強(qiáng)度值綜合判斷； 咬斷性可用硬度值和切斷強(qiáng)度值綜

30、合判斷；咬斷性可用硬度值和切斷強(qiáng)度值綜合判斷； 油膩感雖然與儀器測定值相關(guān)不太大，但也還可用離油膩感雖然與儀器測定值相關(guān)不太大，但也還可用離 液全量，離液中脂肪量和液全量，離液中脂肪量和V形壓頭壓切強(qiáng)度三者綜合形壓頭壓切強(qiáng)度三者綜合 判斷。肉粒感用刃狀壓頭切斷功和平均肉粒直徑綜合判斷。肉粒感用刃狀壓頭切斷功和平均肉粒直徑綜合 判斷。判斷。 l 可見要代替感官評價，往往需要多種測定儀器綜合可見要代替感官評價，往往需要多種測定儀器綜合 判斷。判斷。 第三節(jié) 食品質(zhì)地的儀器測定 1. 質(zhì)構(gòu)儀質(zhì)構(gòu)儀-參數(shù)參數(shù) l Brittleness, crunchiness, and crumbliness, w

31、hich are a similar concept, can be measured as the ease with which the material fractures under an increasing compression load l 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 酥脆性酥脆性，易碎性、脆性

32、、脆度，易碎性、脆性、脆度 (originally called brittleness) is defined as the force at the first significant break in the TPA curve. Springiness（恢復(fù)性，彈性，回彈） l 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. Chewiness（咀嚼性） l Chewiness is defined as the produ