1. Measurements of Starch Content in Cassava Presented: by SurachaiSungzikaw สุรชัย สังข์ศรีแก้ว Workshop on Metrology in Food Safety, Agricultural Products and Product Safety, Hangzhou, PR China, June 2-6, 2008

2. Overview • About Cassava • The Determination of Starch Content in Cassavas for Trade in Thailand • A Comparison of Starch Content Values Measured by Reimann Balance and Electronic Balance • A Comparison of Different Methods for Estimating Starch Content of Cassava Tubers between: - UnderwaterMethod and - Determination of Dry Matter by Oven Method

3. What is Cassava? • Cassavas are cultivated in most equatorial regions.

4. What is Cassava? (continuous) • Cassava tubers are long and tapered

5. What is Cassava? (continuous) • Cassava tubers are very rich in starch.

6. Source: International Starch Institute, Science Park Aarhus, Denmark

7. Products Derived from Cassavas Source: The world cassava economy, FAO

8. Determination of Starch Contentin Cassava Tubers for Trade in Thailand • Officially for trade, determined by Reimann Balancesverified by Weights and Measures Bureau • Also determined by the electronic scale in combination with computer-based calculations(under pattern testing)

9. 1. Determination of Starch Content by Reimann Balance . Weigh 5000 g clean tubers into upper basket in air

10. 1. Determination of Starch Content by Reimann Balance . Weigh 5000 g clean tubers in the upper basket in air Move the tubers into the lower basket under water

11. 1. Determination of Starch Content by Reimann Balance . Weigh 5000 g clean tubers into upper basket in air Move the tubers into the lower basket under water Weigh the tubers again in water Determine of Starch Content

12. 2. Determination of Starch Content by the electronic scale in combination with computer-based calculations Source: Genius Design & Engineering Co.,Ltd.

13. The Construction of the scale • Indicating Device • Load Cell • Basket (load‑receiving element) • Water Bucket • Hydraulic Lift Source: Genius Design & Engineering Co.,Ltd.

14. Measuring Procedure for Determination of Starch Content With clean water, lift the bucket to the empty basket until the basket is completely immersed in water. Weigh the empty basket immersed in water and record the weight of basket by the indicating device. Move the bucket back to the lower position.

15. Measuring Procedure for Determination of Starch Content Weigh 3-6 kg clean cassava tubers into the basket in air. Lift the bucket to the basket containing cassava tubers until the basket is completely immersed in water and weigh again. Starch content of the sampling is calculated by a microprocessor in the indicating device.

16. Comparison of Starch Content Values Measured by Reimann Balance and the Electronic Balance 1 Measuring by Reimann Balance

17. Comparison of Starch Content Values Measured by Reimann Balance and Electronic Balance 2 Measuring by the electronic balance

18. Samples

19. The procedure • Calibrated the Reimann Balance and electronic balance with class M1 standard mass • Programmed in the Computer of The Electronic Balance to calculate starch content by the following equation:

20. The procedure(continuous) Wo = weight of the cassava sample in air Wu = weight of the sample under water SG = specific gravity BC = basket compensated weight ( BC = weight in air – weight under water)

21. First determined starch content of 5 kg, 3 kg, and 1 kg wet clean tubers by Reimann Balance • Second determined starch content of the same samplesby the Electronic Balance

22. Results

23. Discussion • Basket’s weight compensation for the Electronic Balanceis significance for measurement of specific gravity by Under Water Weight method • Specification of the basket comprised with the Electronic Balance have to be considered

24. With the determination of cassava tubers by the Electronic Balance, there is no significant difference on the starch content values of by decreasing each sampling weight to 1000 g. from 5000 g.

25. A Comparison of Different Methods for Estimating Starch Content in Cassava Tubers

26. Objective • To revise the correlation equation between specific gravity and starch content of cassava tubers • To obtain the information for developing the Electronic Balances

27. Methodsof Determination of Starch Content • Under WaterWeight Method • Determination of Dry Matter by Oven at 130 C

28. The Experiments • The experiments were carried out to determine starch contents in the same samples by Under Water Weight method and by Oven method at 130 C

29. Apparatus • For Under Water Weight method • Analytical balance weighing to the nearest 0.01 g • Vessel with clean water • Stainless steel wire for hanging the sample weighed in water

30. Apparatus(continue) • For the Determination of Dry Matter by Oven Method • Analytical balance weighing to the nearest 0.1 mg • Dishes of aluminum with tight-fitting lids • Electrically heated oven • Desiccator containing an effective desiccant

31. The Procedure • Determined of specific gravity of cassava tubers by Under Water Weight method • Calculated starch content values with the following equation: Starch Content = (SG – 1.00906)/0.004845 %

32. Determined of dry matter of cassava tubers by Oven at 130 C • Calculated starch content values with the empirical equation published by FAO as follow: Percent Starch Content = Percent Total Dry Matter – 7.3 % Source: 1. ISI 01-1e Determination of Dry Matter in Starch by Oven Drying at 130oC, International Starch Institute, Science Park Aarhus, Denmark 2. Cassava processing, FAO

33. Comparison

34. Discussion • The starch content values estimated by UWW method are significant different from by Oven method • To confirm this, other reliable methods are required to make more comparison such as Krochmal and Kilbride or Near Infrared Reflectance (NIR) • The correlation equation between specific gravity and starch content of cassava tubers should be revised

35. Thank You for Your Attention A cassava field in Chonburi, Thailand