Isabelle Vandekinderen

Efficacy of sodium hypochlorite and peroxyacetic acid to reduce murine norovirus 1, B40-8, Listeria monocytogenes, and Escherichia coli O157:H7 on shredded iceberg lettuce and in residual wash water.

The efficiency of sodium hypochlorite (NaOCl) and peroxyacetic acid (PAA) to reduce murine norovirus 1 (MNV-1), a surrogate for human norovirus, and Bacteroides fragilis HSP40-infecting phage B40-8 on shredded iceberg lettuce was investigated. The levels of removal of viruses MNV-1 and B40-8 were compared with the reductions observed for bacterial pathogens Listeria monocytogenes and Escherichia coli O157:H7. Two inoculation levels, one with a high organic load and the other containing a 10-fold lower number of pathogens and organic matter, showed that the effectiveness of NaOCl was greatly influenced by the presence of organic material, which was not observed for PAA. Moreover, the present study showed that 200 mg/liter NaOCl or 250 mg/liter PAA is needed to obtain an additional reduction of 1 log (compared with tap water) of MNV-1 on shredded iceberg lettuce, whereas only 250 mg/liter PAA achieved this for bacterial pathogens. None of the treatments resulted in a supplementary 1-log PFU/g reduction of B40-8 compared with tap water. B40-8 could therefore be useful as an indicator of decontamination processes of shredded iceberg lettuce based on NaOCl or PAA. Neither MNV-1, B40-8, nor bacterial pathogens could be detected in residual wash water after shredded iceberg lettuce was treated with NaOCl and PAA, whereas considerable numbers of all these microorganisms were found in residual wash water consisting solely of tap water. This study illustrates the usefulness of PAA and NaOCl in preventing cross-contamination during the washing process rather than in causing a reduction of the number of pathogens present on lettuce.

Optimization and evaluation of a decontamination step with peroxyacetic acid for fresh-cut produce.

Since several disadvantages are associated with the use of sodium hypochlorite as a decontamination agent, the attention for alternative agents such as peroxyacetic acid (PAA) is increasing. In this study the effectiveness of PAA to remove the native microflora was tested in four types of fresh-cut vegetables: grated carrots, fresh-cut white cabbage, iceberg lettuce and leek. Furthermore, the influence of varying PAA concentrations (0, 25, 80, 150 and 250 ppm) and varying contact times (1, 5 and 10 min) was described by means of a linear model. The efficiency of PAA to remove the native flora was highly dependent on the type of fresh-cut produce: the highest microbial reductions were obtained for carrots (0.5-3.5 log cfu/g) and white cabbage (0.5-3.5 log cfu/g) followed by iceberg lettuce (0.4-2.4 log cfu/g). The obtained efficiency was the lowest for fresh-cut leek (0.4-1.4 log cfu/g). Furthermore, all the treated samples, regardless of the type of vegetable and the contact time and concentration of the PAA treatment, were acceptable for consumption.

Effects of food composition on the inactivation of foodborne microorganisms by chlorine dioxide.

Chlorine dioxide (ClO2) is a strong oxidizing agent that can be applied in solution as well as in the gaseous state. It has bactericidal, fungicidal and viricidal properties. Several food-related microorganisms, including Gram-negative and Gram-positive bacteria, yeasts, mould spores and Bacillus cereus spores were tested for their susceptibility to 0.08 mg/L gaseous ClO2 during 1 min at a relative humidity of 90%. In this screening, the resistance of the different groups of microorganisms towards gaseous ClO2 generally increased in the order Gram-negative bacteria, Gram-positive bacteria, yeasts and mould spores and Bacillus cereus spores. With this treatment, reductions of microbial numbers between 0.1 and 3.5 log cfu/cm2 could be achieved. The effects of the food components starch, fat, protein and NaCl on the antimicrobial activity of gaseous ClO2 were also evaluated. Soluble starch, corn oil, butter, whey protein isolate and NaCl were added in incremental concentrations to portions of an agar medium. Then, plates of the supplemented agars were inoculated with Leuconostoc mesenteroïdes at numbers of 4 log cfu/cm2 and subsequently treated with ClO2. Both soluble starch and NaCl did not have an effect on the antimicrobial efficiency of ClO2. However, butter, corn oil or whey protein in the agar almost eliminated the antimicrobial effect of ClO2. In corn oil-water emulsions treated with gaseous ClO2 the peroxide value increased significantly, indicating the formation of primary oxidation products. Similarly, a treatment with ClO2 increased the protein carbonyl content and induced the transformation of SH-groups to -S-S-groups in whey protein. The findings suggest that gaseous ClO2 will be a highly effective decontaminating agent for carbohydrate-rich foods, but that it would be less effective for the decontamination of high-protein and fatty foods.

