Determination Of Moisture Content 5x1x3y

DETERMINATION OF MOISTURE CONTENT

Name:T.L.V. PEIRIS Index no : GS/MSc/Food/3630/08 Date Performed: 21/11/2009

1. DETERMINATION OF MOISTURE CONTENT BY OVEN DRYING METHOD INTRODUCTION The moisture content which results from oven drying method depends on the type of food stuff used. The determination of moisture in a food is done for many purposes such as assessment of quality, quality control, quality assurance, detection and estimation of adulteration, conformity with food standards and other statutory requirement, calculation of total food solids content, assessment of stability, shelf life and storage life. Water in a food item can be present in 2 ways: • Free water (which is physically linked to the food matrix and easily lost by evaporation or drying as a separate constituent) • Bound water ( include water molecules chemically bonded to ionic and polar groups or water of crystallization or hydrates which is difficult to remove) These types may occur in varying quantities in food and are held by physical chemical forces of diverse nature. Even though the accuracy and precision of moisture result is low; the reproducibility results can be obtained under a set of standardized condition. • • • •

The water activity of any product depends on, The chemical composition of food The state of aggregation of its constituent The water content Temperature of the product The shelf life of the product depends on water activity. Moisture can be determined by using following methods, • Thermal Drying method Drying either hot air oven at 1050C in 2-3 hours or in vacuum ovens which is widely used for sugar based foods. The measurement of the weight loss which results due to the evaporation of H2O at or near boiling point is taken here. The loss in weight depend on the particle size, weight of the sample used, type of the dish and temperature variation in the ovens etc. • Chemical assay This is based on the non-stoicheometric reaction of water. • Physical method Involves physical and physiochemical reaction in food. Oven drying method is widely used. The weight loss due to the removal of water by heating under specific conditions is considered here. The loss of weight due to drying is considered as a measure of the moisture content of the sample.

MATERIALS AND METHOD Determination of moisture

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MATERIALS Moisture dish made of stainless steel Oven maintained at 105 0C Weighing balance Cinnamon sample METHOD About 5 g of the sample was weighed in to a moisture dish which was previously dried in an oven and weighed. Then the uncovered dish was dried along side for 21/2 hrs. The dish was covered and was transferred to desiccators and weighed quickly as possible as the dish was cooled. The heating and weighing procedures was repeated until successive weight did not differ by more than one milligram .Loss in weights were recorded. RESULTS AND CALCULATIONS Weight of dish Weight of sample(g) Initial weight(g) Weight of dish + lid + sample(after drying)(g)

1st time 2nd time 3rd time 4th time

1st Sample/g 44.4284 5.0418 49.4702 49.3185 48.9075 48.7088 48.7088

2nd Sample/g 54.2295 5.0785 59.3080 58.8285 55.8084 54.4858 54.4858

3rd Sample/g 46.9371 5.0197 51.9468 51.5003 51.4825 51.1642 51.1642

RESULTS CALCULATIONS Moisture % m/m

m1 m2 m3

=

Weight loss x 100 Weight of the sample

=

m2-m3 m2-m1

= = =

Weight of empty dish Weight of empty dish + sample before drying Weight of empty dish + sample after drying

Determination of moisture

x

100

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1st Sample Weight of dish (g)( m1 ) 44.4284 Weight of sample before drying(g) 5.0418 Weight of dish (g)+ Weight of 49.4702 sample before drying(g) ( m2 ) Weight of dish+sample(after drying) 48.7088 (g)( m3 ) m2-m3 x 100 15.10 m2-m1

Moisture Content of Cinnamon

=

2nd Sample 54.2295 5.0785 59.3080

15.10+16.19+15.19 3

3rd Sample 46.9371 5.0197 51.9468

54.4858

51.1642

16.19

15.19

=

15.69 %

DISCUSSION Oven drying method is widely used in determination of moisture. Water is removed due to heating at 105 °C. Loss of weight due to vaporization of water is taken as weight of moisture. But spices like cinnamon contain volatile oil in addition to moisture and these volatile oils also get loss during oven drying. Due to this the weight loss due to the loss of volatile oils also gets counted for moisture determination. This is the main disadvantage of oven drying method. This method is not suitable to determine the moisture content of thermally unstable compounds and this method removes only free water. Since oven drying method is simple, low cost and easy, it is widely used for routine analysis. The accuracy of results of moisture determination is affected by, drying temperature, relative humidity, particle size of sample, handling method of sample, amount of sample, type of evaporation dish, variation in temperature inside the oven. To minimize these errors various precautions should be taken. i.e. sample should be dried in stainless steel containers, which is not decompose during heating. Three consecutive samples were carried out to eliminate the errors of the handlers, usually 5 g of ground sample was taken to facilitate the drying, and this encourages the evaporation because particle size is small.

