There is a huge difference in the quality of spices. In my sales position sometimes getting the spice business can be a challenge. There are many “jobber” spice companies selling very inexpensive spices. This is true in many supermarkets as well. The up sell can be a challenge but there are real reasons not to skimp on spice quality.
First the thing that make spices bring flavor to your favorite recipes are their essential oils. One presentation I make is putting a table spoon of our spice on a brown paper towel and doing the same with their spice. I then go on to talk about how spices, most of which come from third world countries, are treated and handled.
Cheap spices are far more likely to have things like sticks, pebbles and dirt in them. They are also likely to have been left out in the hot sun or uncovered and unprotected from vermin. Finally cheap spices usually have salt added as an extender.
Now I go back to the spices on the paper towels. I shake off the spice the good spice will leave an oil stain showing it has it’s essential oils the cheap spice will usually not leave any oil stain at all. If this isn’t enough spice companies particularly those in India are adding adulterants that are not salt. Red chili powder is known for having brick powder and saw dust added. Put a tsp of chili powder in water and swirl and you will see a red mist leave the spice this is brick powder. Lead chromate is the leading adulterant in Turmeric.
With all this said how do you avoid these things. Buy premium spices I have sold food for 25 years and been selling Mccormick most of that time. They are completely trustworthy and have the highest quality standards in the industry. I am not selling this as the only choice but is one I know is safe.