In a small bowl, mix red pepper flakes with oil and let it sit for 4 to 5 hours.
On medium heat, pour oil mixture in a fine sieve over a large deep saucepan and discard the red pepper flakes. When hot, add onions and red peppers; sauté until soft, about 3 minutes. Add ginger and sauté for 1 minute. Add chopped mangoes and cook for 5 minute.
Meanwhile in a medium bowl, combine pineapple juice, vinegar, sugar, curry powder, turmeric, and allspice; whisk well. Pour pineapple mixture in the saucepan and stir; season with salt and pepper. Turn the heat to medium-high and bring mixture to a simmer. Reduce heat to medium and simmer until thickens, about 35 to 45 minutes, stirring often.
Pour hot chutney into prepared jar and process in a water bath for 15 minutes. 7 (250ml/8 oz.) canning jars.