Insight into the Impact of Food Processing and Culinary Preparations on the Stability and Content of Plant Alkaloids Considered as Natural Food Contaminants

Pyrrolizidine alkaloids, tropane alkaloids and opium alkaloids are natural plant toxins that have recently gained special interest in food safety due to their concerning occurrence in many foods and feeds. Although a legislation for these alkaloids has recently been established, the concentration levels of these toxins in food exceed in many cases the maximum limit established by the competent authorities. Moreover, these regulations only establish maximum limits of these compounds for certain raw materials, but processed products are generally not considered. However, it is important to correctly assess the potential health risk of these alkaloids through the diet. Accordingly, this review aims to provide insight into these alkaloids and give an overview on how food processing and culinary preparation can influence their content and stability. For this purpose, the most relevant works that address the effect of heat treatment, fermentation, infusion preparation (transfer rate) and other treatments (milling, washing and soaking) on these natural toxins are reviewed. To date, this research field has been scarcely studied and many of the results published are contradictory, so it is not always possible to establish conclusive findings. In many cases, this is due to a lack of experimental design and exhaustive control of the different variables that may affect these treatments and preparations. Likewise, considering the transformation of these alkaloids into toxic degradation products it is also of high interest. Therefore, further studies are needed to delve deeper into the stability of these toxins and to understand how their content may be affected by the transformation of contaminated raw materials into processed products, so that the risk exposure of the population to these alkaloids through diet can be determined more precisely. Hence, this topic constitutes a research line of great interest for future works with many challenges to be resolved.