By Marcelo Teixeira NEW YORK (Reuters) – Food and beverage giant Nestle on Tuesday said it has started operations at its new coffee processing plant in Mexico, its largest instant coffee site in the world, where it invested $340 million to process 670,000 bags per year. The Veracruz-based plant will make instant coffee for Nestle’s Nescafe brand, with the United States as the potential destination of most of its production. According to coffee traders, the investment in such a large instant coffee plant in a location that is far from Vietnam, the world’s largest producer of robusta coffee – th…