Skinner Guy E, Morrissey Travis R, Patazca Eduardo, Loeza Viviana, Halik Lindsay A, Schill Kristin M, Reddy N Rukma
1 U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Food Processing Science and Technology, 6502 South Archer Road, Bedford Park, Illinois 60501.
2 Institute for Food Safety and Health, Illinois Institute of Technology, 6502 South Archer Road, Bedford Park, Illinois 60501, USA.
J Food Prot. 2018 Feb;81(2):261-271. doi: 10.4315/0362-028X.JFP-17-175.
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 10 to 10 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.
高压处理对非蛋白水解型肉毒梭菌孢子失活的影响对于延长冷藏低酸食品的保质期至关重要。在筛选了17株非蛋白水解型肉毒梭菌菌株（8株B型、7株E型和2株F型）后，选择了三株抗性最强的肉毒梭菌菌株（Ham-B、Kap 9-B和610-F）来比较它们的耐热性和压力辅助耐热性。使用双相培养基法制备Ham-B、Kap 9-B和610-F菌株的孢子，将其在N-（2-乙酰氨基）-2-氨基乙烷磺酸（ACES）缓冲液（0.05 M，pH 7.00）中稀释至10⁶至10⁸CFU/mL，放入改良的无菌转移移液器中，热封，然后使用实验室和中试规模的压力测试系统，使其承受600至750 MPa的高压和80至91°C的高温组合处理。将来自同一批次的稀释孢子放入核磁共振管中，热封后，在以Duratheram S油作为传热流体的福禄克7321高精度浴中加热至80至91°C。培养3个月后，两项研究中的存活菌数均通过使用胰蛋白酶-蛋白胨-葡萄糖-酵母提取物肉汤的五管最大可能数法来确定。Ham-B、Kap 9-B和610-F菌株的孢子计数在测试的最高温度和压力组合（91°C和750 MPa）下出现了最高（>5.0）对数减少。随着处理温度从80°C升高到87°C，Ham-B、Kap 9-B和610-F的热D值降低，在87°C时这些菌株的热D值降至<1.0分钟。Ham-B、Kap 9-B和610-F的压力辅助热D值随着处理温度从80°C升高到91°C而降低，且在91°C时随着压力从600 MPa增加到750 MPa，其压力辅助热D值也降至<1.0分钟。基于压力辅助热D值，与仅进行热处理相比，在83至91°C结合600至700 MPa压力处理时，压力对Ham-B、Kap 9-B和610-F菌株的孢子具有更强的保护作用。当Ham-B、Kap9-B和610-F的孢子在较低温度（80至83°C）结合750 MPa处理时，未观察到保护作用。然而，在较高温度（87至9°1C）结合750 MPa处理时，根据计算出的压力辅助热D值，Ham-B、Kap9-B和610-F的孢子表现出保护作用。
