Effect of gamma ray irradiation and packaging on the storage quality of kodo millet (Paspalum scrobiculatum L.) flour

Kodo millet is one of the small millet species, grown widely in the tropical/subtropical regions. In order to prevent the problem of post-harvest losses, various preservation techniques have been used such as irradiation and suitable packaging material. In the present study, shelf life of kodo millet flour was investigated using gamma rays at 1.5 kilogray (kGy) (irradiation, IR) and different packaging materials including low-density polyethylene (LDPE), polypropylene (PP), polyethylene terephthalate (PET) and metallized polypropylene (MPP) for a period of three months. Every fortnight the samples from these treatments were drawn for biochemical changes (moisture, peroxide value, alcoholic acidity and FFA), insect infestation and microbial growth. By the end of storage period, significant (P < 0.01) increase of moisture, peroxide value, alcoholic acidity and FFA content was noticed in the control samples followed by non-irradiated PP (10.50 %, 3.8 mEq/Kg and 1.25%) and LDPE (9.48 %, 3.4 mEq and 1.20 %) packed flour as compared to irradiated MPP and PET packed samples. Insect infestation started after 15 days of storage in steel boxes which increased in countless numbers by the end of storage period. Similarly, insect population was noticed after 30 and 60 days in non irradiated and irradiated PP and LDPE covers respectively. While, there was no insect infestation in case of irradiated MPP and PET packed flour. Significant increase of bacterial load was observed in the control followed by non irradiated PP (4.2 cfu/g) and LDPE (3.8 cfu/g) covers. Sensory tests indicated that the irradiation has no adverse effect on the taste, appearance, flavor and overall acceptability (OAA) of the flat bread made from flour samples stored in these packaging materials. Thus, the kodo millet flour stored in MPP and PET pouches with irradiation dose of 1.5 kGy found to be suitable for safe storage up to three months under room temperature.