Relationship Between Water Activity of Fresh Pasta and Toxin Production by Proteolytic Clostridium botulinum

Four types of fresh pasta (meat- or cheese-filled tortellini and flat noodle linguine or fettucine) were prepared with different water activities, inoculated with proteolytic Clostridium botulinum spores, packaged under a modified atmosphere, and stored at either 4 or 30°C for 8 to 10 weeks. Products were assayed for botulinal toxin at appropriate sampling times. No toxin was detected in any fresh pasta held at 4°C for up to 8 weeks. However, toxin was detected in meat tortellini with a_w of 0.99 and 0.95 at 2 and 6 weeks, respectively, when held at 30°C. Toxin was not detected in tortellini with an a_w of 0.94 or below held at 30°C for 10 weeks. Toxin was produced at 2 weeks in linguine at a_w 0.96 and held at 30°C, whereas no linguine or fettucine at a_w 0.93 or 0.95 and held at 30°C was toxic during 10 or 8 weeks, respectively. The a_w of fresh pasta is a principal factor in preventing botulinal toxin production by proteolytic C. botulinum in temperature-abused products. A survey of commercially available fresh pasta revealed that most flat noodles were below the a_w limit for botulinal toxin production, whereas most of the filled pasta had a_w values which permitted toxin production if temperature abuse occurred.