Phosphine Sorption on Paddy Rice: Effects on Fumigation and Grain Quality Parameters.

Area of Science:

• Agricultural Science
• Pest Management
• Food Science

Background:

• Insect pests cause significant quantitative and qualitative losses in stored grains.
• Phosphine gas fumigation is a common method for controlling these pests.
• Rice husk exhibits high phosphine adsorption, potentially compromising fumigation efficacy and increasing residues.

Purpose of the Study:

• To evaluate phosphine sorption and residue in rice husk, paddy rice, and brown rice.
• To assess the impact of fumigation on the industrial quality of rice (head rice yield, rehydration capacity, cooking time, color).
• To determine if phosphine fumigation maintains effective pest control concentrations in different rice matrices.

Main Methods:

• Fumigation of paddy rice, brown rice, and rice husks with phosphine (3.0 g·m⁻³ for 240 h).
• Measurement of phosphine sorption rates in each material.
• Analysis of phosphine residues in treated materials.
• Evaluation of industrial quality parameters (head rice yield, rehydration, cooking time, color) of brown and white rice.

Main Results:

• High phosphine sorption rates were observed in rice husk (94.77%) and paddy rice (97.61%), with lower sorption in brown rice (35.17%).
• Only brown rice maintained phosphine concentrations above the effective pest control level (400 ppm for 120 h).
• Rice husk showed higher-than-permitted phosphine residues (0.25 ppm). Non-fumigated samples had lower head rice yields. Fumigated samples exhibited improved rehydration capacity and reduced cooking times.

Conclusions:

• The high sorption capacity of rice husk and paddy rice can lead to ineffective phosphine fumigation and increased residues.
• Brown rice appears to be the most suitable matrix for maintaining effective phosphine concentrations during fumigation.
• Further research is needed to optimize phosphine fumigation strategies for paddy rice due to its high sorption rate.