Lab Report Food Analaysis-moisture
TITLE OF EXPERIMENT Practical 1- Determination of Moisture
INTRODUCTION Moisture content evaluation is very important in food industry in order to ensure the quality and required standards of food products. Basically the shelf life is highly related to the moisture proportion present in foods. That is, Legal and Labeling Requirements. There are legal limits to the maximum or minimum amount of water that must be present in certain types of food. Secondly, Economic. The cost of many foods depends on the amount of water they contain - water is an inexpensive ingredient, and manufacturers often try to incorporate as much as possible in a food, without exceeding some maximum legal requirement. Next , Microbial Stability. The propensity of microorganisms to grow in foods depends on their water content. For this reason many foods are dried below some critical moisture content. Furthermore, Food Quality. The texture, taste, appearance and stability of foods depends on the amount of water they contain. Lastly, Food Processing Operations. A knowledge of the moisture content is often necessary to predict the behavior of foods during processing, e.g. mixing, drying,flow through a pipe or packaging. Chemically there are several methods to estimate water percentage. That is, Oven Drying Methods. With oven drying, the sample is heated under specified conditions, and the loss of weight is used to calculate the moisture content of the sample. Next, Distillation Methods. Distillation techniques involve cod stilling the moisture in a food sample with a high boiling point solvent that is immiscible in water, collecting the mixture that distils off, and then measuring the volume of water. Includes direct and reflux distillation. Furthermore, Chemical Methods—Karl Fischer Titration. This technique is particularly suited to food products that show erratic results when heated or submitted to a vacuum.
It is the method of choice for low-moisture foods such as dried fruits and vegetables, candies, chocolate, roasted coffee, oils and fats, and low-moisture foods high in sugar or protein.
A. OVEN DRYING METHOD
OBJECTIVE To determine the moisture content of selected food samples using drying oven method.
PRINCIPLE The method is based on evaporation of water in food sample. A known weight of food sample is dried under specified conditions until constant weight is attained the loss of weight is equated to the moisture content of the food sample.
APPARATUS Aluminum dish, analytical balance, drying oven, desiccators and spatula.
PROCEDURE 1. An aluminum dish with cover was dried for 4 hours in an oven at 105 degree Celsius. The dish was transferred into the desiccator to let it cool and been weighed after it has attained room temperature. 2. 5g of homogenized sample was weighed approximately into the aluminum dish. 3. The sample was laced uncovered, in the oven overnight at 60 degree Celsius or 100-105 degree Celsius for 5 hours. 4. Lid was replaced while dish was still in the oven, dish was removed from oven. Cool in desiccator and was weighed after attaining room temperature. The weighed obtain was recorded. 5. The drying process (step 3 and 4) were repeated until constant weighed was achieved.
Calculate percentage moisture (wt/wt) : (Wt of wet sample + pan) – (Wt of dried sample + pan) x 100 (Wt of wet sample + pan) – (Wt of pan)
RESULTS As shown in Table 1.1 and Table 1.2
DISCUSSION In this practical, we have learned how to determine the moisture content of selected food samples using drying oven method. In this experiment, biscuit and instant noodle was used as a sample. It was dried uncovered in the oven overnight at 6 C, after it removed from oven and cooled it down in desiccator, it was weighed after attaining room temperature. The weight was recorded in Table 1.1 on Data Sheet. Based on our results shows biscuit has moisture of 14.62 % while an instant noodle has 12.28%. If we compared both of them, biscuit has higher moisture than noodles. For theoretical value, moisture content for biscuit is ranged within 2% to 4 %. Meanwhile, for instant noodles its moisture content between 3% to 6 %.
Thus, we can see there has
significant change between the sample value and theoretical value. The difference between our value and the theoretical value too far. This is unacceptable value and it is not in a logical state. The error may occur during this experiment is instrumental error. The weighing balance has a zero error and it may be due to personal error. Furthermore, the sample itself can be a cause to the error. The sample was exposed to air for a long period and before we do the experiment the sample was kept in refrigerator. This cause the sample has higher moisture content when we kept in refrigerator. To overcome this error, make sure the entire instrument in a good condition before do the experiment.
B. DRYING METHOD (MOISTURE ANALYSER)
OBJECTIVE To determine the moisture content of selected food samples using moisture analyser.
PRINCIPLE Measurement of moisture content based on thermogravimetric principle. Sample placed on the sample pan then is weighed and heated under controlled high heat condition. Water evaporates due to heat generated by halogen radiator. The instrument measures the loss of weight and calculates percentage moisture automatically.