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.

Consuming organic versus conventional vegetables: The effect on nutrient and contaminant intakes

The health benefits of consuming organic compared to conventional foods are unclear. This study aimed at evaluating the nutrient and contaminant intake of adults through consumption of organic versus conventional vegetables, namely carrots, tomatoes, lettuce, spinach and potatoes. A probabilistic simulation approach was used for the intake assessment in two adult populations: (1) a representative sample of Belgians (n=3245) and (2) a sample of Flemish organic and conventional consumers (n=522). Although significant differences in nutrient and contaminant contents were previously found between organic and conventional vegetables, they were inconsistent for a component and/or vegetable. These findings were translated here into inconsistent intake assessments. This means that the intake of specific nutrients and contaminants can be higher or lower for organic versus conventional vegetables. However, when considering the consumption pattern of organic consumers, an increase in intake of a selected set of nutrients and contaminants is observed, which are explained by the general higher vegetable consumption of this consumer group. In public health terms, there is insufficient evidence to recommend organic over conventional vegetables. The general higher vegetable consumption of organic compared to conventional consumers outweighs usually the role of differences in nutrient and contaminant concentrations between organic and conventional vegetables.

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 sensory acceptability of cooked meat products treated with a protective culture depends on glucose content and buffering capacity: A case study with Lactobacillus sakei 10A.

Biopreservation has been proven to be a promising natural preservation technique, but the impact of protective cultures on the sensory properties of cooked meat products (CMP) is not well documented. This work presents a case study on the protective culture Lactobacillus sakei 10A to obtain a clear view on the real consequences of using protective cultures on the sensory quality of CMP. A preliminary screening study on 13 different CMP and more elaborate application trials at 7°C on vacuum packaged pâté, cooked ham, cooked sausage and two cooked poultry products demonstrated that L. sakei 10A inhibits the endogenous LAB-flora, Leuconostoc mesenteroides, Brochothrix thermosphacta and Listeria monocytogenes. Despite these promising antagonistic effects, the application of L. sakei 10A to CMP was in some cases limited by a significant acidification resulting in an acid taste of the product. This was most obvious in pâté and cooked sausage and less obvious in cooked turkey fillet. From the results a hypothesis could be derived that high buffering capacity and low glucose content are key elements to avoid sensory deviations when applying protective cultures on CMP.

Microbiological and Safety Aspects of Fresh-Cut Fruits and Vegetables

Despite a worldwide increase in demand for fresh-cut fruit and vegetables, in many countries these products are prepared in uncontrolled conditions and have the potential to pose substantial risk for consumers. Correspondingly, researchers have ramped up efforts to provide adequate technologies and practices to assure product safety while keeping nutritional and sensory properties intact. With contributions from experts from industry, research centers, and academia, Advances in Fresh-Cut Fruits and Vegetables Processing collates and presents new scientific data in a comprehensive update on technologies and marketing considerations. Taking a multidisciplinary approach, this work discusses the basics and recent innovations in fresh-cut fruit and vegetable processing. It addresses scientific progress in the fresh-cut area and discusses the industry and the market for these commodities. The book covers the regulations that affect the quality of the final products and their processing as well as consumers’ attitude and sensory perceptions. The chapters cover the design of plants and equipment, taking into account engineering aspects, safety, and HACCP guidelines. They also examine innovations in creating healthy and attractive products. Use of innovative packaging technology that could improve product quality and shelf life, new fruit mixtures with more variety, incorporation of flavors, or the use of steamer bags for vegetables are just a few considerations that could expand the markets of fresh-cut products. With its focus on science, including biochemical, physiological, microbiological, and quality aspects, as well as heath considerations and consumer science, this book reports on cutting-edge advances and the practical applications of these advances.

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.