That's something SWIM was wondering about. Is the difference between the high purity and food grade quality control and FDA certification? Or is it just the 2% difference? Or is it possibly due to what comprises those impurities?
Edit:
From the site:
Q. What is the difference between food grade and high purity d-Limonene?
A. Once extracted, the "food grade d-Limonene" is purified by fractionation. The resulting product, high purity d-limonene contains a minimum of 98.5% d-limonene. Food grade d-Limonene contains a minimum of 95% d-Limonene.
Just noticed the price difference, so it must be the complexity of the process that's the only difference. SWIM's assuming that food-grade is pure enough for extraction purposes? He's still wondering what the impurities are.