Determination of Fiber

Determination of Fiber

Name : T.L.V.Peiris Index No: GS/MSc/Food/3630/08 Date Performed:07/11/2009

Determination of crude fiber Introduction

In the analysis of cellulose-containing foods, the determination of crude fiber is widely used. Crude fiber includes theoretically, materials that are indigestible in the human and animal organism. It is determined as material insoluble in dilute acid and dilute alkali under specific conditions. The basic method is based on procedure developed by Hennenberg, Stohmann, and Rautenberg in 1864 in Germany. In the determination, 2g of material are defatted with petroleum ether and boiled under reflux for exactly 30 min with 200ml of solution containing 1.25g of sulfuric acid per100ml of solution. The solution is filtered through linen or several layers of cheese cloth on a fluted funnel and washed with boiling water until the washings are no longer acid. The residue is transferred quantitatively to a beaker, and boiled for 30 min with 200 ml of solution containing 1.25 g of carbonate-free sodium hydroxide per 100 ml. The final residue is filtered through a thin cut close pad of washed and ignited asbestos in a Gooch crucible, dried in an electric oven, weighed, incinerated, cooled and weighed again. The loss of weight is taken as crude fiber. The residue from a crude fiber determination contains about 97% cellulose and lignin. It does not represent, however, all the cellulose and lignin present initially. In addition, the crude fiber is a mixture of cellulosic materials and does not represent any specific compound or group of compounds. Despite its nonspecific composition, crude fiber is a useful parameter in food and feed analyses. Crude fiber is commonly used as an index of the feeding value of poultery and stock feeds, to evaluate the efficiency of milling and separating bran from starchy endosperm and in the chemical determination of succulence of fresh vegetables and fruits. Materials and Method Materials Round bottom flask Beaker Reflux condenser Sintered cursible (gooch crucible) Asbestos wool Desicator Heating mantle Weighing balance Sulphuric acid-dil Sodium hydroxide Litmus Paper Tea leaves Method

Determination of Fiber

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2g of tea was weighed into a 1 liter conical flask. Then 200ml of boiling H2SO4 and boil for 30 mins over a bunen burner while swirling occasionally to remove solids from adhereing to the solids from adhering to the sides of the flask. The hot solution was decanted through Buchner funnel fitted with whatman 52 filter paper. All residues was transferred and rinsed with boiling water until no colour change in litmus paper. Then the residue was transferred by using 200 ml 1.25% NaOH solution into a 1liter flask and brought to boil and maintained a gentle ebullition for 30 mins and filtered through rapid hardened filter paper and transferred the fiber quantitatively and washed with 1% HCl until the filtrate is free from alkali followed by distilled water ,15ml of alcohol and 10ml of diethyl ether. Then the residue was quantitatively transferred to a tared crucible and sired in the oven at 105OC and weighed after cooling. Then this was incinerated at 5000C and weighed after cooling. Calculations Moisture Content Weight of Sample

= 2.0701g

Weight of Sample + Crucible

= 15.3377g

Dry sample + Crucible

= 15.2036g

Moisture Content =

Weight Loss X 100 Weight of sample

= 15.3377g-15.2036g X 100 2.0701 =

6.47%

Weight of sample taken for fiber Analysis = 2.0001g Dry weight of Sample

= 2.001g X 93.53 100 = 1.8707 g

Weight of empty crucible= 30.1927g Determination of Fiber

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Crucible+ filter paper = 30.8510g After drying at 105oC in oven = crucible+ Fiber + ash= 31.0640g (m1) After incinerating at 550oC = crucible+ ash= 30.1965g ( m2) Fiber % =

m1-m2 X 100 Sample

= (31.0640g-30.8510g)-( 30.1965g – 30.1927g) X 100 1.8707g = 11.18 % Determination of Acid Detergent Fiber Materials Volumetric flasks (100ml,200ml) Measuring Cylinder Heating Mantle Sintered glass crucible Refluxing system Sulphuric acid Cetyl trimethyl ammonium bromide solution (5g of cetyl trimethyl ammonium bromide dissolved in 250ml 2M sulphuric acid) Method All glassware was cleaned and dried. 1g of tea sample was weighed and placed the materials in refluxing flask and 100ml of acid detergent solution was added. Then heated to boil and refluxed for 60 mins. Then removed the flask after cooling and filtered through a pre weighed crucible using minimum suction. Then washed twice with hot water (900C – 1000C) and then washed with acetone until no more colour is removed. Then dried at 105 oC for 3 hrs and weighed. Calculations Moisture content Weight of Sample = 1.004g Dry Weight =

1.004 X 93.53 100 = 0.9356g

Wt of crucible = 136.8689g Determination of Fiber

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Sample + crucible = 136.6471 + 1.004g = 137.6511g Wt of crucible + Sample after oven drying = 137.1632g % fiber content = Wt. of crucible + Sample- Wt. of crucible X 100 Wt. Sample taken ( 137.1632- 136.8689) X 100 0.9356 = 31.46 % (on dry basis) =

Discussion The maximum amount of crude fiber that can be present in tea is 16.5%. The above values show that this is up to standards. The low level of crude fiber may be due to the reason since this is blended tea. The rate of heating should be gently boiled. Filtering should be done as soon as possible since late filtration generally results in lower results. To reduce evaporation losses during boiling the reflux condenser is used. In digestion except fiber others are dissolve in sulfuric acid and NaOH . Hemicelluloses get dissolve in dilute alkali while pectin and hydrocolloids dissolve in hot water. Protein is denatured and lost in strong acid treatment. But mineral matter donot get dissolve in above treatments. Due to this these remain with insoluble fiber matters. To avoid this error ash content is determined and deducts the amount of ash from the fiber. A tea board standard for crude fiber is 16.5%. The sample that tested has 11.18 % crude fiber content. Experiment value is less than the value of commercial value. Therefore the sample is not adulterated with other materials. Since tea doesn’t contain fat, sample wasn’t defatted. Samples should be transferred quantitatively to avoid the loss of fiber. In final filtration ash less filter paper must be used, otherwise fibers of the filter paper may added to the fiber content of the sample.

Determination of Fiber

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