Information Regarding Crystallization of Stabilized Vitamin C in Glycol

Thank you for your inquiry regarding the crystallization observed in your Stabilized Vitamin C in Glycol product. Based on your description and the information provided by our staff, this phenomenon is a known characteristic of highly concentrated L-Ascorbic Acid solutions, particularly when subjected to temperature fluctuations.

Here are the answers to your questions:

1. Can it actually be stored at room temperature?
   While the product may tolerate room temperature under stable conditions, the crystallization you observed indicates that temperature variations can cause the L-Ascorbic Acid to precipitate out of the glycol solution. For long-term stability and to minimize crystallization, storing L-Ascorbic Acid products in a cool environment, such as a refrigerator (around 6-8°C), is generally recommended.

2. Warming at 60°C didn't work; are there other methods?
   Warming the product gently (e.g., in a 60°C water bath for a short period) is a suggested method to help redissolve the crystals, as mentioned in the product information for L-Ascorbic Acid (Fine). However, as you experienced, it may not always fully dissolve all crystals, especially if the crystallization is significant or has occurred over a long period. Applying higher temperatures or heating for extended durations is not recommended as it can degrade the Vitamin C, reducing its efficacy. If warming does not completely redissolve the crystals, the recommended approach is to filter out the remaining solid particles, as suggested by the staff, to ensure a clear and usable product.

3. If registered with the FDA and sold, will it crystallize before reaching the customer? How to manage this?
   Crystallization during transport and storage before reaching the customer is a possibility, especially in regions with fluctuating temperatures. This can affect the product's appearance and potentially raise concerns about quality consistency for both FDA registration and customer satisfaction. While the staff indicated that the amount of precipitated Vitamin C is typically small (not exceeding 2.5%), the presence of visible crystals can be perceived negatively. Managing this requires strict temperature control throughout the supply chain, which can be challenging in practice.

For formulations intended for wide distribution where temperature control is difficult, considering more stable derivatives of Vitamin C, such as Ascorbyl Glucoside or Ethyl Ascorbic Acid, might be a more suitable option to avoid the crystallization issue entirely. These derivatives offer better stability in various conditions, although their properties and efficacy profiles may differ slightly from L-Ascorbic Acid.