I'm not at all surprised you can't find food fraud records for food additives.
I created the Food Fraud Risk Information Database hosted on Trello and we don't have a single food fraud incident for any food additive (excluding vanilla extract) in the database. Here's why:
1) A fraud that involves adulteration or substitution would be noticed by the food company quite quickly for most additives. For example, if a fraudster sold you whey powder instead of emulsifier you would realise as soon as you tried to use it. If a fraudster sold you talcum powder instead of preservative, you would find a residue in your product.
2) Because of (1), misrepresentation-type food fraud (eg. "organic" sodium bicarbonate that isn't actually "organic") is more likely to occur than adulteration or substitution fraud for food additives. But those types of fraud are less likely to be noticed at borders or customs checks, and don't cause a food safety risk, so they won't be added to RASFF.
3) Many food additives (excluding flavours) have short(ish) supply chains compared to other food types, which reduces the chances for fraudulent tampering with the product and might make them less susceptible to food fraud than other foods.
4) A food fraud problem in a food additive probably won't result in a food safety problem or a recall, because of the tiny concentrations at which additives are present in finished products. If there is no food safety problem and no recall, then the fraud won't become public knowledge. And therefore won't get into RASFF.
5) Border checks and import alerts make up many (most?) of the RASFF records. It's my understanding that most countries prioritise border inspections for foods that present high risks with respect to food safety. They probably aren't prioritising checks on food additives, because they aren't high risk. And actually most food additives might not even be considered "food" at the point they are crossing borders... many would probably be identified as "food grade chemicals" during transport.
These are the reasons you won't find many records of food fraud in food additives in the RASFF portal.
Miguel, you could try contacting the Food Industry Intelligence Network, which receives confidential information from food businesses about frauds they have discovered. These frauds never get released onto the public record. They might know of some food additive frauds.
Best of luck with your studies