Acidified sodium chlorite as an alternative to chlorine to control microbial growth on shredded carrots while maintaining quality

Shredded carrots are particularly susceptible to microbial growth and quality deterioration as a result of a large cut surface area to mass ratio. Acidified sodium chlorite (ASC) in the concentration range 500-1200 microliter L⁻¹ has been shown to have stronger efficacy against pathogens and spoilage bacteria than chlorine and does not form carcinogenic products. However, ASC in this concentration range aggravates tissue damage. The objective of this study was to optimize ASC treatment parameters to balance antimicrobial activity with quality retention of shredded carrots. Shredded carrots were immersed for either 1 min in 100, 250 or 500 microliter L⁻¹ ASC solutions or 2 min in 200 microliter L⁻¹ chlorine or water (control). Treated samples were spin-dried and packaged in polypropylene bags and stored at 5 °C for up to 21 days. Carrots were evaluated at 7-day intervals for visual appearance, package atmosphere composition (O₂ and CO₂), product firmness, tissue electrolyte leakage and pH. The microbial growth, including total aerobic bacterial counts, total coliforms/Escherichia coli, yeast and mold counts and lactic acid bacterial counts on the products was also determined. Treatments with all concentrations of ASC reduced the aerobic bacterial counts, coliform/E. coli counts, yeast mold and counts and lactic acid bacterial populations by 1.2-2.0 log cfu g⁻¹ when compared with the water-washed and unwashed samples. During storage, unwashed samples had a sharp increase in lactic acid bacterial populations accompanied by a sharp decline in pH readings and rapid loss in firmness and tissue integrity; samples washed with 100 microliter L⁻¹ ASC maintained the best overall visual quality, accompanied by the retention of tissue integrity and firmness. Therefore, 100 microliter L⁻¹ was determined as the optimum concentration of ASC for maintaining overall quality and firmness, inhibiting microbial growth and prolonging the shelf-life of shredded carrots.