食品課件食分終極版10ash

1、Determination of ash content The significance of determination of ash contentThe general determination process of ash contentTeaching AimsClassification of Element for human health Major: Ca, Mg, P, K, Na, Cl, et al.Essential trace: Fe, Cu, Zn, I, et al.Harmful: Pb, Cd, Hg, et al.Definition:Ash: Tot

2、al amount of minerals present within a food Mineral content: The amount of specific inorganic components present within a food, such as Ca, Na, K and Cl. (crude ash)Crude ash: Is the inorganic residue remaining after the water and organic matter have been removed by heating in the presence of oxidiz

3、ing agents, which provides a measure of the total amount of minerals within a food. Determination of ash content Acid /water soluble ash content is more significant than total ash contentAcid soluable ash contentTotal ashWater soluable ash contentWater insoluable ash contentAcid insoluable ash conte

4、ntWater soluble ash contentmainly include the oxide and the salt of K, Na, Ca, Mg, etc Acid soluble ash contentmainly include the oxide of Fe、Al and subphosphate of alkaline-earth metalsAcid insoluble ash contentmainly include the contaminants and the content of SiO2Nutritional labeling: Some minera

5、ls are essential to a healthy diet (e.g., calcium, phosphorous, potassium and sodium) whereas others can be toxic (e.g., lead Pb, mercury Hg, cadmium Cd, and aluminum Al). Quality: The quality of many foods depends on the concentration and type of minerals they contain, including their taste, appear

6、ance, texture and stability (e.g. tea). Processing: It is often important to know the mineral content of foods during processing because this affects the physicochemical properties of foods(e.g. different grade of flour). Sanitary condition: Ash contents of fresh foods rarely exceed 5%. Significance

7、 of determination of the ash and mineral content Application exampleThe Classification of Flour: Ash is an important index of flour quality。The ash content in wheat bran is much Higher than that in endosperm. First grade: 0.3 0.5 % (dumpling)Standard grade: 0.6 0.9 %Flour TypesHard Wheat Flours Top

8、Patent0.35 - 0.40% ash content; 11.0-12.0% protein Uses: - Danishes, sweet doughs, yeast doughnuts and smaller volume breads and buns.First Bakers0.50 - 0.55%. ash content; 13.0-13.8% protein Uses: All purpose strong bakers flour, breads, buns, soft rolls and puff pastryFirst Clears0.70-0.80% ash co

9、ntent; 15.5-17% protein Uses: A dark very high protein flour used as a base for rye bread production; poor color not a factor in finished product.Second ClearsLow grade flour, not used in food production. Constitutes less than 5% of flour produced by a mill. Soft Wheat Flours Cake Flour0.36-0.40% as

10、h content; 7.8 - 8.5% protein, chlorinated to 4.5- 5.0 pH. Uses: High-ratio cakes (cakes with a high amount of sugar and liquid in proportion to flour), angel food cakes and jelly rolls.Pastry Flour0.40-0.45% ash content; 8.0-8.8% protein, chlorinated to 5.0-5.5 pH, (also available unchlorinated).Us

11、es: Cake, pastries and pies.Cookie Flour0.45-0.50% ash content; 9.0 - 10.5% protein Uses: Cookies and blended flours. For large-scale manufacturers, flour can be chlorinated to the users specifications.Whole Wheat FlourVarious bran coat granulations produce coarse to fine whole-wheatOrganoleptic/Sen

12、soryQualityPhysical-chemicalindexesSB/T 10157茶葉感官審評方法Natural Elements and Nutrients in Japanese Green Tea(unit:g)Tannin(Catechin)CaffeineTheanine/Amino AcidFatCarbo-hydrateFiberAshContentGyokuro10.03.511.16.3Sencha13.02.324.54.747.710.65.0Houjicha9.51.518.24.8Matcha10.03.230.65

13、.338.510.07.4(per 100g of tealeavesThe influence factor on ash content of teaThe variety and age of tea tree/ tea leafNormal condition: Total ash content tea:4%7.5 % Water soluble ash50 % (in total ash)Variety of tea E.g. black teaoolong teaThe sanitary condition of processAdulterationTotal ash: Hig

