Gamma Irradiation of Brown Rice: Effects of Dose, Variety, Paddy Age, and Packaging on Fungal Control, Shelf-Life and Post-Harvest Cost Estimate

G.B.  Abrera; G.  Diano; M.M.  Tolentino; M.C.B.  Gragasin; M.L.C.  Cobar; G.  Caraos; Z.M. De Guzman; H.M.  Solomon; C.O.  Asaad; C.C.  Deocaris

doi:10.18502/jfqhc.12.2.18863

G.B. Abrera Biomedical Research Section, Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI), Commonwealth Avenue, Diliman, Quezon City, Philippines
G. Diano Biomedical Research Section, Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI), Commonwealth Avenue, Diliman, Quezon City, Philippines
M.M. Tolentino Biomedical Research Section, Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI), Commonwealth Avenue, Diliman, Quezon City, Philippines
M.C.B. Gragasin Philippine Center for Postharvest Development and Mechanization, Science City of Munoz, Nueva Ecija, Philippines
M.L.C. Cobar Biomedical Research Section, Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI), Commonwealth Avenue, Diliman, Quezon City, Philippines
G. Caraos Biomedical Research Section, Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI), Commonwealth Avenue, Diliman, Quezon City, Philippines
Z.M. De Guzman Biomedical Research Section, Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI), Commonwealth Avenue, Diliman, Quezon City, Philippines
H.M. Solomon Irradiation Services Section, Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI), Commonwealth Avenue, Diliman, Quezon City, Philippines
C.O. Asaad Biomedical Research Section, Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI), Commonwealth Avenue, Diliman, Quezon City, Philippines
C.C. Deocaris Biomedical Research Section, Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI), Commonwealth Avenue, Diliman, Quezon City, Philippines

DOI: https://doi.org/10.18502/jfqhc.12.2.18863

Keywords: Aspergillus niger, Food Contamination, Food Irradiation, Food Packaging, Radiation, Gamma

Abstract

Background: Brown rice offers superior nutritional value compared to polished white rice but is less favored in rice-consuming countries due to its limited shelf-life. This study evaluates the efficacy of gamma irradiation in reducing fungal contamination in brown rice and extending its shelf-life, considering factors such as paddy age, rice variety, and packaging type.

Methods: The efficacy of gamma irradiation (0-1 kGy) in reducing fungal contamination in brown rice was evaluated. RC-160 and SL-7 rice varieties (240 kg per variety) were harvested from Central Luzon (Region III) during the dry season (March–April 2023). One kg of two and eight-week-old paddy grains were packed in either Super Bag™, an International Rice Research Institute developed hermetic packaging, or conventional Polyethylene bags. Mold and Yeast Counts were quantified using 3M Petrifilm™ following Association of Official Agricultural Chemists official methods. Fifty g of each sample were homogenized in Butterfield’s phosphate buffer, serially diluted, plated, and incubated at 25±1 °C for 3-5 days. Statistical analyses were performed using one-way ANOVA and Tukey’s HSD post-hoc test with Statistical Tool for Agricultural Research (STAR) software, version 2.0.1 (IRRI).

Results: Gamma irradiation at one kGy significantly (p<0.05) reduced Mold and Yeast Counts, with effects sustained for up to eight months. Paddy age and packaging type had no significant influence on fungal load. A dose of 0.58 kGy achieved a 1-log (90%) reduction in Aspergillus niger, while 3 kGy achieved complete inactivation, extending shelf-life up to six months. Cost analysis showed irradiation, logistics, and added storage fees increased retail price per kg by 0.14, 0.04, and US$0.02, respectively.

Conclusions: Gamma irradiation effectively controls fungal contamination and extends brown rice shelf-life, potentially enhancing consumer confidence and promoting wider adoption of brown rice.