Impact of a decontamination step with peroxyacetic acid on the shelf-life, sensory quality and nutrient content of grated carrots packed under equilibrium modified atmosphere and stored at 7 degrees C

Peroxyacetic acid (PAA) is a strong oxidizer and exerts antimicrobial properties. The effect of a decontamination step with 80 and 250 mg L-1 PAA on shelf-life of grated carrots stored under equilibrium modified atmospheric packaging at 7 degrees C was determined and compared with the shelf-life of unwashed and water-washed carrots. Microbial parameters, including total aerobic plate count, numbers of lactic acid bacteria, Lactobacillae and yeasts, and sensory quality were evaluated. Next to these parameters, atmospheric gas composition, pH and nutrient content were also monitored. The suggested packaging configuration prevented CO2 accumulation, but at the end of the study anoxic conditions were reached for unwashed carrots and carrots washed with 80 mg L-1 PAA. The microbial shelf-life of water-washed carrots was 4 wd based on the yeast count, whereas the flavour was not acceptable after 5 d. The total aerobic plate count and the yeast count determined the shelf-life of carrots treated with 80 mg L-1 PAA on 5 d, whereas the flavour was unacceptable after 7 d. None of the microbial parameters determined the shelf-life of carrots washed with 250 mg L-1 PAA. However. this treatment had already a pronounced adverse effect on the initial sensory quality. Water washing already decreased the content of all individually studied nutrients (-16 to -28%), except for lutein content and the antioxidant capacity. Additional losses after adding PAA on day 0 were found for alpha-tocopherol and phenols. Regardless of the applied treatment, alpha- and beta-carotene remained stable during storage. whereas zeta-carotene, lutein and alpha-tocopherol were unstable. The phenol content and the antioxidant capacity of unwashed, water-washed and 80 mg L-1 PAA-treated carrots increased significantly at the end of the storage period, whereas no changes were found in carrots treated with 250 mg L-1 PAA. On the condition that carrots were packed under an adequate EMA, the 80 mg L-1 PAA treatment showed possibilities for extending shelf-life without pronounced effects on nutrient content. (C) 2009 Elsevier B.V. All rights reserved.