APPARATUS MB45 Halogen Moisture Analyser (Ohaus Corporation), sample pan and spatula.
PROCEDURE 1. The ON/OFF button was press to switch on the Moisture Analyser. 2. The test menu button was pressed and the drying parameter is set based on the following: Drying Temperature Profile Switch Off Time Display Set Target weight Program
: 150 oC : Standard : 15 minutes : % moist : 1g : Auto switch-off
3. The covered of the instrument was opened and the pan was cleared 4. The empty sample pan was placed in the pan handler and the pan handler was placed in the sample chamber. The tongues of the pan handler in ensure fits exactly in the slot of the draft shield element and the sample pan lie flat in the pan handler. 5. The TARE button was pressed to set reading to zero. 6. About 1g of sample was place and been distributed in the sample pan. The cover was closed. 7. The START/STOP button was pressed to start the drying process. 8. The result display for moist % was read and been recorded by the end of the drying process. 9. The cover was opened and carefully lifts the pan handler from the chamber to remove the sample.
DISCUSSION The moisture content which results from oven drying method and drying method depends on the type of foodstuff used. Water in a food item can be present in 2 ways which is Free water (which is physically linked to the food matrix and easily lost by evaporation or drying as a separate constituent)and bound water ( include water molecules chemically bonded to ionic and polar groups or water of crystallization or hydrates which is difficult to remove). In this practical, we have learned how to determine the moisture content of selected food samples using moisture analyser. In this experiment, wheat flour was used as a sample. It was dried and analysed by using moisture analyser. The weight was recorded in Table 1.2 on Data Sheet. The results shows wheat flour has moisture of 13.40%. Meanwhile, for theoretical value is 14%. Thus, we can see there has no significant change and the sample was proved that it has reached the theoretical value. Wheat flour with high moisture content (greater than 14.5%) attracts mould, bacteria, and insects, all of which cause deterioration during storage. Flour with low moisture content is more stable during storage and does not easily to spoil.
1) Identify five factors that you need to consider when choosing a moisture analysis method for a specific food product. Moisture content, nature of other food constituents, equipment availability, speed, accuracy & precision and purpose .
2) In the drying oven method, why do you allow the sample to get cool before weighing? The balance in calibrated to work at a specific temperature, if the object being weighed transfers heat into the balance pan it will heat things up. Metal expands and contracts with different temperature, even a slight temperature change can cause enough change in distance of the internal components to give bad readings. Another is the air. The heat will transfer to the air. If the balance is in a enclosures (which it should be to remove any variations do to air current), when the temperature of the air increases the pressure inside the closed container will increase; pushing down more on the balance pan throwing off the reading.
3) What the advantages and disadvantages from methods conducted ? OVEN DRYING METHOD
DRYING METHOD ( MOISTURE ANALYSER)
• large number of samples
• fast measurement
at same time, thus higher
(approx. 5–10 min.)
throughput possible • large sample volumes possible • large sample volumes possible
• easy handling • reduced risk of error
• high accuracy DISADVANTAGE • measurements only available after
• sample material may decompose or
• sample material may decompose
• no automation possible
• other liquid components such as alcohol, flavors, or acetic acid evaporate • laborious procedure with several working steps • very high risk of error (particularly during manual data entry and calculation) • high risk of error when using hygroscopic sample material
• only one measurement can be performed at a time
REFERENCES 1) M. Ustun Ozgur, G. Alphogen & I Koyuncu, Determination of Moisture page 621634 . 2) http://www.conradfp.com/pdf/ch12_Drying_Control_of_Moisture.pdf 3) http://www.grainscanada.gc.ca/guides-guides/moisture-teneur/guide/mdg-ddte4) http://foodquality.wfp.org/FoodSpecifications/NoodlesFortified/InstantNoodles/ta bid/132/Default.aspx 5) http://www.foodtechsource.com/rcenter/tech_data/td_moisture.htm 6) http://www.tis-gdv.de/tis_e/ware/gemuese/moehren/moehren.htm 7) http://www.wheatflourbook.org/p.aspx?tabid=18 8) http://ezinearticles.com/?Moisture-in-Food-Products&id=3834719
CONCLUSION The objective for this experiment is to determine the moisture content of selected food samples using drying oven method and to determine the moisture content of selected food samples using moisture analyser. In conclusion, now we know how to determine the moisture content of selected food samples using drying oven method and using moisture analyser. As a results, the value that we get are biscuit has moisture of 14.62 % while instant noodles has 12.28% by using drying oven. While by using moisture analyser, flour has moisture of 13.40%. The objective was achieved.