14、h content-older tea, contaminantsWater soluble ash: Higher proportion in total ash-good quality of teaAcid-insoluble ash: High content-bad quality of tea, more contaminantsBasicity of water soluble ash: the acid consumption neutralize the water soluble ash, can be used to identify the adulteration o

15、f tea (l%3%)The influence factor on ash content of teaSix chemical limit standards- Four ash indexesTotal ash: maximum 8%, minimum 4%Water soluble ash: (%total ash), minimum 45%Basicity of water-soluble ash(KOH) Maximum 3.0%, minimum1. 0% Acid-insoluble ash maximum 1. 0%ISO 3720-standard of black te

16、a Determination of Ash ContentPrinciple: Minerals are not destroyed by heating, and that they have a low volatility compared to other food components.Sample Preparation Typically, samples of 1-10g are used in the analysis of ash content.Solid foods are finely ground and then carefully mixed to facil

17、itate the choice of a representative sample. Samples that are high in moisture are often dried to prevent spattering during ashing process. High fat samples are usually defatted by solvent extraction, as this facilitates the release of the moisture and prevents spattering. CarbonizationMethodconstan

18、t weight Take out sampleCool down for 30minIn desiccator calculationAshingSample carbonizationPrepareporcelain crucible Preparemuffle furnace Weighing sampleYesNoSample amount: the ash amount should be 10-100 mg after ashing.e.g.Milk powder, seasoning, aquatic product 12gGrain and grain product, cak

19、e, etc 35g Vegetable and vegetable product, etc510g 。Fruit and fruit product 20gAshing condition (temperature and time) Constant weight processCooling down time in desiccatorPractical consideration in analysis of ash content GB: export teaTotal ash: 700 / 20min (fast analysis), 52525 arbitration and

20、 verify methodAnalysis of Mineral in foodISOAOACGB52525 Constant weight methodE.g. Grain, cereal or flour: 550 arbitration method 850 Ashing condition (temperature and time) system errorCrucibleSample + crucibleAsh + crucible Operating errorTemperature and time for ashingCooling time after ashing (T

21、oo long or too short) system error and operating error on ash analysisAnalytical balance water-soluble ash=total ash - water-insoluble ashThe analysis of Water-soluble ash and water-insoluble ash： ashless filter paper （ quantitative filter paper ）Three grade according to the ash content：I0.01 II0.03

22、 III0.06Total ash+hot water (25ml)tothecrucible containing totalashBoilgentlyfor5minDry, carbonize, ashing, cool down,Weigh till constant weightFiltrate andKeep the residue or waterFood analysis of acidity and pH Key points：The signifiance of acidity analysis in food productThe determination method

23、and it practical applicationTotal AcidityActive Acidity Volatile Acidity Total Acidity(TA)Hydrogen ions (H+) of both fixed and volatile acids present in foodActive Acidity (pH)pH is the hydrogen ion concentration H+ of a solution.Volatile Acidity (VA) Refers to the organic acids found in wine, grape

24、 juice etc that are more volatile or more easily vaporized than the non-volatile or fixed acids (malic acid) acetic acid , butyric acid Concept of AcidityConcept of AcidityAcidity in milkApparent acidity-Natural acidity derived from the alkali binding properties of casein , phosphates, citrates and

25、CO2. Usually it is between 0.15%-0.18%. (% lactic acid)True acidity/developed acidity -result from the fermentation of milk by lactic acid bacteria. When it is above 0.2%, lactic acid exists.0T: the volume of 0.1mol/l NaOH depleted by 100ml milk sample. The apparent acidity of fresh milk is 16-18 0T

26、Organic acids in foodsNatural componentsAdditiveFermentation productsPurpose: Color Taste and flavor PreservationJuice, beverage, fruit：taste-sugar/acid Brix/acidratioFermentation food product：The amount of volatile acidSoybean sauce：suitable amount of organic acidWine：acidity-important quality inde

27、xYellow rice wine: precursor substance of fragranceColor, taste, flavor and stability of foodE.G.Can：Related with sterilizing timeClarification effect of juiceOthers ：Restrain the production of unwanted browning (Maillard Browning) through the control of pHColor, taste, flavor and stability of foodE.G.Fresh milk: 1618 。T Fresh meat （pH）-（color, water holding capacity-WHC）-shelf lifeFood