Effect of High Pressures in Combination with Temperature on the Inactivation of Spores of Nonproteolytic Clostridium botulinum Types B and F

ABSTRACT The impact of high pressure processing on the inactivation of spores of nonproteolytic Clostridium botulinum is important in extended shelf life chilled low-acid foods. The three most resistant C. botulinum strains (Ham-B, Kap 9-B, and 610-F) were selected for comparison of their thermal and pressure-assisted thermal resistance after screening 17 nonproteolytic C. botulinum strains (8 type B, 7 type E, and 2 type F). Spores of strains Ham-B, Kap 9-B, and 610-F were prepared using a biphasic media method, diluted in N-(2-acetamido)-2-aminoethanesulfonic acid (ACES) buffer (0.05 M, pH 7.00) to 105 to 106 CFU/mL, placed into a modified sterile transfer pipette, heat sealed, and subjected to a combination of high pressures (600 to 750 MPa) and high temperatures (80 to 91°C) using laboratory and pilot-scale pressure test systems. Diluted spores from the same crops were placed in nuclear magnetic resonance tubes, which were heat sealed, and subjected to 80 to 91°C in a Fluke 7321 high precision bath with Duratheram S oil as the heat transfer fluid. After incubation for 3 months, survivors in both studies were determined by the five-tube most-probable-number method using Trypticase–peptone–glucose–yeast extract broth. The highest (>5.0) log reductions in spore counts for Ham-B, Kap 9-B, and 610-F occurred at the highest temperature and pressure combination tested (91°C and 750 MPa). Thermal D-values of Ham-B, Kap 9-B, and 610-F decreased as the process temperature increased from 80 to 87°C, decreasing to <1.0 min at 87°C for these strains. Pressure-assisted thermal D-values of Ham-B, Kap 9-B, and 610-F decreased as the process temperature increased from 80 to 91°C with any pressure combination and decreased to <1.0 min as the pressure increased from 600 to 750 MPa at 91°C. Based on the pressure-assisted thermal D-values, pressure exerted a more protective effect on spores of Ham-B, Kap 9-B, and 610-F when processed at 83 to 91°C combined with pressures of 600 to 700 MPa when compared with thermal treatment only. No protective effect was observed when the spores of Ham-B, Kap9-B, and 610-F were treated at lower temperatures (80 to 83°C) in combination with 750 MPa. However, at higher temperatures (87 to 91°C) in combination with 750 MPa, a protective effect was seen for Ham-B, Kap9-B, and 610-F spores based on the calculated pressure-assisted thermal D-values.

Environmental Contamination from Industrial Bitter Cassava: Implications for Moisture-Pressure Combination Treatments

<p>Commercial processing of cassava produces vast quantities of cyanide-laced waste which can adversely infiltrate water supplies and air breathed by factory workers. This study aimed to determine the comparative concentration of cyanogens in the cassava peel as opposed to that of the pith and the effect of the moisture-pressure combination treatments on cyanide concentration. A semi-quantitiative test using the picrate-spectrophotometer method was applied, where, at room temperature in a closed vial, reactions caused liberation of HCN which reacts with a picrate paper. The results showed a 25% higher level of cyanogen concentration in casssava peels compared to that of blended peels and pith. Treatments released cyanide from samples in the order: 2 h wetting at 50 °C + pressing &gt; 4 h wetting at 25 °C + pressing = 2 h wetting at 40 °C + pressing &gt; 2 h wet at 25 °C + pressing = 4h wet at 25 °C &gt; 12 h pressing. In this manner, wetting for 2 h at 50 °C followed by pressure for 12 h released cyanide by at least 20% more than that of any other treatment. The combination of moisture and pressure enhanced the contact time between linamarin and linamarase to increase the release of HCN. Physiological cyanide overload in organisms from cassava processing occurs in water, land, and air. Therefore the reduction in concentration observed in this study, if applied at an early stage of the cassava processing, should reduce the rate of morbidity in environments at risk.</p>