Kim Veramme

Effect of Decontamination Agents on the Microbial Population, Sensorial Quality, and Nutrient Content of Grated Carrots (Daucus carota L.)

Several decontamination agents including water, sodium hypochlorite, peroxyacetic acid, neutral electrolyzed oxidizing water, and chlorine dioxide gas were tested for their effectiveness to reduce the natural microflora on grated carrots. Microbial reductions of the total aerobic count obtained after the different treatments varied between 0.11 and 3.29 log colony-forming units (cfu)/g. Whether or not a decontamination step induced significant changes in the sensory attributes of grated carrots is highly dependent on the type and concentration of disinfectant. To maintain the nutritional value, the influence of the decontamination agents on carotenoid content, alpha-tocopherol content, total phenols, and antioxidant capacity was studied. Besides the part of the nutrients that was leached away from the cutting areas by water, the nutrient losses caused by adding sanitizers were rather limited. Compared with the untreated carrots alpha-tocopherol content was, however, significantly reduced when 250 ppm of peroxyacetic acid (-80%) or 200 ppm of sodium hypochlorite (-59%) was used. Additional losses in carotenoid content were caused by contact with chlorine dioxide gas (-9%). On the condition of an optimized decontamination process toward time and concentration, the microbial quality of fresh-cut carrots could be improved without negatively influencing their sensory quality and nutrient content.

Moderate and High Doses of Sodium Hypochlorite, Neutral Electrolyzed Oxidizing Water, Peroxyacetic Acid, and Gaseous Chlorine Dioxide Did Not Affect the Nutritional and Sensory Qualities of Fresh-Cut Iceberg Lettuce (Lactuca sativa Var. capitata L.) after Washing

Besides the traditionally used sodium hypochlorite (20 and 200 mg L(-1)), alternative sanitizers such as peroxyacetic acid (80 and 250 mg L(-1)) and neutral electrolyzed oxidizing water (4.5 and 30 mg L(-1) free chlorine) as well as chlorine dioxide gas (1.54 mg L(-1)) were evaluated for their efficiency in reducing the microbial load of fresh-cut iceberg lettuce. An additional rinsing step with tap water and cooling of the sanitizing solutions, which are obvious for the fresh-cut industry, were not performed within the current study. The high doses of sodium hypochlorite and peroxyacetic acid tested within this study do not conform to the normally used concentrations within the fresh-cut industry. Neutral electrolyzed oxidizing water (30 mg L(-1)), peroxyacetic acid (250 mg L(-1)), and gaseous chlorine dioxide significantly reduced the total aerobic plate count of cut lettuce in comparison with water wash treatments alone. None of the treatments significantly affected the sensory quality of the lettuce, although small color changes were observed after colorimetric measurements. From a nutritional point of view water rinsing significantly decreased the vitamin C (maximum 35%) and phenol (maximum 17%) contents, but did not affect the carotenoid and α-tocopherol contents. Additional effects caused by adding a sanitizer to the wash water were not observed for vitamin C and phenols. Conversely, washing with 250 mg L(-1) peroxyacetic acid reduced the β-carotene content by about 30%, whereas using 200 mg L(-1) sodium hypochlorite reduced both the lactucaxanthin and the lutein contents by about 60%. Use of gaseous chlorine dioxide also had an impact on the lutein content (-18%). Furthermore, the α-tocopherol content was reduced by 19.7 and 15.4% when the two concentrations of neutral electrolyzed oxidizing water were used, respectively. These data represent the situation on day 0. In a next phase, shelf-life studies considering microbial and sensory quality and nutrient content should be conducted.

THE IMPLEMENTATION OF A DECONTAMINATION STEP DURING THE PROCESSING OF FRESH-CUT PRODUCE: A COMPROMISE BETWEEN INACTIVATION EFFICIENCY AND QUALITY ASPECTS

Peroxyacetic acid is a strong oxidizer and exerts important antimicrobial properties. The effect of a decontamination step with a moderate (80 mg/L) and a high (250 mg/L) peroxyacetic acid concentration on the shelf life of grated carrots stored under equilibrium modified atmosphere at 7°C was determined and compared with the shelf life of unwashed and water washed carrots. Atmospheric composition, microbial parameters, sensory quality and nutrient content (carotenoids, phenols, α-tocopherol, antioxidant capacity) were analysed throughout storage. At the end of the study anoxic conditions were reached for unwashed carrots and carrots washed with 80 mg/L peroxyacetic acid. The microbial shelf life of water washed carrots was 4 days based on the yeast count, where the score for flavour exceeded the limit value after 5 days of storage. The total aerobic plate count and the yeast count determined the shelf life of carrots treated with 80 mg/L peroxyacetic acid on 5 days, whereas the score for flavour exceeded the limit value after 7 days of storage. None of the microbial parameters determined the shelf life of carrots washed with 250 mg/L peroxyacetic acid. However, this treatment had already a pronounced effect on the initial sensory quality. Water washing already decreased the content of all individually studied nutrients, except for the antioxidant capacity. Additional losses after adding peroxyacetic acid on day 0 were found for α-tocopherol and phenols. Regardless of the applied treatment, α- and β-carotene remained stable during storage, but α-tocopherol declined significantly (P<0.05). The phenol content and the antioxidant capacity of unwashed and water washed carrots and carrots washed with 80 mg/L peroxyacetic acid increased significantly (P<0.05) at the end of the storage period, whereas no changes were retrieved in carrots treated with 250 mg/L peroxyacetic acid. On the condition that carrots were packed under an adequate EMA, the 80 mg/L peroxyacetic acid treatment showed perspectives to extend their shelf life without pronounced effects on their nutrient content. Increasing the concentration to 250 mg/L resulted in the best quality from a microbial point of view, but showed an increased impact on both the sensory quality and the nutrient content.