Encapsulation of extract prepared from irradiated onion scales in alginate beads: a potential functional food ingredient

Abstract

Onion scales were irradiated and the effects of irradiation on their bioactive properties were studied. The antioxidant and antibacterial activities of extract prepared from irradiated onion scales (upto 6 kGy) were comparable to the extract prepared from non-irradiated onion scales. OSE (0–6%) were encapsulated in 2% alginate beads. The beads containing 6% OSE had the highest a* and the lowest L* values as compared to neat beads that were prepared without OSE. The size of the beads reduced significantly from 2.42 mm (0% OSE) to 2.05 mm (6% OSE). The moisture content of neat (0% OSE) beads was 95.94% as compared to 93.86% in beads incorporated with 6% OSE. Alginate beads containing 6% OSE had the maximum swelling capacity. On basis of DPPH radical scavenging antioxidant assay it was observed that alginate beads containing 6% OSE showed the maximum antioxidant activity. In simulated gastric and intestinal fluid, the antioxidant activity of the beads containing OSE was retained. Irradiated minced chicken muscles containing 6% OSE alginate beads had lower TBARS value (2.0 mg MDA kg−1 meat) as compared to 3.3 mg MDA kg−1 meat for irradiated meat with 0% OSE. There was significant difference (almost 2 log cycle reduction) in the growth of Staphylococcus aureus, Pseudomonas fluorescens in chicken muscle during chilled storage when OSE encapsulated beads were incorporated. Hence, irradiation of onion scales and its encapsulation in alginate beads has a great potential as a functional ingredient in various food products.