2. DETERMINATION OF MOISTURE CONTENT BY DEAN STARK DISTILLATION METHOD Determination of moisture

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INTRODUCTION Distillation methods are particularly useful for foods with low moisture content and for products containing volatile oils such as herbs and spices. Since the oils remain dissolved in the organic solvent the disadvantages are that they have often been reported to give low values and their requirements for flammable solvent pose small but significant hazards. Dean & Stark Distillation Unit

The Dean and Stark method is widely used in determination of moisture. A known weight of food is placed in a flask with an organic solvent such as xylene or toluene. The organic solvent must be insoluble with water; have a higher boiling point than water; be less dense than water; and be safe to use. The flask containing the sample and the organic solvent is attached to a condenser by a side arm and the mixture is heated. The water in the sample evaporates and moves up into the condenser where it is cooled and converted back into liquid water, which then trickles into the graduated tube. When no more water gets collect in the graduated tube, distillation is stopped and the volume of water is read from the tube. Distillation with a boiling liquid provides an effective means of heat transfer, the water is removed rapidly. If the boiling liquid is lighter than the water, the collecting trap usually contains a tube with tap at the bottom and calibrated upward. This form requires reading only one meniscus in measuring the amount of collected water. The calibrated portion of the tube may be cooled by a water bath to standard temperature. Many difficulties may arise in the determination of moisture by distillation method. These include relatively low precision of the receiving measuring device, difficulties in reading the meniscus, adherence of moisture droplets to the glass, over boiling, suitability of water in the distillation liquid, incomplete evaporation of water and underestimation of moisture contents, and distillation of water-soluble components. Adherence of water to the walls of the condenser tube of sides of the receiving tubes can generally be prevented by using thoroughly cleaned glassware. Use of small amount of wetting agent will also improve meniscus reading. Incomplete recovery of water due to the formation of an emulsion can be avoided by adding small amount of amyl or isobutyl alcohol. MATERIALS AND METHOD MATERIALS Dean Stark Distillation unit Determination of moisture

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Measuring cylinder Beaker (250 ml) Drying oven Weighing balance Toluene METHOD All the glass wares were cleaned and dried in an oven. 50 ml Toluene solution and some pumice stones were added to a boiling flask. The calibrated arm was fixed on the flask and was boiled until the graduated tube gets constant volume of water.2.00 ml of water was added to the flask and was boiled until constant volume obtained. Then accurately weighed (about 2 g) was added and boiled until the graduated tube indicates a constant volume for the extracted water layer. This is equal to the same value of water in gram. RESULTS AND CALCULATIONS RESULTS Volume of the samples 2 ml of water Sample X ml

Volume indicated in graduated tube from the sample volume 1.95 ml 1.03ml

CALCULATIONS % moisture m/m =

Volume of water collected in the graduated tube Weight of the sample

X 100

Volume of water added to the flask Recovered volume of water after distillation Correction factor Weight of sample Volume of water contained in the sample

= = = = =

2.0 ml 1.95 ml 2.0 / 1.95 = 1.026 2.0172 g 0.2 ml

Volume of water (x correction factor) Moisture content %

= = = =

0.2 x 1.026 = 0.2052 0.2052/2.0172 x 100 10.17 % 10.17 %

Moisture content of cinnamon DISCUSSION

In this practical we have used toluene as the solvent. There are few reasons to do so, Advantages in using toluene, 1) It is immiscible with water .Then we can get a measurement. Determination of moisture

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2) Low density than water. 3) It has a high boiling point. So we can heat the sample till we get the whole water amount out. 4) Toluene will dissolves all the volatiles in the sample. So we can get the pure measurement. Advantages in this technique, 1) Less contamination can happened 2) Fewer utensils needed. 3) No need to pay much attention. Disadvantages in this technique 1) Water drops will remains on the walls of the distillate tube. So can get a wrong measurement. Dean & Stark method is suitable for determination of moisture in foods containing volatile matters. But this method is not suitable for routing testing and is employed only when conventional oven drying method is not suitable. It is also not suitable determine small amount of water. It needs little attention, no contamination. The solvent should be irreversible, higher boiling point and lower specific gravity than water. Since toluene has high boiling point (110-111 °C), lower density (0.86 g/ml) and immiscible with water, it was used as the solvent. Other than the toluene, heptane, xylene a mixture of N-amyl alcohol and xylene can be used as solvent. For high precision, a distillation factor correction was done by standardizing the apparatus with known amount of water and measuring the recovered amount water. Method of moisture determination is varied according to the sample to be tested. i.e. viscose foods such as oils, fats done by adding clean dry sand , which facilitate evaporation by increasing surface area and to avoid formation of films and crusts. Due to the experimental errors we got higher value for moisture content.

Determination of moisture

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