NLP food review classification
The best way to solve your problem would be to collect the right labels for your task. Currently, you have the input i.e. text of a review and the rating which can be used to predict the sentiment of the review, but not whether it mentions safety issues. To collect the right labels, you should look at each review and assign it a binary label - 0 means food safety issues are not mentioned, 1 means they are mentioned. The feasibility of such data collection depends on the size of the dataset and the importance of your project. How big is your dataset? How much time/money are you willing to commit to that project? Once you collect the labels, you can train and evaluate a neural network based on them. If this answer helps you, feel free to ask for elaboration, I don't know what's your level of data science expertise and don't want to state the obvious.