Thermal patterns of heat treated Anisakis L3-infected fishery products allow separation into low, intermediate and high risk groups of potential use in risk management

Abstract

Anisakis third-stage larvae (L3) is moderately tolerant to heat and, to mitigate the risk of live L3 intake in cooked seafood, it is important to define with precision at which point after heat treatment the parasite is no longer infective. We aimed to find thermal patterns that allowed to classify fish sandwiches spiked with Anisakis L3 into “low” (100% probability of mortality), “intermediate” and “high” risk groups. For that, experiments with varying set temperatures and heating times have been performed in conditions of different external heating temperatures. Decision points to classify the samples into terminal nodes associated to different risk groups have been obtained with decision tree analyses and then confirmed with linear discriminant analysis. Separation into two (i.e. low vs high + intermediate risk) or three (i.e. low, intermediate, and high risk) distinct thermal patterns (98% and 95.9% correct classifications by cross-validation respectively) was achieved. These results refine heating conditions reported in the EU Regulation, since reaching 60 °C for 1 min in the thermal centre is not sufficient to kill all L3. However, when factors such as relative temperature of heating or time to reach the set temperature are taken into account, other thermal conditions are found that are equally safe in terms of Anisakis L3 inactivation. This, together with the description of “intermediate” and “high” risk groups can help in the risk identification and management, as well as in providing clearer recommendations to consumers.