According to US regulations, which of the following is NOT a method for producing gin?

The production of gin is specifically defined by regulations that dictate its methods and ingredients. To be classified as gin, the spirit must have a predominant flavor of juniper berries, and there are established methods for achieving this.

The redistillation of distilled spirits typically involves taking a neutral spirit and infusing it with botanicals, most importantly juniper, to create gin. This method is widely accepted in the industry.

Mixing neutral spirits with juniper berries also aligns with the production of gin, as this method aims to incorporate the required juniper flavor into the spirit.

Similarly, mixing neutral spirits with extracts allows producers to infuse the spirit with various botanical flavors, including juniper, and is another recognized method for making gin.

In contrast, fermenting grains into whiskey is a completely different process. Whiskey production focuses on fermentation and aging in barrels, and it does not relate to the production of gin. Therefore, this method does not fall under the regulatory framework for producing gin, making it the correct answer in this context.