Effect of bacteriocin-incorporated alginate coating on shelf-life of minimally processed papaya (Carica papaya L.)

• Alginate coating minimized weight loss by preventing water vapour transmission.
• Alginate coating delayed ripening and maintained physico- chemical characteristics.
• Bacteriocin incorporated alginate coating inhibited microbial growth till 21 days.

Alginate coatings can act as carriers of antimicrobials to prolong the shelf stability of minimally processed fruit. Different concentrations of alginate (1, 1.5, 2% (w/v)) incorporated with bacteriocin (0, 20% (v/v)) as a coating material of minimally processed papaya were evaluated for quality parameters viz. firmness, weight loss, colour, head space gas composition, acidity, total soluble solids and microbial load for a period of 21 days. After 21 days of incubation, coated and uncoated samples showed decreases in O2 levels and acidity percentage which were 1.8 and 2.7 times more in uncoated as compared to the coated samples, respectively. The level of CO2 increase was 1.7 times higher in uncoated samples as compared to the coated samples. High respiration rate in uncoated samples led to increases in TSS values, firmness and weight loss. On the other hand, the alginate coating (with or without bacteriocin) acted as a barrier to water vapour transmission and gas exchange, which hindered changes in TSS values, firmness and weight loss in coated samples, which were 3.8, 8.7 and 7.4 times less than for the uncoated samples, respectively. Decreases in ‘b’ and increases in ‘a’ values were more pronounced in the case of controls and became less prominent with the alginate coating. A decrease in ‘b’ values and concomitant increase in ‘a’ values was due to the change from yellow to red colour, indicating ripening of papaya. Microbial counts by the end of the storage period in the alginate coated sample incorporating bacteriocin were 103 CFU/g as compared to 107 CFU/g in the case of the control. Alginate (2% (w/w)) with bacteriocin could be used to store minimally processed papaya for 3 weeks without compromising physico-chemical qualities or microbial safety.