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Effect of Different Soaking Time on Fe and Zn Content of BRRI Dhan29

Sharifa Sultana Dipti, PhD
Principal Scientific Officer
Grain Quality and Nutrition Division, BRRI

Abstract/ Executive Summary:

The major cause of Zinc deficiency was low intake due to diets consisting mostly of a few staple foods with low micronutrient density e.g. polished rice. Modifications to the zinc content of rice could provide a useful opportunity to deliver larger amounts of dietary zinc to the population. As the effect of soaking and parboiling procedures have not yet been studied systematically for their impact on iron content of rice, the present study was conducted to test a range of variables that represent the range of methods presently used in Bangladesh. Longer soaking time resulted in a significant trend towards lower Fe and Zn content in both brown and 10% milled samples (P <0.05). Considering the 10% milled samples where water was not changed, Fe decreased by 25% between 0 and 48 hours soaking time while Zn decreased by 19%. Changing of soaking water had a significant, positive effect on Fe and Zn content across soaking times of 24-48 hours (P <0.05), with the exception of zinc in brown rice, which was not significantly different. The longer pre-steaming time of 5 minutes compared to 2 minutes did not have a significant effect on Zn content of brown or 10% milled rice in either the open or pressure parboiling systems. There was, however, a consistent trend to lower iron content across all soaking and steaming conditions, but this was only significant in the brown and 10% milled samples using open steaming for parboiling.

Keywords: Soaking, Parboiling, Rice, Iron, Zinc

Location: Grain Quality and Nutrition Division Laboratory, BRRI HQ

Start Date: 01-07-2012

End Date: 01-06-2013

Program Area: Quality and Nutrition

Commodity: Rice

Objectives:

To establish the optimum time and temperature of soaking before parboiling which retain most micronutrients.

Methodology:

The studies were focused on only one common Boro rice variety (BRRI dhan29). The study result for this variety is assumed to be demonstrative of the effects that would be observed in other major Bangladeshi rice varieties. For all the soaking experiments 1 kg of paddy for each treatment was soaked in 2.5 L of de-ionized water in plastic pails, just enough to cover the paddy. The ambient temperature was ±25°C throughout the soaking period. For the water change treatment of 24, 36 and 48 hours soaking time were used and water was changed after every 12 hours and 2.5 L of water was added every time. Two pre-steaming treatments were used for the experiment i.e., 2 minutes pre-steaming and 5 minutes pre-steaming. After 2 minutes pre-steaming, when water was added, the temperature of the soaking water increased to 37°C but eventually water temperature became 30°C. After 5 minutes pre-steaming, the soaking water temperature increased to 38°C but again stabled to 30°C. Pre-treatment steaming was done using the Autoclave at GQN Division, BRRI. Each of the soaking treatment will test the effect of duration of soaking on nutrient content of rice. For the ambient temperature soaking, water changed soaking and pre-steaming soaking, open steam parboiling (30 minutes at 100°C, 0 pressure) and pressure steam parboiling (10 minute at 1 kg/cm²) were used for replication of commercial methods followed by sun-drying, dehusking, and milling to produce both brown rice samples (0% milled) and polished rice samples (10% milled).

Source of Information: Proceedings of the BRRI Annual Internal Review, 20012-2013

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Longer soaking time resulted in a significant trend towards lower Fe and Zn content in both brown and 10% milled samples (P <0.05). Considering the 10% milled samples where water was not changed, Fe decreased by 25% between 0 and 48 hours soaking time while Zn decreased by 19%. Between 24 and 48 hours soaking time, the reduction in iron content was 16% and the reduction in zinc content was 8% in the 10% milled samples. Changing of soaking water had a significant, positive effect on Fe and Zn content across soaking times of 24-48 hours (P <0.05), with the exception of zinc in brown rice, which was not significantly different. Effect of open parboiling after 2 min. pre-soaking before soaking paddy for different soaking time there was not much change in Fe content in all the soaking time for brown and polished rice. However Zn loss was observed after 6 h soaking in case of brown rice. Polished rice did not show much loss in Zn content. Effect of pressure parboiling after 2 min. pre-steaming before soaking paddy for different soaking time there was no visible change in Fe content in both brown and polished rice. Zn content, however, changed with increasing soaking time for both brown and polished rice. Effect of open parboiling after 5 min. pre-steaming before soaking paddy for different soaking time there was no visible change in Fe content in both brown and polished rice and Zn content of brown rice. However, Zn content slightly decreased with increasing soaking time for polished rice.

Knowledge Management: Report/Proceedings