Quenten Denon

Heat resistance of Bacillus cereus emetic toxin, cereulide

Aims:  The study describes the effects of heating temperature and exposure time on the thermal stability of cereulide under different conditions (pH, presence/absence of oil phase and cereulide concentration).

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.

Effect of Initial Headspace O2 Level on the Growth and Volatile Metabolite Production of Leuconostoc Mesenteriodes and the Microbial and Sensorial Quality of Modified Atmosphere Packaged Par-Fried French Fries.

This study evaluated the effect of residual O2 level (0% to 5%) on microbial growth and volatile metabolite production on par-fried French fries packaged in a modified atmosphere with 60% CO2 (rest N2 ) at 4 °C. The results obtained showed that the initial headspace (IH) O2 level had an effect on growth of Leuconostoc mesenteroides on French fry simulation agar, whereby growth was slightly faster under 5% O2 . In terms of quantity, ethanol, 2-methyl-1-propanol, and dimethyl disulphide were the most significant volatile metabolites produced by L. mesenteroides. The production of ethanol by L. mesenteroides was highest on simulation agar packaged under low IH O2 levels (0% to 1%), indicating that the fermentative metabolism was induced under these conditions. In agreement with the results observed on the simulation medium, growth of native lactic acid bacteria was faster under an IH O2 level of 5%. In addition, ethanol, 2-methyl-1-propanol, and dimethyl disulphide were also quantitatively the most important volatile metabolites. However, in contrast, greater quantities of ethanol and dimethyl disulphide were produced on par-fried French fries packaged under 5% O2 . This was attributed to the limited growth of the native flora on the par-fried French fries under residual O2 levels of 0% and 1%. Although some significant differences (P < 0.05) occurred between the French fries packaged in 0%, 1%, and 5 % residual O2 during storage, all products were considered to be acceptable for consumption. The results of this study can be used to optimize the shelf-life of packaged chill stored potato products.

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.